| 摘要 |
An a-c line, isolated from ground by a transformer, is continuously tested for ground faults through a switching network which sequentially completes a circuit between the a-c conductors, an apparent active power source, and a ground fault detection network. A fault condition detection network is coupled through a bridge circuit to the a-c lines, to provide an indication of a simple fault on either line, or a substantially unbalanced fault on both lines. An oscillator and ring counter arrangement continuously drives a switching network to test for individual line grounds, and balanced and unbalanced double line faults. A self-contained power supply arrangement is provided.
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