Abstract
Conductive particles are one of the most important defects which can greatly degrade the performance of gas-insulated metal-enclosed switchgear (GIS). Many efforts have been made to clarify the influence on the withstand voltage, understand the flashover mechanism, and build a comprehensive model to describe the particle-initiated flashover. In this study, a partial discharge (PD) signal detected through a photomultiplier (PMT) and recorded by a high-speed data acquisition (DAQ) system was used to analyze the discharge development of a conductive particle-contaminated GIS insulator under constant high AC voltage. An additional PMT was used as a reference to eliminate the dark count of the PMT and the data collection method of a DAQ system was optimized to capture the pulse waveform of each PD to obtain detailed physical information. Spectra of the PD pulse amplitude over pulse width, PD counts within various amplitude ranges over time and phase resolved partial discharge (PRPD) patterns of the PDs in different stages are obtained through the captured PD waveforms. Characteristics of the PDs from the application of the high AC voltage up to the flashover of the insulator were then analyzed, and it was found that the features of the PDs in the near-flashover stage were significantly different to the previous stages.
Highlights
High voltage gas-insulated switchgear is compact metal enclosed switchgear, which offers outstanding reliability, operational safety, and environmental compatibility, and is used widely in electrical power transmission grid for tens of years
The performance of a gas-insulated metal-enclosed switchgear (GIS) can be greatly degraded by presence of defects in the insulation system, such as conductive particles on the electrode or SF6–epoxy interface and voids in dielectric material, which may enhance the local electric field and cause localized discharge, and cause breakdown of the gas gap or flashover of the gas-solid insulating material interface
Lim analyzed the influence of the distance between conductive particle and triple-junction on the flashover voltage of an epoxy surface and proposed a model to present the effect of positive space charge [12]
Summary
High voltage gas-insulated switchgear is compact metal enclosed switchgear, which offers outstanding reliability, operational safety, and environmental compatibility, and is used widely in electrical power transmission grid for tens of years. Lim analyzed the influence of the distance between conductive particle and triple-junction on the flashover voltage of an epoxy surface and proposed a model to present the effect of positive space charge [12]. No comprehensive model of contaminated insulator surface flashover has been proposed, it can be accepted that the overall process is quite complex. The PD process of a cone-type GIS insulator under constant high AC voltage up to flashover has been investigated, initiated by a conductive particle fixed on the concave surface. The characteristics of the PD signals have been presented and analyzed, which may help to understand the process and discharge physics of the contaminated GIS insulator flashover under constant AC voltage
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