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TP CH KHOA HC V CNG NGH, I HC NNG - S 4(39).2010

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NGHIN CU CC BIN PHP GIM IN P PHC HI TRN NG DY 500KV NNG-THNH M-PLEIKU

A RESEARCH ON METHODS TO REDUCE RECOVERY VOLTAGE ON 500KV DA NANG-THANH MY-PLEIKU TRANSMISSION LINE

Trn Vinh Tnh

Trng i hc Bch khoa, i hc Nng Lng Hu Nhn

Cng ty CP T vn Xy dng in 4

TM TT Nghin cu cc bin php v ng dng cc thit b nhm gim gi tr in p phc hi

trn ng dy truyn ti siu cao p 500kV nh: Lp in tr song song vi tip im chnh my ct (MC); Lp in tr phi tuyn vo tng pha MC xung t ; Lp t in song song vi tip im chnh MC; Lp t in vo tng pha MC xung t; Ni tt t b dc bng MC bypass (ni tt sau khi xy ra s c v trc khi tip im my ct m), kt hp hai trong cc bin php trn vi mc ch gip ch cho vic ch to, thit k, la chn, vn hnh my ct an ton v kinh t. y l mt vn ang rt cn thit cho h thng in.

Bi bo ny trnh by cc bin php v ng dng cc thit b gim in p phc hi trn ng dy 500kV Nng-Thnh M-Pleiku. Thc hin m phng trng hp my ct ngt mch cho gi tr in p phc hi cao nht v cc trng hp ng dng cc thit b nu trn bng phn mm EMTP(Electro Magnetic Transients Program). Kt qu cho thy cc bin php n gin, p dng cho h thng in siu cao p 500kV Vit nam c tnh kh thi cao.

ABSTRACT It is essential for the power system to study the methods and application equipment to

reduce the value of recovery voltage on 500kV super high voltage transmission lines by installing a resistor in parallel with the main-contact of a circuit breaker (CB), a nonlinear resistor between each phase of the CB with ground, or a capacitor between each phase of the CB with ground, by using a bypass serial-capacitor or a bypass circuit breaker (using a bypass after the occurrence of faults and before opening contacts of a circuit breaker), or by combining two of these measures for the purpose of manufacturing, designing, selecting and operating circuit breakers safely and economically. This paper presents methods and application equipment to reduce the recovery voltage on the 500kV Danang-Thanhmy-Pleiku Transmission Line. The performance of simulation for isolated short circuit case received results of the highest value in recovery voltage and cases of equipment application by using the Electro Magnetic Transients Program (EMTP) Software. The results show that the simple methods applied for the 500kV super high voltage power system is really feasible in Vietnam.

1. t vn [6], [7], [10] in p phc hi (RV: Recovery voltage) trong my ct (MC) l in p xut

hin gia hai u cc ca MC khi ct s c. in p ny c xt trong hai khong thi gian lin tc: Khong thi gian ban u tn ti in p qu (dao ng cao tn) hay gi in p qu phc hi (TRV) khong thi gian k tip tn ti in p xc lp tn


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s cng nghip. Trong qu trnh m tip im MC, h quang xut hin v dng in qua my ct gim dn v gi tr zero. S phn ng ca h thng n dng ct l nguyn nhn sinh ra TRV (Transient recovery voltage). Ni cch khc trong h thng, in p phn ng t pha ngun n ti qua MC gi l TRV, y l thng s quyt nh gii hn ct ca MC. Thao tc ct s thnh cng nu MC c kh nng chu ng c TRV v in p phc hi tn s cng nghip (hnh 1).

C hai thng s quan trng trong nghin cu TRV l: Bin cc i m thnh phn qu in p ny t c, ph thuc vo gi tr in p vn hnh bnh thng ca h thng, n th hin c tnh ct ca my ct in v c tnh ca tc gia tng TRV l RRRV (rate of rise of recovery voltage) quyt nh s thnh cng ca qu trnh ct mch hoc tht bi (phng in tr li gia hai cc tip xc ca my ct), ph thuc vo tn s dao ng trong sut qu trnh ngt mch. Hai thng s ny quan trng trong vic thit k, ch to cng nh vn hnh MC. C nhiu nguyn nhn dn n mc TRV cao xut hin trn MC nh: Ct ngn mch, ct ng dy khng ti, ct t ngt dng ti v ng m ngc pha.

2. Cc yu t nh hng n TRV v cc bin php gim TRV v RRRV [1], [2], [4], [6], [8], [9]

Gi tr TRV khng nhng ph thuc vo ch ph ti m cn ph thuc vo rt nhiu yu t ngu nhin khc. Cc yu t ngu nhin ny bao gm:

- Cc ch ct MC: nh ct s c, ct khng ti, ng m ngc pha 1800 . - Cc dng s c ngn mch: mt pha, 2 pha - t, 2 pha, 3 pha. - V tr s c. - Thi im m cc cc ca my ct. - Ch vn hnh ca h thng. c th tm ra c gi tr TRV ln nht c th, cn phi tnh ton vi cc ch

ph ti khc nhau v cc dng s c khc nhau. i vi mi ng dy, cc dng s c cn c m phng v tnh ton cho nhiu im s c khc nhau.

Do gi tr TRV ph thuc rt nhiu vo thi im s c cng nh thi im m cc cc ca MC. V vy, khi tnh ton gi tr TRV nht thit phi tnh n s phn b xc sut ca cc thi im ny. Phn mm EMTP cho php m phng xc sut thi im s c v thi im m cc cc tip xc ca MC c thc hin bng cc kho xc sut (statistical switch). Do i vi tng dng m phng s c, 100 tnh ton vi thi im s c v thi im m cc cc MC l ngu nhin (hnh 1).

- Thi im s c c l gi tr ngu nhin theo phn b u trong khong 0,015 0,00577 sec.

Hnh 1. Dng sng in p phc hi


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- Thi im m my ct l gi tr ngu nhin theo phn b u trong khong 0,05 0,00577 sec.

gim TRV v RRRV c th s dng mt s bin php sau: Lp in tr song

song vi tip im chnh MC; Lp in tr phi tuyn vo tng pha MC xung t ; Lp t in song song vi tip im chnh MC; Lp t in vo tng pha MC xung t; Ni tt t b dc bng MC bypass khi xy ra s c trn ng dy (ni tt sau khi xy ra s c v trc khi tip im my ct m), kt hp hai trong cc bin php trn.

3. Phn tch cc bin php gim gi tr TRV trn ng dy 500KV Nng Thnh M - Pleiku, m phng bng phn mm Emtp (Electro-Magnetic Transient Program)

3.1. Gii thiu [3], [5], [11]. ng dy 500kV Nng-Thnh M-Pleiku hnh thnh trn ng dy

500kV Nng-Pleiku (mch 1) sau khi a trm bin p 500kV Thnh M vo vn hnh, d kin vo nm 2015, c cng sut 2x450MVA c xy dng ti huyn Nam Giang, tnh Qung Nam, cch TBA 500kV Nng 76km v cch TBA 500kV Pleiku 203km, vi mc ch chuyn ngun cng sut t cc NMT Xekaman 3, Sng Bung 2, 4, k Mi 1, 4, ln h thng 500kV.

on ng dy 500kV Thnh M - Nng c chiu di 76km v khng c t b dc, gi tr TRV khng ng k. on ng dy 500kV Thnh M - Pleiku c chiu di 203km v c t b dc, gi tr TRV rt cao nn vic tnh ton v nghin cu bin php gim gi tr TRV cng nh RRRV rt cn thit nhm thun li cho vic la chn MC hp l v gi thnh h.

phn tch s thay i gi tr TRV, RRRV ng vi mi bin php do cc dng sng TRV, RRRV ca cc dng cng nh v tr s c trn ng dy c hnh dng gn ging nhau, nn y ch xt dng sng tiu biu cho dng s c v v tr s c cho gi tr TRV cc i, c th ngn mch 2 pha ti im 1 (hnh 2), kt qu tnh ton tng ng cho MC pha Thnh M, ti TBA 500kV Thnh M.

0 5 1 2 4 5 6 ms

Thi im s c Df Lnh ct D1 v D2

Hnh 2. Khung thi gian s c Df v thi im ct my ct D1, D2

THNH M PLEIKU

D1 D2

Df


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3.2. Kt qu m phng bng phn mm EMTP

3.2.1. Cha lp thit b gim TRV v RRRV Xt trng hp ngn mch pha pha, s c ti im 1 ch ph ti cc i

ca h thng in Vit Nam vo nm 2015. Cho gi tr TRV = 3,25pu; RRRV = 0,355kV/s v dng ngn mch qua my ct INM = 3,9kA. c m t trn hnh 3.

3.2.2. Lp in tr phi tuyn vo tng pha MC xung t pha ng dy.

Gi tr TRV = 2,8pu; RRRV = 0,316kV/s v dng ngn mch qua my ct INM = 3, 76kA. c m t trn hnh 4.

THNH MPLEIKU

D1 D2

1 2 3 4 5

113km90km

Hnh 3. Th t v tr s c trn ng dy 500kV Thnh M-Pleiku

Hnh 4b. Dng sng RRRV pha B MC Hnh 4a. Dng sng TRV 3 pha MC

Hnh 3a. Dng sng TRV 3 pha MC Hnh 3b. Dng sng RRRV pha B MC


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3.2.3. Lp t in song song vi tip im chnh my ct ng thi lp in tr phi tuyn vo tng pha MC xung t pha ng dy. Gi tr TRV = 2,5pu; RRRV = 0,165kV/s v dng ngn mch qua MC INM = 4,8kA. c m t trn hnh 5.

3.2.4. Lp in tr song song vi tip im chnh my ct. Gi tr TRV = 2,5pu; RRRV = 0,417kV/s, dng ngn mch qua MC INM = 3,6kA. c m t trn hnh 6.

3.2.5. Lp in tr song song vi tip im chnh my ct v lp in tr phi tuyn vo tng pha MC xungs t pha ng dy.

Gi tr TRV = 2,15pu; RRRV = 0,28kV/s, dng ngn mch qua MC INM = 3,8kA. c m t trn hnh 7.

Hnh 5a. Dng sng TRV 3 pha MC Hnh 5b. Dng sng RRRV pha C MC



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4. Kt lun

Kt qu tnh tan gi tr TRV v RRRV ca MC 500kV trn ng dy 500kV Thnh M-Pleiku vi cc trng hp lp thit b gim gi tr TRV, xt vi dng s c ngn mch pha-pha ti im 1, c m t trn hnh 8. Cho thy cc trng hp u cho gi tr TRV gim ng k so vi khi cha lp thit b gim TRV, gi tr TRV = 3,25pu.

Trng hp lp in tr phi tuyn vo tng pha MC xung t, gi tr TRV =

2,8pu, gim 13,8%, trng hp ny hin nay c s dng ph bin trn h thng in Vit Nam.

Trng hp lp in tr song song vi tip im chnh my ct, gi tr TRV = 2,5pu gim 23,07%, trng hp ny phi lp thm in tr m, lm tng gi thnh my ct.

Hnh 8. Dng sng TRV ca my ct ng vi cc bin php gim TRV.



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Trng hp lp t in song song vi tip im chnh my ct v lp in tr phi tuyn vo tng pha MC xung t pha ng dy, gi tr TRV = 2,5pu, gim 23,07%, trng hp ny cha c s dng, chi ph lp b t s lm tng chi ph d n.

Trng hp lp in tr song song vi tip im chnh my ct v lp in tr phi tuyn vo tng pha MC xung t pha ng dy, gi tr TRV = 2,15pu, gim 33,85%, trng hp ny phi lp thm in tr m, gi tr TRV gim ng k.

Hin nay kh nng ch to MC ca cc hng ch to c g tr TRV nh hn gi tr yu cu ca MC 500kV Thnh M (3,25pu), gy kh khn cho vic sn xut my ct in, ng thi chi ph rt cao nn vic nghin cu bin php gim TRV l rt cn thit. Theo kt qu th nghim TRV cho MC ca mt s nh ch to MC trong nhng nm gn y cho thy trng hp p dng bin php lp in tr song song vi tip im chnh my ct v lp in tr phi tuyn vo tng pha my ct xung t pha ng dy, gi tr TRV = 2,15pu xc sut xut hin l 1%. Trng hp ny TRV ca my ct c ch to hin nay tho mn TRV yu cu nn lm gim chi ph cho vic lp t my ct (ch dng 01 my ct).

TI LIU THAM KHO

[1] Phm Vn Chi, Bi Tn Hu, Nguyn Tin Tn, Kh, NXB Khoa hc v K thut, H Ni, 2008.

[2] Trn Vn Tp, K thut in Cao p, H Ni, 2007. [3] Trm bin p 500kV Thnh M, H s thit k k thut, giai on 2, Nha Trang,

2007. [4] L Cao Quyn, Trn Quc Tun, Lm Du Sn, Nguyn Hng Anh (2007), Nghin

cu qu trnh qu in t trn h thng in 500kV Vit Nam, Bo khoa hc v cng ngh, i hc Nng.

[5] Tp on in lc Vit Nam, Quy hoch pht trin in lc Quc gia giai on 2010-2015 c xt n nm 2025, H Ni, 2007.

[6] R.W.Alexander, PPL, D.Dufournet, Alstom T&D, Transient Recovery Voltage (TRV) for high-voltage circuit-breakers.

[7] Ruben D. Garzon, High voltage Circuit breakers, New York. [8] H.S.Park, J.W.Woo, J.W.Kang, K.S.Han, S.O.Han, Analyzing TRV of CB when

installing current limit reactors in UHV Power systems. [9] Q.Bui-Van, B.Khodabakhchian, H.Huynh, B.de-Metz-Noblat, Transient

simulation study for the 1500km North-South 500kV interconnection in VietNam. [10] Lou van der Sluis, Transients in Power Systems, England, 2001. [11] Branch of System Engineering Bonnerille Power Adminitration Portlan, Oregon

97208-3621 United States of America Electro-Magnetic Transients Program Theory Book.

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