Overhead transmission line is an efficient energy transmission method, and it plays a key role in the safe operation of power grid. Nowadays, power flow on the transmission lines is limited for keeping the conductor temperature below the line’s Maximum Allowable Conductor Temperature (MACT), which is difficult to monitor accruately and results in  serious limitation of the transmission capacity. In this paper, multimode optical fibers are implanted into 10m aluminium conductor steel reinforced (ACSR), and the conductor temperature is monitored in real time by Raman distributed optical fiber sensing system. Also, the measurements of temperature accuracy and distribution are carried out in the constant temperature chamber and outdoors, respectively. The temperature measurement results of thermocouple and infrared thermal imager are compared. It is found that the temperature rise position of ACSR can be accurately located by the Raman distributed sensing system with a spatial resolution of 1m. Compared with the thermocouple and infrared thermal imaging, the measurement error of optical fiber is less than 0.3 °C. It is feasible to implant the optical fiber in the overhead transmission line to measure conductor temperature, whose accuracy and timeliness are guaranteed.

temperature,overhead transmission line,Raman distributed optical fiber sensing,online monitoring