Dynamic Calculation Method for Transformer Short-Circuit Considering Cumulative Effects

Power transformers are critical components in power systems. Insufficient short-circuit withstand capability remains one of the significant causes of transformer failures. Aging equipment commonly experiences deteriorated performance, while quantitative methods for calculating cumulative degradation are lacking. Although dynamic methods have been developed, they suffer from insufficient consideration of material cumulative effects, leading to significant computational errors and limited applicability. Therefore, breakthrough solutions incorporating cumulative effects are urgently needed. This paper proposes a dynamic short-circuit calculation method based on electromagnetic-vibration coupling considering cumulative effects. An inter-disc refinement model incorporating a series-spring model for insulating materials and a damping model for oil gap structures is developed. Based on an axial mass-spring-damper model, winding disc vibration displacement provides spatial parameters for electromagnetic calculations, establishing bidirectional coupling. Simulated short-circuit impact and accelerated thermal aging tests on insulating materials and conductors obtain key mechanical parameters and cumulative deformation patterns, which are incorporated into the algorithm, forming a differentiated verification method considering individual transformer history and operating age. Short-circuit tests on 10 kV prototypes validate the algorithm with average errors of 4.32% and 1.54% for first and second displacement peaks, achieving accuracies exceeding 95.5% and 98.4%, respectively, providing technical support for enhancing transformer short-circuit withstand capability.