Measurement and Analysis of Partial Discharge on Typical Defects in GIS

Li Jisheng, Zhao Xuefeng, Yang Jinggang, Li Dajian, Li Yanming
HIMALAYAL - SHANGHAI - CHINA

Abstract: In order to study the partial discharge (PD) characteristics of the typical defects in GIS, a 220kV GIS bus bar cavity was taken as an object to design four PD physical models, and then the PD signals on different defects were detected by the pulse current method. The effects of the applied voltage on the center-phase distribution and average amplitude of the discharge pulses were investigated, as well as the signal discharge waveform and energy distribution were researched. The experimental results indicate that PD has the high stability and repeatability of the discharge on the identical defect model under the same condition. The phase-resolved PD (PRPD) patterns, the time domain waveforms, average amplitude and central phase changing of PD signals had very similar distribution characteristics and those of different defect had different ones. So the conclusion provides a test basis for the recognition of PD types and a deeper study of the mechanism of PD. 

Key words: GIS, defect model, partial discharge characteristics, pulse current, PRPD pattern, pulse waveform, characteristics analysis

Introduction 
Due to advantages such as small floor area, easy to install and free of external interference etc, the gas insulated substation (GIS) is extensively applied in the high-voltage transformation and transmission power system. However, when GIS breaks, it is hard to repair and takes a long time. What is more, the effect caused by faults is large, resulting in  severe consequence. Among all the breakdowns, the insulation breakdown is the most common one. The partial discharge signal, including abundant insulation condition information, not only detects introduced defects during the production and installation of GIS, but also effectively detects the insulation breakdown and its severity in on-line monitoring. Hence, partial discharge measurement is an important method for insulation condition monitoring.

In order to study GIS discharge characteristics and improve the precision of detection technologies, this paper designs common partial discharge model via utilizing GIS simulation segment, collects discharge signal through broadband detection impedance and extracts effective parameters from the signal by means of applying rear-end process software. Comparing discharge characteristics of different insulation defects provides an important test and theoretical basis for effectively detecting GIS breakdown and its classification.