The Study Of High Frequency Modeling And Voltage Distribution Of Transformer Windings Suffering Impulse Surge

Impulse surge test is a routine test of power transformer, whic h inc ludes standardlightning imp ulse test, standard chopped lightning impulse test and switc hing impulsetest. When a steep fro nt surge invades trans former wind ings along the powertransmiss io n line, the wind ing could fa il if the ins ulation is designed improperly. Theimpulse surge is of these characteristics tha t contain steep fro nt, fast shift and highfrequenc y, which will threaten the safety running of trans formers and otherequip ments connected to the trans miss ion line. To study volta ge distributio n intransformer wind ings and modeling method is of great significa nce for trans formerinsulation design.This paper focuses on the following study fields:First, different methods used by domestic and fore ign researchers are introducedwhen modeling the transformer wind ing suffering a impulse surge. After comparingand analyzing these different methodolo gies, the advanta ges and disadvanta ges andtheir applied area are listed.Second, typica l coil structure and insulation type of trans former is introduced inchapter2. The generation princ iple of impulse surge and its harm to power appratus iselaborated, and then the approach of how to generate such a surge in laboratory isgive n. At the same time, the instruments whic h are needed for the generatio n andmeasure ment o f this impulse surge are enumerated. Natio nal standard of trans formerinsulatio n test is a lso introduced in this chapter. Algorithm on the basis of newtoniterative a lgorithm to co mpute the parameters of full standard lightning impulse isdetailly deduced. Lastly, the full standard lighting impulse wave is shaped through theplatform of Matlab Simulink.Third, the finite eleme nt method is used to the calc ulate distrib ution parameter oftransformer winding. Based on these parameters, the trans fer function o f one turn inthe wind ing can be comp uted by so lving the MTL equatio n, and another way us ingthe instrument to obta in the transfer function curve is also reco mmended. In order toget a ratio na l function, the a lgorithm of vector fitting is exp loited to fit the curve.The accuracy and va lidity o f vector fittin g is demo nstrated by fitting a real exa mp le.Lastly, the vo ltage response in trans former winding is shaped through theconvolution between the voltage transfer functions and the excitation.Fourth, Arno ld i order-reduced algorithm is used to reduce the order of initia l transfer function, and the n the order-reduced trans fer functio n is s ynthes ized to acircuit mode l which is only co mposed of passive e leme nts R, L, C and idealtransformers. By comparing these two wave responses, one is calculated by initia ltransfer function a nd the other is computed by order-reduced transfer function, itproves that the arno ldi a lgorithm has hardly varied the chacteristics of thetramsmission system.Fina lly, the emp irica l fo mula to calculate the resonce frequceny of trans for merwind ing is give n. A new method is used to loacate the resonce freque ncy, which isbased on the ma gnitude-freque ncy curve of tra nsfer functio n. The shape of responsewave validates this high frequency model and precision of resonce frequency.