| 摘要 |
A microprocessor based tie relay controls a tie circuit breaker between a main bus and a transfer bus to which any one of a number of feeder lines may be connected through a disconnect switch when the feeder circuit breaker associated with that feeder line is out of service. Settings for the protection characteristics of each of the feeder relays controlling the feeder circuit breakers are stored in non-volatile memory together with a default protection characteristic suitable for protecting any of the feeder lines. The appropriate protection characteristic for the feeder line connected to the transfer bus is selected for use by the tie relay in controlling the tie circuit breaker. This selection may be made manually by an operator, or preferably automatically by the microprocessor of the tie relay which monitors the states of the feeder circuit breakers and of the disconnect switches and selects the settings associated with the feeder line whose feeder circuit breaker is open and disconnect switch is closed. If the microprocessor does not recognize only one feeder line connected to the transfer bus, the default protection characteristic is selected and an alarm is generated.
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