GIS Partial Discharge Acoustic Emission Detection and Noise Suppression Based on Optical Fiber Interferometer

The ultrasonic signal generated by partial discharge can monitor and detect the operation status of gas-insulated switchgear (GIS) online in a timely and effective manner. The optical fiber ultrasonic sensing system based on Michelson interferometer has the advantages of low detection limit and is not easy to be affected by electromagnetic interference, and is suitable for GIS partial discharge ultrasonic detection. However, it is susceptible to environmental noise, reducing the signal-to-noise ratio of the system. In this paper, high-frequency carrier modulation and frequency down-conversion demodulation methods are introduced. According to the proposed demodulationc method, it can not only reduce the influence of environmental noise on the detection effect, but also prevent the detection blind spot caused by phase fading. It can also reduce the sampling frequency to achieve real-time demodulation. In order to verify the effectiveness of the detection system proposed in this paper, an ultrasonic testing platform was built to verify the effectiveness and accuracy of the demodulation scheme. In order to verify the detection effect of the detection system under actual working conditions, an experiment was carried out on a 1000kV substation true GIS, and the PD ultrasonic signal was successfully detected, and the time-frequency characteristics of the PD ultrasonic signal were successfully detected.The PD ultrasonic detection system proposed in this paper proposes a more sensitive and effective means for GIS PD monitoring.