The fault recorder is used in power system. It can automatically and accurately record the changes of various electrical quantities before and after the fault, including the steady-state recording process and the transient recording process. It can be analyzed by the fault recording graph.

There is a certain correlation between steady-state recording and transient recording. When the power system is in steady-state operation, the operation parameters will change greatly after a sudden big disturbance, and then reach a new stable operation state.

Steady state recording refers to the stable state of power system operation. The stable state is that the operation parameters, voltage, current, power, etc. are kept unchanged. However, in the actual operation of the power grid, this kind of stable state is rare, and there are certain deviations. Therefore, the operation parameters of the power system continue to change around a certain average value and the change value is very small, which is called steady-state recording.

Transient recording refers to the transition process from one stable operation state to another. The operation parameters of this transition process will change greatly and the speed is very fast. This process is called transient recording.

The stable recording and transient recording of fault wave recording are different from whether the electrical parameters of power system are stable. Both processes are the key points of graphic analysis of fault recording. We should not only look at the change of transient process, but also combine the steady-state change process of fault recording graph to see whether there are abnormal points which change very slowly, and comprehensively analyze the causes of the accident.