Distributed temperature sensing in OPGW with multiple optical fibres

Abstract

The ampacity of a material is defined as its maximum electrical current capacity. In an overhead transmission line, it is related to the maximum sag that does not compromise its safe operation. As the sag depends on the conductor's temperature, with this parameter it is possible to estimate its ampacity, increasing the efficiency of the electrical system via real-time energy dispatch management. With the Brillouin backscattering phenomena, the distributed temperature measurement in the fibre inside the optical ground wire (OPGW) or optical phase conductor is possible. However, it is common for overhead power transmission lines to be composed by more than one optical fibre. A calibration algorithm was developed to enable the application of a distributed temperature sensing equipment to monitor the temperature of an OPGW with more than two different fibres. The 230 kV Ibipora-Londrina Transmission Line was used as a case study, being approximately 20 km long and composed of three different fibres spliced in series along with its extension. Through comparison with calibrated sensors, the technique and algorithm were validated. It was possible to characterize the system and perform the temperature monitoring with a spatial resolution of 1 m and amplitude error of less than 6°C.