Development of Simulation Modeling Software for Transformer Winding Leakage Magnetic Field Based on C#

Abstract

The simulated calculation model of transformer winding leakage magnetic field is developed based on the development of C# language, and combined with electromagnetic field and transformer theory of this paper. Taking a transformer winding data as an example, the axisymmetric two-dimensional model is established to verify the engineering application effectiveness of the software. Introduction As the continuous expand of the scale of the power grid, the stability requirements for transformer performance are much higher. At the same time, as the capacity of the transformer continues to increase, the loss and thermal and dynamic stability of the transformer are attracted increasingly attention from manufacturers and power grid [1, 2], The premise that the above problems can be analyzed accurately is to accurately analyze the leakage magnetic field of the transformer winding. With the development of numerical calculation, finite element software has sufficient engineering precision to meet the requirements of electromagnetic field calculation [3], but in the general numerical calculation, the calculating model established can only be used to analyze specific physical problems, and its calculating model cannot be applied to analyze other issues [4]. Therefore, in-depth study of the types of transformer windings, how to automatically establish a method to accurately describe various winding models through simple input has become an urgent research topic. Mao Fengchun et al. recommended the model modeled by pie (line) by comparing the geometric models of windings with different fineness levels [5]. However, for large-scale power transformer, the windings contain various structural forms and structures is complex, which require high technical capabilities and experience of analysts. And the manual modeling method is much time consuming. Therefore, the large-scale power transformer winding modeling software which could apply to design, analyze and verify actual transformers is necessary to be developed. The winding is the core component of the transformer, and its variety is various. It is a top priority to construct the model to reasonably establish the winding conductor model to realize the analysis of the distribution of the winding leakage magnetic field. Based on the theory of transformer leakage magnetic field analysis, the calculation and modeling methods of magnetic flux leakage in transformer windings is discussed in this paper. The object-oriented analysis and design software is adopted, the class required for winding modeling is reasonably abstracted. According to various windings, the winding model in which the conductor ring is as the base and the layer unit is as the core are proposed. The C# language is used as a tool to develop simulation modeling software for transformer winding leakage magnetic field. The coil model for different structural forms of the transformer is established quickly and easily via the analysis software, and the output of the software can be easily identified by the finite element software for the simulation of the leakage magnetic field. Model Construction Principles Leakage Magnetic Field Criterion When the transformer winding is connected to the power supply, the magnetic flux is induced in the core of winding. The magnetic flux induced in the core is the main magnetic flux, and the main magnetic flux is mainly closed in the ferromagnetic material such as the stem and the iron yoke. When the load current flows into the transformer winding, the leakage flux is induced at the periphery of the winding, and its magnitude is proportional to the load current. The leakage flux passes through the air passage between the high and low voltage windings and then returns to the space occupied by the winding. When the transformer is working under load state, the high and low voltage windings satisfy the principle of magnetic potential balance. Since the excitation current is small in value (which can be ignored), the principle of the magnetic potential balance is as follows: I1W1+I2W2=0 (1) where: I1, I2—high and low voltage windings current; W1, W2—the number of turns of the high and low voltage windings; The high voltage windings magnetic potential and the low voltage windings magnetic potential are numerically equal and differ in phase by 180°. The excitation applied to the calculation model of the leakage magnetic field should be applied to the high and low voltage windings respectively to apply the ampere balance surface current density to get the correct solution. Model Simplification Principle The center line of the three-phase winding meets the requirements of axis symmetry and can be simplified into a two-dimensional model. It can be seen from the boundary conditions of the field quantity on the interface of different media that the magnetic flux leakage line is perpendicular to the core. In order to reduce the number of finite element units, the core column and the yoke are not used as the solution field.