The fault recorder can automatically and accurately record the changes of various electrical quantities before and after faults such as short circuit and grounding. Through the analysis and comparison of these electrical quantities, we can correctly analyze and judge the fault development process and fault types of power system, lines and equipment, provide more accurate information for fault location, and help the power supply department to achieve advanced control of equipment accidents, timely detect equipment defects, quickly make accident treatment plans, and greatly reduce the loss caused by accidents 。

The 110kV Substation in a certain place suffered from heavy lightning and heavy rain accompanied by strong wind. The background monitoring machine sent out the protection start-up information, and the 50MW generator unit shut down. It is found that the fault point is likely to be in the 35kV Power System on the user side through the fault recording graph.

After that, the staff of the power supply department conducted a detailed inspection of the equipment on the user side, and found that one supporting porcelain insulator was damaged in two phases of the bus bridge at the high voltage side of No. 1 main transformer room of Huangqian 50MW generator, and the local burning of the bus bars of B and C phases was serious.

According to the field analysis, the reason is that under the bus bridge side of the high voltage side of the No.1 main transformer room under the shutter load shedding, heavy rainfall and lightning, accompanied by strong wind, a large amount of rain water swept into No.1 main transformer room.

High temperature weather and large load operation of main transformer make rainwater heat evaporate, a large amount of moist hot gas rises and gathers in the 35kV high-voltage bus bridge area of main transformer and cannot be discharged. The polluted insulator is wetted, resulting in the reduction of porcelain insulator insulation. In case of over-voltage, B and C two-phase buses discharge to ground along the insulator surface respectively, so it develops into air breakdown flashover discharge, resulting in arc phase short circuit.