TRANSIENT VOLTAGE DISTRIBUTION IN TRANSFORMER WINDING (EXPERIMENTAL INVESTIGATION)

Transcription

1 IJRET: Interntionl Journl of Reserh in Engineering nd Tehnology ISSN: TRANSIENT VOLTAGE DISTRIBUTION IN TRANSFORMER WINDING (EXPERIMENTAL INVESTIGATION) Knhn Rni 1, R. S. Goryn 2 1 M.teh Student, 2 Professor, Eletril Deprtment IIT (BHU), VARANASI, U.P Indi, knhn.rni.eee11@ithu..in, rsgoryn.eee@iithu.. Astrt In this work, the non-liner voltge distriution in trnsformer winding is investigted tht ours due swithing nd lightning. Trnsformer winding is modeled in the lterntive trnsients progrm (ATP) version of Eletromgneti trnsients progrm (EMTP- RV). EMTP softwre is used to simulte the very fst trnsient overvoltge. An experimentl setup tht onsist of, Reurrent surge genertor, CRO nd trnsformer winding model hs een developed nd voltges mesured t different point long the trnsformer winding. Simultion results show good greement with the experimentl result. Index Terms: Very fst trnsient overvoltges, internl resonne, impulse voltge distriution, dis winding *** INTRODUCTION It is well known tht swithing opertion in the Gs insulted swithgers (GIS) produes very fst trnsient over voltges (VFTO). VFTO hve very short rise time of.1µse or less nd its min osillting frequeny rnge is in etween 1MHz to 50MHz [1]. The distriution of these trnsient over voltges in trnsformer winding is highly non uniform. It hs een oserved tht 60 Perent of these voltges ppers ross first 10 perent length of the winding. This non uniform voltge distriution n dmge the trnsformer insultion [2]. This work dels with the voltge distriution in the trnsformer winding when its terminl is exited with impulse voltge. Study is imed to nlyze the nture of the internl voltge mplifition nd voltge stress t vrious points of trnsformer winding with impulse exittion. A trnsformer winding model is developed on the EMTP softwre. Simultion results re ompred with the experimentl results nd stisftory result re otined. 2. TRANSFORMER WINDING MODEL For the study of the trnsients response of the trnsformer high frequeny iruit model of 100 KVA trnsformer model hs een developed sed on geometry nd onfigurtion. While lulting phenomen ssoited with suh high frequenies, the pitne of trnsformer winding is importnt, lthough it is of no importne t power frequeny voltge levels. The most detiled model of the trnsformer is one in whih every turn of the winding is represented nd ll pitnes nd indutnes re inluded. Suh model my e prohiitive in terms of memory nd omplexity. The detils n e redued, y tking some ssumption, to simplify L, C, network without losing muh ury. A shemti digrm of the developed model is shown s in Figure1 Fig. 1: Simplified Equivlent model for Trnsformer Winding It is ssumed tht the winding is uniform i.e. ll the series pitne re equl nd ll shunt pitne re equl nd ll series indutnes re equl. 3. TEST TRANSFORMER AND CALCULATION OF WINDING PARAMETERS 3.1. Test Trnsformer desription To determine the trnsient s voltge distriution in the trnsformer windings, it is neessry to lulte the prmeters of the winding i.e. indutne nd pitne. The study hs een done on 100 KVA single phse trnsformer hving ontinuous disk type H.V. winding. The trnsformer dt is given in Tle 1. Volume: 02 Issue: 04 Apr-2013, 579

2 IJRET: Interntionl Journl of Reserh in Engineering nd Tehnology ISSN: Rting H.V. voltge Tle 1: Test Trnsformer dt 100 kva 11 kv Outside dimeter Men length of turn 507mm 1432mm 649 mm 1916mm L.V. voltge Frequeny Insultion etween ore nd L.V. winding Insultion over ondutor Insultion over lyer Insultion over L.V. nd H.V. winding 433V 50Hz Blised Pper Pper Pper Blised pper Tle 2 nd 3 present ore nd windings dt for the Test Trnsformer. Tle 2: Trnsformer Core dt 3.2 Determintion of the trnsformer winding prmeters Cpitne lultion: Dis to dis pitne for the winding hve een lulted from the priniple of eletrostti energy onservtion [3]. Net series pitne is given s: Cs = Where, D =men winding dimeter N=numer of dis in the trnsformer n =numer of turn per dis h=width of opper strip ondutor = inter dis spe =thikness of insultion Dimeter of ore Width of window Height of window CRGO lmintion Distne etween enter of djent lim 375 mm 375 mm 1335 mm.33 mm 685 mm Dis to ground pitne for winding hve een lulted ssuming tht the oil, ore leg nd the metl tnk form ylindril eletrode system. Net shunt pitne is given s: Where, = Rdius of ore = Inner rdius of L.V. winding = Outer rdius of H.V. winding d = Inner rdius of H.V. winding Axil length of the H.V. winding Tle 3: Trnsformer Winding dt Winding L.V. H.V. Indutne lultion [4]: We hve, L=.001 Type of winding Helil Dis Current density 2.75 A/mm A/mm2 Cross re of ondutor 55 mm mm2 Numer of dis TRANSFORMER WINDING RESPONSE TO IMPULSE VOLTAGES Inside dimeter 405mm 571mm When nlyzing the impulse voltge distriution in the trnsformer winding pitive network is onsidered. In other words, the presene of series pitnes etween Volume: 02 Issue: 04 Apr-2013, If =4 <.2, then

3 IJRET: Interntionl Journl of Reserh in Engineering nd Tehnology ISSN: winding setions uses the trnsformer to respond to rupt impulses s network of pitnes for ll frequenies ove its lower nturl frequenies of osilltions. And re the totl ground pitne nd series pitne of the trnsformer winding respetively. The rtio hs een denoted y the distriution onstnt α. To improve the trnsients response nd to redue the dis to dis voltge grdient the vlue of α is s smll s possile. One wy to redue the vlue of α is to inrese the vlue of whih n e hieve y interleving nd inter-shielding [5] Simultion Result The ehviorl response of the high voltge winding of the trnsformer hve een nlyzed using EMTP y simulting the iruit shown in Fig-1. An impulse voltge soure hving pek voltge 40 volt is pply on the exittion terminl nd the voltge t vrious node is mesured. The node voltge t 2 nd,3 rd nd lst node is shown in elow with isolted neutrl. fig - 2, fig-3 nd fig-4 show the node voltges when α is 10,3.5 nd 1 respetively. Fig3: node voltge when α =3.5 t. 2 nd node.3 rd node. lst node Fig2 : node voltge when α =10 t - 2 nd node - 3 rd node - lst node Fig4: node voltge when α = 1 t. 2 nd node. 3 rd node. lst node Volume: 02 Issue: 04 Apr-2013, 581

4 IJRET: Interntionl Journl of Reserh in Engineering nd Tehnology ISSN: Experimentl results The trnsient response of the trnsformer winding is investigted using experimentl set up s shown in Fig 5 Fig 7: node voltge when α =3.5 t. 2 nd node. 3 rd node. lst node Fig 5 : Experiment set-up In the experiment the sme impulse voltge s in simultion ws injeted to the trnsformer winding model using the reurrent surge genertor nd the voltge t vrious node is oserved using CRO. Fig 6: node voltge when α = 10 t. 2 nd node. 3 rd node. lst node Fig 8 : node voltge when α =1 t. 2 nd node. 3 rd node. lst node CONCLUSIONS The result otined from the EMTP simultion losely grees with the experimentl results. Impulse response of trnsformer winding is osilltory. If the osilltion frequeny equls the trnsformer nturl frequeny, then osilltory trnsients response n trigger internl resonne. Voltge t different node shows tht osilltion is redued s the vlue of α is dereses. Volume: 02 Issue: 04 Apr-2013, 582

5 IJRET: Interntionl Journl of Reserh in Engineering nd Tehnology ISSN: Results lso indite tht voltge distriution in the trnsformer is highly non uniform with lrger vlue of α s ompre to when vlue of α is low.. ACKNOWLEDGEMENTS The uthors wish to thnk Prof. S.P. Singh, the Hed of Eletril Engineering, Indin Institute of tehnology (BHU) Vrnsi for providing neessry omputtionl nd lortory fility for suessful ompletion of this work. REFERENCES: [1]. Y. Shiuy, S. Fujit nd T. Shimomur Effets of very fst trnsients overvoltge on trnsformer IEE, volume 146 No.4 july [2]. Go Youhu,Yun Hong, Wng Erzi, nd Co Yundong Clultion Of Very Fst Trnsients Over-Voltge And Its Distriution In Trnsformer Winding In 110 kv GIS.proeedingof interntionl onferene on eletril mhines nd systems 2007,ot 8~11 Seoul Kore [3] Roert M. Delvehio, Bertrnd poulin, Dilip Kumr M. shh, Rjendr Ahuj Trnsformer Design priniple Chpter 12. [4].Grover, F.W., Indutne Clultions: Working Formuls nd Tles, Dover Pulition, In [5] Mehdi Bgheri, Mehdi Vkilin, Arsln Hekmti, Rouhollh Heidrzdeh Influene of Eletrostti Shielding of Dis Winding on Inresing the Series Cpitne in Trnsformer Power Teh, 2007 IEEE Lusnne. BIOGRAPHIES: Otined the Under Grdute degree from B.B.D. Ntionl Institute of Tehnology & Mngement, Luknow. Presently doing Post Grdution from Indin Institute of Tehnology, BHU, Vrnsi Otined the Under Grdute nd Msters degree from University College of Engg. Burl, Smlpur University, Odiss, nd Ph.D. from Institute of Tehnology, BHU, Vrnsi. Presently, working s Professor in IIT (BHU) Vrnsi. Volume: 02 Issue: 04 Apr-2013, 583