HIGHLIGHT | Quarterly Magazine
INNOVATION TEAM IN SYNC WITH ACTUAL DEVELOPMENTS IN T&D TECHNOLOGY
SAFER, SMARTER, GREENER
THE LAST INVERTER STANDING
No. 73 | July 2018
RESULTS OF TESTS OF AC CABLE CIRCUITS AFTER INSTALLATION
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 2,300 energy experts support clients around the globe in delivering a safe, reliable, efficient, and sustainable energy supply. We have over 90 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 E email@example.com I www.dnvgl.com/kemalaboratories Editorial staff Angela de Geest Photography DNV GL Fotostudio Alain Baars
Technical entrepreneurship In October last year we celebrated the 90 th anniversary of KEMA with a big conference in Amsterdam. For the occasion, her majesty the Queen, granted us the right to name the new High Power Laboratory in her honour: “The Queen Maxima High Power Laboratory”. On the cover picture, you can see the new name on the extended building. At the time of writing, the FIFA world championship football started in Russia – also with a grand opening. Of course, there are more similarities, for example here at our Laboratories we also have many different nationality customer teams working hard to have their equipment win the first prize as most teams work hard to get a golden certificate.
and distribution industry, we see a rapid introduction of new technology for monitoring and controlling existing technology, and with the growth of power electronics, maybe even replacement of some components. For these reasons we are continuously modernizing the capabilities of our Flex Power Grid laboratory. We work closely together with colleagues from the Research and Development Group of DNV GL - Energy, running joint industry projects, evaluating new technologies and developing standards. Furthermore, we of course also work with many customers on developing and testing their new innovative equipment.
Another similarity is the introduction of new digital technology. FIFA introduced the Video Assistant Referee helping the conventional referee team to enforce fair play in the game. In our transmission
Best regards, Jacob Fonteijne, Executive Vice-President KEMA Laboratories
KEMA Labs innovation team in sync with actual developments in T&D technology
The last inverter standing
Results of tests of AC cable circuits after installation
Complete Type Test
Testing activities Schneider Electric (Xiamen) Switchgear Equipment Co. Ltd. KEMA Type Test Certificate issued to Siemens Protection Devices Ltd., UK ZREW Transformatory S.A. recently tested their 40 MVA power transformer Ante Leco Metering Company (PVT) Ltd., Sri Lanka approval for single phase energy meter KEMA Type Test Certificates issued to Xi’an XD
Certification for fuses of testing capacity in High-Voltage Laboratory
KEMA LABS INNOVATION TEAM IN SYNC WITH ACTUAL DEVELOPMENTS IN T&D TECHNOLOGY
With the CIGRE conference about to kick off, some trends in the industry become more “live” than ever. KEMA Labs, in a pro-active way, has created an innovation team dedicated to developing test technology in order to deal with various developments in the industry. Most prominent is the emergence of renewables. Existing T&D products will become more compact, requiring less maintenance for offshore, lowpower frequency and even seabed applications. Here, of course HVDC kicks in. KEMA Labs has now demonstrated the testing of two technologies of HVDC circuit breakers for future HVDC grids, with more to come. HVDC transmission equipment is covered in our HVDC laboratory, where 320 kV cables are being tested now, and a HVDC GIS system is about to undergo a long duration experimental test. At distribution level, we have started to test large battery and PV inverter systems, even a complete 600 kWh storage system, thanks to the recent extension of our FlexPowerGrid Laboratory, read more on page 4.
Hardware-in-the-loop technology is essential when testing control and protection equipment that needs to act on complicated situations in a grid, simulated in our brand new Opal RT system. The Internet of Things is rapidly being introduced in the T&D component world, materializing as digital substation components that communicate and are controlled by digital data packages that are structured along the IEC 61850 methodology. New sensor technologies, like low-power instrument transformers are already being tested by us and at the same time installed in our laboratories to increase flexibility and better monitor DC and grid harmonics. The reliability of such smart sensors, being the interface between the real and the digital world, will gain considerable importance since
the emergence of “fake news” erroneous messages in the cloud will have an enormous impact. Environmentally, the advent of various SF6 alternative gasses will have a big impact. We performed tests on a switchgear containing such gases, and KEMA Laboratories will take the lead in a CIGRE working group on the impact of such gases on switching performance of HV and MV switchgear. But also the high-end supergrid components gain more attention. Several 800 kV transformers have been short-circuit tested recently, thanks to the investment in new generators and transformers. At the super current edge, ultra-high current generator circuit breakers of various technology regularly find their way to KEMA Laboratories.
DNV GL IN ENERGY
THE LAST INVERTER STANDING With the massive integration of renewables the power grid is becoming the new wild west. In this wild west landscape it is becoming more important to assure that the renewables also contribute towards the safe and reliable operation of the entire grid. One of the key components allowing for renewable energy sources to feed into the grid but simultaneously impacting the stability and operation of the grid are the power electronic inverters. Take solar energy for example: the photovoltaic or PV inverters are used to convert the DC output of a PV panel into an AC voltage and current that is compatible with the grid. At the same time, their control also impacts grid voltage and frequency dependent impedance having its effects scaling with the equipment power ratings. Early lifetime failure or reduced overall performance of such inverters can severely influence the return of investment for the owner or operator of such equipment, whilst malfunctioning under extreme conditions could lead to grid instability. To increase the level of confidence in the investment when operating such equipment for a long time, it makes sense to assess the long-term performance and quality of the PV inverter under all foreseen (worst case) operating conditions beforehand. In addition, PV inverters are - by grid code - required to remain electrically stable when operating during dynamic grid conditions and be robust enough to operate independent of a changing electrical landscape around it, for example when placed next to an energy storage unit or in an industrial environment with poor power quality.
Figure 1 - PV inverter under test at KEMA Laboratories (inverter placed inside the climate chamber)
KEMA Laboratories addresses these aspects by managing a Product Qualification Program that includes extensive laboratory-based inverter testing that extends far beyond just the minimal performance requirements. In this program, the performance of a PV inverter, for example, is assessed by a series of laboratory-based tests, which include amongst others an AC & DC envelope characterization, transient voltage and frequency response characterization, low irradiance performance assessment, maximum power point tracking efficiency measurement and energy harvest measurement taken during different weather profiles. All require sophisticated laboratory equipment for (real-time) AC grid emulation as well as PV panel emulation.
The electrical performance tests are followed by an intense reliability assessment of the inverter designed to identify the rate of deterioration when exposed to long-term (extreme) climate conditions. Such tests include a powered thermal cycling test, a powered high-temperature test (setup shown in figure 1 and results shown in figure 2) and powered low-temperature test. In the case of the powered high-temperature test, a PV inverter rigged with thermocouples on a few strategic places, is placed in an environmental chamber where the ambient temperature is raised to the maximum allowed operating ambient temperature of the inverter whilst the inverter is operated at its maximum power. It is then observed closely to see whether it continues to operate
500 Ambient cable entrance (°C) Ambient climate chamber (°C) Ambient power area (°C) Ambient below power area (°C) DC bus capacitor (°C) Output CM choke core (°C) Logic board processor (°C) Setpoint (°C) AC power (kW)
95 90 85
450 400 350 300 250
Figure 2 - High-temperature test of PV inverter (60°C). Note the power derating at high temperatures
in an electrically stable manner and that it safely reaches thermal equilibrium without damage, malfunction or introducing any type of failure or disturbance to itself or its surrounding system. The results from a typical high-temperature test are shown in figure 2. It shows at first a rapid rise of temperature when operating at rated power (125 kW in this case) followed by a predefined derating once the internal temperatures are expected to exceed safe operating values. Finally, a stable operating point is achieved where the inverter maintains a constant power output (80 kW) without overheating. The power conversion efficiency as well as the harmonic distortion produced is recorded throughout to assess any temperature influence there might be on the electrical performance of the equipment under test.
As if that was not enough the inverter is then subjected to a set of accelerated ageing based reliability tests. In this range of tests the PV inverter is subjected to several non-powered thermal tests, such as a thermal cycling, a damp heat and a humidity freeze test. Electrical tests before and after are used to assess the long-term reliability of the inverter. As we embrace a more electrified future, inverters such as these will play a more dominant role in our electrical power grid and actually define the integrity and quality of the overall system. With the comprehensive Product Qualification Program KEMA laboratories are prepared for every step of this journey, separating the good from the bad and the strong from the weak. As we traverse this road of testing we constantly ask ourselves: which inverter will be the last one standing?
DNV GL IN ENERGY
RESULTS OF TESTS OF AC CABLE CIRCUITS AFTER INSTALLATION
A test after installation is carried out to demonstrate the electrical integrity of the cable system as installed. After the cable system has been installed, a DC voltage “oversheath” test as well as an AC voltage test of the insulation is recommended in IEC 60840 and IEC 62067. Nowadays, the series resonant testing method is applied to realize the test after installation, which is widely accepted and reflected in CIGRE publication and standards. KEMA Laboratories routinely carries out such tests on site with their two mobile HV test trucks. Based on decades of experience the following tests in conjunction with an AC voltage test are recommended: partial discharge (PD) measurements, impedance measurement, contact resistance measurement, verification of cross-bonding and cable capacitance measurements. They give valuable information on cable circuits and they help utilities to determine what tests (voltage, duration) might be appropriate to give confidence in newly installed or replaced cable circuits.
The average failure rate is almost 10% across the whole voltage range (see figure). Circuits having voltage above 150 kV have the highest failure rate: 16%. The failure statistics give an indication of the test results; it cannot be used to draw conclusions on general performance of newly installed cable systems, because the various circuits have been tested with various combinations of test voltage and its duration. More information can be obtained from KEMA Laboratories recent position paper on Power Cable Testing. Tests after installation are carried out on a cable circuit already installed, mostly with all components (cable, joints, terminations) type/pre-qualification tested and immediately before energization. It is thus surprising, that still around 10% fails to pass the test at the requested voltage stresses. 16% 14% 12%
This article summarizes the results of 1291 tests after installation on AC cable circuits over a 21-year period (1997-2017) by KEMA’s on-site testing team. For this summary, tests are grouped in three voltage ranges: U ≤ 110 kV, 110 kV < U ≤ 150 kV and U > 150 kV. More than half (58%) of all tests were performed on cables (110 kV < U ≤ 150 kV); cables in the range (U ≤ 110 kV) comprise almost one third (31%) of the total tests. Only a relatively small number of all tests (11%) were on cables above 150 kV because of the generally limited number of projects compared to the lower voltage ranges.
10% 8% 6% 4% 2% 0% Total
U ≤ 110 kV
110 kV < U ≤ 150 kV
U > 150 kV
Failure rate at testing cable circuits after installation
H. He, E. Pultrum, R. Smeets, “Position paper: power cable system testing ensuring the reliability of power transmission and distribution”, DNV GL KEMA Laboratories, April 2018 
Complete Type Test Certification for fuses Fuse-application is a long standing invention that continues to guarantee crucial protection in all electrical engineering applications. It can be assumed to be the last protection barrier. An extra reason to test fuses thoroughly. The IEC 60282-1 standard covers all types of high-voltage currentlimiting fuses of nominal voltage over 1000 V. This standard provides the series of type tests for the high-voltage fuses which verify that a particular design satisfies specified characteristics under normal or fault conditions. This verification is a crucial action to guarantee the safety of both people and the network. KEMA Laboratories Prague is able to offer Complete Type Test certification to their clients according to IEC 60282-1: Dielectric tests cl. 6.4 Temperature-rise tests and power-dissipation measurement cl. 6.5 Breaking tests cl. 6.6 Test for time-current characteristics cl. 6.7 Test of strikers cl. 6.8* Thermal shock tests cl. 7.3 (special test)* Waterproof test cl. 7.5 (special test)* Pre-arcing temperature rise test cl. 7.6.2 (special test)* *New accredited tests developed in KEMA Laboratories Prague as result of a year of study and design of new equipment.
Extension of testing capacity in High-Voltage Laboratory In 2009 the High-Voltage Laboratory in Arnhem moved to a completely new building next to the High-Power Laboratory. This new building is much bigger and better equipped than the former High-Voltage Laboratory. Since then we have seen an increase in testing requests of different MV and HV components, such as cables and cable systems, power transformers, instrument transformers, all kinds of switchgear and others. In the last few years, the increased business demand for the High-Voltage Laboratory has resulted in quite some challenges for the planning department. The result of this was that a new test location was built for testing HVDC equipment (this having being operational for some years already). In addition, the old location of the High-Voltage Laboratory has been brought back into operation again since the end of 2017. With this expansion, we have increased the testing capacity of the High-Voltage Laboratory for both dielectric tests and temperature-rise tests on several components and are therefore able to be more flexible in scheduling the tests.
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SCHNEIDER ELECTRIC (XIAMEN) SWITCHGEAR EQUIPMENT CO. LTD.
Schneider Electric (Xiamen) Switchgear Equipment Co., Ltd. has successfully tested their 12 kV 50 kA 50 Hz circuit-breaker with Electrical Endurance Tests. This circuit has a making current of 7,5 kA and a breaking current of 1250 A with a cos oI of 0,3. With this setting we have performed the close open operation (40 operations per hour) 1300 times. KEMA Laboratories will issue a KEMA Test Report on clients instruction with a reference to CST 74.C.022.04.
KEMA TYPE TEST CERTIFICATE ISSUED TO SIEMENS PROTECTION DEVICES LTD., UNITED KINGDOM
The numerical 3 phase line differential protection relay, type 7SR18, of Siemens Protection Devices Ltd., United Kingdom, has successfully completed the type test programme in accordance with IEC 60255-1. The test programme included both functional performance and hardware/environmental tests. Samples from two different manufacturing locations are included. The KEMA Type Test Certificate has been issued.
ZREW TRANSFORMATORY S.A. RECENTLY TESTED THEIR 40 MVA POWER TRANSFORMER
ZREW Transformatory S.A., Poland successfully tested three phase power transformer 40 MVA, 110 kV/23 kV with tertiary winding at KEMA Laboratories Prague. The routine tests and out-of-tank inspection were successfully done at the ZREW factory in Poland by KEMA Laboratories’ Inspection Services. With this result they are entitled to receive the Type Test Certificate of Short-Circuit Performance as per IEC 60076-5.
ANTE LECO METERING COMPANY (PVT) LTD., SRI LANKA APPROVAL FOR SINGLE PHASE ENERGY METER
Ante Leco Metering Company (PVT) Ltd. in Sri Lanka developed a class 1 electronic single phase energy meter for Ceylon Electricity Board and Lanka Electricity Company, the two main electricity utilities in Sri Lanka. The energy meter was type tested according IEC 62052-11 and IEC 62053-21 standard with an increased impulse voltage level of 12 kV. The KEMA Type Test Certificate has been issued.
KEMA TYPE TEST CERTIFICATES ISSUED TO XI’AN XD
In the first half of the year we tested a 550 kV SF6 Gas Insulated Switchgear, manufactured by Xi’an XD at KEMA Laboratories in Arnhem. The GIS assembly consisted of a circuit-breaker, disconnector, earthing switches and bushings. The tested objects successfully fulfilled all the short-circuit performance, capacitive current switching, dielectric and temperature rise requirements as mentioned in IEC 62271-100/IEC 62271-203 and their relevant product standards. Because the tests were successful, we were happy to issue KEMA Type Test Certificates.
HighLight is the quarterly newsletter of KEMA Laboratories.