Finding Grounding Points in Substation DC System by DC Current Injection Method

The operation environment of the secondary circuit of the substation is poor, which is easy to cause grounding failure. Once the two-point grounding, there is a risk of automatic device rejection or misoperation, which needs to be eliminated as soon as possible when the single point grounding. However, the efficiency of the early search method is low, which is easy to cause the wrong action of the relay protection equipment. The AC injection method commonly used at present will cause disturbance to the secondary circuit, which is easy to be interfered by distributed capacitance. DC leakage current monitoring method has a large input and can not locate the fault point. The DC current injection method is proposed in this paper, which can overcome the influence of the charge and discharge transient of distributed capacitors. The DC constant current is used to charge distributed capacitors for a short time, and stable and continuous current is formed in the circuit where the grounding fault is located after the steady state is reached. The DC clamp ammeter is used to efficiently determine the faulty branch and quickly locate the specific grounding fault point on the branch. High security and reliability. At the same time, the method adopts constant current DC source, which can overcome the ground fault resistance fluctuation and has strong anti-interference ability.