Intensity-Modulated Fiber Bragg Grating Sensor for Detection of Partial Discharges Inside High-Voltage Apparatus

The detection of partial discharges (PDs), inside high-voltage (HV) power apparatus, such as transformers, busing, switchgear, and so on, is important as it provides most early indication of failure. This paper presents a novel fiber Bragg grating (FBG)-based intensity-modulated fiber-optic PD sensor. The proposed sensor has been designed to be placed inside the HV equipment, and can detect high-frequency acoustic wave, as emitted due to the occurrence of PDs. For sensing, two pairs of FBGs with partial overlapping spectrum have been placed in full-bridge combination, on the opposite sides of a suitable designed elastic element of a high dielectric constant material. The proposed full-bridge combination modulates the intensity of the reflected light due to vibration of the elastic element. Thus, the proposed sensor does not require either a fiber Bragg grating analyzer or a narrowband tunable laser source, which is conventionally used in FBG-based sensors. Moreover, the proposed sensor also inherently eliminates the error due to large variation in the temperature of the HV equipment, operating at different parts of the world. The fundamental design equations and experimental results are presented in this paper. From this paper, it has been found that the proposed sensor has reasonable good dynamic responses, signal-to-noise ratio, and sensitivity.