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. This new and important goal for the HVDC Cable Sector has been reached in our KEMA Labs Mannheim HVDC Laboratories.
The long distance between renewable energy sources generation centers and the main power networks, as well as the need to transport the energy with the highest efficiency, with low losses, is driving increasing adoption and investments on HVDC power transmission infrastructures.
The growing integration of extruded HVDC cables into the energy transmission system raises new questions regarding transient failure voltage waveforms and their simulation in the laboratory.
In this respect, immediately from the first simulations performed by the TSOs in 2018, it was found that the IEC and CIGRE standard requirements were not sufficient to cover cases of dangerous transient waveforms in growing DC networks. Some TSOs, engaged in the transport of electricity from offshore wind farms in the North Sea and the Baltic Sea decided to verify the greater ability to withstand electrical transients of 525kV DC cable systems, which occur in HVDC Schemes such as during pole to ground fault, pole to pole fault, AC side faults, etc.
Early simulations revealed that transient overvoltage stress can occur on the cable. In the event of an earth fault in one polarity, the voltage in the other polarity can rise to a value between 1.7 and 2 p.u.
After the computational simulations, the first TOV has now been officially performed for a real Cable System Loop consisting of 2 External Terminations, 2 joints and the DC cable, produced by Prysmian Group.
If you want to know more about this specific test and KEMA Labs services, feel free to reach us through the contact form in the dedicated Cables and Accessories Page.