Analysis And Verification For Winding Hot Spot Temperature Rise For Power Transformer

Oil-immersed power transformer is the important equipment in power system.With the increase of power transformer capacity,heating and cooling problems of the transformer become more and more prominent.Winding as the major loss source in transformer,its local overheating will cause the insulation aged,thereby it will affect the life of insulating materials.If the transformer cannot work normally,it will cause huge economic losses,even endanger personal safety.Therefore,the calculation of winding hot-spot temperature rise has important engineering application value and practical significance in prevention of winding local overheating problem.Based on the finite element method,a two-dimensional axisymmetric model is established by using special software MF2 D,and the distribution of winding leakage magnetic field is obtained.On this basis,the eddy current loss for each partition of all winding is calculated,which provides the basic data to calculated winding hot spot temperature rise.On the basis of getting winding total losses,heating factor Q and cooling factor S are determined by using loss density and cooling efficiency respectively.Thus,analytic formula of hot spot factor is obtained,which improved the calculation method of hot spot temperature rise.The rationality of this calculation method was verified by typical transformer products measurement data.The software was developed to calculate hot spot and hot spot temperature rise,which provide a reference method of calculation for winding hot spot temperature rise.Finally,a two-dimensional model is established by using the fluid software FLUENT,and the model parameters such as material properties,boundary conditions are set.Eventually,the winding temperature field distribution and hot spot temperature are obtained by using finite volume method.The rationality of 2d calculation method is verified by comparing with optical fiber temperature data,and then validation of engineering calculation for winding hot spot temperature rise is confirmed by comparing the temperature field result.