Maximum Frequency Decay Rate for Reactor Coolant Pump Motors

This paper presents methods and results of an analysis to determine the maximum expected frequency decay rate (FDR) at Pilgrim Station Unit 2, a nuclear power generating station utilizing a pressurized water reactor design. The maximum expected FDR would be of concern if it was greater than the FDR analogous to the freewheeling coast-down rate of the reactor coolant pump motors. This paper should benefit utilities and regulatory agencies evaluating pressurized water reactor station designs as it describes how to analyze the off-site power system. The paper includes discussions of the criteria for analytically creating overloads to force frequency excursions, load shedding and under-frequency relay effects on the FDR´s, important assumptions made, a comparison of FDR´s using different load models, and a comparison of the findings with those of other investigators.