Parameters Affecting Lightning Backflash Over Pattern at 132kV Double Circuit Transmission Lines

Transcription

1 Parameers Affecing Lighning Backflash Over Paern a 132kV Double Circui Transmission Lines Dian Najihah Abu Talib 1,a, Ab. Halim Abu Bakar 2,b, Hazlie Mokhlis 1 1 Deparmen of Elecrical Engineering, Faculy of Engineering, Universiy of Malaya, 563 Kuala Lumpur, Malaysia 2 UM Power Energy Dedicaed Advanced Cener (UMPEDAC), Level 4, Wisma R&D, Universiy of Malaya, Jalan Panai Baharu, 5999 Kuala Lumpur, Malaysia a dnajihah@siswa.um.edu.my, b a.halim@um.edu.my Absrac In his paper, an analysis sudy on parameers which affecing he backflash over paern cause by lighning is done. A 132kV double circui ransmission line is modeled using ElecroMagneic Transien Program EMTP sofware for backflash over simulaion. A verically configured double circui ransmission line can be modeled ino several pars: owers, insulaors, phase conducors, ground wire and ower fooing resisance. The backflash over paern is simulaing by model he lighning curren ha hi he ground wire a he aim ower. The parameers ha include in his sudy are he values of fron, peak and ail of lighning curren, sriking disance and lasly he ower ground sysem. The paern can also be analysis by aking ino accoun he posiion of he phase conducors on he double circui ransmission ower. Keywords- Double Circui Transmission Line; Lighning Backflash Over Paern; EMTP; Lighning Curren; I. INTRODUCTION Backflash over generally occurs when lighning srikes he ground wire on ransmission line. The poenial power of he ower increases and affecs he resulan volage across he insulaor. When he resulan volage increases unil exceeded he insulaor limis, backflash over will be occurs. Many numerical simulaions have been used o sudy he lighning backflash over on ransmission line. One of he ools ha can be used is EMTP sofware. The EMTP, [1]-[2] is a common ool o simulae ransien evens in power sysem, which had been inroduced since 198. This paper presens he sudy on he backflash over paern a 132kV double circui ransmission line, [3]. The lighning which srikes he ground wire of he line can creae differen paern of flashover on phase conducors. The paerns are depending on many facors such as lighning curren magniude, fron and ail ime, he characerisics of ransmission ower, he posiion of phase conducors, ower grounding and sriking disance. The backflash over paern will be sudied for boh circuis since each circui have differen behavior. II. MODELLING EMTP sofware is used o simulae he model of ransmission line, owers, insulaors and lighning curren. The phase conducors and he ground wire are represened as frequency dependen line model due o line parameer which involved range of frequencies. Two se of wires circui which represen double circui ransmission line are modeled wih deails beween he owers A. 132kV Double Circui Transmission Tower The 132kV double circui ransmission ower wih wo ground wire is modeled. The ower is a verically configured as shown in Figure 1 and he heigh is 28.22m. The phase conducors of double circui line are arranged differenly for each circui. The firs circui, blue phase is arranged a he op follow by red and yellow. While for he second circui he posiions of he phase conducors are yellow, blue and red. Figure kV double circui ransmission line /12/$ IEEE 88

2 The lumped inducance model, shown in Figure 2 is choose o represen he ower as i provide more accuracy for ower less han 3m, [4]. The surge impedance of he ower can be calculaed using equaion (1)-(3) which recommended by IEEE and CIGRE, [5]. The formula is creaed using wais ower shape heory, [2]. B. Transmission Tower Fooing Resisance The value of ower fooing resisance can influence he lighning performance of ransmission line. Simple linear resisance, Rf is o be modeled in his paper. The value of he resisance o simulae he behavior of backflash over paern is given in Table IV. Tower op L1 l1 C. Insulaor Sring Flashover Model Top phase L2 l2 Middle phase L3 l3 Boom phase Figure 3. Insulaor sring flashover model Tower fooing Z Figure 2. The lumped inducance model Z = ln (H) (1) c L n Z 1 R = 6 ln[co{.5 an ( )] (2) H r1 h1 + r2 h + r3 h = (3) h R 2 Where: Z = ower surge impedance (Ω) c = speed of ligh (3 x 1 8 m s -1 ) n = 1,2 and 3 R is he equivalen radius of he ower represened by a runcaed cone, h= h 1 + h 2, and The figure 3 is shown he insulaor sring flashover model where a capacior parallel wih volage conrolled swich are conneced ogeher. The swich will be open when here is a flashover occurs a he insulaor. Equal area flashover model, [4] are used o show he operaion of he conrolled swich. During lighning, he volage across he swich will be increased and when i exceeds he criical flashover volage (CFO), flashover will occurs. The CFO volage can represen by equaion (5). V o =.9 5% ( ( ) V ) V D (4) gap 71 V =.9(4 + ) d (5). 75 Where: () = volage across insulaor sring V gap k =1 D =.245 d d =lengh of gap beween arc horn = ail ime of lighning curren waveform D. Lighning Curren Model The lighning sroke, shown in figure 4 is represened in double exponenial funcion waveform which includes he fron ime and he ail ime. The lighning peak curren, I O can be obained from he following equaion k r 1, r 2, r 3 h 1 h 2 = ower op, midsecion and base radii [m]; = heigh from midsecion o op [m]; = heigh from base o midsecion [m] Where, I i ( α β ) = ki ( e e ) (6) = peak of lighning curren, i ( ) = insananeous lighning curren 89

3 α, β = wave-head and wave-ail aenuaion quoien of lighning curren k = waveform correcion index Lighing curren model, [6] is used in he simulaion as i comply he behavior of double exponenial funcion. Figure 5 shows he model where Z O represen he lighning surge impedance, A represens lighning srikes poin and Z represens he impedance beween he breakdown poin and he ground. Numbers of lighning waveform wih differen fron ime and ail ime will be sudied o show he relaionship wih he lighning backflash over paern. Parameers corresponding o differen lighning curren waveforms are calculaed according o sandard waveform, as in Table I: III. DISCUSSION In his secion, he 132kV double circui ransmission line wih wo separae ac source is modeled using EMTP sofware as shown in Figure 8. Boh of he sources are synchronous wih each oher s. The ransmission line is conneced wih long cable from he source and he sysem is simulae using nine ower o represen balance sysem wihou refleced raveling wave from he far end of he ransmission line. A. Sriking Disance The lighning sriking disance is sudied in his secion o show he relaionship of flashover paern on double circui. Lighing sroke wih magniude of 12kV is srike on one of he ground wire, consan 1ohm ower resisance and consan ac source angle a 7 degree. A ac source angle of 7 degree, blue phase is a he highes volage value and follow by red and yellow phases for boh circuis which is shown in figure 6. The conducor wih highes volage value will ge more possibiliy o rip when lighning srike because i can exceed he CFO faser compare oher conducor. Figure 4. 8/2µs ligning curren waveform Figure 6. AC Source Volage according o phase angles Figure 5. Ligning curren model Figure 7 shows he volage across insulaor sring a he sriking ower, sriking disance. I is shown ha only blue and red phase of second circui line are rip. This is due o posiion of he rip conducor which is near o he ground compare he same phase conducor a he firs circui or also can be called coupling effecs. TABLE I. PARAMETERS OF STANDARD LIGHTNING CURRENT WAVEFORM Lighning Wave-head aenuaion quoien, α Wave-head aenuaion quoien, β correcion index, k 1.2/5µs /3µs /2µs /7µs /2µs /35µs DEV7/Air1@vb@1: Circui 1- BLUE phase, DEV7/Air2@vb@1: Circui 1- RED phase DEV7/Air3@vb@1: Circui 1- YELLOW phase, DEV7/Air4@vb@1: Circui 2- YELLOW phase DEV7/Air5@vb@1: Circui 2- BLUE phase, DEV7/Air6@vb@1: Circui 2- RED phase Figure 7. Volage across insulaor sring a sriking disance 81

4 Figure 8. EMTP simulaion of 132kV double circui ransmission line The paern of flashover is change a differen sriking disance; d=3, 6, 9 and 12m. There is no rip conducors are found when he lighning srike away from he sudied ower. I is found ha he induced volage magniude a he insulaor sring is decreases when he sriking disance is increases. Figure 9 and 1 shows he firs circui blue and he second circui blue conducor induced volage a insulaor wih increasing sriking disances. There is some delay which follows he increases of he disance due o ravelling ime of lighning curren o he sudied ower. B. Fron ime and Tail Time of Lighning Curren Referring o Table I, numbers of sandard lighning curren waveform (differen fron/ail ime, µs) are invesigaed o sudied he effecs of flashover paern on double circui line. The resuls of flashover paern are shown inside he Table II. I is noiced ha he smaller fron ime will creae more flashover a he conducors. A 1.2µs fron ime, hree conducors had experience flashover and similar wih 4µs. As i increases o 8µs, wo conducors are ripping. When he fron ime increases o 1µs, no more flashover are occurs. The induced volage creaed a he insulaor will increase more when he fron ime is faser and cause flashover. TABLE II. LIGHTNING WAVEFORM DEV7/Air5@vb@1: sriking disance, DEV6/Air5@vb@1: 3m sriking disance DEV5/Air5@vb@1:6m sriking disance, DEV4/Air5@vb@1: 9m sriking disance DEV3/Air5@vb@1:12m sriking disance Figure 9. Volage across insulaor sring a firs circui of blue conducor Lighning 1 s Cc Double Circui Flashover Paern 1 s Cc 1 s Cc Cc Cc 1.2/5µs X - - X X - 4/3µs X - - X X - 1/2µs /7µs /2µs X X - 1/35µs Cc Differen from fron ime, ail ime of lighning waveform did no give much effec on flashover paern. The increases of ail ime will give more ime for he over volage o be clear. DEV7/Air1@vb@1: sriking disance, DEV6/Air1@vb@1: 3m sriking disance DEV5/Air1@vb@1:6m sriking disance, DEV4/Air1@vb@1: 9m sriking disance DEV3/Air1@vb@1:12m sriking disance C. Peak of Lighning Curren Table III shows he resuls of flashover paern of double circui line on he effecs of lighning curren magniude. Figure 1. Volage across insulaor sring a second circui of blue conducor 811

5 TABLE III. Lighning Curren LIGHTNING WAVEFORM 1 s Cc Double Circui Flashover Paern 1 s Cc 1 s Cc Cc Cc 1kA kA X X - 14kA X X - X X - 16kA X X - X X - 18kA X X - X X - Cc 2kA X X X X X X Table III shows he relaionship beween he magniudes of lighning curren wih he numbers of conducor s flashover. More flashover occurs when he curren magniude increases. The paern shows ha blue and red phase conducor is faser o rip compare yellow phase due o he values of ac source volage for each conducor. The conducor which has higher volage will rip faser compare o lower volage. The blue and red conducors a second circui will flashover faser compare a he firs circui because he posiion of he conducor a ransmission line. Closer conducor o ground will rip faser due o coupling effec of he conducors. D. Tower Fooing Resisance Table IV shows he resuls of flashover paern of double circui line on he effecs of ower fooing resisance. TABLE IV. Fooing Resisance TOWER FOOTING RESISTANCE 1 s Cc Double Circui Flashover Paern 1 s Cc 1 s Cc Cc Cc Cc 5ohm ohm X X - 15ohm X X - X X - 2ohm X X X X X - 25ohm X X X X X X Resul in Table IV shows ha he paern of flashover a double circui is dependen on ower fooing resisance. Similar wih lighning curren magniude behavior, he numbers of flashover also increases when he value of fooing resisance increases. The paern also shows ha he blue and red for second circui will rip firs follow by firs circui. A 2 ohm, yellow conducor for firs circui is flashover faser compare o second circui. This is due o he posiion of yellow conducor a firs circui is lower compare a he second circui on he ransmission line. IV. CONCLUSIONS This paper has presened an analysis of parameers ha influenced he paern of lighning backflash over on double circui ransmission line. The parameers ha included in his sudy are lighning sriking disance, fron ime and ail ime of lighning curren, peak of lighning curren and lasly he ower fooing resisance. The sysem sudy of his paper is simulaed using EMTP sofware. The main conclusions are summarized below. The sriking disances give influences on he paern of he flashover. As he sriking disance increases, he induced volage a he insulaor sring will decrease. So less numbers of conducors will be flashover. Sandard lighning waveform wih differen fron ime and ail ime will give differen resuls of flashover paern. Smaller value of fron ime will increase induced volage a insulaor which will cause more flashover a phase conducors when i exceeded he CFO of he insulaor. Meanwhile he ail ime does no show much effec o he paerns. Higher peak or magniude of lighning curren will cause more flashover a he ransmission line. This due o higher curren flow o he insulaor and exceeded he maximum raing of he insulaor. Similar wih ower fooing resisance, here also will be more flashover occurs when higher resisance is used. REFERENCES [1] H. W. Dommel, EMTP Rule Book: B.P.A., [2] A. Ameani, T. Kawamura, A Mehod of a Lighning Surge Analysis Recommended in Japan Using EMTP, IEEE Trans. on Power Del., vol. 2, no. 2, April 25. [3] M. A. Sargen, M. Darveniza, Lighning Performance of Double Circui Transmission Lines, IEEE Trans. on Power App. and Sys., vol. 89, no. 5/6, May/June 197. [4] Sadovic, T., Sadovic, S., Emp_Rv Modelling for he Transmission Line Lighning Performance Compuaion. User Group Meeing. 2 April 29, Dubrovnik. [5] Helmuh O., Carlos A., Henry I., Modeling of Meal Oxide Disribuion Surge Arresers wih An Inenionally Conneced Series Gap, 28h Inernaional Conference on Lighning Proecion ICLP 26, ISBN: , Columbia. [6] Bruce, C.E.R., Golde, R. H., The Lighning Discharge, Journal of Insiuion of Elecrical Engineering, vol. 88, no , 1941, London. [7] Nuci, C. A., A Survey on CIGRE and IEEE Procedures for The Esimaion of The Lighning Performance of Overhead Transmission and Disribuion Lines. Elecromagneic Compaibiliy (APEMC), 21 Asia-Pasific Symposium, April 21 (pp ), Bologna, Ialy [8] A. R. Hileman, Insulaion Coordinaion for Power Sysems, New York: Marcel Dekker,