sensor used in DC ground fault detection system according to measurement method can be divided into low frequency AC signal detecting and DC signal detecting of leakage current . It greatly affect the accuracy of the earth fault signal because of the existence of capacitance in the detecting of low frequency AC signal and it doesnt have online measurement DC current sensor in the market when we want to measure load leakage current. Caliper DC ammeter cant meet the requirements in DC system ground fault diction in terms of resolution, accuracy, range, on-line installation and on-line measurement.

Recently, with the increasing strength of attracting business and investments in Liaoning coastal area or big cities’ suburbs (counties), a large number of industrial and mining enterprises have shifted to rural areas. The rural areas’ power load is growing rapidly, but at the same time, many power sites such as 66kv substation, 10kv transmission line, and low-voltage distribution area have occurred different levels of “low voltage”, which affect the daily life and production of native residents. From 2011, Liaoning Electric Power Co., Ltd. has applied the third generation of dynamic reactive power compensation technology—SVG to control the “low voltage” of rural network, which has fast speed and strong compensation. And as a consequence, there is good social and economic benefit.