Buckling Strength Investigation for Power Transformer Winding under Short Circuit Impact

Power transformers are inevitably subjected to external short circuit impact during their service period. The electromagnetic force generated by the fault current may cause winding destabilization and collapse. The radial buckling of the inner winding accounts for a considerable proportion. Based on the effective contact of the sticks, the traditional analytical methods ignore the manufacturing deviation and operation impact (MDOI) characterized by assembly gaps and insulation shrinkage. To address the limitation of the contact-constrained approach, this paper proposes the equivalent support stiffness (ESS) analytical method. The ESS method can investigate the issues of support weakening and failure, which are affected mainly by assembly gaps and insulation shrinkage. Further, two transformers are implemented in the short-circuit tests to demonstrate the feasibility of the ESS method. Among them, the assembly gaps are investigated by the first and second windings of the newly manufactured transformer, and the influence of insulation shrinkage is researched through a 30-year-old transformer. Furthermore, the application of the ESS method is expressed based on the tests and the simulations. The research presents quantitative references for transformer design and operational reliability assessment. The ESS method can be an improvement and supplement to traditional methods.

在变压器服役期间，不可避免地会受到外部短路冲击的影响。故障电流产生的电磁力可能导致绕组失稳和坍塌，其中内绕组的径向屈曲占据了相当大的比例。基于棒材的有效接触，传统的分析方法忽略了由组装间隙和绝缘收缩所表征的制造偏差和运行影响（MDOI）。为解决接触约束方法的局限性，本文提出了等效支撑刚度（ESS）分析方法。ESS方法可以研究支撑减弱和失效问题，这些问题主要受组装间隙和绝缘收缩的影响。此外，在短路测试中实施了两个变压器，以证明ESS方法的可行性。其中，组装间隙通过新制造的变压器的第一和第二绕组进行研究，而绝缘收缩的影响则通过一个30年的变压器进行探究。进一步地，基于测试和模拟，ESS方法的应用得到了阐述。本研究为变压器设计和运行可靠性评估提供了定量参考，ESS方法可以作为传统方法的改进和补充。