| 摘要 |
PURPOSE:To make it possible to detect independent operation of a low power plant regardless of frequency fluctuation. CONSTITUTION:An independent operation processing section receiving bus voltage VB of high power system and bus voltage VP of low power power plant comprises relays 251, 252 for detecting phase difference between voltages VB and VP having wide and narrow detecting zones respectively, timers T1 and T2 receiving outputs from the phase difference detecting relays and preventing erroneous detection, and an OR circuit OR1 producing a logical sum of the outputs from the timers T1 and T2, wherein independent operation is detected based on the phase difference between the voltages VB and VP. |
