On the ageing evaluation of multistressed corona suppressing systemby partial discharge analysis

摘要

The authors describe a procedure for evaluating the performance ofna corona suppressing system (CSS) exposed to severe environmentalnconditions. The test results presented confirm the validity of thendiagnostic technique based on partial discharge amplitude distributionn(PDAD) analysis for testing insulation ageing conditions. The adoptednmultistress ageing procedure seems to be quite severe when applied tonCSS. The experimental results suggest some improvements of the specimensnto use for the test: complete coils are preferred to insulated bars, andnstainless steel should be used for the supporting structure. The PDADndiagnostic tool was found to be very suitable and sensitive. At thenfirst step of the ageing, small-magnitude partial discharges inside thengroundwall can be detected. Then, it is possible to follow the growth ofnsurface phenomena, which start at the external part of the CSS and, innthe final stage of ageing, cause slot discharges