DESIGN VULNERABILITY OF THE GROUND FAULT PROTECTION SYSTEM FOR THE PREFERRED POWER SUPPLY OF NUCLEAR POWER PLANTS

摘要

According to the analysis result of the faults caused plant shut down in Korean nuclear power plants during last 10 years, the share of electrical fault is 21%. The first case was instrumentation and control system faults and it is 30%. And, more than a quarter of the electrical faults are ground faults. Consequently, ground fault protection is one of the indispensable schemes to enhance the reliability of nuclear power plant electric power systems. This paper elaborated the ground fault protection system for the main generator and preferred power supply line of typical type nuclear power plant in Korea and the vulnerability of the ground fault protection system also. Then, proposed the subharmonics voltage injection type ground fault protection scheme as an alternative.