HIGHLIGHT | Quarterly Magazine
DNV GL PARTICIPATES IN PANEL FOR HIGH ENERGY ARC FAULTS
SAFER, SMARTER, GREENER
SHORT-CIRCUIT TESTING OF LARGE POWER TRANSFORMERS
No. 70 | July 2017
TRANSFORMER RECTIFIER TESTING
DNV GL IN ENERGY
Highlight is the quarterly newsletter of KEMA Laboratories. KEMA Laboratories are part of DNV GL – Energy. Our expertise spans from proficiency in onshore and offshore wind power, solar, conventional generation, transmission and distribution, smart grids, and sustainable energy use to innovative involvement in the energy markets and regulations. Our 2,500 energy experts support clients around the globe in delivering a safe, reliable, efficient, and sustainable energy supply. We have over 80 years of experience in testing, inspections and certification – and the KEMA brand is renowned globally as the gold standard for quality. Our Testing, Inspections and Certification (TIC) activities are internationally recognised for their quality and integrity. Our main product is the KEMA Type Test Certificate, which is issued if a component successfully passes an internationally recognised type test program in our laboratories. For our customers, the award of a KEMA Type Test Certificate is a respected indicator of the reliability and safety of their products. KEMA Laboratories are located in the Netherlands, USA, and the Czech Republic. Editorial department DNV GL – Energy KEMA Laboratories P.O. Box 9035 6800 ET Arnhem The Netherlands T +31 26 356 32 22 E email@example.com I www.dnvgl.com/kemalaboratories Editorial staff Angela de Geest Photography DNV GL Fotostudio Alain Baars
KEMA Laboratories - USA: a unique facility in the North American Power Industry KEMA Laboratories - USA, located in Chalfont, Pennsylvania, is the largest high power testing laboratory in the Americas offering a full suite of high power/high voltage testing services. These services are provided in accordance with ISO 17025 Accreditation and offer KEMA Certification testing to IEEE and IEC Standards, accredited UL Third Party Testing, and independent test laboratory testing for product development for every major OEM in the world. The lab also offers simulation testing for transmission, distribution & generation operating problems, comparative performance analysis of manufacturer’s equipment, and many other customized high power/ high voltage testing programs for the North American power industry. Our lab is regularly involved with interesting and cutting edge projects and serves clients across the power industry.
Sincerely, Tomasz Stefanski Director KEMA Laboratories - USA
DNV GL participates in panel for high energy arc faults
Short-circuit testing of large power transformers
Transformer rectifier testing
studies Laboratories - USA introduces new multitap reactor
If you want to learn more about our laboratories, please contact us at firstname.lastname@example.org or call at +1 215 822 4231 to speak with one of our experts.
Currently, we are working with the US Nuclear Regulatory Commission on the destructive effects of high energy arc faults in electrical equipment using aluminum as a current conducting material (read more about this on page 3).
Our facility has been providing high power & high voltage testing services for every major equipment manufacturer in North and South America for 27 years. Today, the lab is part of DNV GL (formerly KEMA), a global leader in independent testing, certification and technical advisory services to the power, oil & gas, renewables, and maritime industries. The Chalfont facility is a part of a global network of KEMA Laboratories, including facilities in Arnhem, the Netherlands with testing equipment up to 800 KV, and Prague, Czech Republic.
DNV GL PARTICIPATES IN PANEL FOR HIGH ENERGY ARC FAULTS In February 2017, Tom Stefanski represented DNV GL - for the first time - on the Phenomena Identification and Ranking Table (PIRT) Expert Panel for High Energy Arc Faults (HEAF) at a conference organized by the US Nuclear Regulatory Commission.
The conference took place at the NRC Headquarters in Rockville, Maryland with the intent of assessing and documenting the importance of phenomena in characterizing HEAF events, including the current state of knowledge and the ability to gather more data on these phenomena. The panel featured global representatives from Japan, Germany, France, Korea, and the USA. The Phenomena Identification and Ranking Technique (PIRT) is a systematic way of gathering information from experts on a specific subject, and ranking the importance of the information to meet a decision-making objective. This technique has been applied to many nuclear technology issues, including nuclear analysis, to help guide research or develop regulatory requirements. During discussions, scenarios were developed spanning plausible range of HEAF events, while still staying within the scope. The scenarios were mainly focused on the HEAF source equipment as opposed to targets.
KEMA Laboratories – USA was recognized as the only lab capable of conducting HEAF tests at the level of power generated in nuclear power stations. As conversations in the panel progressed, members were eager to learn more about further testing and began dialogue around the next stages of testing for NRC. Discussions indicated that 2018 NRC testing would likely be performed at DNV GL’s KEMA Laboratories – USA.
DNV GL’s primary goal was to share our expertise and contribute as a subject matter expert, advise the panel members on technical matters, as well as answer any relevant questions throughout the panel. A significant part of the meeting was related to the report “High Energy Arc Fault Events (HEAF) Experimental Results” based on tests performed at KEMA Laboratories – USA. This report can be viewed at www.oecdnea.org/nsd/docs/2017/csni-r2017-7.pdf.
This conference allowed NRC members to learn more about our global capabilities, opening up further interest and opportunities for DNV GL to participate in future discussions around testing preparation, procurement of materials, analysis of test program, and decision tree. If you would like to learn more about our HEAF testing capabilities, please contact us at email@example.com or call at +1 215 822 4231 to speak with one of our experts.
DNV GL IN ENERGY
SHORT-CIRCUIT TESTING OF LARGE POWER TRANSFORMERS Power transformers are the most expensive pieces of equipment in power sytems. Interruption of service of transformers need to be avoided at all time, given the enormous consequences. International studies have indicated that the failure rate of transformers is around 0.6%, with converter transformers failing up to 5%. In depth study reveals that a major portion of these failures (up to 20%) is directly related to short-circuits. During a short-circuit, the large currents involved lead to severe mechanical forces and stresses in the transformer windings, which may become deformed when the structural design of the transformer is not adequate. Today, there are two methods to verify whether a transformer survives a shortcircuit. The first one is design review, in which third-party consultants check calculation results of forces and stresses and compare these with critical values based on tests or based on internal manufacturer’s rules. Design review is based on calculation results of idealized, homogeneous structures, it does not cover transient phenomena, it excludes a number of key subcomponents and it is not embedded in a strict quality surveillance system. The second verification method is “short-circuit testing”, in which the complete transformer is subjected to real short-circuit current and thus to the same stresses as would occur in service.
Short-circuit testing is the only complete verification method that can withstand the testing capability of power transformers. In the last few years, KEMA laboratories extended its labs to deal with increasing requests for transformer short-circuit tests. Today, the lab has six 2250 MVA short-circuit generators and ten short-circuit test transformers (reaching a total of 550 kV), allowing our experts to test power transformers with voltage up to 800 kV and power up to 1000 MVA (based on three-phase transformer banks). To date, there have already been several 800 kV class power transformers that were tested. In spite of the wide application of advanced calculation methods, 20-30% of transformers submitted to a shortcircuit test fail to pass the standardized short-circuit tests. The results suggest a tendency of the highest initial failure rates for the highest ratings: the failure rate of the largest transformers (> 300 kV or > 200 MVA), with about 100 tested, is roughly 30%. These statistics are based on a population of 320 power transformers of 25 MVA and above in a 21+ year time span. The most common reason for failure is a reactance increase beyond the limit set by the IEC 60076-5 standard, which indicates an unacceptable internal deformation.
In a number of cases, however, unexpected events are triggered by short-circuit current which are outside of the “usual” failure modes, like breaking of a bushing, oil spill, internal flashover etc. The rate of failure to pass a shortcircuit tests hardly changes over time, which may be related to the high pressure on costs that lead to design close to the margin. Short-circuit tests are recognized to be non-destructive. A key asset of KEMA Laboratories is the avoidance of major damage in case of a malfunction inside the transformer. High-speed protection combined with very fast circuit breakers guarantee survival of the transformer and the possibility to identify the root cause of a failure in a test. In regard to grid-supplied test stations, switching must be done by slow circuit breakers which allow a fault inside the transformer to become fatal for the equipment. In the past, utilities mainly relied on the selection of trusted manufacturers to secure short-circuit capability of their transformers. However, many users are now asking for tests on critical units or prototypes of series of identical units. This may be because a long-term relationship between the purchaser and a single manufacturer is less achievable due to increasing deregulation.
The high failure rate in service due to poor short-circuit performance before the year 2000 (0.4% in France, 0.35% in Italy, 1.2% in Turkey, China: 84% of all internal failures was due to short-circuit, India: over 80% of the failures were caused by winding displacement) led to the adoption of short-circuit testing as a method for quality improvement. By now, it is generally understood and supported by CIGRE that “short-circuit testing is the most comprehensive solution because all parts are verified”. Both the positive and negative experiences KEMA Laboratories has achieved through testing have been very informative and has helped to improve overall testing. Testing can quickly identify critical areas which in most cases can be resolved with simple changes at a relatively low cost - and most importantly, benefit long-term reliability. To learn more, read our latest article in Transformers Magazine titled, “Shortcircuit withstand capability of power transformers - Part I and Part II”.
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TRANSFORMER RECTIFIER TESTING
Real-world testing to give you and your customers utmost confidence A single failed transformer rectifier can shut down a whole power system and bring vital infrastructure to a halt. At KEMA Laboratories – USA, we test transformer rectifiers under the most realistic conditions possible so you can have maximum confidence in their performance in the real world. Transformer rectifiers are a key component of many applications such as transit systems. It is vital that they operate reliably. Any failure resulting in interruptions to service will frustrate customers and can lead to financial penalties. While the damage to components can be fixed, the damage to a company’s reputation is potentially irreparable. Service providers need to be confident in a transformer rectifier’s reliability before they install it into their system.
For new and existing systems Transformer rectifiers are a very mature component type, but each application has its customized technical specifications and even minor changes in design, assembly or choice of materials can impact a product’s reliability. So whether for a new system or to replace existing parts, transformer rectifiers should be properly tested before being installed, even if they are similar to or based on a previously qualified design.
Testing under real-world conditions Third-party, industry-standard testing is the key to that confidence. DNV GL’s real-world testing provides independent evidence that a transformer rectifier will perform as required time after time. Thanks to the state-of-art facilities at KEMA Laboratories – USA, we are able to test transformer rectifiers under the most realistic conditions possible so you can be assured how they will perform in the field.
Testing capabilities No rests between tests We can test transformer rectifiers against all relevant standards and also offer tests that go beyond the standards. In fact, we are the only US lab that can perform overload (RI-9) and shortcircuit tests in one sequence. So as the component does not get the time to cool down, the final high-current short-circuit test takes place at a realistic operating temperature.
This guarantees a much more accurate simulation of a fault resulting from heavy activity. What’s more, our testing does not age the insulation. So the tested system can be installed and used after certification. Transformer rectifier tests Tests can be carried out on: Rectifier-transformers: liquid-filled or dry-type transformers Rectifiers: diode or thyristor-controlled designs The following list covers many of the tests available at KEMA Laboratories. Transformer-rectifier assembly Either with or without a bus duct connecting the transformer to the rectifier Harmonic analysis test Audible sound-level test Efficiency, displacement power factor, and voltage regulation tests Current balance test Temperature rise test RI-9 overload test Short-circuit current test Transient-surge voltage test Rain test
Rectifier only Dielectric test Short-circuit test (six pulse only) Temperature rise test (six pulse only) Current balance test (six pulse only) Customer-specific tests are available upon request Customer-specific tests are available upon request Transformer only Commutating resistance and reactance Harmonic analysis test Temperature rise tests Cold-resistance of transformer windings Hot-resistance of transformer windings No-load and load loss tests Impedance test Short-circuit test Impulse test Partial discharge (up to 40 kV) Other dielectric tests Ratio and polarity tests Audible sound-level test Induced voltage (400 Hz) test Winding insulation resistance test (up to 15 kV) Other (specific requests are also possible) Your partner in understanding standards Industry standards are essential for credible certification. As an industry, it is crucial that we ensure standards continue to meet the evolving needs of all parties. Transformer rectifiers are governed by multiple standards and their requirements can be technically complex. DNV GL is an ideal partner to help you understand the standards that are relevant to you. Deep involvement in the entire power market gives DNV GL real understanding of these needs. We are also active in helping define standards. Early access to new standards allows us to ensure our KEMA Laboratories test facilities and capabilities meet, and surpass, future requirements. It also means you can get earlier insight into how the requirements and implementation of new standards impact your business. Contact us today to arrange a dedicated standards workshop for your company: firstname.lastname@example.org
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CASE STUDIES HIGH PRESSURE COMPRESSOR REPLACEMENT In June 2017, we successfully replaced our 40-year-old Worthington high pressure compressors with two new Bauer B-Series Compressors. The high-pressure compressors serve a big role in test operations by producing the air that the make switches use to operate. Without functioning high pressure compressors, testing would not be able to take place. Dave Heller, Dan Kauffman, and Mike Caselle (pictured from left to right) worked together to ensure the new compressors were installed and functioning seamlessly before decommissioning the old compressors, resulting in zero down time. This ensured a seamless transition and no down time for test operations. The new compressors are automated by PLC control and work on a lead/lag operation scheme. This means that one compressor is running in the lead position while the other is at rest in the lag position. These positions will rotate after a given number of running hours. In addition, the PLC will keep track and alert us of the preventive maintenance requirements based on the run-hours logged by each compressor.
SHORT-CIRCUIT CURRENT WITHSTAND TESTS FOR GMTS, BRAZIL
GTMS Equipamentos Elétricos Ltda. (Brazil) has succesfully performed momentary and short-time short-circuit current tests on their SPV – 245 kV High Voltage Switch at KEMA Laboratories - USA. The test parameters were based on IEC 62271-102. The tests were witnessed by both GTMS personnel and their client Copel Geração (Brazil). The bus loop required for this test and pictured here was setup in Cell 9, the largest test cell at KEMA Laboratories - USA.
KEMA Laboratories - USA introduces new multitap reactor KEMA Laboratories – USA is proud to announce the purchase of a new multitap current limiting reactor. The reactor was designed and constructed to achieve very fast recovery voltages required during tests on fuse cutouts and will also be used as a load bank during specialized test programs. The reactor design allows easy changes maximizing testing efficiency. At KEMA Laboratories we are always open to improvements of efficiency and assistance in addressing customers’ challenges. Our engineering team shares their testing and electrical expertise when seeking solutions to these challenges providing value added services to all our clients. The purchase of the new reactor is a result of customer feedback requesting the expansion of our capabilities. The reactor will allow for quicker and more efficient setups for tests on all fuse cutout ratings presently used in North and South America. Customer feedback is important to us. We respond to all feedback and look forward to improving and expanding our capabilities for our customers and the market. Moving forward, we are looking forward to new challenges, test programs, engineering assistance, and providing our customers with the best quality testing services.
Introducing James Mack KEMA Laboratories is committed to growing market awareness and developing business opportunities within the utility segment in North America. We warmly welcome James Mack who has joined KEMA Laboratories as a Sales Executive based in Chalfont, Pennsylvania, USA. James has a Degree in Mechanical Engineering and has held various sales roles calling on utilities and power generation plants for the past 15 years. James can be reached at KEMA Laboratories - USA at email@example.com, +1 215-822-4270.