Calculation On Windings Stability In Condition Of Switching No-Load And Short-Circuit For Transformer

One of the most important issues in transformer industry and research is the power transformer windings which may be damaged or even collapsed by the powerful electromagnetic force. In recent years, the conclusions drawn from the transformer damage, its process and its subsequent disintegration of inspection showed that incidents are not caused by the material damage, but the windings can not continue to maintain the overall structure of the intact windings (that is, the stability of the windings) because of the electromagnetic force. Shortage in sufficient stability of power transformer windings has become one of the main reasons for the damage of power transformer and outstanding problem for the operation of transformer. Therefore the stability and research of large power transformer has very important practical significance in product development and design process.In this paper, mechanism and characteristics of the inrush current generated by no-load on the single-phase and three-phase transformer is analyzed. A precise numerical simulation of switching no-load inrush current is made under different circumstances of core residual flux and switch-on phase angle for transformer type SZ11-31500/66 under the application of MATLAB. Meanwhile, the inrush current transformer windings electromagnetic force and the stability are calculated through the application of calculation and analysis software-large-scale power transformer winding short-circuit strength calculation and analysis software. In the axial stability calculation, the application of finite element software ANSYS is applied to establish the three-dimensional axial model for natural frequencies transformer windings. During the calculation, non-linear of material and axial pre-stress effects is fully considered as a reference for the choosing of axial pressure on the transformer windings. In the aspects of horizontal stability calculation, a reasonable horizontal electromagnetic force model is created for the inner winding (clamped at both ends of the single-span model) and the criterion of pressure instability inside the windings is given in this paper. Meanwhile, transformer DFP1-240000/500 is taken as an example under the application of finite element software ANSYS clamped on both ends of the elasticity and elastic-plastic model of single-span were calculated and analyzed. And it is pointed out that material plastic deformation factors are to be fully considered in the horizontal stability calculation in the windings.