STUDY OF SURFACE DISCHARGES ON CABLE TERMINATION

Summary

Cable system breakdowns are mostly caused by some defect on cable terminations or joints. One of critical failure occurred in a photovoltaic power plant located in the Czech Republic where the cable channel with cable terminations was exposed to poor environmental conditions. The large amount of dust was accumulated on the cable surface and busbar components. The penetrating humidity, into the cable channel, condensed on its surface when the cable was unloaded. Probably, this effect was the reason of surface discharges initiation and propagation on the cable terminations. The insulation material of terminations was long-time stressed and finally the rapid degradation was accelerated. The breakdown occurred at the end and the high fault current caused the total destruction of medium voltage devices in the cable channel and in the substation. This accident led to the intensive investigation to find reasons of this serious fault. The experimental measurement in the high voltage laboratory at the Czech Technical University in Prague was performed to study a discharge activity at AC voltage of power frequency. Cable terminations were covered by layer of a mixture of water and dust. The inception voltage of discharges and flashover voltage were determined for two types of cable terminations and various parameters of pollution layer. The leakage current and voltage waveforms were recorded during high voltage tests for possible further analysis of discharge activity.

Additional informations

Authors

Zhaoliang Gu, Prochazka Radek