摘要 |
A relay for tripping a circuit breaker in a high voltage power line, the relay including a current transformer having first and second turns ratios, a heat radiation circuit including a plurality of lamps connected to the current transformer and a sensing circuit including a phototransistor which responds to heat radiation from one of said lamps, the turns ratios and lamps being selectively connectable to provide different minimum trip current levels of the relay.
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