Experimental Verification and Electromagnetic-Mechanics-Acoustic Field Coupling Analysis of Transformer Pressure Relief Valve Malfunctions Due to External Short-Circuit Faults

Transformer pressure relief valve (PRV) false trips resulting from external short-circuit (SC) faults can have serious consequences and lead to enormous economic losses. In our work, experimental and numerical methods were employed to investigate the cause of these malfunctions. External SC faults were performed on a real full-scale 50 MVA/110 kV transformer, and the oil pressure characteristics inside the tank were measured and analyzed. Moreover, a sequential multi-physics coupling analysis method was proposed. Using the finite-element method, the winding displacements and oil pressure behaviors at the PRV were determined. Experimental and theoretical studies revealed that serious external SC faults can lead to sustained vibrations in the windings and create significant oil pressure fluctuations that may further result in PRV malfunctions due to the abnormally high valve pressure.