Various Characteristics of GIS Insulation Systems and Test Method of Insulating Spacers for Residual DC Voltage

摘要

The insulation performance of gas-insulated switchgears (GIS) for AC systems is verified by lightning-impulse voltage and power-frequency voltage tests (AC test). The lightning impulse voltage test mainly treats surge overvoltage as an object, while the AC test intends normal operating voltage and temporary overvoltage during operation. However, no test is performed to verify the insulation performance for residual DC voltage due to switchgear operation and so on, since this is not specified in existing standards. Now that GIS are increasingly downsized as specifications are rationalized, the influence of metallic particles and various characteristics of insulators, such as insulating spacers, must also be taken into consideration for residual DC voltage. Accordingly, the present paper reports on various characteristics of GIS insulation systems (Chapter 2) and the withstand voltage performance evaluation method for insulating spacers (Chapter 3) as key factors in insulation design and testing on residual DC voltage. They are outlined as follows: - Resistive and insulation characteristics of GIS insulators against DC voltage are shown. These characteristics will be utilized in the electric field and the insulation design of GIS insulation systems against DC voltage. - When metallic particles are exposed to residual DC voltage, they generate relatively stable partial discharge. Measures against these metallic particles include detection with partial discharge measurement and suppression of behavior by means of an insulating sheath on the bottom surface of the tank. - The test method has been developed, which evaluates the withstand voltage performance of 550kVclass - three phase GIS bus insulating spacers against residual DC voltage by determining characteristics varying over time in the electric field on the insulating spacer surface under DC voltage.