Multipoint Ultrasonic Detection and Localization of Transformer Partial Discharge Using FDM-φOTDR

Partial discharge (PD) detection is crucial for maintaining transformer safety. Multipoint ultrasonic detection of transformer PD leads to accurate localization and early warning of insulation defects. To increase the number of ultrasonic measurement points, this article proposed a novel method for multipoint detection using frequency-division multiplexing (FDM) phase-sensitive optical time-domain reflectometry ( $\varphi $ OTDR) system. The proposed method expanded the traditional response frequency band of $\varphi $ OTDR by four times, enabling the simultaneous detection of PD ultrasonic signals at ten points with a frequency band of 0–200 kHz. Experimental result confirmed the accurate localization of the transformer PD model. The proposed FDM- $\varphi $ OTDR system enables comprehensive PD monitoring without the need for manual relocating of measurement points, making it suitable for in-service detection and on-line monitoring of transformer PD.