NKT has successfully executed its first customer compliant temporary overvoltage (TOV) testing sequence, utilising new inhouse testing capabilities for its high-voltage power cable systems.
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 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.