Partial Discharge Characteristics of a Void Defect inside an Actual 252-kV GIS Post Insulator

Epoxy insulation is one of the important components in gas insulated switchgears (GISs), and its reliability directly affects the safety and stability of the GIS equipment. Epoxy insulation void is a typical defect in GIS insulator, which will cause partial discharges (PDs), accelerate insulation deterioration, and finally lead to insulation breakdown. In this paper, a high-sensitive experimental platform for 252-kV GIS post insulator PD test is established, and the PD characteristics of an abnormal insulator under different voltages are investigated. The experiment result shows that under the routine PD test voltage, the PDs of this insulator is lower than 1 pC. The discharge is weak and sporadic, and traditional PD methods may fail to detect this defect. Under a higher test voltage, PD is enhanced, which is conducive to defect detection. Then the X-flaw detection is performed and the result shows that there is a small void defect inside the insulator with PDs, which confirms that the PDs are generated by internal defects. Finally, the discharge characteristics and mechanism of the void defect are analyzed and discussed. The results in this paper provide an important reference for further mastering the PD characteristics of void defects inside GIS insulators and is helpful for defect detection in routine PD test.