| 摘要 |
PURPOSE:To shorten a detection time and to enable the grasping of a trouble point from a substation, by providing a terminal device for receiving the call-out code from a relay only when trouble was detected and returning a response signal through an overhead earth wire. CONSTITUTION:For example, when it is assumed that earth trouble was generated in the machinery 3 mounted to a utility pole, a power source is applied to a section switch 9 immediately before a trouble point by the cooperation of a substation side apparatus (1-3) and a trouble section separation apparatus (8-10) and the section on an after is separated and, at the same time, a sensor 17 detects the trouble to close a contact 16. Hereupon, a central apparatus injects a relay call-out signal in a high voltage distribution line 5. When the relay 11 receives the call-out signal, a terminal device call-out signal is injected in an overhead earth wire 6 through a signal injector/detector 12. This call-out signal is transmitted only to a terminal device 18 of which the contact 16 is closed and a return signal is injected in the overhead earth wire 6 from the terminal device 18 concerned. The relay receives the return signal and a response signal is returned to the central apparatus 3 through high voltage couplers 7, 4 to make it possible to know the trouble point.
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