DFB Fiber Laser Based on External Optical Feedback Theory Applied in Long-Distance Power Transformer Partial Discharge Detection

Active fiber optic acoustic emission (AE) sensors cause external optical feedback (EOF) in engineering applications, resulting in performance loss when used for long-distance partial discharge detection in power transformers. This work employs a distributed feedback fiber laser (DFB-FL) as a sensor to construct a partial discharge detection system. Furthermore, two schemes that improve the long-distance detection performance of DFB-FL are proposed by Suppressing EOF (S-EOF) and Introducing EOF (I-EOF). Then, partial discharge tests in an 80 kVA power transformer validate that both schemes can implement long-distance partial discharge detection. Experimental results indicate that the S-EOF system has a significant signal-to-noise ratio, which is 6.01 dB higher than the piezoelectric transducer (PZT). The S-EOF scheme is suitable for long-term online partial discharge monitoring. The I-EOF system has a high sensitivity for partial discharge detection, and its detectable discharge magnitude is lower than 65.8 pC. The I-EOF scheme is applicable for short-term systemic sampling and daily inspections.