ki thuat cao ap qua dien ap trong he thong dien

7/28/2019 Ki Thuat Cao AP Qua Dien AP Trong He Thong Dien

1/114

AI HC BCH KHOA Tp.HCMKHOA IN IN TB MN H THNG INNhom mon hoc: CAO AP VAT LIEU

Mn hc

K THUT CAO PQU IN P TRONG H

THNG IN

________________________________________________


2/114

Trao i trc tuyn ti:

http://www.mientayvn.com/chat_box_li.html
http://www.mientayvn.com/chat_box_li.htmlhttp://www.mientayvn.com/chat_box_li.html


3/114

Ti liu tham khaoK thut cao p II TS. HONG VIT

Bi tp KTCA TS. H VN NHTCHNG

Extra High Voltage AC Transmission

Engineering ( 3rd edition)Rakosh DasBegamudre


4/114

MC TIU CA MN HC

NGUN GC, C IM V TC HICA CC DNG QU IN P XYRA TRONG H THNG IN

CC BIN PHP NGN NGA,HN CH TC HI CA QU IN PI VI CC THIT B TRONG H

THNG IN


5/114

QU IN P(OVERVOLTAGE) ?

L THNH PHN IN P C THI

GIAN BIN THIN RT NGN ( 10-6 s)V BIN LN


6/114

NGUN GC SINH RA QUIN P TRONG H THNG

IN?

HIN TNG PHNG IN ST

QU TRNH NG CT CC THIT BTRONG H THNG IN

CC S C XY RA TRONG H THNG


7/114

CHNG I:

HIN TNG PHNG IN ST

Set la hien tng phong ien trong kh quyen giaam may dong mang ien tch vi at hoac gia cacam may dong mang ien tch trai dau nhau. ienap gia may dong va at co the at ti tr so hangchuc, tham ch hang tram trieu volt. Chieu dai trungbnh cua khe set khoang 3 5 km, phan ln chieu

dai o phat trien trong cac am may dong.


8/114

1.1 NGUN GC SINH RA PHNG IN ST


9/114

1.2 CC DNG PHNG IN ST


10/114

Phng

in st

my-t

Phng inbn trong

m my

Phng in

my-my


11/114

1.3 MT S HNH NH PHNG IN ST


12/114



13/114



14/114



15/114



16/114



17/114



18/114



19/114



20/114



21/114



22/114



23/114



24/114



25/114

Giai oan 1Thoat tien xuat phat t may dong mot day sang mkeo dai tng t gian oan ve pha mat at vi toc otrung bnh khoang 105 107 m/s. ay la giai oanphong ien tien ao tng t c goi la tien ao

bac.

1.4 CC GIAI ON PHNG IN ST


26/114

Giai oan 1Kenh tien ao la mot dong plasma mat o ientch khong cao lam, khoang 1013 1014 ion/m3.Mot phan ien tch am tran vao kenh va phanbo tng oi eu doc theo chieu dai cua no.



27/114

Giai oan 1Di tac dung cua ien trng cua ien tch am tren

am may va trong kenh tien ao, vung at ben dise co s tap trung cac ien tch cam ng trai dau.V tr tap trung ien tch cam ng co the ngay bendi am may, hay nhng ni co ien dan cao



28/114

Giai oan 1Trong giai oan au, hng phat trien cua cac tia tienao la ngau nhien tuan thu theo nguyen tac la phattrien theo hng co cng o ien trng cao nhat



29/114

Giai oan 1Khi kenh tien ao at en mot o cao nhat nh,goi la o cao nh hng, th hng phat trien cua

tia tien ao se chu anh hng cua cac vat bendi mat at, ni co s tap trung ien tch camng caoDo o, v tr o bo cua dong set co tnhchon loc



30/114

Giai oan 1 cac v tr tap trung ien tch trai dau vimat o cao, cng o ien trng cuc botrong khong kh tai o cao lam xuat hien sion hoa khong kh, tao nen dong tien ao phattrien t ben di hng len am may, chieudai cua kenh tien ao ngc nay co the lenen vai tram m. ay chnh la qua trnh phongien on set, tao ieu kien nh hng dongset vao v tr o



31/114

Giai oan 2Giai oan phong ien chnh, hay phong ienngc.Khi kenh tien ao xuat phat t am may dongtiep can mat at hay kenh tien ao ngc,cng o ien trng trong khoang cach kh

tang cao gay ion hoa manh liet khong kh danen s hnh thanh dong plasma mi, co mat oien tch tang cao hn nhieu so vi ban au1016 en 1019 ion/m3.



32/114

Giai oan 2Cac ien tch cam ng di matat tran len trung hoa cac ientch trong kenh tien ao t ammay.Cac ien tch cam ng nay tieptuc i theo ng cua phong ientien ao ban au, tiep tuc hnglen am may, hnh thanh nen

kenh phong ien chnh



33/114

Giai oan 2Mat o ien tch trong kenhphong ien chnh rat cao, lam ot

nong manh liet kenh phong iennay, nhiet o co the len ti 2-3chuc ngan o C(gap 3 lan nhiet obe mat mat tri). Chnh v vay,kenh phong ien chnh sang choichang, ma ta thay di dang cactia chp.



34/114

Giai oan 2Vi lng nhiet khong lo nay, lpkhong kh xung quanh kenh phong

ien chnh b ot nong, gian not ngot tao ra nhng t song ammanh liet, ma ta goi la sam



35/114

Giai oan 2Khi kenh phong ien chnh len

en am may dong, dong set cogia tr ln nhat, ay chnh la dongngan mach khoang cach kh giamay va at, co gia tr trong

khoang t 1kA en hang tram kA



36/114

Giai oan 3Giai oan ket thucKhi kenh phong ien chnh len

en am may dong, cac ien tchcam ng t mat at len theo, tranvao va trung hoa cac ien tch traidau tren am may, cac ien tch

(am) con tha tren am may setheo kenh phong ien chay xuongmat at.Dong set co tr giam dan



37/114


1-Giai on phng in tin o

1


38/114

.4CC

G

IAIONP

HNGINST(20-50ms)2-Giai on phng in ngc 3-Giai on kt thc phng in


39/114

Phng th nghim nghin cu v hin tng phng in st


40/114

1.5 CC THNG S DNG IN ST


41/114

Bieu thc toan hoc c viet nh sau

Trong o : I : hang so co th nguyen la dong ien (kA).1, 2 : hang so co th nguyen la thi gian (s).

s : thi gian au song (s). s : thi gian song (s).


I( / )m

ds

a kA s

o doc au song cua dong set


42/114

Xac suat xuat hien dong set co bien o ln hn Im(kA)

26

13

,

,

m

mm

I

I I

e DBv

e DN


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90

10

20

30

40

50

60

70

80

90

100

Vis

Is(kA)

Dong bang

Mien nui


43/114

Xac suat xuat hien dong set co o doc au song a(kA/s)

15,7

7,82

,

,

a

a a

e DB

v

e DN


0 0.1 0.2 0.3 0.4 0.5 0.60

10

20

30

40

50

60

70

80

90

100

Va

a(kA/s)

Dong bang

Doi nui


44/114

1.6 CNG HOT NG CA ST V MT ST

Cng hot ng ca set la so ngay co dong settrung bnh trong nam: n (ngay set/nam)Vung cc: 2-3, on i: 30-50, nhiet i: 75-100, xchao 100-150 (ngay set/nam)

Mat o set la so lan set anh trung bnh tren 1 n vdien tch mat at trong 1 ngay co dong set: m(lan/km2.ngay set)

Mat o set trung bnh trong nm:m.n (lan/km2/nm)


45/114


46/114

S li i d h


47/114

S liu v mt st ti cc a danh Vit Nam (2007)

S li t t t i d h


48/114


S li t t t i d h


49/114


S li t t t i d h


50/114


S li t t t i d h


51/114


S li t t t i d h


52/114

S liu v mt st ti cc a danh Vit Nam

S liu v mt st ti cc a danh


53/114



54/114

THE END


55/114

AI HC BCH KHOA Tp.HCMKHOA IN IN T

B MN H THNG IN

Mn hc

K THUT CAO P


56/114

9/9/2011 2

Trao i trc tuyn ti:



57/114

CHNG II

BO V CHNG ST NH TRCTIP CHO H THNG IN

/ / / / / // / / / / /

R X

(1)

(2)

(3)

Bo phan thu set

(100mm2)

Bo phan dan dong set

(50mm2)

Bo phan noi at


58/114

M hnh A.Kopian:


59/114

p

H

h

R=3,5h

Khu vc c xc sut100% st nh vo ct

thu st: R=3,5h

M hnh A.Kopian:


60/114

p

rx

Phng php thc nghimtrn m hnh ny ara c cng thc xc

nh phm vi bo v cact thu st s c trnh

by phn sau

M hnh A.Kopian:


61/114

M hnh A.Kopian:


62/114


63/114

I. CACH XAC NH PHAM VI BAO VE CUA CTS1. Pham vi bao ve cua mot CTS(


64/114

I. CACH XAC NH PHAM VI BAO VE CUA CTS

1,6 x

x

h hh p

h h

xr

p = 1 khi h 30m.

30p = khi 30m < h < 60m.

h

1. Pham vi bao ve cua mot CTS (


65/114

1,5 (1 )

0,8

xx

hr h p

h

0,75 (1 )xxh

r h ph

, khi hx 2h/3 rx = (1,5h 1,875hx).p

,kh ihx > 2h/3 rx = (0,75h 0,75hx).p

I. CACH XAC NH PHAM VI BAO VE CUA CTS1. Pham vi bao ve cua mot CTS (


66/114

0,2h

h

hx

2h/3

0,75ph

1,5ph

1,5 (1 )

0,8

xx

hr h p

h

0,75 (1 )xxh

r h ph

, khi hx 2h/3 rx = (1,5h 1,875hx).p

,kh ihx > 2h/3 rx = (0,75h 0,75hx).p

I. CACH XAC NH PHAM VI BAO VE CUA CTS1. Pham vi bao ve cua mot CTS: (


67/114

I. CACH XAC NH PHAM VI BAO VE CUA CTS1. Pham vi bao ve cua mot CTS: (>60m)

St khng nhng nh vo nh m cn nh vo phn thn ct gnnh

0,5( 60)h h

i vi ct thu st c chiu cao t 60m n 100m:

i vi ct thu st c chiu cao t 100m n 250m:

0,2h h

Nu chiu cao hiu dng ha h, th phm vi bo v ca ct thu stc tnh vi chiu cao hiu chnh h=h-h

2. Pham vi bao ve cua hai CTS


68/114

7

a

p

p7a

0,2h

hhx

2h/3

0,75hp

1,5hp

a/2a/2rx

7

a

hh0

RCot thu set Cot thu set

rx

rxr0x

r0x

Trng hp hai cot co o cao bang nhauTa co the xac nh c rang neu hai CTS at cach nhau mot khoang

cach a th chung co the bao ve vat co o cao h0 at gia chung, vi h0

c xac nh theo cong thc: h0 = h

a/7p



69/114

0,75h 1.5h0,75h

rx

xhxh

rx

1.5h 1.5h O 0,75h O 0,75h O O1.5hrOX

R

a

ho

Trng hp hai cot co o cao bang nhau



70/114

Neu hai cot thu set co o cao khac nhau, v du h1 < h2 th phamvi bao ve cua chung c xac nh nh sau

- Pham vi bao ve pha ngoai hai cot thu set giong nh pham vi

bao ve cua tng cot rieng le.- Pham vi bao ve gia hai cot thu set co c bang cach quanh cot thap (h1) ve mot ng thang ngang, no cat ng sinhcua pham vi bao ve cua cot cao h2 mot iem , iem nay c coinh nh cua cot thu set gia tng h = h1 va khu vc bao ve giacot thap h va h1 cach nhau khoang a nh gia hai cot co o caobang nhau.

Trng hp hai cot co o cao khac nhau

3. Pham vi bao ve cua he nhieu CTS (n>2)


71/114

Khi cong trnh can bao ve chiem mot dien tch rong ln thngi ta thng dung mot he thong nhieu cot thu set e bao

ve. e xac nh pham vi bao ve, ngi ta chia he thong cotthu set thanh tng nhom 3 hoac 4 cot thu set. Ben ngoai dientch cua a giac i qua chan cac cot thu set ( hnh tam giachoac hnh ch nhat ) pham vi bao ve c xac nh nh gia

tng oi cot thu set vi nhau. Con tat ca cac thiet b co o caoln nhat hx at trong dien tch cua a giac se c bao ve antoan neu ieu kien sau c thoa man :

D 8 (h hx ) pTrong o:h : o cao cua cot thu set.hx : o cao ln nhat cua cao trnh.D : ng knh ng tron ngoai tiep a giac.

3. Pham vi bao ve cua he nhieu CTS (n>2)


72/114

1

2 3

4

a

b

r0X1

r0X2D

1 2

3

a

b c

rX

r0X12

r0X13 r0X23

rX

1500

4000

A

Xa


73/114

RANH CAP LC 22 KV

RANH CAP IEU KHIEN

PHONG THIET BPHAN PHOI 22 KVPHONG VAN HANH

2T60 MVA

1T60 MVA

2500

2500

300

0

3000

3000

3000

3000

3000

1500

1000

1000

3000

3000

3000

300

0

4000

4500

7000

5000

10000

4000

10000

35000

78,5m

B B

A

GVHD

TRNG I HC BCH KHOA TP . H CH MINHKHOA IN -IN T

B MN H THNG IN

Ngy 12/11/2006 Bn v s : 1

Ngi v ng Nh Tn MT BNG B TRTRM BIN P 110/22 kV

N MN HCCAO P

Xa day

Xa thanhgop

3 00 0 3 00 07000

1500 2500 25003000 30002500 25003 00 0 3 00 02500 25003 000 300 02500 2500 15001500 3000 3000 3000 1500 700015001500

Chu thch :

9,75 m1,77 m 5,04 m9,75 m4,125 m 6,54 m2,52 m


74/114

RANH CAP LC 22 KV

RANH CAP IEU KHIEN

PHONG THIET BPHAN PHOI 22 KV

PHONGVAN HANH

2T60 MVA

78,5m

51,79

m

35,23m

1T60 MVA

55,9

2m

55

,92

m48

,09

m

48,09

m

22 m15 m22m

Vung bao ve cao o 6m

Vung bao ve cao o 8m

Vung bao ve cao o 11m1 2 3 4

67

5

35,23m

51,7

9m

Vung I

VungII

Vung III Vung IV

Vung V

13,875 m

9,75 m

4,125 m

2,4 m

0,6375 m

36,18 m

32,56 mGVHD

TRNG I HC BCH KHOA TP. H CH MINHKHOA IN -IN T

B MN H THNG IN

N 12/11/2006 Bn v s : 3

V Phan T

N MN HCCAO P

PHM VI BO V CA KIM THU ST

TRM BIN P 110/22 kVNgi v ng Nh Tn

MSSV:402HT039

Cot anten

Cot enchieu sang

Cot enchieu sang


75/114

CHU THCH :- CB : MA Y CA T SF6- DS : DAO CA CH LY- ES : DAO NOI AT- BI : MAY BIEN DONG IEN- BU : MAY BIEN IEN AP- LA : CHONG SET VAN

MA T CA T A -A

MA T CAT B-B

BU

BU BIS/ES

LA/ES

14m

11m

8m

4000 1500 3000 3000 3000 3000 3000 40003000 2500 3000 3000 4500

BIS/ES

1500 3000 1000 2500 1000 3000

BU BU BUADS/ES BI

CBDS/ES DS/ES DS/ES

CBLA

LA BUDS/ES DS/ES

LAU

7000

N MN HC CAO P

MT CT TRM BIN P 110/22 kVGVHD

TRNG I HC BCH KHOA TP. H CH MINHKHOA IN -IN T

B MN H THNG IN

Ngy 12/11/2006 Bn v s :

Ngi v ng Nh Tn

N MN HCCAO P


76/114

II. CACH XAC NH PHAM VI BAO VECUA DCS:1. Pham vi bao ve cua mot DCS:

DCS

DDkhongc

bao ve

DD c bao ve


77/114

II. CACH XAC NH PHAM VI BAO VECUA DCS:1. Pham vi bao ve cua mot DCS:

a) Trng hp DCS co o treo cao (h) nho hn 30m :

xx

x

h hb 1,2h

h hp

xx x

xx x

h2h > h: b 0,6h(1 )p

3 hh2

h: b 1,2h(1 )p3 0,8.h

h

Hay


78/114

II. CACH XAC NH PHAM VI BAO VECUA DCS (tt):1. Pham vi bao ve cua mot DCS:

b) Trng hp DCS co o treo cao (h) ln hn 30m :

30m h 100m

h 0,29(h-30)

100m h 250m

h 0,2h

Pham vi bao ve theo chieucao (mat cat ng) giam motkhoang tnh t nh:


79/114

II. CACH XAC NH PHAM VI BAO VECUA DCS (tt):2. Pham vi bao ve cua hai DCS:Khi hai day chong set at cach nhau S = 2B = 4h th moiiem tren mat at nam gia hai day chong set se c baove an toan. Neu S < 4h th gia hai day chong set co thebao ve c o cao:

0

S

h h 4p


80/114

II. CACH XAC NH PHAM VI BAO VECUA DCS (tt):2. Pham vi bao ve cua hai DCS:

Khi day dan 3 pha cua ng day tai ien cung nam trenmot mat phang ngang th ieu kien e day dan gia hai cotc bao ve la khoang cach S gia hai day chong set phaithoa man ieu kien:

4. .( )DCS DDs p h h


81/114

II. CACH XAC NH PHAM VI BAO VECUA DCS (tt):2. Pham vi bao ve cua hai DCS:


82/114

II. CACH XAC NH PHAM VI BAO VECUA DCS (tt):3. Cach xac nh pham vi bao ve cua day

chong set cua ng day tai ien cao ap:

031gh

c

hlg 4

90

III. CC YU CU K THUT KINH TKHI DNG H THNG CTS BO V


83/114

KHI DNG H THNG CTS BO VCHNG ST NH THNH CHO TRM

BIN P V NH MY IN:Ct thu st c th t ngay trn cc kt cu cngtrnh (ct x, ng khi, ct n pha) ca TBAvNM khi tha mt s iu kin nht nh. Vict CTS trn kt cu trm ch cho php khi trmc mc cch in xung ln v in tr ni tb.VD:

-TBA 110kV tr ln d dng tha mn c yucu ny-TBA 35kV ch cho php t CTS trn kt cutrm khi R

n4 Ohms



84/114


BIN P V NH MY IN:Chn kt cu t CTS phi c ni theo ngngn nht vo HTNi t an ton ca trm ti imgiao ca cc thanh cn bng th, ng thi tng

cng thm cc ni t b sung (cc thanh, cctng cng)



85/114


BIN P V NH MY IN:Khi cc iu kin trn khng tha mn th CTS phi tcch ly vi cc kt cu trong trm v ni t ca CTS

phi c tch ring khi ni t an ton ca trm.

Khong cch trong khng kh gia CTS v cc vt cnbo v trong trm phi ln.Tng t, khong cch trong t gia ni t CTS v nit an ton trm cng phi ln.



86/114


BIN P V NH MY IN:

kS 0,3 0,1x AR l dS 0,5 xR

lA

h

VBV

Sk

Sd Rx

Chng 3:


87/114

1

NI T TRONG HTHNG IN


88/114

Trao i trc tuyn ti:


3.1 KHI NIM


89/114

3

Cc ni t: c ng

thng xung mt t su t 0,5m n 0,8m

t

Khng kh

chnsu t0

dy dn dngs c, dng st

Cc ni tbng ng haythp m km

3.1 KHI NIM


90/114

4

Thanh ni t: c chn

trong t su t 0,5mn 0,8m

t

Khng kh

chnsu t0

dy dn dngs c, dng st

Thanh ni tbng ng haythp m km

3.1 KHI NIM


91/114

5

Li ni t: do nhiu cc hay thanh

ghp ni vi nhau, chn trong t su 0,5m n 0,8m

cc thanh nit hay dy cp

kt ni thnh

li

Cc ni tng ven chu vi(hc dc theong cho)

3.1 KHI NIM


92/114

6

Cc mi ghp k thut

3.1 KHI NIM


93/114

7

Ni t lm vic: l ni t im trungtnh ca my pht, my bin p cng sut,

TI, TUm bo s lm vic ca trangthit b in lc bnh thng v s c.

Ni t an ton: l ni t v trang thit

b in hoc kt cu kim loi. m bo anton cho ngi vn hnh khi c s c rcch in.

Ni t chng st: l ni t cc b phnthu st ( KTS, DCS) Nhm tn dng stvo t, trnh phng in ngc t phn t n cc b phn mang in.

C

B

R

A

N

Mun in p ti N = 0

R

R

KTS

3.1 KHI NIM


94/114

8

Cu to ca ni t: thng thng c thc hin bng mt hthng nhng cc bng thp hoc ng ( c th trn hoc dt) ngvo t, hoc nhng thanh ngang chn vo t. Hoc cc v thanh

ni lin vi nhau v chn vo t.

Trm phn phi: 3 h thng ni t phi c ni ring l.

Trm truyn ti ( >=110 kV): 3 h thng ni t c dng chung.

in tr ni t R l t s gia in p trn ccU v dng in qua n I . in trRbao gmin tr ca bn thn in cc v in tr tn trong

t. Khi tn dng mt chiu hay xoay chiu th in tr bn thn incc rt b c th b qua.

R

IU

3.1 KHI NIM


95/114

9

Khi tn dng mt chiu hay xoay chiu th in tr bn thn incc rt b c th b qua.

Hnh : M hnh in cc ni t n gin ( thanh hay cc ni t)

3.1 KHI NIM


96/114

10

Khi tn dng st, qu trnh truyn sng trn cc ni t tng tnh trn ng dy ti in. Do c in cm cn tr dng in i su

vo chiu di in cc nn in th phn b khng u trn in cc.

T< =Ts ( l ln): Ni t ko di ( ni t phn b). Rx R

Rx ()

t (s)

R

nh hng ca in cm s gim dn theo thi gian. in tr tnca cc ni t ln nht gn ng vo lc dng st t gi tr cc

i.

T=L0.g0.l2Ts

3.1 KHI NIM


97/114

11

Hnh : Qu in p ti cc v tr trn cc thanh ni 20 m v 100m

3.1 KHI NIM


98/114

12

Khi tn dng st, ngoi nh hng ca in cmL lm gimkh nng tn dng st ca htn, cn c nh hng phi tuyn bihin tng phng in tia la trong t khi dng st c bin ln. Vng t quanh in cc tr nn dn in tt, lm tng khnng tn dng st, tc lm in tr tn xung gim.

3.1 KHI NIM


99/114

13

Hnh: Bn knh ca cc phn on trn thanh ti cc thi im a) 0.2 s v b) 0.5s

a) b)

3.1 KHI NIM


100/114

14

Hnh: Qu in p ti v tr vo dng st v v tr cui trn thanh t a) FEM v b) FDTD

a) b)

3.1 KHI NIM


101/114

15

i vi ni t chng st cn phn bit in tr tn xung Rx vi

in tr tn n nh R. R cng chnh l in tr tn dng xoaychiu ( R~ ) hay dng mt chiu.

x

x

R

R

Ni t tp trung: x < 1, nh hng ca phng in tia la

chim u thNi t ko di: x 1, nh hng ca in cm dc theo chiudi ca thanh dn trong HTN chim u th

3.1 KHI NIM


102/114

16

Mt s phng php o in tr sut t

2 UaI

Phng php Wenner

2

4ln

l U

l I

d

Phng php Driven Rod

3.2 IN TR TN DNG XOAY CHIU R~


103/114

17

Khi dng in xoay chiu chy qua in cc tn vo t, tonn trong t quanh n mt in trng. Mi im trong in

trng k c trn mt t c mt in th nht nh.

Utx

Ub

Gim Utx , Ub

Trn mt t khu vc ni t

c ri mt lp si hoc gim s chn lch in th.

U

r/U

Gim in p trn in cc Uhay gim in tr tip t.



104/114

18

i vi in cc ni t n gin: cng thc xc nh in trtn tn s cng nghip ca mt s dng in cc thng dng

(Bng 4.1, 4.2)4

ln2

tt

c

lR

l d

Cc chn ni:

0

2 1 4

(ln ln )2 2 4

2

tt

c

l t l

R l d t l

lt t

Cc chn chm:

2

0

ln2

tt

t

lR

l dt

Thanh chn chm:

0

8(ln ln )

2 . 4

tt

V

D DR

D d t

Thanh hnh xuyn chn chm:

2

0

ln

2

tt

t

kLR

L dt

Thanh c hnh dng c bit:

d

dang trn

b

b

dang gc

d=0,95b

dang dpd=0,5b

dott mk in tr sut tnh ton ca t:



105/114

19

i vi in tr ni t ca t hp nhiu in cc:

Hiu ng mn che lm mo dng vng

ng th gia hai in cc, lm gim khnng tn ca h thng ni t.

c trng cho hiu ng mn che,ngi ta dng h s ~. ~ l h s s dng

khi tn dng in xoay chiu tn s cngnghip. y l i lng ton hc th hin

bn cht vt l l hiu ng mn che.

R1 R2 R3

B qua hiu ng mn che Rt= R1//R2//R3

Xt n hiu ng mn che Rth~=Rt/~ > Rt ~~

1td

th

R

R

3.2 IN TR TN DNG XOAY CHIU R~ d h h l i i l h


106/114

20

H s s dng ph thuc vo vo loi in cc, s lng v cchb tr chng. N c th tra cu trong cc bng s hoc cc ng

cong cho trong cc ti liu hng dn(SBT PL 4 n PL 7).Xt t hp thanh v cc

cc n

Rc, Rt: in tr ca tng cc ring l v thanh.

c,t h s s dng ca cc v thanh trong t hp

12 m

3 m c = 0.7 , t = 0.74VD

c t

c t c t

th

c t c t t c

c t

R R

n R RR

R R R R nn

3.3 IN TR TN NI T CHNG ST3 3 1 i d i


107/114

21

3.3.1 in tr tn xung ca dng ni t tp trung Kch thc tht ca in cc c th

thay th bng kch thc ca khu vcphng in tia la.

Rx = xR~ (x < 1 )

x= f(Is,): c trng cho phng

in trong t v gin n in cc nit.

Khi chiu di ca in cc tng lnth x tng ln do nh hng ca incm.

Phng in trong t

E > Ep()

IS

Bin ln

E = Ep()

Nu ni t l t hpRthx = Rtx/x >Rtx

x: th hin hiu ng mn che ca t hpkhi tn dng in xung.

3.3 IN TR TN NI T CHNG STT h h i h i


108/114

22

Trnh t tnh ton in tr tn xung ca mt t hp ni t tp trung

B1: Chn km (ni t chng st) . tt = km.o

B2: Tnh R~ ca tng loi in cc ring l. (R~c,R~t)

B3: TnhRx ca tng loi in cc rring l (Rxc,Rxt)

- Tnh dng st phn b qua mi in cc ring l- Tnh x : c th tra bng hoc tnh bng cng thc

Rxc = xcR~c ; Rxt= xtR~t

B4: in tr tn xung ca c t hp

1 1xc

xtxc xt

th

xc x xc xt xxt

RR

R RnRR R n R

R

n

n : s cc

x : h s s dng xungca t hp. (

x


109/114

23

BT 1: Chng ta c mt thanh st trn di40 m ng knh 20 mm. Hi dng

ni t no sau y, c in tr tnxoay chiu nh nht? Bit ni tc chn su 0.8 m trong t. tc in tr sut o vo ma ma l100 m.

a) b)

c)

l1

l2 = 2l1

BT 2: Cho mt h t hp phc nh hnh gm5 cc, mi cc di 3 m, ng knh 30mm, ng cc dc theo thanh dng trnng knh 20 mm di 12 m. C t hpnm su trong t 0.8 m c in tr suto lc kh ro l 120 m. B qua hiung mn che. Tnh in tr tn xoaychiu ca t hp.

3.3 IN TR TN NI T CHNG STBT 3: Cho mt h t hp phc nh hnh gm 3


110/114

24

BT 3:

BT 4:

Cho mt h t hp phc nh hnh gm 3cc, mi cc di 3 m, ng knh 25 mm,

ng cc dc theo thanh dng trn ngknh 15 mm di 12 m. C t hp nm sutrong t 0.5 m c in tr sut o lc khro l 150 m. Tnh in tr tn xoay chiuv tn xung ca t hp.

Xc nh in trxoay chiu v xung kch ca ba thanh nit lmbng thp dt 4x40 mm2, mi thanh di 15 m chnsu trong t 0.8 m. in tr sut t o vo ma m l 200

m. Gi s dng st chy qua h thng ni t l 120 kA.

Is = 100kA

1500

320 45

t

tt t

l

I

Is

It


111/114

3.3 IN TR TN NI T CHNG ST3 3 2 i t t i t k di b th h


112/114

26

3.3.2 in tr tn xung ca ni t ko di bng thanh ngang

a. Khi b qua qu trnh phng in trong t ( ln, is nh)

in p ti v tr bt k theo thi gian t:

1 210

1 210

1( , ) 2 1 os

1(0, ) 2 1

k

k

t

T

k

t

T

k

a k xu x t t T e c

g l k l

au t t T eg l k

Tng tr tn xung u vo ti mt thi im bt k t:

12

10

2(0, ) 1 1(0, ) 1 1(0, )

k

t

T

ks

Tu tZ t e

i t g l t k

2

0 0 11 2 2

;k

L g l TT T

k Hng s thi gian ca qu trnh truyn

sng iu ha bc 1 v bc k

3.3 IN TR TN NI T CHNG ST3 3 2 i t t i t k di b th h


113/114

27


a. Khi b qua qu trnh phng in trong t ( ln, is nh)

Mt cch gn ng khi dng st t tr s cc i (t = Ts)th tng tr xung du vo c tr s ln nht.

s

1s 2

10 s

21 1(0, ) 1 1

d

k

T

T

d

kd

TZ T e

g l T k

Trng hp Ts/T1 > 3

2

1 1s 2

10 s s

0s

21 1(0, ) 1 1

3

(0, )3

d

kd d

d

ds

T TZ T R

g l T k T

L lZ T R

T

3.3 IN TR TN NI T CHNG ST3 3 2 in tr tn ng ca ni t ko di bng thanh ngang


114/114


b. Khi xt n qu trnh phng in trong t

Phng in dc theo chiu di thanh lm cho khuvc phng in thu hp dn, dn n in dn tn xungkhng cn l hng s. H phng trnh truyn sng tr

nn khng tuyn tnh v c gii bng phng phpgn ng hoc phng php s.

ng vi mt tr s v Is nht nh c mt tr sgii hn ca chiu di in cc m vt qu gii hn

, tng tr xung khng gim khi tng chiu di incc na

ki thuat cao ap qua dien ap trong he thong dien

Documents