| 摘要 |
A ground cable continuity check circuit for a power supply cable system having a grounding and a pilot conductor electrically interconnected remotely from the power supply. A source of electrical energy for the check circuit is provided through a constant current transformer having its secondary connected between the grounding and pilot conductors. A circuit including the coil of an undervoltage relay and the contacts of a current relay is connected across the constant current transformer primary. The current relay coil is connected in series with the constant current transformer secondary and the grounding and pilot conductors. A voltage breakdown device is connected across the constant current transformer secondary to divert current from the current relay coil when a high impedance appears in the ground circuit for opening the current relay contacts to disable the under voltage relay. The power supply system may have a main cable and at least one branch cable in which case the grounding and pilot conductor loops of the main cable and branch cable are interconnected by a current transformer having one coil connected in the main grounding and pilot conductor loop and the other coil connected between the grounding and pilot conductors of the branch circuit.
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