Protection of interconnected wind turbines against lightning effects: overvoltages and electromagnetic transients study

Transcription

1 1 Protetion of interonneted wind turines ginst lightning effets: overvoltges nd eletromgneti trnsients study R.B. Rodrigues, V.M.F. Mendes, J.P.S. Ctlão,, * Deprtmentl Are of Eletril Engineering nd Automtion, Instituto Superior de Engenhri de Liso, R. Conselheiro Emídio Nvrro, Lison, Portugl Deprtment of Eletromehnil Engineering, University of Beir Interior, R. Fonte do Lmeiro, Covilh, Portugl Center for Innovtion in Eletril nd Energy Engineering, Instituto Superior Ténio, Tehnil University of Lison, Av. Roviso Pis, Lison, Portugl Reeived 25 July 211; reeived in revised form 3 Mrh 212 Astrt This pper is onerned with diret or indiret lightning strokes on wind turines, studying overvoltges nd eletromgneti trnsients. As wind power genertion undergoes rpid growth, lightning dmges involving wind turines hve ome to e regrded with more ttention. With the im of providing further insights into the lightning protetion of wind turines, desriing the trnsient ehvior in n urte wy, the restrutured version (RV) of the eletromgneti trnsients progrm (EMTP) is used in this pper. A new se study is presented with two interonneted wind turines, onsidering diret lightning stroke to the lde or onsidering tht lightning strikes the soil ner tower. Comprehensive omputer simultions with EMTP-RV re presented nd onlusions re duly drwn. 212 Elsevier Ltd. All rights reserved. Keywords: Eletromgneti trnsients; Lightning protetion; Wind energy 1. Introdution Wind energy is one of the fstest growing renewle energy soures for power prodution [1], prtiulrly in Europen ountries suh s Irelnd [2], Denmrk [3] nd Portugl [4,5]. Lightning strokes on power supply systems n produe dngerous overvoltges nd dmges on equipments. Wind turines re espeilly vulnerle to lightning, whih n use signifint dmge to wind turine omponents [6]. Aville sttistis revel tht etween 4% nd 8% of Europen wind turines re dmged y lightning every yer [7]. * Corresponding uthor t: Deprtment of Eletromehnil Engineering, University of Beir Interior, R. Fonte do Lmeiro, Covilh, Portugl. Tel.: ; fx: E-mil ddress: tlo@ui.pt (J.P.S. Ctlão).

2 2 Effetive lightning protetion of wind turines is inresingly importnt nowdys [8,9], sine res of fvorle lotions for wind turines often oinide with res of signifint thunderstorm tivity [1,11]. Moreover, the eslting numer of wind turines in mny ountries Portugl mkes their reliility nd sfety of ruil importne [12,13]. Lightning protetion of wind turines presents prolems tht re not normlly seen with other strutures. These prolems re result of the following [14]: (i) (ii) Wind turines re tll strutures of more thn 15 m in height; Wind turines re frequently pled t lotions very exposed to lightning; (iii) The most exposed wind turine omponents suh s ldes nd nelle over re often mde of omposite mterils. Although nowdys most of the wind turine systems do hve inuilt lightning protetion systems, the lightning urrent is still le to produe severe dmges; (iv) The ldes nd nelle re rotting; (v) The lightning urrent hs to e onduted through the wind turine struture to the ground, wherey signifint prts of the lightning urrent will pss through or ner to prtilly ll wind turine omponents; (vi) Wind turines in wind frms re eletrilly interonneted nd often pled t lotions with poor grounding onditions. Modern wind turines re hrterized not only y greter heights, ut lso y the presene of everinresing ontrol nd proessing eletronis. Consequently, the design of the lightning protetion of modern wind turines remins hllenging prolem [7]. The future development of wind power genertion nd the onstrution of more wind frms will neessitte intensified disussion of lightning protetion nd the insultion design of suh filities [15]. Nevertheless, there re still very few studies in Portugl regrding lightning protetion of wind turines using sophistited numeril odes. Also, surge propgtion during lightning strikes t wind frms loted in Portugl is still fr from eing lerly understood, given tht the Portuguese Lightning Lotion System (LLS) is in opertion only sine 22, thus muh work remins to e done in this re. Diret nd indiret lightning strokes n produe dmges nd/or mlfuntions of the relevnt eletril nd mehnil omponents [16]. Sttistis of wind-turine dmges due to lightning hve een nlyzed in the literture, long with the relevnt risks [17]. An effetive lightning protetion system should protet not only ginst the diret effets of lightning, ut lso ginst its indiret effets.

3 3 Sle models of eletril systems hve een populr tool to predit trnsients fter different types of perturtions [18]. For instne, 3/1-sle model of n tul wind turine tht hs ldes with length of 25 m nd turine tht is 5 m high ws onsidered in [19,2] for experimentl nd nlytil studies of lightning overvoltges. However, in reent yers, sle models hve een progressively repled y sophistited numeril odes ple of desriing the trnsient ehvior in n urte wy, suh s the EMTP-RV, whih designtes the restrutured version (RV) of the eletromgneti trnsients progrm (EMTP) [21]. In this pper, new se study is presented with two interonneted wind turines, onsidering diret lightning stroke to the lde or onsidering tht lightning strikes the soil ner tower. Comprehensive omputer simultions with EMTP-RV re presented nd onlusions re duly drwn. This pper is strutured s follows. Setion 2 presents the desription of the wind turines. Setion 3 explins the EMTP-RV modeling. Setion 4 illustrtes the results otined. Finlly, onluding remrks re given in Setion Wind turines desription Wind turines with 2 MW of rted power re onsidered. The hu height vries etween 7 to 138 m. The rotor dimeter is out 82 m. The rotor hu nd nnulr genertor re diretly onneted to eh other s fixed unit without gers. The rotor unit is mounted on fixed xle. The drive system hs only two slow-moving roller erings due to the low speed of the diret drive. The nnulr genertor is lowspeed synhronous genertor with no diret grid oupling. The output voltge nd frequeny hnge with the speed, implying the need for eletroni frequeny onversion in order to mke onnetion to the eletri grid. The LV/HV trnsformer is pled inside the tower t the ottom. It hs 25 kva of rted power nd hs speil design to fit the redued dimensions nd working onditions of the tower. The wind turines were modeled in 3D with AutoCAD, s shown in Fig. 1. Ensuring proper power feed from wind turine into the grid requires grid onnetion monitoring, shown in Fig. 2. The eletril sheme of LV/HV susttion inside the tower is shown in Fig. 3. "See Fig. 1 t the end of the mnusript". "See Fig. 2 t the end of the mnusript". "See Fig. 3 t the end of the mnusript".

4 4 The wind turine model is hrterized y: (i) (ii) A 69 V synhronous genertor, suffiiently stle t 5 Hz, is onsidered; A 69 V / 2 kv oost trnsformer is pled inside the tower; (iii) The trnsformer model onsiders only eletromgneti trnsfer, nd stti trnsfer is ignored; (iv) The interonnetion to the power grid is through 2/6 kv trnsformer; (v) The grounding resistne onsidered for the erth eletrode in the sene of lightning urrents is 1 Ω. In ddition, stndrd lightning urrent wveform is ssumed with wve front durtion of 1 μs, hlf wve-til durtion of 35 μs, nd pek vlue of 1 ka. The pek vlue onsidered is euse, in Portugl, 8% of lightning strikes hve pek urrent higher thn 8-1 ka [13]. 3. EMTP modeling The EMTP hs een extensively used to study trnsients in lrge sle power systems. In this pper, the most reent version (EMTP-RV) is pplied. The omplete softwre is lso nmed EMTP/EMTPWorks, where EMTP designtes the omputtionl engine [21]. The following explins riefly the most importnt models used in this pper. 3.1 Lightning urrent soure The ICIGRE devie ws hosen to simulte the urrent lightning soure. This devie is used for urte lultions of the lightning performne of equipment. The urrent front of the first stroke is given y: n I At Bt (1) where A nd B re given y: 1 I A.9n n 1 t mx n S m (2) 1 B (3) n t n S.9 mtn Imx n 1 The urrent til eqution is given y: t tn ttn t1 t2 I I e I e (4) 1 2 Eqution (4) is used when EMTP enters the til zone t t t n t. strt

5 5 3.2 Wind turine struture To model the lde nd the tower of wind turine, the Constnt Prmeter (CP) line is used, whih is frequeny independent trnsmission line model. For the purpose of this pper, the CP line model n e suessfully used. The frequeny dependene of the prmeters ws lso not onsidered in [22], euse the uthors onluded tht it hs sre influene on the trnsient responses of the tower system. Besides, the sme remrk is provided in [23], where the frequeny dependene of the prmeters is gin not onsidered, sine some studies hve shown tht the skin effet hs little influene on the lightning trnsient response. The CP line is distriuted prmeter model. The si equtions of the single phse distriuted prmeter line re: dv x, t di x, t R' Ix, t L' (5) dx dt di x, t dv x, t G' V x, t C' (6) dx dt The CP line prmeters re lulted t given frequeny, whih is etter to tke it ove 1MHz [19,2], nd tht is why it is leled s frequeny independent. The CP line prmeters were lulted tking into ount tehnil informtion from the mnufturer, suh s, mteril hrteristis nd dimensions of omponents. 3.3 Ground eletrode Grounding systems re very importnt for wind turines [24,25]. Preise modeling of the dynmi performne of grounding eletrodes under lightning urrents must inlude oth the time-dependent nonliner soil ioniztion nd the frequeny-dependent phenomen [26]. These phenomen might hve mutully opposing effets sine the soil ioniztion effetively improves the grounding performne, while frequeny-dependent indutive ehvior impirs it. In the se of lightning, the urrent tht is injeted in the grounding eletrodes is fst-vrying urrent pulse with high pek vlues. The dynmi response of the grounding eletrodes sujeted to suh urrent pulses is minly influened y: (i) The soil ioniztion in the immedite proximity of the grounding eletrode, whih is relted to the urrent pulse intensity; (ii) The lightning pulse propgtion long the grounding eletrode, whih is relted to the urrent pulse front time.

6 6 The ground eletrode model used in this pper is very often used with lightning simultion purposes for HV trnsmission lines nd towers. It onsiders nonliner resistne using ontrolled resistne nd dmittne. The presene of the urrent soure provides n option for reting pieewise liner resistne funtion. Any segment k of suh funtion n e represented y the Norton iruit equivlent: i k v I (7) k k k The k is tully the differentil t the operting point k: k i k (8) vk When using the sme ground eletrode for sfety nd servie purposes, the Portuguese regultion requires mximum vlue for erth resistne of 1. This vlue is ssumed in the sene of lightning urrent flowing through it. 3.4 Surge rrester The si rrester model eqution is given y (9), where i is the rrester urrent nd rrester voltge [27]: k v v is the i (9) For SiC (Silion Cride) rresters the vlue of is etween 2 to 6. For MO (Metl Oxide) rresters the vlue is 1 6. The k prmeter is onstnt used in fitting the rrester hrteristi. 4. Cse study In this se study, two interonneted wind turines re onsidered. The eletril sheme is shown in Fig. 4. "See Fig. 4 t the end of the mnusript". The EMTP-RV iruit in Fig. 5 represents two interonneted wind turines. In this se, lightning strikes the ground ner one wind turine. For simpliity, the HV le is represented y n eletril model with onentrted prmeters. "See Fig. 5 t the end of the mnusript".

7 7 No SPD is onneted either in the LV or HV side. The purpose is to study the rel influene of CG strike ner the first tower on the seond one. With pek vlue equl to 1 ka for the lightning urrent the seond wind tower does not suffer dngerous overvoltges. Results n e seen in Fig. 6. Even in presene of pek vlue equl to 2 ka for the lightning urrent, the mximum vlue onsidered in IEC stndrds for projet, the seond wind turine does not suffer dngerous overvoltges. Results n e seen in Fig. 7. The overvoltges t the first wind turine re onsiderle, s shown in Fig. 8, thus SPD should e instlled in order to void dmges on the equipment. "See Fig. 6 t the end of the mnusript". "See Fig. 7 t the end of the mnusript". "See Fig. 8 t the end of the mnusript". The eletril sheme of Fig. 8 represents gin two interonneted wind turines, ut in this se lightning strikes diretly the lde of one wind turine. The pek vlue of the lightning urrent is ssumed to e 1 ka. In these onditions the simultions show tht the seond wind turine does not suffer dngerous overvoltges. Results n e seen in Fig. 9. "See Fig. 8 t the end of the mnusript". "See Fig. 9 t the end of the mnusript". Even in presene of pek vlue equl to 2 ka for the lightning urrent, the seond wind turine does not suffer dngerous overvoltges. Results n e seen in Fig. 1. Nevertheless, SPD must e instlled to provide effetive protetion ginst dngerous overvoltges t the stroked wind turine. "See Fig. 1 t the end of the mnusript". 5. Conlusions This pper presents new se study with two interonneted wind turines, onsidering diret lightning stroke to the lde or onsidering tht lightning strikes the soil ner tower. The most reent interntionl stndrds hve een used in this work. Comprehensive omputer simultions re otined y using the most reent EMTP version: EMTP-RV. Referene vlues of interntionl stndrds hve een dpted to Portuguese relity. Nevertheless, results re lso true for other ountries. The results hve show tht the seond wind turine does not suffer dngerous overvoltges, even when onsidering pek vlue equl to 2 ka for the lightning urrent. To redue the overvoltges to n eptle vlue t the

8 8 stroked wind turine, SPD should lso e instlled, either in ommon or differentil mode. The omputer simultions provided hve proven to e very helpful on finding whih re the most dequte protetion mesures, nd where they must e loted. Aknowledgements The uthors would like to thnk Prof. A. Mhdo e Mour for his vlule omments. Referenes [1] Kldellis JK, Zfirkis D. The wind energy (r)evolution: A short review of long history. Renew. Energy 211; 36: [2] Conroy N, Dene JP, Gllhóir BPO. Wind turine vilility: Should it e time or energy sed? A se study in Irelnd. Renew. Energy 211; 36: [3] Ekmn CK. On the synergy etween lrge eletri vehile fleet nd high wind penetrtion An nlysis of the Dnish se. Renew. Energy 211; 36: [4] Melíio R, Mendes VMF, Ctlão JPS. Power onverter topologies for wind energy onversion systems: Integrted modeling, ontrol strtegy nd performne simultion. Renew. Energy 21; 35: [5] Ctlão JPS, Pousinho HMI, Mendes VMF. Short-term wind power foresting in Portugl y neurl networks nd wvelet trnsform. Renew. Energy 211; 36: [6] Rodrigues RB, Mendes VMF, Ctlão JPS. Protetion of wind energy systems ginst the indiret effets of lightning. Renew. Energy 211; 36: [7] Rhidi F, Ruinstein M, Montnyà J, Bermúdez J-L, Sol RR, Solà G, et l. A review of urrent issues in lightning protetion of new-genertion wind-turine ldes. IEEE Trns Ind Eletron 28; 55: [8] Glushkow B. Effetive lightning protetion for wind turine genertors. IEEE Trns Energy Convers 27; 22: [9] sud, Uno N, Koyshi H, Funshi T. Surge nlysis on wind frm when winter lightning strikes. IEEE Trns Energy Convers 28; 23: [1] Srjev P, Srjev I, Goi R. Trnsient EMF indued in LV les due to wind turine diret lightning strike. Eletr Power Syst Res 21; 8: [11] mmoto K, ngw S, muki K, Sekiok S, okoym S. Anlytil surveys of trnsient nd frequeny-dependent grounding hrteristis of wind turine genertor system on the sis of field tests. IEEE Trns Power Deliv 21; 2: [12] Rodrigues RB, Mendes VMF, Ctlão JPS. Estimtion of lightning vulnerility points on wind power plnts using the rolling sphere method. J Eletrost 29; 67: [13] Rodrigues RB, Mendes VMF, Ctlão JPS. Lightning dt oserved with lightning lotion system in Portugl. IEEE Trns Power Deliv 21; 25: [14] Wind Turine Genertor Systems Prt 24: Lightning Protetion, IEC TR , 22. [15] sud, Hr T, Funshi T. Anlysis of lightning surge propgtion in wind frm. Eletr Eng Jpn 28; 162: 3 8.

9 9 [16] Npolitno F, Polone M, Borghetti A, Nui CA, Cristofolini A, Mzzetti C, et l. Models of wind-turine min-shft erings for the development of speifi lightning protetion systems. IEEE Trns Eletromgn Compt 211; 53: [17] Protetion Aginst Lightning Prt 2: Risk Mngement, IEC , 26. [18] Pintini A, Jniszewski JM, Borghetti A, Nui CA, Polone M. A sle model for the study of the LEMP response of omplex power distriution networks. IEEE Trns Power Deliv 27; 22: [19] mmoto K, Nod T, okoym S, Ametni A. An experimentl study of lightning overvoltges in wind turine genertion systems using redued-size model. Eletr Eng Jpn 27; 158: [2] mmoto K, Nod T, okoym S, Ametni A. Experimentl nd nlytil studies of lightning overvoltges in wind turine genertor systems. Eletr Power Syst Res 29; 79: [21] Mhseredjin J, Dennetiere S, Due L, Khodkhhin B, Gerin-Ljoie L. On new pproh for the simultion of trnsients in power systems. Eletr Power Syst Res 27; 77: [22] Wng XH, Zhng XQ, ng DS. An effiient lgorithm of trnsient responses on wind turine towers struk y lightning. Compel-Int J Comp Mth Eletr Eletron Eng 29; 28: [23] Wng XH, Zhng XQ. Clultion of eletromgneti indution inside wind turine tower struk y lightning. Wind Energy 21; 13: [24] Ukr O, Zmor I. Wind frm grounding system design for trnsient urrents. Renew. Energy 211; 36:24 1. [25] Cvk D, Poljk D, Dori V, Goi R. Trnsient nlysis of grounding systems for wind turines. Renew. Energy 212; 43: [26] Grev L. Time- nd frequeny-dependent lightning surge hrteristis of grounding eletrodes. IEEE Trns Power Deliv 29; 24: [27] Christodoulou CA, Ekonomou L, Mitropoulou AD, Vit A, Stthopulos IA. Surge rresters' iruit models review nd their pplition to Helleni 15 kv trnsmission line. Simul. Model. Prt. Theory 21; 18:

10 1 Figure ptions Fig. 1. 3D model of the wind turine. Fig. 2. Grid onnetion monitoring on the wind turine (Eneron).

11 11 Fig. 3. LV/HV susttion inside the tower. Fig. 4. Eletril sheme with two wind turines.

12 12 Lightning strike Surfe 41 m3 A?i Blde Iigre2 1kA/1us 75 Tower Synhronous mhine.975kv SM1 2MVA m2 SM C1.1nF C4 C3 Cpitive oupling VM.1nF.1nF Cle VV 1G35 (35 m) R3 22m L3 4uH Auxiliry trnsformer D_ /.566 Power trnsformer D_ /28 m4 VM VM m5 VM m7 Rn1 VM m9 VM m6 Rn3 Rn4 Non liner lod VM m1 LXHIOV 1x3x95 (35 m) Underground f(u) 1 Fm1 i I Rn2 I?i >i 1 Ground eletrode R2 134m 38uH L2 Surfe 41 Blde 75 Tower Synhronous mhine.975kv SM2 2MVA m1 SM C5.1nF C2 C6 Coitive oupling VM.1nF.1nF Cle VV 1G35 (35 m) R1 22m L1 4uH Auxiliry trnsformer D_ /.566 Power trnsformer D_ /28 m12 VM VM m11 VM m14 Rn5 VM m15 VM m13 Rn7 Rn8 Non liner lod m16 VM Underground f(u) 1 Fm2 i I Rn6 I?i >i 1 Ground eletrode Fig. 5. EMTP-RV iruit model for indiret lightning strike.

13 13 Fig. 6. Overvoltges t the: ) HV side of first wind turine; ) ontrol system of first wind turine; ) HV side of seond wind turine.

14 14 Fig. 7. Overvoltges with I =2 ka t: ) HV side of first wind turine; ) ontrol system of first wind turine; ) HV side of seond wind turine.

15 15 Lightning strike Surfe 41 m3 A?i Blde Iigre2 2kA/1us 75 Tower Synhronous mhine.975kv SM1 2MVA m2 SM C1.1nF C4 C3 Cpitive oupling VM.1nF.1nF Cle VV 1G35 (35 m) R3 22m L3 4uH Auxiliry trnsformer D_ /.566 Power trnsformer D_ /28 m4 VM VM m5 VM m7 Rn1 VM m9 VM m6 Rn3 Rn4 Non liner lod VM m1 LXHIOV 1x3x95 (35 m) Underground f(u) 1 Fm1 i I Rn2 I?i >i 1 Ground eletrode R2 134m 38uH L2 Surfe 41 Blde 75 Tower Synhronous mhine.975kv SM2 2MVA m1 SM C5.1nF C2 C6 Coitive oupling VM.1nF.1nF Cle VV 1G35 (35 m) R1 22m L1 4uH Auxiliry trnsformer D_ /.566 Power trnsformer D_ /28 m12 VM VM m11 VM m14 Rn5 VM m15 VM m13 Rn7 Rn8 Non liner lod m16 VM Underground f(u) 1 Fm2 i I Rn6 I?i >i 1 Ground eletrode Fig. 8. EMTP-RV iruit model for diret lightning strike.

16 16 Fig. 9. Overvoltges t the: ) HV side of first wind turine; ) ontrol system of first wind turine; ) HV side of seond wind turine.

17 17 Fig. 1. Overvoltges with I =2 ka t: ) HV side of first wind turine; ) ontrol system of first wind turine; ) HV side of seond wind turine.