Technical Evaluation of the Proposed Design Modifications and Technical Specification Changes for the R.E. Ginna Nuclear Power Plant
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Published: 1980
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DOWNLOAD EBOOKThe present design uses undervoltage relays to sense the loss of offsite power. There are no Class 1E loads on the 4160-volt buses. This design consists of two relays per 480-volt Class 1E bus (two Class 1E buses per redundant load group) for the first level of undervoltage protection. An undervoltage condition (loss-of-voltage) will result in isolating the Class 1E buses from all offsite sources, initiating emergency diesel generator start and load shedding on the Class 1E buses, permitting closure of the diesel generator supply breakers, and lastly, the loads will be automatically time-sequenced onto the buses. Actuation begins with loss of voltage to 368 volts (77% of 480 volts). The existing system does not bypass the load-shedding feature once the emergency diesel generators are energizing the Class 1E buses. The licensee has proposed a design change which includes automatic degraded voltage protection. This modification consists of the addition of two time-delayed, undervoltage relays on each 480-volt Class 1E bus, to provide the second level of undervoltage protection.
