Abstract:

In order to effectively solve the problem of overstep tripping caused by short circuit of the power supply system in coal mines, according to the principle of decentralized detection of single-phase grounding fault of injected signal, the single-phase grounding fault line selection theory was proposed based on the combination of signal injection and decentralized detection, and zero sequence current was added to the fault circuit to provide the ideal zero sequence current to the fault system. In addition, analog components were used to build a test system to test the injected signal detection part, and a test model was built to realize the single-phase grounding fault of the power grid system. Digital optical fiber communication protector of the underground distribution network was used to ensure rapid and accurate actions and fault isolation after the failure of the underground power supply system. The results show that by injecting a signal with a main frequency of 80 Hz and an amplitude of 40 mA, the signal filtering algorithm can filter out the interference of power frequency and harmonic signal. When the frequency of the injected signal is offset in a small range, the device can accurately detect and extract the injected signal to judge the fault.

Key words: signal injection, decentralized detection, overstep of power supply system, communication protector, voltage transformer