Influence of swarming pulsive microdischarge on tree degradation

摘要

Partial discharge is one of the causes of degradation in insulating polymer materials subjected to high voltages. Of particular importance in this case is the degradation which occurs due to partial discharges inside gaps, such as voids inside an insulator. Although this subject has already been studied by many researchers [1.2] and various countermeasures have been proposed, there is at present no proven technology to cope with this problem, and much work needs to be done before it is clearly understood. A type of partial discharges not yet well understood is the so called SPMD (swarming pulsive microdischarge), which seem to appear just before breakdown. The existence of SPMD is related essentially to the existence of voids in insulation [3]. Although no discharge pulses have been recorded during the interval between voltage application and tree inception, it is possible that such phenomena are due to the insulation degradation progressed in the voids. The sensitivity of the PD detector apparatus used might also have been a reason for not detecting the small discharges.