E] KHOA HQC - CdNG N 6 H |
NGHICN cim UNH HITIUNG CUA HC TH6NG N6I D/^T utn QUA DlCN AP VA QUA UONG D I I N KHI Sif Cd CHAM ukl TRONG
lirOl DICN PHAN P H 6 | 22 KV 3 pha 3 dfty Vi 3 pha 4 m
Nguyin Luang Mfnh, V6 NhUQutic rdng Cdng ty Oiin li/c miin Trung
TOMTAT
LUdl d l | n phdn phdi (LDPP) 22 kV khu vpc m l l n Trung h l | n dang vdn hdnh vdi d^ng cdu true 3 pha - 3 ddy, bdn kfnh cdp d i l n ddi hdng chye klldmlt {ed m^t sd dudng ddy ddi t r i n 50 km). Qua thuc t l vdn hdnh, dd xdy ra n h i l u trudng hpp khi cham ddt m^t pha (CDMP) gdy qud dl^n dp 6 cdc pha khdng cham ddt vd qud ddng d l | n d pha bj ch^m ddt qud mPc chju dpng eiia t h i l t bl. Oi h^n c h i dnh hUdng cua loai sped ndy din t h i l t bj, cdn quan tdm d i n h l | n tUpng qud d i | n dp vd qud ddng d l | n khi xdy ra sped cham ddt t r i n ludi trong vi|c tfnh chpn t h i l t bj d i | n . Bdi bdo n g h i l n cCfu dnh hudng ciia h | thdng ndi ddt d i n mCfc dO qud dl$n dp vd qud ddng d l | n khi sp cd cham ddt trong LDPP 22 kV ddi vdi 2 dang cdu trOc lUdl 3 pha 3 ddy vd 3 pha 4 ddy, d l cd Ofng dpng h l l u qud vdo thpc t l .
\. Dit vin dt:
LDPP 22 kV cd trung tfnh n6l ddt true tiep, khi cham ddt dupe xem Id dang su cd ngdn mach n i n phdi dUOc each ly vdi thdl gian ngdn nhdt. Trong khodng thdl gtan tP khi su cd xudt h i l n cho d i n khi sp c6 dupe ed ldp, cde t h i l t bj t r i n ludi d i l n se chju tac ddng eiia qud ddng d i l n d pha bj sp ed vd qud d i l n dp d pha khdng sp c6. MPc tang cao d i l n dp vd ddng d i l n phu thudc vdo tinh chdt noi dat ciia lUdi d i l n (ndi dat hieu qud hay khdng h l l u qud), dUdc phdn dnh qua ty sd d i l n khdng t h P t p khdng (TTK) X^ vd dien khdng thPtpthudn (TTT) X,.ThUc t l , khi thiet ke LDPP 22 kV d Vilt Nam thi cde vdn d l ndy ehUa dUde quan tdm diing mpe, nhdt Id h i sd qud d i l n dp vd ed t h i se ddn den viec chpn Ipa cde t h i l t bj d i l n khdng phii hpp vdi dac tinh ciia ludi d i l n .
2. Quan h i giiifa t i n h chlCt n6i dit cua h i thdng den dong dien vd dien dp khi c6 sU co cham ddt:
Xet LOPP 22 kV nhU hinh 1, khi xdy ra sped cham ddt d cudi dudng day tai d i l m N, Ddng d i l n vd d i l n dp eiia cac pha khi xdy ra CDMP vd cham dat hai pha dUdc tfnh toan [4]:
- Khi ngdn mach mdt pha (NMMP) N"' d pha A:
Dong dien ngdn mach (DONM) ciia pha A chfnh Id ddng dien chay qua diem trung tfnh.
I N = IN, 3E
Lfltni) I lOkV 22k\'
($>\m\—
Hinh 1. So dd don g i i n LOPP 22kV H i s6 q u i dl«n i p khi x i y ra NMMP,
1 ''•-I
] ^•
1 X,
r^^--.
1 , X, '
1 ' , l ^ -
l l X,
'
1fx, ,)
\
L X, J
• Khi ngdn mach hai pha cham ddt N " d pha B va phaC:
Ddng d i l n chay qua d i l m trung tfnh chfnh Id ddng ngdn mach 2 pha cham ddt I " ".
K = I N B + I N C = — ;— (3)
2X„+Xi He d qud d i l n dp khi cd ngdn
'•' X,
Quan he glQa 1^'
IN"
' 2 X . + X,
" 2 X i + Xo 3 X ,
X , X ,
'vil„"",
2 ^ . 1 X, 2 . ^
mach ha pha cham ddt,
(4)
(5)
12 Wen Jk Bin song
l"
s''
H -
' o i , 0^
°'°o
•f
^ !^ (i
-•j^
L>
*
f
'
1 -
.-
r-
^
— ^
—Ce(l,l -.-iNliyiNd.ii
Hinh 2. Quan h i giOa Ced), Ce(l ,1), IN(1,1 )/IN(l) theo X0/X1
TO (2), (4) v i (5) c6 t h i b i l u dien quan h? giffa cic he s6 C j " , C ^ ' " v i l„"'/l„"'" theo ty s6 X,/X, nhir hinh 2.
Cac dudng dac tinh C^", C [ ' " va I J ' V I , " " cCing giao nhau tai diem co — ^ = L r i i n g duOng dac tinh C ' , C ' con
^'^ X giao nhau tai diem e d — - = 4,5.
TP hinh 2, nhan thdy:
+ Khi < 3 (he thong noi dat ta hieu qua), tat nhPng d i l m ngdn mach cham dat cd t^ sd — - < 1 thi
? ^ < 1 nen ddng I J ' " nguy hiem hdn ddng IJ", va C ' T(l.l)
> Cg nghia Id qua dien dp khi NMMP nguy hiem hon khi ngan mach 2 pha cham ddt. Tai nhPng diem ngdn mach
X I ' "
cham dat cd t j ' sd 1 < - — ^ 3 thi ^ > 1 luc nay ddng
" 1 ^N
KHOA HQC - CONG NGHf: \3
1^"' nguy h i l m hon ddng I , " " , vd € * ' • ' * > C^'* nghia Id qud d l | n dp khi ngdn mach 2 pha cham ddt nguy h i l m hon khi NMMP.
+ Khi — ^ > 3 (h§ thdng ndi ddt khdng h i i u qud) thi 'N'" ^ V ' " ' ^^' nhCmg d i l m ngdn mach cham ddt cd t^ sd 3 < — ^ < 4,5 thi C^'''*> C ^ " n i n qud d i l n dp khi ngdn mach 2 pha cham ddt nguy h i l m hon khi NMMR Cdn tai nhOng d i l m ngdn mach cham ddt cd ty sd — ^ > 4,5 thi
^ 1 C j " > C^''"' do vdy qud d i l n dp khi NMMP nguy h i l m hon khi ngdn mach 2 pha cham ddt
3. Cdc yiu ti dnh hifdmg d i n tfnh chat ncfi d&t cua h i thdng:
3.7. Tifng trd'ccia (Tu'dhg ddy trin Jr/iong: Tdng trd eiia dudng day tren khong (DDK) phu thudc vdo nhieu y l u td nhu t i l t d i l n day, vat lieu, khodng each pha, cdu true ddy dan, loai lUdi dien, dp cao treo day, n h i l t dp ddy ddn va d i l n trd suat ciia dat. D l tinh tong trd cua DDK cd the dung phuong phdp gidi tfch [1] hoac bang cdch tra bdng.
Phuong phdp dung bang tra nhu sau [5]: Tdng trd dudng day da cho trong bang dUoe tfnh theo cac yeu td nhat djnh nhu khodng each pha, n h i l t dp day dan, d i l n trd suat eua dat... Do dd, dp chinh xdc phu thudc vdo su sai lech gida yeu td thpc te so vdi cac dieu kiln tfnh toan d bdng tra. Yeu td ed dnh hudng Idn d i n do chinh xac la khodng each pha. Tong trd TTT va TTN phu thudc vao khodng each pha va diioc hieu chinh theo khodng each trung binh hinh hpc D^ giPa cdc pha:
D,b=VdA-BdA-cdB. [ml (6)
vdi d^g, d ^ ^ dg J.- ((hoing each thuc te giCra pha A - B, A - C va B • C.
1000 , 1000 , I 1200 , 1000
^ f. ^
D „ = V l O O O . 1000. 2000 D,^=Vl200.1000. 2200 D,^ = VlOOO. 1000.1400
= 1260 m m = 4,132 ft. = 1382 mm = 4,533 ft. =1119 mm = 3,669 ft.
Hinh 3. Khodng cdch trung b'mh hinh hoc cua dudng day 22 kV
Oien & Oai songl 13
El KHOA HQC • CdNG N G H | ;
Diy pha
Bingl. Ting tri cdc thinh phdn HSIxOng da ODK22 ItV o f II
a f II
x"
^ «r <
X
i
Diy trung tfnh a/kmlo f x "
< ^
Diy ddng C-50(1/0)
C-70 (2/0) C-95 (3/0) C-120(4/0) C-150(300)
0,377 0,299 0,237
0,188
0,134 0,444 0,435 0,418 0,413 0,400
0,555 0,477 0,415 0,366 0,311
1,901 1,893 1,877 1,872 1,859
4,3 4,4 4,5 4,5 4,6
1,3 1,1 1,0 0,9 0,8
C-35(2) C-35(2]
C-50(1/0) C-35(2) C-50(1/0) C-35 (2) C-70 (2/0) C-50(l/0)
0,764 0,685 0,542 0,624 0,494 0,575 0,399 0,440
1,323 1,315 1,203 1,298 1,198 1,256 1,152 1,186
3,0 3,0 2,9 3,1 2,9 3,0 2,9 3,0
1,7 1,6 1,3 1,5 1,2 1,4 1,0 1,1 Diy nhOm
A-50(l/0) A-70 (2/0) A-95 (3/0) A-120(4/0) A-150(300) A-185(350)
0,605 0,481 0,380 0,302 0,213 0,183
0,441 0,431 0,419 0,410 0,400 0,393
0.783 0,659 0,559 0,480 0,391 0,357
1,899 1,889 1,877 1,872 1,858 1,851
4,3 4,4 4,5 4,6 4 6 4 7
1,8 1,5 1,3 1,2 1,0 0,9
A-35 (2) A-35 (2) A-50(1/0) A-35 (21 A-50(l/0) A-35 (2) A-70 (2/0) A-50(1/0) A-9S (3/0) A-70 (2/0)
1,058 0,934 0,783 0,834 0,705 0,755 0,575 0,616 0,501 0,544
1,471 1,460 1,299 1,448 1,291 1,440 1,220 1,280 1,163 1,213
3,3 3,4 3,1 3,5 3,1 3,5 3,1 3,2 3,0 3,1
2,4 2,2 1,9 2,0 1,7 1,8 1,4 1,5 1,3 1,4 Diy nhom ioi t h i p
AC-5Q(1/0) AC-70 (2/01 AC-95 (3/01 AC-120(4/0) AC-150(300) AC-185(350)
0,696 0,556 0,449 0,368 0,213 0,190
0,512 0,503 0,490 0,466 0,389 0,385
0,374 0,734 0,627 0,546 0,390 0,368
2,086 2,077 2,064 2,039 1,963 1,959
4,1 4,1 4,2 4,4 5,0 5,1
1,7 1,5 1,3 1,2 1,0 1.0
AC-35 (2) AC-35 (2) AC-50(l/0) AC-35 (2) AC-50(1/0) AC-35 (2) AC-70 (2/0) AC-50(1/0) AC-95 (3/0) AC-70 (2/0)
1,131 0,991 0,844 0,885 0,762 0,803 0,572 0,608 0,547 0,549
1,573 1,563 1,433 1,551 1,409 1,526 1,271 1,332 1,219 1,266
3,1 3,1 2,9 3,2 3,0 3,3 3,3 3,4 3,2 3,3
2,2 2,0 1,7 1,8 1,6 1,7 1,5 1,6 1,4 1,4 Tinh vdi: Khodng cdch trung binh hinh hqc giUa c6cphaD^^= I25m; W/iiir d6 ddy ddn t = S0°O Khodng cdch pha •ddtd=
h22m;Di^ntrdsudtcuaddtp^^=lCKinm.
Ghi chu: So hieu trong ngodc Id ioqi ddy ddn tuang di/ang theo AWC, tinh theo Kcmil
Sai so ve i(hoing cich pha giOa g i i tri cho trudc 6 b i n g tra vdi thuc t i den 50% cd t h ^ d i n d i n sai so cua tdng trd d mufc (0,2 -^ 8,8)% [2]. Oiiu nay i n h hudng den sai s6 DONM, nhung thudng Ithong Idn so vdi phUdng p h i p giii tich.
Ap dung phuong phap tra b i n g de tinh toan tong trd DDK trong LOPP 22 l<V vdi c i u true 3 pha 3 d i y va 3 pha 4 day cho cac loai day dan dong (C), day nhdm (A) v i day nhom Idi thep (AC) duoc bd tri nhu hinh 3.
Co the lay gia tri trung blnh ciia D^^ = 1.254 mm = 4,11ft; de tinh cho trudng hop tong q u i t ciia DDK 22 l<V. Kit qua tinh toan tdng trd cua DDK 22 kV duoc trinh b i y d b i n g 1.
TO b i n g 1 cho thay, tdng trd TTT chi phu thuoc cau true va d i e tinh eua day pha. Viic co hoac I<h6ng eo day trung tinh cung nhu each noi dat lap lai cua day trung tinh trong da so cic trudng hdp cua DDK i n h hudng khdng dang ke den tdng trdTTT.Tuy nhiin, cie yeu td nay lai i n h hudng Idn den tdng trd TTK. Tdng trd TTK se g i i m d i n g ke khi dudng day 3 pha 3 day duoc k i o them day trung tinh cd ndi dat lap lai.
3.2. Moi quan hi giaa cic ty so R y X ^ X ^ , va chieu dii duing day vii cic ciu trie lUH khac nhau: Bilu dien ket q u i tinh toan mdi quan he gida ty sd R/X,,X/X, va chieu d i i dudng day vdi tCing dang cau true ludi khic nhau nhd ludi
14 Oien & Oai song
dien d hinh 1 theo dd thj t d hinh 4 d i n hinh 11 (kit q u i tinh t o i n DDNM v i cie t i sd R/X,, X,/X, duoe thi;c hi^n t r i n chUdng trinh tinh t o i n n g i n mach PSS/ADEPT [3]).
Vdi cau true 3 pha 3 d i y v i 3 pha 4 d i y cua DDK ed d i y pha AC-95, d i y trung tinh ed t i i t d i | n thay ddi v i di^n trd suit eCia d i t p,„ = 100 Om, thi ty sd R/X,, X/X, v i chilu d i i dudng day dUdc b i l u d i i n theo d6 thj hinh 4 v i hinh 5,
HDU'
m
.400
200
m
600
JOO
non
t//
ll
' 0 014
«
V
=
"
y^
I s
?
=
$
X
_
- 1
-
'
?
- ^
7
"T
^
"1
KHOA HQC - CdNG N G H | : Q
gidm dl^n khdng TTK nhung khdng dnh hudng d i n dien khdng TTT, n i n Idm cho t^ sd Xyx, gidm di. Ngupc lai, ddy trung tfnh Idm tdng d l | n trd TTK n i n cung Idm cho t;J' so RyX, tdng I l n . Khi t i l t di^n ddy trung tfnh cdng Idn thi cdc t i ' s 6 R y x , v d X y x , cdng gidm.
Vdi cdu true 3 pha 3 ddy vd 3 pha 4 ddy eiia DDK ed ddy pha AC-185, ddy trung tfnh ed t i l t d i l n thay ddi vd di§n trd sudt eiia ddt p^„ = 100 Om, thi t^ sd R/X,, X/X, vd chilu ddi dudng ddy dupe b i l u d i l n theo dd thj hinh 6 vd hinh 7.
0 5 10 15 ZO Z5 » JS 40 45 SO L(Kiii)
Hinh 4.Ty sd RO/Xl theo chieu dai DDK khi pdat = 100 Om
I.2D0
1000
0800
0600
0400
0 300
1=
foOH
?
y Yl
I >
o
I
0
:
^
i'•>
"
S
-4-
%
^ 7 *
- i
- ^ ] A C - l « S -•-3AC-18S(IAC-I20 -•-3AC-18StlAC-l50 ->-3AC-l8S^^IAC-l8i
0 5 10 15 20 15 30 35 40 (5 50 L ( K D I )
Hinh 6.J^ sd RO/Xl theo ehieu dai DDK khi pdat = 100 Om
Hinh S.Ty sd XO/Xl theo chilu dai DDK khi p d l t = 100 Tphinh4va hinh 5 nhdn thay:
-Ty so Rp/X| phu thudc vao vat lilu ddn d i l n , edn ty so X/X, chu yeu phu thudc vao kfch thudc hinh hoc cua day dan.
- LDPP 22 kV vdi cau trpc 3 pha 3 day, mac dii trung tinh eua may bien dp ngudn 22 kV ed ndi dat true tiep nhUng ndi dat hieu qud van khong ddm bdo do R/X, > 1 khi chieu dai dudng day tren 20 km va X/X, > 3 khi chilu dai dudng day tren 10 km.
- Doi vdi cau true 3 pha 4 ddy, day trung tinh se lam
0 i 10 15 20 25 30 35 40 4S SO K K m l
Hinh 7.J^ sd XO/Xl theo chieu dai DDK khi pdat = 100 Om Tir hinh 6 va hinh 7 nhan thay: Khi t i l t d i l n day dan pha tang len thi vdi cdu true 3 pha 3 day, ty sd R/X, giam nhieu (R^/X, < 1 khi L = 50 km) nhung t^ sd X/X, lai tang nhanh (X/X, > 3 khi L s 10km), do vay tinh hieu qud eiia c h i dp ndi dat giam theo chieu dai dudng day. Cdn vdi cau true 3 pha 4 day, khi cd day trung tinh thi ty sd R^/X, tang rat ft (R/X, > 1 khi L > 25 km ddi vdi day trung tinh AC-120)
Dien Jk D&i songl 15
E] KHOA HQC - CdNG NGH^
v i t^ sd n i y c i n g g l i m khi t i l t di^n d i y trung tinh c i n g t i n g , cdn t j sd X/X, g l i m r i t n h l i u (X/X, < 3 khi L > 50 km ddi vdi d i y trung t(nh AC-120) v i t;> sd n i y g l i m khdng d i n g k l khi t i n g t i l t d i f n d i y trung tinh.
3.3. Mdi quan h^ glOla cic t) i<i RO/Xl, XO/Xl v i chilu d i i dirfng d t y vAI cic cfu triic liMi khic nhau khi dlfn trA suit cit d i t thay d<h Khi dl$n trd suit cilia d i t thay ddi, vdl c i u trOc 3 pha 3 d i y cCia DDK c6 d i y pha AC-95 v i AC-185, thi ty sd RO/Xl, XO/Xl v i chilu d i i dudng d i y ddi^c b i l u d i l n theo dd th| hinh 8,9,10 v i 11.
Hinh 8. Ty sd R/X, theo chieu d i i DDK 3AC-95 5
Hinh 9. Ty sd X/X, theo chieu d i i DDK 3AC-95
16 Oien A Hot' soing
Hinh 10. T^sdRyX, theo c h i l u d i i DDK 3AC-185
Hinh 1 1 . Ty sd X / X , theo chieu d i i DDK 3AC-185 Qua eie hinh 8, 9, 10, v i 11 nhan thay: Khi diin trd suit eua d i t c i n g tang thi cac ty sd Ryx, v i xyX, cung tang theo, trong do ty sd R/X, tang khdng d i n g k l , con t^ sd X/X, tang theo ty le k h i deu nhau m i h o i n toin khdng phu thude vao t l i t d i i n d i y pha. Vdi cung mdt tiet d i i n d i y d i n , c i u true LfiPP 22 kV 3 pha 3 d i y d nhflng khu VUC cd dien trd suit eua d i t c i n g Idn thi tinh ndi dat h i i u q u i cang g i i m , do vay l i m g i i m b i n kinh cap diin hieu q u i cua ludi d i i n .
KHOA HQC - CONG N G H I Q
4. K^t q u i tfnh q u i dien i p v i q u i ddng diln vdl cic cllu triic ludi khic nhau:
TCr k i t q u i tinh t o i n DDNM t?l t i t c i cic nut ciia DDK ed chieu d i i 50 km vdl cic dang c i u triic ludi khic nhau (nhd mue 3.2), theo (2) v i (4) tinh dU(?c eie h i sd qua d i i n i p khi kiy ra NMMP (C,"') v i n g i n m?ch 2 pha (C,""). Bing 2 t h i hl^n tdng hop cic t l sd X/X,, cie h i sd C,"', C,"": v i ddng d i i n SU cd cham d i t 1^^ cCia 2 dang c i u true lUdi 3 pha 3 d i y (3AC-95) v i 3 pha 4 d i y (3AC-95-H AC-50) khi d l | n trd suit cuadatp„j, = lOOnm,
Bing 2. Qui diin ip vi qui ddng dtin vii cic du trie lu^ Ithic nhau
L (km)
0 5 10 15 20 25 30 35 4 0 45 50
NOt
NODEl N0DE2 N0DE3 N0DE4 N0DE5 N0DE6 NODE?
NODES N0DE9 NODE10 NODEl 1
X„/X, 0,278 2,170 2,841 3,181 3,383 3,516 3,607 3,673 3,722 3,758 3,786
3 pha Clt) (pu) 0,885 1,166 1,235 1,264 1,280 1,290 1,297 1,301 1,305 1,307 1,309
3 ddy C "•"
(pu) 0,537 1,219 1,276 1,296 1.307 1,313 1,317 1,320 1,322 1,324 1,325
(%l^') 131,918
74,716 66,572 63,462 61,853 60,886 60,252 59,812 59,495 59,262 59,088
3 pha 4 ddy X / X ,
0,278 1,574 2,033 2.265 2,403 2,493 2,556 2,601 2,634 2,659 2,677
c m (pu) 0,885 1,089 1,150 1,177 1,192 1,201 1,208 1,212 1,215 1.218 1.220
C "•"
(pu) 0,537 1,138 1,204 1,229 1,242 1,249 1,255 1,258 1,261 1,263 1,264
131,918 83,214 75,012 71,809 70,138 69,130 68,469 68,011 67,683 67,443 67,266 Qua k i t qud tinh toan eac sd lieu nhu bdng 2 ta thdy:
+ T6ng trd eiia DDK phu thudc vao nhilu yeu td nhu tiet dien day, khodng cdch pha, cau true day dan, loai ludi dien, do cao treo day, nhiet dd day dan va dien trd suat cua dat; do vdy gay dnh hudng d i n k i t qud tfnh cdc he sd C^'", C^"-".
+ Tai ciing mdt diem ngdn mach cham dat (nut N0DE4 each nguon 15 km), vdi cau true lUdi 3 pha 3 day ed CJ'-"-^'-" = 1,296 pu > 1,229 pu = CJ'-'i-^f-w cua cau true ludi 3 pha 4 day. Hon nda, khi cd ngdn mach cham ddt eudi dudng day (niit NODEl 1 each ngudn 50 km) thi vdi cdu true ludi 3 pha 4 day ed c^fi'-^'-^ = i,264 pu van nhd hon c^u'wid cCia cau true ludi 3 pha 3 day khi cd ngdn mach cham dat tai diem each ngudn 15 km. Do vdy, vdi cau true ludi 3 pha 4 day se ddm bdo tinh kinh te ciia mang nhd chpn cdc t h i l t bj dien cd he so qua dp tam thdi be.
+ Doi vdi ludi 3 pha 3 day thi ddng d i l n cham ddt 1^^ > 60% l^j"' khi d i l m ngdn mach each nguon <, 30 km. Vdi iudi 3 pha 4 day thi ddng d i l n cham dat 1^^, > 60% 1^"' khi diem ngdn mach d cudi dUdng ddy each ngudn den 50 km. Do vay, vdi cdu triic ludi 3 pha 4 day bdo v l ro le lam vile tin cay hon khi sp cd NMMR
5. Ket luin:
He thdng ndi dat la hieu qud hay khdng hieu qud s i dnh hudng den qud dien ap va qua dong dien khi cd sU cd cham ddt t r i n ludi d i l n . Tfnh hieu qua cua e h l dp ndi dat khdng nhiJfng phu thude vdo vile ndi dat trung tinh tai nguon ma edn phu thudc vao tong trd eiia DDK, vao ty I I X^/X, tai diem ngdn mach ma mPc do tang cao ciia dien ap va ddng dien se thay ddi.
Trong tinh toan DDNM va cde ti so RyX|, x y x , theo chilu ddi dudng day vdi cdc dang cau true ludi, khi day trung tfnh bd tri cung vdi cac ddy pha tren mat phdng nam ngang, khi eac day pha va day trung tfnh bd trf t r i n mat phang thdng dijfng, va khi thay ddi do cao ciia DDK. Ket qud tfnh toan cho thay, anh hudng eiia cdch bd tri day dan va dp cao ciia DDK 22 kV den cac ty so R/X,, X/X, la khdng dang ke,
do vdy d l tfnh todn tfnh ndi ddt h i i u qud thi trong tfnh todn cho cdc ddy ddn pha bd trf t r i n mdt phdng ndm ngang vd ddy trung tfnh bd trf phfa dUdl cdc ddy pha, vdi cdc elu triic 3 pha 3 ddy va 3 pha 4 day d so dd cdt 10,5 m i t thi k i t qud tfnh todn cho tuong ddi chfnh xdc.
Vdi edu trde lUdi 3 pha 3 day tuy cd trung tfnh ndi ddt trpc tiep, nhung khi h i thdng ndi ddt khdng hi|u qud (X/X, > 3) thi khdng dat hiiu qud gidm qud d i l n dp, cde h^ sd qud d i l n dp C^", CJ'" cdng tdng khi tl sd Xyx, cang tdng. Cd 2 dang edu trPc ludi 3 pha 3 ddy vd 3 pha 4 ddy d i u ed he sd qua dien dp C^ s 2 pu.
Tai nhiJrng d i l m ngdn mach t r i n dudng ddy ed tl sd X/X, < 1 thi ed 2 dang edu true ludi 3 pha 3 day va 3 pha 4 day d i u ed C^'"
> CJ'", do vdy qud dien dp d cdc pha lanh khi xdy ra NMMP nguy h i l m hon. NhUng khi ngdn mach tai nhCfng diem t r i n dudng day cd ti sd Xg/X, > 1 thi cd 2 dang cau true lUdi cung deu ed C " "
> C^"', do vay qud dien dp d cac pha lanh khi xdy ra ngan mach 2 pha cham ddt nguy hiem hdn.
TAI U | U THAM K H A O [IJ Central Station Engineers of the Westinghouse Electric Corporation {1970), Electrical Transmission and Distribution Reference Book, East Pittsburgh, Pennsylvania.
[2] Cooper Power Systems (1990), Electrical Distribution System Protection - Third edition, USA.
[3] ShawPowerTechnologies_
Inc (2004). PSS-ADEPT__User Manual, New York.
[4] Richard RDeper(l 996), Ngiiin mach trong h^ thong diin, Nha xuat bein khoa hocva ky thuat, Ha Noi.
[5] Nguyen Luang Minh (2007), 8do cdo chuyin de: Nghien ciiu anh hudng cua day trung tinh ludi dien 22 kV d che do lam viec KDX va ngdn mach 1 pha, £>k Nang.
