Simulation Research On The Electromagnetic Characteristic Of Transformer Based On The Field-circuit Coupling

Power transformer is indispensable electrical equipment in the power system,and its manufacturing industry has also developing rapidly because of the growing demand of the global power industry.With the more and more severe requirement of power quality and the rapidly increasing awareness on energy conservation and environmental protection,power customers put forward higher requirement of the performance of the transformer products.During the design process of the transformer body,design workers mostly adopt the traditional methods such as empirical formula,which can not predict the performance parameters of the transformer accurately and can not make better effect on late optimization,such as thermal verification having a greater influence on the safe operation of the transformer.Transformer forecast analysis of all kinds of performance parameters depends on internal electromagnetic performance calculation of the transformer.Thus,this thesis aims to study internal electromagnetic properties and thermal calculation of transformer under different operation condition,and analyze the influence of the power system operation condition to transformer performance.The two elements of transformer thermal calculation are internal thermal environment analysis and internal loss calculation.As transformer internal heat source,loss is the main source and prerequisites of heat production.It is necessary to calculate internal electromagnetic properties accurately for the prediction of the transformer internal loss.A 50MVA/110 kV oil immersed power transformer is set for an example in this thesis.And this thesis focus on the analysis of electromagnetic performance,where transformer is under different operating conditions.Firstly,on the basis of basic assumptions and simplification,the physical model of transformer is established.Based on the finite element theory and the field-coupled method,this thesis calculates internal electromagnetic property of transformer running under different working conditions.According to the results of calculation,this thesis analyses the instantaneous changes about the induced voltage and current in the transformer windings,and studies the distribution rule of magnetic induction in transformer core and winding.Then the three phase iron cores of transformer were modeled individually,to calculate three-phase core loss,high and low voltage winding loss of transformer under different conditions and analyze the influence of different operating conditions to the internal loss of the transformer.Finally,the internal loss of the transformer is considered heat source,based on the theory of fluid mechanics and heat transfer,using the finite volume method and transformer physical model used in the magnetic field calculation,on the basis of the relevant assumptions,the temperature field of the transformer is calculated,and the internal temperature distribution rule of transformer under different working conditions is explored.