Research on the Vibration Distribution Characteristics of Transformer Windings Based on Distributed Optical Fibre Sensing

ABSTRACT

The vibration signals of transformer windings are critical parameters for evaluating their mechanical condition. To achieve in situ winding vibration measurement and investigate its spatial distribution characteristics under multiple operating conditions, this paper proposes a distributed optical fibre monitoring method based on phase‐sensitive optical time‐domain reflectometry (Φ‐OTDR). Short‐circuit temperature‐rise, variable‐load‐factor and accelerated thermal‐ageing tests were conducted on a transformer prototype. The results show that the winding amplitude exhibits an M‐shaped axial spatial distribution under normal operating conditions. The frequency‐multiplied components introduced by the nonlinear hardening characteristics of the spacers increase with the load factor, with the total harmonic distortion increasing from 1.56% at 0.1 p.u. to 6.88% at 1.3 p.u. The effect of temperature on the vibration distribution primarily arises from changes in the stress–strain relationship of the spacers. Meanwhile, owing to the thermal expansion of the conductors, the total harmonic distortion first increases and then decreases with increasing temperature. After insulation ageing, degradation of the spacer elastic modulus and accumulation of plastic deformation cause the amplitude distribution to change from an M‐shaped pattern to a gravity‐influenced spatially asymmetric distribution. The total harmonic distortion increases to 10%–20%, whereas the phase differences of the 100 Hz component among the measurement points expand from within 15.4° before ageing to a range of −161.1° to 139.8°. This study provides technical support for vibration‐based transformer condition assessment.