Residual current sensor protection action The setting current can be from mA to A, and the sensitivity is very high, so it is possible to detect subtle changes in leakage current in the electrical circuit. It is used to extract the residual current signal of the monitored line, and can continuously detect the leakage current of the grounding system. The primary current with a larger value can be converted into a secondary current with a smaller value through a certain transformation ratio for protection and measurement. And it can realize the use of power monitoring for three-phase systems at the same time. When a leakage current occurs in the electrical circuit, the trip device is driven to switch the power supply network to achieve the purpose of ground fault protection.