Analysis of the Influence for Metal Foreign Body on the Shielding Case of Miniaturized GIS and Its Detection Method

The millimeter and micron-level metal foreign bodies are inevitably generated during GIS (Gas Insulated Switchgear) installation and operation, which seriously affects the internal insulation state during their operation. Based on 363kV miniaturized GIS, a test platform with 520kV power frequency withstand voltage and 1175kV lightning impulse withstand voltage is built to analyze the influence of insulation state under different sizes of metal foreign bodies. First, when the foreign of different sizes is adsorbed to the high voltage electrode of the circuit breaker, the internal insulation margin of the GIS is checked to obtain the level of internal insulation deterioration of the circuit breaker. Later, the high voltage method was used to obtain the insulation state change rules of GIS when different sizes of foreign bodies are adsorbed to high voltage electrodes. Finally, the foreign body detection method of two-light source contrast is proposed based on the sensitive optical characteristics of the foreign body, to reduce the impact of the foreign adsorption of the high voltage electrode on the insulation margin of the GIS equipment before the handover test.