Study of the Influence of Void Defect Size on Partial Discharge Characteristics in Solid Insulation

Internal void defects of basin insulator in GIS will lead to the partial discharge and long term partial discharge can cause deterioration of insulation. Therefore, taking the circular artificial void inside the epoxy plate model as the research object, this paper set up the generation and detection system to study the partial discharge characteristics on the base of the pulse current method. The results showed that the increase of the void diameter will lead to the decrease of PDIV, the rise of the maximum discharge quantities and discharge repetition rate. With the void height increasing, the internal electric field intensity, the formation probability of discharge channel and the discharge path length will all change, which can lead that the inception voltage has a minimum value, and the maximum discharge and discharge repetition rate have the maximum value. In addition, the distribution of the surface charges will change with the increasing diameters, which can cause the differences of the phase resolved pulse sequence (PRPD) spectrum. The results of this paper can effectively reflect the stage of partial discharge development and the severity of the void defects.

I. Introduction

Gas Insulated Metal Enclosed Switchgear (GIS) has been widely used in power system for its compact structure, small footprint, low maintenance, high reliability and stable operation [1], [2]. Basin insulator is the main part of GIS and made by vacuum casting process. For the unsatisfactory vacuum environment or the gas entry, the void defects occur in the insulator, which easily leads to partial discharge (PD) due to the electric field concentration inside the void. The long-term PD can cause insulation degradation, lead the breakdown under the operating voltage and result in the accidents, which will bring huge economic loss [3], [4].