Performance Analysis of Power Quality Impact of Adama-One Wind Farm in Ethiopia

Transcription

1 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC) erfrmace Aalysis f wer Quality mpact f Adama-Oe Wid Farm i Ethipia GaesaRamu a,b, Abraham Alem Kebede a, afera Meke a ad HekAyele a a NCHE, Kumaracilhuckalay, amil Nadu, dia, b J- Jimma Uiversity, Jimma Ethipia, abrahamalem6@gmail.cm. dr.gaesh.ass@gmail.cm, mtefee@gmail.cm Abstract Due t the itermittet ature f wid, the pwer quality f the grid with wid pwer plats is affected. Hece, i rder t assure the pwer quality f Adama-Oe wid farm, the ctiuus perfrmace assessmet is recmmeded usig varius perfrmace idices. w aspects f the wid farm perfrmace evaluatis are assessed. he first aspect is the evaluati f pwer ad eergy prducti perfrmace idices. Frm prducti aalysis aspect, the wid farm delivers average pwer f 8.43 MW t the grid with maximum f 5.9 MW ad miimum f.8 MW. he eergy delivered ver e year i 5/6 G.C has bee GWH agaist the desig yearly harvest f 6.7 GWH per year. Hece, the Capacity Factr result f aual eergy prducti is fud t be 35.3 %. hese demstrate that based the curret status, the wid farm perfrmace is gd ad withi the desig rage. he secd aspect is aalysis f harmic emissi frm the wid farm as the result f frequecy cverters ad ther liear lads. he harmic curret data s are cllected at e f the pit f cmm cuplig (CC) which is at 33 K bus bar systems, where 3 rd ad 5 th curret iecti harmic filters are istalled. Usig Matlab sftware, the steady state harmic lad flw aalysis f the wid farm at 33K bus-bar system is perfrmed. t has bee fud that the results f mathematically aalyzed tal Harmic Distrti (HD) curret ad vltage values are almst similar t that f simulated HD utput f curret ad vltage.he wid farm harmic curret emissi with maximum calculated value f 5.96 % is fud t be withi permissible limit set by iteratial stadard at selected CC which is 7%. he maximum calculated HD vltage is als fud t be.75 % which is less tha 5 % set by EEE SD-59. Hece, pwer quality f the wid farm ca be said t be gd ad d t have sigificat egative impact the pwer quality f grid system at preset. Fially, the grid cde stadard is prpsed. Keywrds: Harmic Filters, EEE SD-59, erfrmace dices, MSG, it f Cmm Cuplig, wer Quality, tal Harmic Distrti, Wid urbie.. NRODUCON Nw a day, wid pwer plats are becmig dmiat i servig as surce f eergy. his is because f the advacemet ad better uderstadig f the techlgy, eergy security, geerati mix, ad aim t decrease the greehuse gases r glbal warmig. he cetral gegraphical psiti f the wid farm is 39 3' 48"E latitude,8 3'4"N lgitude with (4-6)m wide ad 5km lg ad the farm is 95 km far frm Addis Ababa, capital city f Ethipia.he istalled capacity f Adama-Oe Wid farm is 5MW with 34 uits each havig a capacity f 5kW. he basis f the Gld Wid.5MW wid turbie is its permaet maget (M) geeratr, which is gearless ad directly drive by a 3 blade rtr. he cverter system cmbied with the MDD (ermaet Maget Direct Drive) sychrus geeratr guaratees superir grid cecti capabilities. But the cverter-iverter system used i wid farms prduces harmic emissis; hece it may result a pwer quality prblems withi the wid farm ad the grid cected t it. At the geerati substati, the wid farm is cected t the grid frm this substati, - 3 k trasmissi lie is liked t the Adama-ld grid. - he rest is cected t Lad Dispatch Ceter (LDC). GRD CONNECED WND OWER LAN rder t fulfill the pwer demad eeded by csumers, cutries are applyig varius types f reewable eergy surces i additi t the cvetial surces. Amg these reewable surces, wid eergy is recetly becmig dmiat. But due t the itermittet ature f wid, the presece f frequecy cverters ad liear lads, Harmics emissi is resulted. his causes the pwer quality prblem which is beig bserved i differet cutries acrss the wrld. Wid farms have differet impacts ad fuctis the perfrmace f the grid tha cvetial pwer plats because f variati f wid speed i time. Dubly fed ad Squirrel cage iducti geeratrs are widely used i wid eergy cversi systems. hese geeratrs are usually gridcupled via pwer electric cverters i rder t ctrl the vltage, frequecy ad pwer flw durig the variati fwid speed. As a csequece, wid turbies affect the dyamic behavir f the pwer system i a way that might be differet frm hydraulic r steam turbies []. Harmics arise wheever -siusidal currets ad/r vltages are geerated i the pwer system. hese are geerally referred as Harmic Distrti. he basic cditis that give rise t harmic-related prblems i pwer systems are N-liear lads, hase imbalace, High iput vltage r curret ad Resace []. mst Swedish distributi etwrks, the prblems related t harmics have bee util w ad mst fte, it is t harmful. he harmics levels have thus bee acceptable. Hwever, studies de i, fr example, USA, Japa ad Frace shw that the harmic levels have icreased. he reas fr the icremet f harmic level is the itesive use f pwer electric devices which results high harmics i distributi etwrks. he icrease i harmics level has /6/$3. 6 EEE 83

2 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC) specially bee ticed i Japa where the prblems related t harmic levels als icreased [3]. GENERAOR SDE BREAKER MDD Geeratr ASSE RECFER AC DC DC LNK + GRD SDE NERER (GB) DC AC GRD SDE BREAKER GRD SDE FUSES Uit RANSFORMER *3 phase MSG SE U CONEROR - 6/33 K Nacelle COMENSANG CAACOR CHOER HGH OLAGE ROECON (LR) NSDE OWER LC FLER OWER SULY SYSEM OUSDE OWER Fig.. Gld Wid.5 MW Electrical Diagram [4] he figure abve applies six phase Rectifier &frequecy cverter system fr the sake f trasferrig the pwer prduced efficietly ad with gd pwer quality. he rectifier efficiecy imprvemet uder six phase is evaluated usig the DC-lik utput. A. Bridge Rectifier hedclik vltagefrsix pulseisgive by 9 dωt ab dc = = m[si(ωt)-si(ωt- )]dωt () π π = 3 m= 3 where, m= π π =.35LL where, LL = 3 Fr six phase system, the vltage is give by, hedclik vltagefr twelvepulseisgive by 75 dωt ab dc = = m[si(ωt)-si(ωt-6 )]dωt () π π 45 =.4 =.398 m LL Frm the abve tw results, cmparis f the dc-lik vltage ca be see that the six phase system is mre efficiet tha three phase system. B. Frequecy Cverter he cecti f the wid farm t the public grid is de by a frequecy cverter system ad a trasfrmer. he frequecy cverter has bee specially desiged fr the use tgether with sychrus geeratrs. t allws a cmplete separati f the geeratr perati frm the grid system. S, variable speed perati f geeratr i a speed rage f 9 t 7.3 rpm is pssible. he mai circuit diagram f the cverter system is as fllws. Fig.. Six phase cverter iverter system f AWF [4] he cverter device is desiged specially accrdig t the feature f permaet maget sychrus geeratr. t has a excellet flexibility with the six phase MSG. he iductrs placed as wig structure used t prduce the fial three phase utput additially t that f reducig the harmics effect. he direct drive type ca greatly reduce the ise f system peratig ad raise reliability. he applicable frequecy scpe f GW5 KW set is 47.5 Hz t 5.5 Hz. the state f pwer grid shrt circuit, there are ly.5 t.5 times rated trque. t is 7 t 9 times much lwer tha that f M ducti Mtr (M) r Duble Fed ducti Geeratr (DFG).. MEHODOLOGY& ANALYSS Fr the aalysis f the wid farm curret perfrmace, differet perfrmace idices are csidered. Amg this, pwer cefficiet with respect t tip speed rati is checked at its rated wid speed. A. wer Cefficiet he Cp i terms f λ is give as fllws ( ) * ( ) Cp (.48)*(.4).5 5% Where Cp is pwer cefficiet, λ is ip speed rati & γ is Grud surface cefficiet. Usig the abve value, Matlab simulati utput f pitch ctrlled wid turbie pwer cefficiet versus tip speed rati curve at rated wid speed f m/s is give belw. (3) Figure 3. Cps λ utput at differet pitch agle /6/$3. 6 EEE 84

3 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC) Amg all curves, the desired e is the pit where pitch agle is fud t be zer because at this agle value f the required pwer ca be prduced. Usig the calculated values ad the datas give frm the maufacturer, available pwer ca be determied. Give the fllwig data: Blade legth, l= r= 38.5 m, Wid speed, = m/sec Air desity, =.97 kg/m3, wer Cefficiet, Cp=.5 sertig the value fr blade legth as the radius, l= r= 38.5 m A = πr, where A is the swept area = π*(38.5m) =4654m Fially the pwer cverted frm the wid by a turbie will 3 be, avail = ρa C p(λ,β) (4) 3 3 avail= *.97kg/m *4654m *(m/s) *.5 avail =.5MW he pwer curve aalysis f a turbie system is assessed usig the fllwig diagram. Fig. 4. Cmparis betwee the referece ad measured pwer curve. Frm Fig. 4, the measured pwer curve shws almst similar characteristics with that f the referece curve that prvides the maximum amut f pwer at rated wid speed value. B. ermaet Maget Sychrus Geeratr (MSG) Characteristic Equatis he geeratr system has tw sets f three-phase widigs the statr side, which are shifted by 3 electrical degrees with each ther. he vltage equatis fr the six physical statr widigs are shw belw [9] =R s si s+ψ' s (5) Where, s statr vltage, R s statr resistace, i s statr curret ad ψs is flux leakage. =[ s a b c x y ] z, i=[i s a ib ic ix iy i], z R=r s 6*6 ψ =[ψ ψ ψ ψ ψ ψ ]. s a b c x y z he resultig vltage equati i d-q axis is: =Ri+ψ' (6) he Equivalet circuit f MSG based the wid eergy cversi system is shw belw. Fig. 5. Equivalet circuit f MSG i d-q referece frame Frm Fig. 5, the vltage equati ca be expaded as: d R Lq i= d v- d i+ d ωri q (7) dt Ld Ld Ld d R Ld λpωr i= q v- q i+ q ωri- d (8) dt L L L L q q q q Where, L d = d axis iductace R = resistace f the statr widig i q = q axis curret, i d = d axis curret, q = q axis vltage, ω = Agular velcity f rtr, d = d axis vltage, r λ= flux iduced, umber f ple pairs. C. Eergy rducti Assessmet f AWF Mthly eergy prducti data are cllected fr a year ad the capacity factr is calculated t check the curret capacity f AWF. A capacity factr implies that the system ru at full capacity the etire year. he capacity factr fr a large wid farm rages frm % t 4%, the latter figure beig clse t the techlgy ptetial. Aualeergy prducti (MWh) CF= (9) stalledcapacity*ttalhuria year D. wer Quality Assessmet f the Farm he fllwig prcedure has bee used t aalyze the HD level f the wid farm: Step : Chse the pit f cmm cuplig. Step : detify the date where filters are cected t the system. Step 3: Cllect harmic curret data frm filters utput. Step 4: Calculate HD f curret ad vltage at selected CC. Step 5: erify pwer quality status f AWF by cmparig Calculated HD f vltage ad curret with stadard. E. Mathematical Frmulati f Harmics aalyze wave frms f vltage ad curret, the cmmly used tl is Furier series. Furier series basics are described usig the fllwig equatis /6/$3. 6 EEE 85

4 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC) f(t)= a + (a csωt+b siωt) () = Where, π ω= a = f(t)dt a = f(t)cs(ωt)dt b = f(t)si(ωt)dt Where is a whle umber he abve aalysis ca als be expressed as fllws: f(t)= a + Csi (ωt+φ ) () = where, C = a +b b φ =arcta a S, a distrted vltage (t) f perid ca therefre be expressed i the fllwig maer, (t)= + si (ωt+ ) () = π where ω= :Amplitudef the DCcmpet :heiitialphasef,(t=) Similarly, a distrted curret i (t) f perid ca be expressed as: i(t)= + si (ωt+φ ) (3) = where :Amplitudef thedccmpet φ :heiitialphasef,(t=) RMS frmula f harmic vltage ad curret: Related with the abve basic equatis, the RMS value f the sigal (t) is defied as: rms= (t)dt (4) arseval's therem tells us that: = (t)dt= + (5) his gives the fllwig relatiship f vltage ad curret RMS values: 3 4 = RMS = = (6) Similarly, 3 4 = RMS = = (7) Csiderig that DC cmpets, ad =. tal Harmic Distrti (HD): t is the measure f pwer quality f the wid farm by aalyzig the -siusidal wave frms f vltage ad curret. Assumig DC cmpet i the utput, HD ca be determied as fllws (, rms) HD = = (8) (, rms) HD = = (9) he fudametal curret ( fud ) which is used fr ttal harmic curret distrti estimati has bee selected usig the equati shw belw [4]. k actual / 3 fud = () Xfud Where, K is the k factr f the step up trasfrmer i the substati (CC). actual is the actual vltage measured at selected bus bar (CC) [].X fud is the per phase fudametal reactace [ ]. After cmputig the curret ad vltage HD frm the cllected harmic currets, EEE stadard harmic curret limit is selected usig the fllwig frmula t kw that the estimated values are withi the limit r t. shrtcircuit MA SCR= = () lad MW sc L Where, SC is the maximum shrt circuit curret at the CC. L is the maximum demad lad curret at CC. Shrt circuit curret calculati: Assumig S = MA, Select shrt circuit pit, that is 33k shrt circuit pit; akig shrt circuit curret frm Nazareth substati R = KA, Shrt circuit capacity, MA sc 3*U *R 3*3* 86.4MA () Shrt circuit reactace uit value, S Xx.437 SMA 86.4 Mai trasfrmer reactace uit value: U% S Z X *.5*.9 S 55. Reactace uit value calculati f 34 WGs: X=X X =.337 x. Csiderig ifiite bus system ' z = 4.79 X Referece curret: S MA 3*U 3*33.75KA 4. Shrt circuit curret frm ifiite bus system: ' z z * 4.79*.75KA 7.49KA (3) Shrt circuit curret frm 34 WGs. Reactace uit value f ttal 34 WGs: X.5. Effective reactace f 34 WGs: S 5/.95 X s X*.5*.74 S ' 3. he, z Referece curret S 5/.95.94kA 3*U 3*33 he, ' * 4.6* ka z z /6/$3. 6 EEE 86

5 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC) Shrt circuit curret: z ka Maximum shrt circuit curret, csiderig circuit breaker sizig factr is cmputed as: SC= *K ch* z= *.9*.84=3.5kA (4) Where K ch is sizig factr f circuit breaker [5]. Lad curret calculati: Lad MW 5MW L= = (5) Lad 33k L =.54 ka. he lad curret ( L ) is cmputed by takig the rati f maximum Lad pwer i MW ad the vltage at 33 k bus bar systems. Shrt circuit rati is determied frm sc ad L ad the the limit fr curret ad vltage are fud. F. Harmic wer Lss Evaluati f the Farm wer lss f Adama-Oe wid farm due t the harmics emissi effect is assessed at a CC f 33 K, A bus bar system. he pwer lss calculati is de usig harmic vltage, curret ad true pwer factr. lss= H* H*pf (6) Evaluati f Harmic Filters ad heir mpact: he impact f 3 rd ad 5 th harmic filters istalled i AWF is evaluated based their ctributi f pwer factr imprvemet f the wid farm. he active ad reactive pwer datas are cllected fr a sample f e mth. calculate the pwer factr, first apparet pwer (S) is calculated frm cllected pwer datas usig equati shw belw. S= +Q (7) Ad, csφ= S Where S apparet pwer ad csφ is pwer factr. Fr estimati f the pwer factr, the maximum values f active ad reactive pwer are used t fid the pwer factr value at wrst case.. RESUL AND ANALYSS A. Eergy rducti Aalysis f Adama-Oe Wid Farm (AWF) he Fig. 6 belw summarizes the aual eergy prducti f AWF based the cllected data frm Data Lgger ad SCADA system. ANNUAL ENERGY RODUCON (MWH) 5,.,. 5,.,.,84.5, ,.6, , ,358. 6,89.8,5.7 8, ,473. 8,737. 4,.,95.9 As per the abve prducti aalysis, there is 3% differece betwee the curretly calculated aual eergy prducti f 57,739.93GWhad that f the referece value f firm eergy prducti f 6.7GWh per year which was held durig the ctract agreemet with Ethipia Electric wer Crprati (EEC). S, it is fud that the farm is prvidig the desired pwer. Capacity Factr (CF) f AWF: he Capacity Factr (CF) f AWF based the abve summarized data ca be estimated as fllws. 57,739.93(MWh) CF = 5MW*876 h =.353, CF = 35.3% Based the abve value f CF, it ca be ccluded that the wid farm is peratig well sice the value fulfills the iteratial stadard limit which is betwee t 4 %. But the maximum CF value f the farm set durig feasibility study was 38%. Hece, ly a differece f.7 % is fud. Capacity Factr versus Average Lad: he wid farm prducti ctributi t the grid system is aalyzed by usig the relatiship betwee mthly capacity factr ad average lad. he farm average lad data is cllected frm three turbie grups ad capacity factr is calculated fr each mth frm the respective eergy prducti f the wid farm Capacity Factr s Average Lad Capacity factr (%) Average lad (MW) Fig. 7. Capacity Factr vs. Average Lad f AWF Frm Fig.7 abve, it ca be see that the wid farm capacity is high which ca hadle the respective lad (MW) effectively, s it ca be said that the farm ctributes its part fr avidig the eergy shrtage curretly. B. wer quality evaluati f the wid farm Simulati utput f vltage ad curret at CC: he steady state utput f vltage ad curret HD values are aalyzed usig FF aalysis frm Matlab ad detailed mdel f AWF is shw belw. Aual eergy prducti (MWh) Fig. 6. Result summary f AWF Aual eergy prducti /6/$3. 6 EEE 87

6 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC).4 Selected sigal: cycles. FF widw (i red): cycles ime (s) Fudametal (5Hz) =.38, HD=.3% Mag (% f Fudametal) Fig. 8. Simulik Blck diagram f AWF Usig Fig.8 abve, the simulati is de at the selected CC f 33 K bus bar system. he simulati result f curret ad vltage HDs are havig similar values with the mathematically cmputed HD values f the actually cllected harmic curret datas. hree phases wavefrm utput f curret ad vltage i per uit at 33K bus bar system is shw belw Frequecy (Hz) Fig.. FF utput f ttal harmic vltage distrti C. Summary f ttal harmic curret distrti After aalysis f tw mths harmic curret data, the result is summarized as fllws. % Harmic Curret Distrti 5% % Date Mi HDi (%) Max HDi (%) Fig.. Summary f curret HD at 33 K bus bar system D. Summary f ttal harmic vltage distrti Fig. 9. ad three phase wave frm utput at 33 K busbar FF aalysis f Curret HD: Selected sigal: cycles. FF widw (i red): cycles ime (s) After aalysis f tw mths harmic vltage data, the result is summarized as fllws. he harmic vltage distrti is cmputed frm harmic curret ad harmic pwer filters ut put with the crrespdig pwer factr values. % 8% Harmic ltage Distrti Mag (% f Fudametal) Fudametal (5Hz) =.78, HD= 4.95% Frequecy (Hz) Fig.. FF utput f ttal harmic curret distrti 6% 4% % % Date Mi HDv (%) Max HDv (%) FF aalysis f ltage HD: Fig. 3. Summary f curret HD at 33 K bus bar system /6/$3. 6 EEE 88

7 6 teratial Cferece Ctrl, strumetati, Cmmuicati ad Cmputatial echlgies (CCCC) Frm the tw graphs, the result summary f harmic vltage ad currets are withi permissible limits as cmpared t EEE stadard values. Ad therefre, it ca be said that the wid farm pwer quality is gd ad did t affect the grid system pwer quality. E. Harmic filters ad their impact Usig maximum active () ad reactive pwer (Q) datas frm SCADA system, the pwer factr f the farm has bee aalyzed i rder t assess the impact f filters i the wid farm. [] J.Arrilaga, D.A.Bradley ad et al. wer System Harmics, Jh Willey & Ss, 985. [3].C. Shuter, H. llkmmer ad et al. survey f harmic levels the America electric pwer distributi system, EEE rasactis pwer delivery, vl. 4, pp. 4-3, Octber 989. [4] GldWid sciece ad techlgy C.LD, Maual, Gldwid Uiversity, 9. [5] Gld Wid techical ffer, Hydr Chia ad CGCOC it veture, Nvember, 9. [6] A. Ametai, harmic reducti i thyristr cverters by harmic curret iecti, EEE trasacti. wer App system, vl. AS-95,., pp.44-45, Mar.976. [7]. Ackerma, Wid wer i wer Systems, Jh Wiley & Ss, Ltd, 5. [8] wer Quality issues stadards ad guide lies, EEE, l-3, May996. Fig. 4. Harmic Filters impact pwer factr imprvemet t is fud that there is sigificat differece bserved whe harmic filters are cected ad discected.. CONCLUSON Based the cllected data frm data lggers ad SCADA (Supervisry ctrl ad data acquisiti) system f the plat, the curret perfrmace status ad its pwer quality impact f Adama-Oe Wid Farm is aalyzed. he results btaied frm the assessmet f this wid farm ca be used as a iput fr the ther wid farms t be cected with grid system i the future. he eergy delivered ver e year i 5/6 has bee GWH agaist the desig yearly harvest f 6.7 GWH per year. he harmic data at stadard CCis cllected ad aalyzed fr its curret HD level ad fud t be 5.96 % ad less, agaist the EEE stadard level f 7 % fr the case f selected CC. Hece, cmparig the abve results with EEE stadards, it is deduced that curretly the wid farm perfrmace is gd ad has sigificat egative impact grid system pwer quality. ACKNOWLEDGMEN First f all, we wuld like t pass all hr ad glry t the almighty Gd frm the begiig t ed. eed t pass my deep gratitude fr Jimma stitute f echlgy fr prvidig us this pprtuity t wrk the research. We als thak Mr. Gebeyehu Belay fr his guidace ad techical supprt. Fially, we wuld like t thak ur clleagues fr all supprt that they have prvided. REFERENCES [] H.lider, F. ader il ad et al. Cmparis f Direct-Drive ad Geared Geeratr Ccepts fr Wid urbies, Eergy Cversi, pp ,. Abraham Alem Kebede (986) received his First degree BEd i Electrical ad Electric echlgy i Adama Sciece ad echlgy Uiversity i ad his M.Sc. i wer System Egieerig at Bahir Dar Uiversity i 4. Nw he is wrkig as a faculty i schl f Electrical ad Cmputer Egieerig at Jimma stitute f echlgy, Jimma, Ethipia. He is wrkig as HOD i Faculty f Electrical & cmputer Egieerig Startig frm 5 util w. His field f iterest icludes Reewable Eergies, wer Quality, wer system perati ad ctrl, wer system Aalysis, Electrical machies ad Drives. Gaesa R (976) received his Bachelr, Master ad Dctrate degree i egieerig i 999, ad respectively. He has bee wrkig as rfessr i the departmet f EE, Nrul slam Uiversity, dia. resetly, he is wrkig as a Expatriate faculty i the Schl f ECE, Jimma stitue f echlgy, Jimma Uiversity, Ethipia. He published research articles i varius scpus idexed iteratial urals ad iteratial cfereces. His areas f research are Electric istrumetati, LS architecture fr etwrk algrithms ad mage cmpressi algrithms. He is a life member f SE ad EE. He was a deputy prect directr fr NUSA paylad desig ad steerig cmmittee member f NUSA which is a ivative prgram is beig develped by NU, dia. Mr. efera Meke received BEd degree i Electrical ad Electric echlgy frm Adama Sciece & echlgy Uiversity i ad his M.Sc. i wer System Egieerig at Bahir Dar Uiversity i 4. He is curretly wrkig as a lecturer i schl f Electrical ad Cmputer Egieerig at Jimma Uiversity, Ethipia. Curretly he is wrkig as Dea fr Faculty f Electrical & cmputer egieerig. His field f iterest icludes wer system dyamics & rasiet, rasmissi ad Distributi system, Reewable Resurces ad echlgy ad wer Quality. Mr. Hek Ayele received BEd degree i Electrical ad Electric echlgy ad M.Sc. i wer System Egieerig frm Adama Uiversity ad Bahir Dar Uiversity i 9 ad 4 respectively. He is curretly wrkig as a lecturer i schl f Electrical ad Cmputer Egieerig at Jimma Uiversity, Ethipia ad as pre-egieerig crdiatr i Jimma istitute f echlgy. His field f iterest icludes wer Electrics ad Electrical Drives, wer Quality, rasmissi ad Distributi system, Reewable Resurces ad echlgy /6/$3. 6 EEE 89