Fault analysis of AC power supply cables in power plants affected by low voltage ride through device

The article proposes a fault traveling wave characteristic analysis method about AC power supply cables fault in power supply system of power plant key auxiliary motor. First, a small step simulation model including VVVF(Variable voltage and variable frequency) and low voltage ride through(LVRT) device is constructed. Then, the fault characteristics of voltage and current signal about key auxiliary AC power supply cable faults are derived. Furthermore, the signals are analyzed by wavelet methods, to achieve accurate fault location based on the traveling wave principle. Simulation shows that under disturbances or faults, there will be sudden changes and noise caused by electronic components in AC power supply system to the plant motor. By applying wavelet analysis methods, the sudden changes can be accurately identified. Compared with current signals, voltage signals have more significant amplitude changes and less noise impact. Due to the presence of power electronic switching devices, the three-phase power signal switches are not synchronized, and symmetrical faults also have zero sequence components in the sudden changes caused by faults. Therefore, fault analysis can use phase components or zero sequence components. At the same time, the load side current also needs to consider the sudden changes caused by noise and electronic devices. In the simulation case, the main energy of most of the voltage and current signal sudden changes is concentrated in the frequency band of 12.5-18.75kHz, which can be used to set the sampling parameters for accurate fault location equipment.