Fault recording is mainly used in power system. It can automatically and accurately record the changes of various electrical quantities before and after the fault, such as voltage, current, phase, power, power factor, harmonic, imbalance, etc. through the analysis and comparison of these electrical quantities through the original waveform, so as to determine the fault cause, correctly analyze and evaluate the protection and self-protection The action behavior of the moving device provides the basis.

For example: a factory in a serious failure of the underground power distribution cabinet, the distribution room equipment is basically burned, the production of the whole plant is completely interrupted. According to the graph recorded in the fault recording, the field staff found that in the hundreds of milliseconds of the fault time period, the voltage waveform of two phases almost overlapped, the other phase was reversed with other two phases, and then the overlap and inversion disappeared; after tens of milliseconds, there were tens of milliseconds of overlap and inversion, and the current obviously increased, and then disappeared. Finally, the phenomenon of three-phase symmetrical short circuit appears. According to the calculation of current amplitude, we can know the short-circuit scale of low-voltage side. After 60 ms, the circuit breaker will open and the current will return to zero.

According to the graphic record of the fault recorder, it can be judged that the phase in reverse phase has single-phase grounding fault, which will lead to the three-phase short-circuit accident of the system, which leads to the serious electrical fire in the distribution room and the burning of the whole station equipment. According to the specifications and lengths of bus ducts and busbars, the site staff roughly calculated and estimated the accident point in the low-voltage switchgear. After efforts, the key clues are found and the conclusion of the accident is given. It turns out that there is a fan for heat dissipation on this fault line. During the maintenance and installation, the staff accidentally let the fan touch the system bus, resulting in a single-phase ground fault, which led to three-phase short circuit and power failure of the whole plant.