Calculation of Power Transformer Short-current Force Hongkui LI

Transcription

1 International Power, Electronic and Material Engineering Conference (IPEMEC 2015) Calculation of Power Tranformer Short-current Force Hongkui LI School of cience,shenyang Ligong Unierity,Shenyang, ,China Keyword: magnetic field; power tranformer; hort-circuit Force; finite element method Abtract. Thi reearch tudie the magnetic field and force on the winding of tranformer due to hort-circuit. Three dimenional finite element computation of three-phae power tranformer i carried out. The model deeloped hae been applied to power tranformer and the reult are erified experimentally. To erify the computation reult, they are compared with thoe obtained uing ANSYS oftware imulation. Introduction In thi paper a new optimal deign of occer robot control ytem which i baed on mechanical analye and calculation on the preure and tranmutation tate of chip kick mechanic, thi new control ytem with high preciion for peed control and high dynamic quality. One of major reaon for fault in power tranformer i deterioration of winding and inulation of conductor due to the ocillation reulted from the electrodynamic force. The oer-current and rated current reult in the aboe-mentioned force. Therefore, the tranformer coil mut be protected mechanically and connected to each other by ribbon and wedge. The tructural criterion for thi upport i generally thoe force that are generated by the maximum poible current [1]. A large tranient current during a hort-circuit apply abnormal electromechanical force upon the winding of tranformer that may damage the whole winding. Short-circuit force and reultant tree mut be predicted in the deign tage. Thee force mut be in the range that i pecified by manufacturer. The accurate ealuation of the magnetic field and the reulting force on power tranformer winding under hort-circuit i ery important for the deign of the deice. It enable, in particular, to aoid mechanical damage and failure during hort circuit tet and the power ytem fault. A the force grow rapidly with the tranformer rating their prediction i of crucial importance for the deign of ery large apparatu. In uch cae hort-circuit magnetic field and force tet under normal oltage are ery laboriou and expenie. The computation reult are compared with thoe obtained by application of finite element method. Caue of Short-Circuit Magnetic Field and it Current After a tranformer i connected to current pa a tranient mode and then reache the teady-tate mode. winding magnetic field of power tranformer i a typical 3D nonlinear eddy current problem with a multiply connected region. In the region of winding, the field equation and boundary condition i reflected the intenity of magnetic induction B.In the cae of frequency,ignore the impact of diplacement current. Maxwell equation a in H=J (1) B E=- (2) The author - Publihed by Atlanti Pre 276

2 B=0 (3) J=0 (4) Magnetization of ferromagnetic material i quite complicated. If we till write B= µ H (5) The permeability µ i function of magnetic field H and depend on the hitory of magnetization. The electric current denity i Where σ i called conductiity. Junction condition a in J= σ E (6) H 1 n= H 2 n (7) (8) B1 n = B2 n J1 n = J 2 n (9) E1 n = E2 n (10) In the eddy area, H(t) can directly from the ource current and the external applied magnetic field to calculate the current denity. That i calculated by the following relationhip H=J (11) B E = (12) We conider a part inide the urface of a magnetized body a hown in Figure 1. For calculating the magnetic force acting on thi part, the magnetic material inide i eparated from the ret of the magnetic material by mean of an imaginary gap of infiniteimal width. The magnetic force i the rate of change in magnetic energy when the magnetic medium i undergoing an incremental diplacement with the magnetic excitation held fixed. The magnetic and elatic propertie of ferromagnetic and other material depend on each other. The different coupling between thee propertie are called magnetoelatic effect. Thee effect can be eparated into two main categorie, namely direct effect and inere effect According to the principle of irtual work, the magnetic energy i gien a f f w = did did (13) Where w i irtual work, δ i i irtual peed of tranfomer iron The total magnetic force F acting on any part of the tranfomer i calculated from the magnetic energy W a W F = u = f d + Where u i the ector of irtual diplacement in the conidered coordinate ytem f d (14) µ f = J B - H µ + H τ 2 (15) 2 τ Prepare Finite Element Method for Force Computation Maxwell tre tenor i ued for force computation by finite element method, in thi paper, ANSYS finite element analyi method of three-dimenional on SZ parameter of power tranformer i hown a table I. 277

3 Table I. Parameter of Power tranformer Winding inner diameter external diameter turn window High Phae current (A) HV LV Baed on the aboe parameter, Mehing of three-phae power tranformer with pecification are gien in Figure 1. Fig.1. one-half mehing model of finite element A. Inruh Current Force To erify the alidity and reliability of aboealgorithm, ome experiment on SZ /66, uch a witching unloadtranformer, witching unload tranformer with a mallturn-to-turn fault a well a turn-to-turn fault duringnormal running, are completed on an Yn/Δ-11 tranformerbank. The other experiment, uch a the aturation ofcurrent tranformer when witching unload tranformer,are carried on another Yn/Δ-11 tranformer bank. Theparameter of the former are gien a follow, ratedcapacity 40000kVA, rated oltage in primary winding66kv, rated oltage in econdary winding 10.5V,rated current in primary winding 275.6A, teady magnetizing inductance 5.37H. Figure2 how the Inruh current in different cae. Switching angle i zero(t=0.058), remanent magnetim of three-phae are (A-phae=0.8Wb/m2,B-phae=-0.4 Wb/m2,C-phae=0.4 Wb/m2) A i(a) C B t() Fig.2. α=0rad Br i[0.8,-0.4,0.4]pu Change of force on bilateral winding during dynamic tate i hown in Figure 3 and Figure

4 Fig.3. Upper end of winding Fig.4. Lower end of winding B. Short-circuit Force There i little electrodynamic force in axi direction of both inner and outer winding.moreoer, there exit puhing force between adjacent pie or turn ofwinding. Epecially, the enormou hort-circuit electrodynamic force will make the winding ditorted, the HV oltage winding phae current during two-phae hort-circuit i hown in Figure5.Axial hort-circuit force ign on the HV winding of the three-phae tranformer with pecification i gien in Figure Current / ka phae a phae b phae c Time / Fig.5. HV oltage winding phae current Fig.6. Ditribution of radial magnetic force Since the tranformer core normally enter a tate of aturation, the magnitude of inductance i reduced, the current increae quickly due to the decreae in inductance. Thi phenomenon ha the ome dangerou effect. Intant in time when oltage i zero during continuou operation. Since the core non-linear doe not take into account and Sinuoidal input oltage therefore the ue of tranient analyi. Three-phae current include primary A-phae current i curra, B-phae current i currb and C-phae current i currc. Concluion In thi paper, The etablihment of a iron decription of inuoidal electromagnetic field in the mechanical propertie of the mathematical model are built.according to electromagnetic field theory and elaticity theory. Formula for the calculation ofmagnetic and magnetotrictie force are alo deried. The implemented method i ued to computethe ibration of the iron of tranformer under the effect of magnetic and magnetotrictie force. The effect of coupling between the magnetic and elatic field i alocomputed for power tranformer. The magnetic force mean here the interaction between the magnetic and elatic field in the iron part of a tranformer. magnetotriction i the phenomenon by which an iron part change it dimenion under the effect of a magnetic field. The reult how that the Electromagnetic force and the magnetotrictie effect 279

5 i the phenomenon of different,it i important to etablih mathematic model. We can reearch ibration and noie characteritic of the power tranformer. Acknowledgement In thi paper, the reearch wa ponored by The general project of cience and Technology Education Department of Liaoning Proince (Project No. L ) Reference [1] K. Delaere, W. Heylen, K. Hameyer, and R. Belman, Local magnetotriction force for finite element analyi,,ieee Tran.Magn., Vol..36, pp , Set [2] Dapino, M. J., Smith, R. C. and Flatau, Structural Magnetic Strain Model formagnetotrictie Tranducer, IEEE Tranaction on Magnetic, Vol. 36, pp May [3] L. Vandeelde and J. A. A. Melkebeek, Modeling of magnetoelatic material, IEEE Tran. Magn., ol. 38, pp , Mar [4] Jile, D. C. 1995, Theory of the Magnetomechanical Effect, Journal of Phyic D: Applied Phyic, Vol. 28, 1995, pp [5] M. J. Sablik, and D. C. Jile, Coupled Magnetoelatic Theory of Magnetic and Magnetotrictie Hyterei, IEEE Tranaction on Magnetic, Vol. 29, No. 3, July 1993, pp