Breakdown of Air-Polymer Composite Insulation due to Partial Discharge and Influence of Thermal Insulation

Abstract

Breakdown characteristics of air-polymer composite insulation under repetition of partial discharge have been studied using needle-plane electrode system. The purpose of this study is to clarify the effect of repetitive partial discharges and thermal properties of polymer on breakdown mechanism of air-polymer composite insulation under the application of square pulse voltage. The experiments were also performed by inserting a thermal insulating film between an electrical insulating film for breakdown and the plane electrode. The number of pulse voltage up to breakdown (NBD) was measured with variation of pulse frequency. With increasing the pulse frequency, the sudden drop of the NBD appeared over a threshold of pulse frequency. The threshold frequency became lower by inserting thermal insulation. The results observed with thermograph show that surface temperature was increased with increasing pulse frequency and increased more remarkably around the threshold frequency. With insertion of the thermal insulating film, the surface temperature rise appeared at lower frequency. These results on the breakdown characteristic and the thermal characteristic were successfully explained based on the numerical analysis of the thermal circuit.