Temperature monitoring of power transformer using fiber-optic sensor

A fiber-optic transformer winding temperature sensor based on High Birefringence Fiber Loop Mirror (Hi-Bi FLM) for online temperature monitoring in power transformer is proposed. The proposed sensor works on the principle of interference between two counter propagating light waves having a phase difference. A detailed theoretical and practical investigation proved this sensor to be suitable for online transformer monitoring applications, showing insensitivity to high electric field as well as transformer vibrations. Experimental results confirmed theoretical predictions, depicting a wavelength sensitivity of 0.58 nm/°C with high accuracy and reversibility, and the minimum detectable temperature variation is 0.173°C.