In order to solve the problem of weak sensing and location failure of existing distribution automation terminals in the steady-state characteristics of high resistance grounding fault in distribution network, a fault detection and section location method of injecting non power frequency signal into neutral flexible grounding equipment is proposed. According to the disposal strategy of permanent grounding fault in distribution network, the non power frequency characteristic current signal is injected into the neutral point through the flexible grounding device injection transformer, the steady-state quantity of characteristic frequency current amplitude is obtained by each feeder distribution automation terminal of distribution network, and the characteristic frequency current amplitude section positioning criterion based on fault section and non fault section is constructed to realize fault section location. In order to enhance the anti-transition resistance and anti-interference ability of fault detection and location, the selection of injection frequency domain affecting fault detection and location is analyzed in detail, and the optimal non power frequency signal injection frequency band of neutral point is formulated. The simulation model of grounding fault section location based on non power frequency signal injection in distribution network is built in PSCAD simulation environment. The simulation results show that this method has strong anti-transition resistance ability and can accurately locate the fault section in a wide range.