Abstract: The composition principle of phase-controlled arc suppression coil is analyzed,and a phase-controlled arc suppression coil system based on injected power frequency signal is put forward. The principle of power frequency signal injection method for measuring capacitance current of distribution network system is described,and the measurement accuracy of this arc suppression system is tested through simulation system. The arc suppression system has a simple structure,and can measure the capacitance current fast and accurately,which has a stable operation and good application effect after it being put into operation.