Design and testing of a system to classify faults for a generation-shedding RAS

The PacifiCorp Jim Bridger Power Plant has 2.2 GW of installed capacity and is connected to the main grid by three 345 kV series-compensated lines. These lines are, on average, over 200 miles long. In order to operate at full capacity and maintain stability during a system contingency, Jim Bridger requires a generation-shedding remedial action scheme (RAS). PacifiCorp is modernizing and upgrading this scheme. The design of the RAS requires inputs from the protection systems and a special RAS logic relay on critical lines near Jim Bridger. This relay communicates the severity of the fault so that the proper amount of generation is shed, maintaining stability without overshedding. The RAS logic relay must quickly and accurately classify the fault in one of three categories: three phase, multiphase, or single line to ground. It must also accurately classify the fault as severe or nonsevere, as determined by the distance from the Jim Bridger bus. This paper discusses the design of the RAS system, the challenges faced in designing the RAS logic relay, the novel method that was developed for classifying the fault type, and the validation and optimization of the RAS logic relay using a real-time digital simulator.