| 摘要 |
PURPOSE:To prevent a cable from acting with a surge from outside by mounting four current transformers thereon. CONSTITUTION:With output of current transformers 10 mounted on a power cable 6, measured value of time counting circuits 9 are outputted to a comparator circuit 7. The time counting circuits 9 are synchronized by a synchronous signal 8. A surge developed at a fault point 11 is outputted to a 4-type comparator circuit 7 as measured value with the time counting circuits 9. A current transformer 10 closer to the fault point detect a surge signal more quickly and outputs a signal to the time counting circuit 9 thereby enabling the determining of the detection order of the current transformer 10. When fault takes place at the point 12, the time count detected the current transformer 10 located at both ends thereof is smaller than other values. This indicates a trouble outside the cable, where the detection circuit won't work. |
