The small current grounding line selection device selects the line with grounding fault and gives an indication signal. It is suitable for single-phase grounding line selection of 3KV-66KV neutral point ungrounded or neutral point grounded by resistance and arc suppression coil. It is used in the power supply system of power system substations, power plants, hydropower stations and large factories and mines such as chemical industry, oil extraction, metallurgy, coal, railways, etc. Therefore, in order to ensure safety, any substation and power supply system should be equipped with a small current grounding line selection device. It is a kind of protection equipment used in the power industry.

In the power system, the system whose neutral point is not grounded or grounded through arc suppression coils and resistance is called small current grounding system. The common fault in low current grounding system is single-phase grounding. When a single-phase grounding fault occurs in a small-current grounding system, all lines with capacitance to the ground will have zero-sequence currents. However, because the zero-sequence current is small and has great dispersion, it is difficult to choose grounding lines. There is an arc suppression coil in the system, which makes it more difficult.

When single-phase grounding occurs, the grounding current is small. According to the safety operation regulations of the power system, the single-phase grounding fault can continue to operate for 1 to 2 hours, but the non-faulty relative ground voltage of the system rises to the line voltage at this time, if not handled in time , It is very easy to develop into a two-phase short circuit to expand the fault, and the arc grounding can also cause overvoltage in the whole system. The low current grounding line selection device can accurately find the grounding line alarm.