Research On High Voltage GIS Partial Discharge Detection Characteristics

GIS?Gas Insulated Switchgear,Gas Insulated Metal Closed Switchgear?is a high voltage electrical equipment with SF6 gas as insulating medium.Compared with traditional transmission equipment,GIS has many advantages,such as compact structure,small area,safe operation,high reliability,small maintenance and small electromagnetic radiation.GIS equipment is made of aluminium alloy enclosure,so it is difficult to detect local defects in the insulation,which will lead to insulation breakdown when it reaches a certain level.Partial discharge detection technology is an effective means to evaluate the operation status of GIS.It can detect early partial discharge in GIS in advance,identify and track it in time,and improve the reliability of equipment operation.This paper introduces the internal discharge mechanism of high voltage GIS and the occurrence process of SF6 gas discharge,and studies the insulation characteristics of SF6 gas gap and the surface discharge of solid insulators in SF₆ gas.According to the mechanism of partial discharge and the development process of partial discharge in GIS equipment,in general,the insulation defects in GIS will cause partial discharge to varying degrees,which will inevitably accompany the development process of partial discharge before breakdown occurs.UHF method and Acoustic Emission method are the better methods of partial discharge detection in GIS.In this paper,a real GIS equipment is used to build a partial discharge detection test platform.According to the common insulation faults in the actual operation of GIS,three typical defect models are designed,which are metal particle discharge,insulating object discharge and corona discharge at the tip of GIS.Among them,the metal particles scattered on the horizontal insulator and the metal particles left on the inner wall of the metal shell are selected to discharge.The discharges of the insulating objects are selected as the discharges of the flashover basin insulator and the insulating wire in GIS.The discharges of the tip corona discharge are selected when the SF6 gas pressure is high and the pressure is low.In this paper,UHF and Acoustic Emission Partial Discharge are detected under different working conditions of each typical defect model.The size of partial discharge is controlled by adjusting test voltage and SF6 pressure.UHF and Acoustic Emission discharge waveforms and phase diagrams are obtained and summarized.The experimental results show that different types of typical defects in GIS show different characteristics in UHF and Acoustic Emission detection of partial discharge waveforms,and the differences are quite large.In practical application,the discharge types can be identified by analyzing and comparing the characteristics of discharge waveforms,which has played a guiding role in the fault diagnosis of GIS.