| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent change of zero-phase resistance in a power system and reduce influence of a protection system for line-to-ground fault even in a plural ity of extra high voltage or high voltage transformers are operated in parallel. SOLUTION: Extra high voltage or high voltage transformers TR1, TR2, TR3 and TR4 are connected to buses BUS1, BUS2, BUS3 and BUS4 through circuit breakers CB1, CB2, CB3 and CB4. Interconnecting circuit breakers for buses 52B12, 52B23 and 52B34 interconnect between the buses BUS1 to BUS4. The buses BUS1 to BUS4 provide grounding transformers GPT1 to GPT4. Undervoltage relays 27B1 to 27B4 are provided on the side of delta connections of the grounding transformers GPT1 to GPT4. Equivalent grounding resistors are separated into resistors for constructing delta connectionsΔR1 toΔR4 and resistors for maintaining operation currents in directional line-to-ground fault relays R101 to R104. The resistorsΔR1 toΔR4 and the resistors R101 to R104 construct detaching circuits. When power systems are operated in parallel, the detaching circuits detach the resistors R101 to R104 in systems other than the highest priority system according to priority order.</p> |
