Research On Calculation And Evaluation Technology Of Winding Anti Short Circuit Capacity Of Distribution Transformer

The safe operation of distribution transformers is crucial in the distribution system,and if a failure occurs,it will directly affect the reliability of the distribution network.Distribution transformer damage is often caused by short circuit fault,transformer in the oblong,circular,rectangular and other winding structure applications,increase the distribution transformer short circuit fault damage probability and the difficulty of calculation and analysis,so for the distribution transformer anti-short circuit verification method research,can guide the production of transformer and anti-short circuit design,thereby improving the anti-short circuit performance of the distribution transformer,reduce the damage rate when the transformer is shorted,has important engineering practical value.In this paper,the three-phase short-circuit current of the transformer is first analyzed and calculated,and the inrush current of the transformer short-circuit and the multiple of the shortcircuit current are given.Using the three-phase short-circuit current as the load,the finite element simulation software ANSYS established a three-dimensional model of the oblong winding distribution transformer of different structures,and the magnetic field characteristics of each model were compared and analyzed,and the leakage magnetic field and short-circuit current density distribution of the low-voltage winding were obtained.The low-voltage copper discharge pinout and axial amp-turn balance simulation are compared and analyzed,the axial magnetic field and radial magnetic field are analyzed in detail and the distribution law is summarized,and the accuracy of the three-dimensional finite element analysis method is verified by the transformer model magnetic field test.Then,according to the winding layout characteristics of the distribution transformer,the analysis method of the short-circuit winding force analysis of the transformer is improved,the correlation coefficient is summarized and introduced,and the calculation method of the shortcircuit electromagnetic force of different winding parts of the transformer is summarized based on the finite element method.Considering the actual process of transformer installation and compression,the relationship between the offset of the transformer and the total external thrust is calculated and analyzed,and the calculation methods of various stress sizes and short circuit temperature rises of the transformer winding short circuit are summarized,and the winding is checked in combination with the anti-short circuit requirements in the transformer standard GB1094.5.Finally,the calculation method of short-circuit magnetic-structure sequential coupling of distribution transformer is proposed,the modeling and processing method of low-voltage copper foil and high-voltage layer winding is given,and the different working conditions of the transformer are simulated,the deformation and stress size of the windings and structural parts are obtained,and the weak position of the transformer’s winding resistance short-circuit resistance is summarized.By comparing the effects of the short circuit temperature rise on the winding deformation and stress after the winding,the improvement measures to enhance the winding strength of the distribution transformer are proposed,which has reference value for transformer designers.