Analysis of Anti-interference for HV Capacitor PD Measurement at DC

Abstract: In order to reduce the effect of interference and improve the anti-interference performance in HV capacitor PD test at DC, the paper presents the analysis of interference existing in the test circuit from the aspects of generation mechanism, reason, source and category. After taking anti-interference measures including adding isolating transformer, filter and independent earth wire, the input voltage waveform gained by oscilloscope is more smooth. The Q/N curve also indicates that the number of discharge reduces and the noise amplitude becomes smaller.  

Key words: Partial discharge (PD), interference, anti-interference, capacitor        

Introduction

The PD is caused by uneven electric field and electric media, bubbles, impurities and corrosion, thermal cracking, moisture of insulation etc. The PD mechanism is based on the electron-collision ionization theory. In the electric field, the speeding free electrons collide with neutral molecules. The kinetic energy of electron is high enough to make neutral molecules stimulate electrons, forming new free electrons and ions. Thus, the electron avalanche generates. The model of air gap discharge in the medium is shown in Fig.1. There are a variety of interference sources in the PD test.