Force and Temperature Characterization of a Novel Fiber Bragg Grating Overhead Line Sensor

Area of Science:

• Materials Science
• Optical Engineering
• Electrical Engineering

Background:

• Overhead power lines (OHLs) require continuous monitoring for mechanical integrity.
• High-temperature low-sag (HTLS) conductors present unique monitoring challenges due to operational temperatures and mechanical loads.
• Existing monitoring solutions may lack the robustness or accuracy needed for advanced conductor types.

Purpose of the Study:

• To characterize a novel optical sensor for OHL mechanical parameter monitoring.
• To evaluate the sensor's performance with both conventional and HTLS conductors.
• To demonstrate the sensor's capability for simultaneous temperature and mechanical load tracking.

Main Methods:

• Development of an optical sensor utilizing fiber Bragg gratings (FBGs) in a hermetically sealed Kovar® capillary tube.
• Epoxy-free design for enhanced durability and reliability.
• Laboratory testing involving strain and temperature measurements across a range of 30 °C to 200 °C and forces up to 2 kN.
• Assessment of sensor performance through thermal cycling tests.

Main Results:

• The sensor directly measures conductor strain and temperature, enabling indirect estimation of sag, tension, and stress.
• Experimentally determined sensitivities were approximately 0.4 nm/kN for force and 27 pm/°C for temperature.
• The sensor maintained force sensitivity within a 20% variation after ten thermal cycles between 30 °C and 200 °C.

Conclusions:

• The developed optical sensor offers a reliable method for monitoring mechanical parameters of OHLs, including HTLS conductors.
• The robust, hermetically sealed design ensures consistent performance across a wide temperature range.
• The sensor's ability to simultaneously track temperature and mechanical load highlights its potential for enhancing power transmission network safety and efficiency.