SIMULATION OF ELECTROMAGNETIC PHENOMENA DUE TO INDIRECT LIGHTNING STRIKES ON WIND TURBINES

Transcription

1 SEF 2 - XV nterntonl Symposum on Eletromgnet Felds n Mehtrons, Eletrl nd Eletron Engneerng Funhl, Mder, Septemer -3, 2 SMULATON OF ELECTROMAGNETC PHENOMENA DUE TO NDRECT LGHTNNG STRKES ON WND TURBNES R.B. Rodrgues, V.M.F. Mendes, J.P.S. Ctlão 2,3 nsttuto Superor de Engenhr de Lso, Lson, Portugl 2 Unversty of Ber nteror, Covlh, Portugl, E-ml: tlo@u.pt 3 Center for nnovton n Eletrl nd Energy Engneerng, ST, Lson, Portugl Astrt Ths pper s onerned wth the smulton of eletromgnet phenomen due to ndret lghtnng strkes on wnd turnes. Lghtnng dmges nvolvng wnd turnes hve ome to e regrded wth nresng onern. The wnd power generton s rpdly growng n Portugl, ut stll there re few studes onernng the lghtnng proteton of wnd turnes usng models of the Eletro-Mgnet Trnsents Progrm, restrutured verson. Hene, se study s presented n ths pper usng EMTP-RV for modellng nd smulton, thus hghlghtng the need for dequte proteton mesures gnst trnsent overvoltges. ntroduton The need to ontrol lmte hnges nd the dependene n fossl-fuel osts stmulte the evergrowng use of renewle energes worldwde. Conernng renewle energes, wnd power s prorty for most ountres expressed n ther energy strtegy []. The new Portuguese Strtegy for Energy, ENE 22, pproved t Aprl 5, 2, estlshes tht 3% of the fnl energy should e otned from renewle soures n 22. The gol s to reh 85 MW of nstlled wnd power pty n 22. As wnd power generton undergoes rpd growth, lghtnng ndents nvolvng wnd turnes hve ome to e regrded wth more ttenton [2]. Lghtnng s n ft tremendous phenomenon of nture, s eutful s dngerous. The ndene of lghtnng strokes s very serous prolem [3], s t n produe dngerous overvoltges. An effetve lghtnng proteton system should protet not only gnst the dret effets of lghtnng, ut lso gnst ts ndret effets. Lghtnng proteton of wnd turnes presents prolems tht re not normlly seen wth other strutures [4]. Modern wnd turnes re hrterzed not only y greter heghts ut lso y the presene of ontrol nd proessng eletrons. Consequently, the desgn of the lghtnng proteton of modern wnd turnes s hllengng prolem [5]. The future development of wnd power generton nd the onstruton of more wnd frms wll neesstte ntensfed dsusson of lghtnng proteton nd the nsulton desgn of suh fltes [6]. Nevertheless, there re stll few studes n Portugl regrdng lghtnng proteton of wnd turnes usng models of the Eletro-Mgnet Trnsents Progrm, restrutured verson (EMTP-RV). Ths softwre llows desrng the trnsent ehvour of power systems n n urte wy. Also, surge propgton durng lghtnng strkes t wnd frms loted n Portugl s stll fr from eng lerly understood, gven tht the Portuguese Lghtnng Loton System (LLS) [7] s n operton only sne 23, thus muh work remns to e done n ths re. Hene, n ths pper, the possle dmges due to trnsent overvoltges ndued y ndret lghtnng strkes on wnd turnes re studed usng EMTP-RV. A se study s presented, sed on wnd turne wth n nteronnetng trnsformer, onsderng tht lghtnng strkes the sol ner the tower t dstne suh tht glvn ouplng ours through the groundng eletrode. Computer smultons llustrte the eletromgnet phenomen nd onlusons re duly drwn.

2 Wnd Turne A wnd turne wth 2 MW of rted power s onsdered. The rotor dmeter s out 82 m. The hu heght vres etween 7 to 38 m. The LV/HV trnsformer s pled t the ottom of the turne. t hs 25 kva of rted power nd hs spel desgn to ft the redued dmensons nd workng ondtons of the turne. The wnd turne shown n Fgure ws modelled n 3D wth AutoCAD. Fg. Dmensons of the wnd turne The wnd turne model s hrterzed y: 69 V synhronous genertor, suffently stle t 5 Hz, s onsdered; 69 V / 2 kv oost trnsformer s pled nsde the wnd turne or nstlled rther lose to the wnd turne; jont groundng of the prmry nd seondry sde s ssumed; the trnsformer model onsders only eletromgnet trnsfer, onsderng surges only wth reltvely long perods exeedng μs; the stt trnsfer s gnored; the nteronneton to the power grd s through 2/6 kv trnsformer; the groundng resstne onsdered for the eletrode n the sene of lghtnng urrents s Ω. n ddton, stndrd lghtnng urrent wveform s onsdered wth wve front durton of μs, wve-tl durton of 35 μs, nd pek vlue of ka. Ths s euse, n Portugl, 8% of lghtnng strkes hve pek urrent hgher thn 8- ka [7]. Lghtnng strkes the sol ner the tower t dstne suh tht glvn ouplng ours through the groundng eletrode. Method nd Models The EMTP hs een used to study trnsents n lrge sle power systems or n rtrry eletrl networks. n ths pper the most reent verson, EMTP-RV, s ppled. The omplete softwre s lso nmed EMTP/EMTPWorks, where EMTP desgntes the omputtonl engne [8]. The followng explns refly the most mportnt models used n ths pper. Lghtnng urrent soure The CGRE deve s n EMTP-RV model tht ws hosen to smulte the urrent lghtnng soure. Ths deve s used for urte lultons of the lghtnng performne of equpment. The urrent front of the frst stroke s gven y: n = At Bt () Where: mx A =.9n Sm (2) n tn

3 B = ( ) ( S t.9 ) m n mx (3) n tn n The urrent tl equton s gven y: ( t tn ) ( t tn ) t t2 = e 2e (4) Equton (4) s used when EMTP enters the tl zone t Wnd tower struture t t n t. To model the lde nd the tower of wnd turne, the Constnt Prmeter (CP) lne s used, whh s frequeny ndependent trnsmsson lne model. For the purpose of ths pper, the CP lne model n e suessfully used. The frequeny dependene of the prmeters ws lso not onsdered n [9], euse the uthors onluded tht t hs sre nfluene on the trnsent responses of the tower system. Besdes, some studes hve shown tht the skn effet hs lttle nfluene on the lghtnng trnsent response. The CP lne s dstruted prmeter model. The s equtons of the sngle phse dstruted prmeter lne re: dv ( x, d ( ) ( x, = R' x, t L' (5) dx dt d ( x, dv ( ) ( x, = G' V x, t C' (6) dx dt The CP lne prmeters re lulted t gven frequeny, whh s etter to tke t ove MHz [], nd tht s why t s leled s frequeny ndependent. The CP lne prmeters were lulted tkng nto ount tehnl nformton from the mnufturer, suh s, mterl hrtersts nd dmensons of omponents. Ground eletrode The ground eletrode model used n ths pper s very often used wth lghtnng smulton purposes for HV trnsmsson lnes nd towers. t onsders nonlner resstne usng ontrolled resstne nd dmttne. The presene of the urrent soure provdes n opton for retng peewse lner resstne funton. Any segment k of suh funton n e represented y the Norton rut equvlent: k = k vk k (7) The k s tully the dervtve t the opertng pont k: k k = (8) vk When usng the sme ground eletrode for sfety nd serve purposes, the Portuguese regulton requres mxmum vlue for erth resstne of Ω. Ths vlue s ssumed n the sene of lghtnng urrent flowng through t. Surge rrester The s rrester model equton s gven y (9), where s the rrester urrent nd v s the rrester voltge: α = k v (9) For SC (Slon Crde) rresters the vlue of α s etween 2 to 6. For MO (Metl Oxde) rresters the vlue s α 6. The k prmeter s onstnt used n the fttng proess. strt

4 Crut nd Results n frst pproh, the EMTP-RV rut s onsdered wthout surge protetve deve (SPD), s shown n Fgure 2. nsde the wnd turne 69 VRMS genertor (SM) produes eletrl energy whh s delvered to the mn power trnsformer (D_2) nd to the uxlry trnsformer (D_). The D_ trnsformer feeds eletron ontrol equpment (Rn, Rn3 nd Rn4). Lghtnng strke Surfe 4 m3 A? Blde gre2 ka/us 75 Tower Synhronous mhne.975kv SM 2MVA m2 SM.nF C C4 C3 Cptve ouplng VM.nF.nF CleVV G35 (35 m) R3 22m L3 4uH Power trnsformer D_2 Auxlry trnsformer D_ 2.975/ /28 VM m4 m5 VM VM VM m6 m7 VM m9 Rn Rn3 Rn4 Non lner lod m VM Underground f(u) Fm Rn2?> Ground eletrode Fg.2 EMTP-RV rut wthout SPD Fgure 3 presents the shpe of the overvoltge t the prmry sde of trnsformers. The pek vlue of overvoltge surpsses kv. Fgure 4 presents the shpe of the overvoltge t the seondry sde of the mn power trnsformer. Fg.3 Overvoltge t the prmry sde of trnsformers Fg.4 Overvoltge t the seondry sde of the mn power trnsformer Fgure 5 presents the shpe of the overvoltges t the eletron ontrol equpment. The pek vlue of overvoltge rehes lmost kv, whh s more thn ths knd of equpment n support.

5 Fg.5 Overvoltge t the seondry sde of the uxlry trnsformer n these ondtons, n dequte SPD s neessry to lmt the voltge elow n eptle level, s shown n Fgure 6. Lghtnng strke Surfe 4 m3 A? Underground f(u) Blde Fm gre2 ka/us 75 Tower Synhronous mhne.975kv SM 2MVA m2 SM C4 Cptve ouplng CleVV G35 (35 m) R3 22m L3 4uH Rn2?>.nF C C3 Ground eletrode VM.nF.nF Power trnsformer D_2 Auxlry trnsformer D_ 2.975/ /28 kv ZnO ZnO VM m4 m5 VM Fg.6 EMTP-RV rut wth SPD R VM VM m6 m7 VM m9 Rn Rn3 Rn4 Non lner lod m VM Fgure 7 presents the shpe of the overvoltge t the seondry sde of the mn power trnsformer. The pek vlue of overvoltge s nferor, ut stll notele. Fg.7 Lmted overvoltge t the seondry sde of the mn power trnsformer wth SPD Fgure 8 presents the shpe of the overvoltges t the eletron ontrol equpment wth SPD. The pek vlue of overvoltge rehes lmost 6 kv, whh s stll more thn ths knd of equpment n support. Hene, only wth perfet SPD onneton the overvoltge ould remn elow the upper lmt supported y the ontrol equpment.

6 Fg.8 Overvoltge t the seondry sde of the uxlry trnsformer wth SPD Conlusons Ths pper presents se study, sed on wnd turne wth n nteronnetng trnsformer, onsderng tht lghtnng strkes the sol ner the tower t dstne suh tht glvn ouplng ours through the groundng eletrode Computer smultons, otned y usng EMTP-RV, llustrte the eletromgnet phenomen. Referene vlues of nterntonl stndrds hve een dpted to Portuguese relty. Nevertheless, results re lso true for other ountres. The pek vlue of the overvoltge rehes lmost 6 kv t the eletron ontrol equpment, even wth SPD nstlled. Ths ours euse the onneton of SPD to ground s not del. To redue the overvoltge to n eptle vlue, SPD n dfferentl mode ould e nstlled. Aknowledgment The uthors would lke to thnk Prof. A. Mhdo e Mour for hs vlule omments. Referenes [] R.B. Rodrgues, V.M.F. Mendes, J.P.S. Ctlão, Eletromgnet trnsents nlyss on wnd turnes durng lghtnng strkes, SEF 29, Arrs, Frne, Septemer 29. [2]. sud, et l., Surge nlyss on wnd frm when wnter lghtnng strkes, EEE Trns. Energy Converson, Vol. 23, pp , 28. [3] B. Glushkow, Effetve lghtnng proteton for wnd turne genertors, EEE Trns. Energy Converson, Vol. 22, pp , 27. [4] EC, Wnd turne generton system 24: Lghtnng proteton, Teh. Rep. TR64-24, 22. [5] F. Rhd, et l., A revew of urrent ssues n lghtnng proteton of new-generton wnd-turne ldes, EEE Trns. ndustrl Eletrons, Vol. 55, pp , 28. [6]. sud, T. Hr, T. Funsh, Anlyss of lghtnng surge propgton n wnd frm, Eletrl Engneerng n Jpn, Vol. 62, pp 3-38, 28. [7] R.B. Rodrgues, V.M.F. Mendes, J.P.S. Ctlão, Lghtnng dt oserved wth lghtnng loton system n Portugl, EEE Trns. Power Delvery, Vol. 25, pp , 2. [8] J. Mhseredjn, et l., On new pproh for the smulton of trnsents n power systems, Eletr. Power Syst. Res., Vol. 77, pp 54-52, 27. [9] X.H. Wng, X.Q. Zhng, D.S. ng, An effent lgorthm of trnsent responses on wnd turne towers struk y lghtnng, Compel-nt. J. Comp. Mth. Eletr. Eletron. Eng., Vol. 28, pp , 29. [] K. mmoto, et l., Expermentl nd nlytl studes of lghtnng overvoltges n wnd turne genertor systems, Eletr. Power Syst. Res., Vol. 79, pp , 29.