Remote Open Phase Faults in the Supply System of Start-up Transformers of Nuclear Power Generating Stations

United States Nuclear Regulatory Commission (US NRC) has requested to the US nuclear power generating industry that Open Phase Conditions (OPCs) should be automatically detected. This requirement has been extended by other regulatory bodies worldwide. Several systems for detecting OPCs are available in the marketplace. Remote open phase faults in the supply system of start-up transformers of nuclear power generating stations (NPGSs) pose a major challenge for available detection systems. A remote fault consists of an open phase fault in an intermediate point of the transmission line that feeds the startup transformer of the NPGS. This paper investigates the ability of existing methods to detect a remote open phase fault in the transmission line that feeds the start-up transformer of an NPGS. It also proposes an alternative protection system.