Online PD testing on a 1,5 km long 22 kV subsea cable
We recently performed condition assessment on a number of 22 kV cables for one of our customers. At one of the subsea cables we discovered critical internal discharge. The PD was measurable at both ends of the 1.5 km long cable, even though the cable was armored.
In the analysis below you find the measurements from both sides. Due to the attenuation and propagation effects, the FFT is lower and the PD wave is slower at one of the sides.
Through the analysis we were able to establish that origin of the PD is not the termination, but in the cable at the transition between land and sea, approx 50 meters from the termination.