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核电厂直流系统为重要控制和保护负荷供电,对核电厂安全稳定运行起到至关重要的作用。接地故障是危害直流系统可靠供电及其负荷正确运行的主要因素之一。简要介绍了直流系统接地故障的原因和危害,对直流系统一点接地和两点接地故障模式进行深入分析。为避免一点接地引起的故障,需在直流系统设计中采取优化措施;为避免两点接地引起的故障,则应采用绝缘监测装置。对各类绝缘监测方法进行研究和评估,并对现有绝缘报警定值的设计方法进行深入分析。最后提出了绝缘监测报警定值设计的改进方案。
Nuclear power plant DC system for the important control and protection of load power supply, safe and stable operation of nuclear power plants play a crucial role. Ground fault is one of the main factors that endanger the reliable power supply of DC system and the correct operation of the load. This paper briefly introduces the reasons and hazards of DC system ground fault, and analyzes the DC system ground fault and two-point ground fault mode. In order to avoid the fault caused by a little grounding, it is necessary to take the optimization measures in the design of DC system; in order to avoid the fault caused by two grounding, the insulation monitoring device should be adopted. Various types of insulation monitoring methods for research and assessment, and the existing insulation alarm set value design in-depth analysis. Finally, an improved scheme of insulation monitoring alarm design is proposed.