413 / 2022-03-15 20:31:59

Long-distance Transmission Line monitoring Based on Brillouin Optical Time-domain Reflectometer

Transmission Line Monitoring,BOTDR,distributed optical fiber sensing

On-line monitoring of transmission lines is essential for power grid security. With the length of tens of kilometers, transmission lines are hard to be fully monitored. Distributed optical fiber sensing based on Brillouin scattering is able to detect temperature distribution of each point along the long-distance fiber, which is suitable for transmission lines condition monitoring. However, the sensing distance of the distributed optical fiber sensors is not enough for long transmission lines, and the calibration method of laid lines is unclear. This work proposed an effective method to achieve a sensing distance of 100 km. To calibrate the data measured in the field, fiber Bragg grating (FBG) sensors were installed onto the power tower.

Experimental/Modeling methods

In this paper, Brillouin optical time-domain reflectometer (BOTDR) was built to achieve distributed temperature sensing along the fiber. The Brillouin backscattering light was further amplified by a two-stage amplifier. The sensing distance of BOTDR was extended to 100 km. A group of fiber Bragg grating (FBG) sensors was designed to obtain the temperature value, which was used as standard figures while calibrating the results of BOTDR. Field tests were conducted on a 220 kV transmission line, temperature distribution along the fiber is obtained, which reflected the state of the transmission line.

Results/discussion

The sensing distance of BOTDR was extended to 100 km in the laboratory. Field tests were carried out on a 220 kV transmission line, and temperature distribution was obtained with the calibration referring to FBG sensors applied onto the power tower.

Conclusions

This work provided a distributed monitoring method for the long-distance transmission line. An effective two-stage amplification method was derived, extending the sensing range of BOTDR to 100 km. A calibration method of the laid line was put forward to demodulate the temperature distribution along the fiber.