Through the principle of small current grounding line selection device, we can know that fault line selection and operation should be simplified as far as possible, but in the actual operation process, there will be some problems. The main factors affecting the small current grounding line selection device include current unbalance, capacitance waveform, current signal and zero sequence current.

Current unbalance is mainly caused by unbalanced load current. The unbalance of current is easy to increase the harmonic current and zero sequence current, resulting in the current in the ungrounded loop higher than that in the grounded loop; the weak current signal is also the main factor affecting the judgment. After the single-phase grounding fault occurs, the zero sequence current will be generated in the fault line. Because of its relatively small value, especially after the arc suppression coil at the neutral point is compensated, its value is still low When using harmonic current than zero sequence voltage to judge the fault line, some workers often can't correctly judge the cause of the fault because the electric flow is too small.

In China's distribution network, the small current grounding line selection device should be very extensive, but due to the frequent parameter changes during the operation of the power grid, the capacitance current and harmonic current often change, and the bus voltage and load current are not constant, so it is easy to cause the direction and size of zero sequence current to change. Therefore, in the actual operation, the reliability and accuracy of small current grounding line selection device need to be improved.

With the continuous progress and development of the power industry, small current grounding line selection will be further innovation in the future development process, which can help staff find fault circuit more quickly, improve its work efficiency and reduce the impact on people's production and life.

With the continuous application of new technology and new equipment, the accuracy of line selection of small current grounding line selection device will continue to improve. All localities should pay full attention to the line selection device and timely rectify the problems, so as to provide guarantee for the safe and stable operation of the power system.