ONSITE PD TESTING OF CAST-RESIN TRANSFORMERS IN WIND FARMS
PROTECTING WIND TURBINES THROUGH EFFECTIVE GROUNDING PAGE 60
APPLYING NFPA 70E AND CSA Z462 TO RENEWABLE ENERGY POWER GENERATION PAGE 72
JIM WHITE REMEMBRANCE PAGE 83
Megger Solar Testing Kit
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n MIT2500 Insulation Resistance Tester
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n PV Test Lead
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The MIT2500 is the only handheld insulation resistance tester with test voltages up to 2,500V, so you can easily test both the ac and dc sides of inverters and quickly identify conductor insulation issues.
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COVER
Onsite PD Testing of Cast-Resin Transformers in Wind Farms
Wind power generation has established itself as a major renewable technology used by utilities around the world. But like anything new, the fast-paced implementation of windpower installations has brought its share of challenges. The failure rate of mediumvoltage transformers installed in wind farms is well above what the industry has been used to with traditional energy-generation sources. The lack of onsite testing capability, among other factors, has contributed to those failures. While challenges are great, so are opportunities. This article shares a modern method to test the insulation of mediumvoltage transformers installed in challenging environments such as remote locations, constricted space conditions, and areas with high electromagnetic interferences.
Mathieu Lachance, OMICRON electronics Canada, and Dr. Alexander Kraetge, OMICRON electronics Germany
FEATURES
60 Protecting Wind Turbines through Effective Grounding
Sameer Kulkarni and Dr. Ahmed El-Rasheed, Megger
72 Applying NFPA 70E and CSA Z462 to Renewable Energy Power Generation
Terry Becker, P.Eng., CESCP, TW Becker Electrical Safety Consulting Inc.
10 Virginia Balitski, Magna IV Engineering
7 President’s Desk
Always Remember: Your Work Is Essential
Eric Beckman, National Field Services
NETA President
17 NFPA 70E and NETA
Proposed Changes to the NFPA 70E Standard, 2002 Edition
In Memory of James R. White, Shermco Industries
21 Relay Column
Programming Numerical Relays to Alarm
Steve Turner, Arizona Public Service Company
26 In the Field
The Trouble with Ground Fault Testing
Mose Ramieh, CBS Field Services
32 Safety Corner
Distracted Driving
Paul Chamberlain, American Electrical Testing Co., LLC
136 Outgoing NETA President Scott Blizard: Up to the Challenge
IMPORTANT LISTS
139 NETA Accredited Companies
146 Advertiser List
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neta@netaworld.org
www.netaworld.org
executive DiRectOR: Missy Richard
NETA Officers
pResiDent: Eric Beckman, National Field Services
fiRst vice pResiDent: Ken Bassett, Potomac Testing
secOnD vice pResiDent: Bob Sheppard, Premier Power Maintenance
secRetaRy: Dan Hook, Western Electrical Services, Inc.
tReasuReR: John White, Sigma Six Solutions, Inc.
NETA Board of Directors
Virginia Balitski (Magna IV Engineering)
Ken Bassett (Potomac Testing, Inc.)
Eric Beckman (National Field Services)
Scott Blizard (American Electrical Testing Co., Inc.)
Jim Cialdea (CE Power Engineered Services, LLC)
Scott Dude (Dude Electrical Testing LLC)
Dan Hook (Western Electrical Services, Inc.)
David Huffman (Power Systems Testing)
Chasen Tedder, Hampton Tedder Technical Services
Ron Widup (Shermco Industries)
nOn-vOting bOaRD membeR
Lorne Gara (Shermco Industries)
Alan Peterson (Utility Service Corporation)
John White (Sigma Six Solutions)
NETA World Staff
technicaL eDitORs: Roderic L. Hageman, Tim Cotter
assistant technicaL eDitORs: Jim Cialdea, Dan Hook, Dave Huffman, Bob Sheppard
assOciate eDitOR: Resa Pickel
managing eDitOR: Carla Kalogeridis
cOpy eDitOR: Beverly Sturtevant
aDveRtising manageR: Laura McDonald
Design anD pRODuctiOn: Moon Design
NETA Committee Chairs
cOnfeRence: Ron Widup; membeRship: Ken Bassett; pROmOtiOns/maRketing: Scott Blizard; safety: Scott Blizard and Jim White; technicaL: Alan Peterson; technicaL exam: Dan Hook; cOntinuing technicaL DeveLOpment: David Huffman; tRaining: Eric Beckman; finance: John White; nOminatiOns: Dave Huffman; aLLiance pROgRam: Jim Cialdea; assOciatiOn DeveLOpment: Ken Bassett and John White
NETA World is published quarterly by the InterNational Electrical Testing Association. Opinions, views and conclusions expressed in articles herein are those of the authors and not necessarily those of NETA. Publication herein does not constitute or imply endorsement of any opinion, product, or service by NETA, its directors, officers, members, employees or agents (herein “NETA”).
All technical data in this publication reflects the experience of individuals using specific tools, products, equipment and components under specific conditions and circumstances which may or may not be fully reported and over which NETA has neither exercised nor reserved control. Such data has not been independently tested or otherwise verified by NETA.
NETA MAKES NO ENDORSEMENT, REPRESENTATION OR WARRANTY AS TO ANY OPINION, PRODUCT OR SERVICE REFERENCED OR ADVERTISED IN THIS PUBLICATION. NETA EXPRESSLY DISCLAIMS ANY AND ALL LIABILITY TO ANY CONSUMER, PURCHASER OR ANY OTHER PERSON USING ANY PRODUCT OR SERVICE REFERENCED OR ADVERTISED HEREIN FOR ANY INJURIES OR DAMAGES OF ANY KIND WHATSOEVER, INCLUDING, BUT NOT LIMITED TO ANY CONSEQUENTIAL, PUNITIVE, SPECIAL, INCIDENTAL, DIRECT OR INDIRECT DAMAGES. NETA FURTHER DISCLAIMS ANY AND ALL WARRANTIES, EXPRESS OF IMPLIED, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE.
ELECTRICAL TESTING SHALL BE PERFORMED ONLY BY TRAINED ELECTRICAL PERSONNEL AND SHALL BE SUPERVISED BY NETA CERTIFIED TECHNICIANS/ LEVEL III OR IV OR BY NICET CERTIFIED TECHNICIANS IN ELECTRICAL TESTING TECHNOLOGY/LEVEL III OR IV. FAILURE TO ADHERE TO ADEQUATE TRAINING, SAFETY REQUIREMENTS, AND APPLICABLE PROCEDURES MAY RESULT IN LOSS OF PRODUCTION, CATASTROPHIC EQUIPMENT FAILURE, SERIOUS INJURY OR DEATH.
ALWAYS REMEMBER: YOUR WORK IS ESSENTIAL
I want to start by thanking all NETA members and Board members for their support and trust to help lead the organization as I step into my term as President. It truly is an honor to be part of such a first-class organization that’s so well-respected all across the world and to be able to represent and lead it is even more important.
In this NETA World, we take a renewable energy tack and look into the hazards and regulations associated with this type of power generation from construction to maintenance. We also take a look at the importance of effective grounding in the protection of wind turbines. You’ll certainly want to read the cover story, “Onsite PD Testing of Cast-Resin Transformers in Wind Farms.”
As the world begins to open, I want to take a moment to recognize electrical workers and their families across the world. As we all have learned, the electrical infrastructure is quite possibly the most essential part of our life these days. We tend to forget that we can’t accomplish many of the things we’ve become accustomed to doing without it.
Although very fortunate to have the opportunity to continue to work and provide for their families, these technicians, electricians, and engineers put themselves in potential harm’s way. Adhering to various state, agency, and government regulations while maintaining safe work practices has and continues to be a huge challenge for everyone. I want to commend the perseverance and dedication to all of those involved. It is truly a testament to how hard-working the people in this critical industry really are.
Remember to mark your calendar for February 28–March 4 for PowerTest 2022 at the Hyatt Regency in Denver, Colorado. This will be our first in-person event — but with a virtual element.
Plan ahead and always put safety first!
Eric Beckman, PE, President International Electrical Testing Association
Superior Service for Optimal Performance
VIRGINIA BALITSKI: SAFETY FIRST — SUCCESSION PLANNING NEXT
With over 15 years’ experience at Magna IV Engineering in Edmonton, AB, Canada, this technician-turned-trainer explains why preserving our legacy knowledge is the best way to keep people safe.
NW: What attracted you to the electrical testing profession?
Balitski: In high school, I excelled in math and physics, so one of my instructors encouraged me to explore engineering. My father was an electronics technician, and I was often in the shop with him when he was fixing things. I’ve always enjoyed working with my hands.
I graduated from the NAIT Electrical Engineering Technology program in 2006. I have always had an interest in the electrical discipline, so I thought the field might be a great place to start my career. I worked full time in the field as a technician for approximately 6
Virginia Balitski is Manager — Training and Development for Magna IV Engineering, a NETA Level 4 Certified Technician, and a member of the NETA Board of Directors.
years, then moved to a role that was 50% in the field and 50% in the office for a few more years. Now, I am mostly in the office or onsite delivering technical or safety training — although I do dust off the coveralls every now and again and head back out to the field.
NW: What about this work keeps you committed to the profession?
Balitski: Once I started working on projects, I knew I loved the work. I especially enjoy the experiences and the knowledge that come with the job. I started getting involved in a few of the electrical industry groups and started participating more on committees and boards through my
employer as well. Now I am part of several groups that contribute to the electrical industry.
NW: What about this work is specifically challenging for you, and how are you overcoming that challenge?
Balitski: Staying on top of all the technological advancements and staying up to date is always challenging. I have to keep up with new technologies, safety regulations, and new legislation. I stay involved with the emerging technologies by reading technical papers, articles, attending seminars, and conferences. NETA World is a great resource for some of that information. Fortunately,
Canada and the United States are technically harmonized in a majority of their regulations and standards.
NW: If you were talking to a young person interested in knowing more about being a technician or having a career in electrical testing, what advice would you give?
Balitski: I would make sure they understood that the job is ever-changing and fast-moving. To be successful in the electrical power testing industry, you need to be flexible and quickthinking, ready to work hard, and be willing to devote your time. You pay your dues by working long hours in the field, and there’s lots
INSIGHTS & INSPIRATION
of travel. You must stay on the job until the problem is solved, so it’s important to develop your troubleshooting skills. You must do whatever needs to be done to keep the client happy. The reward is a successful career in a field that we all enjoy.
NW: Describe one of your best workdays… What happened?
Balitski: I am not sure I could pick a particular day, but it is always rewarding to leave a site with a successful energization and a happy client. I’ve had loads of good days. It’s always a good day when no one gets hurt.
NW: What’s it like when a day doesn’t go as planned? How did you respond to those situations?
Balitski: Most days during a maintenance shutdown rarely go exactly as planned, which is why I emphasize the need for quick thinking and flexibility. It is very important to be able to troubleshoot issues as they come up and to be flexible with the demands, schedule, and plan.
NW: How important is ongoing training and professional development in this field?
Balitski: Training and development is where I am currently involved in my career, so I certainly believe it is essential for workers to be properly trained and competent to perform the tasks they are asked to handle. It is an ongoing challenge for any organization to stay up to date with all the new technologies and standards. Since I am involved in developing and delivering training, it is essential that I understand the latest standards and requirements in the industry. Being involved with all aspects of the industry —such as standards, technical information, and safety — helps to keep me updated on all new topics.
You have to take responsibility for your professional development by joining and participating in industry organizations and keeping up with your continuing education credits and standards.
NW: Speaking of training, I saw a photo of you providing training to an all-male audience. What advice do you have for women who are interested in advancing in the electrical power testing profession?
Balitski: I don’t want to be thought of as a female technician or a woman doing her best in a predominantly male industry. I don’t expect any favors or special attention. I want to be thought of in the same way as any other team member.
My advice to women is to be comfortable in your technical competence. Work hard and do your job. It’s the same for both men and women who want to advance in their career. In the electrical testing profession, we are all doing the same tasks. There is nothing in the field that a woman cannot do. There are generally fewer women in the field, but this is a great career for women, with plenty of opportunity to excel.
NW: What are some of the energy trends you believe will affect your work in the future (e.g. EVs, wind, solar, etc.)? How are you preparing for future changes that may be coming your way?
Balitski: Renewable energy and electric vehicles are trends that will continue to evolve in the electrical industry and become much more prominent. Dealing with the unique stresses and operational challenges of an aging electrical infrastructure will highlight the importance of ensuring the reliability of electrical systems. We have to make sure the electrical systems can handle it. Some of our clients are shifting to renewable energy, particularly wind and solar. Therefore, it is critical to stay on top of all the new standards.
NW: As an industry, what do you think should be the No. 1 priority over the next year?
Balitski: The industry focus should always be on improving safety. Safety is always essential and should be given top priority. Complying with the latest electrical safety standards and
best practices throughout the industry needs to be top of mind for all organizations. There are lots of tools and resources out there to help with this and keep all workers safe so they can go home and keep doing what they love to do. In my spare time, you will find me out exploring mountains, running races, and spending time with my loved ones. Everyone should be able to return safely to their loved ones at the end of each day.
After safety, the industry needs to look at recruitment and succession planning. We must make sure we are not losing our collective industry knowledge. We need mentorship for passing along that information to the next generation. When I started out in the field, I
was working with a smaller group of people and had easy access to the most experienced people. But as a company grows larger, you need a plan on how to pass on that knowledge to the newer people on the team. It’s critical that our industry keeps its legacy knowledge intact.
WANT TO TELL YOUR STORY?
NETA World is looking for technicians, emerging leaders, and industry thought leaders to be featured in our new Insight & Inspiration department. If you know someone who would make a great interview — or if you would like to be interviewed yourself — please contact Carla Kalogeridis at ckalogeridis@netaworld.org
VIRGINIA BALITSKI:
Balitski says safety is about making sure technicians return to who and what they love at the end of the day.
THE PREMIER ELECTRICAL MAINTENANCE AND SAFETY CONFERENCE
FEBRUARY 28 – MARCH 4, 2022
HYATT REGENCY DENVER, COLORADO
Exhibit to an audience of 500+ electrical testing professionals including leading decision-makers looking for new products and services.
For attendee profile and additional information, visit powertest.org
The
the industry, that never compromises
As North America’s largest independent electrical testing company, our most important Company core value should come as no surprise: assuring the safety of our people and our customer’s people. First and foremost.
Our service technicians are NETA-certified and trained to comply and understand electrical safety standards and regulations such as OSHA, NFPA 70E, CSA Z462, and other international guidelines. Our entire staff including technicians, engineers, administrators and management is involved and responsible for the safety of our co-workers, our customers, our contractors as well as our friends and families.
Our expertise goes well beyond that of most service companies. From new construction to maintenance services, acceptance testing and commissioning to power studies and rotating machinery service and repair, if it’s in the electrical power system, up and down the line, Shermco does it.
Proposed Changes to the NFPA 70E Standard, 2002 Edition
A LOOK BACK AT HISTORY
The National Fire Protection Association (NFPA) is best known for the 70 standard, which is a consensus standard reviewed and updated every three years. The NFPA produces many additional standards covering topics such as Aircraft Rescue and Fire Fighting, Finishing Processes, and Wastewater Treatment Plants. There are three standards that pertain directly to electrical workers and equipment:
• NFPA 70 National Electrical Code
• NFPA 70B Recommended Practice for Electrical Equipment Maintenance
• NFPA 70E Electrical Safety Requirements for Employee Workplaces
The NFPA 70 standard, first published in 1979, was the first nationallyrecognized standard for electrical safety in the US and was the reference document used for the Electrical Safety-Related Work Practices (ESRWP) regulation (29CFR1910.331–.335). Although the CRF is a Federal law, the 70E is a standard, which means it is not legally binding.
In July of this year, another revision of the 70E is due to be published. Because of this, a lot of interest is being generated about the standard, what it will contain, and the impact any changes may have on companies and their employees.
So why should we be concerned about the 70E standard? Much of it (speaking from a monetary standpoint) has to do with the fact that if there is a nationally recognized standard and we do not follow it, we are left open for
Jim White Shermco Industries, Inc.
litigation if something should occur. The court would literally “throw the book at us” at trial. Another reason to use the 70E standard is that OSHA accepts the 70E and uses it as their reference, as they have members on the 70E Committee.
The 70E Committee is composed of a wide range of individuals from companies and organizations, such as the IBEW, OSHA, Underwriters Laboratories, protective clothing manufacturers, contractors, and NETA. The OSHA representatives are nonvoting and are there to advise the 70E Committee so that the standard stays compliant with the regulations. At last count, there were 24 members and ten alternates.
One observation I had at the December 70E Committee meeting was that each person on the Committee as well as the people who attended to have their
NFPA 70E AND NETA
views and opinions heard were committed to providing a safe work environment for all employees who have to work on or near electrical equipment. This provided an environment where people can voice their concerns without worrying that they would be ridiculed or harassed. This is extremely important in developing the best recommendations for the standard.
The real reason we should apply the 70E is because it contains the latest, and best, research and methods for working on electrical systems. No one wants to see another person injured or killed. However, we often make decisions based on our ignorance, which can have a negative consequence on our employees’ and on our future.
SOME IMPORTANT CHANGES
One of the major changes is that the current Part II, which covers electrical safety-related work practices, will become Part I. This will give more emphasis on the employee safety requirements. The current Part I, Installation Safety Requirements (basically a paraphrasing of the NEC) will become Part IV.
Some other major changes are with job sites where more than one employer is working, such as when a contractor is working at a company’s job site. Both the contractor and the site representative are to coordinate safe work procedures, including identifying existing hazards, what PPE is required, what safe work procedures are needed, and emergency/evacuation procedures. A physical meeting and documentation of the meeting is also required.
In the 2000 edition of the 70E, equipment and lines that had less than 50 volts to ground received very little mention. In the 2003 edition, it is recognized that low-voltage systems could present a hazard and, if they do, the hazards they present must be accounted for. Conductors and live parts below 50 volts must be placed in an electrically safe condition if they create any hazard. Other changes to the 70E standard include:
• 2-1.1.2, Part II. This section states that unqualified works will be allowed to work on equipment that has been placed into an electrically safe condition by a qualified worker. This was not the case in the 2000 version.
• 2-1.3, Part II. This section has been reorganized.
• 2-1.3.1 through 201.3.3, Part II, Electrical Hazard Analysis. This section requires that both a shock hazard analysis and a flash hazard analysis be performed before any person approaches the Flash Protection boundary. It also requires that the employer document the incident energy exposure at the working distance and what PPE is being used. The Hazard/Risk tables can be used as an alternative. Annex B, the new IEEE 1585 Guide (parts of which are contained in Annex B) or the new Table 2-1.3.3.2 may be used as well as any of the available computer programs.
• 2-1.3.6, Part II (new), Energized Electrical Work Permit. This section states that any work performed within the flash protection boundary requires an energized electrical work permit. An exception was added that allows troubleshooting and diagnostic work to be done without a permit if the worker is protected by performing a hazard analysis. 2-1.3.6, Part II refers the reader to Appendix G for an example form.
• 2-3.2.1, Alertness. This section prohibits allowing employees to work in areas containing live parts if their alertness is impaired due to illness, fatigue, or other reasons.
• 2-3.4.2, Part II, Conductive Articles Being Worn. This section states that unrestrained conductive eyeglass frames are prohibited if they post an electrical hazard. Plastic frame glasses, although not specified, are implied when someone works on or near energized equipment. The wording “unless such articles are rendered nonconductive by covering, wrapping or other means” will be deleted.
• 3-3.3, Part II, Head, Neck and Face Protection. This section now includes face, neck, and chin.
• Table 3-3.9.1, Part II. Many revisions are being made to this Table. When the incident energy exceeds 40 cal/cm2, a new Note 7 is applicable, which reads, “The degree of hazard and risk is too great for this task to be performed while the circuit is energized. This task must be performed only with the equipment in an electrically safe work condition.” At one point, the Committee considered adding a Hazard/Risk Category 5, which would be used when arc energies exceed 100 cal/cm2. It was decided that the hazard from the acoustic wave (blast) of an arc
would, at that point, be primary hazard, so the HRC 5 category would not be appropriate.
• Table 3-3.9.1, Part II also adds notes for diagnostic testing and other types of equipment, such as watthour meters.
• Table 3-3.9.2, Part II. This Table changes wording to allow wearing of other types of clothing besides cotton.
• Table 3-3.9.3, Part II. This Table deletes a column calling out fabric weights to allow for newer clothing systems that may weigh less that previous ones did.
• 3-3.9.4.1, Part II, Layering. This section allow nonmelting, flammable clothing to be worn as underlayers.
• 3-3.9.4.3, Part II, Underlayers. This section allows a small quantity of meltable fibers to be used in undergarment waistbands. There is still a hazard when any meltable fiber is work, as the heat from an arc can be sufficient to melt such clothing, even through flash protective clothing and equipment.
• 3-3.9.4.4, Part II, Coverage. This section requires coverage for the wrists and neck.
• 3-3.9.5.2, Part II, Flash Suits. This section requires that flash suits and their face shields have adequate thermal rating. Face shields were not specifically called out in the previous edition.
• 3-3.9.5.3, Part II, Hand Protection. Leather gloves are required for flash protection. Rubber insulating gloves are required as needed for shock protection.
• 3-3.9.7.2, Part II, Flammability. This section allows the use of cotton or other nonmelting, flammable clothing where work is performed on Class–1 and Class–0 systems and the incident energy is expected to be less than 2 cal/cm2. The 2 cal/cm2 value is not intended to be an arc-thermal rating for cotton, by the way. Cotton, wool, or other flammable material does not provide protection from an arc, it only does not increase the extent of the injury by igniting and melting onto your skin.
• Annex B, Part II. This section now includes the text portion of IEEE 1584-2002. The new portions are added after B–6. In my opinion, this annex is of limited benefit. If the 1584 Guide is going to be used, the calculators that are included are much handier.
NFPA 70E AND NETA
CONCLUSION
This is by no means a complete, or even thorough, look at the new 70E. There are too many changes recommended that would take too long to detail, but the changes included here are some of the more important ones that I believe managers should look for. As this article is being written, the full 70E Committee is sending their ballots in for a final vote, It is possible that some of the proposed changes to the standard will not pass, so do not make any changes yet. As always, everyone should strive to provide a safe work environment, regardless of the status of the OSHA regulations or standards.
Jim White wrote this first 70E & NETA column for the Spring 2003 issue of NETA World. He went on to write 72 consecutive 70E & NETA articles, most co-authored with Shermco Industries’ Ron Widup. Jim also authored numerous feature articles for NETA World and provided an article for every Training Talk issue from Summer 2017 through Fall 2020.
James (Jim) R. White was nationally recognized for technical skills and safety training in the electrical power systems industry. At time of this article, he was the Training Director for Shermco Industries, a NETA Full Member company, and spent his nearly 40-year career directly involved in technical skills and safety training for electrical power system technicians.
PROGRAMMING NUMERICAL RELAYS TO ALARM
BY STEVEN TURNER, Arizona Public Service Company
Numerical protection relays offer the ability to alarm for many abnormal operating conditions, including the health of the relay. Below is a list of typical conditions to alarm for due to an abnormal condition:
• Overexcitation
• Phase undervoltage
• Loss of potential or blown fuse(s)
• Relay firmware or hardware failure
• Relay access
• Over or under station battery DC voltage
• Trip coil monitoring
The purpose of this article is to demonstrate how to set a numerical protection relay to alarm for some of the conditions listed above.
ABNORMAL POWER SYSTEM OPERATING CONDITIONS
Overexcitation and phase undervoltage are two such conditions taken from the list above.
Overexcitation (24)
Overexcitation occurs in a transformer when the magnetic core saturates. Stray flux is induced in nonlaminated components and causes overheating. Numerical transformer relays with phase voltage inputs can detect this
condition by measuring the volts per hertz. A typical alarm threshold is when the measured volts per hertz reaches 105% of the nominal value.
Assume the nominal voltage measured by the relay is 120 volts secondary line-to-line and the power system operates at 60 Hz.
V/Hznominal = 120 volts/60 Hz
V/Hznominal = 2 V/Hz (1 per unit)
105% V/Hznominal = 1.05l(2 V/Hz)
105% V/Hznominal = 2.1 V/Hz
Use the Level 1 volts/hertz element as an overexcitation alarm (Figure 1). Set the pickup equal to or greater than 105% but less than the minimum pickup of the Level 2 element if the relay is also programmed to trip for this abnormal condition. Use a time delay of 1 second to allow time to ride through transient conditions.
Assign the time-delayed Level 1 volts/hertz element to an output contact, which closes on operation to signal the control center this condition exists.
RELAY COLUMN
LVL1 V/HZ PICKUP
LVL1 TIME DLY
100–200% 24D1P := 105
0.04–400.00 sec 24D1D := 1.00
Figure 1: Overexcitation Alarm Settings
Phase Undervoltage (27)
Generators are usually designed to operate continuously at a minimum voltage of 95% of its rated voltage, while delivering rated power at rated frequency. Operating a generator with terminal voltage lower than 95% of its rated voltage can cause undesirable effects such as reduced stability and import of excessive reactive power from the grid to which it is connected. Use the methodology demonstrated in the previous example to set this function to alarm with a fixed time delay.
EQUIPMENT FAILURE CONDITIONS
Loss of potential, relay failure, relay access, and trip circuit monitoring are the conditions covered here.
Loss of Potential (LOP) or Blown Fuse(s)
Loss of potential occurs due to blown potential fuses or by the operation of molded case circuit breakers. The basic principle used to detect this condition is voltage unbalance in the presence of no current unbalance. For example, there is more than a 25% drop in the measured positive-sequence voltage with no corresponding magnitude or angle change in positive-sequence, negative-sequence, or zero-sequence currents. Loss of potential to a relay can cause voltage-dependent protection functions such as phase undervoltage and distance elements to misoperate. It is very important to alarm for this condition so the fuses can be replaced to restore proper operation of any affected voltage-dependent protection functions. Use the methodology
demonstrated in the first example to set this function to alarm with a fixed time delay.
Note: It is a good practice to use this function to block the voltage-dependent protection functions while the condition exists. For example, to supervise phase undervoltage protection elements by using LOP, use the following trip equation:
TR2 := . . . OR 27P2T AND NOT LOP
Where:
TR2 ≡ 2nd Trip Equation
27P2T ≡ Level 2 Phase Undervoltage Element LOP ≡ Loss of Potential
Relay Failure
One relay manufacturer uses the relay word bit HALARM to signal self-test problems. HALARM is pulsed for hardware self-test warnings and is continuously asserted for hardware self-test failures.
Program a normally closed output contact to open if the relay detects a relay hardware failure as follows:
OUT301 := HALARM
The control center senses a relay failure when this output contact is open.
Relay Access
The same manufacturer mentioned above uses the relay word bit SALARM, which is pulsed, for software programmed conditions such as setting changes, unsuccessful password entry attempts, and password change. It is very
important to monitor these conditions due to the need for cybersecurity.
Program a normally open output contact to close if the relay detects any of these conditions has occurred as follows:
OUT302 := SALARM
The control center senses the alarm when this output contact pulses.
Trip Circuit Monitor (TCM)
If the trip coil fails for a circuit breaker or lockout relay (86), then personnel should know this condition exists immediately so that it can be quickly corrected. Figure 2 illustrates the external connections for a trip circuit monitor function.
This function should be programmed to block when the breaker is open, as indicated by the 52b contact input. If the TCM is monitoring a lockout relay, use a lockout relay (86) contact input to block this function when the lockout relay is tripped.
When the output contact is open, and continuity exists in the trip circuit, a small DC current flows, which activates the trip circuit monitor input. If the trip circuit is open, and the output contact is open, no current flows and the trip circuit monitor input is deactivated.
An output contact that is welded closed will also cause the trip circuit monitor input to deactivate, indicating failure of the output contact. When the output contact is closed, no current flows in the trip circuit monitor input. If the relay has issued a trip command to close the output contact and trip circuit monitor input remains activated, this is an indication that the output contact failed to close.
The output of the trip circuit monitor function should be programmed as an alarm to alert maintenance personnel.
CONCLUSION
This article demonstrates how to program numerical protection relays to alarm for specific abnormal operating conditions, including the health of the relay. By using these alarms, it is possible to quickly address such issues and restore the integrity of the power system.
Steve Turner is in charge of system protection for the Fossil Generation Department at Arizona Public Service Company in Phoenix. After working with Beckwith Electric Company, Inc. for 10 years, Steve spent two years as a consultant in San Diego. His previous experience includes positions as an Application Engineer at GEC Alstom and in the international market for SEL focusing on transmission line protection applications. Steve also worked for Duke Energy (formerly Progress Energy), where he developed the first patent for double-ended fault location on overhead high-voltage transmission lines and was in charge of all maintenance standards in the transmission department for protective relaying. Steve has BSEE and MSEE degrees from Virginia Tech University. He has presented at numerous conferences including Georgia Tech Protective Relay Conference, Western Protective Relay Conference, ECNE, and Doble User Groups, as well as various international conferences. Steve is a senior member of IEEE and a member of the IEEE PSRC.
“What are you doing here?” asked the manufacturer’s testing representative. “We are doing start-up of the gear, and your work seems redundant.”
Redundant? That depends on what each of us is responsible for checking. That depends on who is going to ensure that all the known potential failures get checked and as needed, corrected.
As an industrial or commercial buyer, getting a warranty on your new switchgear is great. An extended warranty because you purchased manufacturer acceptance testing and start-up is even better. In addition to a warranty, wouldn’t you like to have a piece of electrical equipment that works reliably for years because it was properly started up?
In this “in the field” situation, the manufacturer didn’t include primary current testing for
breakers or the ground fault protection system. Admittedly, it is rare for a new breaker to fail a primary injection test. In contrast, it is common for a ground fault protection system to fail. This significant increase of failure is directly related to the human elements of installing and wiring the ground fault protection system (Figure 1).
GROUND FAULT PROTECTION FAILURE
Ground fault protection systems come from the factory with several potential error points:
• Incorrect input wiring at the breaker
• Incorrect output wiring of the neutral current transformer (CT)
• Incorrect neutral CT orientation
Ground fault systems have additional potential error points during field installation:
• Incorrect neutral conductor connection to CT orientation
• Neutrals and ground landed together on the same bus in the switchboard or at downstream panels
Figure 1: Overview of Ground Fault System
IN THE FIELD
Assuming that the factory or the contractor installed wiring correctly can lead to issues. These issues typically result in nuisance trips of the breaker that create power outages and production losses. After a system has been energized, a nuisance trip is even more difficult to troubleshoot and correct.
GROUND FAULT PROTECTION TESTING PROCEDURE
Pro-Tip: Trust your testing plan and use good procedures.
1. Trip Test: The breaker should operate during this test because it is simulating an unbalanced phase current without neutral CT input to cancel it out.
a. Inject primary current through the breaker to verify ground fault pick-up per manufacturer’s tolerances.
b. Inject approximately 1.5 times the pick-up value to verify that the breaker trips in the published time band for the coordination setting.
2. No-Trip Test: The breaker should NOT operate because the unbalanced phase current is canceled out by returning the unbalanced current through the neutral CT input.
a. Inject primary current (used in step 1b) through the breaker and return the current through the neutral CT. For this, you will need additional conductors to route the current through the neutral CT.
b. Note that the direction of the current through both the breaker (source to load) and the neutral CT (load to source) should be as shown in Figure 1.
c. If everything is properly installed and wired, the breaker should not trip, as this is a normal current flow situation.
Note on direction of current flow: What is the appropriate direction to return the test current through the neutral CT? Reference Figure 1 again: Neutral current is the normal current that flows on the neutral of an unbalanced three-phase, four-wire system. This current returns from the load(s) through the neutral CT on its way back to the source (transformer).
I had to question my technique when the first of the ground fault protection systems we tested that day failed. After spending some time checking and double-checking, our team moved on to another breaker. To our pleasure, this system worked as we expected it to work.
Given this new piece of validation and information, we:
• Rolled the polarity of the wiring at the CT, even though it matched the wiring of all the other neutral CTs of this type (Figure 2).
• Retested and obtained the no-trip result we expected the first time. While this fixed the operation, the wiring problem was actually at the input to the breaker’s trip unit. As noted earlier, the wiring matched all the other CTs and caused us to question our test procedures.
Figure 2: CT Lead with Incorrect Wiring Polarity
• This information was passed to the manufacturer to correct the wiring at the breaker to avoid a warranty challenge with our team making a modification.
We continued our testing and found one additional CT wiring issue that was legitimately at the CT (Figure 3). Unlike the first CT issue we identified, this CT had three wires. Following the failed test, we noted that two wires were landed into one connection point of the CT leaving one connection open. After a quick comparison to other similar CTs, we relocated the wire to the proper output, and the issue was corrected, rechecked, and operated as expected.
These two big finds helped our customer avoid unnecessary outages in their process. What would have happened if we had not been there to test things that the factory team assumed had been verified at the factory?
IN-SERVICE GROUND FAULT TRIP
Additional complications are possible if a breaker trips on a ground fault event after the system has been in service for many months or even years.
The complication:
• Usually starts with the assumption that the system was properly started up and is working to do its job to protect the equipment from a ground fault event.
• Assumes that the setting is appropriate per the coordination study.
• These assumptions lead to a well-intended facility manager insisting on installing temporary metering in the hopes that you can capture the event. In my experience, the event never seems to occur while the metering equipment is installed. I’m still trying to figure out why that is.
• Many months later, this plan typically leads to another nuisance ground fault protection trip and an outage.
Take the steps necessary to troubleshoot a suspected ground fault trip:
1. De-energize the source of power. This typically creates more frustration for the client, who says, “Can’t you do this with the equipment energized?”
2. Do a trip test and a no-trip test as described earlier.
3. Inspect the installation of the neutral wires. This is particularly important if the CT is mounted on the neutral bus bar.
CASE STUDIES
Following are two case studies related to busbar mounted CTs.
Case 1: A customer experienced repeated ground fault trips that couldn’t be explained.
• The metering didn’t capture anything.
• Our trip and no-trip tests passed.
• Confused and frustrated, I crawled underneath the eight sets of parallel conductors to inspect the neutral CT at the rear of the gear, which was installed against a wall, of course.
Figure 3: CT wiring is landed incorrectly on the secondary of the CT. On the left, note the empty middle connection. The photo on the right shows the connection corrected with the black wire in the middle connection.
• To my surprise, half the neutral wires were landed on one side of the neutral CT and half were landed on the other side (Figure 4). This effectively meant that half of the neutral current flowed through the CT and half did not, which in turn meant that when the conditions were right, enough of the needed neutral current to avoid an operation didn’t flow through the CT.
• It was no easy fix to move all those neutral wires to the correct side of the CT, but after that the unplanned outage calls stopped.
Case 2: A customer experienced a significant ground fault event that the ground fault protection system failed to operate and clear.
• Starting with the basics, we conducted a successful trip and no-trip test — both passed.
• During the inspection of the entire switchboard and neutral wires, it was noted that the installing contractor had landed all the neutrals and all the grounds to the neutral bus.
• By landing the ground conductors on the neutral bus, the contractor effectively defeated the ground fault protection because the ground current from the fault was now passing through the neutral CT.
• When asked why they landed the grounds on the neutral bus, the reply was, “Well, it’s electrically the same point, right?” No. No, it is not. The neutral is a normal current-carrying conductor. The ground conductor only carries current in the event of a fault. Hint: you might see a question like this on the certification exam.
CONCLUSION
When setting up new equipment, we are often the ones charged with ensuring that all known potential failures are checked and corrected if needed. To increase the probability of success,
avoid these mistakes or misconceptions technicians make in the field:
• Assuming the neutral CT is a ground CT and the source of current necessary to operate the ground fault protection.
• Passing current only through the neutral CT, which will trip the breaker at the designated pick-up level. However, this is not the intended operational design of the system and therefore provides no value.
• Failing to include the no-trip test in the acceptance testing plan.
Ensuring you understand the purpose of the neutral CT in a ground fault protection system is another step towards meeting the requirements of NETA technician certification.
Mose Ramieh III is Vice President, Business Development at CBS Field Services. A former Navy man, Texas Longhorn, Vlogger, CrossFit enthusiast, and slow-cigar-smoking champion, Mose has been in the electrical testing industry for 24 years. He is a Level IV NETA Technician with an eye for simplicity and utilizing the KISS principle in the execution of acceptance and maintenance testing. Over the years, he has held positions at four companies ranging include field service technician, operations, sales, business development, and company owner. To this day, he claims he is on call 24/7/365 to assist anyone with an electrical challenge. That includes you, so be sure to connect with him on the socials.
Figure 4: Improperly Landed Neutral Wires
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DISTRACTED DRIVING
BY PAUL CHAMBERLAIN, American Electrical Testing Co. LLC
People are easily distracted in a world filled with more distractions every day. In this day of modern technology, it is easy to get overwhelmed with the number of distracting devices out there, and these devices have encroached upon the driving environment. Cell phones are convenient means to communicate over long distances, but couple them with texting, email, internet, and mobile video, and they are an absolute attention grabber.
They can be coupled with hands-free Bluetooth devices that allow a driver to talk with limited interaction with the phone, and they can be useful in displaying directions when used as a GPS. However, even when using these safer methods of interaction, they divert the attention of the driver from their primary task — driving a vehicle. And cell phones are not the only distractions in a vehicle. People still eat or drink while driving, fiddle with the radio, read the paper or magazines, talk on CB radios, play with smart watches, and perform personal grooming like shaving or brushing their hair. Some vehicles even have video players in them. Drive on the road long enough and look at what the other drivers are doing. It is astounding what people will do while driving and the absurd risks they are willing to accept.
WHERE CAN I FIND MORE INFORMATION?
The National Highway Transportation and Safety Administration (NHTSA), which is part of the U.S. Department of Transportation, has created a website for distracted driving information: www.distraction.gov. It is loaded
with statistics and information that can be disseminated to co-workers and teen drivers and used by employers for employee distracteddriving awareness training.
Here are some key facts and statistics from that website:
• In 2019, 3,142 people were killed, and 424,000 people were injured in motor vehicle crashes involving distracted drivers. More than 26,000 have been killed between 2012 and 2019
• In 2019, an estimated 2.1 trillion text messages were sent in the USA. (https://www.ctia.org/news/report-2020annual-survey-highlights)
• Nine percent of all drivers 15 to 19 years old involved in fatal crashes were reported as distracted at the time of the crashes. This age group has the largest proportion of drivers who were distracted at the time of the crashes. (http://www-nrd.nhtsa.dot. gov/Pubs/812132.pdf )
• In 2019, 566 nonoccupants (pedestrians, bicyclists, and others) were killed in
• The USA had over 442.5 million wireless subscribers in 2019. (https://www.ctia.org/ news/report-2020-annual-survey-highlights)
• In 2019, there were an estimated 287,000 distraction-affected injury crashes (15 percent of all injury crashes). In these crashes, an estimated 294,000 drivers (8% of all drivers in injury crashes) were distracted at the time of the crash. (http:// www-nrd.nhtsa.dot.gov/Pubs/812132.pdf )
• Five seconds is the average time your eyes are off the road while texting. When traveling at 55mph, that’s enough time to cover the length of a football field blindfolded. (http://mcsac.fmcsa.dot.gov/ documents/DriverDistractionStudy.pdf )
• Smartphone ownership is growing. In 2019, 37.1 trillion megabytes of data were
used in the USA. (https://www.ctia.org/news/ report-2020-annual-survey-highlights)
• More than half (53%) of all adult cellphone owners have been on the giving or receiving end of a distracted-walking encounter. (http://www.pewresearch.org/ fact-tank/2014/01/02/more-than-half-of-cellowners-affected-by-distracted-walking/)
WHAT CAN EMPLOYERS DO TO REDUCE DISTRACTED DRIVING?
Employers are certainly not powerless to prevent distracted driving by employees while on company time or in a company vehicle. The U.S.DOT encourages employers to create a distracted driving policy. It will provide videos, posters, and sample policies to encourage better driving habits. There is a lot of hands-free technology available for use that can either be provided for employees, or you can encourage
SAFETY CORNER
Primary enforcement hand-held phone use ban for all drivers
Primary enforcement texting ban for all drivers
Secondary enforecement texting ban for all drivers
Primary enforcement texting ban for novice/beginner drivers
No bans on cell phone use
Figure 1: State Laws Addressing Cellphone Use while Driving
your employees to purchase it. Before purchase, however, be aware of which states allow the use of such devices. The map provides more information regarding hand-free device and texting bans or allowances.
HOW CAN PARENTS PREVENT DISTRACTED DRIVING?
Parents can use videos and talk with the children regarding distracted driving. Many states ban the use of cell phones for young drivers. Additionally, apps are available that parents can put on their children(s) smart phones that will disable the phone while it is in motion. A list of these apps for Android devices can be found here https://bit.ly/2T5DcV2 as an example of what’s available. A similar number are available for use on Apple devices.
Teens and young adults are prone to distractions while driving. With the many social apps available out there, they have a tendency to need to feel “connected” and may
be inclined to pick up the phone when it beeps. Couple that distraction with their inexperience driving, and it can lead to tragedy, as the statistics from the U.S. DOT show.
Teenagers can also make pacts with each other to not use the phone while driving. A friend riding as a passenger can be affected just as adversely by a distracted driving accident as the driver, so they can make it their responsibility to prevent drivers from using the phone while driving.
Adults, for the most part, have less connection on social networking and don’t tend to reach for the phone each time it beeps, and their accumulated windshield time has given them the experience necessary to react better in emergency situations. However, they do have reduced reaction time, which slows as you age, and can be distracted due to other outside forces. These can include lack of sleep (i.e. new parents, stressful work, etc.) or time pressure (i.e. in a rush to get to work). So teens AND parents should take a pledge together to
SOURCE: NCSL, 2020
concentrate on driving and to avoid or mitigate those distractions that affect them the most.
HOW CAN TEACHERS PREVENT DISTRACTED DRIVING?
Schools can get involved in reducing distracted driving, too. They can run a pledge drive, encouraging students and other educators to not drive distractedly. They can use the various posters or videos available to spread the word on distracted driving. They can also encourage parents to use some of the methods mentioned above to mitigate a teen or young adults distracted driving.
HOW ELSE CAN DISTRACTED DRIVING BE PREVENTED?
Local community groups, such as churches or other youth groups (i.e. the Boy Scouts of America) can get involved in reducing distracted driving. Distraction.gov has a free
SAFETY CORNER
downloadable campaign kit available for these groups. Additionally, voters can support local driving laws and ensure their local police departments enforce those laws.
CONCLUSION
Many things can divert a person’s attention from driving, and in this digital age, the cell phone is probably the most prevalent. Communicate with others about distracted driving and follow your state laws. Make it a point to be a better, more attentive driver, and it will be hard not to see the improvements in driving ability.
Paul Chamberlain has been the Safety Manager for American Electrical Testing Company Inc. since 2009. He has been in the safety field since 1998, working for various companies and in various industries. He received a Bachelor of Science from Massachusetts Maritime Academy.
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TECH Quiz
A LOOK BACK AT HISTORY
1. Describe the function of polarity marks on current transformers.
2. Transformer differential relays protecting a 50 MVA, 138 kV – 13.09 Y/7.56 kV transformer have been operating normally during the construction phase of a project. When the transformer is being brought up to full load it trips. There is no indication of a fault, as all tests on the transformer and cable are acceptable. What are the most likely causes?
3. What is the definition of a CT accuracy class (i.e. Class C200)?
4. Relay CTs are available in either Class C or Class T. What is the difference? No. 61
Jim White wrote his first Tech Quiz in the Fall 2002 issue of NETA World. He would go on to write 75 consecutive Tech Quiz columns over the next 19 years of his service to NETA and the industry. Nationally recognized for technical skills and safety training in the electrical power systems industry, Jim never turned down a request from NETA World staff for support or guidance. He will be missed.
James (Jim) R. White, Vice President of Training Services, had worked for Shermco Industries Inc. since 2001. He was a NFPA Certified Electrical Safety Compliance Professional and a NETA Level 4 Senior Technician. Jim was NETA’s principal member on NFPA Technical Committee NFPA 70E®, Electrical Safety in the Workplace®; NETA’s principal representative on National Electrical Code® Code-Making Panel (CMP) 13; and represented NETA on ASTM International Technical Committee F18, Electrical Protective Equipment for Workers. Jim was Shermco Industries’ principal member on NFPA Technical Committee for NFPA 70B, Recommended Practice for Electrical Equipment Maintenance and represented AWEA on the ANSI/ISEA Standard 203 Secondary Single-Use Flame Resistant Protective Clothing for Use Over Primary Flame Resistant Protective Clothing. An IEEE Senior Member, Jim received the IEEE/IAS/PCIC Electrical Safety Excellence Award in 2011 and NETA’s Outstanding Achievement Award in 2013. Jim was Chairman of the IEEE Electrical Safety Workshop in 2008 and was Vice-Chair of the IEEE IAS/PCIC Safety Subcommittee.
4. Class C means the CT accuracy can be calculated, while Class T means it must be measured.
3. The accuracy class of a CT (C100, C200, etc.) indicates the maximum output voltage the CT can sustain at 20X full secondary current (100 amperes) without exceeding a 10 percent error.
2. One cause could be incorrect tap setting. Others are incorrect CT connection or miscalculation of the mismatch ratio. During startup, there often is not enough load (operating current) to cause a minimum trip operation. As load increases, operating current increases until a trip occurs.
1. At the instant that current flows into H₁,it also flows out of X₁. This is on the positive half cycle. On the negative half cycle, current flow reverses, and at the instant current flows into H₂, it also flows out of X₂. Since we are dealing with alternating current, the polarity marks indicate relative instantaneous polarity.
ANSWERS
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Replacement of control wiring; SCR’s; SCR firing board; current transformers; poor connections & wiring.
GENERAL MAINTENANCE & CALIBRATION
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2 Model dependent.
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BTS-1000
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BT-120DC
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HC-100
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PS-1000
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BTS-300
THE IMPORTANCE OF GROUNDING RENEWABLES
BY JEFF JOWETT, Megger
The rapidly developing industry of renewable power generation can be compared to an hourglass. Inexhaustible supplies of free resources — sun and wind — are converted into a corresponding outflow of electrical energy at notable return on investment. But the process includes the neck of the hourglass through which the resources must pass. This is the solar array or wind tower. These two assets must be diligently kept functioning at maximum efficiency and safety in order for the process to yield its anticipated return.
Nacelle Destroyed by Lightning Strike
WIND
Wind towers are particularly at risk because of their great height: 280 feet and getting taller. It is estimated that a tower extending more than 50 feet above surrounding structures becomes a prime lightning target. Lightning interruptions cause up to 50% of typical downtime, depending on locale. And damage isn’t limited to structure. It can extend all the way down to sensitive control systems, further limiting profitability.
The National Lightning Safety Institute recommends that protection begin as early as site selection and proceed through system design. Yet the Institute estimates that maximum lightning protection can be achieved at only 1% of the total cost of a new project. Useful sources of standardization are available in IEC 61024 and IEC 61400-24.
SOLAR
Solar panels are at similar lightning risk as wind towers, as they are installed on roofs or vast open fields where they may be the highest structure.
The National Electrical Code (NEC) specifies:
Exposed non-current-carrying metal parts of module frames, equipment, and conductor enclosures shall be grounded.
Components like inverters, combiner boxes, and disconnects are connected by an equipment-grounding conductor. Every module must be connected to an equipmentgrounding conductor. These converge commonly at the ground busbar inside the main distribution panel. From here, the grounding electrode conductor completes the connection to the ground electrode. When removing panels, care must be taken not to
Open solar fields are prime lightning targets.
disrupt the bonding. For roof mounts, this is often rebar in the foundation, but it should be supplemented by a ground rod to prevent damage to the concrete during fault clearance. Full requirements are described in NFPA 70, NFPA 780, NEC Article 250, NEC Article 690, and UL 96A.
GROUNDING SYSTEM
The tower and array should be designed, constructed, installed, and maintained according to the highest industry standards. An indispensable part of this is the grounding. It is easy to become focused on the dynamics of this process, such as the turning of blades or the humming of transformers, and overlook the indispensable contribution made by the grounding system. Buried out of sight and not visibly operating, these critical components can be largely out of mind until an event occurs, such as a wind tower crashing to ground after a lightning strike.
Don’t wait for such an event to happen! Ensure the system is designed and installed in accordance with industry standards and local conditions first, and then periodically checked and maintained on a regular basis.
It is commonly thought that burying a rod and connecting the electrical system means it is grounded, but that is not necessarily the case. The grounding system must be treated with the same attention and care as any other electrical component.
GROUNDING CONDUCTOR
The other main element of this protection is the grounding conductor. No matter how good the grounding electrode (rod, grid, or other structure) is , it will be rendered useless without a continuous, low-impedance path to conduct lightning and fault current around equipment and personnel and safely into the soil. This is the job of the grounding conductor. In general applications, it connects the dead frame of equipment to the ground bus at the entrance panel.
But in wind generation, its structure is unique: It spans from the tips of the blades to connect with the ground grid at the base of the tower. Frequency of lightning strikes increases with height, and studies have suggested that rotating blade tips are additionally attractive.
Blade tips are particularly vulnerable to lightning.
For adequate protection, the grounding conductor must be regularly tested. Turbine manufacturers typically specify 15–30 mΩ for a safe path to ground. A low-resistance ohmmeter is the designated tester for this purpose. Traditionally, these testers utilize a 10 Amp test current to reliably assure a sufficiently low-impedance path. These can be bulky, given the physical demands of this testing environment.
Recent improvements in meter technology, however, have made the job easier by introducing handheld 1 Amp testers with sufficient accuracy and resolution. The most sensitive part of the ground path is through the blade because the stress of motion can cause the grounding conductor to crack. If the two fragments remain in contact, a simple continuity test will still pass. A more robust test current and measurement resolution will unerringly reveal such a break.
But there’s still a unique problem: the distance of the blade tips from the ground. As with handheld testers, technological advances were in order and have been realized. Test leads with lengths of 100 meters have become available. The long leads create an additional problem: resistance. A compensation factor allows for power loss in some instruments when using leads of a normal length. Compensation for extra-long leads is accomplished via the formula:
P = I2R
Where:
P = output power of the instrument
I = output current of the instrument
R = (resistance of load) + (resistance of test leads)
Standard compensation in the average meter can fall short of delivering enough power against such a daunting lead resistance as would exist in 100-meter leads. Adequate compensation is achieved by reducing test current. Some instruments have a selector
switch to reduce current; others do so automatically. Either way, a 1 amp test current has proven sufficient to yield accurate, reliable test results. The ohmmeter is thereby enabled to test with milli-ohm resolution without lead resistance entering the measurement.
REMOTE EARTH
The termination of the protection system is the electrode buried in earth. This must not be taken for granted. The mere fact of its existence is not enough, although it is often thought of in that manner. No, it must be tested, like any other electrical component. Surge arresters alone are inadequate without a good ground. The goal is low resistance to what is referred to as “remote earth” — that is, the maximum resistance a fault current or lightning stroke will encounter before being safely dissipated. There is no universal standard, but electrode resistance should be held to values like 1–5 Ω.
TESTING AND MAINTENANCE
Testing is particularly difficult with renewables because a single electrode is not grounding a single network, as in a building. Rather, potentially enormous numbers of wind towers and solar panels are daisy-chained together, and the chain is often growing. The biggest problem is that ground testing requires long leads strung to test probes far out in the soil, with the distances based on multiples of the maximum dimension of the grid or array. This can quickly become prohibitive. Unfortunately, there’s no simple answer. But one of the worst things to do is to wait until the job is done before testing. By that time, the composite electrode can be virtually too big to test.
Plan ahead, and test the sections as they are installed. This applies to both solar and wind, as the issue is the same. Every time a new section is paralleled in, resistance will drop significantly. So collectively, by the time the job is done, an adequate ground will be provided. Periodic maintenance also needs to
be performed, as we’ve seen, and this can be a bigger challenge.
The most widely respected ground electrode test, fall of potential, is likely to require too much space. Be familiar with methods that have been specifically designed to deal with this problem. The most prevalent is the slope method. Another is intersecting curves. Instructions for these methods are commonly available in the literature. Additionally, lightning protection and power grounding have different criteria, so be certain requisite conditions are met for both. Power grounds
may be shallow-buried, and this may not afford sufficient protection from lightning.
The grounding system must be tested upon installation for initial conformance to specs and standards, and then periodically thereafter. The familiar “out of sight, out of mind” can be deadly here. Clearance of lightning strikes and electrical faults will often work as intended, leaving the tower structure and function unharmed. But in the process of clearance, the grounding electrode can be seriously compromised, and it is dangerously out of sight. Regular testing, as well as after known strikes, is necessary. Changes in soil composition, especially moisture and subsurface corrosion, can have the same effect on a longer time scale.
Copper theft, a problem throughout the electrical industry, can be particularly acute on wind farms because of their size and remote location. In addition, grounding is often buried at much shallower depths than cabling, making theft that much easier. The clamp-on ground tester can be a useful tool here as a quick means of determining whether continuity exists or has been corrupted by theft.
Studious and thorough record-keeping is particularly in order, as comparing results can be especially informative in recognizing problems and issues. It’s also a good idea to note exactly where test probes are placed. Subsequent testing can then be done for comparison to stored records. The data is useful for maintenance to note changes, even if the size of the grid precludes objective accuracy to remote earth. Provided testing is precisely repeated, changes in results can be indicative of issues that need to be addressed.
CONCLUSION
Effective grounding is indispensable to the safe and efficient operation of renewable energy sources, wind towers, and solar arrays. The two are identical in requiring a continuous, low-impedance path to ground and a low-
A Well-Maintained Solar Field
Wind Generator Blade Destroyed by Lightning
impedance connection to the surrounding earth. The test equipment is the same for both, and procedures are only slightly — but critically — adjusted to the site.
REFERENCES
Richard Kithil. “Lightning Hazard Reduction At Wind Farms,” National Lightning Safety Institute, 26 April 2010.
Paul Swinerd. Megger Application Note: “Earth Testing On Wind Farms”
Bruce Thatcher. “Grounding: The Key To Lightning Protection,” Sankosha, USA. 2016.
Megger. “Getting Down To Earth: A Practical Guide to Earth Resistance Testing.”
Jeffrey R. Jowett is a Senior Applications Engineer for Megger in Valley Forge, Pennsylvania, serving the manufacturing lines of Biddle, Megger, and MultiAmp for electrical test and measurement instrumentation. He holds a BS in biology and chemistry from Ursinus College. He was employed for 22 years with James G. Biddle Co., which became Biddle Instruments and is now Megger.
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ONSITE PD TESTING OF CAST-RESIN TRANSFORMERS IN WIND FARMS
BY
MATHIEU LACHANCE, OMICRON electronics Canada, and DR. ALEXANDER KRAETGE, OMICRON electronics Germany
Installed wind power capacity in the United States has been growing at an incredible pace during the last two decades. In the middle of 2020, the total American wind power capacity was nearly 110,000 MW with over 60,000 turbines installed (Figure 1).
It is known that power equipment used to connect renewables faces very specific and increased stress when sources of fluctuating nature are involved. Large-scale wind and solar
power often utilize transformers of different types within one installation. A typical wind farm electrical installation includes several small transformers (referred to as generation
transformers in this article) connecting single wind turbines to a main bus feeder. Several feeders then connect the substation to the power grid using one or more larger power transformers.
For a better understanding of typical topology, please refer to Figure 2. While these power transformers typically do not show reduced life expectancy compared to other grid transformers, a higher rate of failures has been reported for generation transformers installed in wind farms, including liquid-filled as well
Figure 1: U.S. Wind Capacity in 2019
Figure 2: Typical Topology of a Wind Farm
as cast-resin transformers. The latter are widely applied when special measures for fire or ground water protection are required.
Generation transformers used in wind power plants typically have rated power ranging from 1 MVA to 4MVA, with primary voltages usually below 1,000 V and secondary voltages of up to 36 kV. Larger units with rated power up to 14 MVA are also available, but their failure rates seem lower.
In most cases, problems occur in the insulation system. Identified reasons include overheating due to very narrow design restrictions, vibrations, frequent thermal cycling, impact of frequency converter signals, high humidity, and salty air. Consequently, periodic diagnostic condition assessment is requested more frequently, as failures cause increasing outage costs for repairs and, often even worse, undelivered energy.
For cast-resin transformers, the application of typical diagnostic tools is very limited due to the specifics of molded, air-cooled windings. The most common reason for failure of this type of transformer is electric breakdown of the epoxy-resin insulation. Therefore, including off-line partial discharge measurements during commissioning and in a periodic maintenance plan can reduce the risk of in-service failures.
PD measurements on transformers can be quite challenging when performed onsite. If done online, the level of interference is usually above the permissible limit of a factory test. Therefore, PD occurring below the noise floor can go undetected. On the other hand, the logistics to perform offline PD measurements on transformers installed in remote and constricted space locations, such as wind farms, can be very complicated.
This article shares a modern method to perform offline PD measurements using induced voltage on medium-voltage transformers installed in the field in challenging environments such as remote locations, constricted space conditions, and areas with high electromagnetic interferences.
MEASURING PARTIAL DISCHARGE IN TRANSFORMERS
Partial discharges are localized dielectric breakdowns of a small portion of an insulation system under electrical stress. It can occur in solid, liquid, and gaseous electrical insulation. Most insulation systems used in transformers are not resistant to PD, and sustained PD activity will therefore result in erosion of the insulation. Over time, this can lead to inservice failures.
Accurate PD measurement can help identify weak points within the insulation system before complete insulation breakdown. For this reason, many international standards require or recommend PD measurements during the production of various MV and HV equipment. Commissioning and preventive maintenance of equipment during its service life is also increasingly recommended.
PD measurement may be performed on the windings of all types of dry-type transformers. For transformers with solid-cast windings with rated voltage above 1.2 kV, partial discharge measurements are an integral part of the routine tests performed at the end of the manufacturing process. The measurement is done during the induced voltage test by applying voltage to the low side of the transformer and measuring PD on the high side. Unlike the conventional applied voltage test, commonly called hipot, the induced voltage test stresses both the turnto-turn insulation and the insulation to ground above the rated voltage.
In order to increase the test voltage above the rated voltage of the transformer, the frequency must be higher than 60 Hz to avoid core saturation without introducing significant interference pulses that may be detected as PD signals. In addition, the voltage source must be powerful enough to supply the needed reactive power at higher frequencies. Traditional voltage sources used in factories include large motor-generator sets (MG sets) or frequency converters. On many occasions, a capacitor
bank is also used to compensate completely or partly for the needed reactive power.
PD test procedures are described in IEEE C57.12.91, IEEE C57.124, IEC 60076-11, and in IEEE C57.113 in the case of liquidfilled transformers. In dry-type transformers, a phase-to-phase pre-stress voltage of 1.8 x Ur is induced for 30 seconds, followed by a phaseto-phase voltage of 1.3 x Ur for 3 minutes, during which PD is recorded. For in-service or aged transformers, the voltage level is usually reduced to 80% of the factory acceptance test (FAT) level. The maximum level of PD must be less than 10 pC for solid cast windings and 50 pC for resin-encapsulated windings. As an example, the test sequence according to IEEE C57.12.91 and a three-phase connection diagram according to IEC 60076-11 are respectively illustrated in Figure 3 and Figure 4.
FROM THE FACTORY TO THE FIELD
For onsite PD measurements on transformers, the expectations for a voltage source are raised. In addition to the previously stated requirements to perform induced voltage tests at the factory, the voltage source must be able to function on the limited power available from a regular power outlet, as mobile diesel generators are not always available and must be portable for confined space conditions. A great example of such a space requirement is when testing a transformer installed inside the tower or the nacelle of a wind turbine or installed deep inside a facility with difficult access.
To reduce the power requirement, the onsite test is performed using a single-phase voltage source. The required power is therefore significantly reduced compared to the conventional three-phase test. In addition, energizing one phase at a time is usually the next step when PD is detected during a threephase measurement. To further reduce the required power, a modern voltage source that can freely control the frequency and that can measure the impedance of the complete test circuit is used. The test frequency can therefore
5: Test Circuit Impedance vs. Frequency
be tuned to the resonance frequency of the given test circuit, including the inductance of the transformer, the winding capacitance, and the coupling capacitor used for PD measurement. Figure 5 illustrates an example of the frequency response of such a system. If the test frequency is set to the maximum value in the blue curve (highest impedance), the required test power is minimized.
Figure 3: PD Test Procedure According to IEEE C57.12-91
Figure 4: PD Test Arrangement According to IEC 60076-11
Figure
COVER STORY
not intended to be used on-site, even though it is recommended practice to apply its rules if possible.
In rare cases, the required power can still be too high for a conventional power outlet. In these cases, additional low-voltage capacitors can be used to compensate for part of the reactive power needed to energize the winding. Practical experience has shown that 10–100 uF are enough. Since these capacitors are installed on the low-voltage side of the transformer (typically 600–690 V), commercial availability is usually not an issue. Figure 6 shows an example of the test setup used for onsite testing with low-voltage capacitors for reactive power compensation.
ONSITE INTERFERENCE
Partial discharge measurements outside of Faraday cages are most often troublesome due to electromagnetic interference from the surroundings. For example, PD in cast-resin insulation will sooner or later lead to severe problems, as these types of insulation are not self-healing. PD will erode the insulation over time, and the dielectric strength will decrease more and more. Thus, very small levels of PD must be found and clearly identified. External interferences are often far higher than the PD signals to be detected. To overcome these challenges, modern fully digital PD instruments employ several denoising methods that can reduce or even eliminate such noise problems. A great advantage of digital compared to analog filters is their flexibility to adapt bandwidth and mid-band frequency to the actual measuring conditions. While the strict boundary conditions of IEC 60270 apply for measurement in the factory, this standard is
As the aim of on-site PD testing typically is risk assessment, the steps to achieving the goal include reliable detection of harmful PD, identification of PD type, and location of the PD spot(s) if necessary. Evaluation of the pC-value describing the intensity is of less importance, especially if assets with nonself-healing insulation are to be investigated. Therefore, it is common for practical reasons to set the digital measuring filters of the PD instrument to frequency ranges with a lower background-noise floor. Variation of the filter bandwidth can also help to achieve a better signal-to-noise ratio (SNR).
Another powerful method is to utilize multiband measurement filters, often referred to as the 3-center frequency relation diagram (3FREQ or 3CFRD) method. This requires three PD bandpass filters measuring every PD event simultaneously at their predefined mid-band frequencies. The synchronous consideration of three different frequency parts of the spectrum of each single PD pulse provides information on its discharge nature, signal propagation, and path attenuation. A comprehensive investigation of the spectral behavior of different types of pulses is given in reference. Selection of these three bandpass positions in the frequency domain is the key to gaining optimum benefit. By applying 3CFRD, it is possible to discriminate between pulses of different type or same type but different origin.
Figure 7 shows a simplified theoretical schematic of the principles behind 3CFRD. The red arrows indicate the response of PD pulse #1 at the discrete filter frequencies. These response values are represented by the starshaped 3CFRD diagram as shown on the right side of Figure 7. The lengths of the phasors represent the measured response magnitudes, and the axes indicate the respective filter frequency. By adding the phasors of the PD responses, one single dot is the final
Figure 6: Voltage Source with Capacitive Compensation, Test Object, and Coupling Capacitor
representation of the initial triplet. Figure 7 shows an example of a measurement where 3CFRD was applied to separate different types of PD.
PROOF OF CONCEPT
Like any innovative solution, the concept had to be proven first. Therefore, measurements took place in collaboration with manufacturers of cast-resin transformers and with wind turbine manufacturers. Figure 8 shows an initial test that was performed on a 6 MVA wind farm transformer in the factory, along with its corresponding installed location in the wind turbine.
A pre-stress voltage of 52 kV was induced for 30 seconds, followed by three minutes at 42 kV where PD was measured. No PD activity was detected during the test.
To test the applicability of onsite induced voltage testing with PD measurements once the transformer is installed in the nacelle, a test was successfully conducted on a preparation site of a large, offshore windfarm. Figure 9 shows the test setup.
CASE STUDIES
In recent years, several measurements have been performed using this innovative testing solution. It has also been applied outside wind farms at other applications including transformers used for the excitation of hydrogenerators and transformers installed in constricted space conditions inside industrial facilities or on ships.
9: On-Site PD Measurements during Induced Testing of an Installed Transformer
Case
Study #1: 34.5 kV
A 34.5 kV wind turbine transformer known to have PD activity was tested at 40 kV, and several PD sources were able to be identified. Figure 10 shows the transformer during the test and its regular position in the wind turbine. In
Transformer with Known PD Activity in a Wind Turbine
Figure 7: Simplified Theoretical Schematic of 3CFRD
Figure 8: Test Setup in the Factory and Installed Position in the Nacelle
Figure
this case, it is obvious that a small, portable test set was a necessity.
Figure 11 shows the initial phase-resolved partial discharge (PRPD) diagram on the left and its corresponding 3CFRD diagram on the right.
Figure 12 shows the individual PRPD diagrams from each selected cluster of the 3CFRD diagram. The top PRPD diagram shows contact-related PD activity; the other two PRPD diagrams show signs of internal and surface discharges. The transformers had visible signs of carbonized tracks, which indicates PD activity sustained over some time.
Case Study #2: Commissioning a Hydro-Generating Station
Following the commissioning of a remote hydroelectric power plant, PD measurements
were requested after two of eight 10 MVA transformers, installed to excite the 400 MVA asynchronous generators, had failed. The goal of the measurements was to assess the insulation of the remaining six transformers. The transformers’ rated voltage was 19 kV on the high side and 3.9 kV on the low side. For this reason, an additional step-up transformer was needed. Figure 13 is an aerial photo of the remote generating station and a photo of the test setup.
For these measurements, an equivalent of the factory test was required and therefore had to be done according to IEC 60270. This led to higher background noise due to external signals from nearby power electronics that could not be switched off. Using an advanced, fully digital PD instrument and the 3CFRQ cluster separation method, it was possible to confirm that no internal PD was present with a sensitivity of less than 30 pC, which was considered acceptable under the given circumstances. All transformers passed the test successfully.
Case Study #3: Diagnostic Measurement in a Data Center
Partial discharges were detected by an online PD monitoring system for a length of mediumvoltage cable in an important data center. An offline PD measurement showed clearly that the cables were PD-free. A connected 2 MVA/20 kV transformer was identified as the possible source of the detected PD signals. A subsequent induced voltage test provided clear indication of the presence of void-type
Figure 10: PD Measurement on a Transformer (left) and Position in a Wind Turbine (right)
Figure 11: PRPD Pattern of the Three Filters (left); 3CFRD Measurement (right)
discharges within the solid insulation. The inception and extinction voltages were both below the transformer’s rated voltage; therefore, the risk of failure was considered high. As all phases were affected, replacing the windings was not economically justifiable; thus, the transformer had to be replaced. Figure 14 shows the test setup and the measured PRPD diagram depicting void-type discharges.
CONCLUSION
Modern test equipment opens all kinds of new testing possibilities. Historically, onsite PD measurements for medium-voltage transformers have been difficult to perform. With the latest advancements in technology, use of a flexible and portable voltage source for PD testing combined with fully digital PD measurement technology opens new onsite
Figure 13: Aerial Photo of the GS (left); MVA Transformer under Test (right)
testing possibilities. This results in increased reliability for modern power generation and industrial facility operators in addition to creating new business opportunities for service providers.
REFERENCES
IEEE Std. C57.12.91-2020, IEEE Standard Test Code for Dry-Type Distribution and Power Transformers, (Revision of IEEE Std C57.12.91-2011).
IEC 60076-11, Power transformers – Part 11: Dry-type transformers, International Electrotechnical Commission, Geneva 2004.
IEEE Std. C57.124, IEEE Recommended Practice for the Detection of Partial Discharge and the Measurement of Apparent Charge in Dry-Type Transformers, 1991.
IEC 60270, High-Voltage Test Techniques –Partial Discharge Measurements” International Electrotechnical Commission, Geneva 2015.
A. Kraetge, K. Rethmeier, M. Krueger, P. Winter. “Advanced noise suppression during PD measurements by real-time pulse waveform analysis of PD pulses and pulse-shaped disturbances,” IEEE ISEI, San Diego, 2010
A. Kraetge, C. Engelen, W. Guo, M. Kruger. “Field-Testing of Cast-Resin Transformers in Wind Farms, industrial and Marine Applications under Constructed Space Conditions,” Proceedings of TechCon Aus-NZ, Sydney, Australia, 2018.
Mathieu Lachance joined OMICRON electronics Canada Corp. in 2019 and presently holds the position of Regional Application Specialist for rotating machines and partial discharges. Matthieu previously worked as a test engineer in the fields of partial discharges and high voltage. He received a BS in electrical engineering from Université Laval in 2014.
Dr. Alexander Kraetge is a transformer expert and key account manager for the transformer industry with OMICRON electronics in Germany. After working as a professional electrician, he studied high-voltage engineering at the Berlin University of Technology and earned a PhD in transformer condition assessment. Alexander has held several technical and senior management positions within OMICRON, Austria, and Highvolt, Germany. He is an IEEE Senior Member, a member of the IEEE Transformers Committee, and is actively involved in Cigré D1 and A2. He has authored more than 100 technical and scientific publications, mainly about condition assessment of transformers and partial discharge diagnostics.
Figure 14: Test Setup (left); PRPD Diagram for all Three Phases (right)
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PROTECTING WIND TURBINES THROUGH EFFECTIVE GROUNDING
BY SAMEER KULKARNI and DR. AHMED EL-RASHEED, Megger
The share of wind power in total electric power generation is expected to increase, and with that comes a requirement for this carbon-free source to be more reliable. The wind turbine, which is the most important component of a wind power system, is exposed to harsh environmental conditions and electrical transients such as lightning strikes. Naturally, understanding the lightning protection scheme of the wind turbine and checking its integrity is vital to protect it during lightning strikes such that continued, reliable operation is achieved.
Recent international studies have shown that in one European country, 80% of insurance claims on wind turbines resulted from lightning-related damage. Similarly, a major US utility reported that over 85% of their wind turbine downtime was due to lightning-related damage.
This article provides a general overview of the lightning protection system of a wind
turbine, the best practices for lightning protection on wind turbines, and how to verify effectiveness. It discusses the need and advantages of various tests performed to verify the continued integrity of such lightning protection systems, and shares reference quantities for testing parameters and expected results while reviewing some practical and safety considerations.
WIND POWER
Renewable energy — and wind power, in particular — is growing at a rapid pace. In 2020, new installations of wind power provided 93 GW globally. The year-over-year growth is
53% with both the United States and China leading the world in new installations of wind power generation. Wind power answers the pressing needs and circumstances of the day. It is a relatively inexpensive and green energy source that addresses constrained infrastructure budgets as well as climate-change policies. Most market analysts indicate that wind power development will continue to grow at a fast rate because all the driving factors for its adoption persist.
This is great news for the electrical power industry, as there will be growth and opportunity for many years to come. However, this growth will require improved maintenance programs that will protect the investments and maximize the profits from wind power.
LIGHTNING STRIKES
The biggest maintenance problem for wind power is lightning strikes (Figure 1a and Figure 1b). According to Vestas CEO Henrik Andersen, intense lightning strikes were the biggest driving force behind the record warranty claims of €175M (US$212M) in just the second quarter of 2020. Wind turbine manufacturers and installers like Vestas recognize the immense danger of lightning strikes and take great care in the design of turbines. Still, operators and owners of wind turbines must ensure a robust and effective maintenance program for their assets.
LIGHTNING PROTECTION SYSTEMS
A growing number of studies speculate that rotating wind turbines may be more susceptible to lightning strikes than stationary structures. Wind turbines are at an increased risk of being struck by lightning due to their height and the locations used for wind farms. Lightning faults cause more loss in wind turbine availability and production than the average fault. Wind turbines are equipped with lightning protection to minimize damage from direct lightning strikes and to shield sensitive
Figure 1a and Figure 1b: Lightning Damage to Wind Turbines
equipment integral to wind turbine operation. A lightning strike would not only have a large magnitude of current but would also impress an unwanted electromagnetic field across components housed in the nacelle and base of the tower. The lightning protection system (LPS) performs the function of directing the current strikes to ground.
Lightning Protection Zones
To facilitate the coordination of protections functions, it is prudent to divide the wind turbine into lightning protection zones (LPZ). The lightning protection zone concept is a structuring measure for creating a defined, electromagnetically compatible environment in an object while being cognizant of the object’s stress withstand capability.
IEC 62305, Standard for Lightning Protection defines the LPZ for structures and can be applied to a wind turbine. The zones are classified into external and internal zones based on their exposure to direct lightning.
External Zones
• LPZ 0A is the zone where the threat is due to the direct lightning flash and the full lightning electromagnetic field. The internal systems may be subjected to full lightning surge current.
• LPZ 0B is the zone protected against direct lightning flashes but where the threat is the full lightning electromagnetic field. The internal systems may be subjected to partial lightning surge currents.
The rolling sphere method is used to determine LPZ 0A — the parts of a wind turbine that could be subjected to direct lightning strikes, and LPZ 0B — the parts of a wind turbine that are protected from direct lightning strikes by external air-termination systems or airtermination systems integrated in parts of a wind turbine (for example in the rotor blade), as seen in Figure 2 and Figure 3.
Figure 2: Simplified Wind Turbine External LPZ
Figure 3: Air Termination Systems Installed for Wind Turbine Nacelle
Internal Zones
• LPZ 1 is the zone where the surge current is limited by current sharing and isolating interfaces and/or by surge protection devices (SPD) at the boundary. Spatial shielding may attenuate the lightning electromagnetic field.
• LPZ 2 to LPZ n are the zones where the surge current may be further limited by current sharing and isolating interfaces and/or by additional SPDs at the boundary. Additional spatial shielding may be used to further attenuate the lightning electromagnetic field.
The LPS essentially works by taking the form of a low-resistance path to ground. The path goes from the blade’s tip to the base of the turbine. This path is shown in Figure 4 and Figure 5.
In the event of a lightning strike, current will flow to ground through the lightning protection system, not the sensitive equipment in the wind turbine. As the lightning current is dissipated through the grounding system, it is important to not cause thermal or mechanical
damage or arcing that may lead to fires or personnel injuries. To ensure that protection in the above zones will work when needed, the resistance of the path to ground should be measured at regular intervals, making sure it meets the limits specified by the turbine
Figure 4: Current Path for Lightning Discharges
Figure 5: Foundation Earth Electrode at Wind Turbine Base
manufacturer (typically limited to 15–30 mΩ, depending on turbine size). For these tests, use of a low-resistance ohmmeter is recommended.
METHODS TO VERIFY LIGHTNING PROTECTION SYSTEMS
Measurement of low resistance is affected by key factors such as measurement type, test current magnitude, length of measurement leads, and placement of leads/probes.
Four-Wire Method
The four-wire method (Figure 6) is most appropriate because it uses separate current probes to inject direct current (DC) and separate potential probes to measure the voltage drop across the test specimen.
In some practical cases, a Kelvin measurement — where current and potential probes are 180° apart — is also employed to measure lowresistance values. The use of any other methods such as a two-wire method may not be suitable, as the measurement contains contact resistance values of the probes, thereby clouding the measurement.
Testing Wind Turbine Lightning Protection
As introduced in the preceding sections, the most important part of the LPS is to test the conductor from the blade tip to the down conductor inside the hub that ultimately connects to the ground grid as was shown in Figure 5 and is depicted in Figure 7 and Figure 8.
This conductor is placed under significant strain as the blade flexes with the wind during normal operation. Under strain, the conductor may fracture. Unfortunately, it is not enough to simply check continuity because, if the fractured conductor is touching at the break point during a continuity test, the result will not be satisfactory. Consequently, a test current magnitude of 1 A or more is recommended for this test.
Figure 6: Four-Wire Method
Figure 7: Lightning Conductor Resistance Measurement at Blade Tip
Figure 8: Lightning Conductor Resistance Measurement at Wind Turbine Hub
The length of a turbine blade can be seen in Figure 9. The size of the turbines poses a problem because low-resistance ohmmeter test leads are typically very short. Due to the size of the wind turbines, some extra-long leads are required, often up to 100 m. This is a huge increase in length over standard test leads for low-resistance ohmmeters. The long leads must be designed with a low enough resistance to ensure that a measurement is still possible. To achieve this, it is important to understand the test instrument design.
Some instruments have a compensation factor to allow for power loss in standard test leads. When using long test leads, the compensation for power loss will no longer
be sufficient. As a result, the test range of the instrument will be reduced. When the resistance of the test leads is increased, the total value of R in the following equation will also increase.
P = I 2R where
R = (resistance of load) + (resistance of test leads)
P = output power of the test instrument
I = output current of the test instrument
Since the maximum power output ( P ) of the test equipment cannot change,
Optimum conditions (Figure 10)
Figure 9: Wind Turbine Blade before Installation
Table 1: Resistance Range for Varying Test Current Magnitudes for a Popular Low-Resistance Tester
the rise in test lead resistance will cause the maximum current ( I) to be reduced. Table 1 shows how lead length impacts the ability of an instrument to measure low resistances. It is clear that accurate and repeatable measurements will be a combination of test current, lead length, and resolution.
As seen in Figure 10, the performance of the low-resistance tester at 1 A (2.5 W) was most desirable for lead lengths that are typically employed to measure wind turbine LPS. For wind turbine applications, it is important to utilize the proper range and test current magnitude because it will be imperative for the length of measurement leads to accommodate the length of the wind turbines blades.
RESULTS
Testing the lightning protection system was performed on a wind turbine with 32-m-long (105-ft) blades using a low-resistance ohmmeter. The instrument was used in its long-test-lead mode, which applies a 1 A test current and can measure accurately down to 0.01 mΩ when using 100-m-long (330-ft) test leads. The lightning system testing consisted of measuring the system’s resistance from the tip of each blade to the hub and from the hub to the base. The lightning system terminates with interconnected ground rods at the base of the turbine tower.
Each measurement was taken three times to evaluate repeatability. The variance meter on the instrument automatically recorded three measurements in a row and calculated their variance. The raw measurements of this test can be seen in Table 2; total results are shown in Table 3.
The low variance provides confidence in the measurement. In the field, test engineers must take every care to remain safe and follow best practices. This will provide the best possible measurements.
The manufacturer of this wind turbine provided a pass level for the lightning system of 20 mΩ or less. This test proves that the lightning system has been installed correctly and is in good working order. Therefore, this turbine has good lightning protection as per the manufacturer’s design.
CONCLUSION
Lightning is a hugely damaging threat to wind turbines, and as wind power installations continue spreading across the world, the
Figure 10: Optimum Testing Parameters with 1 A Test Current and Long Leads
Table 2: Raw Measurements, Variance, and Averages
Table 3: Total Resistance Values and Results
requirement to protect these assets becomes more important.
Manufacturers of wind turbines take great care in designing the lightning protection system because of the known damage that can be caused. Owners and operators of turbines must ensure that the lightning protection system has been installed correctly. Additionally, owners and operators must regularly check the lightning protection system as part of the maintenance program.
Testing and verifying the lightning protection system is based primarily on low-resistance measurements. There are some challenges to measuring resistances at milliohm level when dealing with large structures like a wind turbine, so a balance between test energy, accuracy, resolution, and test lead length must be established. However, the right tools for the task will make it a simple job.
It is highly recommended to make lightning protection maintenance a key regular task for owners and operators. This will avoid lightning damage to wind turbines and ensure these assets are protected.
REFERENCES
Dehn International. “Lightning and Surge Protection for Wind Turbines,” 2015. [Online]. Available: https://www.dehn-usa. com/sites/default/files/uploads/dehn/pdf/whitepapers/ab-juli15/wp016-e-wind_turbines.pdf.
American Clean Power. “Wind Power Facts,” [Online]. Available: https://cleanpower.org/ facts/wind-power/.
Global Wind Energy Council. “Global Wind Report,” Global Wind Energy Council, Brussels, 2021.
Sameer Kulkarni, PE, is an Applications Engineer at Megger. He previously worked for Entergy at River Bend Nuclear Generating Station as Systems Engineer responsible for power distribution, large power transformers, and NERC. Sameer obtained his BS in Mumbai, India, and graduated with an MS in electrical engineering from Arizona State University. He obtained his Professional Engineer license in June 2019 and is an IEEE Member.
Dr. Ahmed El-Rasheed is a Business Development Director at Megger and has over 14 years’ experience in electrical engineering. He is a member of several international standards organizations and has published papers on ground testing, insulation testing, and multi-sensor integration using AI.
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APPLYING NFPA 70E AND CSA Z462 TO RENEWABLE ENERGY POWER GENERATION
BY TERRY BECKER, P.ENG., CESCP, TW Becker Electrical Safety Consulting Inc.
The growth in renewable energy power generation will continue into the future. What has been lacking is focus on the electrical hazards in construction and fabrication, commissioning, operation, and maintenance. However, requirements in NFPA 70E, Standard for Electrical Safety in the Workplace and CSA Z462, Workplace electrical safety Standard do apply to renewable power generation.
ARC FLASH AND SHOCK HAZARDS IN RENEWABLE POWER GENERATION
Renewable power generation is not new technology. It has been adopted in Canada, the United States, and globally for decades.
• A strong installed base exists in wind turbine power generation and large commercial solar power farms, and with new battery technology, largescale battery storage will begin to be installed.
• Large-scale solar power generation development (e.g. 100 MW, 500 MW, 1,000MW, or larger) has lagged wind turbine power generation, but has accelerated in the last three to five years.
• Installation of large-scale battery storage systems is relatively new and will experience significant growth.
In Canada, according to Natural Resources Canada — in addition to wind and solar power growth — development of other renewable power generation including hydro, solid biomass, ethanol, renewable municipal waste/landfill gas, biodiesel, and tidal has also accelerated in the last 15 to 20 years.
Additionally, technological development and competition in battery technology has resulted in lower prices and greater capacity. This is expected to result in accelerated growth in adoption.
The development growth has come with the additional exposure of construction and fabrication, commissioning, operation, and
maintenance workers to the electrical hazards of arc flash and shock from working on both low- and high-voltage electrical equipment.
NFPA AND CSA STANDARDS
NFPA 70E and CSA Z462 have been adopted across the USA and Canada by industrial, commercial, and institutional business sectors as the industry’s best practices for the development and implementation of policies, practices, and procedural requirements for electrical safety and the effective management of arc flash and shock hazards. The adoption
and application of NFPA 70E and CSA Z462 to renewable energy power generation would be considered good due diligence to applicable OSHA and provincial or territorial occupational health and safety regulations.
The 12th Edition of NFPA 70E published in September 2020 included a new Battery Risk Assessment method (Figure 1) for work on batteries in Annex F Risk Assessment and Risk Control, F.7, and Figure F.7: Assessing Hazards Associated with Work on Batteries. CSA Z462 published its 5 th Edition in January 2021; it does not include this flow chart related to batteries.
Notes:
1. Arc flash and shock PPE may be required to put the batter y in a segmented state The batter y must also be isolated from the system.
2. This only applies if the technician cannot reasonably reach across more than 100 volts or if the exposed par ts are protected so the technician cannot touch across more than 100 volts.
3. If the batter y ter minals are more than 6 ft apar t, or if at least one of the ter minals is protected, arc flash hazard PPE is not required with respect to the batter y ter minal risk
4. There may be additional procedures that can be implemented that would fur ther reduce the arc hazard risk and required PPE.
Figure 1: Annex F, Figure F.7: Assessing Hazards Associated with Work on Batteries
As defined by the Canadian Electrical Code and the National Electrical Code, low-voltage (≤1,000 V) and high-voltage (≥1,001 V) power generation is installed. Solar power generation occurs at DC voltages that are considered highvoltage: 1,500 VDC. In its 2021 Edition, CSA Z462 will apply to electrical equipment with a voltage greater than 30 V AC or 60 V DC (CSA Z462, 2021 Edition, Clause 4.1.6.2.3), while NFPA 70E still retains a 50 V AC or DC low-voltage threshold.
The NFPA 70E and CSA Z462 standards are based on work tasks and are 100% focused on risk assessment. Specific, defined worktask descriptions can be found in NFPA 70E
Table 130.5(C) or CSA Z462 Table 2 for both AC and DC low- and high-voltage electrical equipment. Table 1 highlights some of the work tasks that would normally be performed related to construction and fabrication, commissioning, operation, and maintenance of renewable power generation.
Significant electric shock and arc flash hazard exposure is related to isolation and any diagnostics or troubleshooting work tasks related to renewable energy power generation.
During the construction of renewable energy power generation facilities, tasks related to commissioning the power distribution system
Table 1: Energized Work Tasks Applicable to Renewable Power Generation
Task Description
1 For AC systems, work on energized electrical conductors and circuit parts, including electrical testing
2 Operation of a circuit breaker or disconnect switch the first time after installation or completion of maintenance in the equipment
3 Operation of a circuit breaker or switch that is not in a normal equipment condition
4 For DC systems, working on energized electrical conductors and circuit parts of series-connected battery cells, including electrical testing
5 Opening hinged door(s) or cover(s) or removal of bolted covers (to expose bare, energized electrical conductors and circuit parts) including bolted covers, such as battery terminal covers for DC systems
6 Working on control circuits with exposed energized electrical conductors and circuit parts, greater than 120 V
7 Insertion or removal (racking) of circuit breakers or starters from cubicles, doors open or closed
8 Insertion or removal of connector covers or battery intercell connector(s)
9 For DC systems, working on exposed energized electrical conductors and circuit parts of utilization equipment directly supplied by a DC source
10 Opening voltage transformer or control power transformer compartments
11 Operation of outdoor disconnect switch (hook-stick operated)
12 Operation of outdoor disconnect switch (gang operated, from grade)
13 Operation of a circuit breaker, switch, contactor, or starter
14 Voltage testing on individual battery cells or individual multi-cell units
15 Removal or installation of equipment covers such as wireways, junction boxes, and cable trays that does not expose bare, energized electrical conductors, and circuit parts
16 Opening a panel-board hinged door or cover to access dead front overcurrent devices
17 Removal of battery nonconductive intercell connector covers.
18 Maintenance and testing of individual battery cells or individual multi-cell units in an open rack
19 Insertion or removal of individual cells or multi-cell units of a battery system in an open rack
SOURCE: WORK TASKS LISTED ARE EXCERPTED FROM NFPA 70E TABLE 130.5(C) OR CSA Z462 TABLE 2, ESTIMATE OF THE LIKELIHOOD OF OCCURRENCE OF AN ARC FLASH INCIDENT FOR AC AND DC SYSTEMS.
will expose qualified persons to the electrical hazards of arc flash and shock. Following commissioning, ongoing operation and electrical equipment maintenance will expose operations and maintenance employees or contractors to the electrical hazards of arc flash and shock. Renewable power generation also includes construction of additional overhead power lines for distribution and transmission with related outdoor high-voltage substations, and this energized electrical equipment poses a significant shock and electrocution hazard and arc flash.
SEQUELA EFFECTS OF ELECTRICAL SHOCK
The electrical shock hazard has been neglected. Electrical workers have accepted being shocked
as part of the job — a right-of-passage, a badge of honor — and they may not even be aware of the long-term sequela health effects of receiving multiple low-voltage electrical shocks and how it may have impacted them. Currently, two facilities are formally recognized for formal research and treatment: the St. Johns Rehab Centre, Electrical Injury Program in Canada and the University of Chicago, Chicago Electrical Trauma Rehabilitation Institute (CETRI) in the United States.
When a worker is exposed to electric shock hazard, there are two possible outcomes:
1. A shock is received, and the worker survives.
2. Or they die.
Electrical incident statistics confirm that fatal electrical injuries from shock occur at an alarming rate — on average still once a day or more in North America. What is not published in electrical incident statistic reports is the number of electrical workers who suffer from the long-term effects of receiving multiple lowvoltage (<1,000V) shocks. The medical term for this is “sequela.”
A sequela is a pathological condition resulting from a disease, injury, therapy, or other trauma. Typically, a sequela is a chronic condition that is a complication which follows a more acute condition. It is different from, but is a consequence of, the first condition. SOURCE: WIKIPEDIA
Short-Term Effects
We know the short-term effects of receiving an electric shock. As noted above, you survive the electric shock or you die. Table 2 lists the short-term immediate effects of receiving — but surviving — an electric shock.
The amount of current, the current flow path through the human body, and the frequency and length of time the current flows through the human body determines the probability of heart fibrillation. Male and female body resistance will be different, and added muscle mass increases conductivity. Wet or dry skin at the point of current entry will also impact current flow, and the number of times an
electric shock is received impacts the long-term effects and possibly sequelae.
Long-Term Effects
If you are an electrical worker reading this article, you may have long-term sequelae effects from been shocked multiple times throughout your career at 120 VAC, 208 VAC, 240 VAC, 277 VAC, 347 VAC, 480 VAC, or 600 VAC. If you have some of the symptoms listed in this article, you may want to follow up with your family physician. The potential long-term sequela effects from receiving multiple, lowvoltage electric shocks include psychological, neurologic, or physical symptoms.
• Psychological Symptoms. Behaviour changes and attention span issues. You may be irritable, get frustrated, experience anger, and may be physically aggressive. You may experience depression and posttraumatic stress disorder depending on whether you experienced “no-letgo” or became unconscious due to the shock exposure. Other sequelae include insomnia, anxiety, fear of electricity, panic attacks, guilt, and moodiness.
• Neurological Symptoms. You may experience memory loss, numbness, headaches, chronic pain, poor concentration, carpal tunnel, seizure disorders, dizziness, tinnitus, and tremors.
4 amps Heart paralysis threshold Heart stop for duration of current flow
5 amps or greater Tissue burns
Most likely fatal; vital organs are burned or damaged; can lead to amputation of limbs
Table 2: Immediate Effects of Electrical Current Flow through the Human Body
• Physical Symptoms. Generalized pain, fatigue, exhaustion, reduced range of motion, contracture, night sweats, fever, chills, or joint stiffness may be experienced.
The effects listed can change or may be more severe depending on whether the shock was a momentary contact or resulted in no-let-go, the path the current flowed through the body, and the duration and amount of current.
John Knoll’s Story
John Knoll is a Master Electrician, and a Professional Electrical Contractor (PEC) with the Electrical Contractors Association of Alberta (ECAA) and resides in Edmonton, Alberta, Canada. John is currently not working in the trade and is suffering from sequalae related to receiving multiple low-voltage shocks while at work starting when he was an apprentice and continuing while he was a journeyman electrician. John worked in the non-unionized side of the trade for most of his apprenticeship and career. He told me, “As an apprentice trimming out lighting circuits in apartments, we played games about being shocked at 120 VAC. We were not taught to fear electricity or respect it. I was never concerned about 120 VAC, 240 VAC. I didn’t consider it an issue to receive those shocks. I always said I would rather receive one knowing it was coming than not knowing. So after tick testing, we would touch the wires, because sometimes the tick tester lied, and it was better to know it was coming. It was the most we were able to do most times not being supplied the proper PPE or training to do our duties.”
The story of John’s career is very common. John started in the electrical trade in 2005 and worked on energized 120/240 VAC singlephase and three-phase 208 VAC panelboards as an apprentice. He received shocks as early as the first week in the trade. John states, “I was probably shocked up to 500 times,” and I have talked to other electricians who say they were shocked hundreds of times during their career. John explains, “The electricians I worked with
when I was an apprentice never identified the hazards and long-term effects of electric shock. There was no formal training, and no personal protective equipment was provided. If we wanted a tick tester, we had to buy it ourselves. ‘Live’ work was not questioned. We had to work energized because we couldn’t deenergize parts of the job. We cut in panels while energized and rarely could turn off the power, as it impacted the other trades. I didn’t receive any training on lockout until I worked the last few months of my fourth period in the Union.”
John’s perception of shock and his sequela changed when he was shocked at 347 VAC. “That shock was different,” he says. “I was held and could not let go. I knew I was going to die, and I had no control of my body. I was saved by gravity when I fell off my ladder. I thought I was dying; the pain was unbelievable as I lost the ability to breathe. At that point,” John says, “I had a new-found respect and fear of electricity.”
In John’s case, he experienced psychological, neurological, and physical symptoms he did not know could be attributed to receiving multiple, low-voltage shocks throughout his career. When John described his injuries, I found it unbelievable, but based on information published more than 10 years ago by Dr. Joel Fish, who at the time was practicing at St. Johns Rehab Centre in Ontario, the longterm sequela effects of electric shock are real.
John moved on in his career and had his own company from 2010 until he could no longer work due to escalation of his symptoms. He believes he began experiencing symptoms as early as two years into the trade and began seeking chiropractic and massage care — known relief for the nerve pain caused by the long-term sequelae effects of electric shock. In 2016, his life began to change rapidly, and looking back now, he knows the multiple electrical shocks he received led to deterioration in his mental and physical health and directly impacted his personal life, as he was divorced from his wife and had issues with his friend and business partner.
FEATURE
ELECTRICAL SHOCK RISK FACTORS
Those working in the electrical industry identified many sociocultural, environmental, and behavioral factors that lead to electric shock.
Societal
These may include environmental factors, federal, provincial or municipal laws and policies
Bad weather (i.e. rain)
Working at heights
Sectoral
These may include cultural values and/or safety norms
Time pressure (trying to work quickly)
Competitive pricing strategies (trying to cut costs)
Organizational
These may include environment, equipment and/or culture
Poor training in electrical safety and risk
Faulty equipment
Interpersonal
These may include coworkers, family, supervisor and/or friends
Rely on others to ensure equipment is de-energized
Miscommunication
Other trades working on site
Interruptions and distractions
Individual
These may include knowledge, attitudes and/or skills
Poor work practice/ complacency
There are consequences of refusing or declining to work on energized equipment.
told not to bring things up again in the future if they felt unsafe
John’s comments about working on energized conductors and circuit parts were and perhaps still are the norm in the industry. In fact, his comments align with the results of a shock research project completed by the British Columbia, Canada, Technical Safety British Columbia (TSBC). In February 2019, the TSBC published a report related to shock hazard in “Negotiating Safety – Understanding the Behavioral and Sociocultural Factors Related to Electric Shock.” Based on interviews and surveys, the report categorized the reasons
Figure 2: TSBC Risks and Consequences of Electrical Shock Infographic SOURCE: TECHNICAL SAFETY BRITISH COLUMBIA
electricians have worked and continue to work energized: societal, sectoral, organizational, interpersonal, and individual (Figure 2). The report concluded that poor training, poor work practices, complacency, not refusing to work energized, “I thought someone else had turned off the power,” and peer pressure (e.g. loss of job, keep the boss happy, rebuked by other workers) influenced why working energized was never questioned.
I believe John’s story is not an isolated case. There are hundreds, potentially thousands, of electricians in Canada, the United States, and internationally who have long-term sequelae and have not correlated them to receiving multiple, low-voltage shocks throughout their careers. The psychological, neurological and physical health issues, the impacts on families, and the potential impact of not continuing in the trade with its resulting financial impacts are significant. If you are an electrician and are experiencing symptoms listed in this article, they can most likely be attributed to receiving multiple, low-voltage electric shocks while working. A big shout out and “thank you” to John Knoll for sharing his story, emotions, drive, and entrepreneurial spirit.
The bottom line is that electrical workers have been shocked as a normal condition of doing their jobs with a complete lack of awareness of the potential long-term effects of receiving multiple, low-voltage shocks throughout their careers. From 1942–1960, the American Electricians’ Handbook taught electricians that the human body could be used to detect voltages up to 250 VAC by touching with the hands. The chapter on Measuring, Testing, and Instruments said, “Electricians often test circuits for the presence of voltage by touching the conductors with the fingers. The presence of low voltages can be determined with tasting.”
Yes, there have been changes in the last decade in Canada with the publication of CSA Z462, Workplace electrical safety Standard in 2009. NFPA 70E, Standard for Electrical Safety in
the Workplace, first published in 1979, has also made a difference, but the focus has been on arc flash and not shock. For the future, shock needs to be a priority!
APPLYING NFPA 70E AND CSA Z462
As noted previously, the NFPA 70E or CSA Z462 standards are work-task-based. The next consideration is the voltage of the electrical equipment the work task will be completed on and the condition of maintenance of the electrical equipment. NFPA 70E and CSA Z462 require a risk assessment procedure to be implemented for defined “jobs” that would include the execution of a single or multiple work tasks. Two separate risk assessments are completed underneath the job’s risk assessment procedure for each work task: a shock risk assessment and an arc flash risk assessment.
Based on the work tasks listed in Table 1, construction/fabrication, commissioning, operation, and maintenance of renewable energy power generation require effective hazard identification and risk assessments to be completed for “jobs” that may include the work tasks listed.
CONCLUSION
The requirements of NFPA 70E , Standard for Electrical Safety in the Workplace and CSA Z462, Workplace electrical safety Standard do apply to energized electrical equipment related to renewable power generation.
REFERENCES
Marni L. Wesner, MD, MA, FCFP, DipSportMed, and Dr. John Hickie, MD, MSc, CCFP, CCBOM. “Long-Term Sequelae of Electrical Injury.” Canadian Family Physician, CFP-MFC, Official Publication of The College of Family Physicians of Canada, September 2013. Online: https://www.ncbi.nlm.nih.gov/pmc/ articles/PMC3771718/.
FEATURE
Clifford C. Carr, EE, PE. American Electricians’ Handbook, Fifth Edition, Tyrell Croft Consulting Engineers. McGraw-Hill Book Company, Inc., 1942.
Technical Safety British Columbia (TSBC). “Safety Stories: Electric Shock.” Online: https://www.technicalsafetybc.ca/State-ofSafety-2018/safety-stories/electric-shock.
St John’s Rehab Centre. Electrical Injury Program. Online: https://sunnybrook.ca/ content/?page=sjr-patvis-prog-electrical
University of Chicago, Chicago Electrical Trauma Injury Institute. Online: https:// en.wikipedia.org/wiki/Chicago_Electrical_ Trauma_Rehabilitation_Institute.
Government of Canada. Online: https:// nrcan.gc.ca/science-data/data-analysis/energydata-analysis/energy-acts/renewable-energyfacts/20069.
Terry Becker, P.Eng., CESCP, IEEE Senior Member, is an Electrical Safety Specialist and Management Consultant. He is the first past Vice-Chair of CSA Z462, Workplace electrical safety Standard Technical Committee and currently a Voting Member and Clause 4.1 and Annexes Working Group Leader. Terry is also a Voting Member on CSA Z463, Maintenance of electrical systems Standard and a Voting Member of IEEE Std. 1584, Guide for Performing for Arc-Flash Hazard Calculations. He has presented at conferences and workshops on electrical safety in Canada, the United States, India, and Australia, and is a Professional Engineer in the Provinces of British Columbia, Alberta, Saskatchewan, Manitoba, and Ontario.
Reliable Power System Solutions
In Remembrance: JAMES R. “JIM” WHITE
Foreword by RON WIDUP, Shermco Industries
On June 9, 2021, I received this text message from Vickie White, wife of Jim White:
Jim is free and home with God. June 9, 2021 @ 4:55 AM was his appointed time.
And that was that.
Jim the fighter, the guy who would never give up, the person you could always count on to help you out and volunteer to get things done, had gone home.
And though it wasn’t a surprise to any of us, it’s the finality of that statement that hits you. I saw Jim just two days earlier and was able to say goodbye to him, and more importantly, to say goodbye from all his electrical buddies. It is in that spirit that we honor our memories of Jim, in his favorite electrical industry journal, NETA World.
Jim’s career in the electrical field expanded across many decades with a specialty in training and education. His direct impact on the electrical worker in the field is immeasurable. With a passion for the practical and a common-sense approach to understanding the hazards of electricity,
Jim shared his knowledge with a unique style and dry-wit humor that was his trademark.
Who knows what the impact of Jim’s contributions are to the industry? Did he prevent significant injury or save lives because of it? My guess is he did. And did he make all of us better at what we do? Most definitely.
We could spend many hours on Jim stories, and we should continue to do that when we come together again in future conferences and meetings. One thing for sure: We are better people for having known and spent time with him. We will miss him dearly.
James Roy White was born December 12, 1951, in Washington, DC, to parents Benjamin and Katherine White. He was the middle son, born between brothers Ben Jr. and David.
Jim grew up in Cottage City, Maryland, and attended Bladensburg High School. In 1968, he began work as a journeyman electrician. This was the beginning of Jim’s auspicious career in the electrical industry.
In 1970 at the age of 19, Jim enlisted in the Air Force where he served as a jet mechanic in Korea during the Vietnam War. After a fouryear stint, Jim returned home and worked as a high-voltage electrician for the U.S. government.
It was during that time he met the love of his life, Vickie Ford. They were married two years later and raised a family comprised of a
daughter and two sons. Everyone knew that with Jim, family always came first.
Jim enjoyed golf, restoring old cars (mostly Corvettes), and very early morning workouts at a local gym. He was a member of the National Corvette Restorers Society for 20 years, earning Master Judge recognition for judging restored vintage Corvettes.
Jim leaves behind his beloved wife Vickie, daughter Jodie, son Jason and his wife Christina, son Justin and his wife Allison, granddaughter Kristen, and three grandsons Caden, Connor, and Anthony.
JAMES R. “JIM” WHITE
Jim’s Air Force Days
Vickie and Jim White
AN OUTPOURING OF LOVE AND RESPECT FOR
Jim White
Generosity of spirit is the phrase that comes to mind when I think of Jim. He gave freely to all around him, educating us through his knowledge and expertise and passion for the industry. He genuinely cared about making the electrical power industry a safer place for everyone in it. — Kristen Schmidt
Jim was one of the most well-respected technical and safety professionals in the industry. He will be greatly missed. — NETA President Eric Beckman
I remember a few times when conversations were tense while debating this or that in a meeting. Jim would always retort with something from a different perspective, or he would say something completely off the wall and make us all laugh. We are safer at work because of his efforts, but more than that, we are better human beings because we knew Jim. — Kiley Taylor
Jim was a wealth of knowledge. I thought I had a lot of knowledge myself and was enjoying some good conversation with other members during a task group breakout. Jim put me back in my place with a good comment about something I said: “That sounds great, but how does it help us address this issue?” He always made you think about solving the real problems at hand. — Karl Cunningham
While others may remember Jim for his hard work, technical expertise, and industry knowledge, I will always remember Jim as a leader who faced great adversity, and despite these tremendous challenges, set an example for us all. Jim’s courage and faith are an inspiration. — Bill Mohl
Jim always impressed me as a straightshooter and a gentleman — a person of integrity and empathy, as well of deep expertise and knowledge of his field. He could offer you a dissenting opinion and bring you to his side of seeing things without even the hint of disagreement. — Marcelo Valdes
Jim is in a new oversight role now. — Martin Nagel
Jim was the consummate professional, guru on electrical safety, and a downright great person. His loss creates an unfillable void and emptiness in the hearts of all who had the privilege of knowing him. — Tom Bishop
I will remember Jim for his dedication to his craft, his dedication to the NFPA community and codes and standards, and his dedication to safety — always looking out for the small guy. — Larry Ayer
A PROLIFIC CAREER
During his career, Jim became an industry leader in electrical safe work practices and technical training. An NFPA Certified Electrical Safety Compliance Professional and a NETA Level 4 Senior Technician, Jim was NETA’s principal member and current secretary of NFPA Technical Committee NFPA 70E®, Electrical Safety in the Workplace for nearly 20 years. Louis Barrios served with Jim on the 70E Committee. “Jim White continued his commitment to our safety community until the very end. I’ll never forget one of his last presentations at the IEEE ESW, where he drove himself up to the podium in a small scooter and stood and delivered his presentation. What a fighter!”
“Jim had a special way of cutting through what can sometimes be very complex messages and getting to the practical point with a unique wit,” Barrios continues. “He was a real champion of electrical safety.”
Jim was also NETA’s principal representative on National Electrical Code® Code-Making Panel (CMP) 13 and represented NETA on ASTM International Technical Committee F18, Electrical Protective Equipment for Workers.
Jim was Shermco Industries’ principal member on NFPA Technical Committee for NFPA 70B,
Recommended Practice for Electrical Equipment Maintenance. “He was a straight-shooting, tellit-like-it-is guy, a true champion of electrical safety, and a friend,” says Rod West, who worked alongside Jim on the 70B Committee.
Jim also represented AWEA on ANSI/ISEA Standard 203, Secondary Single-Use Flame Resistant Protective Clothing for Use Over Primary Flame Resistant Protective Clothing. Jim was Chairman of the IEEE Electrical Safety Workshop in 2008, was Vice-Chair of the IEEE IAS/PCIC Safety Subcommittee, and was an active member on many advisory boards. Additionally, Jim authored two technical books and many articles for industry publications. He was a regular contributor to NETA World for well over two decades and was an active presenter/lecturer at NETA’s PowerTest and many other venues.
“Jim will be sorely missed within the electrical and NETA communities,” says Scott Blizard, a recent past-President of the NETA Board of Directors. “The industry lost a man who made a huge impact on the world,” adds Missy Richard, NETA Executive Director.
Daryld Ray Crow co-presented technical classes and papers with Jim over the course of many years. “I enjoyed helping Jim with the question-
REMEMBRANCE: JAMES R. “JIM” WHITE
New Corvette 2012
and-answer sessions on NFPA 70E that he led at NETA’s safety conferences,” recalls Crow. “I could always count on his help when needed. Jim was a true mentor to many people.”
Jim was well-respected in the industry, and he received much recognition and many industry awards for his technical expertise, vast industrial experience, and leadership. An IEEE Senior Member, he received the IEEE/ IAS/PCIC Electrical Safety Excellence Award in 2011 and NETA’s Outstanding Achievement Award in 2013.
“I had the opportunity to meet many players in the codes and standards industry over the years, but there is only one Jim White,” says colleague Jim Dollard. “He was respectful, compassionate, humble, kind, and funny as hell. In many cases, his dry sense of humor made tense meetings seem jovial. We are all better people for having known and spent time with him.”
Jim’s contributions to electrical codes and standards will live on, making workplaces safer and saving the lives of men and women who never knew him.
“While we all recognize his passion for everything he was involved in, his ongoing dedication to NFPA 70E and PowerTest — and more recently, the conversion of NFPA 70B from a recommended practice to a standard — was determined and energetic,” says Palmer Hickman. “He continued to participate at the highest level when most would have retreated and given up. Overcoming adversity and giving it his all is what we all will fondly remember of Jim.”
To watch Jim’s June 28th service, go to https://www.dropbox.com/s/pwv8mthr4itmh4b/Jim%20 White%20Memorial%20%286-26-21%29.mp4.
Jim presented at many industry events.
Tony Demaria and Jim Cutting Up
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Conventional testing of medium- and high-voltage circuit breakers (MV/ HV CBs) involves measuring the timing and travel of the main contacts and their corresponding resistors (pre- or post-insertion) if any, along with the current profile of the operating coils, and occasionally the timing of auxiliary contacts.
This article explains several techniques available to improve or extend the scope of testing. Aspects reviewed include improving the safety and efficiency of conventional practices, testing circuit breakers that are normally not tested due to the difficulty they present, and using additional or alternative testing techniques to assess specific circuit breaker components.
Circuit breaker analyzers (CBAs) are versatile instruments that can be used to extend testing capabilities beyond conventional testing to achieve better or focused assessment of circuit breakers depending on their application or criticality — all by simply adding accessories. This article provides insight into techniques that can be implemented and the advantages of adding them to a maintenance plan.
CONVENTIONAL CB TESTING
MV/HV CBs are installed in systems above 1 kV with various insulating media: air magnetic blast, vacuum, oil (low and bulk volume),
SF6, or new insulating gases developed by CB manufacturers. Vacuum is the most common for MV CBs and SF6 for HV CBs. The mechanism that drives operation of the breaker is commonly spring-based, but pneumatics and hydraulics are also used. Magnetic mechanisms are currently common on MV vacuum CBs. Depending on size and application, the breaker may have one or three mechanisms:
(1) One single mechanism for the three phases, commonly known as three-pole operated
(2) One mechanism per phase, known as single pole or independent pole operated (IPO)
A circuit breaker isolates the source from the load when it is in open position as well as any side from ground under any circumstance. Insulation tests, such as insulation resistance, power factor, vacuum bottle integrity, or gas analysis, are required to assess the condition of the insulation.
When the breaker is closed, it should provide continuity to the circuit with extremely low impedance to avoid losses and consequent heat that deteriorates the contacts and can cause catastrophic failure of the breaker. A contact resistance test is used to determine whether the contacts are within specs. High values from the reference or elevated differences between the contacts are indication of wear, contamination, or looseness of the contacts.
The third main function of a circuit breaker is to act as a switch for operational maneuvers or protection against faults in the system. MV and HV circuit breakers rely on external commands to operate under protection conditions. External commands are applied to a control
circuit, which in turn uses coils and contacts to actuate the mechanical or electrical restrain to release the energy stored in the mechanism to close or open the breaker. The breaker should also be capable of opening correctly immediately after closing in cases where the breaker is closed under an existing fault; this function is called close-open or trip-free. In other instances depending on the system and the type of breaker, the breaker should be able to open and close after a certain delay to act as a recloser. If the fault persists, the breaker should open again immediately. These operations are called open-close and open-close-open.
All of these operating characteristics are included in manufacturer specifications and
INDUSTRY TOPICS
should be within certain timing and travel parameters. They can therefore be verified with a test that simulates the external commands to the control coils, measures the operating times of main and resistive contacts, calculates synchronism of the poles, and characterizes mechanical behavior by plotting the travel curve and calculating the speed, acceleration, rebounds, stroke, and penetration, among others. This comprehensive test, called timing and travel analysis, is performed with a circuit breaker analyzer (CBA) and the appropriate transducers.
CIRCUIT BREAKER ANALYZER
In a very simplified description, a CBA is a test instrument that simulates the operating pulses from relay and control systems by closing a contact in a control module to initiate a timer and operation of the breaker. Simultaneously, another set of modules or channels are activated to measure different parameters. These modules operate with analog or digital signals.
One module is dedicated to simulating the operating signals. Other modules are dedicated to measure:
• Timing of the main contacts by applying voltage to each pole and detecting the make- or-break by measuring current circulation or interruption, in essence a continuity measurement. Resistor contacts (pre- and post-insertion) timing is measured the same way and includes measurement of the resistance.
• Timing of auxiliary contacts using a similar concept of continuity measurement.
• Travel of the breaker mechanisms through analog or digital channels and the usage of the corresponding transducers mechanically attached to a specific point of the circuit breaker drive. The module measures the analog or digital signals for the entire operating period and converts the information to
travel parameters (length, angle, speed) using manufacturer conversion factors or tables. Results are displayed numerically and graphically to show the behavior of the mechanism throughout the entire operating time.
The analog channels of a CBA can be used to measure signals from various accessories. This allows the instrument to be used for the following tests, thus expanding the usage of a CBA as a comprehensive and efficient tool.
Dual Ground Testing
The conventional timing method requires the breaker to be isolated from ground at least from one side. Even though the circuit breaker under test is isolated from high voltages and grounded on one side, three main possibilities still exist for the breaker to become energized to a dangerous high potential:
1. Accidental energization of the line from some unwanted source of potential
2. A lightning strike on the lines or bus connected to the circuit breaker
3. Most common, capacitive coupling from another conductor that is energized. The voltage from capacitive coupling can sometimes generate 20 mA or more of current that can be pushed through a human body.
To minimize the safety hazard, the common practice is to ground both ends and only remove one of the grounds for the testing operations. When the timing equipment is connected to the circuit breaker under test, it provides a direct path to the technician for this capacitive-coupled current. Timing equipment should always be grounded while testing in a substation, but the induced current will still flow through the equipment to ground as seen in Figure 1
If the ground fails or the technician inadvertently removes one of the timing leads
from equipment, the technician is now the easiest path to ground, and the induced current will flow through the technician. When the circuit breaker is grounded on both sides as in Figure 2, the induced current flows directly to ground and not through the test equipment or test technician.
The added step of disconnecting the ground to test and reconnecting it to complete the setup and return the CB to service adds extra time to the procedure, which can represent one or two extra hours to complete the testing depending on the size of the breaker and internal company practices. Additionally, safety is compromised as was shown in Figure 1 while the tests are conducted. Some international standards, including IEC EN 50110-1, require working on components in high-voltage environments only when both sides are grounded.
CBA analyzer manufacturers have implemented techniques to be able to time breakers with both ends grounded, and utilities are gradually implementing them in their procedures due to the benefits of increased safety and reduced outage time.
DCM Testing
One leading technique uses dynamic capacitance measurement (DCM), which relies on the natural capacitance of the circuit breaker to distinguish between closed and open states. A simple representation of a circuit breaker (Figure 3) consists of a moving contact and a stationary contact separated by some type of insulating medium, commonly vacuum, oil, or SF6 gas, i.e. the circuit breaker is a capacitor.
By placing a variable frequency generator in parallel with the circuit breaker, an LRC circuit is formed. The inductance and resistance is composed mainly of the leads connecting the frequency generator to the circuit breaker and the ground leads; the capacitance is from the circuit breaker itself.
One side grounded
One side grounded
High voltage
High voltage
Up to several kV if not earthed (grounded)
Up to several kV if not earthed (grounded)
capacitive coupled current capacitive coupled current
capacitive
capacitive coupled current
Test equipment
Test equipment
Grounding
Grounding
Station earth (ground)
Station earth (ground)
Both sides grounded
Both sides grounded
High voltage
High voltage
Up to several kV if not earthed (grounded)
Up to several kV if not earthed (grounded)
Grounding
Grounding
Grounding
Grounding
Station earth (ground)
Station earth (ground)
Measuring the dynamic capacitance allows the maximum capacitance value for each contact to be determined. This happens when the contacts have the minimal separation before the make of the contacts. The moment of this maximum capacitance is used to start and/or stop the timer to measure the breaker operating times.
Figure 1: CB with One Side Grounded for Testing
Figure 2: CB with Both Sides Grounded for Testing
Figure 4 includes two graphs of current vs. frequency — each with its own resonance point. When the circuit breaker is in the closed position, frequency varies between 150 kHz to 2 MHz to establish a minimum current response, at which point the frequency is locked into this position. When the circuit breaker is operated, the test current is continuously monitored at a high frequency (typically 40 kHz). When the contacts first separate upon opening, or right before they first touch on closing, the capacitance in the circuit is at maximum, and the resonance point shifts from the established minimum recorded while the circuit breaker was closed. As stated previously, if a timer records from close or trip coil energization to this shift in current response, accurate contact times per IEEE Std. C37.09 and IEC Std 62271-100 are recorded.
Figure 3: RLC Model of a Circuit Breaker and DCM Test Setup
Resonance frequency is determined and locked while CB is in closed
A CBA with the ability to operate with a DCM accessory allows a breaker to be tested more safely and efficiently, totally immune to 50/60 Hz interference, and with the added advantage of displaying the results in the conventional timing format.
Resonance frequency is determined and locked while CB is in closed position
Dynamic Resistance Measurement (DRM)
Resonance changes at contact separation with addition of serial capacitance
Resonance changes at contact separation with addition of serial capacitance
Figure 4: Current vs. Frequency for Contacts Closed and Contact Separation
This testing technique monitors contact resistance by circulating a DC current and measuring the voltage drop across the contacts of the breaker while it is opened or closed. The purpose is to plot the resistance rather than obtaining a specific contact resistance magnitude. This plot depicts the condition of the surfaces of the contacts and the various sections along the travel of the moving contact over the fixed contact.
The typical DRM response of the open operation of a breaker with arcing contacts (Figure 5) shows a flat line during the first milliseconds, then a slight increase in resistance as the moving contact begins to travel towards the open position. Then, when the main contact opens and the swipe continues over the arcing contact, the plot reflects this transition with a resistance spike followed by a second horizontal response with higher magnitude
for some milliseconds, trailed by a last spike in resistance to infinite when the moving contact parts from the fix side.
Arcing contacts are used to endure the deterioration caused by the arc from opening the breaker. The wear and tear caused by the arc reduces the length of the moving arcing contact to the point that it becomes ineffective and needs replacement. To determine when to replace the arcing contact, it is necessary to know the length of the moving contact. This can be estimated from manufacturer graphs that show the estimated number of operations under fault current, but since it is an estimate, it may trigger major maintenance activity only to find it is not due for replacement, or it is too late, and the main contacts are already affected.
As an optimal alternative, DRM can be used to reliably determine the length of the arcing contact. When travel measurement is added to the test, the separation between the two spikes in resistance, measured from the travel curve, represents the remaining length of the moving arcing contact. Furthermore, significant deterioration of the arcing contact such as erosion or contamination will be reflected in the graph with multiple and high variations in the resistance instead of a smooth and flat curve.
DRM works well with both sides of the breaker grounded and when the breaker opens. Instead of a spike to infinite, it will show a spike to a resistance of higher magnitude equivalent to the ground loop resistance. In this sense, the technique also offers increased safety, and in addition to assessing the arcing contacts, it may be used to estimate breaker timing. However, it is not as accurate because it relies on a resistance threshold that needs to be adjusted below the ground loop resistance and above the arcing contact resistance. Both limits are usually not higher than 10 milliohms, and the transition occurs in less than 10 ms. A threshold setting within such a small range is difficult, especially if the measurement is affected by induced AC currents from surrounding live conductors.
First Trip
Circuit breakers can be used for multiple applications, and in most of them, the common status or position is closed. Because they are used mainly for protection and temporary isolation, they will be in open position only for hours or days, while they remain in closed position for months or even years. Since their operation depends mainly on mechanical drives, latches, and their corresponding lubrication, the lack of exertion can degrade their ability to respond in a matter of milliseconds upon a protection or control command.
Think about two identical breakers for a period of two years with the same initial mechanical conditions but with different operating regimes. Breaker A operates occasionally in steady, mild environmental conditions. Breaker B, which is permanently closed, does not operate over the two-year period and is exposed to harsh environmental conditions, i.e. the four seasons, high humidity, and extreme temperatures. After the two-year period, the operating performance of these two breakers will be different. The lack of exertion and the effect of the environment on lubrication and components could have greater impact on the performance of Breaker B compared to the effect of wear and tear on Breaker A. Specifically, the very first open operation of
Figure 5: Typical Response of a DRM Test
Breaker B could be slower and is likely to be out of tolerance; however, subsequent operations during the testing process may not show this reduced performance. When called upon to open, a breaker only has one opportunity: that very first operation after being closed for a long time. It doesn’t matter if the performance improves with additional operations.
Any detriment in performance will be reflected in the current signature of the trip coil. Any problem in the control circuit or the latching system driven by the coil armature will change the magnitude of the current or the timing of the sequence of events prior to releasing the latch. Opening a breaker that has been closed for a long time in preparation for testing usually goes unmeasured, the reduced performance is unnoticed, and the maintenance test may not prescribe any maintenance activity, masking an underlying and developing issue in the breaker. It is easy to conclude that measuring this first operation provides revealing information about the condition of the breaker.
This test is called first trip and can be done using a CBA with added current clamps. The test consists of measuring the current signature of the trip coil — or coils if the breaker is an independent pole operated (IPO) breaker — at the first operation after being in the closed position for a long time. The setup needs to be done at the control cabinet while the breaker is in service, however the setup is simple: one current transformer per trip coil, connections to the DC voltage supply to
Figure 6: Setup to Measure First Trip
Figure 7: Setup to Measure First Trip
monitor the voltage while the breaker operates, and connection to the trip circuit to use it as a trig-in that starts the timer of the CBA (Figure 6). The measured signature is compared to a previous measurement, and the differences can determine whether there is a problem with the coil winding or armature, wiring or low-voltage issues, or problems in the trip latch or linkage system due to corrosion or lubrication issues.
The opening time of the CB can also be measured by monitoring the secondary side of the protection current transformers (Figure 7). In any case, extra caution must be taken since there are live DC circuits in the control cabinet, and the mechanism may be inside the same cabinet. In this test, there are no connections to the main terminals, and travel is not measured unless the transducer is permanently mounted.
The greatest benefit of using first trip testing is to test real-world operating conditions. It is a quick test that does not require an outage and can be used to determine and prioritize offline maintenance actions using a condition based approach.
Motor Current
A spring-charge motor is employed to compress or expand springs to store potential energy for close and open operations. Malfunctions of the charging drive can cause deviations in motor operation, which in turn will be reflected in the electrical current that circulates during its operation. If this current is monitored and trended, issues such as lack of lubrication or a broken or fatigued spring can be determined.
Normally, operation of the motor occurs after a close operation and takes between 10 and 30 seconds. Due to the duration of the operation, a separate close test is added to the breaker test plan to measure the current separately from the rest of the timing operations. For the measurement, the current is monitored by one of the CBA’s analog modules using a current sensor clamped around the motor power
supply. The power supply voltage is monitored by the control module.
The result will display the current graph along with parameters that characterize the motor voltage and current behavior such as motor running time and peak current ( Figure 8 ). Analyzing the results evaluates the current shape and ensures that maximum current and time for charging springs are not exceeded compared to manufacturer specs, commissioning, or historic results.
If the motor peak current is too high and/or motor charge time is too long, it could indicate that the charging mechanism requires more force than normal, e.g. due to lack of lubrication. Lower peak current and/or shorter motor charge time could indicate a broken or fatigued spring.
MV GIS Breaker Timing
Medium-voltage gas insulated switchgear poses a challenge when performing timing tests because the breaker is enclosed without any access to its terminals. Electrical access may be possible via cable terminal components, spare bays, or similar routes, but such access is limited to installation and commissioning phases. In the end, these options do not provide a practical option for routine or
Figure 8: Motor Current Measurement Result
troubleshooting testing activities, and the entire switchgear needs to be isolated to be able to test using the conventional timing technique.
An alternative is to connect a CBA to the voltage detection system (VDS) through an adapter to determine the operating time of the breaker by detecting the instant in which voltage appears or disappears when closing or opening the breaker, respectively, for each phase.
Other parameters, such as coil current and auxiliary contacts, can be recorded, and other testing techniques like first trip and motor current are fully applicable to this type of circuit breaker while using the VDS to perform the test. Figure 9 shows the basic test setup where the control module is used to measure control voltage and trigger signals. The adapter is connected to the VDS on one end and to the timing module on the other end.
Figure 10 compares the results of close and open operations under conventional and VDS methods.
This technique offers the ability to safely, efficiently, and accurately test breakers that are difficult to test with conventional techniques.
Figure 9: Basic Setup for VDS Testing
Figure 10: Close and Open Timing with Conventional and VDS Methods
CONCLUSION
A circuit breaker analyzer is a multifunction instrument that, with the appropriate accessories and adapters, allows conventional testing, complementary testing, advanced testing such as DRM and motor current, and alternative techniques such as DCM to improve safety and efficiency. First trip testing can be used to prioritize maintenance activities. Other uses of a CBA not covered in this article include vibration analysis and testing synchronized switching of shunt capacitor or harmonic filter circuit breakers.
Not all circuit breaker analyzers are capable of performing all of these measurements. It depends on the module’s configuration and software capabilities. Selecting the right base instrument is critical to be able to add any additional feature in the future.
REFERENCES
R. Foster, V. Naranjo, and D. Carreño. “Testing High Voltage Circuit Breakers with Both Sides Grounded Using Dynamic Capacitance (DCM) Technology,” IEEE Electrical Insulation Conference (EIC), 2018, pp. 439-442.
Volney Naranjo joined the Technical Support Group at Megger in 2011 as an Applications Engineer focusing on the products for transformer, low-voltage and high-voltage circuit breakers, batteries, and power quality testing. He participates in the IEEE Energy Storage and Stationary Battery committee and has published articles in conferences such as TechCon, PowerTest, TSDOS, BattCon, and EIC as well as technical magazines. Volney received his BSEE from Universidad del Valle in Cali, Colombia. After graduation, he worked in the areas of electrical design and testing and commissioning of power systems as a field engineer and project manager.
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HOW GROUNDS AFFECT PEAK VOLTAGE DUE TO LIGHTNING
BY AL MARTIN, retired
Did you know that the most common characterization of a ground rod may not work for lightning? In 1997, an experiment at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida, challenged the predominant view that ground rods are essentially resistive. That experiment found that the waveshapes of lightning currents in a building grounding system and those entering the electrical circuits of the building were considerably different. That was at odds with IEC 61312-1:1995 assertions that they should be the same. The conclusion was that, for lightning, the ground rod had an impedance with a reactive component in addition to the resistive one.
INDUSTRY TOPICS
So how do we take into account the impedance effects for lightning? Well, it turns out not to be so simple. Professor Leonid Grcev, who with his students has conducted extensive studies of grounds, found that a simple modeling of a ground rod as an R-L-C circuit doesn’t yield correct results due to surge propagation effects that cause deviation from the low-frequency behavior during the fast-transient period. So the challenge is to determine what this deviation is.
Grcev has shown that normal grounds (those not chemically treated or otherwise enhanced), can be characterized in terms of effective length and impulse coefficient (IC). The IC is the ratio of peak voltage across an actual ground rod to the peak voltage across a purely resistive ground rod in response to a surge. It shows how the impedance of the ground rod affects the expected peak voltage due to a surge relative to what it would have been if the ground rod were purely resistive.
EFFECTIVE LENGTH
The first thing to consider is the ground rod effective length leff, which is the maximum length of the ground electrode for which the
impulse coefficient is equal to one (1). leff will be used later in the discussion of the IC, which is what we really want.
To calculate leff, Grcev developed the relation:
ρ = soil resistivity in ohm-m and T₁ is the zeroto-peak rise time of the lightning current pulse.
Military Handbook 419 Table 2.3 shows a range for average soil resistivity of 1 to 500 ohm-m.
CIGRE TB549 Table 3.5 shows a range of front durations of 1.1 µsec for the average subsequent stroke to 18 µsec for the maximum first stroke. Considering those values, the ρT₁ product could reasonably range from 1 to over 1,000 ohm-m-µsec. We can use those values in equations (2) and (3) to make a plot of leff vs. ρT₁, as shown in Figure 1. Both slower rise time and higher soil resistivity lead to a longer effective ground-rod length.
IMPULSE COEFFICIENT
If the length s of the ground rod is less than leff (Figure 1), the ground rod is primarily resistive, with some capacitive effect. If the length of the ground rod is greater than leff, the ground rod will have inductive effects. So which effect do we have, and what is the consequence of that effect?
Well, that’s what the IC determines. Grcev has proposed the relation: (4)
where A = Z/R is the impulse coefficient, Z is the effective impedance, R is the ground rod resistance, α is calculated from equation (2), and β is calculated from equation (3).
Figure 1: Variation in Effective Length of a Ground Rod with Soil Resistivity and Zero-to-Peak
IMPULSE COEFFICIENTS
For A >1, the ground rod has an effective series inductance in addition to its resistance. In this case, the peak voltage will be A times bigger than it would have been if the ground rod were purely resistive.
For A <1, the ground rod has an effective parallel capacitance in addition to its resistance. In this case, the peak voltage will be A times lower than it would have been if the ground rod were purely resistive.
From equation (4), the effect of the ground rod reactance can be calculated. As an illustration, take the four cases of ρT₁ = 100, 300, 1,000, and 10,000, and use equation (4) to plot the impulse coefficient A vs. the length of the rod. Ground rods with a low ρT₁ product have a high impulse coefficient, whereas ground rods with a high ρT₁ product have a low impulse coefficient, as shown in Figure 2.
Figure 3 is a replot of Figure 2 for ground rods of a length normally used in the field (≤ 10 m).
For ground rods ≤ 10 m, the low value of the impulse coefficient means that the peak voltage across the ground rod will be less than would be calculated for a purely resistive ground rod. For example, for a common 2-m rod, the ratio of peak voltage to the peak voltage across a purely resistive ground rod is in the range of 0.2 to 0.4, depending on the ρT1 product. The voltage across the ground rod as a surge decays is determined primarily by the resistance of the ground rod. So as the surge decays, the effect of the ground rod reactance dies away (remember that the impulse coefficient is relevant only during the rise-time period).
CURRENT FLOWING IN THE GROUND ROD
Figure 2: Impulse Coefficient (Ratio of Peak Voltage to Peak Voltage across a Purely Resistive Ground Rod) Versus Length of Ground Rod
Figure 3: Impulse Coefficient for Ground Rods ≤ 10 M Long
The peak voltage developed across the ground rod is given by: (5)
where Irod is the peak current captured by the ground rod, and Z is the ground rod impedance.
To calculate I rod we need to calculate the fraction of the lightning current Imax captured by the ground rod. IEEE Std. 142 shows that 99% of the current flowing in the ground rod is captured in a volume having a radius of twice a ground rod length, s. Figure 4 illustrates this situation, where d is the distance from the
lightning strike point to the edge of a cylinder representing the ground rod outer effective extent.
The angle θ subtended by the ground rod is given by:
(6)
Note that the arcsin is not defined for arguments greater than 1, so there are two cases for equation (6): Case 1 where d ranges from 2s to infinity, and case 2 where d ranges from 2s to 0.
For case 1, if the arcsin is in degrees, then the fraction f₁ of the lightning current Imax captured by the ground rod is:
(7)
For case 2, if the fraction f₂ of the lightning current Imax captured by the ground rod is:
Combining equations (7) and (8), Irod = Imax (f₁ + f₂), which is:
Remember that in calculating Irod, the first term in equation (9) is only valid for d greater than 2 s, and the second term is only valid for d less than 2s.
PEAK VOLTAGE
The peak voltage is calculated from equation (5). The effective impedance Z of the ground rod to be used in equation (5) can be calculated from Dwight’s equation multiplied by A: (10)
where a is the radius of the ground rod.
Substituting equations (9) and (10) in equation (5):
As an example of the calculation of Vpeak, consider a 12 kA 4.5/77 subsequent surge from TB549 impinging on a 10-m rod 5/8 inches in diameter in the soil of 50 ohm-cm, 200 ohmcm, 600 ohm-cm, and 3,000 ohm-cm.
For these cases, Figure 5 demonstrates how Vpeak changes due to a decrease in ground-rod current capture with increasing distance.
Applicability of the Peak Voltage Calculation
(8)
(9)
Now a word about the applicability of the foregoing analysis. In the region near the lightning strike point, the ground resistivity ρ is highly variable. In particular, soil breakdown can happen when the electric field overcomes the soil ionization gradient. Soil ionization occurs when the electric fields at the ground electrode surface become greater than the ionization threshold of approximately 300 kV/m. In this case, in the region surrounding the current striking point, local transverse discharges start from the lightning strike point and stop at the points where the electric field drops below the critical
Figure 4: Effective Capture Area of the Ground Rod
breakdown strength. An illustration of this point is shown in Photo 1.
The literature on lightning shows that the streaks in Figure 6 are places where the ground is ionized. A circle of radius r₀ can be put around this area. The size of r₀ is determined by both the magnitude of the lightning current and ρ. In Figure 6, r₀ appears to be about 6 m, but that may or may not be typical. In any case, to avoid the area where ρ is highly variable, d should generally exceed 2r₀.
With the foregoing discussions in mind, different lightning waveforms, different ρ, and different ground rod lengths will result in different peak voltages from those shown in Figure 5.
SUMMARY
The usual assumption that ground rods are purely resistive is not what is actually observed in the case of lightning. Particularly for the relatively short ground rods commonly used, during the rise-time period, the ground rods look like an impedance with a significant capacitive component. The result is that for these commonly used ground rods, the peak voltage due to a lightning strike is generally significantly lower than would be the case for a purely resistive ground rod. Whether the peak voltage is higher or lower than for a purely resistive ground rod depends on a number of variables, including the surge waveform, the ground resistivity, the length of the ground rod, and the distance the observer is from the lightning strike point. The peak voltage across the ground rod can be calculated based on estimates of these variables.
REFERENCES
1. V. A. Rakov et al. “Direct Lightning Strikes to the Lightning Protective System of a Residential Building: Triggered-lightning Experiments,” IEEE Transactions on Power Delivery, Vol. 17, No. 2 (April 2002).
2. IEC Standard 61312-1:1995, Protection Against Lightning Electromagnetic ImpulsePart 1: General Principles
Figure 5: Example of Peak Voltage across 2 M Ground Rod Due to 12 kA 4.5/77 Strike
Extent of Ionization from a Lightning Strike to the Flag Marking the Hole
3. L. Grcev. “Impulse Efficiency of Ground Rods,” IEEE Transactions on Power Delivery, Vol. 24, No. 1 (January 2009), 441-451.
4. H. B. Dwight. “Calculation of Resistances to Ground,” Transactions of the American Institute of Electrical Engineers, (1936) Vol. 55, pp. 1319-1328..
5. IEEE. IEEE Std 142-1991, IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems.
6. MILHDBK419, Military Handbook Grounding, Bonding, and Shielding for Electronic Equipments and Facilities, Volume 1 of 2 Volumes on Basic Theory, January 1982.
7. Cigre TB549, Lightning Parameters for Engineering Applications, August 2013.
8. A. Geri. “Behaviour of Grounding Systems Excited by High Impulse Currents: The Model and Its Validation,” IEEE Transactions on Power Delivery, Vol. 14, No. 3, July 1999.
9. L. Grcev and V. Arnautovski. Proceedings of 24th International Conference on Lightning Protection (ICLP’98), Birmingham, UK, 1418 September 1998, Vol. 1, pp. 524-529.
Al Martin holds a BEE degree from Cornell University and a PhD from UCLA. He joined Raychem in 1975 and held a number of positions with Raychem, which became TE Connectivity) until retiring in 2013. Al has been a contributing member of TIA TR41, ATIS NIPP- NEP, ITU-T, the IEEE EMC Society, the IEEE Power and Energy Society, and the IEEE Product Safety Engineering Society. He has been an editor for TIA TR41, ATIS NIPPNEP, and IEEE standards, and is presently chairman of IEEE PES SPDC WG3.6.7 Surge Protectors and Protective Circuits Used in Information and Communications Technology (ICT) Networks, including Smart Grid Data Networks, and vicechairman of WG3.6.2 Solid State Surge Protective Device Components. He serves as a member on the Telecom Advisory Committee of the IEEE Product Safety Engineering Society and is the author or co-author of over 30 papers on EMC and telecommunications, including nine PEG presentations. Al is a Life Senior Member of the IEEE and the IEEE SA.
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ELECTRICAL SAFETY THROUGH THE LENS OF THE FIRE & LIFE SAFETY ECOSYSTEM
BY DEREK VIGSTOL, National Fire Protection Association
Electrical safety is often described as a three-legged stool encompassing proper installation, routine maintenance, and applicable safe work practices. It is this relationship that sets the stage for what can best be described as the electrical safety ecosystem as it lives within the larger overall NFPA Fire & Life Safety Ecosystem™.
This Ecosystem is made up of eight key elements (Figure 1) that must all work together and are interdependent on each other. A breakdown in one element often leads to tragedy, and when it comes to electrical safety, the stakes are even higher.
On top of keeping the world working safely within this well-oiled system, industry professionals are tasked with keeping up with an ever-changing technological landscape. Equipment and building systems are evolving at a faster pace than ever before as manufacturers strive to solve issues with energy efficiency, equipment resiliency, building manageability, and cybersecurity. Keeping up with this
changing industry is paramount to the success of the Ecosystem and that three-legged stool of electrical safety.
CODES AND STANDARDS
One of the key components of this ecosystem is that we develop and use codes and standards based on the most up-to-date information available. Imagine trying to stay on top of the dangers of today’s lithium-ion energy storage system (ESS) hazards if all we had were the installation requirements for storage batteries from the 1981 edition of NFPA 70, National Electrical Code® (NEC®)! This would be extremely problematic.
INDUSTRY TOPICS
Fortunately, that is not the case. Today, we have specific requirements in a number of codes and standards that address the hazards with these ever-evolving battery technologies. However, requirements across multiple codes and standards means that those who design, install, and maintain electrical equipment have more places to look when they need to find the necessary information.
Energy Storage Systems
Take an energy storage system, for example. As an electrician, I immediately think of Article 706 in the NEC and Article 480 for storage batteries, if the ESS happens to employ batteries as the energy storage medium. But there is also the new standard, NFPA 855, Standard for the Installation of Stationary Energy
Storage Systems . This standard addresses the minimum requirements for mitigating the hazards associated with ESS. Additionally, NFPA 1, Fire Code contains an entire chapter on energy storage systems from a fire danger standpoint. And a number of other codes and standards contain information like how these systems can serve an installation, how and when these systems must be maintained, how to work safely around ESS equipment, and how to address an ESS when there is a problem. All in all, at least half a dozen documents contain requirements for safety around energy storage equipment throughout its lifecycle.
Microgrid
As technology like ESS and solar/wind power generation becomes more prevalent in the built
Figure 1: NFPA Fire & Life Safety Ecosystem SOURCE: NATIONAL FIRE PROTECTION ASSOCIATION
INDUSTRY TOPICS
environment, this has become more of an issue. Today’s electrical systems seek to resolve issues with resiliency and efficiency. This has led to an increase in the number of systems utilizing this technology and has put terms like “microgrid” and “island mode” on the tip of everyone’s tongue in the NEC universe. With facilities aiming their sights squarely on establishing a system that can weather just about anything that comes their way and keeping energy costs to a minimum, microgrids seem to be popping up everywhere. This usually means an entire system that depends on solar/wind generation and ESS to stay operational, and it presents challenges from both maintenance and upkeep standpoints due to the hazards this type of system presents.
Let’s take a look at some requirements that will help keep us safe.
First, we must fully grasp and understand just what is meant by the term “microgrid.” There has been a lot of discussion around this term ever since it was added into the NEC, but it often seems as though folks are overcomplicating the issue. In its basic form, a microgrid is defined in the NEC as:
“A premises wiring system that has generation, energy storage, and load(s), or any combination thereof, that includes the ability to disconnect from and parallel with the primary source.”
In other words, a microgrid is simply a premises wiring system that can stand on its own if need be and can operate in parallel with a primary source such as a utility-fed service. Not overly complicated when it comes to answering the question of “what is a microgrid.” However, let’s break down the individual components of a microgrid and explore the requirements there.
We’ll start by diving right into energy storage systems, in particular, battery-type energy storage systems. We will need to look in both the NEC and NFPA 855 for requirements related to the design and installation of these systems.
NEC Section 706.3
First and foremost, section 706.3 requires that only qualified persons as defined in the NEC install and maintain these systems. This means that only those individuals who possess skills and knowledge related to the construction and operation of the electrical equipment and installations and have received safety training to recognize and avoid the hazards involved are able to work on these systems.
Article 706 goes on to require other safety measures like how systems must be listed, disconnecting means configuration, circuit sizing, and capacity along with overcurrent protection, ventilation, and how to make the connection to an energy source.
ESS must also be maintained in safe and proper operating condition. This required maintenance must be in accordance with both manufacturer’s requirements and industry standards, and a written record must be kept of all maintenance and repairs performed.
NFPA 70B
One such document that provides industry knowledge for maintenance is NFPA 70B, Recommended Practice for Electrical Equipment Maintenance. However, in NFPA 70B, you are not going to find specific requirements for maintaining an ESS. You will find recommendations on how and why to establish an electrical preventive maintenance program. You will also find recommendations on what information to collect, how to collect it, and some basic fundamentals that make up maintaining these systems such as cleaning and personnel safety. However, the requirement for what needs to be checked, when it needs to be checked, and how it gets checked often comes from elsewhere like the manufacturer’s information.
NFPA 855
Lastly, we also need to be thinking about other hazards associated with an ESS that
are now incorporated into the installation when we install a microgrid. NFPA 855 addresses many of these other hazards. There are requirements within 855 for emergency planning for when something goes wrong, protection of thermal runaway incidents, and even explosion control to be implemented in accordance with NFPA 69, Standard on Explosion Prevention Systems. There are also requirements for fire protection systems depending on the type of ESS employed.
PHOTOVOLTAIC EQUIPMENT
However, all of this only addresses the ESS portion of the microgrid. Don’t forget we must also address the other components. One of the more popular energy sources for microgrids is solar photovoltaic (PV) equipment, which has its own set of requirements to follow. NEC Article 690 addresses the installation of PV systems for safeguarding persons and property from the electrical hazards this type of equipment presents. Here we can find requirements for sizing conductors based on how much current the PV system will supply and how to protect those conductors from overcurrent. We’ll also find requirements for how to shut off the system intentionally as when adverse conditions exist. This requires isolation disconnects, rapid shutdown for emergency response, and arc-fault detection in order to shut the system down when it presents a hazard.
However, there are also requirements for grounding and bonding, safety marking and labeling of PV systems, and the same requirement as ESS systems that require only qualified persons to install PV system equipment and wiring components.
An entire chapter in NFPA 70B deals with the maintenance of PV systems. Here we can find recommendations on how to plan out a maintenance schedule to maximize the longevity of these systems and keep them performing as intended for years. The
environment where we install these systems plays a crucial part in planning out how we take care of them as well.
For instance, PV systems are on nearly every building in California. If the building location is within close proximity to the ocean, the maintenance plan might need to include a procedure for cleaning the salt off of the modules and other associated equipment like the inverter and possibly the charge controller if the ESS is also installed where exposed to this environment. Another thing to maintain is labelling or marking. When the NEC requires us to mark something with the hazard present or leave a placard showing the location of other key components of the system, it is important that these labels are suitable for the environment where they will be installed. We must make sure we maintain them in legible condition and that the environment hasn’t damaged them beyond recognition.
These are just a few examples of where we need to begin when it comes to building out the electrical safety ecosystem. We find a number of requirements for qualified persons to install and service the equipment that makes up a microgrid. Having a skilled workforce is one of the key components to protecting the world from electrical hazards. We also want to make sure we are using the most recent editions of the various codes and standards since these are based upon the most recent information available to the industry.
ENFORCEMENT
We also need effective enforcement, which means that people in job roles like the AHJ must be aware of and stay current with industry trends and the latest requirements. However, enforcement isn’t always coming from the AHJ role. Many times, as is the case with safe electrical work practices, it is the employer who must enforce the rules. No matter who does the job, effective enforcement is critical to ensuring the highest level of safety.
INDUSTRY TOPICS
INVESTMENT
All of this requires a significant investment in safety. There will need to be training, development of electrical safety plans and electrical preventive maintenance plans, and investments in new technology that provides new ways of approaching the electrical system within a building. We also need to keep pace with the changing trends in the industry. To do this the right way, electrical safety must be a place where no corners are cut. Replace equipment if we know it to be unsafe; make the investment now before the investment turns into fines and restitution. Be prepared to respond when the unthinkable happens. We can follow all aspects of the ecosystem, but if there is no emergency plan, we can still fail to provide that needed level of electrical safety when we have no idea how to respond to an event. Remember, people’s lives are often on the line when it comes to electrical safety.
CONCLUSION
When we bring all these pieces together to form our electrical safety ecosystem, it becomes more and more apparent just how much work we really have in front of us. With technology evolving on a daily basis, keeping up with what a person needs to know often seems an impossible task or at a minimum, a full-time job all by itself.
However, staying connected and getting involved will help keep us on that leading edge of knowledge and expertise that the world depends on us for. Keep in mind that, without those of us in the electrical industry with safety as a core principle for doing what we do day in and day out, the whole thing can come crashing down. The electrical world is a complex and often confusing world to navigate, but with a little help, we can achieve the level of safety we all strive for. Remember, it’s a big world. Let’s protect it together!
RESOURCES
The NEC, NFPA 1, and NFPA 70B are now available in NFPA LiNK™, the association’s information delivery platform with NFPA codes and standards, supplementary content, and visual aids for building, electrical, and life safety professionals and practitioners. Learn more at nfpa.org/LiNK
Derek Vigstol is Senior Electrical Content Specialist with the National Fire Protection Association (NFPA) in Quincy, Mass. He can be reached at dvigstol@nfpa.org.
DOBLE LABORATORY SERVICES:
ANALYSIS AND ENGINEERING GUIDANCE TO HELP MANAGE CRITICAL ASSET RISK
Since 1933, our experienced team of engineers and chemists has helped customers determine the health of transformers and other oil-filled assets. Whether it’s routine oil testing or development of cost-effective testing programs, customers rely on our expertise for independent interpretation of results and high quality data. Doble also offers in-depth reporting and consulting services to help clients analyze test results and make informed decisions about asset health and maintenance.
At five ISO 17025-accredited laboratories located throughout North America, Doble offers over 200 tests and testing packages on both solid and liquid insulation, including:
• Dissolved gas-in-oil analysis (DGA)
• Furanic compounds-in-oil
• A multitude of oil quality test packages
• Water content
• Corrosive sulfur
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• Wear metals in oil (Doble Test Method)
• Dissolved metals in oil
• Load tap changer analysis program
• Breaker analysis program
• Material compatibility programs
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• Methanol, ethanol and furanic compound analysis
For comprehensive data analysis and fleet asset management, automatically load your test results into Doble’s INSIDEVIEW® software.
For a full menu of Doble’s laboratory services, visit: doble.com/lab-services. To request information on consulting services or proposals, please contact us via email at Labservices@doble.com.
DETERMINING CELLULOSE DEGRADATION IN TRANSFORMERS USING INDIRECT TESTS
LANCE R. LEWAND and DAVID KOEHLER, Doble Engineering Company
The design life of a transformer is usually about 20 to 25 years. In the United States, estimates show the average age of a transformer is currently around 42 years, which means a number of even older units are still in service. As with all things, transformers age and degrade over time. Transformer failures can come from a variety of sources including through faults, faulty crimps and brazes, corrosive sulfur, poor design, water intrusion, collateral damage from a bushing or load tap changer (LTC) failure, incorrectly sized leads, and a host of other issues. Overall, however, the demise of a transformer from normal aging is linked directly to the condition of the solid insulation (i.e. paper, cellulose).
PAPER INSULATION
Paper is used as an insulating medium because it is inexpensive, a very effective dielectric, has high mechanical strength, and allows insulating liquids to fill voids in the insulating structure. Much of the mechanical strength of paper and pressboard comes from the long-chain cellulose polymer. As the cellulose ages, the polymers are cleaved and become shorter, resulting in reduced mechanical strength.
Although the two main insulation components in a transformer are the insulating liquid and the cellulose (paper), it is the paper that is the main driver of transformer life, as it is intimately wrapped around the conductor and cannot be easily replaced, nor can it be remediated in situ. In contrast, the insulating liquid can easily be replaced, reclaimed, or reconditioned.
However, the same stressors that negatively impact the insulating liquid will also impact the
paper. The main stressors to insulating liquids are heat and oxygen. Minor stressors are organic acids and possibly the catalytic effects of copper. Water has little to no effect on the life of the insulating liquid. Paper degradation is accelerated by heat and oxygen, as are insulating liquids, but the added stressor of water is significant and is directly proportional to the water concentration in the paper. Also like insulating liquids, the minor stressors of organic acids and metal catalytic effects play a role. Insulating liquids and paper degradation has been discussed in numerous papers over the years and thus will not be discussed in detail in this article.
ASSESSING PAPER INSULATION CONDITION
Since paper degrades, it becomes vitally important to monitor the degradation process and take effective measures to reduce or delay the aging process. Several analytical tools can
be used to assess the condition of the paper insulation. These tools are broken down into two large categories: direct and indirect tests.
Direct Tests
These tests are conducted directly on the paper insulation from the transformer. The two most common tests are tensile strength and degree of polymerization (DPv). Both tests require paper samples from the transformer. The DPv test measures the average length of the cellulose molecule in the paper. DPv values of 1,000 to 1,300 are considered consistent with new paper; as values of 200 would be considered end-of-life, and values of 400 would be considered midlife as it is a logarithmic relationship as opposed to linear. McNutt proposed a life curve based on the DPv value.
Taking a paper sample for DPv or tensile strength is an expensive proposition. Some or
ADVANCEMENTS IN INDUSTRY
all of the insulating liquid must be drained from the transformer and samples dissected from various locations in order to adequately assess the aging of the insulation. Then those sections where samples were retrieved must be repaired followed by preparing the transformer to receive and install the insulating liquid back into the unit.
The biggest obstacle is deciding where in the transformer to retrieve the paper sample. An attempt needs to be made to find the hottest spot insulation as this will dictate the survivability of the transformer over time. Most often, the hottest spot insulation is in the upper third of the winding and cannot be retrieved unless the transformer is scrapped. Paper aging in transformers is not uniform; it follows thermal and water gradients. In addition, external layers are more exposed to higher concentrations of oxygen and the byproducts of aging in the insulating liquid. Actual DP measurements from various areas of the transformer can be drastically different depending on the local conditions.
Because of the sheer intrusiveness and exorbitant cost, this is seldom done on in-service transformers. Additionally, if it is a generating unit, revenue is lost as a result of the transformer
being out of service while the process in ongoing. Although direct tests can provide information on the paper in the general vicinity from which they were taken, it cannot provide a global determination of the transformer insulation as a whole. This is why there has been a focus on indirect tests to gather valuable information.
Indirect Tests
Most indirect tests are the analysis of chemical markers in the insulating liquid. Electrical tests such as power factor, dielectric frequency response (DFR), gas-in-oil monitors, and water-in-oil monitors can help one understand the condition of the cellulose, but the results of these tests are unable to define the aging process relative to how much of the cellulose life has been consumed.
Indicators of cellulosic aging are:
• Water content/relative saturation
• Acidity of the oil
• Carbon oxide concentrations
• Furanic compounds
• Methanol and ethanol concentrations
Water Content
Analyzing the water content of the oil using on-line monitors or water-in-oil measurements can provide some indication of the condition of the paper. Along with DFR, they can provide information on the water content of the paper through mathematical interpretation. As the water content of the cellulose doubles, the life of the paper decreases by half, so it is directly proportional. However, determining the end of life of the paper or how much life has been consumed through these means is not effective.
Acid Neutralization Number
The acid content (neutralization number) is another marker that paper has decayed as the broken bonds in the cellulose structure
Figure 1: Example of the Amount of Paper around a Lead
Figure 2: Three Units of a Cellulose Molecule
5-hydroxymethyl-2-furfural furfuryl alcohol
5-hydroxymethyl-2-furfural furfuryl alcohol
5-methyl-2-furfural 2-acetyl furan
Figure 3: Commonly Found Furanic Compounds
5-methyl-2-furfural 2-acetyl furan
will eventually form measurable acids. But other materials in the transformer also form acids. Natural esters in the insulating liquid, for example, forms large amounts of acids. Therefore, it becomes difficult to distinguish between paper degradation and other materials being degraded. So, although useful in a general sense, this test has not been used to determine the remaining life of paper insulation.
Carbon Oxide Gases
Carbon oxides — carbon monoxide (CO) and carbon dioxide (CO2) — can be detected from dissolved gas-in-oil (DGA) or online DGA sensors that alert the user that paper degradation has occurred. Carbon oxides can be produced from outgassing of transformer components, especially in older transformers, but generally most of the production is from cellulose decay. There have been attempts to use carbon oxide concentrations to estimate paper life, especially
in Japan (Yoshida, et al), but it is not common practice. It is probably more suitable to sealed transformers that are not leaking as opposed to free-breathing transformers that can lose much of the CO to the atmosphere because of the partitioning coefficient.
Furanic Compounds
Furanic compounds are probably the most notable of the cellulose degradation indicators that began to develop as a method of analysis in the 1980s in Europe.
Through the hydrolytic, oxidative, and thermal stressors already discussed, the polysaccharide of cellulose (Figure 2) is broken down into smaller and smaller molecules forming a variety of products including alcohols, carbon oxides, waters, acids, and free glucose that is not soluble in the insulating liquid. To form furanic compounds, the glucose undergoes
additional reactions that break the sixmembered carbon rings into five-membered ring structures (Figure 3). Unsworth and Mitchell demonstrated a mechanism by which the open-chain glucose molecule goes through a series of dehydration reactions (elimination of water molecules) and then recycles into a fivemembered ring structure. Furanic compounds, unlike sugars such as glucose, are oil soluble and therefore are detectable.
ANALYZING FURANIC COMPOUNDS
ASTM Method D5837 and IEC 61198 are the methods employed to perform furanic compound analysis; they can be utilized for all insulating liquids including natural and synthetic esters. The method involves extracting semi-polar compounds, in which furanic compounds might be present, from the insulating liquid into a more polar solvent that is then injected into a high-performance liquid chromatograph (HPLC). In the HPLC, the extracted eluent is passed through an analytical column that separates the compounds by polarity and molecular weight. The compounds are detected by the use of a tunable ultraviolet (UV) detector optimized at specific wavelengths for the desired compounds. Furanic compounds are measured in ug/L or mg/kg. Although there are many furanic compounds, many of them are unstable in the insulating liquid or the eluent and are of little use for routine diagnostic information.
Table1: Furanic Compounds Commonly Used for Diagnostic Purposes
is being used to provide an overall DPv value through the use of the Chendong or other similar equations.
Although a powerful tool for transformer diagnostics, it can be misapplied, as it was originally designed for free-breathing Chinesemade Kraft paper transformers, even though it is now used universally for all transformers. The equation is given as:
Equation 1: Estimated DP = ((log of 2-furfural in mg/kg) – 1.5)/-0.0035
SOURCE: XUE CHENDONG
The furanic compounds produced from locations of paper degradation inside a transformer are comingled from other locations in a transformer to provide a pseudo-average 2-furfural concentration in the oil, much like water and gas-in-oil measurements. The extent to which paper is aged in one or more locations will increase the value of the 2-furfural concentration.
The DPv value calculated by the Chendong equation does not apply to any one location within the transformer. It must be remembered that if the 2-furfural concentration is high, which corresponds to a low DPv value, the actual location in the transformer where the highest rate of paper degradation is taking place is probably much worse.
One compound, 2-furfural (FAL or 2-FAL), is the one most commonly present and used for diagnostic purposes. The 2-furfrual content
As stated, the specific population of transformers the Chendong equation is derived from were Kraft paper-wound, freebreathing, conservator-type transformers. Varied practices were used worldwide to manufacture transformers. Many transformers in Latin America, Europe, and parts of Asia, for example, have historically been manufactured with breathing conservator systems and Kraft paper insulation. Most open conservator systems seal out water, but not oxygen. In contrast, the most common practice in the United States is to seal the oil and paper from air by using either a sealed tank with nitrogen or a conservator tank with a polymer
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Table 2: Categories of Transformer Types
Kraft Paper All 55°C rise transformers Free Breathing < 50 ug/L/year
Kraft Paper
TU* Paper
All 55°C rise transformers
Sealed < 35 ug/L/year
Most 65°C rise transformers Free Breathing < 25 ug/L/year
TU* Paper Most 65°C rise transformers Sealed < 20 ug/L/year
SOURCE: DOBLE
Table 3: 2-Furfural Concentrations
2-Furfural Concentration, ug/L Information and Recommendations
< 100 Normal Aging
100 to 999 Some paper degradation has occurred. Resample in 36 months or sooner if rate does not exceed those listed in Table 2.
1000 to 1259 Paper degradation has occurred. Resample in 24 months or sooner if rate does not exceed those listed in Table 2.
1260 to 3325 The cellulose insulation has 50% to 25% remaining mechanical life. Resample in 18 months or sooner if rate does not exceed those listed in Table 2.
3326 to 4974 The cellulose insulation has 25% to 10% remaining mechanical life. Resample in 6–12 months or sooner if rate does not exceed those listed in Table 2.
4975 to 6284 The cellulose insulation is below 10% remaining mechanical life. Serious consideration should be given to planned replacement of this transformer in the near future. Resample in 3 months or sooner if rate does not exceed those listed in Table 2.
>6284 The cellulose insulation is near or past its mechanical life. Mechanical disruption of the windings, for example through faults, may cause unit to fail. Immediate mitigation is necessary.
The Chendong equation has come to be used by some to evaluate the paper DP for all transformers, regardless of paper type or preservation system. As transformers with different insulation and preservation systems accumulate different amounts and ratios of furanic compounds, they will have differing
aging profiles. The results of the calculation to estimate DP from the 2-furfural content needs to consider the kind of paper and the type of preservation system. For example, when used for nitrogen-blanketed and sealedconservator transformers, this calculation can seriously underestimate the degree of long-term aging, especially in transformers with thermally upgraded insulation. Under these conditions, the result could provide a false sense of security.
The Chendong equation is best used to estimate an average DP in transformers with Kraft paper insulation and free-breathing conservators. For other insulation and preservation systems, the equation can be used to estimate paper degradation from thermal events.
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Because of the differences in paper types and preservations systems, there are four categories for evaluating the results (Table 2). In addition, normal rates of accumulation concentrations of 2-furfural are provided for each category.
These rates can be calculated over the age of the transformer or from sample to sample. It is actually good to perform both calculations, as the current aging may be more severe than previous aging rates and is dependent on load increases over time, overheating events, environmental conditions, and leaks in sealed systems (Figure 4). To get a sense of severity and the degree of remaining life, the information in Table 3 may be useful.
The fate of furanic compounds in the oil can be changed by a number of processes very similar to the fate of acids, water, and gases-in-oil. Vacuum dehydration usually removes about 10% of the furanic compounds. Straight filtration using cellulose filters can remove as much as 15% of the furanic compounds, especially HMF, whereas oil replacement or reconditioning by Fuller’s earth or activated alumina will remove all of the furanic compounds. Removal of furanic compounds does not improve the paper condition, just as degassing does not repair the incipient fault condition of a transformer; it only
removes the evidence that the paper degradation has occurred. It is highly recommended to test the insulating liquid for furanic compounds before processing or changeout to serve as a baseline. It usually takes 6–12 months for furanic compounds to migrate from the paper back into the insulating liquid after a processing activity to establish a steady-state condition. Any furanic compounds produced after that point should be added to the baseline value determined before the processing activity to get a more reliable indicator of the true aged condition.
Several other factors can affect the amount of 2-furfural in the insulating liquid. 2-furfural can be decomposed at really high temperatures that produce carbon monoxide and acetylene gases and thus does not adequately indicate that paper degradation has occurred. Additionally, the dicyandiamide used as the thermal upgrading agent in thermally upgraded paper can cause decomposition of 2-furfural through an oxidation reaction and thus yield lower levels than expected. Lastly, because furanic compounds are semi-polar, wet paper tends to bind more strongly to furanic compounds and yields less concentration in the insulating liquid. As a result, another method to determine paper degradation was needed.
Figure 4: Example of Degraded Insulation
ADVANCEMENTS IN INDUSTRY
METHANOL AND ETHANOL
Because most U.S. and Canadian transformers are built with thermally upgraded paper, the fate of 2-furfural is suspect and may not be the best indicator of paper degradation. In addition, wet paper reduces the concentration of furanic compounds in the insulating liquid. In 2007, research group IREQ (Jalbert et al), which is based in Canada and headed by Dr. Jalbert, was able to determine that the rupture of the glycosidic bond between the cellulose molecules in paper caused the formation of methanol. Additional research by that group developed a method for methanol as an indicator of cellulose aging in 2012. They also found that ethanol was produced but at higher temperatures. That method was developed into ASTM Method D8086, released in 2020.
Research has shown that methanol and ethanol concentrations are not impacted by the wetness of the paper insulation nor the dicyandiamide content of thermally upgraded paper. Additionally, it is an even earlier indicator of paper degradation than furanic compounds. Since the break in the glycosidic bond between two glucose molecule occurs before the glucose molecule is opened up to form the furanic compounds, methanol and ethanol is produced much sooner than furanic compounds. This provides the transformer owner with an earlier alert of a possible issue.
It was also determined that methanol appears to be more thermally stable than furanic compounds; it survives in temperatures about 110°C. Ethanol survives up to 130°C, whereas the temperature range for furanic compounds was 110°C and lower.
The methanol and ethanol concentrations need to be corrected to 20°C to establish a steady-state condition for comparing samples and from which to draw diagnostic value. It should also be noted that transformer design, insulating liquid to paper ratios, and other factors such as the presence of acids may influence the amount of methanol and ethanol produced and dissolved in the insulating liquid.
Table 4 provides information on the methanol concentration and the global calculated DPv value.
Based on the work by Jalbert et. al, the following interpretation model was presented to calculate the mean DPv value:
DP0 = Starting DPv value after initial factory dry out, usually around 1,000
CH3OH = methanol concentration in ug/kg (ppb)
Methanol and ethanol concentrations suffer the same fate as furanic compounds and other chemical markers from oil processing — most or all is removed even from vacuum treatment alone. However, the migration rate from the paper into the insulating liquid is much quicker than furanic compounds — usually 6 months or less and higher than 89% of the methanol value before treatment. As a comparison, most
SOURCE: CIGRE BROCHURE 779
Table 4: DPv Values from Methanol Concentrations
ADVANCEMENTS IN INDUSTRY
furanic compounds only return 18% to 26% of the methanol value before treatment.
Currently, analysis and modeling for methanol is for mineral-oil-filled transformers. Hydrolysis reactions that can be found when dealing with natural and synthetic esters may impact the concentrations of methanol and ethanol. Several researchers are currently looking into the degradation mechanism and chemical marker formation.
NOMEX
Since Nomex is a synthetic aramid fiber, no cellulose is present that can degrade. So DPv, furanic compounds, and methanol/ethanol analysis cannot yield any results that would indicate the remaining life of this type of insulation. The only type of analysis that can be performed is tensile strength testing, but this requires going into the transformer to gather Nomex insulation samples for testing; this is not a common practice and is an expensive endeavor. Researchers are actively trying to determine whether some chemical marker can be found in the insulating liquid to aid in determining the condition of the Nomex.
CONCLUSION
Direct tests on paper such as tensile strength and DPv are useful in determining the aging of the paper in the specific locations where the samples were taken. Because water and temperature gradients within the transformer dictate paper aging, degradation is not uniform within the transformer. Therefore, multiple samples are needed to get an adequate assessment. Retrieving the samples is intrusive and costly and thus not often performed.
A more useful and cost-effective approach is to determine the condition of the paper insulation through chemical markers in the insulating liquid. Water/relative saturation, acid content, and dissolved gases-in-oil can be indicators of paper degradation, but cannot be used to determine the remaining life of solid insulation.
Furanic compounds, developed in the late 1980s, are an excellent tool in determining the life of cellulose insulation, especially in free-breathing transformers with Kraft paper insulation. For transformers with thermally upgraded insulation, 2-furfural concentration, which is used to determine an average DPv value, can be compromised by very high temperatures and the dicyandiamide used to thermally upgrade the paper. Because of these factors, methanol and ethanol analysis were developed.
The presence of methanol and ethanol stems from the breakdown of the glycosidic bond between glucose groups in the cellulose molecule. As such, it is an early indicator of paper degradation, and the concentration is not compromised by the presence of dicyandiamide from thermally upgraded paper. In sealed systems with thermally upgraded paper, methanol/ethanol analysis would be the best choice for determining paper degradation. Because methanol/ethanol are light alcohols and volatile, samples must be taken in syringes like DGA in order to make sure the alcohols are not lost to the atmosphere.
For natural- and synthetic-filled transformers, methanol and ethanol production and/or stability may be negatively impacted. All chemical markers in the insulating liquid are negatively impacted by any insulating liquid replacement or processing; thus, baseline values must be established before any processing activity commences.
From the use of indirect tests such as furanic compounds and methanol/ethanol, the amount of paper degradation and an estimate of remaining life can be reasonably ascertained.
REFERENCES
Lewand L.R. and Griffin P.J. “How to Reduce the Rate of Aging in Transformer Insulation,” NETA World, Spring, 1995. McNutt, W. J. “Insulation Thermal Life Considerations For Transformer Loading Guides,” IEEE Trans. on Power Deliv, Vol. 7, No. 1, Jan. 1992, Pg. 392-401
Lewand, L.R. and Griffin, P.J. “Practical Experience Gained from Furanic Compound Analysis,” Proceedings of the Seventy-Third International Conference of Doble Clients, Boston, MA, 2006
Yoshida, H., Ishioka, Y., Suzuki, T., Yanari, T., Teranishi, T. “Degradation of Insulating Materials of Transformers,” IEEE Trans Dielectr Electr Insul, 1987, EI-22, pg. 795–800
Unsworth, J. and Mitchell, F. “Degradation of Electrical Insulating Paper Monitored with High Performance Liquid Chromatography,” IEEE Trans Dielectr Electr Insul, Vol. 25, No. 4, August 1990, pg. 737-46.
Chendong, X. “Monitoring Paper Insulation Aging by Measuring Furfural Contents in Oil,” 7th International Symposium on High Voltage Engineering, Aug. 26-30, 1991, pp. 139-142.
Jalbert, J., Gilbert. R., Tétreault, P., Morin, B., Lessard-Déziel, D. “Identification of a Chemical indicator of the rupture of 1,4-β-glycosidic bonds of cellulose in an oil-impregnated insulating paper system,” Cellulose, 2007, Vol. 14, pp. 295-309.
Jalbert, J., Gilbert. R., Tétreault, P., Morin, B., and Denos Y. “Kinetics of 1,4-β-glycosidic bonds rupture in cellulose and correlation with methanol formation during ageing of paper/oil systems. Part 1: Standard wood kraft insulation,” Cellulose, 2009, Vol. 16, pp. 327-338.
Jalbert, J., Duchesne, S., Rodriguez-Celis, E., Tetreault, P., and Collin, P. “Robust and Sensitive Analysis of Methanol and Ethanol from Cellulose Degradation in Mineral Oils,” Journal of Chromatography A, Vol. 1256, pp. 240-245, September 21, 2012.
CIGRE. “Field Experience with Transformer Solid Insulation Ageing Markers,” CIGRE Brochure 779, October 2019. Committees A1/D2.
Griffin, P.J., Lewand, L.R., and Pahlavanpour, B. “Paper Degradation By-Products Generated Under Incipient-Fault Conditions,” Minutes of the Sixty-First Annual International Conference of Doble Clients, 1994, Sec. 10-5.
Lance R. Lewand is the Technical Director for the Doble Insulating Materials Laboratory. The Insulating Materials Laboratory is responsible for routine and investigative analyses of liquid and solid dielectrics for electric apparatus. Since joining Doble in 1992, Lance has published over 75 technical papers pertaining to testing and sampling of electrical insulating materials and laboratory diagnostics. He is actively involved in professional organizations including the American Chemical Society; has served on the ASTM D-27 since 1989 and chairs ASTM Committee D-27 as well as Subcommittee 06 on Chemical Tests; is secretary of the Doble Committee on Insulating Materials, and represents the U.S. on the National Committee for TC10 of the International Electrotechnical Commission (IEC) and ISO TC28. Lance is a recipient of the ASTM Award of Merit for Committee D-27. He received his BS from St. Mary’s College of Maryland.
David Koehler is the Business Development Manager, Professional Services for Doble Engineering Company. He has 23 years of experience in the testing of insulating liquids and management of analytical laboratories. He has provided numerous technical presentations and published technical articles within the power industry and is an active contributor at NETA’s PowerTest Conference. David is Vice President-elect for IEEE Member and Geographic Activities (MGA) and a member of IEEE’s Honor Society, HKN. He served on the IEEE Board of Directors from 2019–2020 and will serve on the IEEE Board of Directors again in 2022. David is a member of the ASTM D-27 Technical Committee on Electrical Insulating Liquids and Gases and serves as an Advisory Board Member for Engineering and Technology at Embry-Riddle Aeronautical University, Worldwide Campus. David is a past Executive Committee member of the Indiana American Chemical Society. He received a BS in chemistry from Indiana University and obtained his MBA.
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ANSI/NETA STANDARDS UPDATE
REVISION SCHEDULED
ANSI/NETA ETT–2018 REVISION SCHEDULED FOR 2021
ANSI/NETA ETT, Standard for Certification of Electrical Testing Technicians , 2018 Edition is in the process of revision. The initial ballot was completed July 2021. Suggested comments and revisions will be reviewed by the Standards Review Council in fall 2021. A second ballot is scheduled for late 2021. The revised edition of ANSI/NETA ATS is scheduled to debut at PowerTest 2022.
ANSI/NETA ETT establishes minimum requirements for qualifications, certification, training, and experience for the electrical testing technician. It provides criteria for documenting qualifications for certification and details the minimum qualifications for an independent and impartial certifying body to certify electrical testing technicians.
SPECIFICATIONS AND STANDARDS
ANSI/NETA ATS–2021 LATEST EDITION
ANSI/NETA ATS, Standard for Acceptance Testing Specifications for Electrical Power Equipment & Systems, 2021 Edition, has completed an American National Standard revision process. ANSI administrative approval was granted September 18, 2020. The new edition was released in March 2021 and supersedes the 2017 edition.
ANSI/NETA ATS covers suggested field tests and inspections for assessing the suitability for initial energization of electrical power equipment and systems. The purpose of these specifications is to assure that tested electrical equipment and systems are operational, are within applicable standards and manufacturers’ tolerances, and are installed in accordance with design specifications. ANSI/ NETA ATS-2021 new content includes arc energy reduction system testing and an update to partial discharge survey for switchgear. ANSI/NETA ATS-2021 is available for purchase at the NETA Bookstore at www.netaworld.org.
ANSI/NETA ECS–2020 LATEST EDITION
ANSI/NETA ECS, Standard for Electrical Commissioning of Electrical Power Equipment & Systems, 2020 Edition, completed the American National Standard revision process. ANSI administrative approval was received on September 9, 2019. ANSI/NETA ECS–2020 supersedes the 2015 Edition.
ANSI/NETA ECS describes the systematic process of documenting and placing into service newly installed or retrofitted electrical power equipment and systems. This document shall be used in conjunction with the most recent edition of ANSI/NETA ATS, Standard for Acceptance Testing Specifications for Electrical Power Equipment & Systems .
PARTICIPATION
Comments and suggestions on any of the standards are always welcome and should be directed to NETA. To learn more about the NETA standards review and revision process, to purchase these standards, or to get involved, please visit www.netaworld.org or contact the NETA office at 888-300-6382.
The individual electrical components shall be subjected to factory and field tests, as required, to validate the individual components. It is not the intent of these specifications to provide comprehensive details on the commissioning of mechanical equipment, mechanical instrumentation systems, and related components.
The ANSI/NETA ECS–2020 Edition includes updates to the commissioning process, as well as inspection and commissioning procedures as it relates to low- and mediumvoltage systems.
Voltage classes addressed include:
• Low-voltage systems (less than 1,000 volts)
• Medium-voltage systems (greater than 1,000 volts and less than 100,000 volts)
• High-voltage and extra-high-voltage systems (greater than 100 kV and less than 1,000 kV)
ANSI/NETA MTS, Standard for Maintenance Testing Specifications for Electrical Power Equipment & Systems, 2019 Edition, completed an American National Standard revision process and received ANSI approval on February 4, 2019. The revised edition of ANSI/NETA MTS was released in March 2019 and supersedes the 2015 Edition.
ANSI/NETA MTS contains specifications for suggested field tests and inspections to assess the suitability for continued service and reliability of electrical power equipment and systems. The purpose of these specifications is to assure that tested electrical equipment and systems are operational and within applicable standards and manufacturers’ tolerances, and that the equipment and systems are suitable for continued service. ANSI/NETA MTS–2019 revisions include online partial discharge survey for switchgear, frequency of power systems studies, frequency of maintenance matrix, and more. ANSI/NETA MTS–2019 is available for purchase at the NETA Bookstore at www.netaworld.org.
BY TERRY BECKER, P.ENG., CESCP, TW Becker Electrical Safety Consulting Inc.
Changes in the CSA Z462, Workplace electrical safety Standard are slowing down. Good news! That said, the 2021 Edition includes significant reorganization of content in Clause 4.1 and Clause 4.3, changes to existing annexes and some new annexes, and a significant change to the Arc Flash PPE Category Method of determining “additional protective measures” for a work task’s arc flash risk assessment. CSA Z462, 2021 Edition IS NOT 100% technically harmonized with the 2021 Edition of NFPA 70E.
The following information is provided for the benefit of the reader in understanding the CSA Z462, Workplace electrical safety Standard and the updates/changes to the 2021 Edition, as well as for the employer in order to update an established electrical safety program. A compliant electrical safety program’s internal electrical safety audit would identify the need to update the electrical safety program whenever a new edition of CSA Z462 publishes.
Note: The information provided in this article is the technical interpretation of the author and is not an official interpretation from the CSA Group. The author takes no liability for the information presented. The information presented
is based on the published CSA Z462, 2021 Edition. This article does not include all changes or updates.
CSA Z462, 5 TH EDITION
CSA Z462, Workplace electrical safety Standard published its fifth edition on January 5, 2021. Since its inception in 2006 following CSA and NFPA executing a memorandum of understanding (MOU) to harmonize standards for North America, CSA Z462 has had a positive impact on electrical safety and the identification and effective management of arc flash and shock hazards. Lives have been saved!
SPECIFICATIONS AND STANDARDS
The first edition published in January 2009. Over the first four editions, significant evolution of the standard has occurred. CSA Z462 moved from focusing on hazard identification and PPE selection to a more mature standard aligned with occupational health and safety management system standards (e.g. CSA Z45001, ISO 45001) to include a mandatory risk assessment procedure. In the 2018 and 2021 Editions, CSA Z462 is 100% job and discrete work-task and risk-assessment based, including two unique risk assessments completed under the overall job’s risk assessment specific to the work task(s) that will be performed: the shock risk assessment and arc flash risk assessment.
Technical harmonization of the core clauses and articles between CSA Z462 and NFPA 70E has been maintained for the most part in the first four editions. CSA Z462 includes additional annexes that were not adopted into NFPA 70E. This has occurred again in CSA Z462, 2021 Edition.
The 2021 Edition of CSA Z462 includes additional changes of a technical nature related to the Arc Flash PPE Category Method that are not published in NFPA 70E. NFPA 70E, 2021 Edition includes a significant new Article 360 Safety-Related Requirements for Capacitors and an associated Annex R Working With Capacitors that are NOT included in the CSA Z462, 2021 Edition.
The CSA Z462, 2021 Edition public review draft closed July 29, 2020. You are encouraged in future revision cycles to submit public comments and influence the direction of the CSA Z462 standard. The CSA Z462 Technical Committee met on October 27, 2020, to review and approve final amendments to the draft, and a final vote occurred to the draft. The 2021 Edition of CSA Z462 as noted above published on January 5, 2021.
CLAUSES
The following changes and updates are noted. Not all changes are included in this article.
Clause 3 Definitions
The following definitions have been altered, or updated: Accessible, Balaclava (sock hood), Barrier, Equipment, Arc-Resistant, Fault Current, Available (Note), Receptacle, Shock Hazard, Voltage Nominal (note on float voltage for DC to change the threshold for applicability of CSA Z462 to 60 VDC from 30 VDC), and Work On (Notes). To clarify, if the voltage is 30 VAC or less or 60 VDC or less, CSA Z462’s requirements do not apply.
The following definitions are deleted: BranchCircuit Overcurrent Device, Switchgear, ArcResistant.
The following new definitions are added: Normal Operation, Policy, Procedure, Process, and Program.
Clause 4 Safety-Related Work Practices
A substantial reorganization of content from Clause 4.1 and Clause 4.3 has occurred. This is a positive change to further clarify the framework/contents of an employer’s electrical safety program and the elements that need to be considered when completing a work task’s risk assessment procedure. Content is deleted altogether, updated, or relocated between clauses. Significant clause number changes will occur with this realignment of content.
Clause 4.1 now identifies that an employer shall create and document an “Electrical Safety Policy” that affirms the organization’s commitment to identify electrical hazards, eliminate exposure, or assessment and control risks, and as a priority, establish an electrically safe work condition. This policy shall be documented in the employer’s electrical safety program. Clause 4.1 will now include a new clause with a general requirement that an electrically safe work condition shall be established as identified in Clause 4.2. Practices as identified in CSA Z462 Clause 4.1, and Clause 4.3 shall be used if an electrically safe work condition cannot be established.
SPECIFICATIONS AND STANDARDS ACTIVITY
Justification statements for energized electrical work are relocated from Clause 4.3 to Clause 4.1. With respect to the applicable voltage level that CSA Z462 applies to in the 2021 Edition, 30 VAC will be retained, but the threshold voltage for DC will be increased to 60 VDC.
Reference is now made to CSA Z45001 instead of CSA Z1000 as the CSA Group adopted ISO 45001 with respect to occupational health and safety management systems. Annex A in turn has been completely updated with respect to the comparison table of how CSA Z462 aligns with the requirements of CSA Z45001.
Some updated content will be added to the risk assessment procedure clause, specifically Clause 4.3.2.2.4 Normal Operating Condition will be relocated to Clause 4.1 under Risk Assessment Procedure and is renamed Normal Equipment Conditions. A new definition of Normal Operation is added. This is an appropriate update as the requirements of a normal equipment condition relate directly to risk assessment (e.g. likelihood of occurrence) and are not related to justification for energized electrical work. This aligns with the arc flash risk assessment CSA Z462 Table 2.
Additionally, in Clause 4.1.6.9 from the 2018 Edition (this clause will be renumbered), new Annex I content will be added providing an example of a job safety planning checklist. Updated Clause 4.1 content will be included for Lockout Program and Procedures.
A significant change in the 2021 Edition related to type of training includes the addition of language in the Notes for the existing Clause 4.1.7.1.5, which now recognizes that classroom training can include “interactive electronic or interactive web-based training.”
Some additional content is included in existing Clause 4.1.10 Portable (cord-and-plugconnected) Electrical Equipment related to maintenance, handling, and storage.
Clause 4.2 includes two changes to the existing Clause 4.2.5 Process for Establishing and
Verifying an Electrically Safe Work Condition and Clause 4.2.6 Temporary Protective Grounding Equipment.
A note is added to Clause 4.2.5 with respect to where a shared neutral conductor may still carry current. Some wording changes are included for a “permanently mounted absence of voltage tester.” A specific reference to UL 1436, Outlet Circuit Testers and Other Similar Indicating Devices is added.
In Clause 4.2.6 Temporary Protective Grounding Equipment, expanded content is added with respect to testing and inspection, and a new Annex T is added with extensive additional information.
In Clause 4.3 as noted above, significant content is relocated to Clause 4.1, which does enhance the flow of content in CSA Z462 and what an employer’s electrical safety program shall include for content.
In Clause 4.3 some additional content modifications are included with respect to describing the “estimate of likelihood and severity” for a work task’s shock risk assessment. CSA Z462 Table 2 Estimate of the Likelihood of Occurrence of an Arc Flash Incident for AC and DC Systems includes the deletion of the work task: “For DC systems, maintenance on a single cell of a battery system or multicell units in an open rack”; this duplicated “Maintenance and testing on individual battery cells or individual multi-cell units in an open rack.” A new work task was added: “Operation of a circuit breaker or switch the first time after installation or completion of work or maintenance in the equipment” for any equipment condition. The wording of “Removal or battery conductive intercell connector covers” changed to “Insertion or removal of connector covers or battery intercell connector(s).” The arc resistant switchgear work task description is updated and renamed “Arc-resistant equipment.”
SPECIFICATIONS AND STANDARDS
Some minor updates are included to Table 3 with respect to addition of “high-visibility apparel” and clarifying in notes that outerwear arc-rated clothing worn over selected arc-rated PPE is not considered as part of the required ATPV for the anticipated incident energy exposure.
In Clause 4.3.7.3 Personal Protective Equipment, new content is added to the note providing risk control method options to consider when the incident energy exceeds the ATPV of commercially available arc flash PPE to manage risk (e.g. Oberon Company 140 cal/cm2 ATPV).
In Clause 4.3.7.3.7 Hand and Arc Protection, a new Table 4A Maximum Use Voltage for Rubber Insulating Gloves is added to identify Class number and maximum AC and DC use voltages. This table is taken from ASTM F496, Standard Specification for In-Service Care of Insulating Gloves and Sleeves, Table 1 Voltage Requirements.
The most significant change in CSA Z462, 2021 Edition relates to Clause 4.3.7.3.15 Arc Flash PPE Category Method. The existing Table 6A Electrical Equipment Parameters were used (with other selected IEEE 1584 parameters) with the new IEEE 1584, 2018 Edition formulas. A new arc flash PPE category 5, minimum 75 cal/cm2, will be added for 600-V-class switchgear. Also, the arc resistant electrical equipment rows will clarify that the arc flash PPE category is N/A when doors are closed and secured and the available fault current does not exceed the arc-resistant rating of the electrical equipment. Table 6C Personal Protective Equipment (PPE) will add the new arc flash PPE category 5 and quote minimum 75 cal/cm2 ATPV arc flash PPE (e.g. Arc Flash Suit).
The most significant change is a new alternate table to Table 6A. Table V.1 is added in a newnormative Annex V Arc Flash PPE Categories. The existing Table 6A Arc-Flash PPE Categories for Alternating Current (AC) Systems has not been deleted and either Table 6A or Table V.1 can be used.
Included in the new Annex V is Figure V.1, Table V.1 Arc-Flash PPE Categories Selection flow chart, which is provided as a guide to the use of the alternate Table V.1. Table V.1 was added in an effort to simplify the information gathering required to use the arc flash PPE category method.
Of significance, this new Table V.1 includes electrical equipment that is “240 VAC singlephase” indicating abnormal arcing fault probability is sustainable for 240 VAC singlephase electrical equipment. Official clarification from the CSA Group with respect to the addition of 240 VAC single-phase electrical equipment in the new Table V.1 can be requested to get specific technical clarification on why 240 VAC single-phase electrical equipment is capable of sustaining an abnormal arcing fault condition and causing an arc flash to occur on 120/240 VAC panelboards.
Clause 5 Safety-Related Maintenance Requirements
A general rewrite of Clause 5 is included in CSA Z462, 2021 Edition. A lot of the existing content is retained but will be removed and the clause numbering is completely updated. A new clause is added with respect to the owner of the electrical equipment establishing, implementing, and maintaining a documented maintenance program for electrical equipment and references CSA Z463, Maintenance of electrical equipment Standard
The updates, revisions, and additions to Clause 5 improve its readability and the interpretation of the information presented. It is recommended that the CSA Z463, Maintenance of Systems Standard be purchased from the CSA Group and referenced with respect to reviewing electrical equipment maintenance requirements.
ANNEXES
In CSA Z462, 2021 Edition, several existing annexes are updated and several new annexes are included to provide additional explanatory
SPECIFICATIONS AND STANDARDS ACTIVITY
and supplemental information to reference with respect to the core clause content of CSA Z462.
Annex A Updated. References CSA Z45001 and provides a new cross-reference table specific to CSA Z462 and the CSA Z45001 occupational health and safety management system intent or objective.
Annex D Updated. The existing IEEE 1584, 2002 Edition content is deleted (no detailed formula content from IEEE 1584 is included). References added to only the new updated IEEE 1584, 2018 Edition.
Annex I Updated. Added a sample job briefing and planning checklist and a new Figure I.2 Sample Job Planning Checklist.
Annex J Updated. Sample energized electrical work permit and Figure J.2 Energized Electrical Work Permit Flow Chart amended to update the applicability of the permit for 30 VAC or now 60 VDC.
Annex K Updated. Includes a complete rewrite of the general categories of electrical hazards as related to arc blast indicating that arc blast pressure is not as significant as it has been presented in the past.
Note I have quoted that 40 cal/cm2 of incident energy is not a stop point for energized work, which has been a true statement for over 10 years. This updated published information in Annex K will now provide additional substantiation for this. Energized work tasks can be performed up to 140 cal/cm2 of incident energy, as an arc flash suit is available from Oberon Company with an ATPV of 140 cal/cm2.
DOCUMENT REVISION HISTORY
Annex O Updated. Safety-related design has been significantly updated with changes and additions.
Annex P New. Electrical switching and isolation is added to provide general information for low- or high-voltage complex switching and isolation including a new Figure P.2 Example Switching Order form.
Annex Q Updated. Arc flash and shock warning equipment labels includes minor wording updates and updated example equipment labels to correct the orange color used to properly align with ANSI Z535. A specific note is now included that states electrical hazard information for supervised industrial installations can be provided through alternative methods other than the application of equipment labels.
Annex T New. Temporary Protective Grounding is added to provide application information further in addition to the content of CSA Z462, Clause 4.2.6.
Annex V New. Arc flash PPE categories added. This is a normative annex providing an alternate table to Table 6A. An instructional flow chart is included: Arc-Flash PPE Categories Selection and then Table V.1.
SUMMARY
Since 2009, CSA Z462, Workplace electrical safety Standard has made a significantly positive impact in Canada to worker safety related to energized electrical work. Many employers are referencing CSA Z462 when developing their
SPECIFICATIONS AND STANDARDS ACTIVITY
electrical safety programs and determining the hierarchy or risk-control methods to apply to work tasks to eliminate exposure to arc flash and shock for qualified electrical workers and task qualified workers to reduce risk as low as reasonably practicable.
This article is not an official interpretation from the CSA Group and is based on the interpretation of the author of this article. You are advised to contact the CSA Group for any official interpretation. If you would like to discuss this article and the information presented, please contact me at terry.becker@ twbesc.ca (www.twbesc.ca) or 1-587-433-3777.
Terry Becker, P.Eng., CESCP, IEEE Senior Member, is an Electrical Safety Specialist and Management Consultant. He is the first past Vice-Chair of CSA Z462, Workplace electrical safety Standard Technical Committee and currently a Voting Member and Clause 4.1 and Annexes Working Group Leader. Terry is also a Voting Member on CSA Z463, Maintenance of electrical systems Standard and a Voting Member of IEEE Std. 1584, Guide for Performing for Arc-Flash Hazard Calculations. He has presented at conferences and workshops on electrical safety in Canada, the United States, India, and Australia, and is a Professional Engineer in the Provinces of British Columbia, Alberta, Saskatchewan, Manitoba, and Ontario.
COMMITTEE REPORT: NFPA 70B
BY DAVID HUFFMAN, Power Systems Testing Company
The new NFPA 70B, Recommended Practice for Electrical Equipment Maintenance closed its First Draft balloting on June 11, 2021, at 11:59 PM EDT. Much work has been done — and will continue to be done — by the committee members.
This has been a huge re-write with chapters added, moved, renamed, and completely revamped. Material that was anything but a “what to do” has been removed from the chapters but retained in annex material for its value.
The final two weeks of work included multiday Teams meetings between six and eight hours in length. We’re pretty happy with the outcome and very pleased to have a break from the work. The First Draft report will be issued by October 29, 2021. The public comment closing date for the Second Draft is February 9, 2022. The next publication is due to release in 2023.
David Huffman has been with Power Systems Testing, a NETA Accredited Company, since January 1988 and is currently CEO. He graduated from California State University, Fresno, and is a licensed Professional Electrical Engineer in the state of California as well as a NETA Level IV Certified Technician. David is a NETA board member, NETA’s Principal Representative to the NFPA 70B Committee, and serves as a member of various NETA committees.
COMMITTEE REPORT: CSA Z462 AND CSA Z463
BY KERRY HEID, Shermco Industries
NETA supports two main CSA standards in Canada: CSA Z462, Workplace Electrical Safety and CSA Z463, Maintenance of Electrical Systems. Both of these standards are entering a new revision phase.
TWO NEW TECHNICAL COMMITTEE CHAIRS
CSA Z462 is now chaired by Daniel Roberts. Daniel is well-known in electrical safety circles as an expert in electrical shock and arc flash exposure mitigation as well as standards development and training. This standard, which strives to remain harmonized with NFPA 70E, will release a new publication in 2024.
After 11 years as chair of CSA Z463, my tenure has expired. I’m pleased to announce that Lorne Gara (Shermco Industries and NETA Board Member) has been elected as the new technical committee chair. Lorne has numerous years of field experience and is highly regarded as one of the top technical experts within
NETA’s Standards Review Council. The next edition of Z463 will be published in 2023.
MEETINGS
In May 2021, virtual meetings were held for both standards to establish the technical committees, working groups, and timeline to the next edition. Face-to-face meetings are expected to take place during the fall of 2021.
Kerry Heid is an Executive Consultant at Shermco Industries. After beginning his career with Westinghouse Service, Kerry founded the Magna Electric Corporation (MEC) office in Regina, Saskatchewan in 1996 and became President of the company in 2001. MEC was acquired by Shermco Industries in December 2013, and Kerry served as CEO of Shermco Industries Canada until 2019. Kerry is a NETA Certified Level IV test technician and is active in Canadian standards development. He has served as Chair of the CSA Z463, Maintenance of Electrical Systems Technical Committee since 2010, and as a member of the CSA Z462, Workplace Electrical Safety Technical Committee since its inception in 2006. He received the prestigious Award of Merit from the Canadian Standards Association in 2019. Kerry served on NETA’s Board of Directors from 2003–2014, is a past-President, and received NETA’s Outstanding Achievement Award in 2010.
OUTGOING NETA PRESIDENT SCOTT BLIZARD: UP TO THE CHALLENGE
A change in NETA leadership occurs every two years, with the transition to a new president recognized as an important part of the association’s history and a key to its longevity and progress. NETA World’s custom is to share the outgoing president’s perspective in a thoughtful and reflective interview.
Outgoing President Scott Blizard has been Vice President and Chief Operating Officer of American Electrical Testing Co. LLC since 2000. During his tenure, Scott acted as the Corporate Safety Officer for nine years. He has over 25 years of experience in the field as a Master Electrician, Journeyman, Wireman, and NETA Level IV Senior Technician.
Scott went to work early with his father, Charles – a former NETA President – and spent most of his life being around and working within the family company. “I grew up in the industry and in NETA,” he says. One of the lessons his father imparted to him over the years was the importance of giving back to the industry. “I was never good at sitting still,” Scott admins, “so I decided to just go for it and follow my father’s example of giving back to the industry.”
Scott credits his success to the love and support of his wife, Laurie, and their five children — Daniel, Cortneigh, Christopher, Cameron, and Riley — as well as his granddaughter, Sadie.
Scott has made many contributions to NETA over the years. He currently chairs the Promotions & Marketing and Safety Committees and is a member of the Membership
Application Review Committee, the Technical Representation Steering Committee, the Finance Committee, and the Conference Committee. He represents NETA on NFPA 70, National Electrical Code Code-Making Panel 10; is an alternate to Dave Huffman on NFPA 70B, Recommended Practice for Electrical Equipment Maintenance; and is a frequent NETA World author. Scott received NETA’s Outstanding Achievement Award in 2019.
Q: Looking back over your service as NETA President, what accomplishment are you most proud of?
Blizard: I am proud of the NETA TEAM and having had the privilege of guiding our organization through the COVID-19 Crisis.
Q: With two years of focused industry leadership behind you, what has emerged as the biggest challenge facing the electrical power testing field?
Blizard: To keep NETA in the forefront of the electrical industry, it’s critical to be able to show the value of hiring a NETA-Accredited Company. It can be challenging to educate the
results of acceptance testing and commissioning new installations to assure they operated as designed; encourage them to develop a maintenance program to properly assure the equipment is functioning as designed, and promote the need for continuing education of our technicians to insure they are up to date with the latest technology.
Q: What impact will the growth of alternative power like wind and solar have on the industry?
Blizard: New technology along with the growth of alternative power is creating new opportunities for NETA Member Companies. Following the government spend on alternative sources of power and with the majority of the 50 states setting
Left: Scott Blizard received NETA’s Outstanding Achievement Award in 2019.
Below: Jim White and Scott Blizard attend PowerTest 2020
POWERTEST TV OFFERED A MORE CUSTOMIZABLE CONFERENCE EXPERIENCE THAN EVER BEFORE AND WAS A GREAT SUCCESS.
standards to be carbon-free, this trend is not going away. We must embrace the opportunity as it is the future of our industry.
Q: Did PowerTest’s performance as a virtual event surprise you?
Blizard: It didn’t surprise me as much as you might have thought. We started planning a virtual event in the background in June of 2020 when NETA Executive Director Missy Richard and I began looking at platforms. We had a pretty good idea of who we wanted to use if we had to cancel the live event. Most of the credit for the success for PowerTest 2021 should go to Conference Chair Ron Widup and NETA staff led by Events and Editorial Services Manager Laura McDonald, with a shout-out to the promotion and marketing team and liaison Marketing Project Manager Katie Polzin.
PowerTest 2021 was able to fill the void of CEU and CTD training during the COVID-19 crisis. The program was designed around the needs of the technician, so the all-new virtual platform featured high-powered, on-demand content; the flexibility to participate from anywhere in the world; and the ability to earn 75+ NETA CTD credits (7.5+ CEUs). PowerTest TV offered a more customizable conference experience than ever before and was a great success.
Realistically, I was thinking of 350 to 450 attendees at best, so I was pleasantly surprised to see nearly 400 new attendees — mostly technicians who would not normally have had the experience of attending a NETA conference. We actually set a new attendance record for PowerTest with over 600 attendees.
Q: What advice do you have for incoming NETA President Eric Beckman?
Blizard: I don’t have any advice for Eric other than to enjoy his time as President. I wish him the best.
“I have had the pleasure of working closely with Scott over the past two years as he served as President,” says NETA Executive Director Missy Richard. “Scott has an extraordinary passion for the association and the electrical testing profession. I am honored and blessed to have shared this time with him. He is not only a mentor who has deeply impacted me professionally and personally, but also a friend. His leadership and support — especially during the unprecedented challenges of the pandemic — were invaluable to me and this organization. Quite frankly, I don’t know that we could have navigated so successfully through the last 18 months without him. I look forward to continuing our work with Scott as he passes the torch to the next President.”
Scott Blizard Speaks at PowerTest 2020 Member Meeting
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