Unbalanced short circuit analysis for the Hope Creek nuclear generating station

On March 19, 1990 the Hope Creek generating station was tripped off line when a phase-to-phase fault occurred on the Salem to Deans 500-kV transmission line. The fault was very close to the Salem switchyard. The Salem station is adjacent to Hope Creek. The line circuit breakers opened and closed within four cycles to clear the fault. In the present study, the authors simulate the Hope Creek nuclear generating station power distribution and the nearby 500-kV network during the fault, and analyze the depression of voltages in the plant. The study is conducted so that equipment responses in the plant can be reconciled with the depression of voltages caused by the fault. The close-in phase-to-phase fault apparently created highly unbalanced conditions in the three-phase power distribution network of the Hope Creek plant. As a result, undervoltage relaying at 4.2 kV and 7.2 kV did not operate, while the voltage on the 480/120 V control transformers dropped below the setpoint of the voltage sensing relay, initiating a plant trip.<>