Power transmission line sag detection device

The invention relates to a sag detection device for a power transmission line. The device comprises a positioning device and a monitoring device. The positioning device is arranged in the middle of apower transmission line at the lowest point of the power transmission line; a control unit, a positioning module, an inclination angle sensor, a distance measuring base station A, a power supply A anda wireless transceiving module are arranged in the positioning device; the positioning module is connected with the control unit; the inclination angle sensor is connected with the control unit; thewireless transceiving module is connected with the control unit; the power supply A provides power for the control unit and the distance measuring base station A. The monitoring device is fixedly installed at the joint of an electric pole and the power transmission line. A control chip, a wireless receiver, a network communication module, a distance measuring base station B and a power supply B are arranged in the monitorin