Fiber bragg grating sensor for hydrogen detection in power transformers

A novel hydrogen sensor is designed on the basis of Fiber Bragg grating (FBG) sensing technique. The sensor can be arranged inside the transformer. It has several advantages, such as fast fault detection and location, immunity to electromagnetic interference, quasi-distribution measurement and real-time monitoring. The principle of the proposed FBG hydrogen sensor is based on changes of the physical properties of palladium films which absorb hydrogen. A thick palladium layer prepared by magnetron sputtering is used to achieve high sensitivity. Meanwhile, polyimide is added into the adhesive layer to improve the reliability of the sensor. Partial discharge experiments demonstrated that the wavelength shift of the FBG hydrogen sensor varies linearly with the concentration of hydrogen dissolved in the transformer oil. It is hardly disturbed by other factors. The hydrogen sensing experiment in oil at a temperature of 80°C revealed that the sensitivity of the sensor remains same as the temperature varies, ranging from room temperature to operating temperature of the power transformer. Thus, the proposed sensor can work properly under the operating temperature of power transformers.