Packaged FBG + PMN-PT Sensor for Contactless Electric Field Monitoring of Overhead Line Insulators

Overhead line insulators are key components of the transmission infrastructure, and methods for condition monitoring of these assets are critical for a reliable electric grid. Electric field measurement is a useful technique to identify faults and thus there is an increasing interest in non-invasive observation of electric field for insulator condition monitoring. Fibre Bragg grating (FBG) sensing is a promising technology for such application since it is dielectric, small, power passive and can be used to measure various parameters. Thus, this paper presents a packaged FBG electric field sensor for monitoring overhead line insulators. The sensor was built by bonding a substrate of piezoelectric material, PMN-PT, to a polyimide coated FBG sensor and casting into a probe using epoxy resin. When placed in a uniform field, the probe exhibited a stable response in the tested range of 0.05-0.43 kV/mm, which is representative of that encountered in the vicinity of live insulators. Further tests were then conducted on an energised cap and pin insulator string to determine and validate the potential of the sensor to perform diagnostics. The results show that the FBG electric field sensor measurements can indicate the presence of faulty discs on the string and therefore has potential to provide an effective solution for condition monitoring of insulators.