Increased operation reliability of HV apparatus through PD monitoring

In this article, the challenges with continuous partial discharge (PD) monitoring of HV power cables, transformers and rotating machines are presented. A versatile partial discharge monitoring system is described that is applicable to different high-voltage equipment and can be connected to a vast range of sensors. In the case of power cables, the paper deals with continuous monitoring of a 420 kV XLPE cable system in an underground tunnel. The method that can simultaneously detect and locate partial discharges at all accessories is described. In the case of transformers, partial discharges are measured at the bushing measuring taps and in the UHF range with an antenna installed within the transformer tank. The experience gathered from PD monitoring to assess the condition of turbo and hydro generator stator winding insulation is also presented in the paper. The advanced features for noise and PD defects separation based on synchronous multi-channel techniques are shown. Case studies are included, which indicate that critical defects can be detected early and their evolution can be monitored.