Abstract: GIS is important equipment responsible for power distribution and fault excision in power grid. For obtaining the internal state of GIS equipment without power failure, discovering and alerting equipment defects in advance, avoiding equipment failures and power grid accidents, the GIS was inspected by live detection methods like ultrasonic, UHF, vibration and gas decomposition products. The test signals were analyzed based on electromagnetic field theory. The reason and development process of discharge were explained by the principle of capacitance partial voltage and chemical reaction equation. It was found that there were vibration and discharge phenomena in the 110kV GIS busbar PT disconnector. The ablation trace was found on the fork, reed and drive pin after offline disassembly. Meanwhile, amount of metal sulfide power was found near the discharge point. The reason of discharge is probably the lack of pressing force of the reed. Then the contact among the fork, reed and drive pin is loose causing the floating discharge. The offline disassembly result verifies the validity of online detection. The online detection prevents a severe accident of unplanned outage of busbar caused by the discharge.
 

GIS,online detection,floating discharge,ultrasonic method,vibration

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