An Improved Radial Buckling Analysis Method and Test Investigation for Power Transformer under Short Circuit Impact

The inner winding of the power transformer is subjected to uniform compressive stress in the radial direction during the short circuit, which makes circular radial stability a crucial component of reliability. At present, the radial stability evaluation system lacks the sufficient state characteristic judgment quantity considering the manufacturing devia-tions and assembly gaps, which makes the design and cal-culation of the transformer have significant variation devia-tion and seriously endangers the operation safety of the equipment. This paper proposes an improved radial buck-ling analysis method (IRBAM) to investigate the circular radial stability of inner winding. The IRBAM is implement-ed by defining two characteristic parameters, equivalent flexibility and manufacturing deviation (MD). Besides, the buckling judgment method of the relative change ratio of impedance (RCRI) is proposed as a condition for ending the test. The destructive short-circuit tested transformer, with the rated power of 50MVA and the high-voltage (HV) rated voltage of 110 kV, is designed. Then, 72 cumulative short-circuit tests are performed until impedance exceeds the permissible value based on the judgment. It is verified that IRBAM can effectively match the failure mode of the transformer windings by comparing the experimental phe-nomena and calculation results.

电力变压器内部绕组在短路过程中会承受径向均匀压应力，这使得环形径向稳定性成为影响其可靠性的关键指标。当前的径向稳定性评估体系缺乏足够的、兼顾制造偏差与装配间隙的状态特征判断量，导致变压器的设计计算存在显著偏差，严重威胁设备的运行安全。本文提出一种改进型径向屈曲分析方法（IRBAM），用于研究内部绕组的环形径向稳定性。该方法通过定义等效柔度与制造偏差（MD）两个特征参数实现。此外，本文还提出以阻抗相对变化率（RCRI）作为屈曲判断方法，以此作为试验终止的判定条件。本文设计了一台额定容量为50MVA、高压（HV）额定电压为110kV的破坏性短路试验用变压器，随后基于该判定条件开展了72次累计短路试验，直至阻抗超出允许值。通过对比试验现象与计算结果，验证了IRBAM可有效匹配变压器绕组的失效模式。