Research on the Neutral Point Operation Mode and Fault Line Selection Strategy of Nuclear Power Plants

The auxiliary power of Chinese nuclear power plants is a medium-voltage system, and large cross-section cables are commonly used. Because of the high capacitance current, it is difficult to extinguish the arc when a single-phase ground fault occurs. The neutral point using resonant grounding method can inhibit arc reignition. The actual field operation shows that the arc suppression device has a long response time and the problem of difficult fault line selection. Firstly, this paper investigates the transient process of single-phase ground fault in auxiliary power systems. It is proposed to use delayed removal of series damping resistance to speed up the response speed. Secondly, this paper investigates the fault selection technology of the parallel resistance of the arc suppression device. It is proposed that reasonable selection of the resistance value of the parallel resistance can improve the fault line selection accuracy and suppress the residual fault current. Finally, the effectiveness and reliability of the above solution measures are verified by PSCAD simulation.