Analysis and Prevention Countermeasures of Insulation Breakdown Caused by Foreign Body Fault of 800 kV GIS Disconnector

GIS equipment has been applied widely in power grid and is one of the key equipment in transform substation. This paper focuses on an 800kV GIS bus differential protection finding that GIS disconnector exists a fault after on-site inspection. The insulation structure of GIS is checked and proven to be reliable by finite element method. After returning to the factory for disassembly, tests are carried out. It is comprehensively determined that the fault is resulted from insulation breakdown caused by foreign body attached to the moving side shielding devices. The prototype is organized to verify the source of foreign body in GIS disconnector, and the type and size of foreign body are obtained. The foreign body is proven to cause insulation breakdown by establishing the FEM model of the foreign body fault and this method can provide reference for similar GIS fault. Finally, to prevent similar accidents, the control measures to avoid foreign body fault in the process of production, manufacturing and assembly are put forward.