Computation Of Wave Process And Development Of Software Based On Equivalent Circuit Model Of Transformer

The longitudinal insulation of transformer is mainly assessed through the calculation of transformer winding wave process. As general rule, in order to simplify the process of calculation, single-winding equivalent circuit model is used, ignoring the influence of low-voltage winding to the wave results. However, the assessment of insulation based on the simple equivalent circuit could not be accurate enough. Based on the study of single-winding equivalent circuit model, the double-windings equivalent circuit model which considers the influence of low-voltage winding is developed. And based on the double-windings equivalent circuit model, practical wave process engineering calculation software is developed in this thesis.In this thesis, firstly, based on the analysis of single winding equivalent circuit model of the transformer, a double windings equivalent circuit model is set up. By the method of cut-set analysis, the equivalent network differential equations of transformer are derived, and the node voltage of the transformer equivalent circuit is calculated. Secondly, as the important of capacitance and inductance parameters in the calculation of wave process and taking the influence of the actual structure of the winding form and location into account to the distribution of electromagnetic field. This thesis from the perspective of field, Finite element method and analytical method is applied to calculate of capacitance and inductance parameters of winding, through analysis and comparison of the calculated results to find out the more suitable analytical calculation method.Thirdly, based on the derivation of equivalent circuit equation and calculation of capacitance and inductance parameters, the wave process calculation software facing the engineering staff is developed. The software is based on the hybrid programming of VB and Matlab, using the VB as interface calls the computer program written in Matlab language. The initial voltage distribution along transformer winding, the distribution voltage of the impulse response, the maximum potential distribution and the gradient voltage of oil-duct are calculated and then are output to the VB interface. Finally, one power transformers is calculated by the wave process analysis software written by ourselves. Each transformers are respectively calculated the initial voltage distribution, the distribution voltage of the impulse response, the maximum potential distribution and the gradient voltage of oil-duct under the impact of lightning shock,and the calculated results are compared with the results calculated by the currently software used in transformer production company to prove the validity of the calculation of the software.In this thesis, the power transformer wave process calculation software is developed , which can be used to analysis and calculation for various kind of winding form, capacity and voltage level of power transformer.