Fiber Optic Fabry-Perot Sensor with Stabilization Technology for Acoustic Emission Detection of Partial Discharge

Partial discharge (PD) is one of the major reasons that leading to insulation destroyed of power equipment. PD measurement can help to find faults earlier and reduce the financial loss. An extrinsic Fabry-Perot interferometer (EFPI) sensor is presented to detect PD acoustic emission in the oil. The relationship between cavity length and parallel misalignment of FP cavity facets is theoretically analyzed. Silica diaphragm and signal mode fiber are used to form FP cavity. The sensing diaphragm will induce Fabry-Perot cavity length modulation when acoustic is detected. For high sensitivity, the resonant frequency of diaphragm is modeled by the finite element methods (FEM) in ANSYS. To prevent drifting of operation point, a quadrature intensity demodulation system using distributed feedback (DFB) semiconductor laser is proposed for EFPI acoustic sensor. When operation point drift influenced by temperature and pressure, the center wavelength of DFB laser will be tuned to lock the operation point by method of feedback control. The performance of the EFPI sensor system is verified by preliminary test. EFPI sensor and piezoelectric (PZT) transducer are both used to detect acoustic emission signals generated by partial discharge from noodle-plate model. The experiment shows that the proposed EFPI sensor sensitively detects acoustics from partial discharge.