Modeling And Characteristic Study Of Wound Core With Short Circuit Fault

With the growing maturity of large-scale wound core manufacturing technology,wound core transformer is playing an increasingly important role in power system and traction power supply system.At the same time,due to its excellent loss-reduction performance,it brings good economic benefits to the society.The short circuit faults of the core occupie a very high proportion in the transformer fault,making huge harm.The insulation performance is reduced and the loss is increased when short-circuit faults occur.In severe cases,it even burns the core,resulting in power failure.However,because the wound core is in the initial stage of the application,domestic and foreign scholars have less research on the characteristics of wound cores’ short circuit faults.Therefore,it is necessary to study the characteristics of the wound core based on the study of the short circuit fault of the laminated core,furtherly evaluates the severity of the damage,at last provides reference for the project site.Firstly,according to the structure of the wound core,original anisotropy formula has been modified and the modeling method in eddy current field is proposed,then the wound core 3D eddy current field calculation model is established.The eddy current loss calculation equation is used to verify the validity of the model and relevant simulation analysis is performed.In the engineering case,the eddy current loss is calculated for the OD-R-32000/55 auto-transformer,then compare the measured value and the calculated value to verify its applicability in the project.Secondly,the homogenization modeling methods of the laminated core considering interlaminar faults and multi-point grounding faults are proposed,and relevant three-dimensional eddy current field models are established.The distribution of the flux inside the core and the eddy current loss distribution in the fault region are simulated and analyzed when interlaminar faults occurs.The simulation results are verified by the classical equivalent circuit method,and the validity of the model is proved.The distribution of the eddy current in the laminated core and the macroscopic value of fault currents are calculated and analyzed when the multi-point grounding faults occur,and the accuracy of the model is verified by comparing with the test values of the laminated core with multi point grounding fault.Finally,based on the structure of the wound core and the principle of two kinds of short circuit fault,the homogenization methods of wound core with the faults are proposed,and three dimensional eddy current field fault models are established.The distribution of the flux inside the core,eddy current and eddy current loss in the fault zone are simulated and analyzed for the wound core with interlaminar faults.And the simulation results are compared with the results of the laminated core with interlaminar faults,it shows that the fault severity is far less than the iron core when the interlaminar fault occurs in the same working condition.The macroscopic fault current value of the wound core is compared with the test multi-point grounding fault value,the accuracy of the model is verified.The fault current value of the multi-point grounding fault of the wound core are calculated,and the results are compared with the calculation results of the laminated core with the same size.It shows that the fault degree is more serious when the wound core has multi-point grounding faults.