Simulation Modeling of Incipient Faults in Power Transformer

Transcription

1 Itertiol Jourl of Scietific & Egieerig eserch olume 3, Issue 5, y- ISSN Simultio odelig of Icipiet Fults i Power Trsformer il Kumr, jy thore, shish Ptr strct - This pper presets method of modelig iterl widig fults of three-phse, power trsformers to sigle-phse, distriutio trsformers. The model which is comptile with the ltertive Trsiets Progrm, TP, llows the simultio of tur-toerth d tur-to-tur fults o either widigs of sigle-phse, two-widig, distriutio trsformer. esults of stged iterl widig fults of distriutio trsformer re compred with the simultio results to vlidte the model. The experimetl results were foud to e comprle to those of the simultio. Idex Terms Iterl widig, power trsformer, distriutio trsformer, comptile, ltertive trsiets progrm (TP), simultio,. INTODUCTION T he trsformer is oe of the most expesive d importt electricl equipmet of power distriutio system d hece the loss of such equipmet through ctstrophic filure c e very costly. Deregultio i the US hs cused drstic chge i the electricity mrket. This chge hs put utilities uder stress sice electric eergy hs ecome ulk commodity trded d sold uder free mrket competitio resultig i cost cosciousess mog utilities. The mi drivig forces re to reduce mitece costs, prevet forced outges with the cosequetil costs, prevet forced outges with the cosequetil costs, d work existig equipmet hrder d loger []. utilities re therefore lookig for wys to detect developig or icipiet fults efore they ecome ctstrophic d llow for chge from periodic-to coditio-sed mitece. Differet techiques hve ee used i the re of trsformer fult detectio d digosis. The most estlished digostic d moitorig method is the lysis of dissolved gses i the trsformer[]. The method is sed o lyzig the types, cocetrtio d productio rtes of geerted gses [, 3]. The techique is well ccepted d hs the cpility to detect wide rge of filure types. Determitio of the degree of polymeriztio vlue of cellulose (used i pper isultio) is stdrd method for qutifyig the degrdtio of cellulose [4]. Other methods hve utilized the mesuremet of trsfer fuctios of the trsformer to detect deformtios of the widigs [5, 6]. Deformtio or chges i geometricl distces of the widigs leds to chges i iterl cpcitce, d therey chge i the trsfer fuctio of the trsformer. study of the records of moder trsformer rekdows which hve occurred over period of yers shows very coclusively tht etwee 7 d 8% of the umer of filures re filly trced to short-circuits etwee turs [7]. These short circuits re result of degrdtio or wer of the trsformer widig isultio (ofte clled the mior isultio) cusig djcet turs to short (tur-to-tur fult) or tur (s) shortig to y grouded prt of the trsformer (tur-to-erth fults). The purpose of the work reported here is ired t developig techique tht utilizes electricl idictors for iterl widig fult detectio d digosis. Towrds this, it is ttempted to simulte some of the widig fults of sigle-phse trsformers d vlidte the sme with experimets. model developed i [8] for three-phse power trsformers is dpted to model sigle-phse distriutio trsformers to study the effect of iterl widig fults t the termils. Simultio d field test results of stged iterl widig fults re preseted. compriso of the two results is mde to show the vlidity of the model. IJSE

2 Itertiol Jourl of Scietific & Egieerig eserch olume 3, Issue 5, y- ISSN SINGE-PHSE TNSFOE ODE Figure (l) shows the widig represettio of sigle-phse, two-widig trsformer i figure (l ). I. I. + + N N - - Figure. Two widig trsformer I I I m m m E E N N Figure. Equivlet circuit of two-widig trsformer I figure iduced voltges, widig resistces,, i ' s re termil voltges, E i' s the I i ' s the widig currets, i ' s the i ' s the widig iductces d N i ' s the umer of widig. Suscript i refers to the primry widig, the secodry widig d m the mgetizig rch. The resistce d iductce of the two-widig trsformer re represeted i TP y the mtrices [] d [] s show i equtio (). = ij is the mutul iductce etwee widigs i d j. BCTN, supportig routie of TP [9] is used to derive lier [] - [] represettio for the sigle-phse, two widig trsformers usig dt of oth the ope-circuit d short-circuit tests t rted frequecy. Stry cpcitces re igored i this represettio d hece the model is oly vlid for up to few khz. The derived [] - the form show i (). re of To model iterl fults, the [], [] mtrices re revised where some of their elemets re computed y BCTN for trsformer without fults i the widig, d the other elemets computed from mthemticl equtios modelig fults i the widig.. Tur-to-erth fult tur-to-erth fult o the primry widig divides the primry widig ito su-coils s show i fig.. I.. I + +, i N, i - - Fig.. Sigle-phse trsformer with tur-to-erth fult [] = o primry [ ] [] is determied usig the reltios :...() ;...(3) N N is determied from BCTN d the remiig elemets i the mtrix, [], re computed from mthemticl reltios of the fulted coil. Determitio of,, d = is sed o the rules of cosistecy, lekge d proportiolity. Derivtio d use of equtios sed o these rules c e foud i [8]. Usig the rules of proportiolity d lekge, we hve ; k k k ; k IJSE

3 Itertiol Jourl of Scietific & Egieerig eserch olume 3, Issue 5, y- 3 ISSN (4) k k Where k =. The priciple of cosistecy leds to:...(5) Sice we re usig shell-type sigle-phse trsformer ll coils re woud o the sme leg. If the ; ; N N c c...(9) N,, c,, c d c re determied umericlly usig the rules of cosistecy, lekge d proportiolity., d c re determied usig the cosistecy priciple which results i (). c..()...(6) ;.(),, re otied from the mtrix computed y the BCTN routie d is computed y (4). This gives...(7). Tur-to-tur fult tur-to-tur fult o the primry divides the widig of the primry ito three su-coils s show if figure (3). + I.. I + i i N - c i c Figure 3. Sigle-phse trsformer with tur-to-tur fult o primry. - c is the computed usig () d (). I (), the lekge etwee the primry d the secodry coil is ssumed to e close to the lekge etwee the fulted coil o the primry d the secodry coil. 3. COPUTE SIUTION Figures 4 d 4 show the implemettio of tur-toerth d tur-to-tur fults i TP respectively. S source Esource Sfult Slo d lo d Figure 4. Simultio setup for tur-to-erth fult o the secodry The trsformer i this cse is represeted y the 4 4 mtrices [] d [] i (8). [] = c Ssource E source S fult S lo d lo d [] c c c c c [] is determied usig the reltios :...(8) Figure 4. Simultio setup for tur-to-tur fult o the secodry sigle-phse, 5Hz, two-widig, 5k, 7 / 4 trsformer is used for the simultios. I oth cses IJSE

4 o d Itertiol Jourl of Scietific & Egieerig eserch olume 3, Issue 5, y- 4 ISSN the primry of the trsformer is coected to idel siusoidl source, Esource, through switch, Ssource, closed t time, t. The secodry is coected to purely resistive lod, lod =.34 through swith, Slod, closed t time, t, Tur-to-erth d tur-totur fults re stged o oth widig of the trsformer. The currets d voltges o oth the primry d the secodry sides re moitored i dditio to the curret circultig through the shorted widigs. mitied t rms for ll cses. The secodry side is coected to vrile, pure, resistive lod. The lod used here ws.34 ohms. eters to mesure the voltges d currets o oth sides d lso the circultig curret i the shorted widig were coected s show i figure 5 ove. 5. ESUTS lidtio of the proposed method ws wveforms i two steps: 4. EXPEIENT SETUP Figure 5 shows the experimetl setup used to study the termil ehvior of trsformer uder vrious iterl widig fult coditios. The trsformer d lod hve the sme rtigs s used i the simultios. ric C T Power eter Figure 5. Experimetl setup with tur-to-tur fult o secodry. The primry of the trsformer hd 78 turs totl i lyer: turs i the first 6 lyers d 8 turs i the lst lyer. The widigs re mde of copper. The secodry hs two sets of widigs of 3 lyers ech mde of lumium sheets. The secodry could e coected for either (the two sets coected i prllel) or 4 (the two sets coected i series) output. For the work reported i this pper, the secodry ws coected for 4 output d fults were stged o the primry widig of the trsformer. The primry side of the trsformer ws coected to vric cple of supplyig up to 4, mximum. Due to high circultig curret i the shorted widig, voltge fr less th the rted ws supplied through the vric. For this experimet, the supply voltge ws. Prior to fults iititio, the wveforms of termil voltges d currets of oth the primry d secodry widig modeled usig methods i sectio II re compred to termil voltges d currets of primry d secodry widigs modeled usig the BCTN routie of TP. It ws foud tht the proposed model geerted wveforms similr to those geerted usig the BCTN routie of TP. This vlidtes the models for orml opertig coditios of the trsformer.. Uder fult coditios, ctul field experimets re coducted s explied i sectio I. Figure 6 shows the primry curret wveform otied durig simultio of tur-to-erth fult o the 8 th tur of primry d figure 6 shows the primry curret wveform for tur-to-tur fult etwee turs 337 d 364 of the primry. The fult iitited t t=.4 secods. Figure 6. Primry curret for tur-to-erth fult o the 8 th tur of primry. IJSE

5 Itertiol Jourl of Scietific & Egieerig eserch olume 3, Issue 5, y- 5 ISSN The results i tle show the simultio d experimetl results re quite close withi the limits of experimetl errors. The vlidtes the model. 6. CONCUSION method hs ee preseted to model d simulte iterl widig fults of two-widig, sigle-phse, distriutio trsformer. Simultio results idicte tht the proposed method yields correct results. Further, from tle, the results of the field experimets re i close greemet with the simultio results, thus vlidtig the proposed method. Figure 6. Primry curret for tur-to-erth fult etwee turs 337 d 364 of primry For fults o the primry side, the primry curret showed visile chge. The other termil vlues remied pproximtely costt efore d fter the fult. Tle gives compriso of the results etwee simultio d experimetl test. Cse P8_F is tur-toerth fult etwee the 8 th tur o the primry d the groud. Cse P4_5F is tur-to-tur fult etwee turs 337 d 364 o the primry. The i ' s re voltges i volts d the I i ' s re currets i mps. ll vlues re rms. The suscript I stds for the primry d for the secodry. Tle. Compriso of simultio d experimetl results Cse Prmeter Simultio Experimet P8_F I I.3.66 P4_5F I.45.5 I CKNOWEDGEENT The uthors thks to ITS deprtmet Gwlior d Director r. Sjeev Ji ITS Gwlior to cotoous ecourgemet to this work. 8. EFEENCES. Begtsso, C., Sttus d treds i trsformer oitorig, IEEE 995 Powertech Coferece, Stockhlom, Swede, pp IEEE Guide for the Iterprettio of Gses Geerted i Oil Immersed Trsformer, IEEE St drd C , New York IEEE Press, Steis, D. d., et l., Dissolved Gs lysis of Trsformers Oil, Pel Sessio, 997 Witer eetig. PES/ IEEE, Ferury 997, NY. 4. ll. D.., Prcticl ife-ssessmet Techiques for ged Trsformer Isultio, IEEE Proceedigs, ol. 4, No. 5 Septemer, 993, pp Bk-Jese, J., et l, Detectio of Fults d gig Pheome i Trsformer y Trsfer Fuctios, IEEE Trsctios o Power Delivery, ol., No., Jury 995, pp Swevelder, P, Hcke, G.P. Utilizig the Trsfer Fuctio i Trsformers Testig, ITC 94, y Stigt, S.. Frkli S.. The J & P Trsformer Book, th Ed., Joh Wiley & So, NY-Toroto. 8. Bstrd. P. et l, Trsformer odel for Widig Fult Studies, IEEE Trsctios o Power Delivery, ol. 9, No. pril 994, pp ltertive Trsiets Progrm (TP) ule Book, Cdi/meric ETP Users Group, IJSE

6 Itertiol Jourl of Scietific & Egieerig eserch olume 3, Issue 5, y- 6 ISSN IJSE