Fiber Fabry-Perot Sensors Based Acoustic Detection of Partial Discharges in Power Transformers

A Fabry-Perot acoustic sensor system is designed for on-line detection of ultrasonic signals generated by partial discharges in transformer oil. Cavity of the sensor is formed between a quartz diaphragm sensitive to dynamic signal and an end of fiber pigtail. Frequency and sensitivity of the sensor have been designed based on the characteristic of the acoustic signal. The signal is measured in the range of narrowband frequencies and deduced through demodulation of the output intensity. The system has inherent immunity to electromagnetic interference. The theoretic analysis and computer simulation shows that the system has a sensitivity of 10pC discharge level at 100 mm from the PD source