Acoustic-enhanced fiber optic MZI sensing technology for partial discharge detection in XLPE cable accessories

Abstract The research on partial discharge detection using high-sensitivity fiber-optic Mach–Zehnder interferometer (MZI) sensing technology for cable accessory defect recognition is insufficient, which restricts its engineering applications. In this paper, a frequency-domain sensitivity model of the acoustic-enhanced structure was established. An acoustic-enhanced fiber-optic MZI sensing system was then constructed, and its anti-interference performance was analyzed. Finally, the system was used to conduct experimental tests on four types of simulated defects in cross-linked polyethylene (XLPE) cable accessories, including air gap defects, impurity defects, scratch defects, and moisture defects. The results show that the acoustic-enhanced structure provides acoustic amplification in the 20–200 kHz range and can concentrate acoustic energy at its terminal region. The acoustic-enhanced fiber-optic MZI sensing system can resist environmental temperature changes and low-frequency vibration interference. It can effectively recognize four types of simulated defects in XLPE cable accessories and outperforms cylindrical fiber-optic MZI sensing systems and piezoelectric transducers sensor. For impurity and moisture defects, the acoustic-enhanced fiber-optic MZI sensing system can detect partial discharges with a minimum charge of 32.0 pC and 54.6 pC, respectively. For air gap and scratch defects, the system has better defect detection ability than high-frequency current transformer, with the initial discharge voltage being 10.0% and 6.8% lower, respectively.