High sensitive and reliable fiber Bragg grating hydrogen sensor for fault detection of power transformer

A fiber Bragg grating (FBG) sensor is proposed for detecting hydrogen in transformer oil. A thick palladium layer (560 nm) is prepared with magnetron sputtering to get high sensitivity. Meanwhile, in order to solve the problem that the palladium layer peels off from the FBG when the sensor is exposed to a high concentration of hydrogen, polyimide is added in the adhesive layer. The reliability of the sensor with polyimide layer is significantly increased when the hydrogen concentration is 4%. The experimental results demonstrate that the proposed FBG hydrogen sensor can effectively indicate the small concentration of the hydrogen dissolved in transformer oil, and the sensitivity is raised up to 13.5 ppm/pm in oil.