Calculation And Analysis Of Wave Process Of Multi-winding Power Transformer

The calculation of the transformer winding wave process under the lightning impulsehas great significance for designing insulation structure. In order to simplify calculationprocess, single winding and duplex winding equivalent circuit have always been used tobuild model. This method has some limitations for analyzing wave process. Meanwhile,assessment of insulation has certain deviation because of ignoring the influence of theresult. The method of quickly building multiple winding equivalent circuit and generatingcoefficient matrix is presented through the research on three-winding equivalent circuitmodel, and based on this, a calculation software with the characteristic of wide range ofapplication and simple operation is developed.Firstly, lumped parameter of wave process on solving is studied, and then thecalculation of inductance and capacitance has a great influence on the calculation results.The finite element method is used to analyze and modify the each part of the capacitanceafter various forms of capacitance parameter have been given. The method of energy equaleffects is used to deduce a variety of winding form of equivalent longitudinal capacitance.Infinite long core model is used to calculate inductance parameter. Determine the corepermeability by calculating core inductance component of the different core permeability.In order to confirm the correction coefficient of inductance, the method to compareanalytic formula and finite element analysis results is used. Secondly, equivalent circuit ofordinary three winding transformer model is established. The method of rapid generationcut set coefficient matrix and direct method of solving differential equations are presented,and based on this, the calculation program is wrote which is suitable for various types oftransformer wave process. The wave process of high impedance transformer on-loadregulating auto-transformer is calculated. The calculated value, experimental value andenterprise value were compared to test practicability and accuracy of the program. Finally,an easy operation, simple used and wide range of application wave process calculationsoftware is developed by using Matlab as the core program and the Visual Basic as thesoftware man-machine interface. This software can be used for analyzing various types of transformer and calculating different winding structure and end node connection mode. Inorder to prove the significance of wave process calculation software for designinginsulation, this software is used for calculating the maximum potential distribution andpotential gradient of no excitation regulating transformer and load regulating transformerunder full wave and chopped wave. The insulation safety margin under the lightningimpulse is analyzed and the results provide reference for engineering practice.