Case 1: On November 10, 2004, the 10kV bus bar fault was caused by the short circuit of a 10kV switch in a 110kV substation, resulting in the complete shutdown of the substation and serious damage to some 10kV equipment.

Fault cause analysis

On-site inspection: The most serious live display sensor (Fuzhou High-tech High Voltage Electric Appliance Co., LTD. Products) of the busbar brake cabinet burned: found that phase A and B have been burned into ash, and phase C is slightly better; Combined with the brake contact burning condition: the C contact is basically intact, the A phase is slightly burned, and the B phase is the most serious. It is assumed that the fault was caused by the B-phase charged display sensor, resulting in a short circuit between the arcs.

In order to further verify the cause of the accident, two undamaged live display sensors in the switch cabinet were dissected, and it was found that the internal mand-rod filler was softened and there was weak insulation. Due to the overvoltage caused by the loss of ground in the 10kV system, the partial discharge inside the sensor gradually develops into a penetrating breakdown, resulting in an interphase short circuit.

Case 2: On August 12, 2010, the 631 switch on the low voltage side of the main transformer of a substation #1 was burned due to heat, which caused a three-phase short circuit inside the switch cabinet.

The preliminary analysis is: 1# main transformer 10kV side 631 hand switch cabinet circuit breaker A phase A plus-shaped contact between the upper side and the static contact bad heat, and eventually developed into a plus-shaped contact arc discharge to the static contact, resulting in serious burning of vacuum circuit breaker copper contacts, cooling parts melting, static contact box burned and produced a large number of metal ions.