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A. Cc bo co chung
1
TNG CNG N NH, TIN CY CA LI IN 500 kV
SAU CC S C MT IN DIN RNG
V S CN THIT PHI TRANG B H THNG BO V
CHNG MT IN DIN RNG
Nguyn c Ninh
Trung tm iu h thng in Vit Nam
Tm tt: Cng vi s pht trin ca ngun in nhm p ng tc tng trng
ph ti cao, h thng in truyn ti xng sng 500 kV lin kt cc min ng
vai
tr rt quan trng trong vic cung cp, trao i in nng an ton v kinh
t. Vi
xu hng truyn ti ngy cng ln c v cng sut ln sn lng, vic vn hnh
h
thng in 500 kV tr nn rt phc tp.
Trong bi cnh nhu cu truyn ti trn h thng in 500kV c xu hng
ngy
cng tng, bo co trnh by nhng kh khn, nguy c mt n nh trong qu
trnh vn hnh v tng kt mt s s c nghim trng in hnh trn HT 500kV
trong nhng nm gn y.
Xut pht t nhu cu thc t, bo co cng nu r s cn thit phi trang b
h thng bo v chng s c din rng v nu nhng c im c bn ca h
thng ny.
1. QU TRNH PHT TRIN CA H THNG IN 500 kV BC - NAM
1.1. H thng in Vit Nam trc nm 1994
Cng ngh pht in xut hin ti Vit Nam vo cui th k XIX di hnh thc mt
s nh
my pht in c lp cung cp trc tip cho li in khu vc. Khi min Bc Vit
Nam c
gii phng nm 1954, tng cng sut in quc gia ch t 100 MW vi li in
tha tht v
cp in p cao nht 30.5 kV. H thng in pht trin tt trong giai on
1975-1994 vi s
tham gia ca mt s cng ngh tin tin, cc nh my in ln nh nh my nhit
in Ph Li
(4x110 MW), Nh my thy in Tr An (4x100 MW) v c bit l Nh my thy in
Ha
Bnh (8x240 MW) ln lt c a vo vn hnh. Trong giai on ny, li in
truyn ti
pht trin trn ton quc vi cp in p cao nht l 220 kV nhng vn cha lin
kt h thng
in ba min thnh mt h thng hon chnh. H thng in ti ba min c iu hnh
c lp
bi cc trung tm iu ca cc cng ty in lc min Bc, min Trung, min Nam.
Do cha
c lin kt gia cc min nn cc thi im khc nhau mt s khu vc d tha in
nng
trong khi nhng khu vc khc b thiu ht, cc vn v n nh ca cc h thng v
cht
lng in nng cng thng xuyn gp phi.
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HI NGH KHOA HC V CNG NGH IN LC TON QUC 2014
2
1.2. Vn hnh ng dy 500 kV Bc - Nam mch 1
T nm 1994, ng y siu cao p 500 kV mch 1 c a vo vn hnh kt ni h
thng
in min Bc, Trung, Nam thnh mt h thng duy nht. ng dy 500 kV vi
chiu di
1488 km lin kt h thng in 3 min qua 5 trm bin p 500 kV (Ha Bnh, H
Tnh,
Nng, Pleiku, v Ph Lm) ng vai tr quan trng to nn s cn bng nng lng
ti u
gia ba min. Trong nhng nm u, in nng d tha ca thy in Ha Bnh v cc
nh my
in min Bc c truyn ti p ng nhu cu cp in cho min Trung v Nam.
Trong cc
nm t 1994 n 2000, tng in nng trao i gia cc min t 40 t kWh, t
13.8% tng
sn lng in quc gia.
1.3. Vn hnh ng dy 500 kV Bc - Nam mch 2
Cng vi s pht trin ca nn kinh t, h thng in 500 kV ang ngy mt m
rng vi nhiu
ng dy lin kt gia cc vng min. T nm 2004, cc d n lin quan n ng dy
500
kV Bc - Nam mch 2 bt u c thc hin. ng dy 500 kV mch 2 c tc dng
nng
cao kh nng truyn ti gia cc min v nng cao kh nng hot ng an ton ca
h thng
trong cc ch s c N-1.
Bn cnh , cc ng dy quan trng khc cng c a vo vn hnh: ng dy Ph
Lm
- Nh B - Ph M gii ta cng sut trung tm nhit in Ph M vi cng sut lp
t
4000 MW (2004 - 2005); cc ng dy truyn ti v tng cng lin kt vi khu
vc ng
Bc min Bc; cc ng dy lin kt vi cc ngun thy in khu vc Sn La - Lai
Chu;
ng dy 500kV mch 3 Pleiku - M Phc Cu Bng (2014) Ngoi ra, cc d n
thay
th thit b tng cng kh nng truyn ti trn li 500 kV/220 kV v ang tng
bc
c thc hin p ng nhu cu cung ng in.
Nh vy, trong bi cnh nhu cu trao i in nng gia cc vng/min ngy cng
tng, h
thng 500 kV pht trin tr thnh xng sng ca ton b h thng in quc gia,
ng
vai tr quan trng trong vic kt ni cc khu vc ph ti/ngun in trn ton
quc gp phn
m bo vn hnh h thng in an ton, kinh t.
n cui nm 2013, h thng 500 kV c tng chiu di 4887 km v 20 trm bin
p (tng cng
sut 19350 MVA). Ph ti ln nht c ghi nhn trong nm 2013 l: quc gia
- 20010 MW;
min Bc - 9081 MW; min Trung - 2383 MW; min Nam - 9687 MW. Sn lng
tng ng
l: Quc gia - 129655 t kWh; min Bc - 51539 t kWh; min Trung -
12801 t kWh; min
Nam - 64207 t kWh [1].
2. MT S VN V TRUYN TI IN V VN HNH H THNG IN
500 kV N NH
c im a l ca t nc di v hp, nh hng n vic phn phi cc ngun pht
ti
Vit Nam. Cc dng ngun in chnh bao gm thy in, nhit in than, nhit
in turbin kh
(chu trnh n v chu trnh hn hp). Cc nh my thy in tp trung cc khu
vc Ty Bc
min Bc, khu vc min Trung v khu vc Cao Nguyn min Nam. Cc nh my
nhit in
than c xy dng gn ngun nng lng s cp trong khu vc ng Bc min Bc,
khu vc
Bc Trung B. Cc nh my in turbin kh nm hai khu vc ng Nam B v Ty
Nam B.
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A. Cc bo co chung
3
Bn cnh , ph ti h thng in quc gia tp trung ch yu min Bc v min Nam
c
bit l khu vc th H Ni v thnh ph H Ch Minh.
Do c im phn b khng ng u cng nh ch hot ng khc nhau ca cc dng
ngun in, li in 500 kV thng xuyn phi truyn ti mt lng cng sut rt
ln, c bit
l cc ng dy Nho Quan H Tnh Nng trn giao din Bc Trung, cc cung
on
ng dy t Pleiku n Ph Lm trn giao din Trung Nam. Xu hng trao i in
nng
gia h thng in cc min ngy cng tng th hin trong bng 1 [1],[2].
Bng 1. in nng truyn ti gia cc min nm 2013 v c tnh cc nm 2014 -
2020
Giao din truyn
ti
Sn lng truyn ti nm (GWh)
2013 2014 2015 2016 2017 2018 2019 2020
Bc - Trung 3683 9535 12009 17460 18921 18513 17888 14967
-> 5379 9678 12009 17460 8921 18513 17932 15091
12471 15456 17493 22419 22523 20423 18231 21769
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HI NGH KHOA HC V CNG NGH IN LC TON QUC 2014
4
Hin tng sp in p gy st gim in p ti u nhn cng sut thng xut hin
khi
truyn ti 500 kV cao. Sp in p cng c th xut hin u nhn cng sut do
hu qu
ca s c cc ng dy 500kV quan trng hoc s c gy mt mt lng ngun ln
u
nhn cng sut (s c t my, s c gim/ct kh) gy ra hin tng tng cng sut
truyn ti
trn cc ng dy lin kt. Theo kt qu tnh ton hin tng vi cu hnh h thng
in nm
2014, hin tng sp in p c th xut hin trong ch cao im trn ng dy H
Tnh
- Nng khi truyn ti trn 2400/1980 MW ng vi ch vn hnh 2 mch/1 mch,
trn cc
ng dy t Pleiku n Ph Lm l 3600/2600 ng vi ch vn hnh 3 mch/2
mch
ng dy [3].
Hin tng mt n nh ng trn h thng in c th xut hin khi c s c ln trn h
thng
in. Tng kt cc s c ln cho thy mt n nh ng thng do s c cc ng dy 500
kV
khi ang truyn ti cao, in hnh l cc ng dy Nho Quan - H Tnh - Nng,
cc ng
dy t Pleiku - Ph Lm. Theo tiu ch s c N-1 cc ng dy 500 kV, gii hn
truyn ti
trn cc giao din Bc - Trung, Trung - Nam nm 2014 c tnh ton t xp x
1600 MW
v 2300 MW (ng vi cu hnh 3 mch ng dy 500 kV) [3]. Trong cc s c
trn, vic
cc mch sa thi c bit, mch sa thi ph ti theo tn s, mch sa thi ph
ti theo in p tc
ng ng vai tr ht sc quan trng trong vic lm gim nguy c s c lan
rng. Nh , c
th xem xt cho php truyn ti cng sut trn cc giao din mc cao hn gii
hn truyn ti
tnh ton trong mt s trng hp cn thit.
Mt s hin tng, s c in hnh trn h thng in trong mt vi nm tr li
y:
(1) S c ngy 27/12/2006 lc 14h43 ti trm bin p 500 kV Pleiku. Mt
my ct 500 kV
khng thc hin ct c khi c lnh ct do li h thng ngun nui DC. Chc nng
chng h
hng my ct (50BF) tc ng thc hin ct thanh ci ti trm Pleiku. Trong
thi im trc s
c, mt my ct kt ni vi thanh ci khc ca trm Pleiku c tch ra khi vn
hnh, gy
ra hin tng tro lu cng sut chy vng t Ialy ti Ph Lm, tr li thanh
ci Pleiku v ti
Nng. Hin tng dao ng in xy ra do lin kt 500 kV qu yu;
(2) Dao ng in trn ng dy 500 kV Pleiku - Nng lc 11h30 ngy
24/4/2008. Bo v
khong cch (F21) ti trm Nng nhn bit c dao ng cng cng sut trn
ng
dy. Ti thi im ny, ng dy 500 kV Nng - H Tnh ang vn hnh mt mch
duy
nht. Cng sut truyn ti trn cc ng dy Pleiku - Nng, Nng - H Tnh ln
lt l
1040 MW v 690 MW;
Hin tng dao ng gy ct cc ng dy 500 kV Nng - H Tnh, Nng - Pleiku,
h
thng in b tch i ti H Tnh, Nng. Tip theo bo v qu p tip tc ct ng
dy 500
kV H Tnh - Nho Quan;
(3) S c ngy 04/10/2012: s c gy nhy ng dy Di Linh Tn nh khi ang
truyn ti
cao cng sut vo min Nam, dn n dao ng v gy nhy c ng dy kNng Ph
Lm lm tch mng h thng in min Nam khi h thng in Quc gia. H thng sa
thi ph
ti theo tn s thp tc ng ct 2147 MW;
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A. Cc bo co chung
5
(4) Ngy 02/4/2013, NM C Mau 2 (620MW), Ph M 1 GT3 (174 MW) ln lt
ngng do
s c. Trong ngy c thi im in p ti cc thanh ci 500 kV Ph Lm, Tn nh
xung ti
417 427 kV, k s vn hnh ra lnh sa thi 300 MW u ngun 110 kV m bo
ch
in p min Nam;
(5) S c ngy 26/4/2013: Do iu kin vn hnh phi bypass 2 t b dc ti
Nho Quan trn
ng dy Nho Quan - H Tnh v 4 t b dc ti H Tnh trn ng dy H Tnh - Nho
Quan
v H Tnh - Nng dn n hin tng dao ng cng sut v gy nhy 2 mch ng
dy
H Tnh - Nng lm tch mng h thng in min Bc vi h thng in min Trung
v
min Nam;
(6) S c ngy 22/05/2013: s c gy nhy ng dy Di Linh - Tn nh khi ang
truyn ti
cao cng sut vo min Nam, dn n dao ng v gy nhy mt s t my khu vc
min Nam
v ng dy kNng - Ph Lm lm tch mng v gy mt in ton b h thng in
min Nam.
3. CC PHNG PHP HIN HU PHNG CHNG MT IN DIN RNG
Vi mc tiu m bo cung cp in an ton, n nh, tin cy v m bo cht lng in
nng,
Trung tm iu h thng in Quc gia (A0) nghin cu v phi hp vi cc n v
lin
quan trong vic ra cc gii php phng trnh mt in din rng. Cc gii php
ny c
thit k da trn cc nhm nguyn nhn sau:
Mt n nh tn s do s c mt mt/ mt nhm cc t my hoc do s c gy mt
lin
kt h thng in;
S c ng dy, my bin p 500, 220 kV quan trng;
Phng chng in p thp v sp in p.
Trn c s cc h thng bo v, mch lin ng c s dng:
(1) H thng sa thi theo tn s thp (F81);
(2) H thng sa thi ph ti c bit b sung;
(3) Cc mch sa thi ngun; hiu chnh sa thi t my min Bc;
(4) Cc mch sa thi c bit khi s c 1 phn t ng dy/ my bin p quan
trng;
(5) Cc mch sa thi ph ti theo in p ti Ph Lm, Tn nh v mt s trm 220
kV min
Nam.
Cc mch sa thi trn ng vai tr quan trng trong cng tc vn hnh h thng
in, phng
chng mt in din rng. Tuy nhin, do cu hnh h thng in thng xuyn thay
i, nn cc
mch trn cn thng xuyn c cp nht, hiu chnh cho ph hp.
4. S CN THIT PHI TRANG B H THNG BO V CHNG MT IN
DIN RNG
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HI NGH KHOA HC V CNG NGH IN LC TON QUC 2014
6
Cng tc vn hnh cho thy rng, c th kp thi a ra cc lnh iu ph hp nhm
ngn
chn cc s c mt in din rng, nhn vin vn hnh cn c trang b cc cng c
mnh
phn tch, a ra c cc cnh bo nhanh chng, chnh xc v tnh trng vn hnh
ca h
thng in trong h thi gian thc. Thm ch, h thng in cn c trang b cc
bo v
thc hin mt lot cc hnh ng t ng trc khi h thng b tch ra hoc phn
chia theo cch
thc c th kim sot c.
Cc s c din rng c th xy ra khi h thng vn hnh ch bin, xut pht t mt
hoc
mt vi phn t b tch ra khi vn hnh v gy phn ng dy chuyn dn n vic mt
lot cc
phn t b tch ra khi vn hnh. Trong khi , nhc im ln ca cc h thng iu
khin v
gim st truyn thng l khng cung cp c cc hnh nh mang tnh ng ca h
thng ngha
l cc nhn vin vn hnh khng c c bc tranh tng th xem ci g ang din ra
trn h
thng. Hn na s c mt in din rng c th xut hin v din bin trong thi
gian ngn, m
bn thn ngi vn hnh khng th kp a ra cc phn tch hay tnh ton nhm a
ra c cc
quyt nh hp l. Cc mch sa thi & lin ng hin hu trong trng hp tc
ng ng s c
tc dng phng trnh s c lan rng. Tuy nhin, cc mch ny c thit k cho
nhng trng
hp c th v c th khng t hiu qu mong mun khi cu hnh h thng thay
i.
H thng o lng, gim st v bo v din rng khai thc cc tin b mi nht
trong cc k
thut v cm bin, truyn thng, my tnh, thut ton v c bit l cng ngh o
lng c
ng b ha. S xut hin ca cc thit b o gc pha c ng b ha (Phasor
Measurement
Unit) lm nn cuc cch mng ton din trong lnh vc gim st, iu khin v
bo v h
thng in.
Theo nh ngha ca IEEE th thit b o gc pha Phasor Measurement Unit
(PMU) l thit
b c kh nng ng b gc pha, tn s v tc thay i ca tn s thng qua vic o
cc tn
hiu in p v/hoc dng in v tn hiu ng b thi gian. Thit b PMU c th
thc hin cc
chc nng khc v c t tn theo cc chc nng ny (v d: nu thit b PMU c kh
nng
ghi li dng sng ca cc tn hiu o s c gi l thit b ghi s c).
Thit b PMU rt ph hp theo di cc trng thi ca h thng in trong thi
gian thc.
PMU c s tin b ng k so vi h thng SCADA/EMS, trong khi h thng
SCADA/EMS l
h thng c tc cp nht t vi giy n vi pht, ch o cc gi tr RMS ch khng
o cc
gi tr gc pha th PMU thng c tc cp nht cao (thng khong 10; 25; 50
gi tr o/s do
ngi dng ty chn), mi gi tr o c dn nhn thi gian c ng b ha vi
chnh
xc cao thng qua h thng GPS v c th o c cc gi tr pha (bin v gc
pha) ca
dng in v in p.
Gc pha ca in p v/hoc dng in t nhiu im o trn h thng in khi c ng
b
thi gian thc c th gip nh gi tnh trng vn hnh ca h thng in mt cch
tin cy v
chnh xc. Nhng thng tin v gc pha ny c th c s dng cho vic gim st h
thng in
din rng (WAMs).
Ngy nay, vic o gc pha ng b c ng dng ch yu cho vic xc thc cc m
hnh ho
h thng in, phn tch sau s c, hin th thi gian thc... v ha hn s ngy
cng c vai tr
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A. Cc bo co chung
7
quan trng trong vic nng cao tin cy, n nh v tnh kinh t ca h thng
in thng qua
vic iu khin v trang b phng thc bo v thi gian thc.
PMU: Phasor measurement unit; PDC: Phasor Data Concentrator
Hnh 2. Cu trc mt h thng gim st bo v v iu khin din rng
vi thit b o gc pha (PMU)
PMU c mt s ng dng c th nh sau:
o lng v gim st h thng in din rng phc v bo v chng mt in din
rng;
Gim st v iu khin thi gian thc: gip cho cc nhn vin vn hnh nm bt
mt cch
trc tuyn v ch vn hnh ca h thng;
nh gi v a ra cc cnh bo v tnh trng vn hnh ca h thng in;
Gim st n nh in p v n nh qu ;
H tr cng tc phc hi h thng...
Nh phn tch trn, h thng in 500 kV Vit Nam hin nay v nhng nm tip
theo
thng truyn ti mt lng cng sut ln t h thng in min Bc, Trung vo min
Nam.
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HI NGH KHOA HC V CNG NGH IN LC TON QUC 2014
8
Trong mt s ch vn hnh cc oan, nguy c xy ra mt n nh l rt cao (v d
s c ngy
26/04/2013 gy nhy ng dy mch kp H Tnh - Nng sau khi 06 t b dc ti
H Tnh
v Nho Quan b Bypass). Vic trang b cc b PMU (hoc cc b ghi s c c
chc nng o
ng b gc pha) tng bc trin khai, khai thc cc tnh nng ca PMU nh tnh
nng cnh
bo tnh trng vn hnh ca h thng in s gip cho ngi vn hnh c c nhng
phn ng
kp thi v hiu qu
Hn na, theo l trnh trin khai xy dng h thng li in thng minh
(Smart Grid) ti Vit
Nam c Chnh ph ph duyt (Quyt nh s 1670/Q-TTg ngy 08/11/2012 v vic
Ph
duyt n pht trin Li in Thng minh ti Vit Nam) th trong giai on
2012 - 2016 s:
Trin khai cc ng dng nhm tng cng tin cy, ti u vn hnh li in truyn
ti, li
in phn phi, gim tn tht in nng; tng cng h thng ghi s c, h thng
pht hin v
chng s c mt in din rng nhm m bo truyn ti an ton trn h thng in
500kV. Do
, vic trang b cc b o gc pha cng l bc quan trng chun b c s h tng
cho vic p
ng l trnh trin khai li in thng minh Vit Nam.
TI LIU THAM KHO
[1] Tng kt vn hnh h thng in quc gia nm 2013.
[2] Bo co nh gi trnh hnh cung cp in giai on 2014-2020.
[3] Bo co vn hnh li in quc gia nm 2014.
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A. Cc bo co chung
9
[1]