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NKT successfully completes first inhouse TOV test sequence of high-voltage DC cable systems

Jun 21, 2023

NKT takes temporary overvoltage (TOV) test from a theoretical hypothesis to proof-of-concept inhouse and successfully completes its first test sequence – an important technical milestone that increases reliability of cable systems needed for the green transition.

With current and future demand on sustainable energy sources growing exponentially, the pressure on reliable high-voltage cable systems is constantly increasing. As a result, international standardization communities are driving  discussions around tests to ensure future cables can withstand the pressures of increased stress and overvoltage scenarios. 
NKT has successfully executed its first customer compliant TOV testing sequence, utilizing new inhouse testing capabilities for its high-voltage power cable systems. This milestone shows NKT’s commitment to future-proofing the technology and better supporting the continued rollout of a DC power grid in Europe. 
Anders Jensen, CTO, says: 
“The completion of these tests demonstrates the robustness and high reliability of our HVDC cable systems even under transient events at the highest voltage levels. This project was a great example of NKT pushing technological boundaries to support customer requirements. From taking a theoretical hypothesis all the way to proof-of-concept was a challenge we were proud to take on and believe it is an important technical milestone that in the long run will support reliable cable systems for the green transition.” 
525 kV HVDC cable system meets customer expectations
Related to the new CIGRE recommendation, e.g. CIGRE TB 852, on “Special temporary overvoltage test” (TOV) waveforms, NKT’s 525 kV HVDC cable system has successfully passed surge and extended overvoltage testing. The TOV summarizes two new types of stress wave shapes on the cable which were not previously tested for; damped oscillation transient voltages with different frequencies, and long (few hundred milliseconds) temporary overvoltage. 
NKT is the first cable manufacturer to have inhouse capabilities to generate all types of temporary overvoltage at the highest commercial levels in its own high voltage laboratory. NKT has developed and invested in test equipment that allows the generation of long TOV curves with special features such as pre-plateau overshoot and enhanced discharging at the end of the plateau. 
The completion of these initial tests and the equipment will help NKT to continue delivering quality HVDC cable system technology for its customers
Pelle Fischer-Nielsen
External Communications Officer
Pelle Fischer Nielsen