Sensitivity Optimization of the Optical Coupling Fiber Sensor for Acoustic Sensing of Partial Discharges

A sensitivity optimization scheme of optical coupling fiber sensor (OCFS) focusing on three factors has been presented and the optimized OCFS for partial discharge detection has been demonstrated experimentally. First, removing the pre-tension during fabrication can dramatically increase the sensitivity of OCFS. It can be explained that longitude pre-tension makes the sensor hard to vibrate transversely and limit the sensitivity. Moreover, the sensitivity of OCFS could be improved further by optimization of coupling agent. It seems that acoustic impedance of UV epoxy resins is more matched with the propagation medium (aluminum), and consequently leads to high sensitivity of OCFS. In addition, the effect of laser linewidth on the sensitivity is also analyzed. Finally, PD detection experiments are carried out to test the proposed sensitivity optimization in comparison with PZT. It indicates that optimized OCFS not only detects PD effectively but also has higher sensitivity and wider band than traditional PZT. Considering the EMI immunity and essential stability, OCFS could be a preferred candidate for PD on-line monitoring.