To dispense with the maintenance work of a terminal by substantially eliminating the consumption of a battery at the thermosensitive detection terminal, and besides to remote-control abnormal heating in real time.

This system is equipped with a transmitter which transmits a signal including ID information by wireless, a power source, and a switch between the transmitter and the power source. The switch is switched on only at the abnormal heating, so that a thermosensitive detection terminal 6 being a normal-off switch which is usually switched off is attached to the specified point 4 of an overhead wire. A plurality of transceivers 9 which receive the signals by wireless and transmit them by wireless are arranged at low places of a chain of pylons 11-1n. This system transmits the signals received with a plurality transceivers 9 in the pylons 11 to 1n-1 outside the service area of an external public network 8 to the transceiver 9 in the pylon 1n within the service area of the external public network 8, relaying the the plurality of transceivers 9 in the pylons 12 to 1n-1 between those pylons 11 and 1n, and transmits the signal received by the transceiver 9 in the pylon 1n within the service area to a monitor center via the external public network 8.