Study On Loss Separation Of Oil Tank Wall And Structure Of Power Transformer

In this thesis,a three-phase power transformer with 380 MVA capacity is taken as an example,and the electromagnetic simulation calculation is carried out by using MagNet software.The characteristics of the distribution of the internal leakage magnetic field of the transformer on each structure are obtained,that is,the strong magnetic flux leakage area on each structural part is always close to the winding,for example,the position of the strong magnetic leakage area of the oil tank wall corresponds to the winding side,and that of the clamp and pull plate corresponds to the winding end.The magnetic shielding is used to reduce the magnetic field strength of the strong magnetic flux leakage area.Compare the change of magnetic flux leakage intensity between the structure with and without magnetic shielding,it can be found that the magnetic shielding effectively reduces the magnetic flux leakage intensity of the shielded structural parts.In order to study the shielding deeply,this paper compares and analyzes the shielding with different parameters,the thickness of magnetic shielding with the best shielding effect is determined,and the conclusion that the shielding effect of magnetic shielding is better than that of electric shielding is obtained.This thesis designs a double transformer image method loss separation test scheme,which can effectively separate the loss of oil tank wall and magnetic shield composite structure from the total loss of transformer.In this test scheme,the transformer that needs to be separated from loss is divided into two parts,in which the oil tank wall and magnetic shield form the tested structure together.The transformer after removing the oil tank wall and magnetic shield is renamed as the excitation transformer,and the magnetic leakage produced during normal operation will generate loss in the tested structure.A transformer that is identical with the excitation transformer is added The magnetic field generated by the mirror transformer is used to compensate for the change of the magnetic field environment of the tested transformer under the no-load condition(the double transformer operates without the tested structure)due to the removal of the tested structure.Magnetic shielding has high magnetic conductivity,so it can be approximately considered that the direction of magnetic flux on the surface of magnetic shielding is vertical,and the mirror transformer is placed in the position symmetrical to the excitation transformer,forming the no-load condition of mirror symmetry.Two dimensional and three-dimensional simulation calculation of load and no-load conditions in the loss separation test scheme of double transformer image method by using MagNet software.The simulation results show that the mirror transformer plays an effective role in magnetic flux leakage compensation of excitation transformer under no-load condition,which makes the magnetic flux leakage environment of excitation transformer under no-load condition and load condition basically the same The loss of the excitation transformer is basically unchanged under the two conditions.Since the no-load condition only includes the mirror transformer and the excitation transformer,and both of them are in the same leakage magnetic environment,half of the total loss of the no-load condition can be taken as equivalent to obtain the loss of the excitation transformer under the load condition,and then the total loss of the load condition can be used to subtract the loss of the excitation transformer to obtain the loss of the structure under test,which successfully realizes the loss of the tank wall and the magnetic shield The purpose of separating the loss from the total loss of the tested transformer also verifies the feasibility and effectiveness of the double transformer image method loss separation test scheme.