A compound signal method selective leakage protection method and system

Abstract

The invention discloses a compound signal method selective leakage protection method and system. The method is to inject an additional detection DC signal while the main line is supplied with AC power, and the low-voltage protector of the main switch always detects the entire power supply line through the additional detection DC signal. When the low-voltage protector of the main switch detects that the insulation is lower than the threshold value, the low-voltage protector of the main switch injects the additional AC current generated by the AC generator from the main line into the power supply through the signal injection control part In the line, the current direction of each phase of the additional AC current is different from the voltage of each phase of the power supply AC; when the power directional leakage protector in the sub-switch of one of the sub-lines detects that the additional AC When the zero-sequence current is low, it is judged that there is leakage in the sub-line, and the sub-line is cut off immediately. The invention enables the sub-switch to correctly select the earth leakage circuit, thereby achieving the purpose of selective leakage protection.

Description

technical field [0001] The invention belongs to the technical field of coal mine power supply, and in particular relates to a selective leakage protection method and system. Background technique [0002] In the underground low-voltage explosion-proof feed switch of coal mine, it is required to install selective leakage protection. This branch can restore the power supply system to normal and ensure the safety of the power supply system. However, often because the selective leakage protection of the sub-switch is not selective, the feed switch refuses to operate or malfunctions, and the feed switch (hereinafter referred to as the main switch) installed in the incoming line circuit malfunctions, etc., which seriously affects the coal mine. normal production. [0003] At present, the leakage protection of the underground low-voltage feeder system is realized in this way: [0004] A DC signal is added to the main switch, and the main switch has been measuring the insulation r...

AI Technical Summary

Problems solved by technology

Due to the thinner cables and shorter cable lengths of the low-voltage system, the ground capacitance of the entire low-voltage system is very small, especially when the single-phase is grounded by resistance (that is, the insulation is reduced), the capacitive current is smaller, and there is no way for the branch switch to be correctly grounded. Quantitatively determine the direction of the zero-sequence current. Therefore, there are often malfunctions or refusals, which also cause malfunctions of the main switch.

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