Non-destructive condition assessment on a 60 kV PILC subsea cable

A few weeks ago, Neka performed condition assessment on a 1.7 km long subsea cable of the type OKRA 50CU 60 kV PILC from 1960. A total of 4 single core cables were tested, 3 phases + 1 spare phase.

None of the phases showed signs of aging or spot-weakness, neither at the partial discharge (PD) diagnosis or the TanDelta (TD) diagnosis. We had a small increase in PD activity at phase L3. The activity was located to originate from the opposite end and was a result from dust on the external surface of the termination.

The TanDelta diagnosis, which indicates how the insulation is aging, shows stable and even values between the various voltages, as well as between all phases. Even the reserve phase, which has been mainly voltage-free, has the same TD values as the "used" phases. All in all, this indicates that the insulation of these cables is in good condition, even after 60 years in service.