A new DC system fault detection method based on improved unbalanced bridge

Grounding fault and injecting AC into DC control system in substation may lead to many protector problems, such as maloperation and miss trip, Based on the traditional unbalanced bridge and blocking condenser principle, the IUB(Improved Unbalanced Bridge) is put forward to detect ground resistance and alternating voltage occurred in substation DC system. The circuit of IUB models in MATLAB/Simulink is presented, and a DC system fault detection circuit board is constructed to achieve the detection function of grounding fault and AC intrusion. The results showed that the proposed method is correct and effective.