Dynamic measurement based on optical fiber sensing technology for the ultra-high voltage large oil-immersed transformer

Dynamic measurement of internal physical parameters during arc-induced explosions in ultra-high voltage (UHV) oil-immersed transformers presents a significant challenge due to extreme electromagnetic interference (EMI) and the highly transient nature of the event. To advance high-voltage measurement science, this study proposes a multi-parameter optical fiber sensing system enabling simultaneous, EMI-immune detection of dynamic pressure, strain, and temperature. The system integrates extrinsic Fabry–Perot interferometric (EFPI) pressure sensors sampled at a high frequency of 20 kHz, alongside Fiber Bragg Grating (FBG) sensors for structural and thermal monitoring. Full-scale arc explosion experiments conducted under 5 kA and 30 kA discharge currents successfully quantified the transient physical responses. Quantitatively, the system captured peak dynamic pressures of 532.4 kPa and 1197.8 kPa under 5 kA and 30 kA currents, respectively, while resolving internal pressure oscillation intervals of 198 ms and 109 ms. It also identified extreme localized negative pressures reaching −1098.6 kPa during the explosion. Furthermore, strain measurements revealed that deformation at bolted access panels was an order of magnitude higher than on the rigid tank walls. Remarkably, the sensors precisely recorded a minimal temperature rise of only 3.13 °C at 10 cm from the arc source. This methodology overcomes the limitations of conventional electrical sensors in severe EMI environments, providing a robust empirical foundation for UHV equipment design and fluid–structure interaction analysis.