Fault Simulation and Detection of Oil-Immersed On-Load Tap Changer Based on Dual Cantilever Beam Fiber Bragg Grating Vibration Sensor

This study presents the design and application of a fiber Bragg grating (FBG) vibration sensor with a dual cantilever beam structure for fault monitoring in oil-immersed load tap changers (OLTCs). The sensor leverages the strain-wavelength modulation principle of FBGs, enhanced by a symmetrically distributed dual cantilever structure to amplify sensitivity. Theoretical analysis derived the relationship between acceleration and wavelength shift, validated through acceleration calibration, which demonstrated a linear response (R2=0.9993) within 2–20 m/s<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The sensor exhibited stable performance in transformer oil simulations (40–100°C) and effective sealing. A fault simulation platform for KM-type OLTCs was established, replicating four common faults: loose drive shaft bolts, loose arc plates, contact wear, and spring fatigue. Time-frequency analysis of vibration signals revealed distinct spectral features: loose bolts induced low-frequency resonance, arc plate loosening caused minor vibrations, contact wear generated high-frequency components, and spring fatigue reduced low-frequency responses. The sensor demonstrated high accuracy in capturing fault-specific signatures below 4 kHz, confirming its potential for early fault diagnosis in OLTCs. This work provides a reliable method for enhancing OLTC operational stability and maintenance efficiency through vibration-based condition monitoring.