220kV电力变压器短路动力学性能分析

Dynamic Performance Analysis of Winding for 220 kV Power Transformer with Short Circuit

电力变压器突发三相同时短路时,短路电流对变压器绕组动稳定性影响重大。笔者针对一台220 kV等级电力变压器,基于有限元电磁—结构耦合计算,运用动力学原理,研究短路电磁力作用下的低压绕组机械强度及变形过程。在电磁分析中,计算了各绕组的轴向和辐向电磁力,确定绕组中承受电磁力最大的线饼;在辐向应力应变分析中,以电磁力为激励,对选定绕组进行瞬态动力学计算,得出线圈的辐向动态应力及位移;在绕组轴向振动分析时,考虑线饼间绝缘垫块弹性模量,分析线饼轴向动态力和轴向位移。分析结果为变压器绕组短路强度校核提供参考依据。

When a sudden short circuit fault occurs on three phases of a power transformer, the short circuit current produces a significant influence on dynamic stability of the transformer windings. In this paper, the mechanical strength and transient dynamic response of the low-vohage winding under the electromagnetic force due to short circuit are analyzed for a 220 kV power transformer based on magnetic-mechanical coupling analysis via two-dimensional finite element method. The axial and radial components of electromagnetic force on the low- voltage winding are calculated by using electromagnetic analysis. Kinetic analysis is conducted to calculate the radial stress and strain in the disk which undergoes the maximum radial electromagnetic force. The axial transient dynamic stress and displacement of the low-voltage winding are investigated considering the elastic modulus of the kraft paper. This study may facilitate the strength verification of transformer winding in short circuit condition.