Comparative analysis and countermeasures of power system open phase conditions in Korea’s standard nuclear power plants

Abstract

Open Phase Condition (OPC) is a failure in which one (or two) of the three-phases of the power system is maintained open, and the OPC of the nuclear power plant (NPP) may cause station blackout (SBO) and pose a great risk to the integrity of the reactor core. Recently, OPCs have occurred in power systems at NPPs around the world, but many problems have been reported that failures are not detected by the current protection systems. Accordingly, the NPPs in Korea, which have a power system similar to that of overseas NPPs, also need to review the risks to OPCs. In this paper, the occurrence of OPCs was simulated for Korea’s standard NPPs using ETAP, and the current protective relays were analyzed and compared for each scenario. In addition, based on these analysis results, countermeasures against OPCs are proposed in order to secure reactor core integrity. It is considered that this paper can be used as a technical background material necessary for improving the on/off-site power protection system of NPPs and establishing related detailed regulatory guidelines in the future.