PERTURBAII OBINUTE LA DECONECTAREA N GOL A UNEI LINII DE 380 KV

DISTURBANCES OBTAINED AT A 380 kV UNLOADED LINE

DISCONNECTING

Petre TUALIU* Dan-Costin TUALIU* Aydogan OZDEMIR** Viorica VOICU*** *Universitatea din Craiova, Romnia, 200440, Craiova, Bd. Decebal nr. 117,

Tel.: +40-251-435724, fax: +40-251-436447, e-mail: ptusaliu@yahoo.com, ptusaliu@elth.ucv.ro, dtusaliu@yahoo.com **Technical University of Istanbul, Turkey, e-mail: ozdemir@elk.itu.edu.tr

***ICMET Craiova, Romnia.

Rezumat: Aceast lucrare prezint perturbaiile care apar n reeleleelectrice datorit fenomenelor tranzitorii de comutaie ale unei liniielectrice n gol de 380 kV. Fenomenele tranzitorii de comutaiestudiate rezult ca urmare a comutaiei ntreruptorului pentru olinie n go,l localizat n KEPEZ-YATAGAN din Turcia. Acest studiuse refer la valorile instantanee ale supratensiunilor (tensiuniletranzitorii de restabilire), supracurenilor, i cmpurilor electricepe durata primului ciclu dup comutaia liniei n gol, n particularla efectele posibile i perturbaiile asupra Reelelor electrice,Mediului i Vieii.Ca instrument de simulare a fost utilizat pachetulsoftware al Programului EMTDC / PSCAD. n simulare s-a consi-derat modelul de linie n T. A fost analizat, de asemenea, influenalungimii liniei de transmisie. Rezultatele modelrii au fost comparatecu rezultatele obinute analitic i prin modelare cu ajutorul Progra-mului MathCAD. n final,pe baza rezultatelor obinute, precum ipe baza lucrrilor publicate anterior de autori, au fost desprinseconcluzii care pot s fie utilizate n proiectarea ntreruptoarelorelectrice, n scopul creterii siguranei n funcionare i a compatibi-litii electromagnetice a reelelor electrice. Keywords: perturbaii, reele electrice, fenomene tranzitorii decomutaie, ntreruptoare electrice.

Abstract: This paper presents the disturbances that appear in powersystems due to switching transient phenomena of a 380 kV unloadedline. The switching transient phenomena that are studied resultfrom the circuit breaker switching of the 380 kV unload line locatedin KEPEZ-YATAGAN from Turkey. This study concerns the instanta-neous values of the overvoltages (transient recovery voltages),overcurrents and electrical fields during the first cycles after theswitching of the unload line, in special the possible effects anddisturbances in Power Systems, in Environment and in Life. Thesimulation tool used was the software package EMTDC / PSCADProgram. In the simulation it was considered the T model of line.It was also analysed the influence of the transmission line length.The modelling results are compared with the analytical resultsand the results obtained by MathCAD Program. Finally, someconclusions were extracted from the obtained results, as well asfrom previous published papers by the authors that can be usedby the circuit breakers designer in order to ensure a reliableoperation and an electromagnetic compatibility. Keywords: disturbances, power systems, switching transientphenomena, circuit breakers.

1. Introducere Solicitrile electrice n sistemul electroenergetic depind

de echipamentul de comutaie i de parametrii de configuraieai reelei [1-3]. Uzual, pentru comutaia i simularea fenome-nelor tranzitorii de comutaie capacitive (linii n gol i bateriide condensatoare) se folosesc ntreruptoarele electrice [5-9].Pentru obinerea de rezultate exacte, n studierea fenomenelortranzitorii, cel mai utilizat model este cel al liniei n T (modeluldependent de frecven). Acest model de linie este bazat peteoria undelor cltoare, care ine seama n perturbaiile de tensiune de funcia de ntrziere i de atenuarea formei de und.

Aceast lucrare este destinat s evalueze tensiunile tranzi-torii de comutaie, supratensiunilor pe fiecare faz i cmpulelectric, ca urmare a comutaiei liniei n gol, pentru diferitelungimi de linie. In acest scop, s-au considerat apte valori diferite de lungime, pentru linia n gol.

2. Abordarea analitic Analiza fenomenelor tranzitorii, la comutaia liniei n gol,

poate fi efectuat pe baza schemei modelului monofazic,urmtor, propus de [5,6], (fig. 1).

Fenomenele tranzitorii de comutaie ale liniei n gol pot fiexprimate, pe baza fig. 2, de urmtoarelor ecuaii (1-8) [5, 6]:

1. Introduction The voltage stress in the power systems depends of the

switching equipment and of the network configurationparameters [1-3]. Usually, for switching and simulation ofthe switching transient phenomena (unloaded lines andcapacitor banks) are used the circuit breakers [5-9]. The mostcommon approach is to use the T-model (the Frequency-Dependent model), which should be considered in transientstudies in order to obtain accurate results. The T-model ofline is based on the travelling waves theory, with the voltagedisturbances reflecting the delay function and the wave-shapeattenuation.

This paper is devoted to the evaluation of the transient recovery voltages, the overvoltages on each phases and theelectrical field, as following of the unloaded line switchingfor different lengths of line. In this way were assumed sevendifferent length values for the unload line.

2. Analytical approach The analysis of the switching transient phenomena at the

unloaded line switching can be made analytically by usingthe mono-phase schematic circuit proposed by [5, 6] (fig. 1).

Switching transient phenomena of unloaded line can beexpressed by figure 2 and following equations (1-8) [5,6]:

The 6th International Power Systems Conference

598

Fig. 1.Deconectarea unei linii n gol (n ambele reelele, general i redus, s-au neglijat rezistenele) Fig. 1. Disconnecting of the unloaded line (both the general network and a reduced network with neglected resistances are held)

a1) Model-echivalent; Model-equivalent a2) Rezistena neglijat; Resistance neglected b1) Diagrama fazorial; Phasor-Diagram b2) Diagrama fazorial; Phasor-Diagram c1) Valori instantanee; Instantaneous values c2) Valori instantanee; Instantaneous values

Fig.2. Modelul electric al unei linii n gol. Fig.3. Tensiunea tranzitorie de restabilire. Fig.2. Electrical Model of unloaded line. Fig.3. Transient recovery voltage.

( )

1 2

1 21

1 2

3 32 2

2 3 1 2 3 1 2

1 12 2

1 1cos / 1

C C C

LC C CLC C

U UU l v U L C U L C

+ ==

+= = =

(1)

1 2

2 2

1

2

2 0,203

21 0,797

0,62722 1

CC C

C C C

LL L

= = = =

= =

(2)

2 02 1 030 01 2

1 1dt L dtt tdiu u i u iC dt C

= = + + (3)

[ ] 102 03 02 0322 1 2 11

11 2

1

1R

RR

C Lu u u uL i

C C L pp LC LC C C

= = + ++ (4)

02 032 02 01 1 1

1 sint

R

R

u u tu u dtC L C L

C

= (5)

( )

+=

1

02031

022 cos1LC

tuuCC

uuR

R (6)

03-04.11.2005, Timioara, Romania 599

( )2 02 03 02 1,594u u u u= + (7) ( ) ( )1 2 2 3 2 max 2 1,594ru u u U U U= = + (8)

Tensiunea tranzitorie de comutaie maxim a fost calcu-lat pe baza ecuaiilor (1-8) [5,6] i este reprezentat n fig. 3.

Caracteristicile ntreruptorului i parametrii reelei dealimentare influeneaz fenomenele tranzitorii.

Viteza de cretere a rigiditii dielectrice (Ud = f (t)) i amplitudinea tensiunii tranzitorii de restabilire (Ur = f (t)), joac, de asemenea, un rol foarte important n acest proces[5-9].

3. Abordarea practic Analiza fenomenelor tranzitorii de comutaie, la deconec-

tarea unei linii n gol, ntr-o reea electric de 380 kV, a fostefectuat pe baza modelului din figura 4. Acest model a fostconceput pe baza pachetului software al ProgramuluiEMTDC / PSCAD. Linia de nalt tensiune de 380 kV asistemului electroenergetic (fig.4) prezint pentru analiz:generatoare, transformatoare, modelarea liniei de transmisie,prin modelul n T (moddelul dependent de frecven), magis-trala de bare, ramura bateriilor de condensatoare conectatla generator, ntreruptoarele pentru comutaia liniei i baterieide condensatoare. Fenomenele tranzitorii au fost simulatecu ntreruptorul pe poziia nchis, n prima etap, urmndoperaia de deconectare. Primul timp a fost de 0.205 [sec],iar al doilea timp de 3 [sec]. Pentru bateria de condensatoares-au adoptat valori discrete ale capacitii electrice de la 30F pn la 150 F, cu un pas de 20 F, considerndu-seconexiunea n stea.

The maximum of the transient recovery voltage wascalulated by the equations (1-8) [5,6] and is illustrated infigure 3.

The circuit breaker characteristics and the feeding networkparameters influence the transient phenomena. The growingspeed of dielectric rigidity (Ud = f (t)) and the amplitude ofthe transient recovery voltage (Ur = f (t)), play, also, a very important role in this process [5-9].

3. Practical approach The analysis of the switching transient phenomena at

disconnecting of an unloaded line in a 380 kV Electric PowerSystem, it was effected by model from figure 4. This modelwas evaluated using the EMTDC / PSCAD software package.The 380 kV High Voltage Line of the Power Systems (fig. 4)presents for analysis: the voltage generators; the transformer;the transmission line modelling by T-Line Model (Frequency-Dependent Model); the busbar, the branch of capacitor bank,connected on generator, the circuit breakers for the switchingof line and for switching of the capacitor bank. The transientphenomena were simulated with the circuit breaker on firstposition it was closed, following disconnecting operation.The 1st time was 0.205 [sec] and the 2nd time was 3 [sec].For capacitor bank they were assumed discrete capacitancevalues from 30 F until 150 F with a step of 20 F, consid-ering a star connection.

Fig. 4. Modelarea i simularea fenomenelor tranzitorii de comutaie utiliznd Programul PSCAD. Fig. 4. Modelling and simulation of the switching transient phenomena using PSCAD Program.

n Fig. 4 este prezentat scema electric pentru modelareai simularea fenomenelor tranzitorii de comutaie la deconec-tarea n gol a liniei de 380 kV, din Sistemul electroenergetical Turciei, utiliznd Programul PSCAD.

Fig. 4 presents the electrical scheme for modelling andsimulation of switching transient phenomena at the 380 kVunloaded line disconnecting, from Turkey Power Systems,using the PSCAD Program.

The 6th International Power Systems Conference

600

4. Rezultate Rezultatele sunt prezentate n urmtoarele tabele i

figuri:

4. Results The results are presented in the following tables and

figures: Tabelul 1. Tensiunile tranzitorii de restabilire la comutaia n gol a unei linii electrice de 380 kV

Table 1. Transient Recovery Voltages at 380 kV unloaded line switching l [km] 40 80 120 160 200 240 280

TRV_A[kV] 687,8 698,2 698,2 702,8 702,85 711,5 720,3 TRV_B[kV] 417,7 417,7 417,7 427,43 427,43 427,43 427,43 TRV_C[kV] 683,19 692,92 692,92 702,65 712,39 712,39 722,12

Tabelul 2. Tensiunile de faz la comutaia n gol a unei linii electrice de 380 kV

Table 2. Phase Voltages at 380 kV unloaded line switching l [km] 40 80 120 160 200 240 280

V_AL[kV] 315,04 315,04 315,04 322,12 322,12 329,2 336,28 V_BL[kV] 315,04 315,04 315,04 329,2 329,2 336,28 350,4 V_CL[kV] 316,81 316,81 320,35 332,74 332,74 332,74 344,25

Tabelul 3. Tensiunile tranzitorii de restabilire i tensiunile de faz la comutaia n gol a unei linii electrice de 380 kV

Table 3. Transient Recovery Voltages and the Phase Voltages at 380 kV unloaded line switching l [km] 40 80 120 160 200 240 280

TRV_A[kV] 687,8 698,2 698,2 702,8 702,85 711,5 720,3 TRV_B[kV] 417,7 417,7 417,7 427,43 427,43 427,43 427,43 TRV_C[kV] 683,19 692,92 692,92 702,65 712,39 712,39 722,12 V_AL[kV] 315,04 315,04 315,04 322,12 322,12 329,2 336,28 V_BL[kV] 315,04 315,04 315,04 329,2 329,2 336,28 350,4 V_CL[kV] 316,81 316,81 320,35 332,74 332,74 332,74 344,25

Tabelul 4. Tensiunile de faz i intensitile cmpurilor electrice sub o linie de 380 kV, la nivelul solului, pentru trecerile la nivel de

autostrad i linia de cale ferat Table 4. The Phase Voltages and the Electrical Fields, under 380 kV line, at grounded level, for the crossings of the National Highway

and Railway l [km] 40 80 120 160 200 240 280 V_AL[kV] 315,04 315,04 315,04 322,12 322,12 329,2 336,28 V_BL[kV] 315,04 315,04 315,04 329,2 329,2 336,28 350,4 V_CL[kV] 316,81 316,81 320,35 332,74 332,74 332,74 344,25

E_AL[kV/m] 8,5 8,5 8,5 8,7 8,69 8,88 9,08 E_BL[kV/m] 8,5 8,5 8,5 8,89 8,88 9,08 9,46 E_CL[kV/m] 8,56 8,56 8,65 8,99 8,99 8,99 9,29 E_AL[kV/m] 13,42 13,42 13,42 13,72 13,72 14,02 14,32 E_BL[kV/m] 13,42 13,42 13,42 14,02 14,02 14,32 14,92 E_CL[kV/m] 13,49 13,49 13,64 14,17 14,17 14,17 14,66

Tabelul 5. Intensitile cmpurilor electrice sub o linie de 380 kV, la nivelul solului, pentru trecerile la nivel de autostrad i linia de cale ferat

Table 5.Electrical Fields, under 380 kV line, at grounded level, for the crossings of the National Highway and Railway l [km] 40 80 120 160 200 240 280

E_AL[kV/m] 8,5 8,5 8,5 8,7 8,69 8,88 9,08 E_BL[kV/m] 8,5 8,5 8,5 8,89 8,88 9,46 E_CL[kV/m] 8,56 8,56 8,65 8,99 8,99 8,99 9,29 E_AL[kV/m] 13,42 13,42 13,42 13,72 13,72 14,02 14,32 E_BL[kV/m] 13,42 13,42 13,42 14,02 14,02 14,32 14,92 E_CL[kV/m] 13,49 13,49 13,64 14,17 14,17 14,17 14,66

0

100

200

300

400

500

600

700

800

[kV]

40 80 120 160 200 240 280

[km]

Transient Recovery Voltages due to Switching Transient Phenomena in a 380 kV unload Line of

Power Systems

l [km]

TRV_A[kV]TRV_B[kV]TRV_C[kV]

Phase Voltages due to Switching Transient

Phenomena in a 380 kV unload Line of Power Systems

290

300

310

320

330

340

350

360

40 80 120 160 200 240 280

[km]

[kV]

V_AL[kV]

V_BL[kV]

V_CL[kV]

03-04.11.2005, Timioara, Romania 601

Figura 5. Tensiunile tranzitorii de restabilire la comutaia n gol a liniei de 380 kV, pentru diferite lungimi.

Figure 5. Transient Recovery Voltages at switching of the 380 kV unloaded line, for different lengths.

Transient Recovery Voltages and the Phase Voltages due to Switching Transient

Phenomena in a 380 kV unload Line of Power Systems

0

100

200

300

400

500

600

700

800

40 80 120 160 200 240 280

[km]

[kV]

TRV_A[kV]

TRV_B[kV]

TRV_C[kV]

V_AL[kV]

V_BL[kV]

V_CL[kV]

Figura 7. Tensiunile tranzitorii de restabilire i tensiunile de faz la comutaia n gol a liniei de 380 kV, pentru diferite lungimi.

Figure 7. The Transient Recovery Voltages and the Phase Voltages at switching of the 380 kV unloaded line, for different lengths.

Figura 6. Tensiunile de faz la comutaia n gol a liniei de 380 kV, pentru diferite lungimi.

Figure 6. The phase voltages at switching of the 380 kV unloaded line, for different lengths.

0

2

4

6

8

10

12

14

16

[kV/m]

40 80 120 160 200 240 280

[km]

The Electrical Field under a 380 kV Line to crossing of the National Highway and Railway, at grounded level

E_AL[kV/m]E_BL[kV/m]E_CL[kV/m]E_AL[kV/m]E_BL[kV/m]E_CL[kV/m]

. Figura 8. Intensitile cmpurilor electrice sub o linie de 380 kV, la nivelul solului, pentru trecerile la nivel de autostrad i linia

de cale ferat. Figure 8. Electrical Fields, under 380 kV line, at grounded level,

for the crossings of the National Highway and Railway.

R1 0.006732 ohmkm

.

X1 0.061951 ohmkm

.

Y1 1.376592 ohm. km.Line length: 280.km

u2m t( ) u02max CR u03max u02max( ). 1 cos t omega0.( )(.

C1 U2max = 694721 kV

Figura 9. Aplicaie a Programului MathCAD la deconectarea LEA n gol. Figure 9. MathCAD Programs Application at the unloaded line diconnecting.

Electrical Field uder a 380 kV Line

0,00

5,00

10,00

15,00

20,00

-15 -10 -5 0 5 10 15

[m]

[kV

/m]

E(x)

Figura 10. Cmpul electric sub o linie de 380 kV, la nivelul solului,

pentru trecerile la nivel de autostrad i linia de cale ferat. Figure 10. The Electrical Field, under 380 kV line, at grounded level, for the crossings of the National Highway and Railway.

Tabelele 1-5 i figurile 5-11 arat influena lungimii liniei,

la comutaia n gol, asupra tensiunilor tranzitorii de restabilire,tensiunilor de faz i cpurilor electrice. Se observ ca valorile

ur t( )

t0 0.05 0.1 0.15 0.2

8 105

6 105

4 105

2 105

0Transient Recovery Voltage

Figura 11. Tensiune tranzitorie de restabilire, obinut pe baza

Programului MathCAD. Figure 11. Transient Recovery Voltage, obtained by MathCAD

Program. The tables 1-5 and the figures 5-11 show the influence of

line length, at unloaded switching, about the transient recoveryvoltages, phase voltages and electrical fields. It observes that

The 6th International Power Systems Conference

602

obinute sunt foarte nalte. Acestea pot genera influenepericuloase asupra Echipamentului electric, Mediului i Vieii.Se impune, ca o necesitate, mbuntirea mentenanei liniilori reelelor electrice, precum i a ntreruptoarelor electricede comutaie pentru a limita valorile maxime ale fenomenelortranzitorii de comutaie.

6. Concluzii

Din rezultatele obinute se desprind urmtoarele concluzii:- Ca urmare a fenomenelor tranzitorii de comutaie n Sistemul

electroenergetic apar perturbaii foarte periculoase pentruechipamentul electric i mediul nconjurtor. Dintre acestea,cmpurile electrice, n ultimul timp, sunt n atenia i preocu-prile multor specialiti, datorit efectelor lor negative asupraechipamentelor, mediului i vieii [5, 6, 9-12].

- Datorit comutaiei liniilor n gol apar n Sistemul electro-energetic supratensiuni mari (tensiuni tranzitorii de resta-bilire, 3.28 [p.u.]; supratensiuni de faz, 1.59 [p.u.]), caretoate genereaz cmpuri electrice, cu impact negativ, nsuiasupra Sistemului i Mediului nconjurtor.

- Rezultatele obinute prin modelare i simulare sunt n concordan cu soluiile teoretice (9.58 %).

- ntre modelarea obinut prin PSCAD Program i MathCADProgram, diferenele sunt foarte mici (0, 1 %).

- Rezultatele obinute pentru cmpurile electrice maxime,datorate comutaiei liniei electrice n gol de 380 kV, ncadrul Sistemului electroenergetic al Turciei, sub linie, lanivelul solului, (9.46 kV/m, la trecerea de nivel de autostradi 14.92 kV/m, la trecerea de nivel la reeaua electricaferoviar), arat c acesta sunt peste limitele admisibilerecomandate de normele internaionale CIGRE i IEEE [9].

- De aceea este necesar s se fac investigaii i s se impunmetode de limitare.

values obtained are very high. These can generate dangerinfluences about Electrical Equipment, Environment and Life.It is necessary to improve the maintenance of lines of powersystems and of circuit breakers switching for to limit themaximum values of the switching transient phenomena.

6. Conclusion From the obtained results the following conclusions can

be extracted: - As following of the switching transients phenomena in

Electrical Power Systems appear very danger disturbancesfor electrical equipment and for around environmental. Of these, the electrical fields, in last time, are in the preoccu-pations of the many specialists, thanks to their negativeeffect about equipment, environment and life [5, 6, 9-12].

- As following the unload lines switching appear in Power Systems the big overvoltages (transient recovery voltages,3.28 [p.u.]; phase overvoltages, 1.59 [p.u.]), which allgenerate the electrical fields, with negative impact about,item System, in Power Systems and around Environment.

- The results obtained by modelling and simulation are inaccording with theoretical solutions (9.58 %).

- Between modelling effected by PSCAD Program andMathCAD Program, the difference is very small (0, 1 %).

- The results obtained for the maximal electrical fields dueto a 380 kV unloaded line switching in Power Systems fromTurkey, under line at grounded level (9.46 kV/m, at thecrossing of the National Highway and 14.92 kV/m, at thecrossing of the National Railway), show that they overtakethe admissible limits recommended by the CIGRE andIEEE International norms [9].

- Therefore it is necessary to make investigations and toimpose the limited methods.

Bibliografie (References)

1. Shunt capacitor bank switching, stresses and test methods (2nd Part). Working Group 13.04 (Switching Test Methods). Electra no. 183, pp. 12-41, April 1999.

2. Shunt capacitor bank switching, stresses and test methods (First Part). Working Group 13.04 (Switching Test Methods). Electra no. 182, pp. 164-189, February 1999.

3. "Capacitive current switching". Working group 13.04 (Switching Test Methods). Electra no. 155, pp. 32-63, August, 1994. 4. Greenwood, A. Electrical Transients in Power Systems, Second Edition, John Wiley & Sons Inc, 1991. 5. Chowdhuri, P. Electromagnetic Transients in Power Systems, John Wiley & Sons Inc, 1996. 6. Tusaliu, P., Tusalu, V., Tusaliu, M., Tusaliu, D., About power system electromagnetic compatibility at the transients due to switching

operations, in Proc. of the 4th European Symposium on Electromagnetic Compatibility, September 11-15, 2000, vol. 2, pp.178-184, Brugge, Belgium.

7. Machado, C. M., Pinto, J. A., Barbosa, M. F. P., Influence of the circuit breakers reclosure in the transient stability of an electric power system using a new hybrid approach, in Proc. of the UPEC 2001, the 36th UniversitiesPower Engineering conference, University of Wales, 12th-14th September, 2001, Swansea.

8. Tusaliu, P., Device for strains determination of electric breakers, when simple or multiple capacitor banks are switched, Author's certificate of invention no.92383/1987, Bucharest, Romania.

9. Comparative electric field calculation and measurements on high voltage insulators. Working Group 03. Electra no. 141, pp. 74-132, 1992.

10. Marincu, A., Greconici, M., The electromagnetic field around a high voltage 110 kV electrical overhead lines and the influence on the biological sistems, in Proc. of the 5th International Power Systems Conference, November 6-7, 2003, Timisoara, Romania.

11. Magureanu, Gh., Ground electric field characteristics and measurement problems, in Proc. of the 5th International Power Systems Conference, November 6-7, 2003, Timisoara, Romania.

12. Ngamsanroaj, K., Tayati, W. An analysis of switching overvoltages in the EGAT 500 kV transmission system. Power Engineering, 2003 Large Engineering Systems Conference on 7-9 May 2003, IEEE, 2003, pg.149153.