Fault recorder is a kind of device that can record automatically when power system breaks down or vibrates. It can record the current, voltage and its derived quantity caused by short circuit fault, system oscillation, frequency collapse, voltage collapse and other large disturbances, such as the whole process change phenomenon of active power, reactive power and system frequency.

According to the different conditions of power system failure, the function of fault recording device is mainly reflected in three aspects:

1. In case of system failure, the protection action is correct

The current and voltage recorded by the fault recorder are used to locate the fault line, and the basis of strong transmission is given.

2. Power system components trip for unknown reasons

The current and voltage recorded by fault recording are used to determine whether there is no fault trip. The fault recording device can find out the cause and immediately resume power transmission.

3. Incorrect action of relay protection device

No fault trip caused by misoperation of relay protection device

The system is faulty but the protection device refuses to operate

The system is faulty but the protection action does not conform to the pre design

The reason of incorrect protection action can be found out by using the event amount of protection action recorded by fault recorder and the state information of switch auxiliary contact. If necessary, simulation calculation and analysis can be carried out by means of calculation tools.