The Necessity of the Field AC Withstand Voltage Test for GIS Operation

Abstract

This article illustrates the characteristics and proportion of GIS system failure through the introduction to GIS system structure and characteristics; In order to make the GIS in the safe operation of the power system, It is necessary to test AC withstand voltage at the scene. Introduction With the development of modern electric power industry, our new substation is mostly on the GIS substation (Combination electric appliance of SF6 gas appliances).It has many unique advantages such as small floor space, convenient maintenance, reliable operation and so on . but the failure of GIS substation is more serious than open substation’s. Through a large number of experiment, it proves that AC withstand voltage test at the scene of the GIS system can discover the insulation of the GIS system defects preferably, and avoid the happening of the accident, also ensure the safe operation of power system[1-3]. GIS makes all primary equipment except the transformer in a substation to be an organic combination whole by optimization design-generally modular structure ,called “gas insulated substation”. In general, it consists of eight parts-the circuit breaker (CB), the isolating switch (DS), earthing switch (ES), voltage transformer (TV), current transformer (TA), lightning arrestor (LA), BUS (BUS) and the casing (BSG). These all are enclosed within a grounded metal shell, shell is filled with SF6 gas (0.3 ~ 0.4 Pa) to ensure reliable insulation of to ground, phase-to-phase and the fracture. As shown in Figure 1. Figure 1 An interval of GIS equipment in 66 kV substation The cause of GIS test The GIS need to take adjustment test after in the factory after redelivery assembling, then transport to the field for installation as the form of transportation unit. Mechanical vibration and impact in the process of transportation may cause the original GIS or assembly fasteners to loose or