Measurement and analysis of partial discharge on floating electrode defect in GIS

Abstract

In this paper, a 220kV GIS bus bar model is established to study partial discharge characteristics of floating electrode defect in Gas Insulated Switchgear (GIS), which is one of the common sources of PD. The 220kV GIS bus bar cavity is taken as an object to design physical model of floating electrode defect. The PD development process is researched by applying gradually increased voltage. The UHF method and the acoustic method are used to detect the PD. The PRPD patterns at different voltage levels of PD are accessed through the PD data of UHF signal. The discharge patterns of different voltage levels at continuous mode and phase mode are obtained through ultrasonic method. These measurements can provide test basis for the assessment of partial discharge provoked by floating electrode defect in GIS. It is shown by experiments that the PD characteristics change as the applied voltage raised. Their specific performances are the discharge number at positive and negative half cycle getting more, and the phase interval gradually widened with the increase of applied voltage. But the discharge amplitude has no dramatic change with the increase of the applied voltage. By comparison of the UHF method and the acoustic method, it is concluded that UHF method has advantages of interference immunity, high sensitivity. The acoustic method is electromagnetic noise immunity. The acoustic sensor do not require intrusive installation and do not destroy the GIS structure itself. Compared to the UHF sensor, it may be more cost effective. But the acoustic signal is attenuated and the measurement sensitivity is under the influence of the temperature. The two methods both can make PD location using the time difference of the different sensors. The two kinds of measurements can provide test basis for the assessment of partial discharge provoked by floating electrode defect in GIS.