Broadband Frequency Partial Discharge Detection Based on a Wide-Narrow Dual Pulse Fiber Distributed System

In this article, a wide-narrow dual pulse was developed to construct a dual branch distributed sensing system for broadband frequency partial discharge (PD) detection. The narrow pulse is used as the probing light of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi $ </tex-math></inline-formula>-OTDR branch to fulfill PD location, and the wide pulse is used in a Mach-Zehnder interferometer (MZI) branch to extend the frequency response range of PD frequency measurement. Three kinds of data processing methods were used for signal demodulation of the dual-branch system, and the results were compared to screen out the best one for actual detection. Positioning capability of multiple acoustic signals of the proposed system was tested using PZTs, and a linear acoustic pressure response was obtained. A wound fiber optic ring was introduced to improve sensitivity to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.03\times 10^{-{6}}$ </tex-math></inline-formula> rad/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>Pa, which is three orders of magnitude higher than that of a standard R15i ultrasonic transducer. A point PD setup was established to verify the actual PD detection capacity of the system. Location and PD waveform restoration results agree well with the preset, and frequency response range could be extended to 20–300 kHz at a sensing distance of 941 m. Due to its broadband frequency PD response, exact PD positioning, and waveform restoration capacity, the proposed system is expected to have broad application prospects in high-voltage power fields.