| 摘要 |
PURPOSE:To provide a ground fault indicator capable of reliably indicating a failure only when an opposite phase current flowing through an overhead earth wire is detected at a steel tower where a ground fault has occurred. CONSTITUTION:Two current transformers CT1 and CT2 are respectively attached to an overhead earth wire extending to both the sides of a steel tower. The outputs of these CT1 and CT2 are sent to the circuit of two transformers T1 and T2, for instance, and their sum and difference are calculated. Moreover, the output of this circuit is sent to an in-phase discrimination circuit and an opposite phase discrimination circuit; and a failure indication circuit is operated only when the opposite phase discrimination circuit has operated and a failure indictor such as flash lamp is operated. |
