With the continuous deepening of China's smart grid construction, the construction of rural intelligent distribution stations has also made great progress. In many areas, rural distribution stations are equipped with intelligent main protection or residual current relays. Through these intelligent devices, the residual current in the station area can be monitored and protected in real time, greatly improving the supervision of residual current. However, relying solely on intelligent total protection or residual current relays to monitor and protect the residual current in the substation area is not enough. It is also necessary to control the source of residual current generation. Residual current testing tools are used to accurately locate the substation area where the residual current exceeds the limit, find the leakage point of residual current, and thus eliminate the fault of residual current exceeding the limit.

According to the actual usage on site, the testing tool is divided into two models, one is the simple type and the other is the network type. When using the simple residual current testing tool, it is directly connected to the circuit. When abnormal residual current is measured, the alarm indicator light on the device indicates that there is an over limit situation in the residual current. It is easy and intuitive to use. The network-based residual current testing tool not only has all the functions of a simple type, but also adds remote communication function. When the residual current exceeds the limit in the line is detected, the situation of the residual current exceeding the limit will be uploaded to the main station system or the troubleshooting personnel's mobile phone through the mobile network, which is convenient for direct location and analysis of on-site faults.

　　·The residual current detector is equipped with a handheld device for easy on-site query of test results or parameter setting;

　　·The residual current detector can remotely log in to the main station system through GPRS/CDMA public network, report event records in real time, and can directly perform data collection and other operations on the detector using a mobile APP client;

　　·The residual current detector can record the time and magnitude of residual current exceeding the limit;

　　·The residual current detector adopts a clamp shaped opening method, which is convenient for on-site hanging and removal;

　　·The residual current detector adopts a built-in rechargeable lithium polymer power supply and does not require on-site power supply;

　　·Fast testing speed, accurate judgment, simple operation, and easy portability.

Applied to locations where leakage current trips frequently occur, it helps operation and maintenance personnel accurately and quickly locate the leakage point. It can also be applied to the measurement of residual current.