Design of a novel optical overhead line monitoring sensor

This letter reports on the design of a novel optical overhead line (OHL) monitoring sensor for determining key mechanical line parameters in electrical power networks. The sensor employs fiber Bragg gratings (FBGs) that are inscribed in a metal-coated fiber and encapsulated in a Kovar capillary. The epoxy-free construction of the sensor ensures high-performance hermetic sealing of the FBGs making the proposed sag sensor suitable for monitoring standard low-temperature as well as high-temperature low-sag (HTLS) overhead line conductors. The sensor construction allows for direct measurements of the conductor strain and temperature of up to ±2000 μm/m (μstrain) and up to 450 °C, respectively, and indirect measurements of sag and other parameters such as tension force and stress in the conductor. The sensor design optimization is performed by means of the finite element analysis (FEA), allowing the expected strain transfer from the conductor to the strain sensor to be investigated theoretically. It is demonstrated that the proposed design of the sensor, with a simulated strain transfer of 52%, is suitable for providing sag measurements within the required ranges. The proposed sensor has the potential for multiplexing on a single optical fiber and thus can be used for the determination of OHL sag, temperature, and vibration over a wide-area power network, enabling precise dynamic line rating and condition monitoring functions.