Zoom-Bi.com -- Chong Set Choduon Gday Va Tram Bietn AP 0621

7/27/2019 Zoom-Bi.com -- Chong Set Choduon Gday Va Tram Bietn AP 0621

1/99

1

n : Tnh ton thit k chng st cho ng

dy v trm bin p 110/22KV

H thng in l mt h thng quan trng ca h thng nng lng

Vit Nam v khng th thiu c trc cng cuc hin i ho, cng nghip

ho t nc. Do ngun in thng t xa ni tiu thin nng nn phi

chuyn qua cc trm bin p tng hoc gim in p. i vi nc ta l nc

c kh hu nhit i gi ma, m h thng in li ko di t Bc vo Nam do

phi i qua nhiu vng kh hu khc nhau c bit l nhng ni c m

cao, mt ging st nhiu. Thit hi do st gy ra cho ngnh in v nn

kinh t quc dn l rt ln.

V vy chng ta phi u t vo nghin cu, tm ra nhng gii php

chng st nh vo cc nh my, trm bin p, ng dy gim n mc

ti thiu thit hi do st gy ra cho nn kinh t. Vi yu cu nh vy, n

thit k ca em gm bn thuyt minh ny v km theo bn v thit k v bov chng st cho trm bin p 110/22/0,4KV v ng dy 110KV.

Do thi gian c hn nn vic thit k ca em khng trnh khi nhng

sai st, em mong c s ch bo gip ca cc thy c gio b mn h

thng in. ng thi em xin chn thnh cm n thy gio Nguyn nh

Thng tn tnh hng dn em hon thnh n thit k na v em cng

xin cm n cc thy c gio b mn quan tm ch bo, hng dn chng

em trong vic thit k n tt nghip.

Mt ln na em xin chn thnh cm n!

Ngy 29 thng 4 nm 2003Sinh vin thit k


2/99

2

on Vn Minh

CHNG MU

------o0o-----

TNH HNH GING ST VIT NAM V NH HNG CA NTI LI IN

ic nghin cu ging st v bin php chng st c lch s

lu di cng vi s pht trin ca ngnh in. Ngy nay

ngi ta tm ra c cc phng php, nhng h thng thit b v k thut

cao phng st nh mt cch hu hiu v an ton.

Tuy nhin mt , thi gian xy ra st nh khng th don c

trc nn vic nghin cu chng st l rt quan trng c bit l ngnh in .

I - TNH HNH GING ST VIT NAM.

- Theo ti KC - 03 - 07 vin Nng Lng, trong mt nm s ngy st

nh mim Bc khong t 70 - 100 ngy v s ln c ging t 150 - 300

ln. Vng c ging nhiu nht trn min Bc l khu vc: Mng Ci, Tin Yn

(Qung Ninh) hng nm c t 100 - 110 ngy ging st, thng 7 - 8 c th c

n 25 ngy ging trn mt thng.

- Mt s vng c a hnh chuyn tip gia cc vng ni v vng ng

bng, s ln ging cng n 200 ln/ 1 nm, vi s ngy cng n 100

ngy/nm. Ni t ging nht l Qung Bnh, hng nm ch c khong 80 ngy

ging. Xt v din bin ca ma ging trong nm, ma ging khng honton ng nht gia cc vng. Ni chung mim Bc ma ging tp trung t

thng 4 n thng 9, min Ty Bc tp trung khong t thng 5 n thng 8

trong nm.

V


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3

- Trn vng duyn hi Trung Bpha Bc n Qung Ngi l khu vc

tng i nhiu ging trong thng 4 n thng 8 s ngy ging xp x 10

ngy/thng. Thng nhiu nht l thng 5 c th t 12 n 15 ngy. Nhng

ngy u ma v cui ma ch c 2 n 5 ngy/ thng.

- T Bnh nh trvo l khu vc t ging nht thng ch c vo thng 5

vi s ngy xp x bng 10 ngy (Tuy ho: 10 ngy; Nha Trang 8 ngy; Phan

Thit: 13 ngy), cn cc thng khc ca ma ng ch quan st c t 5 n

7 ngy ging st.

- Min Nam cng c kh nhiu ging hng nm quan st c t 40 - 50

ngy tu tng ni. Khu vc nhiu nht l ng bng Nam B, s ngy ging

st c th ln ti 120 n 140 ngy. Ma ng Nam B t thng 4 nthng 11 s ngy ging trung bnh 10 ngy/thng cn t thng 5 n thng 10

c khong trn 20 ngy ging ( Si Gn: 22 ngy; H Tin: 28 ngy)

- Ty Nguyn ma dng thng ch c t cc thng 4,5 v thng 9. Thng

cc i (thng 5) trung bnh quan st c 15 ngy ging v Ty Nguyn

trung bnh s nga ging t 10 - 12 ngy(Ply cu: 17 ngy; Kon Tum: 14

ngy, Lt: 10 ngy) cn cc thng khc ca Ma ng trung bnh c t 5

n 7 ngy/thng.

- Qua s liu kho st ta thy rng trung bnh ging st 3 min Bc - Trung -

Nam, nhng vng ln cn li c mt tng i ging nhau. Kt qu nghin

cu ngi ta lp c bn - phn vng st Vit Nam (cc thng s cho

trong bng 1-1).

Bng 1-1:

VngNgy ging

trung bnh(ngy/nm)

Giging trungbnh(h/nm)

Mt sttrung bnh

Thngging cc

i

ngBngvenbin Mim Bc

81,1 215,6 6,47 8

Min ni trung 61,6 219,1 6,33 7


4/99

4

du Bc B.

Cao nguynMinTrung

47,6 216,21 3,31 5,8

Ven binMinTrung

40,0 95,2 3,55 5,8

ng BngMin Nam

60,1 89,32 5,37 5,9

- T cc s liu v ngy giging, s lng o lng nghin cu thc

hin qua cc giai on c th tnh ton a ra cc s liu d kin v mt

phng in xung cc khu vc (sliu dbo trong bng 1-2 ).

Bng 1-2:

S ngy

dng

ng bng

ven bin

Min ni

trung du Bc

B

Cao nguyn

min trung

Ven bin

min trung

ng bng

Min Nam

20 40 2,43 4,68 2,1 4,2 1,2 2,4 1,22 2,44 1,26 2,52

40 60 4,68 7,92 4,2 6,3 2,4 3,6 2,44 3,65 2,52 3,78

60 80 7,92 9,82 6,3 8,4 3,6 4,8 3,65 4,87 3,78 5,06

80 100 9,82 12,15 8,4 10,5 4,8 6,0 4,87 6,09 5,06 6,3

100 120 12,1514,58 10,5 12,6 6,0 7,2 6,09 7,31 6,3 7,76

II. SNH HNG CA GING ST TI H THNG IN:

- Vit Nam, trong khun kh ti cp nh nc KC - 03 - 07 lp t

cc thit b ghi st v b ghi tng hp trn cc ng dy ti in trong nhiu

nm lin tc, kt qu thu thp tnh hnh s c li in 220 KV min Bc t

nm 1987 n nm 1992 c ghi trong bng 3.- Trong tng hp s c vnh cu ca ng dy trn khng 220 KV Ph Li

- H ng, nguyn nhn do st l 8/11 chim 72,7%. Sdly kt qu s c

ca ng dy Ph Li - H ng lm kt qu chung cho s c li nh

Min Bc v y l ng dy quan trng ca Min Bc v s cng dy


5/99

5

ny nh hng rt ln n tnh hnh truyn ti in nng trn li in. Ngoi

ra theo ti nghin cu khoa hc - nghin cu gii php k thut hon thin

h thng chng st bo v li in trung p ca Vin Nng Lng tp

trung thng k, phn bit tnh hnh s c li in 35 n 110 KV ca Min

Bc ni chung v li in quc gia ni ring t nm 1976 n nm 1982.

Kt qu thng k c th hin bng 1- 3.

Bng 1- 3:

NmDi 220 KV ng dy Ph Li - H ng

Tng s Vnh cu Tng s Vnh cu Do st

1987

1988

1989

1990

1991

1992

2

5

24

25

30

19

1

2

3

4

2

1

2

5

6

2

3

4

1

2

2

1

1

4

1

1

1

1

1

3

Tng s 105 16 22 11 8

- T thng k ny cho ta thy rng: Tng s c do st gy ra i vi ng

dy trung p l ln hn tng s ca ng dy cao p, nhng tc hi ca n

mang li i vi h thng in l rt ln. S ln s c li in 35KV chim

t l kh ln n 54%.

Bng 1- 4:

Nm theo di Cp in p KVTng chiu di

ng dy (Km)

Sut s c (ln /100Km)

Tng s Do st

1979110

35

1050

3400

8,5

11,5

1,85

6,00

1980110

35

1100

3400

6,8

10,7

1,46

5,40

1981 110 1150 5,6 2,50


6/99

6

35 3800 7,7 1,20

1982110

35

3300

11200

6,9

10,8

2,50

5,10

*Kt lun: Qua nghin c tnh hnh ging st Vit Nam v nhng thit

hi do s gy ra cho li in l rt ln nn vic m bo chng st cho ngdy in v trm bin p l rt cn thit nhm gim n mc thp nht s c ct

in ng dy. V vy vic u t nghin cu chng st l rt quan trng

nng cao tin cy cung cp in v trong vn hnh li in quc gia.

CHNG I

------o0o-----

TNH TON TRNG ST NH TRCTIP VO TRM BIN P

rong h thng in (HT), trm bin p (TBA) ng vai tr

quan trng. N quyt nh rt ln v tin cy cung cp

in ca ton HT v mt yu t quan trng dn n s mt n nh ca

HT trong nhiu yu t l do sng st qu in p truyn vo trm tng

dy v do st nh trc tip vo trm.

- Qua thng k, ngi ta thy s ln s c ca HT do b st nh chim t

l rt ln so vi cc trng hp khc. V vy vic tnh ton bo v TBA do st

nh hn mc ti thiu l mt nhim v ht sc quan trng v cn thit.

Khi b st nh vo trm, cc thit bin s b h hng v c th dn n

vic cung cp in b ngng ton b , ng thi c th lm nh hng trc

tip n qu trnh sn xut in nng v cc ngnh kinh t khc.

- m bo chng st nh trc tip vo trm cn dng cc ct thu st vdy chng st. Cc ct thu st ny c thc t c lp hoc trong iu

kin cho php ta vn dng chiu cao ca cc ct, x ct n chiu sng. Ring

ct c lp thng tn km hn v kinh t nn ch dng khi khng th tn

dng c chiu cao ca cc ct, x...

T


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7

- Nu t cc ct thu st trn cc kt cu ca trm phn phi ngoi tri v

dng dy chng st bo v cho don dy dn ni t s cui cng ca trm

n ct u tin ca ng dy th chng sc ni t chung vi h thng

ni t chung ca trm v tng ln nh ny cn tu thuc vo thng s ca

dng in st v in trni t xung kch ca h thng. Khi in p ny

vt qu gii hn cho php th c th gy nn nguy him cho cc thit bin,

do vy ch trong iu kin cho php mi c t ct thu st trn cc cng

trnh trong trm hoc dy chng st trong trm.

- Khi thit k bo v chng st nh trc tip vo trm bin p, ngoi cc

yu cu v k thut cn phi ch n vn kinh t v vn m thut.

I. CC YU CU K THUT:

- Vi mc ch gim vn u t khi thit k bo v chng st nh trc tip

vo trm bin p ngoi tri, ngi ta thng b tr ct trn cc cao c sn

nh ct, x... i vi trm 110KV do c mc cch nh cao nn cc ct thu

st c tht trc tip trn cc kt cu ca trm. Cc tr ca cc kt cu trn

c t cc ct thu st phi l ngn nht sao cho dng in st (Is) khuych

tn vo t theo 3 4 thanh ci ca h thng ni t.

- i vi trm 22KV khi b tr ct thu st trc tip trn x th phi tng

cng cch in n cp 110KV, do vy s c tn tht v kinh t. Khi dng

ct thu st c lp th phi ch n khong cch gia cc ct thu st ti cc

b phn ca trm trnh kh nng phng in t ct n cc thit b bo v.

Khi dng ct n chiu sng lm gi cho ct thu st th phi cho dy dn

in n bng n vo ng ch v chn di t.

- m bo cho cgii v chng n mn kim loi cn phi theo ng quy

nh v cc loi vt liu, tit din dy khi dng trn mt t v di t.


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8

II. GII THIU SLC V THIT K TRM 110/22KV:

-Trm c kch thc: 60 x 100m2

-Tng din tch trm: 6000m2

- Chiu cao ln nht cn c bo v pha 110KV l 11m pha 22KV l 8m

- Trong trm c 2 my bin p 110/22KV, c 2 lng dy 110KV i vo

v 5 lng dy 22KV i ra.

- Trn cc l 110KV c dy chng st nn cc thit b ca trm nm di

on ng dy vo trm n x n dy u c bo v nn ta thit k

chng st cho pha 110KV c th khng cn tnh n phm vi ny.- Trong phn thit k ny ta a ra cc phng n b tr ct thu st bo

v trm bin p ngoi tri theo cc yu cu k thut, m thut v kinh t sau

chn phng n hp l tnh ton.

III - PHM VI BO V CA CT THU ST:

1. Phm vi bo v ca mt ct thu st (H1-1):- Bn knh bo v cho cao hx l:


9/99

9

)hh(

h

h1

6,1r x

x

x +

=

Trong:

h - L cao ca ct.

hx - L c cao cn bo v.

h - hx = ha - L chiu cao hiu dng ca ct.

Nu hth3

23 th )8,0

1(5,1h

hh xx =

hhx 3

2> th

=

h

hxx 175,0

- Nu chiu cao ca ct h > 30m th ta phi kn h siu chnh nghal:

Prmhr xx .)30( => (vi P l h shiu chnh)

.5,5

hP=

2. Phm vi bo v ca hai ct v nhiu ct thu st :

- Nu hai ct c chiu cao bng nhau: gi s 2 ct cch nhau mt khong l

a.+ Nu a = 7h th bt kim no trn mt t gia hai ct sc bo

v an ton.

+ Nu a = 7h th ct bo vc cao l0

0

h

h c xc nh t h).

.77 00a

hha

hh ==

+ Ta xem h0 nh cao mt ct v tnh phm vi bo v cho cao hx

=>

=

000

0000

175,03

2

8,015,1

3

2

h

hhrhh

h

hhrhh

xoxx

xxx


10/99

10

+ Khi ct thu st c h> 30 thP

ahh

70=

Hnh 1-2

-Nu hai ct c cao khc nhau:

Hnh 1 - 3- Nu c nhiu ct: Ta phi xc nh cho tng nhm ct gn nhau (3 hay 4

ct) phi hp bo v thu st sao cho nh cc ct cng nm trn mt ng

trn ngoi tip, cc ct to thnh mt tam gic hoc a gic th phn bn

trong sc bo v hon ton nu:


11/99

11

ax hhhD 8)(8 =

Trong:

D - ng knh ng trn ngoi tip a gic do cc ct to thnh.

h L chiu cao ca cc ct thu st.

hx - L chiu cao ca vt cn bo v.

Hnh 1- 4

IV. KHONG CCH AN TON TRONG KHNG KH V T.

- Khong cch an ton trong khng kh SK.

- Bin in c xung (Dmax) trong trng hp chung xc nh theo cngthc:

[ ] )KV()WL(RR2

axImmaxU

22

XKXK ++=

Trong:

Imax - Dng in st tnh ton (KA)

RXK- in trxung kch ca b phn ni t (R)

L - cm ng ca dy dn t b phn ni t n im kho st )( H cn

gi l h sin cm.


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12

- Khi ta thay Imax = 150 KA; bn cch in ca khng kh l 500KV/m v

ax

IW

Im

2 = vi

S

KAI

60= th ta sc cng thc tnh ton dng xc nh

khong cch an ton cho php ca khng kh nh sau:

[ ]

[ ] )(8,015,0150

60.215,0

)()(2.500

150

500

max

222

2

22

mLRRLRR

KVWLRRU

S

XKXKXKXK

XKXKx

++=

++=

++==

- Khong cch an ton trong t S

- Tiu chun khong cch an ton Sc xc nh bng biu thc sau:

S= a.Rxk

Trong:

a- H s ph thuc tr s dng in st chn trong tnh ton vi Imax = 150

th a = 0,5.

Rxk- Tr sin trtn xung kch ca dng in st i qua b phn ni t

)(

xk0,5RdS =

Hnh 1- 5


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13

V. TRNH TTNH TON CHNG ST NH TRC TIP.

1 - B tr cc ct thu st :

2 - Xc nh chiu cao hiu dng ca ct :

- Tm ng knh D ca ng trn ngoi tip a gic i qua nh thu ct

st sao cho din tch a gic c bo v cho hx, p dng ton trm. Ta

phi tnh cao L ca ct thu st: h = hx + ha.

3- Kim tra kh nng bo vi vi vt nm ngoi phm vi ct

thu st bo v:

- Tnh bn knh bo v ca mt ct thu st.

- Tnh bn knh ca khu vc bo v gia 2 ct thu st v tnh bn knh r0x

m h0 bo vc.

- V khu vc bo v theo kch thc tnh c.

4. Kim tra li ton b:

- Kim tra li ton b bn v thit k nu c cao x no m cn bo v

cn nm ngoi bn knh bo v ro x th cn phi xem xt li thit k: tng

cao ct hoc b tr thm ct sao cho cc cao cn c bo v phi nm

trong phm vi bo v ca cc ct thu st.

VI. LA CHN PHNG N B TR CT:

1. Phng n 1:

B tr 10 ct thu st trong c 2 ct thu st t thm 2 u ca x n dy

u trm cn 8 ct dng c lp

a. Xt cc cp ct:

- Cc cp ct 1 - 2 -10 ta c:


14/99

14

)m(30l

)m(8l

101

21

=

=

Do to thnh mt tam gic vung nn:

)m(05,31830l 22102 =+=

)m(88,38

31

8

Dh

)m(31)05,3153,34)(3053,34)(853,34(53,342

05,31.30.8D

)m(05,312

05,31308P

h ===

=

=

=++

=

vi hx =11m cho nn chiu cao ca cc ct l : 11+3,88=14,88(m)

Vy ta chn chiu cao cc ct l 19 (m)

- Cc ct 2 - 3 - 10:

)m(04,413028l

)m(05,31l

)m(30l

22

103

102

32

=+=

=

=

Do cc ct ny to thnh mt tam gic thng nn.

)m(15,5

8

21,41

8

Dh

)m(21,41)04,4105,51)(05,3105,51)(3005,51(05,512

05,41.05,31.30D

)m(05,512

04,4105,3130P

a ===

=

=

=++

=

Vi hh = 11m chiu cao ca cc ct thu st l 11+5,15 = 16,15 (m)

Vy ta chn chiu cao ct l 19 (m).

- Cc ct 3 -4 -10.


15/99

15

Ta c

)m(56l

)m(04,41l

)m(99,343018l

104

103

22

43

=

=

=+=

Do cc ct to thnh mt tam gic thng nn:

)m(02,78

15,56

8

Dh

)m(15,56)5602,66)(04,4102,66)(99,3402,66(02,662

56.04,41.99,34D

)m(02,662

5604,4199,34P

a ===

=

=

=++

=

Vi hx = 11m ta c chiu cao ca cc ct l : 11+7,02 = 18,02(m)

Vy ta chn chiu cao ct l 19 (m)

- Cc ct 4-5-9-10:

)m(56ll

)m(30ll

95104

10954

==

==

Do cc ct to thnh hnh ch nht nn:

)m(94,78

53,63

8

Dh

)m(53,635630D

a

22

===

=+=

Chiu cao ca cc ct thu st vi hx = 11m l 11+ 7,94 = 18,94m

Vy ta chn chiu cao ca cc ct l :19(m).

- Cc ct 5 - 6 -7:

)m(28l

)m(33l

76

65

=

=

Do cc ct to thnh mt tam gic vung nn:


16/99

16

)m(41,58

28,43

8

Dh

)m(28,43)28,4314,52)(2814,52)(3314,52(14,522

28,43.28.33D

)m(14,522

28,432833P

)m(28,432833l

a

22

75

===

=

=

=++

=

=+=

Vi hx = 8m chiu cao ca cc ct l: 8+ 5,41=13,41(m)

Vy ta chn chiu cao ca cc ct l : 16 (m)

- Cc ct 5 - 7 - 9:

)m(28,433328L

)m(56l

)m(28,43l

22

97

95

75

=+=

=

=

Do cc ct to thnh mt tam gic nn ta c:

).m(09,78

76,56

8

Dh

)m(76,56

)28,4328,71)(5628,71)(28,4328,71(28,712

28,43.56.28,43D

)m(28,712

28,435628,43P

a ===

=

=

=++

=

Vi hx = 8m chiu cao ca cc ct l: 8+ 7,09 = 15,09(m)

Vy ta chn chiu co ca cc ct l: 16(m)

-Cc ct 7 - 8 -9:

)m(28,43l

)m(33l)m(28l

97

98

87

=

==

Do to thnh tam gic thng nn:


17/99

17

)m(41,5828,43

8Dh

)m(28,43)28,4314,52)(3314,52)(2814,52(14,522

28,43.33.28D

)m(14,522

28,433328P

a ===

=

=

=++

=

Vi hx = 8m cho nn chiu cao ca cc ct thu st l 8+5,41=13,41(m).

Vy ta chn chiu cao ca cc ct l: 16(m).

* Vy ta xc nh c:

+Cc ct 1-2-3 -4 -10 cao l 19 m

+Cc ct 5 - 6 -7 - 8 -9 cao l: 16m.

b. Xt cc cp ct bao quanh trm:

- Cp ct 1 -2:

+ Bn knh bo v ca mi ct cao 19m l:

=

h

hhr xx 8,0

15,1 v )m(67,12h3

2m11h

1x=


18/99

18

- Cp ct 2-3:

+ Bn knh bo v ca mi ct cao 19m l 7,88 (m)

+Phm vi bo v gia hai ct l:

v

)m(86,314,16

11114,16.75,0

h

h1h75,0r

)m(76,10h3

2m11h

)m(14,167

2019

7

ahh

o

x0x0

0x

o

=

=

=

=>=

===

- Cp ct 3-4:

+ Bn knh bo v ca mi ct cao 19m l 7,88m

+Phm vi bo v gia 2 ct l:

v:

)m(25,21411114.75,0

hh1h75,0r

)m(33,9h3

2m11h

)m(147

99,3419

7

ahh

0

x0x0

0x

10

= =

=

=>=

===

- Cp ct 4-5:

+ Bn knh bo v ca ct 4 l 7,88m

Bn knh bo v ca ct 5 l:

V:)m(75,3

16

11116.75,0

h

h1h75,0r

)m(67,10h3

2m11h

5

x5x

2x

=

=

=

=>=

+ Phm vi bo v gia 2 ct: v 2 ct c cao khc nhau nn

bn knh bo v ca ct 5 vi cao hx = 16(m) l:


19/99

19

V:)m(25,2

19

16119.75,0

h

h1h75,0r

)m(67,12h3

2m16h

4

x44

4x

=

=

=

=>=

)m(75,2725,230raa 4 ===

7

75,2716

7

ahh 50 =

=

V:)m(06,3

04,12.8,0

8104,12.5,1

h8,0

h1h5,1r

)m(03,8h3

2m8h

0

x0x0

ox

=

=

=

==

)m(47,229,11

8129,11.75,0rox =

=

-Cp ct 6-7:

+ Bn knh bo v ca mi ct cao 16m l: 3,75 (m)

+ Phm vi bo v gia hai ct:


20/99

20

=

===

o

xoox

60

h

h1h75,0r

)m(127

2816

7

ahh

V )m(8h3

2m8h 0x ===

)m(312

8112.75,0rox =

=

-Cp ct 7-8:

+ Bn knh bo v ca ct cao 16m l 3,75(m)


)m(127

2816

7

ahh 60 ===

=

0

x0ox

h

h1h75,0r

V: )m(8h32)m(8h 0x ===

)m(312

8112.75,0rox =

=

- Cp ct 8- 9:

+Bn knh bo v ca cc ct cao 16m l 3,75(m)

+Phm vi bo v gia hai ct l:


21/99

21

)m(46,228,11

8128,11.75,0

)m(52,7h3

2m8hvi

h

h1h75,0r

)m(28,117

3316

7

ahh

ox

o

xoox

8o

=

=

=>=

=

===

-Cp ct 9 -10

+ Bn knh bo v ca ct 9 cao 16m l 3,75m.

Bn knh bo v ca 10 ct cao 19m l 7,88m

+Phm vi bo v gia 2 ct: V 2 ct c cao khc nhau nn bn knh

bo v ca ct 10 vi cao h h =16m l:

=

10

x1010

h

h1h75,0r

V: )m(67,12h3

2m16h 10x =>=

)m(25,219

16

119.75,0rox =

=

)m(75,2725,230raa 10 ===

)m(04,127

75,2716

7

ahh

90===

V: )m(03,8h3

2m8h 0x =


22/99

22

+ Phm vi bo v gia 2 ct:

)m(71,147

3019

7

ahh 100 ===

V: )m(8,9h32m11h 0x =>=

)m(78,271,14

11171,14.75,0

h

h1h75,0r

o

x0ox =

=

=

*T cc s liu tnh ton trn ta c bng sau:

Bng 1-6

STT Cc cp ct hx(m) ho(m) rox(m)

1 1-2 11 17,86 6,17

2 2-3 11 16,14 3,84

3 3-4 11 14 2,25

4 4-5 8 12,04 3,06

5 5-6 8 11,29 2,47

6 6-7 8 12 3

7 7-8 8 12 3

8 8-9 8 11,28 2,46

9 9-10 8 12,04 3,06

10 10-1 11 14,71 2,78

- T bng s liu trn ta v phm vi bo v ca cc ct thu st (theo s

b tr ct thu st)


23/99

23


24/99

24

2 - Phng n 2:B tr 12 ct thu st trong 2 ct t trn x n u trm, ct cn

li t c lp.

a. Xt cc cp ct:- Cp ct 1 - 2 - 11

)m(8l 21 =

)m(30l 111 =

Do cc ct to thnh mt tam gic vung nn:

)m(88,38

31

8

Dh

)m(31)05,3153,34)(3053,34)(853,34(53,342

05,31.30.8D

)m(53,342

05,31308

P

)m(05,31308l

a

22

112

===

=

=

=

++

=

=+=

Vi hx = 11m chiu cao ca cc ct l: 11+ 3,88 = 14,88 (m)

Vy ta chn chiu cao ca cc ct l 18 (m)

- Cc ct 2 -3 -11:

)m(04,412830l

)m(05,31l

)m(30l

22

113

112

32

=+=

=

=

Do cc ct to thnh mt tam gic cho nn:

)m(15,58

21,41

8

Dh

)m(21,41)04,4105,51)(05,3105,51)(3005,51(05,512

04,41.05,31.30D

)m(05,51

2

04,4105,3130P

a ===

=

=

=++

=


25/99

25

Vi hx = 11m chiu cao ca cc ct l: 11+ 5,15 = 16,15(m).Vy chn

chiu cao ca cc ct l 18(m)

- Cc ct 3 -11- 12:

)m(73,292810l

)m(40l

)m(04,41l

22

1211

123

113

=+=

==

Do cc ct to thnh tam gic thng nn:

)m(45,58

58,43

8

Dh

)m(58,43)73,2942,55)(4042,55)(05,4142,55(42,552

73,29.40.05,41D

)m(42,552

73,294005,41P

a ===

==

=++

=

Vi hx = 11m th chiu cao ca cc ct l: 11+ 5,45 = 16,45(m). Vy ta

chn chiu cao ca cc ct l18 (m)

- Cc ct 3 - 4 -12:

)m(83,482840l

)m(40l

)m(28l

22

124

123

43

=+=

=

=


)m(1,68

8,48

8

Dh

)m(8,48)83,4842,58)(4042,58)(2842,58(42,582

83,48.40.28D

)m(42,582

83,484028P

a ===

=

=

=++

=


26/99

26

Vi hx = 11m th chiu cao ca cc ct l: 11+ 6,1 = 17,1 (m). Vy ta

chn chiu cao ca cc ct l: 18(m)

- Cc ct 4 -5 -12:

)m(73,291028l

)m(83,48l

)m(30l

22

125

124

54

=+=

==

Do cc ct to thnh tam gic thng nn ta c:

)m(48,68

86,51

8

Dh

)m(86,51)63,2928,54)(83,4828,54)(3028,54(28,542

73,29.83,48.30D

)m(28,542

75,2983,4830P

a ===

==

=++

=

Vi hx = 11m chiu cao ca cc ct l: 11+6,48 = 17,48 (m)

Vy ta chn chiu cao cc ct l 18 (m)

- Cc ct: 5 -6 -12:

)m(41,342028l

)m(73,29l

)m(30l

22

126

125

65

=+=

=

=

Do cc ct to thnh tam gic thng nn ta c:

)m(57,48

54,36

8

Dh

)m(54,36)41,3407,47)(73,2907,47)(3007,47(07,472

41,34.73,29.30D

)m(07,472

41,3473,2930P

a ===

=

=

=++

=

Vi hx = 8m chiu cao ca cc ct l: 11+4,57 =15,57 (m)


27/99

27

Vy ta chn chiu cao cc ct l: 18 (m)

- Cc ct 10 -11-12:

)m(41,343028l

)m(30l

)m(73,29l

22

1210

1110

1211

=+==

=

Do cc ct to thnh tam gic cn nn:

)m(57,48

54,36

8

Dh

)m(54,36)41,3407,47)(73,2907,47)(3007,47(07,472

41,34.73,29.30D

)m(07,472

41,3473,2930P

a ===

=

=

=++

=

Vi hx = 11m chiu cao ca cc ct l: 11+4,57 =15,57(m). Vy ta

chn chiu cao ca cc ct l 18(m)

-Cc ct 6 -7 - 8:

)m(28l

)m(33l

87

76

=

=

Do cc ct to thnh tam gic vung nn:

)m(41,58

28,43

8

Dh

)m(28,43

)28,4314,52)(2814,52)(3314,52(14,522

28,43.28.33D

)m(14,522

28,432833P

)m(28,432833l

a

22

86

===

=

=

=++

=

=+=

Vi hx = 8 m chiu cao ca cc ct l: 8+5,41= 13,41m

Vy ta chn chiu cao ca cc ct l 16 (m)


28/99

28

- Cc ct 6 -8 -10:

)m(56l

)m(28,432833l

)m(28,43l

106

22

108

86

=

=+=

=


09,78

76,56

8

Dh

)m(76,56)5628,71)(28,4328,71)(28,4328,71(28,712

56.28,43.28,43D

28,712

5628,4328,43P

a===

=

=

=++

=

Vi hx = 8m th chiu cao ca cc ct l: 8+7,09 = 15,09(m)

Vy ta chn chiu cao ca cc ct l 16(m)

- Cc ct 8 -9 - 10:

)m(28,43l

)m(28l

)m(33l

108

98

109

=

=

=

Do cc ct to thnh tam gic vung nn:

)m(41,58

28,43

8

Dh

)m(28,43

)28,4314,52)(2814,52)(3314,52(14,522

28,43.28.33D

)m(14,522

28,432833P

a ===

=

=

=++

=

Vi hx =8(m) th chiu cao ca cc ct l 8+5,41=13,41(m)

Vy ta chn chiu cao ca cc ct l 16(m)


29/99

29

* Vy ta xc nh c:

+ cc ct 1 - 2 -3 -4 - 5 - 11 - 12 cao 18 (m)

+ cc ct 6 - 7 - 8 -9 - 10 cao16 (m)

b. Xt cc cp ct bao quanh trm:

-Cp ct 1 - 2:

+ Bn knh bo v ca mi ct cao 18 (m)

V: m12h3

2m11h 1x =


30/99

30

=

===

0

x0x0

0

h

h1h75,0r

)m(14,157

2018

7

ahh

V: )m(09,10h3

2m11h 0x =>=

)m(11,314,15

11114,15.75,0rox =

=

- Cp ct 3 - 4:

+ Bn knh bo v ca ct cao 18m vi hx = 11m l 6,38 (m)

+ Phm vi bo v ca 2 ct

=

===

o

xoox

3o

h

h1h75,0r

)m(147

2818

7

ahh

V )m(33,9h3

2m11h

ox=>=

)m(25,214

11114.75,0rox =

=

- Cp ct 4 - 5:

+ Bn knh bo v ca ct 4 cao h = 18m l 6,38m

+Phm vi bo v gia 2 ct:

)m(71,137

3018

7

ahh

10===

V )m(14,9h3

2m11h 0x =>=


31/99

31

)m(03,271,13

111h75,0r 0ox =

=

- Cp ct 5 - 6:

+ Bn knh bo v ca ct 5 cao 14m v hx= 8m l 6,38(m)

Bn knh bo v ca Ct 6 cao 16 m l:

V: )m(67,10h3

2m8h 0x ==

V: )m(12h3

2m16h

5x =>=

=

==

=

===

=

=

=

0

x0ox

60

5

5

x55

h

h1h75,0r

)m(93,117

5,2816

7

ahh

)m(5,285,130raa

)m(5,118

16118.75,0

h

h1h75,0r

V: )m(93,11h32m8h

0x=>=

)m(95,293,11

8193,11.75,0rox =

=

- Cp ct 6-7:


32/99

32

+ Bn knh bo v ca ct cao 16m l 9 (m)


=

===

o

xoox

6o

h

h1h75,0r

)m(28,11

7

3316

7

ahh

V )m(52,7h3

2m8h

0x =>=

)m(46,228,11

8128,11.75,0rox =

=

-Cp ct 7- 8:


+ Phm vi bo v gia hai ct.

=

===

o

x0ox

7o

h

h1h75,0r

)m(127

2816

7

ahh

V )m(8h3

2

m8h 0x ===

)m(312

8112.75,0rox =

=

-Cp ct 8 -9:


+ Phm vi bo v gia hai ct.

=

===

o

x0ox

8o

h

h1h75,0r

)m(127

28167

ahh

V )m(8h3

2m8h

0x===


33/99

33

)m(312

8112.75,0rox =

=

-Cp ct 9 -10:

+ Bn knh bo v ca ct cao 16m l 9m

+ Phm vi bo v ca 2 ct:

=

===

0

xoox

9o

h

h1h75,0r

)m(28,117

3316

7

ahh

V )m(52,7h3

2m8h xx =>=

)m(46,228,11

8128,11.75,0rox =

=

-Cp ct 10 -11:

+ Bn knh bo v ca ct 11 cao 18m l 6,38 (m).

Bn knh bo v ca ct 10 cao 16m l 9 (m).

+ Phm vi bo v gia 2 ct: v 2 ct c cao khc nhau cho nn

bn knh bo vct 11 vi cao hx = h10 = 16m l:

=11h

h1h75,0r x1111 v )m(12h

3

2m16h 11x =>=

)m(5,118

16118.75,0r11 =

=

=

===

===

0

x0x0

100

11

h

h1h75,0r

)m(93,117

5,2816

7

'ahh

)m(5,285,130raa

v )m(95,7h3

2m8h

0x=>=


34/99

34

)m(95,293,11

8193,11.75,0rox =

=

-Cp ct 11-1:

+ Bn knh bo v ca ct cao18m l 6,38m

+Phm vi bo v gia hai ct:

=

===

o

xoox

o

h

h1h75,0r

)m(71,137

3018

7

ahh

V )m(14,9h3

2m11h ox =>=

)m(03,271,13

11171,13.75,0rox =

=

* T nhng s liu tnh ton trn ta c bng tng kt sau y:

Bng 1-8

STT Cc cp ct h0 (m) hx = (m) r0x (m)

1 1 - 2 16,86 11 4,39

2 2 - 3 15,14 11 3,11

3 3 - 4 14 11 2,25

4 4 - 5 13,71 11 2,03

5 5 - 6 11,93 8 2,95

6 6 - 7 11,28 8 2,46

7 7 - 8 12 8 3

8 8- 9 12 8 3

9 9 - 10 11,28 8 2,46


35/99

35

10 10 -11 11,93 8 2,95

11 11-1 13,71 11 2,03

T bng s liu trn ta vc phm vi bo v ca cc ct thu st (theo

s b tr ct thu st)


36/99

36

* So snh 2 phng n:

+ V mt k thut th c 2 phng n u m bo thit k bo v

trm

+ V mt kinh t th phng n 1 kinh t hn v phng n 1 ch

phi dng 10 ct trong c 8 ct c lp so vi phng n 2 l phi dng

ti 12 ct trong c ti 10 ct phi dng c lp.

Do vy ta chn phng n 1 thit k thi cng bo v trm bin p

110/22KV.


37/99

37

CHNG II

-----o0o-----

TNH TON NI T CHO TON TRM

him v ca ni t l tn dng in xung t m bo an

ton cho vt cn ni c tr s b. Trong HT ngi ta chia lm 3

loi ni nh sau:

- Ni t lm vic: Nhim v l m bo cho s lm vic

bnh thng ca thit b theo ch c quy nh sn. Loi ni t ny

gm ni t im trung tnh MBA o lng v ca khng dng trong b

ngang trn cc ng dy ti in.

- Ni t an ton (ni t bo v): c nhim vm bo an ton cho

ngi v thit b khi cch in b h hng tc l ni t mi b phn kim loi

bnh thng khng mang in nh: v MBA, my ct, cc gi kim loi...

khi cch in h hng trn cc b phn ny s xut hin in nh th nhng

do c ni t nn gic mc in th thp m bo an ton cho ngiv thit b khi tip xc vi nhng b phn ny.

- Ni t chng st: Mc ch l nhm m bo tn dng in st vo

trong t khi c st nh xung ct thu st hoc trn ng dy. Do s hn

chc dng in st ti cc thit bin cn c bo v.

- trm bin p v nguyn tc phi thit k tch ri 2 h thng ni t

l ni t lm vic v ni t chng st. phng khi c dng ngn mchln hay dng in st i vo h thng ni t lm vic ln hay nh s khng

gy nn in th cao trn h thng ni t an ton.

- Trong thc t cng vic ny rt kh thc hin c v nhiu l do nn

ngi ta thng ch dng mt h thng ni t chung thc hin c 2 nhim

N


38/99

38

v. V l nn h thng ni t chung l phi m bo yu cu ca c 2 loi

ni t, ngha l phi c in trni t nh hn hoc bng in trni t

nh nht ca mt trong hai h thng ni t k trn.

- Cc yu t cn chung cho h thng ni t.

+ B phn ni t c tr sin trni t cng nh th s thc hin

c cng tt nhim vu tn dng in st trong t v in th trn cc thit

bc ni t mc n nh. Tuy nhin vic gim in trni t s lm

cho chi ph vu t xy dng tng ln nhiu (do s lng kim loi tng).

Do cn phi c quy nh tiu chun tr s cho php ca in trni t.

* Vi cc thit bin ni t trc tip th in trni t yu cu l R)(5,0

* Vi cc thit b c im trung bnh tnh ni t trc tip th in tr

ni t yu cu l IR /250 (nu h thng ni t ch dng cho cc thit b

cao p)

* Vi h thng c im trung tnh cch in v h thng ni t cho c

thit b cao p v h p th in tryu cu l: IR /125 (nhng R chc

)(10 Dng in I tu theo mi trng hp c tr s khc nhau.

+ i vi ni t an ton th in trc chn sao cho cc gi tr

in p bc v in p tip xc trong mi trng hp u phi khng vt

qu tr s cho php.

+ Ngoi vic m bo tr sin trni t quy nh v gim in tr

ni t ca h thng ni t cn cn phi ch n vic ci thin s phn b

in th trn ton b din tch trm.

- H s ma: Ta bit rng t l mt mi trng phc tp khng ng

nht v kt cu v thnh phn m ch yu l do kh hu. Do vy thit k h


39/99

39

thng ni t cn tp trung v ch n tr s ln nht v tr s tnh ton in

trsut ca t c th c trong cc ma.

Kd .0 =

K l h s ma

0: in trsut c theo ma

- Phng php ni t: Theo chc nng ngi ta phn lm nhiu loi.

H thng ni t bao gm cc in cc trong t lm gim in trni t

theo tiu chun ca tng loi ni t. Cc in cc thng l cc thanh di

nm ngang hoc cc thng ng in p bc nh. Khi tnh ton ta phn ra

lm cc loi ni t t nhin v ni t nhn to.

Ni t t nhin l s dng cc ni t c sn nh dy chng st, ct

thu st, cc kt cu kim loi ca cng trnh cc ng ng nc. Cn ni t

nhn to nhm mc ch tho mn cc yu cu ni t ca cc cng trnh khi

ni t t nhin khng m bo c.

- Cc tham snh hng n ni t :

+ nh hng ca kch thc hnh hc

+ nh hng ca cc b tr in cc.

+ nh hng ca tr sin trt.

+ Hin tng phng in xung kch: Khi c dng xt i vo in cc

ni t, th gy ra mt in trng ln trn b mt in cc v trong t. in

trng t n gii hn th xy ra qu trnh phng in trong t. Cc tia

la in phng in pht trin xung quanh in cc to ra vng h quang, cc

ni t xem nh l to ra v in trni t gim, in trni t c tnh

bng cng thc:

=R


40/99

40

Vi 1


41/99

41

b- H thng ni t nhn to ca ni t an ton:

H thng ni t an ton ta s dng mch vng hnh ch nht c kch

thch nh sau:

Hnh 2-1

Mch vng c chn di phn in tch trm 110KV su 0,8m.

Phn mch vng ny cch tng ro 5m.

Ta chn loi thp dp 50 x 1mm = b = 50 mm = 0,05 m lm mch

vng.

Ta c:dt

KL

LR ttmv .

ln2

2

=

L- Chu vi mch vng L = ( 50+60).2 = 220 m

t- chn su ca mch vng t = 0,8 m.

d- ng knh quy i ca thanh dt )(025,0205,0 md ==

K- H s ph thuc t l 2,12

1 =L

Ltra bng ta c K = 5,64.

tKmdott .. = vi 6,1. =tm


42/99

42

)(52,4025,0.8,0

220.64,5.ln.

220.2

10.28,1

)(10.28,1)(10.28,16,1.10.8,022

244

==

===

mvR

mcm

Ta thy )(1)(52,1 >=mvR cho nn ta ta phi ng cc dc theo mch

vng gim in trca h thng ni t. Ta ng cc cc dc theo mch

vng c 3m mt cc v mi cc di 3m c ng knh l 40mm v nh vy

s cc l 743

220= ( cc).

)(57,28

38,0.4

38,0.4ln

2

1

10.40

3.2ln

3.2

10.8,0

)4

4

2

12(

2

3

2

=

++=

+

+=

lt

ltn

d

lm

lRc

in trtn ca h thng ni t c tnh nh sau:

74..52,1.57,28

52,1.57,28

.. ctcmvtc

mvcnt nRR

RRR

+=

+=

Tra bng ta c:

=

=

4,0

22,0

c

t

)(1)(85,04,0.48,11222,0.57,28

43,43


43/99

43

Hnh 2-2

Mch vng c chn di phn din tch trm 22KV c su 0,8m

phn mch vng ny c cch tng ro 5m

Ta chn loi thp dp 50 x 1mm = b = 50mm = 0,05m lm mch

vng. Ta c:dt

KL

LR ttm

=2

ln2

Trong : L - Chu vi mch vng: L= (30+50) 2 = 160(m)

t - chn su ca mch vng t = 0,8m

d - ng knh quy i ca thnh dp

)(025,02

05,0md ==

K - h s ph thuc t l 67,12

=

L

L Tra bng ta c K =

6,05

Kmttt .0 = vi Kmt = 1,6 )(10.28,1)(10.28,1116.10.8,0444 mcm ===

)(38,2025,0.8,0

160.05,6

160.2

10.28,1 22=

= LnRm

Nh vy


44/99

44

II. TNH TON NI T CHNG ST CHO TRM:

1. Mu:

Khi c dng in i vo b phn ni t nu tc bin thin ca dng

in theo thi gian rt ln th trong thi gian u in cm s ngn cn khngcho dng in i ti cc phn cui ca in cc, khin cho in p phn b

khng u, sau mt thi gian nh hng in cm mt dn v in p s phn

bu hn.

Thi gian ca qu trnh qu ni trn ph thuc vo hng s thi

gian: 2LglT = (T l t trng vi in cm tng L .1 v in dn gl ca in

cc)

T biu thc trn cho thy khi dng in tn trong t l dng mt

chiu hoc xoay chiu tn s cng nghip nh hng ca L khng ng k v

bt k hnh thc ni t no (thngng hoc nm ngang) cng u biu th

biir tr sin trtn.

Khi dng in tn trong t l dng in st tham s biu th bi ni t

tu thuc vo tng quan hng s thi gian T v thi gian u sng in. Khi

T


45/99

45

t an ton ca trm. Nh vy s gp trng hp ni t phn b di, tng tr

xung kch ZXK c th rt ln v ln gp nhiu ln so vi tr sin tr tn

xoy chiu l in ngc ln cc phn mang in ca trm. Do ta phi tnh

ton kim tra yu cu ca ni t chng st trng hp c dng in st i

va h thng ni t.

+ Dng sng tnh ton ca dng in st.

Trong tnh ton thit k ta chn dng sng tnh ton cu dng in st

l sng xin gc c bin khng i. Dng sng tnh ton ca dng in st

c biu din nh sau:

= .)( TdsikhiI

Tdsikhiattis

Hnh 2-3

Trong:

a - c dc dng in st quy nh a = tg = 30(KA/s).

I = 150KA - Bin dng in st i vi trm bin p

Nh vy thi gian u sng:

)(530

150s

aI

Tds ===

* Cc yu cu k thut i vi ni t chng st

t

i


46/99

46

Ta s kim tra theo iu kin m bo an ton cho cch in ca my

bin p ( y ta xt in p ti thi im khi c dng in st i vo h

thng ni t).

%50),0(. UTZI dc <

Trong:

I- Bin ca dng in st ly bng 150 (KA)

Z(0,Ts)- Tng trxung kch ti thi t = Ts v ngay ti ch dng

in st i vo in cc.

U50%- Tr sin p phng in xung kch t ln cch in ca my

bin p.

- Nu iu kin trn khng tho mn th phi tin hnh tnh ton ni t b

xung ti ni i vo h thng ni t ( tc l ni thm 1 in trsong song vi

h thng nhm mc ch lm gim tng trxung knh ).

2- Tnh ton ni t chng st cho trm 110 KV:

- Do ta dng ni t an ton lm ni t chng st cho nn trc ht ta phi

hiu chnh li tr s Rnt

( in trnhn to) theo yu cu ca ni t chng st

c ngha l ta phi hiu chnh h s ma ca ni t an ton theo h s mu

ca ni t chng st ( Tra bng 19 - 2 gio trnh kthutin cao p).

Kma( NCS ) = 1,4 - i vi thanh chn su 0,8m

Theo tnh ton ca phn ni t an ton:

)1()(.

ln.2

)(.)(

2

=dt

KL

L

NDATKSNDATR

md

mvo

Cn i vi t chng st. Ta c:

)2(.

ln2

)(.)(

2

dt

KL

L

NDCSKSNDCSR mdmv

o

=

Chia c hai v ca ( 2) cho ( 1) ta c:


47/99

47

)(33,152,1.6,1

4,1)(.

6,1

4,1)(

6,1

4,1

)(

)(

)(

)(

===

==

NDATRNDCSR

NDATK

NDCSK

NDATR

NDCSR

mvmv

m

m

mv

mv

Vy in trni t nhn to ng vi ni t chng st l:

)(83,074.4,0.33,122,0.57,28

33,1.57,28

.).(.

)(.)( =

+=

+=

nNDCSRR

NDCSRRNDCSR

cmvtc

mvcnt

a- Tnh ton tng trsng xung kch:

- tnh ton tng trsng xung kch ta c vi gi thit sau:

+ B qua in trni t t nhin.

+B qua cc thanh ni t cn bng p trong trm bin p+ Trong qu trnh tnh ton dn gin ho ta b qua qu trnh phng

tia la in trong t v gi thit in trsut ca t l khng i. Mt khc

in tr ca bn thn vt liu dng l ni t b hn rt nhiu so vi in

khng L ca n ( ng vi tr s dng in st) v nh hng n in dung C

ca in ni t cng rt nh hn nhiu so vi nh hng ca in dn ni t.

Nh vy ta c th coi mch vng ni t gm hai tai di L1 v L2 ghp

song song vi nhau v mi tia c chiu di l:

)(1102

220

221m

LLL ====


48/99

48

Hnh2-4

S thay th ca 1 tia h thng ni t.

Hnh2-5

Da vo s thay th trn ta c cc gi trin cm Lo v in dn Go

c tnh ton nh sau:

Go - in dn ca in cc tnh trn mt n v di

=mlNDCSR

Gont

1

)(2

1

Lo- in cm ca in cc ni t tnh trn 1 n v di

=m

H

p

lLo

)31,0(ln2,0

Trong:

l = L1 = L2 = 110 (m) ( chiu di mt tia)

)(83,0)( =NDCSRnt - in trni t nhn to ng vi ni t chng

st.

P- Bn knh ca cc ni t do ta chn b = 40 mm.

)(10.20202

3 mmmb

p ===

GoGoGoGo

Lo Lo Lo Lo


49/99

49

Thay cc thng s vo ta tnh c.

)(641,131,010.20

100ln2,0

110.610.6,0

100.83,0.2

1

3

32

m

HLo

mGo

=

=

===

Tnh ton phn b di khi khng xt n qu trnh phng in trong t

t s thay th ta c th lp c h phng trnh vi phn nh sau:

=

=

gUX

It

iL

X

U

.

Gii h phng trnh trn ta c in p ti thi im bt k trn in

cc:

+=

=

l

XKe

KT

lG

aU

K

T

t

txt cos)1(

121

. 121

0),(

Vi hng s thi gian:

22

200

.KlGLTK

= vi = 1K

Mt khc:

.2

12

200

1K

TT

lGLT K =

=

Tng trxung kchu vo in cc ni t (i vi 1 tia)

+=

=

0

12

1

0).0( )1(

121

1

K

Kt

tte

Kt

T

lGZ

Tng trxung kch tng ng u vo in cc ni t gm hai tia

ghp song song ti thi im: .5 sTt ds ==


50/99

50

+==

=

12

1

0)5,(),0( )1(

121

1

2

1

K

T

T

dsot

K

ds

eKT

T

lGZZ

tnh )5,0(Z ta xt chui:

=

=

=

=

1 1 1222

1)1(

K K K

TT

TT

K

e

KK

e Kds

K

ds

=

=

=1

2

26433,1

6

1

K K(stay ton hc)

=

++++=1

2222 21K

T

T

T

T

T

T

T

T

K

eee

K

e Kds

K

ds

K

ds

K

ds

LL

Ta c: e-3 = 0,0497

e-4 = 0,0183

e-5 = 0,0067

e-6 = 0,0024

e-7 = 0,00091

Cho nn ta ly cp chnh xc l 0,001 th khi 7>K

ds

T

Tth ta coi:

02

K

e Kds

T

T

Do gii hn: 7K

ds

T

T

Mt khc ta c:

.2

7 12

12

1

ds

dsK T

TKK

T

T

K

TT =

Vi

)(98,91.14,3

100.641,1.10.6

. 22

23

21

2

20

1 sK

lGLT o ==

=

(v K l snguyn dng)


51/99

51

74,35

98,9.7=K

Vy ta ch tnh n gi tr K < 3,74 Tnh K = 1 3

Vi K = 1 3 ta c cc gi tr 21

.KT

Tds tng ng l:

2

11 .1 KT

TK ds=

Thay cc gi tr va tnh c trn vo biu thc ca Z(0,5) ta c:

)(093,2)641,036,1(5

98,9.21

110.10.6

1.

2

13)5,0(

=

+=Z

Vi )(93,2)5,0( =Z ta kim tra iu kin ni t chng st xem c tho

mn khng nu khng tho mn th ta phi tin hnh ni t b sung.

)460)110(43993,2.150. %50)5,0( KVKVUZIs =>

Trong tnh ton ly dng in st Is = 150KA; a = 30KA/ ,S in p

trn b phn ni t c xc nh.

1=

3

1=2

54

2

250

22

22

13

22

12

2

11

6410=3

+2

+==

54=39895

=3=

2=29895

=2=

50=19895

=1=

K K

KT

TT

T

ds

ds

ds

eee

K

e

K

e

KT

TK

KT

TK

KT

TK

K

ds

K

ds

,

,.,

.

.,.

,.,

.

,,

.


52/99

52

dd

PdKPddsd

KKPd

KPddSQ

SEURIU

SEUdt

dLRIU

..

..

.

= vi L- chiu di cc = 2,5m.

)(105,0

55,0

5,0

)(83,203,0

5,2.1,50,6

==

=


53/99

53

Hnh 2-6

Trong:

L- Chiu di cc = 2,5 m v cc c lm bng thp gc 4040.4mm.

mhl

t 05,28,02

5,2

2/ =+=+=

d- ng knh ca cc = 0,95.40.10-3= 0,038 m

)(71,405,205,2.4

5,205,2.4ln

2

1

038,0

5,2.2ln

5,2.14,3.2

45,1.10.8,0 2=

+

+= cR

Tnh in trthanh nm ngang bng thp dt :

dt

Ka

aR ttt .

ln2

2

=

Trong:

t = 0,8 m - L chn su .

K = 1 L h s hnh dng ( tia ngang).

D - L ng knh quy i ca thanh thp dp vi b = 40 mm

mmmb

d 02,0202

===

a = 10 m - L di ca thanh .


54/99


55/99

55

Hnh 2-8

Tr s xung kch ca tia XKT . Tra bng 10 (trang 87 - sch hng dn thit k

tt nghip) ta c cc dng st vc th quan h XKC v d . T th ta

c:

IS = 5KA 10KA 20KA 40KA

Th XKT = 1,05 0,93 0,83 0,74

Hnh2-9

0,8 2 4 6 8 10

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

1,1

Is = 40(KA)

Is = 20(KA)

Is = 10(KA)

Is = 5(KA)

(10 .cm)4

kxc

0,8 2 4 6 8 10

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

1,1

Is = 40(KA)

Is = 20(KA)

Is = 10(KA)

Is = 5(KA)

(10 .cm)4

kxt


56/99

56

* Tr s XK t bng 10 (trang 87 - sch hng dn thit k tt nghip)

ta tra c h s s dng vi cc dng in xung kch l 0,8. T cc gi tr

IS(KA) ta tnh c cc ga tr Ut tng ng vi chng nh bng 2-11

Bng 2-10

Is (KA) 5 10 20 40

XKC 0,87 0,8 0,171 0,57

RXKC )( 32,174 47,976 42,579 34,183

Uc(KV) 326,087 399,70 1064,467 1709,145

XKC 1,05 0,93 0,85 0,74

RXKC )( 19,221 25,882 23,655 20,594

Ut(KV) 182,634 323,524 59,387 1029,71

Vi cc gi tr IC = 5;10; 20;40 KA ta ging ln ng cong Uc ri x

ngang ct ng Ut v h vung gc vi trc I ta c cc gi tr I v tnh

c IS = 3IC + 2I

Hnh 2-11

1200

600

I(KA)

U(KV)

1800

5 10 25 40

Ut = f(It)

Uc = f(Ic)


57/99

57

Uc(KV) 326,087 599,70 1064,467 1709,146

IC(KA) 5 10 20 40

It (KA) 11 19 42 67

IS (KA) 37 68 144 254

Bng 2-13

T cc gi tr Uc v IS ta s thu c th quan h gia U v IS v ta

xc nh U bng cch t I = 150KA dng ln th v dng sang tr U ta c

U = 1200KV

)(8150

1200 == XKR

Phng n ni t m bo yu cu k thut vi ct thu st c lp

pha trm 22KV. T cc phn tnh ton trn, ta vc s ni t cho ton

trm

Hnh 2-14

Phng n ni t m bo yu cu k thut vi ct thu st c lp

pha trm 22KV. T cc phn tnh ton trn ta sc s ni cho ton

trm

Bng tng kt s lng kim loi dng cho ton trm

I(KA)

U(KV)

60 120 180 240

600

1200

1800

Ud = f(Is)


58/99

58

Thp dp 50 x 1mm 300m

Cc 40 x 40 x 4mm 24 cc = 60m


59/99

59

Hnh 2.12. S nit ton trm 110/22kV


60/99

60

III. TNH TON NI T CT NG DY 110KV:

1- Nhim v:

Nhim v ch yu ca ni ct ng dy l thot dng in st khic st nh vo ng dy chng st. Ngoi ra i vi cc ng dy 3

20KV khi i qua khu vc ng dn c th ni t cn c nhim v bo v an

ton cn trong h thng ng dy c dng ngn mch ln ( KVUdm 110 ) do

trong h thng in c rle bo v tc ng nhanh do y nhim v bo

v an ton khng t ra. Nh ta bit khi c st nh dng st rt ln c th

lm hng ng dy v trm, do vy ni t ct in trng dy l ht sc

cn thit trong xy dng v vn hnh h thng in.

Gi R l RXK l in trni t n nh v in trni t xung kch,

ta c:

RRXK .= vi R l h s xung kch

Thng i vi ng dy ngi ta quy nh in trni t ng vi

tn s cng nghip.

i vi in trni t ca ng dy cng cn phi ch n qu

trnh sng in p v sng in lan truyn n cc cc. Do tc dng ca

in cm ca cc trong vic khuych tn dng in st nn i vi ni t ca

ct ng dy cng chia ra l ni t tp trung v ni t ko di.

in trni t ca ng dy ph thuc vo in trxut ca t ,

iu xut pht t ch nu in trsut cao th dng in s b v cc vng

y vic thit k xy dng v lp t h thng t s gp rt nhiu kh khn v

gi thnh xy dng rt cao.

Tr s quy nh ca in trni t tn s cng nghip cho bng di y:


61/99


62/99

62

+ Vi loi mng cc th c th chn cc ngy vo l mng hay dng

ni t dng tia - cc.

i vi tia th di gii hn l:

Chiu di gii hn ca tia in trsut ca t )( m

40m 410.5

60m 410.25

100m 410.100

Bng 2-16

- Ta chn mng l mc lm mng cho ct ng dy c treo mt

dy chng st 110KV v ta tin hnh tnh ton ni t vi dng l tia - cc.

Ta c in tr )(10.8.04

cm= nn ta tnh ton ni t sao cho in trni tca ct ng dy l R


63/99

63

- Tia di 6m bng thp c b = 40mm = 0,04m tia c chn su 1,5m- Cc dng loi cc bng thp gc 40 x 40 x4mm

)(038,0)(38940.040.95,0 mmmdd ====

Khong cch cc cc l 3m, chiu di cc l 3m

- H s ma: Kmt = 1,6 ; Kmc = 1,45

* in trca thanh ni:bt

l

lR ttt .

2ln

.2

2

=

Trong:

)(10.28,16,1.10.8.0 22 mtt ==

l = 6m, t = 1,5m ; b = 0,04m

)(09,2404,0.5,1

6.2ln

6.14,3.2

10.28,1 22== tR

* in trca cc thp gc 40 x 40 x 4mm

+

+

=14

14ln

2

12ln

2 t

t

d

l

lR ttc

Trong:

)(10.16,145,1.10.8.0 22 mtt ==

l = 3m

t/ = 1/2 = 1,5m

d = 0,04m

)(23,3435,1.4

35,1.4ln

04,0

3.2ln

3.14,3.2

10.16,1 2=

+

+= cR

* in trca h thng ni t tia - cc:


64/99

64

ctc

ctnt nRR

RRR

..

.

+=

Trong:

n - L s cc cn s dng l 2 cc

c v t - L h s s dng c xc nh trong bng sch hng dn

thit k tt nghip cao p vi a/l =1

Ta c:85,0

87,0

=

=

c

t

)(61,112.87,0.09,2485,0.23,34

23,34.09,24=

+= ntR

Ta thy rng


65/99

65

Vi: )(10.16,145,1.10.8,0 22 ==tt

L = 3 ( m)

D = 0,038( m)

T/ = 1,5 m

)(55,3435,1.4

35,1.4ln

2

1

038,0

3.2ln

3.14,3.2

10.16,1 2=

+

+= cR

in trca h thng ni t tia cc:

nRR

RRR

cttc

tcHT ...

.

+=

Trong:

n = 4 ( l slng cc sdng)

t v c tra trong bng 3,5 sch hng dn thit k tt nghip k thut

in cao p vi 2=l

a .

)(5,84.74,0.09,2477,0.55,34

09,24.55,34

74,0

77,0

=+

=

=

=

HT

c

t

R

Ta thy rng


66/99

66

ng dy ti in l phn t di nht ca HT nn thng b st nh

v chu tc ng ca in p kh quyn, c th dn n ct my, ct ng

dy nh hng ti s cung cp in ca li ng thi ph hoi thit b trong

trm. Do ta phi nghin cu chng st cho ng dy ti in, c bit l

nhng on gn trm, v khi st nh c thr to nn sng truyn vo trm

gy nguy him cho ngi v thit b trong trm.

Qua in p kh quyn xut hin trn ng dy l do st nh trc tip

vo ng dy dn, dy chng st, ct hoc xung t gn ng dy. Khi

xt n ch tiu kinh t ta ch c th chn theo mc hp l v kinh t v k

thut, tan khng th chn c mc cch in theo yu cu ca qu in p

kh quyn v tr s ca n l ln.

Vi mc treo cao trung bnh ca dy trn cng ( dy chng st) l h,

ng dy s thu v cc phng in st trn di t rng 6h v chiu di bng

chiu di ng dy. Tng s ln st nh thng ln ng dy hng nm

c tnh l:

ngsTB nLhN ..10.)9,06,0(3=

Trong : hTB- cao trung bnh ca dy cao nht ( m)

Nngs- s ngy st nh hng nm trong khu vc dy i qua

10070 =ngsN ngy.

L- chiu di ng dy ( km)

Do tham s dng st nh l khc nhau, khng phi ln no cng dn

n

phng in trn cch in. xy ra phng in khi st nh th tr s qu

in


67/99

67

p kh quyn phi ln hn mc cch in xung kch ca ng dy. Do vy

s

ln phng in trn trn cch in ph thuc vo gi tr xc sut phng in

rp

v s ln phng in c xc nh:

pdngsTbpdpd rnLhNrN ....),,(3109060==

Phng in trn cnh in ch gy ct in khi phng in xung kch

trn cch in chuyn thnh ho quang duy tr bi in p lm vic xc sut

trthnh h quang ph thuc vo graien in p lm vic dc theo ng

dy phng in:

).( LoEf = vi )(.m

KVL

ULoE

pd

LV=

Trong : ULV- in p lm vic ca ng dy.

Lp- chiu di ng phng in.

Vy s ln ct in hng nm do st nh vo ng dy ti in l:

rnLhrNN pdngstbpdc .....),,(..3109060==

so snh kh nng chu st ca ng dy ti in c tham s khc

nhau ngi ta dng tr s suts ct ng dy tc l s ln ct khi ng dy

c chiu di L = 100km c tnh l:

rhn pdtbcd ..).,,( 9060=

Do gim s ln ct din ta phi gim rp hoc .

+ Gim rp: bng cch tng cng cch in ng dy v treo dy

chng st. Treo dy chng st l c hiu qu nht. Vi vng t c cm 510>

th dy chng st s khng pht huy tc dng.


68/99

68

Gim : gim c khi gim c cng in trng dc theo

ng phng in hay phii tng Lp( tng s bt s).

Ta thy rng ng dy 110KV i qua vng c st nh hot ng

mnh cn c bo v bng dy chng st. ng dy 22KV c trung tnhcch in v cch in ca ng dy l rt yu nn khng treo dy chng

st.

I.NG DY 110KV.

1.Tham s ct ng dy 110KV

- Dy dn dng loi AC - 185 c ng knh d = 18,8 mm = 18,8.10-3m pha

A1, A2 treo cao 20,8m, B1 v B2 treo cao 17,8 m, C1 v C2 treo cao 14,8m.Ct ng dy 110kv - 2l - 1 dy chng st.


69/99

69

Hnh 3-1:Ct ng dy 110KV- 2 l- 1 dy chng st

- Dy chng st l dy thp C- 70 c ng knh d = 11,4 mm, r = 5,7

mm treo cao h = 25 m.

- vng ca dy chng st l fcs= 6 m. vng ca dy dn in lfdd= 8,5 m.

- Chui cch in dng loi s treo 54 , c 7 bt s.

- Khong vt ng dy l lKV= 200m.- U50% cch in 110Kv l 650 Kv/7 bt s.- H s hiu chnh vng quang cp in p 110Kv l 31= ,

2. Cc s liu tnh ton:

- treo trung bnh ca dy chng st.

Hcstb= hcs- 2/3 fcs= 25 - 6(2/3)o= 21 m.

- treo cao trung bnh ca dy dn pha A1, A2.

mfhh ddAtbAA 1315=5832820=3

2=21

,,).(,)(

- treo cao trung bnh ca dy dn B1, B2.

)(,,)(,)( mfhh ddBtbBB 1312=5832817=3

2=21

- treo cao trung bnh ca dy dn C1, C2.

)(,,).(,)( mfhh ddctbCC 139=5832

814=32

=21

- Tng trsng ca dy dn c tnh theo cng thc:

r

hZdd

260= ln.


70/99

70

Trong : h - treo cao trung bnh ca dy dn.

+ r l bn knh ca dy dn: r=1049=210818 3

3

.,.,

- Tng trsng ca dy dn pha A1, A2

)(,.,

,.ln.

..ln. 612484=

1049

1315260=

260=

321

r

hZ

tbAA

dd

- Tng trsng ca dy dn B1, B2)(,

.,

,.lnln 352471=

1049

1312260=

260=

321

r

hZ

tbBB

dd

- Tng trsng ca dy dn pha C1, C2.)(,

.,

,..ln

.ln 305454=

1049

139260=

260

321

r

hZ

tbCC

dd

- Tng trsng ca dy chng st:)(,

.,

.ln

.ln 297534=

1075

21260=

260=

3r

hZ cstbcs

- Tng trsng ca dy chng st khi c vng quang:)(,

,

,998410=

31297534

==

ZZ csvqcs

- Gc bo v pha A1, A2:h

lxarctgA

=

Trong : lx- chiu di x treo dy pha tnh t tm ct.

Ac hhh = l k hiu gia chiu cao ct v chiu cao

dy dn cc pha.

o

A arctg 4625=820252

=21 ,,


71/99

71

- Gc bo v pha B1, B2:o

B arctg 2924=81725253

=21 ,,

,

- Gc bo v pha C1, C2:o

C arctg 3916=814253

=21 ,,

Ta thy rng cc gc bo v cc pha n < 30o. Vy m bo yu cu

v chng st nn ta chn loi ct st v treo dy dn, dy chng st nh trn

tnh ton.

* H s ngu hp gia dy dn v dy chng st.- H s ngu hp pha A1-2 v dy chng st:

2

2

12

12

2=

r

h

d

D

Koln

ln

D12- khong cch gia dy chng st v nh hng cu pha A1-2

d12- khong cch gia dy chng st v dy dn pha A1-2

h2- bn knh dy chng st.

( ) ( )

( ) ( ) mlhhd

mlhhD

x

x

26=2+131521=+=

18536=2+21+1315=++=

22221212

22222112

,,

,,

Ta c:

1980=

1075

21226

18536

=2

=

32

2

12

12

,

.,

.ln

,

,ln

ln

ln

r

h

d

D

Ko

Khi c nh hng ca vng quang th:


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72

2576=311980== ,,.,.KK oorq

- H s ngu hp gia pha B1-2 v dy chng st.( ) ( )

( ) ( ) mlhhd

mlhhD

x

x

459=253+131221=+=

2933=253+1312+21=++=

22221212

22222112

,,,

,,,

Ta c:

1410=

1075

2124592933

=2

=

32

2

12

12

,

.,

.ln

,

,ln

ln

ln

r

h

d

D

Ko


1830=311410==0 ,,.,KK orq

- H s ngu hp gia pha C1-2 v dy chng st.( ) ( )

( ) ( ) )(,,

,,

mlhhd

mlhhD

x

x

2412=3+13921=+=

330=3+139+21=++=

22221212

22222112

Ta c: 1010=

1075

2122412 330=

2=

32

2

12

12

,

.,

.ln

,,ln

ln

ln

r

h

dD

Ko


1310=311010== 00 ,,.,.KK rq

Qua tnh ton ta thy rng h s ngu hp gia dy chng st v pha

A1-2 l ln nht do :

+ tnh sut ct do st nh vng qua dy chng st vody dn ta

xt cho pha A1-2 c gc bo v ln v treo cao hn.


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73

+ tnh st nh vo khong vt ca dy chng st ta tnh cho pha

c in p kh quyn t ln ln hn tc l pha c h s ngu hp nh hn.

+ tnh sut ct do st nh vo nh ct ta phi xc nh qu in p

kh quyn t ln cch in cc pha v ta tnh vi trng hp nguy him tcl c Uc(a,t) ln hn.

II.TNH TON THAM S KHI ST NH LN NG DY 110KV

1.S ln st nh vo ng dy:

Cng thc tnh: LnhN ngscstb ...),,(3109060=

Trong : + hcstb=21 m

+ L - chiu di ng dy ti in ly 110 km

+ nngs- s ngy st nh trong nm ly 100ngy

Ta c: 189126=10010010219060= 3 ...),,(N ln / nm.

M: N = N+ Nc +NKV

Trong : N- s ln st nh vng qua dy chng st vo dy dn .

Nc- s ln st nh vo nh ct v ln cn nh ct.

NKV- s ln st nh vo khong vt.

2. S ln st nh vng qua dy chng st no dy dn.

c trng cho s xc sut 2Vkhng nhng ch ph thuc vo gc bo

vma cn tng theo chiu cao ct c tnh l:

490

=hc

U

lg

l gc bo v tnh vi pha A1 - 2 = 25,460

hc l chiu cao ca ct = 25m

aUU 32 1062=5852=49025

= .,,lg25,46


74/99

74

Vy s ln st nh vng qua dng dy chng st vo pha A12 l:

mnkmlnNUN //(,,.. 100490=6210189== 322

Ta ly N = 189 l gi tr ln nht tnh.

3. S ln st nh vo nh ct hoc ln cn v khong trt

)/(, mKmnlnN

NN KVdc 100594=2189

=2

==

4. Tnh sut ct do st nh vng qua dy chng st vo dy dn.

Theo cng thc: UNn Pddd ..2=

Vp l xc sut phng in do qu in p ng dy khi c st nh

vo dy dn.

l xc sut hnh thnh h quang.

* Tnh Vp : Khi st nh vo dy dn mch ca khe st ghp ni tip

vi tng tr sng ny c tr s l Zdd/2 (ta gi s st nh vo chnh gia

ng dy).

Ta c:2

=2

2+

= 00

0 Scdd

ddcc

IIZZvi

ZZ

ZII .

in p trn dy khi st nh vo l:

4= ddSdd ZIU .

Khi in p trn dy dn Udd vt qua mc in xung kch ca chui

cch in %50 UUdd th dy n phng in trn chui cch in.

%504U

ZI ddS nn

dd

SZ

UI %

. 504

Khi xc sut phng in khi qu p trn ng dy chnh l xc sut

cho:

8650===

4=

4

612484126

504

126

504

50

50

,,.,%

,

%

%

%

U

Z

U

dd

Spd

dd

S

dd

Z

UIfV

Z

UI

ll

Vi Zdd l tng trsng pha A1-2


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75

* Tnh : tr s ph thuc vo t scs

LVLV

l

UE =

+ ULV- in p lm vic

+ lcs- chiu di chui s.

KvU

U dddmLV 2157=110143

2

3

2=

2

3

2= ,.

,...

cp in p 110 Kv ta chn loi s cch in cho ng dy l loi

s 54 , c 7 bt s.

mlcs 21= ,

Ta c: )/(,,

,kmkv

l

UE

cs

lvLV 6847=21

2157==

T bng xc sut hnh thnh h quang ( trang 205 - sch k thut in

cao p) ta c

Bng 3-2:

Elv 50 30 20 10

0,6 0,45 0,25 0,01

Theo bng s liu trong bng ta vc th biu din quan h ELV v .

Sau ELV ta xc nh c gi tr tng ng l ELV= 47,68(kv/km) =0,58.

Thay vo cng thc:

260=58049== ,,.,.. oVNn pddd (ln/100 km.nm)

Ta thy rng gim ndd c th gim bng cch tng cng chui cch

in ... hoc gim N bng cch gim gc bo v tng cao dy chng st.

Hnh 3-3


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76

5. Tnh sut ct do st nh vo khong vt:

Khi c st nh vo dy chng st trong khong th ti v tr st nh

coi nh dng in st s chia u cho 2 phn ca dy chng st.

Gi thit l sng st c dng xin gc, phng trnh dng in do st l:

Is= at nu t < Ts

Is= I nu dcTt

Khi tnh ton ta phi tnh vi cc gi tr khc nhau ca dng st vi

a = 10,...100 )(s

KA v t = 1,2 ...10 )( s v gi tr 11=c

R .

Khi c st nh vo khong vt ca dy chng st s sinh ra cc in

p l in p tc dng ln cch in khng kh gia dy dn v dy chng st,

in p tc dng ln cch in chui s. Thnh phn in p tc dng ln

cch in khng kh ph thuc vo dc dng in st, v khong cch gia

dy dn v dy chng st. Trong thit k v trong xy dng ngi ta t

khong cch gia dy dn v dy chng st kh ln trnh chm dy nn

kh nng phng in trong khong vt do thnh phn in p tc dng ln

cch in khng kh ln hn mc cho php, ng thi nu c th xc sut hnh

thnh h quang l rt nh, do kh nng ct in ng dy l khng ng

k, v vy trong tnh ton ta b qua thnh phn ny.

ELV40302010 50

0,1

0,25

0,45

0,57


77/99

77

a. in p tc dng ln cch in ca chui s.in p tc dng ln chui s khi st nh vo khong vt ca dy

chng st l:

LVCSC

ctcd Uk

dttdisLatRU +1

2+

2= )()(.)(

- Dng in st c dng is(t) = at nn c:LV

cs

cc

cd Uka

LatR

tU +1

2

+2

= )(..

)(

Trong cc thnh phn ca Ucc xc nh nhphn sau.

b. in p lm vic ( tnh phn trc)

)(,.,

. kvULV 2157=1101432

3

2=

c. in p tinh ct khi stnh vo khong vt khi c nh hng cah quang.

2

+2

1=a

LatR

kU cscc ..

)(

Trong : a- dc ca dng in st.

Lccs- in cm ca thn ct in tnh t mt t ln n im

treo dychng st v Lccs= Lo.hc. Vi Lo l in cm n v ca thn ct:

)(,m

HL 60=0 ;

hc- chiu cao ct in.

HLcsc 15=2560= .,

Rc- in trni t ca ct ng dy 11=cR

k- h s ngu hp ca dy chng st i vi dy dn c nh hng ca

h quang ( k ca dy dn pha A K pha B).


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78

Trong cng thc trn ta thy t l nghch vi K, vy ta s ly gi tr K

nh hn tnh vi U ln, ta c:

KA1-2= 0,275.

KB1-2= 0,183.KC1-2=0,131.

V ta ly KC1-2 l h s ngu hp tnh ton. T ta c:

2157+15+1143450=

2157+15+43450=

2157+

2

15+2

13101=

+1

2

+2

=

,)(.,

,).(.,

,.

),(

)(.

)(

ta

tRa

aatR

Uka

LatR

atU

c

c

LVcsc

ccd

Nh vy khi thay 11=R vo ta c biu thc tnh Uc theo a v t ta

c kt qu sau:

at

1)( s

2)( s

3)( s

4)( s

5)( s

6)( s

7)( s

8)( s

9)( s

10)( s

10 170,18 217,98 265,77 313,57 361,36 490,16 456,96 504,75 552,54 600,34

20 283,15 378,74 474,33 569,92 665,51 761,10 866,69 952,28 1077,87 1143,36

30 396,12 539,51 862,99 826,28 969,66 1113,05 1256,43 1399,82 1543,20 1686,59

40 509,09 700,27 891,45 1082,63 1273,81 1464,99 1656,17 1847,35 2038,53 2229,71

50 622,06 861,04 1100,01 1338,99 1577,96 1816,94 2055,91 2294,89 2533,86 2772,84

60 735,03 1021,80 1308,57 1595,34 1822,11 2168,88 2455,65 2742,42 3029,19 3315,96

70 848,00 1182,57 1517,13 1851,70 2186,26 2520,83 2855,39 3189,96 3524,52 3859,09

80 960,97 1343,33 1725,69 2108,05 2490,41 2872,77 3255,13 3637,49 4019,82 4402,21

90 1073,94 1504,10 1934,25 2364,41 2794,56 3224,72 3654,87 4085,03 4515,18 4945,34

100 1186,91 1664,86 2142,81 2620,76 3098,71 3576,66 4054,61 4532,56 5010,51 5488,46

T gi tr 11=cR ta c bng c tnh Vc(a,t) ph thuc vo thi gian

v dc u sng st a. T bng ny ta vc th Vc theo a,t v v

c c tnh phng in ca chui s.


79/99

79


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80

th gi tr ca Uc theo a v t vi 11=cR vi st nh vo khong

vt.

Ta c bng sau:

t(MS) 1 2 3 4 5 6 7 8

Ucs(KV

)

1020 930 860 818 790 780 770 770

Bng gi trin p phng in ca chui s Ucs(KV)

T th ta xc nh c cc gi tr ai v ti l giao im ca Uc vi

c tnh V - S ca chui s, do ta s xc dnh c cc cp thng s nguyhim (Ii;ai). Sau ta xc nh c ng cong nguy him I = f(a).

d. Xc sut phng in Vp: l xc sut cp thng s (I,a) ca

phng in st thuc min nguy him.

Vp= f{I,a} thuc min nguy him 3 hay

dVp=f{a = ai}* { }iIIf m

{ } 11261 == rIIf

I

i,

l ( r1 l xc sut dng in st ln hn

dc i Ii no )

aaiaii drdaadafaaf =+== )()( ( dra l xc sut dng in st

ln hn dc ai no )

9101

== ,)(I

ia aafr l

T ta xc nh c dVp= r1dra hay Vp= Str1dra, ta chia on t0

lm thnh thnh phn nh khi :

= aipd rrV vi 1+= aiai VVV


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81

T th Uc vi 11=cR ta xc nh c cc cp gi tr (a,t) t xc

nh c I, Vi, Va, aV nh trong bng sau:

a(KA/ )s 10 20 30 40 50 60 70 80 90 100

T( )s 11,8 6,7 3,7 2,8 2,3 1,8 1,5 1,2 0 0

I(KA) 118 134 111 112 115 108 105 96 0 0

V1(10-1 0,11 0,05 0,14 0,14 0,12 0,16 0,18 0,25 0 0

Va 0,0019 0,0005 0,0037 0,0034 0,0026 0,0049 0,065 0,0149 0 0

)( 210aV 1,0014 0,9968 1,0003 1,0008 0,9977 0,9984 0,9976 1,0149 0 0

)( 610aVV1

110,15 49,84 140,04 140,11 119,72 178,49 178,49 253,73 0 0

Vi 11=cR ta c: 61 10821151== .,.. apd VVV

Sut ct do st nh vo khong vt:

06530=6010821151594== 6 ,,..,.,.. VNN pddcKV (ln/100km.nm)

Do ta c th c th I = f(a) l gii hn ca min nguy him:

a )( sKV

Min nguy him

I(kA)


82/99

82


83/99

83

6. Tnh ton sut ct do st nh vo nh ct v ln cn nh ct.

Ta xt trng hp st nh vo nh ct: khi dng in si vo b

phn ni t ca ct in, ng thi mt phn nh si vo b phn ni t

ca cc ct ln cn. Khi c qu p kh quyn tc dng ln cch in ng

dy th i vi cc pha khc l khng ging nhau, ta phi tnh ton in p t

ln cch in tng pha v xt trng hp c gi tr ln nht.

a. in p t ln cch in cc pha.Gi s ta tnh Uc (a;t) vi 1 gi tr a = 30 )( s

KV V t = 5 )( s vi

11=cR , khi cch in ln mi pha c tnh bi cng thc sau:

[ ] [ ]t

ticcs

c

dd

ctcstddcc

d

culvtacd d

dKLLKMMakRiUUU x

)(

)()();( )(. ++1++=

Trong : + ULV- thnh phn in p lm vic ca ng dy 57,12Kv.

+ K- h s ngu hp c nh hng ca h quang vi pha.

KA1-2= 0,257; KB1-2= 0,183; KC1-2= 0,131.

+ ddcL - tr sin cm ca phn ct in tnh t mt t ti

cao ca ng dy: ddcL = L0.hdd.

+ L0- in cm n v ca thn ct in ta ly

mHL 60=0 ,

+ hdd- treo cao ca dy dn pha:

A1-2: hdd= 20,8 ddcL = 0,6.20,8 = 12,48 H

+ B1-2: HLmh ddcdd 6810=81760=817= ,,.,,

C1-2: hdd= 14,8 m ddcL =0,6.14,8 = 8,88 H


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84

+ cscL - tr sin cm phn ct in tnh t mt t ti treo cao

dy chng st.

HhLL cscsc 15=2560== 0 ,. + Mdd(t)- h cm gia khe phng in st

vi mch vng dy dn v t c tnh:

1+

2

+1

+20=

h

H

h

h

H

HVhM

dd

tddtdd

ln

)(ln,)(

. V- vn tc pht trin vi phng in ngc khe vi Vt= .C

- tc tng i phng in ngc ca st (= 0,3)

C- tc truyn sng trong khng kh ( C = 300s

m )

Vt= 0,3.300.5 = 450 ( sm ) ( ly t = 5)

. H = hc+ hdd:

Pha A1-2: H = 25 + 20,8 = 45,8 (m)

B1-2: H = 25 + 17,8 = 42,8 (m)

C1-2: H = 25 + 14,8 = 39,8 (m)

. h = hc- hdd:

Pha A1-2: h =25 - 20,8 = 4,2 (m)

B1-2: h = 25 - 17,8 = 7,2 (m)

C1-2: h = 25 - 14,8 = 10,2 (m)

Vi pha A1-2:

HMAdd 9811=

1+

24845

820224

84530+1

845+4582020=21 ,

,

,ln

,.

,

,),(

,ln,.,

Vi pha B1-2:

HMBdd 6410=

1+

27

842

8172

27

84230+1

842+45081720=21 ,

,

,ln

,.

,

,),(

,ln,.,

Vi pha C1-2:

HMCdd 765=

1+

210839

8142210

83930+1

839+45081450=21 ,

,

,ln

,.

,

,),(

,ln,.,

+ Mcs(t)- trcm gia mch khe st v mnh dy chng st c tnh:


85/99

85

H

hVthcM ctcs 215=

1+

2530+12252+510030

2520=

1+

+12

2+10= ,

),(

...,ln.,

)(ln,)(

+ Udc- thnh phn in cm ng ln ng dy v cc pha gy ra bi

din trng ca cc in tch khe st v trong ct.

Hhh

HvthVthvt

ha

h

hkU

c

cdd

dd

csdcu

.)(

))(()(ln

..,).(

2+1

+++101=

Vi pha A1-2:

KvUAdcu 655855=845422530+1

845+53003024+53003025+530030

308203010

82025

25701=2

21 ,,...),(

),..,)(,..,()..,(ln

,

,..,)

,.,(

Vi pha B1-2:

KvUBdcu 096756=842272530+1

842+59027+59025+590

308173010

81725

18301=2

21 ,,.,..),(

),.)(,.().(ln

,

,..,)

,.,(

Vi pha C1-2:

KvUCdcu 214643=8392102530+1

839+590210+59025+590

3081410300

14825

13101=2

21 ,,.,..),(

),.)(,.().(ln

,

,.,).,(

+ is lthnh phn dngin st i vo trong thn ct c xc nh bi

cng thc:

t

c

tcscs

tsR

MLai 21

2

2= l(. )()( )

Vi: + Lcs- in cm ca dy chng stC

LZL cscs

.=

+ L- l chiu di khong vt L = 200 m.

+ Zcs- tng trsng ca dy chng st Zcs= 410,998 )(

+ C- tc truyn sng C = 300s

m

HLcs 247=300200998410

=.,


86/99

86

+ 0720=152+274

112=

2+

2=2 ,

.

.csccs

c

LL

R

Vy ta c: KAi tc 12112=1112215227430

= 50720 ,).(.

,.. .,)( l

+ bin thin dng in st : tc

tcscs

t

tic

R

MLa

d

d.)()(

...

222

2= l

Thay vo ta c: 718=0720112

215227430= 50720 ,.,.

.

,.. .,)(l

t

tic

d

d

By gita thay cc tham s tnh c v cc tham s cho trc

sts

KAaRc 5=30=11= ;; vo cng thc tnh Uc ta tnh c in p t

ln cch in cc pha:

in p t ln cch in pha A1-2

),( taUAcd21 = 57,12 + 855,655 + 102,68.11(1 - 0,257) +30

[11,98 - 0,257.15,2] + (12,48 - 0,257.15)18,7 = 2155,474 Kv

in p t ln cch in pha B1-2

),( taUBcd21 = 57,12 + 756,096 + 102,68.11( 1- 0,183) + 30

[10,64 - 0,183.152] + (10,68 - 0,183.15) 18,7 = 2120,138 Kv

in p t ln cch in pha C1-2

),( taUCcd21 = 57,12 + 643,214 + 102,68.11 (1- 0,131) + 30

[5,76 - 0,131.15,2] + (8,88 - 0,131.15).18,7 = 1924,227 Kv

Qua tnh ton trn ta thy in p t ln cchin pha A1-2 l ln

nht so vi cc pha khc nn ta ly pha A1-2tnh ton in p tc dng ln

chui s khi st nh vo nh ct ng dy in.

b. in p t ln cch in pha A1-2 trong trng hp vo nh ct.in p t ln cch in pha A1-2c tnh bi cng thc:

cscctc

dcLVtcd KVRiUUUU +++= )(


87/99

87

Trong : ULV= 57,21 KV ( tnh)

d

cU- thnh phn in p cm ng in.

982585

845+9024+9025+90794=

845242530+1

845+9024+9025+90

3082010

82025

25701=

+1

+++101=

2

2

,

),)(,()(ln,

,.,..),(

),)(,()(ln

,

,..,)

,.,(

..)(

))(()(ln

..,).(

ttta

tttaHhh

Hvthvthvt

ha

h

hkU

c

cdd

dd

csdc

Vi cc gi tr ca a = 10, 20, 30.100s

KA v t = 1, 2, 3.10 (s)

Thay Uc ta c kt qu bng sau:

A t 1 2 3 4 5 6 7 8 9 10

10 148,49 204,41 239,1 263,75 285,12 301,75 315,92 328,26 339,19 349,00

20 296,97 408,83 478,24 527,49 570,24 603,51 631,85 656,53 678,39 698,00

30 445,46 613,25 957,65 791,25 855,36 905,26 947,77 984,79 1017,58 1047,00

40 593,95 817,66 1197,06 1054,99 1140,48 1207,02 1263,69 1313,05 1356,77 1396,00

50 742,44 1022,08 1436,47 1318,75 1425,59 1508,77 1579,62 1641,31 1695,96 1745,00

60 890,92 1226,49 1675,88 1582,49 1710,71 1810,53 1895,54 1969,58 2035,16 2094,01

70 1039,41 1430,91 1915,29 1846,25 1995,83 2112,28 2211,48 2297,84 2374,35 2443,01

80 1187,89 1635,33 2154,71 2109,99 2280,95 2414,04 2527,40 2626,10 2713,54 2792,01

90 1336,39 1839,74 2154,71 2373,75 2566,07 2715,79 2843,33 2954,37 3052,73 3141,01

100 1484,87 2044,16 2394,12 2637,49 2851,19 3017,55 3159,25 3282,63 3391,93 3494,02

t

cU l thnh phn in cm t.

Ta c: )( .. tddt

icddc

tc Ma

d

dLU +=

Trong : ddcU - in cm ct tnh t mt t n x treo dy dn.


88/99

88

t

ic

d

d- tc bin thin ca dng in st nh vo nh ct, gi tr

ny ph thuc vo s bin thin l c phn x hay cha c t ct ln cn

trv.

1+2405459

845+906164= ,

,

,.(ln,)(

tM tdd

Thay cc gi tr t = 0, 1, 2, 3.10 s vo cng thc Mdd(t) ta c kt qu

bng sau:

T 1 2 3 4 5 6 7 8 9 10

Mdd(t) 6,592 8,707 10,102 11,145 11,98 12,673 12,267 13,783 14,25 14,666

Thnh phn in p ic Rc:

- Khi cha c phn x t ct ln cn trvc

Lt 2

Vi L l chiu di khong vt = 200 m

C l vn tc truyn sng = 300 s

st 331=3002002

,.

+ Dng in trong ct ic(t): ta c s thay th nh hnh v:

2

2+=

l

ZMZ

RZ

ai cstcstcs

ccs

taC )()(),(

i 4314=152

112+998410=

2

2+=1 ,

.

.,csc

ccs

L

RZ


89/99

89

Thay vo biu thc tnh ic(a,t) ta c bng kt qu

Tc bin thin:

t

aa

t

aZtRZ

a

d

dcs

ccst

ic 94920=998432

998410=112+998410=2+=

,

,

,

).,(.)(

Gi trt

ic

d

dc tnh trong bng kt qu .

Ta c s thay th:

i:C

LZL cscs

.=

Zcs- tng trsng ca dy chng st khng c nh hng ca h quang

HLcs 198356=300200297534

= ,.,

Is

Rc

i

Zcs

2

crq

c2i

Is

Rc

i

Zcs

2

c

rq

c2i

Lcs

2Lc

cs


90/99

90


91/99

91

+ Dng in i trong ct ic(a,t) l:

( )( )

0570=

152+198356

112=

2+

2=

122

=1

2

2

,

.,

.

)()

CS

CCS

c

t

cscs

c

c

LL

Rvi

etMLR

atai

Gi tr MCS(t) bng sau:

1+65

50+905=

ttMCS

ln)(

Bng 3.7

T 1 2 3 4 5 6 7 8 9 10

MCS(t)

9,19 9,24 9,28 9,29 9,32 9,33 9,34 9,35 9,36 9,37

Bng 3.8

a(KA/ )s 10 20 30 40 50 60 70 80 90 100

T( )s 11,3 4,9 3,5 2,4 1,6 1,3 0 0 0 0

I(KA) 113 98 105 9,6 80 78 0 0 0 0

V1(10-1) 0,132 0,234 0,179 0,253 0,466 0,504 0 0 0 0

Va .10-3 0,031 0,125 0,066 0,149 0,649 0,780 0 0 0 0

)( 210aV 0,906 1,059 0,917 0,5 0,869 1,78 0 0 0 0

)( 610aVV1 11,96 24,78 16,41 12,65 40,49 89,71 0 0 0 0

Ta c: 02220=6010196189==10196== 66 ,,..... VNnVVV pdcaiPd(ln/100Km.nm)


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92

7. Tnh xc sut phng in khi st nh vo nh ct v ln cnnh ct.

34150=2540+06530+02220=++= ,,,,ddKVc nnnn (ln/100km.nm)

ch tiu chng st ng dy ti in

932=341501

=1

= ,,n

m (ln /100km.nm)

* Kt lun : ta thy rng sut ct in trn ng dy 110KV l c th

chp nhn c (khng cao qu), tham s ca ct l m bo ch tiu v sut

ct cho ng dy khi c st nh vo n.

Vy gim s ln ct in do st c th dng cc bin php sau y.

- Gim xc sut phng in VP bng cch gim in trni t ctin v tng cng cch in ng dy.

- Gim tr s gc bo v gim kh nng st nh vo dy dn. Trng

hp st nh vo dy dn c xem l nguy him nht. V rt d gy phng

in, nh ng dy 110KV xc sut phng in c th t ti 80%,

ng dy in p cao hn xc sut ny vn cn gi cc tr s kh ln. Tuy

nhin cn phi bo v se yu cu ct phi cao v nh th s lm tng gi

thnh.

Bng gi tr ca d-it/ dt =0,949 a/t

t

a

10 20 30 40 50 60 70 80 90 100

1 9,492 18,98

4

28,47

6

37,96

8

47,46

0

56,95

2

66,44

4

75,93

6

85,42

8

94,92

0

2 4,746 9,492 14,23

8

18,98

4

23,73

0

28,47

6

33,22

2

37,96

8

42,71

4

47,46

0

3 3,164 6,328 9,494 12,65

6

15,82

0

18,98

4

22,14

8

25,31

2

18,47

6

31,64

0

4 2,373 4,746 7,121 9,492 11,86

5

14,23

8

16,61

1

18,98

4

21,35

7

23,73


93/99

93

5 1,898 3,797 5,696 7,594 9,492 11,39

0

13,28

9

15,18

7

17,08

6

18,98

4

6 1,582 3,164 4,747 6,328 7,910 9,492 11,07

4

12,65

6

14,23

8

15,82

0

7 1,356 2,712 4,069 5,424 6,780 8,136 9,492 10,84

8

12,20

4

13,56

0

8 1,187 2,373 3,560 4,746 5,933 7,119 8,306 9,492 10,67

9

11,86

5

9 1,055 2,109 3,165 4,219 5,273 6,328 7,383 8,437 9,492 10,54

7

10 0,949 1,898 2,848 3,797 4,746 5,695 6,644 7,594 8,543 9,492

BNG GI TR CA [ ]142,0M2t998,410998,432

a)ait(i )t(csc =

t

a1 2 3 4 5 6 7 8 9 10

10 9,064 18,554 28,044 37,535 47,026 56,517 66,009 75,500 84,992 94,483

20 18,128 37,108 56,088 75,071 94,052 113,035

132,017

151,000

169,983

188,966

30 12,192 55,661 84,131 112,60

5

141,07

7

169,55

2

198,02

6

226,50

0

254,97

5

283,44

9

40 36,257 74,115 112,17

5

150,14

1

188,10

3

226,06

9

264,03

5

302,00

0

339,96

6

377,93

2

50 45,321 92,769 140,21

9

187,67

6

235,12

9

282,58

6

330,04

4

377,50

1

424,95

8

472,41

5

60 54,385 111,32

3

168,26

3

225,21

2

282,15

5

339,10

4

396,05

2

453,00

0

509,94

9

566,89

8

70 63,449 129,87

6

196,30

7

262,74

7

329,18

1

395,62

1

462,06

1

528,50

1

594,94

1

661,38

1


94/99

94

80 72,513 148,43

0

224,31

5

300,28

2

376,20

6

452,13

8

528,06

9

604,00

1

679,93

3

755,86

5

90 81,577 166,98

4

252,39

4

337,81

7

423,23

2

508,65

5

594,07

8

679,50

1

764,92

4

850,34

8

100 90,642 185,53

8

280,43

8

375,55

3

470,25

8

565,17

3

660,08

7

755,00

2

849,91

6

944,83

1


95/99

95

TI LIU THAM KHO

1. K thut in cao p ca V VIT N

2. Hung dn k thut in cao p ca NGUYN TH MINH CHC

3. Nh my in v trm bin p ca NGUYN HU KHI

4. Chng st cho nh v cng trnh ca VIM SUM

B GIO DC V O TOTRNG H BCH KHOA H NI

CNG HO X HI CH NGHA VIT NAMc lp - Tdo - Hnh phc

----------*******-------------

NHIM V THIT K K THUT

Ging vin hng dn : TS Nguyn nh Thng


96/99

96

H v tn sinh vin :on Vn Minh

Ngnh hc : H thng in

I/ - u thit k:

TNH TON THIT K V CHNG V CHNG ST CHO NG DY V

TRM BIN P 110/22KV.

II/- Dliu ban

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