NKT wraps up first in-house TOV testing of HVDC cable systems

Denmark-based NKT has completed the first in-house temporary overvoltage (TOV) test sequence of high-voltage DC cable systems, said to represent an important technical milestone that increases the reliability of cable systems needed for the green transition.

NKT reported on 21 June that it had executed its first customer-compliant TOV testing sequence, utilizing new in-house testing capabilities for its high-voltage power cable systems.

According to the company, related to the new CIGRE recommendation, e.g. CIGRE TB 852, on Special TOV test waveforms, its 525 kV HVDC cable system has passed surge and extended overvoltage testing. 

The TOV is said to summarize two new types of stress wave shapes on the cable which were not previously tested for, including damped oscillation transient voltages with different frequencies, and long (few hundred milliseconds) temporary overvoltage. 

“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,” said Anders Jensen, CTO of NKT.

“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.” 

NKT notes that the milestone shows its commitment to future-proofing the technology and better supporting the continued rollout of a DC power grid in Europe. 

NKT last month revealed it was planning to boost its high-voltage power cable business with a €1 billion investment in a new factory in Sweden and a power cable vessel.

The move is said to be driven by growing demand for HV power cables, strong order intake, and a record order backlog of more than €7 billion at the end of 1Q 2023.