Analysis of the Deterioration Effects of Stator Insulation on the its Electro-Thermal Property

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1 Intnational Jounal of Elctical and Elctonics Engining 3:11 9 Analysis of th Dtioation Effcts of Stato Insulation on th its Elcto-Thmal Popty Diako Aii, Ahmad Gholami, Abolfal Vahdi Abstact Elctical machiny spcially lctic gnatos which a th main pats of any lctical ntwok, though th tim and vyday functions lik any oth lctical dvics xpinc a sis of lctical, mchanical and thmal stsss. Continuous of this tansint and stabl tnsion ov th tim, caus lasting ffcts on th machin insulation pats, spcially th insulation of stato slot which is th most impotant pat of th insulation in machins. Ths vnts includ cation of voids in th vaious lays of insulation; cation th gaps btwn lays of insulation and incasing th insulation dissipation facto du to chang in capacitanc of insulation. Thfo, in this pap w tid to analysis th impact of ths dstuctiv factos on th stato slot insulation lcto-thmal analysis using finit lmnt analysis and finally stimat th maining lif of th insulation in ths cass with gad to th ffct of th lctical and thmal stss simultanously. Kywods Dtioation, stimatd lif, gnatos, void I. INTRODUCTION HE insulating systm is on of th main pats of lctical T otay machin. High opating and liability dmands qui th pop tchnological stps to manufactu th insulating systm [1]. Much ffot has bn invstd ov sval dcads in studying th aging chaactistics of th vaious lctical insulating systm dsigns and insulating matials mployd in high-voltag quipmnts. Ths studis aim mainly to allow asonabl stimats of th svic lif xpctancis of such quipmnt and to assss thi liability in opating conditions aft a givn numb of yas in svic. Th aging of a polymic matial, o of any oth matial fo that matt, inhntly involvs th altations of th matial s physical and/o chmical stuctu which is xpctd to b latd to th changs in th physical and chmical poptis of th matial [],[3]. Whn th aging of a dilctic matial is vokd, it usually implis that th altations in th poptis of th matial a dtimntal to its svic opation and svic liability. Whn ths poptis hav dtioatd to th point wh th matial can no long Diako Aii is with th Univsity of Scinc and Tchnology, Than, Ian (cosponding autho to povid phon: ; -mail: diako_@yahoo.com). D. Ahmad Gholami was with Univsity of Scinc and Tchnology, Than, Ian. H is now with th Dpatmnt of lctical ngining, (-mail: Agholami@iust.ac.i). D. Abolfal vahdi is with th Elctical Engining Dpatmnt, Univsity of Scinc and Tchnology, Than, Ian, (-mail: Avahdi@iust.ac.i). opat safly und nomal stss conditions, it implis that it has achd th nd of its usful lif. Th causs of aging a yt to b fully undstood, but obviously, th dg of aging stongly dpnds on th natu of th involvd matial and on th natu and duation of th applid stsss. Indd, aging can b inducd by a combination of th vaious stsss (lctical, mchanical, thmal o nvionmntal) to which th insulation systm is subjctd. Th simultanous application of ths stsss lads to th intaction of aging mchanisms. Emg of som signs of wa and aging in th insulation, such as voids and thi dlaminating will acclat its dtioation. As a sult in th location of th voids, th lctic fild intnsity will incas many tims and caus patial dischag in th voids and thus will incas th void si and duc th insulation lif. Th a diffnt ways to masu th insulation lif. On of thm is th laboatoy mthod [4]. But this mthod is not usd much, bcaus of bing tim consuming. Thfo, this pap is tid to us simulation and numical analysis of data which is obtaind to stimat th maining lif of insulation using coupld Elcto-thmal analysis basd on stong mthod of finit lmnt. Analysis of th cosmtic sults of th maining lif shows that in th adjacnt Walls of th voids, th lif of th insulation is ducd svly. This issu ncssitats th nd to pai th damagd insulatos. II. CASE OF STUDY To study a sampl, it is quid to dtmin o dsign th sampl fist. Thfo, in od to do fild analysis and to study th gnato insulation Status, a gnato with a givn pofil has bn slctd. Th slctd gnato is synchonous with Rgula winding, th phas, two pols that hav 4 slots in stato. Ratd fquncy, voltag and pow a spctivly 5H, 13.8 KV and 1 MVA. III. ELECTROMAGNETIC MODELS To div th lctomagntic systm quation, w stat with th Amp s law, D D H = J + = σ E + σv B + J + (1) Ths quantitis a: Th lctic fild intnsity, E Th lctic displacmnt o lctic flux dnsity, D 697

2 Intnational Jounal of Elctical and Elctonics Engining 3:11 9 Th magntic fild intnsity, H Th magntic flux dnsity, B Th cunt dnsity, J Extnally gnatd cunt, Elctical conductivity, σ Vlocity, v Now w includ th ffct of th tim vaiant-hamonic filds and us ths dfinitions fo th potntials: B = A () A E = V (3) And combin thm with th constitutiv lationships B = μ ( H + M ) and D = ε E + P to wit th Amp s law as: 1 ( jωσ ω ε ) A + ( μ A M ) σv ( A) + ( σ + jωε ) V = J + jωp In which ω, ε, μ, M and P spctivly f to Angula fquncy, Rlativ pmittivity, Rlativ pmability, magntiation vcto and lctic polaiation vcto. In th cas of -dimnsional-plan, th a no vaiations in th -diction, so th lctic fild is paalll to th -axis. Thfo you can wit V as ΔV/L wh ΔV is th potntial diffnc ov th distanc L. Now ths quations a simplifid to:. μ A ΔV = σ + J L 1 y + M. x M + jωp σv A + ( jωσ ω ε ) A In th ax-symmtic cas, anoth fom of th gadint of Vloop th lctic potntial has bn usd, V =, bcaus th π lctic fild is only psnt in th aimuthally diction. Th abov quation, in cylindical coodinats, bcoms: u M [ ] u u 1 μ μ + 1. M u σ v ( j ) u V u u + + σ ω ω ε + σ. = Vloop σ Jϕ jωp π + + Th dpndnt vaiabl u is th nono componnt of th magntic potntial dividd by th adial coodinat, so that: (4) (5) (6) Aϕ u = (7) Th application mod pfoms this tansfomation to avoid singulaitis on th symmty axis. IV. INSULATION LIFE Ahnius modl usually has bn usd fo stimating th lif of th insulation pats whn thmal stss is applid alon, but with gad to fast dtioation in th sctions of th insulation whn placd und th both lctical and thmal tnsions, Ahnius modl must b comphnsiv [5], [6]. Thfo, Hatch and Endicott psntd th Eying modl fo taking to account th thmal and voltag stsss simultanously. But using spcial mthods fo dtmining th cofficints of th quation to stimat th lif of Eying insulation is actually a challng [7], [8]. Thus Ramu poposd [9] a modl fo th stimation of th insulation lif which us th pow law and its paamts a tmpatu dpndnt. Whn th insulation is only und thmal stss, th lif is obtaind using th following lationship: E L = Axp (8) kt E is th activation ngy and k is th Boltmann s constant. A dtaild analysis of th data which is obtaind in th psnc of thmal stss alon o whn both lctic and hat a applid shows that activation ngy applying both tnsions simultanously, is lss than th cas which on stss is applid. Taking to account this point, th modl fo Ahnius can b coctd by dcasing th activation ngy using th σξ xp facto. Nw modl is xpssd as kt follows: E σξ L = Axp (9) kt Th ξ is lctically fild (stss) applid. A. Void V. DETERIORATION EFFECTS In this sction w assumd that th scond insulation lay has a void with ctangula dimnsions,.1 mts. In Fig.1 distibution of th lctic fild with th ai void is psntd. Fig.1 shows th lins of lctic fild, Fig. compas th lctic fild distibution in two cass with and without hols in th scond lay of insulation and Fig.3 psnts th maind lif of insulation. 698

3 Intnational Jounal of Elctical and Elctonics Engining 3:11 9 fild in voids incass suddnly. Ths local incasing causs patial dischag in that location and thus incass th void si and th insulation will b damagd locally. Fig. 4 shows th distibution of th tmpatu with spct to 5 pcnt incasing in th dissipation facto. Th sults of th duction of th insulation lif in ths cass hav bn psntd in th Fig.5. B. Incasing of th dissipation facto In this sction th aging ffct has bn modld by th incasing of th dissipation facto in insulation lays and its ffcts on th fild distibution has bn spcific. H w assumd that th dissipation facto of th insulation lay is incasd 5 pcnt. Fig. 1 Distibution of th lctic fild and spctiv lins if th ai void is in th scond lay of insulation (V/m) Fig. 4 Th distibution of th tmpatu with spct to 5 pcnt incasing in th dissipation facto (ºC) Fig. Compaing th lctic fild distibution in two cass with and without hols in th scond lay of insulation Fig. 5 Th impact of 5 pcnt incasing of th dissipation facto on th insulation lif with gads to th thmal and lctical stsss Fig. 3 Effct of void in th maining lif As it is obvious fom th sults, th intnsity of th lctic As can b sn, 5 pcnt incasing of th dissipation facto incass th insulation tmpatu 3 pcnt. It should b noticd that ctain changs in th distibution of th lctic fild has not bn dtctd in two cass. 699

4 Intnational Jounal of Elctical and Elctonics Engining 3:11 9 C. Gap cation btwn th insulation lays Dfct of good assmbly and connction of appopiat insulation lays and conductos togth, maks availabl to tim, bing utilid in long-tms, th shaking and insulation xhaustion, an ai gap will b catd in th pat of th lays. Du to th low ai pmittivity cofficint in compaison to th insulation, th lctic fild intnsity will b gatly incasd in ths gions and th localid tnsions caus s tivial dischags which damag th insulation wall [1], [11]. Th spad of this dstuctiv phnomnon duing th tim can siously damag th insulation sctions. In this sction th distibution of th lctic fild is analyd again whil considing th abov mntiond phnomnon. Fig. 6 shows th Elctic fild distibution assuming ai lay cation and Fig.7 psnts th impact of dlaminating on th lif of insulation lays considing th thmal and lctical stsss. scto is locatd in th conducto spaation cuv and bcaus of th insulation dpating in this sction; th lctic fild intnsity is gatly incasd as it is shown in th figu which incass th tmpatu of th lay. This issu can caus sious damag to th insulation sction. VI. COMPARING THE RESULTS Tabl I shows diffnt impacts of th insulation aging on th distibution of lctic and thmal fild, and th insulation lif. TABLE I Effcts of th insulation dtioation on th distibution of lctic and thmal fild, and th maind lif in th dtioatd aa dtioation typ lctical fild thmal fild maining lif with void 55% incasing 1% incasing % incasing % incasing in dissipation facto laying without vaiation 18% incasing 3% incasing 3% dcasing 4% incasing 7% dcasing Dlaminating is th most impotant th intnsity of lctic fild and th tmpatu sction. This poblm has causd th gatst th duction of th insulation lif which is ducd to 7 pcnt. This issu vals th nd to us insulatos with high quality matials, mo accuat opation and assmbly, and ultimatly complt sal btwn th insulation lays. Fig. 6 Elctic fild distibution assuming ai lay cation (V/m) VII. CONCLUSION Any lctical dvic has a lif tim that with passing of this tims gadually, th nd to pai and maintnanc will b cla. Gnatos and motos which a th basic pats of lctical ntwoks a not xmptd fom this vital nd. Fo this pupos diffnt mthods hav bn usd. This pap was focusd to th analysis of filds, such as lctical and thmal filds. Ths filds caus tnsions in diffnt pats of th insulation which monito th vaious scnaios and dtmin th common quations fo th insulation lif stimation, and th lif in diffnt pats of th insulation is stimatd whil considing th aging ffct. Th sults pov that, void cation and dlaminating of th insulation will damatically dcas th maining lif of th insulato. REFERENCES Fig. 7 Impact of dlaminating on th lif of insulation lays considing th thmal and lctical stsss Sinc th catd ai lay is dictly connctd th conducto, it consists th wamst pat of th systm. Also this [1] Mntlik Vaclav, Tanka Pavl, Piha Josf, Using of th aging modls and otating machin insulation valuation, Elctical Insulation. 8, ISEI 8, Confnc Rcod of th 8 Intnational Symposium on, 9-1, Jun 8, Pags [] T. J. Lwis, Aging- A pspctiv, IEEE Elct. Insul. Mag., vol. 14, no. 4, pp. 6-16, 1. [3] V.K. Agawal, H.M. Banfod, B.S. Bnstin, E.L. Bancato, R.A. Fouac, G.C. Montanai, J.L. Papal, J.N. Sguin, D.M. Ryd and J. Tanaka, Th mystis of multifacto aging, IEEE Elct. Insul. Mag., vol. 11, no. 3,

5 Intnational Jounal of Elctical and Elctonics Engining 3:11 9 [4] Jams H. Dymond, K. W. Stangs and Nick Stangs, Th ffct of sug tsting on th voltag nduanc lif of stato coils, IEEE Tansactions Industy Applications, vol.41, no.1, Jan/Fb 5. [5] G. C. Montanai and M. Cacciai, A pobabilistic insulation lif modl fo combind thmal-lctical stsss, IEEE Tansactions on Elctical Insulation vol. EI- no.3, Jun [6] G. J. Ands, SM J. Endnyi, F G.L. Fod, M G.C. Ston, SM, A pobabilistic modl fo valuating th maining lif of lctical insulation in otating machins, leee Tansactions on Engy Convsion, vol. 5, no. 4, Dcmb 199. [7] S.B.Pandy, Estimation fo a lif modl of tansfom insulation und combind lctical & thmal stss, IEEE Tansaction on liability. vol.41, no.3, 199 Sptmb. [8] H.S.Endicott, B.D.Hatch, R.G.Sohm, Application of ying modl to capacito aging data, IEEE Tans. Componnt pats, vol 1, 1965 Ma, pp [9] T.S.Ramu, On th stimation of lif pow appaatus insulation und combind lctical and thmal stss, IEEE Tans. Elctical insulation, vol EI-, 1985 Fb, pp [1] Victo V.Kumin, Lv L.khaimovitch, Equigadint lins of lctic fild in stato slot, isodstuction lins of insulation and high voltag dsign of tubo- and hydo gnatos winding, Confnc cod of th IEEE intnational symposium on lctical insulation, Anahim, CA USA, Apil -5,. [11] Gc C.Ston, Edwad A.Boult, Ian Culbt, Hussin Dhiani, Elctical insulation fo otating machins, IEEE Pss sis on pow ngining, 4. Diako Aii was bon in H has civd B.Sc. dg in Elctical Engining fom Tabi Univsity, Tabi, Ian in 7. And h civd th Mast dg in Elctical Pow Engining fom th Univsity of Scinc and Tchnology, Than, Ian in 9. H is psntly pusuing th Ph.D. dg in Elctical Pow Engining, Ian Univsity of Scinc and Tchnology. His sach intsts a aging of insulations in lctical machins. 71