| 摘要 |
PROBLEM TO BE SOLVED: To delay the operating time of a ground relay on the non-utility side in case of an accident-incurred by providing a means of determining whether an earth fault, if it occurs in non-utility power receiving equipment connected to a high-tension distribution line from a distribution substation, occurs on the non-utility side or not. SOLUTION: A controlling device 10 disposed in the ground relay on the non-utility side is so formed that, using the information of failed current obtained by detecting an input signal in a residual current transformer on the non-utility side, a signal of the failed current may be transmitted from an input circuit 12 to a filter circuit 13 and then a higher harmonic analysis circuit 14 and a level detection circuit 15, outputs from the former two circuits may be inputted, with a signal of a timer 17, into an operating time characteristics switching circuit 16 for processing, and a signal may be outputted into an operation circuit of the GR through an output circuit 18. Two pieces of information of waveform difference and analytic value of higher harmonies are used for determination and, in case of an accident-incurred, such a control as delays operating time of the GR is conducted.
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