Fault recording device plays a very important role in power system. According to the recording data, the working conditions of relay protection and automatic device (correct action, misoperation and refusal of action) can be correctly evaluated. Especially in case of switching fault, the accurate data provided by the device can help find the shortcomings of relay protection and automatic device and help to further improve and perfect these devices. At the same time, the situation of the circuit breaker (tripping, closing time, refusal to move, jumping, breaking, etc.) is truly recorded, and the existing problems of the circuit breaker can be found and hidden dangers can be eliminated.

        From the electrical quantity change curve of the fault oscillogram, we can clearly understand the operation of the power system. The fault oscillogram is generated according to the change process from the beginning of the fault to the beginning of the fault when the fault occurs. It is not only important for the fault process, but also important for the time period before and after the fault occurs.

        The fault recorder can record 5-10 cycles of section a before the fault occurs, and one cycle is 20ms, so the fault recorder can record 100 ~ 200ms before the fault occurs. The fault recorder can record 150-1000 cycles of section B after the fault occurs, that is, 3 ~ 20s after the fault occurs.