PURPOSE: To improve the reliability and the economical efficiency of the titled device and to prevent malfunction due to abnormal voltage and noise by using both optical fiber cable and telegraph cable for the transfer of control signal between electric stations.

CONSTITUTION: Usually, the optical fiber cable LC is used for the transfer of a control signal between transmitting and receiving circuits A3, B3 of a transfer device. If a fault is generated in a light transmitting/receiving circuit, an electric signal is sent to the 1st electric station A as a control signal through a telegraph cable Cc because the contact Ry of a protection relay in the 2nd electric station B is actuated. A time limitting relay TRy is actuated by the control signal, and with lapse of prescribed time, a contact TRya is actuated to retract the transmission of a breaker on a transmitting side. The contact TRya is actuated delaying by a prescribed time even at the generation of abnormal voltage such as induced voltage to prevent the influence of abnormal voltage.