Hitachi, Ltd.

The Chugoku Electric Power Co., Inc.

Kenji Kohara

Shingo Shirakawa

Seizo Nakano

Seiichi Maruyama

Eichi Okamoto

A transmission line protection system arranged such that a leakage current detector is provided at an end of an insulating device such as an insulator connected at one end to a corresponding one of arms of a steel tower and connected at the other end to a transmission line of each phase, thereby detecting an arrester leakage current flowing in the transmission line of each phase, an output signal of the leakage current detector being led to a repeater through an optical fiber cable, an output of the repeater being transferred to a control/supervisory board in a substation through an optical fiber cable. In the control/supervisory board, preferably, a received digital signal which was converted from an analog signal at said leakage current detector is displayed on a cathode ray tube. In such an arrangement, it is possible to smoothly perform supervision of the status of the transmission lines without causing maloperations due to influences from the transmission lines.

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Hiroshima, Japan

Kenji Kohara