| 摘要 |
In one aspect, the invention provides a residual current device (RCD) for protecting a circuit by tripping in response to an imbalance signal representative of residual current imbalance in the circuit. The RCD trips the circuit when the imbalance signal exceeds a predetermined threshold rating. The RCD comprises test means for increasing the imbalance signal so as to test operation of the RCD against the rating. In another aspect the RCD comprises: a current transformer for generating an imbalance sense current in a sense coil in response to a current imbalance in an electrical supply; and a degaussing coil for substantially removing remanence in the current transformer by application of a degaussing signal to the degaussing coil.
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