Study on Radial Stability of Power Transformer Winding Considering Conductor Transposition Structure and Brace Support State

Continuously transposition conductors are widely used in power transformers, but there is a problem of overestimation due to simplification when evaluating the radial stability of windings. In this study, a refined multi-turn finite element model of 220 kV transformer winding is established, considering the conductor transposition structure and support stiffness. Compared with the traditional model, the effects of support degradation, local support failure and short-circuit cumulative effects are studied. The results show that under the same stiffness, the critical buckling load of the simplified model is 8.8% higher than that of the refined model, and the maximum stress is 32.2% lower. Reducing the support stiffness can reduce the critical buckling load, and the maximum stress will be transferred from the support to the transposition area. Local brace failure will further reduce the critical buckling load. After 11 times of short-circuit impacts, the residual stress and plastic displacement in the transposition area reached 38.9 MPa and 0.73 mm, respectively. The establishment of the refined model lays the foundation for the accurate evaluation of radial stability and the structural design of the transformer.