| 摘要 |
PURPOSE: To provide a compact ground fault detecting apparatus by detecting zero-phase current and overcurrent flowing through a distribution line using a current transformer. CONSTITUTION: In the invention, when a ground voltage is detected through a limiting resistor 17A and a ground overvoltage relay 12 in the tertiary open delta circuit 10C of a transformer 10 for grounded instruments, the switching circuit 18 is closed to form a low impedance circuit 17 so that the ground fault current i1 flowing in the distribution line is detected by a transformer 5, thereby omitting a zero-phase transformer.
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