Quantitative analysis of swarming pulsive microdischarges by using very low frequency voltage application

Abstract

AbstractPartial discharge (PD) degradation phenomena is one of the most important factors to decide the performance and the lifetime of the high voltage apparatus. During PD degradation tests of an epoxy specimen with an internal void, PD often change to a large number of very small PD known as swarming pulsive microdischarges (SPMD). Because the appearance of SPMD is concerned with the degradation of the insulating materials, the insulation diagnosis with the detection of SPMD becomes possible. However, SPMD cannot be detected with the conventional PD Detector because the PD magnitude of SPMD is too small. The computer‐aided partial discharge analyzing system (CAPDAS) has been developed to detect and analyze the SPMD. Furthermore, a new PD parameter, the SPMD ratio has been introduced for quantitative analysis of SPMD. In this paper, the time variation of SPMD characteristics of a CIGRE Method‐II specimen are investigated by using the CAPDAS. Further, the effect of the frequency of the applied voltage on SPMD is also investigated at 60 Hz and a very low frequency of 0.1 Hz. As a result, the comparison of PD magnitudes measured at 60 Hz with those at 0.1 Hz enables a quantitative analysis of SPMD characteristics to be possible by using only the conventional PD detector.