Abstract
When the electromagnetic transients occur in a power transformer, an inrush current is generated in its winding. The inrush current not only affects the performance of the transformer windings, but also affects the lifetime of the transformer. Many factors affect the inrush current, the most influential ones among which are the closing phase angle and the residual flux. In this paper, a dry-type transformer simulation model is built to analyze the influence of the inrush current on the performance of transformer windings during no-load reclosing conditions. Firstly, the inrush current was generated in the transformer windings during the no-load reclosing operation under different residual fluxes. Secondly, the field-circuit coupling 3d finite element method is used to analyze the electromagnetic force at different locations of the transformer windings under the influence of different inrush currents. The results of winding structural parameter variations are obtained through electromagnetic-structural coupling simulation, and the electromagnetic forces are used as the input parameter for the structural analysis. Finally, the residual flux is generated by controlling the opening and closing angle of the transformer through the phase-controlled switch, and the winding electromechanical characteristics are tested under different residual fluxes. Finally, comparisons of the test and simulation results are drawn to verify the impact of the closing angle and residual flux on inrush current and the winding deformation during the no-load reclosing conditions.
Highlights
When a power transformer is cut out of the system, a certain amount of residual flux will be generated due to the hysteresis characteristics of the core material
A simulation circuit was built to obtain the peak inrush current generated during no-load reclosing under different residual fluxes of the transformer core
The electromechanical characteristics of the transformer winding under the influence of the inrush current generated during no-load reclosing are analyzed using the field-circuit coupling and the finite element method
Summary
When a power transformer is cut out of the system, a certain amount of residual flux will be generated due to the hysteresis characteristics of the core material. They built a core detection circuit for ring transformers, processes the experiments to obtain transient measurement current signals, and substituted the results into the residual flux and current relationship equation This method was able to obtain the residual flux in the core of power transformers more accurately. This paper uses the phase-controlled switching technique to control and calculate the residual fluxes of the transformer core under different closing phase angles, as well as to analyze the peak excitation inrush currents and their effect on the transformer windings generated under different residual fluxes. A simulation circuit of the power transformer is established to analyze and obtain the inrush current under the no-load reclosing condition of the transformer with different residual fluxes. The “field-path” coupling method and finite elem4eonf 2t2 method are combined to analyze the electromagnetic force of the transformer winding under the inrush current corresponding to different residual fluxes. The power trwaninsfdoirnmgeurnedleecrtrthome iangrnuesthicc-sutrrruecnttucraolrrceosuppolnindginagnatolydsiisffmeroendtelreissiedsutaabl lflisuhxeeds.toAaftnearlythzaet, ththeedpefoowrmerattrioannsofof rtmheerweilnedctinrogmstarguncetutirce-s. tTruhectnu,rbaalsceoduopnlinthgeasniamlyusliastimonodreesluisltess, ttahbelipsahre-d amtoeatrnicalryezlaetitohneshdiepfsorbmetawtieoenn orfestihdeuawl ifnludxinagndstcrulocstiunrge.phTahseena,nbgaleseadndonelethcterosmimauglnaettiiocn forrecseulatsn,dthwe ipnadrianmgedtreicforremlaattioionnshairpes boebttwaieneend.reFsiindaulalyl,fltuhxe avnadlicdliotysinogf pthheasseimanugllaetiaonnd meelethctordomanadgntheeticcoforrreccetnanesds wofinthdeinrgesdueltfsoramreavtieornifiaerde boybteaxinpeedri.mFeinnatsl.ly, the validity of the simulation method and the correctness of the results are verified by experiments
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