Recently, KEMA Labs (CESI’s Testing, Inspection and Certification Division) has carried out the first TOV (Transient Over Voltage) test on a 525kV DC Cable System, manufactured by Prysmian Group R&D. This new and important goal for the HVDC Cable Sector has been reached in our KEMA Labs Mannheim HVDC Laboratories.
Due to the importance of such a ground-breaking project, we have interviewed Heiko Jahn, KEMA Labs Principal Engineer and Special Projects Coordinator, in order to go deeper into the several steps that led to the project’s successful completion. Below, you can find Mr. Heiko Jahn’s full interview.
KEMA Labs has carried out the first TOV (Transient Over Voltage) test on a 525kV DC Cable System. Can you tell us about your role in this great achievement?
I have been contacted already in 2019 to start an evaluation if testing with special waveforms could be provided by KEMA Labs. Starting with numerical simulations to find a test circuit in 2020 and down-scaled laboratory tests to prove the general feasibility in 2021, I have prepared the set-ups for the full-scale tests in 2022, and I have operated these tests on a 525 kV DC cable arrangement.
What does this test mean for the cable systems sector?
Testing with such special waveforms is not yet part of the test standard IEC 62895. But CIGRÉ Technical Brochures 852 and 853 already contain such tests. With the successful tests in the KEMA Labs in Mannheim we can give the manufacturers and the TSOs the certainty that such tests can be carried out in a regular HV laboratory with only small additional investments. Therefore, we can expect that requests for such tests will increase in the future.
This test was born from a solid collaboration between KEMA Labs and Prysmian. Do you think it will open the doors for similar projects in the future?
This collaboration has proven a solid confidence between Prysmian and KEMA Labs. We could show to Prysmian that KEMA labs is a reliable partner who supplies technical expertise and customized solutions. Vice versa Prysmian supported us with technical advice and short response time in our communication. Such a good collaboration exists also in Milano since many years and therefore, we can expect that it will be continued with new projects, also in the future.
What test parameters were fulfilled during the tests?
In fact, we have performed 2 different tests. While the first one was an oscillating discharge test, i.e. the discharge of the cable from operation voltage 525 kV to zero, the second one was a transient overvoltage test, where a transient overvoltage was superimposed to the operation voltage which reached a peak of 1.6 x 525 kV for the unipolar test and -0.6 x 525 kV for the test with opposite polarity. The frequencies for the oscillating tests were expected to be below 400 Hz (low-frequency test) and between 5700 Hz and 8000 Hz (high-frequency test). For the transient overvoltage test the main difficulty was the expected long time for the discharge, which shall exceed 100 ms. Introducing a high-voltage rectifier to the test circuit we were able to fulfill also this request and to offer a reliable solution.
Finally, what does this achievement represent for the KEMA Labs facility in Mannheim?
The KEMA labs facility in Mannheim is one of the smallest if we compare the headcount. However, this achievement proves that also in this small facility we have the power to develop technical innovation, basing on our expertise and on the experience with dielectric testing. Additionally, it confirms, that the decision of the management to install the HVDC laboratory in Mannheim, 10 years ago, was the right step.
Heiko Jahn is principal engineer and special projects at KEMA Labs FGH Engineering & Test GmbH, Mannheim (Germany). Since mid-2020, Jahn works as project coordinator for Central Europe. He has worked since 2006 at FGH Engineering & Test GmbH, initially as head of High-Voltage Test Laboratory and then as head of High-Voltage and High-Power Test Laboratory, platform manager of Mannheim Platform and principal engineer and special projects. Jahn has been a member of CIGRÉ WG A3.18 from 2003 to 2006. He previously worked at Siemens AG and has a doctor degree in engineering, Dresden Technical University, Germany.
If you want to know more about the first ever TOV Test on a 525kV DC Cable System, as well as other ground-breaking projects and achievements in the TIC sector, read our latest issue of Testingly.