Phan Dien Trong Nha May Dien Va Tram Bien AP

7/25/2019 Phan Dien Trong Nha May Dien Va Tram Bien AP

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Mn hoc: Phn in trong nhamay in vatram bin ap

Nhom Nhamay in - Bmn Hthng in - HBK aNng 1

Chng 1KHAI NIM CHUNG VNHAMAY IN

TRAM BIN AP & HTHNG NNG LNG

1.1 KHAI NIM PHN LOAI NHAMAY IN VATRAM BIN AP1.1.1- Phn loai nhamay in ( NM )

Nhamay in lamt X nghip c bit conhim vubin i cac dangnng lng khac nhau nh nng lng cua nhin liu (than, du, kh t, nguyntv.v. . . ) nng lng cua dong nc, gio, mt tri v.v ... thanh in nng cung cp cho cac htiu thu.

Cn cvao cac loai nhin liu sdung cho nhamay in ngi ta chia ra:Nhamay nhit in , thuy in , phong in , nhamay in nguyn t, nhamayin dung nng lng mt tri v.v...

a- Nhamay nhit in (N)Trong nhamay nhit in ngi ta dung nhin liu lathan a, du hoc

kh t , trong othan ac sdung rng rai nht.quay may phat in, trong nhamay nhit in dung tuabin hi nc ,

may hi nc ( l c m bin ), ng c t trong vatua bin kh, tuabin hi nccokhanng cho cng sut cao vavn hanh kinh tnn c sdung rng rainht.

Nhamay nhit in con c chia lam 2 loai: Nhit in ngng hi vanhit in trch hi:

+ Nhamay nhit in ngng hi toan bhi dung san xut in nng.+ Nha may nhit in trch hi mt phn nng lng cua hi c s

dung vao muc ch cng nghip vasinh hoat cua nhn dn vung ln cn.b. Nhamay thuy in : ( T )Nhamay thuy in dung nng lng cua dong nc san xut ra in

nng . ng c s cp quay may phat thuy in la cac tua bin nc truc

ngang hay truc ng .So vi nhit in nhamay thuy in comt su im quan trong sau :* Giathanh in nng thp ch bng 1/5 - 1/10 nhit in .*Khi ng nhanh ch cn mt phut la co th khi ng xong va cho

mang cng sut , trong khi okhi ng mt tmay nhit in ( kcalovatuabin ) phai mt hang ngay .

* Cokhanng tng hoa cao nn sngi phuc vutnh cho mt n vcng sut ch bng 1/10 1/15 cua nhit in .

* Kt hp cac vn khac nh cng trnh thuy li, chng lulut, han han,giao thng vn tai, hthacav.v...

Tuy nhin nhamay T cung comt snhc im ang chuy:


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* Vn u t xy dng mt nhamay rt ln.* Thi gian xy dng dai.* Cng sut b han chbi lu lng vachiu cao ct nc .* Thng xa h tiu thunn phai xy dng ng dy cao ap rt tn

kem.c - Nhamay in nguyn t:Thc cht nhamay in nguyn tlamt nhamay nhit in, trong olo

t than c thay bng lophan ng nguyn t.Nhamay in nguyn ttiu thunguyn liu ( Torium vaUranium ) rt

t, v nng lng 1kg Uranium tng ng vi nng lng cua 2700 tn than atiu chun. V vy nhng vung nui khng thun tin cho vic vn chuynnguyn liu th vic xy dng nhamay in nguyn tcoyngha quan trong.

Nm 1954, Lin X xy dng nhamay in nguyn tu tin cocngsut 5.000KW, tiu thu ngay m khoang 30g Uranium, trong khi o N cocung cng sut tiu thukhoang (100 110) tn than xu.

d- Nhamay in dung sc gio:Trong nhamay in nay, ngi ta li dung sc gioquay mt hthng

canh quat vatruyn ng quay may phat in. Khokhn cua nhamay innay lado tc vahng giolun lun thay i, nn iu chnh tn svainap gp nhiu khokhn.

e- Nhamay in dung nng lng mt tri :Thc cht cung la nha may nhit in, trong o lo than c thay thbng hthng knh thu nhn nhit nng cua mt tri. Nhamay in dung nnglng cua mt tri u tin trn thgii ac xy dng Lin X vi cngsut 1.200 KW. Ngoai ra con conhamay in dung sc nc thuy triu lamtnhamay thuy in sdung nng lng thuy triu.

1.1.2/ Phn loai tram bin apa- Tram tng ap :

Tram tng ap thng t cac nhamay in conhim vutng in ap

tin ap may phat n in ap cao hn truyn tai n cac htiu thuxa.b- Tram haap :

Tram haap t cac htiu thu, bin i in ap tai lngcao hn n ai lng thp hn thch hp cho cac htiu thuin.

c.Tram bin i in xoay chiu thanh mt chiu vangc lai.d- Tram phn phi in:

Gm mt sng dy cung cp vamt sng dy phn phi n cachtiu thu. Cac ng dy nay cocung in ap nh nhau, nn trong tram phn

phi khng cn may bin ap, y ch t thanh gop, kh cuin ong ct, iukhin.


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1.2. HTHNG NNG LNGHthng nng lng latp hp nhng nhamay in, tram bin ap, cac h

tiu thuin vanhit nng, chung c ni lai vi nhau bng cac mang in vanhit.

Hthng in lamt bphn cua hthng nng lng gm cocac mayphat in, thit b phn phi in, mang in vacac hi tiu thuin.

Ngi ta chia hthng nng lng thanh 3 bphn chnh:1- Ngun phat nng lng: Nhamay in san xut nhit nng vain

nng.2- Bphn truyn tai: Mang in vamang nhit.

3- Cac h tiu thu: Bin i in nng va nhit nng thanh cac dangnng lng khac.

c im cua hthng nng lng:a- San xut vatiu thuphai ng thi , cac sccua bt cbphn nao

lam mt scn bng gia san xut vatiu thuu cothdn n ngng lam vicmt phn hay toan bhthng .

b- Cac quatrnh quatrong hthng nng lng xay ra rt nhanh, nnngi ta phai sdung cac thit b rle tng loai trscnhanh chong.

c- Sphat trin cua hthng nng lng phuthuc vao sphat trin cuann kinh tquc dn vaphai c phat trin trc mt bc.u im cua hthng nng lng:a- am bao phn phi cng sut hp lyvakinh t nht , tn dung cac

thit b va nguyn liu a phng mt cac hp ly, do ogiam gia thanh innng.

b- Nng cao tnh cht am bao cung cp in lin tuc cho cac htiu thu.c- Giam c phn trm cng sut dtrva tng c cng sut n v

cac tmay.Nhc im cua hthng nng lng:Xy dng hthng nng lng oi hoi phai tn thm vn u t xy dng

cac tram bin ap vang dy lin lac. Tuy nhin nosec bulai nhanh chongbng vic hagiathanh in nng vatng tin cy cung cp in vanhit.1.3. TH PHUTAI :

1.3.1/ nh ngha vaphn loai :c im cua san xut in nng la san xut va tiu thu phai thc

hin ng thi. Tai mi thi im, htiu thu(kcatn tht) tiu thubao nhiu

in nng th nhamay in phai san xut ra ngn y in nng. Trong thc t,tiu thuin nng qua mt ngay m thay i rt nhiu. vn hanh kinh tva


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am bao, cn phai bit c quy lut bin thin cua phu tai, chun b chaythm cac tmay khi phutai giam. Qui lut bin thin cua phutai c bin dintrn hnh ve, goi lath phutai. Trn truc tung cua th, biu din cng suttac dung, phan khang hay cng sut toan phn bng n v co tn hay n v

tng i vi lng c ban lacng sut cc ai, trn truc hoanh cua th biudin thi gian bng gihay ngay.

Cothphn loai th phutai theo nhiu cach:+Theo cng sut : th phutai tac dung, phan khang, toan phn.+ Theo thi gian : Hang ngay, hang nm, mua.+ Theo v tr trong hthng : th phutai cua hthng, cua nhamay

in, cua tram bin ap, cua htiu thuv.v...1.3.2/ Cach veth phutai :

a- th phutai hang ngay : ve th phu tai hang ngay co th dung watt met t ghi la

chnh xac nht.Cung co th ve theo phng

phap tng im, ngha la c sau mtkhoang thi gian nht nh ghi lai trsphutai ri biu din tng im trnh truc tooa . Ni cac im lai se

ng gay khuc biu din phu tai mtcach gn ung. ( H.1.1) .Hnh 1.1

Phng phap venay tuy khng chnh xac, nhng trong thuc tlai dung rtphbin. cho vic tnh tn tht in nng c thun tin, thc tngi tabin ng gay khuc thanh ng bc thang . Khi bin i phai am bao haiiu kin :

1- Din tch gii han bi ng mi va ng cu vi truc toa phaibng nhau.

2- Cac im cc ai vacc tiu cua ng cuphai nm trn ng mi.veth phutai cua Nhamay in, ngi ta dung phng phap cng

th. th phutai hang ngay cua nhamay in bng tng cac th phutaicua cac htiu thu, cng vi tn tht qua may bin ap vatdung.

Tn tht trong may bin ap gm hai phn :1- Tn tht trong thep, khng phuthuc vao sbin thin phutai vabng

1-3% phutai cc ai.2- Tn tht ng, phuthuc vao sbin thin phutai vabng 6-15% phu

tai qua may bin ap.Phutai tdung cua nhamay cung gm 2 phn :


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1.3.3/ Cac ai lng c trng cua th phutai:a) Cng sut trung bnh : Goi A lain nng san xut ra trong thi gian

T, th cng sut trung bnh Ptbtrong thi gian T xac nh nh sau:

T

APtb=

b) Hsin kn phutai latys:

maxmaxmax .

.

A

A

TP

TP

P

PK

tbtb

dk ====

y : Pmaxlacng sut cc ai trong thi gian T. biu th mc khng ng u cua th phutai

Khi : Ptb= Pmax th = 1

Thc t

< 1,

cang ln cang tt.

c) Hssdung cng sut t lat s:

d

tb

sd

P

PnK ==

y: PTng cng sut t cua tt cacac tmay kcadphong, n noiln mc sdung cng sut t, n cang ln chng totn dung cng sut tcang nhiu vanh thlatt.

Do Pmax < P n <

d) Thi gian sdung cng sut cc ai bng

TP

TP

P

AT

tb ..

maxmax

max ===

Nh vy, nu luc nao phutai cung laPmax, th ch sau thi gian Tmax, phutai atiu thuin nng ung bng in nng tiu thuthc tvi cng sut thayi. ng vquan im kinh tTmaxcang ln cang tt.

) Thi gian sdung cng sut t xac nh nh sau:Tn

P

TP

P

AT

d

tb

d

d .

.===

Cung nh Tmax, Tcang ln cang tt.

1.3.4/ Phn phi phutai hang ngay cho cac NM trong hthng:Khi cac nhamay ac ni lai thanh hthng th vic phn phi th

phutai cho cac nhamay coanh hng rt ln n giathanh in nng. vnhanh kinh t, chung ta se phn phi th phu tai cho cac nha may trong hthng theo cac nguyn tc sau y:


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a) Trc ht u tin phn phi phutai chocac nha may co th phu tai bt buc toanphn hay bt buc tng phn am nhn phnphutai gc.

Nha may co th phu tai bt buc toanphn lanhng nhamay thuy in khng cohcha valam vic trong mua ma lu.

Nhamay coth phutai bt buc tng phnlanhng nhamay nhit in trch hi . i vinhng nha may nay cho hiu sut cao ngvi mt phu tai nhit nht nh oi hoi phai cophutai in nht nh.

Hnh 1.4

Giathit vi phutai nhit acho cohiu sut cao nht, th phn th phutai in cua nonh phn NR trn hnh 1.4 .

b) Phn con lai cua th phu tai, se giao cho cac nhamay nhit inngng hi, nhng trc ht u tin cho nhng nha may ngng hi gn ngunnhin liu vacoc tnh sut hao hi kinh tnht.

c) Phn mui nhon cua th phutai segiao cho cac nhamay thuy in cohcha nc, v nomvangng may nhanh chong, t tn kem. Trong hthngin khng conhamay thuy in th phn mui nhon segiao cho cac nhamay

nhit in ngng hi cu kem kinh t.1.3.5/ iu chnh th phutai :nng cao tnh kinh tcua nhamay in phai tin hanh iu chnh

th phutai nhm tng thi gian sdung cng sut t T, cung nh thi gian sdung cng sut cc ai Tmaxlam cho th phutai bng phng hn sao cho innng cua nhamay phat ra ln nht. Ngi ta dung cac bin phap iu chnh th phutai chuyu sau y:

a) Phat trin cac hdung in theo mua, mi mua conhim vukhac nhaunhm tiu thuin nng canm.

b) Nhng hch dung in vai gitrong mt ngay ch cho phep lam victrong nhng githp im.

c) Tng sca lam vic trong x nghip.d) Btr ngay ngh trong mt tun cua cac x nghip lch nhau.) iu chnh gibt u lam vic cua cac tkhac nhau.


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Mn hoc: Phn in trong nha may in va tram bin ap

Nhom Nha may in - B mn H thng i n - HBK a Nng 9

Trong tnh trang lam vic bnh thng, in ap cua 3 pha i vi tUa, Ub, Uci xng bng in ap pha cua thit b. Do o dong in dungcua cac pha IC0A, IC0B, IC0C cung i xng vi nhau va tng cua chung bngkhng, cho nn khng co dong nao chay trong t.

CUIII

III

fCCBCAC

CCBCAC

..

0

000

0

*

0

*

0

*

===

=++

Dong in trong cac pha cua may phat in IFA, IFB,IFCbng:

CCptCFC

BCptBFB

ACptAFA

III

III

III

0

***

0

***

0

***

+=

+=

+=

T th Vect thy rng dong in dung co anh hng lam giam goclch pha cua dong in trong cac may phat, tc la no co kha nng lam tngh s cng sut .

2.1.2/ Khi co mt pha cham t:Gia thit rng pha C cua mang in cham t trc tip, khi o in ap

i vi t cua pha C bng khng. in ap cua pha C bng khng co th coinh tai ch cham t, c t thm vao mt in ap th t khng bng -Uc.

Nh vy, i n a p mi cu a ca c pha i vi t U'A , U'B , U'Cbng tng hnhhoc in ap cac pha i vi t trc khi cham t va in ap th t khng.

Hnh 2.2 a/

b/


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0**,*

**,*

**,*

==

=

=

CCC

CBB

CAA

UUU

UUU

UUU

T th vect hnh b d dang tnh c:

0

3

3

,*

*,*

*,*

=

=

=

C

BB

AA

U

UU

UU

Tc la in ap cua pha b cham t bng khng, con 2 pha kia tng

ln 3 ln ( bng in ap dy ). Do o, dong in dung qua in dung cuapha b cham t bng khng, con dong in dung qua in dung cua hai phakia tng ln 3 ln so vi dong in dung luc bnh thng.

003;3;0 CCBCCACC IIIII ===

Chung ta quy c chiu dong in tnh t dy dn vao t, t hnh vetnh c dong in chay trong t (cung la dong in chay trong pha bcham t nh sau).

CCCACBCAC IIIIII ===+= 0

***

33

Tc la dong in dung trong pha b cham t tng ln gp 3 ln dongin dung bnh thng. ai lng tuyt i cua ICco th xac nh nh sau:

CUX

UII f

C

f

CC 33

30

===

Trong o Ufla in ap thit b .T o ta thy rng dong in in dung phu thuc vao in ap , tn

s va in dung cua pha i vi t . in dung cua pha i vi t lai phuthuc vao cu tao va chiu dai ng dy. Vi tn s cng nghip , dongin dung Ic co th xac nh theo cng thc kinh nghim sau y :

i vi ng dy trn khng : [ ]ALUI d

C350. =

i vi ng dy cap: [ ]ALUI dC10

.

=

y: Ud : in ap dy cua thit b [ KV].L : Chiu dai tng cng cac ng dy co

ni in vi nhau [Km ] .T th vect ( H.2.2b) ta thy rng :


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CAACCA

BCCBBC

ABBAAB

UUUU

UUUU

UUUU

*,*,*,*

*,*,*,*

*,*,*,*

==

==

==

Nh vy i n ap dy trc va sau khi cham t mt pha khng thay i.Tom lai khi cham t trc tip 1 pha, th tnh hnh mang in co

nhng thay i sau:a) in ap cua pha cham t bng khng, con hai pha kia tng ln

bng in ap dy.b) Dong in in dung trong pha cham t tng ln 3 ln, con hai pha

kia tng3 ln.c) in ap dy cua thit b trc va sau khi cham t khng thay i.d) in ap cua im trung tnh tng t khng n in ap pha.Do dong in dung sau khi cham t rt nho so vi dong phu tai va

in ap dy khng thay i, nn cac phu tai vn lam vic bnh thng. Tuyvy, i vi mang in nay ngi ta cung khng cho phep lam vic lu daivi mt im cham t, v nhng nguyn nhn sau y:

a) Sau khi cham t, in ap cua cac pha con lai tng ln 3 ln sovi in ap pha, do o nhng ch cach in yu se b choc thung va gy rangn mach gia cac pha. khc phuc phai thit k cach in chu cin ap dy dn ti tng gia thanh thit b.

b) Dong in dung se sinh h quang, co th t chay cach in tai chcham t va dn n ngn mach gia cac pha. Vi mt tr s nht nh cuadong in dung, h quang se chay chp chn ngha la chay i tc lai mtcach chu ky. V mang in la mt mach vong dao ng nn hin tng nayse dn n qua in ap, lam cho in ap cac pha tng ln n (2,5 - 3)lnin ap pha nh mc. Do o cach in cua cac pha khng b cham t ddang b choc thung va dn n ngn mach gia cac pha, mc du no a cthit k bng cach in in ap dy .

Quy trnh ky thut vn hanh quy nh mang in co th lam vic vitrung tnh cach in i vi t - nu do ng in cham t mt pha la:

- Khng ln hn 20 30A i vi mang 6 10KV

- Khng ln hn 15A i vi mang 15 20KV- Khng ln hn 10A i vi mang 35KVVi mang ln hn 110KV noi chung khng lam vic vi trung tnh

cach in vi t v trong cac mang ny d tr cach in rt be.Trong mang trung tnh cach in vi t nht thit phai co thit b

bao tn hiu cham t 1 pha nhn vin vn hanh bit, tm cach sa chahay thm ch ct lun phn t h hong.


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Cui cung, cn noi thm rng nu cham t 1 pha qua 1 tng tr trunggian nao o, th in ap pha b cham t ln hn 0 nhng nho hn U f , conin ap 2 pha kia ln hn Ufnhng nho hn Ud va in ap trung tnh ln hn0 nhng nho hn Uf.2.2 /Mang in ba pha trung tnh ni t qua cun dp h quang :

Nh a noi trn, cac mang in 35KV tr lai, khi cham t 1 pha chcho lam vic vi dong in in dung nht nh. V vy, trong nhng mangin nay khi dong in dung ln hn, trung tnh cua mang in phai cni qua cun dp h quang, giam dong in in dung tai ch cham t.Cun dy dp tt h quang la mt cun dy in cam co loi thep t trong 1thung cha y du may bin ap. Trng b ngoai rt ging may bin ap inlc 1 pha. in khang cua cun dy dp tt h quang rt ln, con in trcua no khng ang k. in khang co th thay i c bng cach thay is vong dy hoc khe h cua loi thep

Hnh 2 - 3Trong iu kin lam vic bnh thng, in ap t ln cun dp h

quang coi nh bng 0, v in ap cua im trung tnh gn bng 0, do o trongcun dy dp tt h quang khng co dong in.Khi 1 pha cham t trc tip,in ap im trung tnh tng ln bng in ap pha, do o cun dy dp tt h

quang t di in ap pha va trong no se co dong in in cam I L chmpha so vi in ap im trung tnh 1 goc 90o. Kt qua la tai ch cham t, seco dong in IL va Ic ngc pha nhau. Nu iu chnh ILthch hp th dongin tai ch cham t bng 0, h quang khng th xut hin.

Trong thc t vn hanh, phai ong ct cac ng dy nn dong Ic thayi do o khng th thc hin c IL = Ic . Mt khac, ngi ta mun rngdong in tai ch cham t sau khi bu con co 1 tr s nao o, cho bao vr le tac ng cho tn hiu bao cho nhn vin trc nht bit kp thi sa


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cha nn ngi ta thng iu chnh IL > Ic tc la I = IL - Ic > 0 . Mangin c iu chnh nh vy goi la mang qua bu.

Cn chu y rng trong mang in trung tnh ni t qua cun dy dptt h quang, cach in pha cung phai c thit k bng cach in dy.Mang in 3 pha trung tnh cach in hay ni t qua cun dp h quang,

goi la mang co dong in cham t be va cn phai co thit b kim tra tnhtrang cach in.

2.3/ Mang in ba pha trung tnh trc tip ni t :

a/ Ni t trc tip b/ Ni t qua in khang nho .Hnh 2.4

Cac mang 110KV va cao hn, u co trung tnh trc tip ni t vnguyn nhn sau y.- Dong in dung cua cac mang nay rt ln do in ap cao va chiu

dai ng dy ln.- Du co dung cun dp h quang cung khng giai quyt c nhc

im cua mang in co dong cham t be la khi cham t 1 pha in ap cacpha con lai tng ln bng in ap dy, trong khi o d tr cach in cua cacmang in ap ln hn 110KV rt be, nn cach in d dang b choc thungdn n ngn mach gia cac pha, tng cng d tr cach in trong cacmang nay rt tn kem.

u im c ban cua mang in trung tnh trc tip ni t la lam chogia thanh kh cu in va cach in ng dy re hn v ch cn ch tao viin ap pha. Tuy vy mang in trung tnh ni t cung co nhc im sau :

- Trung tnh trc tip ni t th khi cham t 1 pha la ngn mach thitb bao v se ct mach in lam cho vic cung cp in b ngng tr. Tuynhin, thc t vn hanh chng to rng phn ln trng hp cham t 1 phacua ng dy trn khng in ap ln hn 1000V ch la tam thi. Nn


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mang nay thng dung thit b t ng ong lai giam thi gian mt incua cac h tiu thu n mc thp nht.

- Do dong in cham t 1 pha rt ln nn thit b ni t phc tap vat tin.

- Dong in ngn mach 1 pha co th ln hn dong in ngn mach 3

pha. han ch dong in ngn mach 1 pha phai tng in khang th tkhng bng cach giam bt s im ni t trung tnh trong h thng inhoc ni t trung tnh qua mt in khang nho.

Li in trung tnh trc tip ni t hay ni t qua in khang nho(co in ap ln hn 1000V ) u goi la li in co dong in cham t ln(> 500A ).

Cn chu y thm rng i vi cac mang in be hn 500V u lam vicvi trung tnh trc tip ni t khng phai v nguyn nhn tit kim cachin ma am bao an toan cho ngi. Ngoai ra mang in nay ngi ta

con dung dy trung tnh ly in ap pha.


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Chng 3

S NI IN CUA NHAMAY IN VATRAM BIN AP3. 1. Cac yu cu c ban cua s ni in trong Nhamay in vatram bin ap.

1. Khai nim chung:S ni in latp hp tt canhng thit b in chnh nh may phat, may bin

ap, ng dy, may ct, thanh gop, thit b thao tac, v.v . . . c ni vi nhau theo mtthtnht nh.

S ni in rt a dang nhng khi thit kcn thoa man cac yu cu c ban sau:

a. Vai tro, v tr cua nhamay in hay tram bin ap:Cac nhamay in vatram bin ap trong h thng in covai tro, v tr khac nhau

hoan toan, v dumt snhamay selam vic nh phutai, mt snhamay lam vic

phuthuc th phutai nhit,.... nn s ni in cua cac nhamay nay sekhac nhau.i vi tram bin ap cung vy: Cotram ch comt phutai, cotram cung cp cho mt shtiu thuring le, hay mt cum phutai cua mt vung rng ln vacung cokhi dung lin lac vi hthng cho nn s ni in cung khac nhau.

b. tin cy cung cp in:Yu cu am bao cung cp in tuy thucmc quan trong cua htiu thuquyt

nh.- Hloai I:Latt canhng hmakhi ngng cung cp in segy nguy him cho

tnh mang con ngi, anh hng ln n an ninh, trt t, chnh tr lam hong thit b - sanphm hang loat gy thit hai ln cho nn kinh tquc dn.

V vy i vi cac hnay yu cu cung cp in lin tuc ngay cakhi sc, thigian mt in ti a cho phep bng thi gian tng ong ngun dphong khoang (0,50,7) giy cho nn hloai I phai c cung cp in bng hai ng dy thai ngunc lp.

- Hloai II: Lanhng htiu thumakhi ngng cung cp in ch lam ngng tr

san xut, lam can trgiao thng vn tai, anh hng sinh hoat khu dn c ln, thanh ph.Thi gian cho phep mt in dai hn hloai I cac nhn vin vn hanh thc hin

thao tac (sa cha hay) ong ngun dphong bng tay. Hloai nay cothcung cp inbng 1 ng dy nhng phai congun dphong.

- Hloai III : Latt canhng hcon lai, y lanhng hkem quan trong vi vythi gian mt in cho phep dai hn nhng khng quamt ngay m.

Cac s ni in phai am bao tnh tin cy khi h hong bt cbphn nao trn s

th nhng bphn con lai vn am bao cung cp in theo mc yu cu.- Yu cu n gian, linh hoat, thun tin thao tac, an toan phuc vu:


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S ni in cang n gian, cang rorang th tnh am bao lam vic cang tt vacang an toan cho ngi phuc vu. S linh hoat phai cho phep vn hanh nhiu tnhtrang khac nhau, do os phai conhiu thit b, nhng khi oxac xut scsetngln ngha latnh n gian vatnh linh hoat thng mu thun nhau. V vy cn xet chnh

xac tng trng hp cuth. Tnh an toan quyt nh chuyu bi cach btr cac thit btrong s .- Tnh kinh tcua s :Quyt nh chuyu bi stn tai cua cac thit b vahnh thc thanh gop. Yu cu

chi ph vn hanh hang nm benht : Zmin .

2. Phn loai s ni in chnh :a.Theo spha:

- S 1 si (tc 1 pha)

- S 2 si- S 3 si (ba pha)

S 3 si rm ranhng biu din c cho ca3 pha, con s 1 si th ngian dung 1 si ai din cho ca3 pha vanoc sdung rng rai nht. Tai nhng nii xng ta dung s 1 si, nhng nhng chbt i xng ta phai dung s 3 si.

b. Theo phng phap sdung may ct, dao cach ly:

Ngi ta chia thanh 2 nhom :- Mi mach c bao vbng 1 may ct. (S mt hthng thanh gop)- Mi mach c bao vbng 2 may ct (S tam giac). Slng may ct bng

(12) ln smach.Cahai loai s thuc nhom thI hoc thII cothcohoc khng cohthng

thanh gop.

~MF

MBA

~MF

MBA

Dung cuo


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3. 2.S cu truc

1.Nhamay comt cp in ap cao:

2. Nhamay cohai cp in ap cao:

S xy dng TBPP UF S bMF-MBA

F1

TBPP UC

TBPP UH

HT

Std+ SUF

TBPP UT

F2 F3 F4

Std

TBPP UC

F1

HT

Std + SUF

TBPP UT

F2 F3

Std + SUF Std+ SUF

B1 B2

B3 B3

B2B1

F2F1

TBPP UC

TBPP UH

HT

Std+ SUF

TBPP UC

HT

F2

F1Std + SUF Std+ SUF

S xy dng TBPP UF S bMF-MBA

B1 B2B1 B2


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3.3. S Hthng mt thanh gop

1. S Hthng mt thanh gop khng phn oan :

a. M ta s : Trong s nay cac ngun cung cp vacac ng dy u nivao thanh gop qua mt may ct vahai dao cach ly.

(Trn mi mach u cn phai t mt may ct in ct mach in chlamvic bnh thng cung nh sc.)

- Dao cach ly CL11, CL21, CL31, CL41, CL51gia may ct vathanh gop goi ladao

cach ly thanh gop.- Dao cach ly CL12, CL22, CL32, CL42, CL52vpha ng dy goi ladao cach ly

ng dy.(Cac dao cach ly nay c dung tao khoang cach an toan trng thy khi sa

cha cac phn ttrong mach) .Ngun N1(N2) cothlamay phat in, may bin ap hoc ng dy tai in. Nu

ngun cung cp lamay phat in (hoc may bin ap) th khng cn t dao cach ly giamay phat (may bin ap) vamay ct v khi sa cha may ct th may phat sengh. Bnhthng tt cacac may ct vadao cach ly u v tr ong, hai ngun N1 vaN2 cung cpin cho cac phutai.

b. Thao tac s : Sa cha may ct: V dusa cha MC1

- Ct may ct MC1.- Ct cac dao cach ly CL12, CL11.- Thc hin cac bin phap an toan a may ct MC1ra sa cha (Ni t an

toan, t bin bao, rao chn, ...).

MC1

N1 N2

CL12

CL11

MC2 MC3

D1 D2 D3

CL22

CL21

CL32

CL31

MC4

CL41

CL42

CL51

CL52

MC5

Hnh 3-1


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Khi sa cha xong MC1ta tin hanh ong in lai cho ng dy D1nh sau:- Mni t an toan.- ong cac dao cach ly CL11, CL12.- ong may ct MC1.

Nh vy ng dy D1b mt in trong sut quatrnh sa cha MC1. Khi cn sa cha, kim tra ng dy: V dusa cha ng dy D2

- Ct may ct MC2(Thao tac bng tay)- Ct dao cach ly CL22.- Thc hin cac bin phap an toan tin hanh sa cha ng dy D2.

Sau khi sa cha xong ong in lai cho ng dy D2theo trnh tngc lai.

Khi congn mach xay ra trn ng dy: V dungn mach trn ng dy D2- Bao vrle sea tn hiu n ct may ct MC2.

- Ct dao cach ly CL22.- Thc hin cac bin phap an toan tin hanh sa cha ng dy D2.

Thao tac sa cha thanh gop:

- Ct tt cacac may ct mach ng dy ni vao thanh gop theo thtngdy kem quan trong ct trc: MC1, MC2, MC3.- Ct tt ca cac may ct ngun ni vao thanh gop: MC4, MC5.- Ct tt ca cac dao cach ly thanh gop: CL11, CL21, CL31, CL41, CL51.

- Thc hin cac bin phap an toan sa cha thanh gop: Ni t an toan ...Khi sa cha thanh gop th toan bs b mt in.

Khi congn mach trn thanh gop:- Bao vrle a tn hiu i ct cac may ct ngun (MC4, MC5) vamay ct cua

nhng ng dy congun cung cp thai pha hoc congun dtr(MC2, MC3).

Toan bs b mt in.- Ct tt cacac may ct mabao vrle cha a tn hiu ct (MC1).- Ct tt cacac dao cach ly thanh gop: CL11, CL21, CL31, CL41, CL51.- Thc hin cac bin phap an toan sa cha thanh gop: Ni t an toan ...

Sau khi sa cha TG xong ta khi phuc lai slam vic cua s nh sau:

- Mni t an toan.-ong tt cacac dao cach ly thanh gop: CL11, CL21, CL31, CL41, CL51.- ong tt cacac may ct ngun ni vao thanh gop: MC4, MC5.- ong cac may ct mach ng dy ni vao thanh gop theo thtng dyquan trong ong trc : MC3, MC2, MC1.

(Sa cha dao cach ly TG : sinh vin tthc hin)


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Chuy: Dao cach ly phai t ung chiu nh trong hnh am bao sau khi daocach ly ct ra th u li khng coin.

c. u - nhc im vapham vi sdung:* u im: - S n gian, gia thanh khng ln, DCL ch lam nhim vu tao

khoang cach an toan khi sa cha, ong ct luc khng codong in ngha lalam ungchc nng cua no. am bao an toan ngi ta dung cac bkhoalin ng dao cachly ch c ong ct sau khi MC act.

- S nay cho phep xy dng cac thit b phn phi tron b(KPY) thi cng lprap n gian, nhanh chong vavn hanh chc chn.

* Nhc im: tin cy cung cp in thp- sa cha thanh gop hoc dao cach ly thanh gop cua bt cmach nao cung u

phai ct tt cacac ngun ni vao thanh gop dn n mt in toan b.

- Khi sa cha may ct cua bt kymach nao th mach y phai ngng cung cp introng sut thi gian sa cha (cothvai ngay).

- Khi ngn mach trn thanh gop hay dao cach ly thanh gop tt cacac ngun u bct ra vanh vy toan bphutai u b ngng cung cp in .

- Khi ngn mach trn ng dy mamay ct trn mach y khng ct, th toan bcacmay ct cua ngun sect vacung dn n mt in toan b.

* Pham vi sdung: V nhc im trn nn s hthng mt thanh gop khng

phn oan chuyu dung trong cac thit b in cng sut nho, khng quan trong, comtngun cung cp vano con dung trong cac s in tdung cua nhamay in hoctram bin ap, nhng trong trng hp nay phai dung ngun dtr.

2. S Hthng mt thanh gop cophn oan :a.

Phn oan bnd dao cach ly:Thanh gop c phn thanh nhiu oan nhogoi lanhng phn oan vacac phn

oan nay c ni vi nhau bng dao cach ly phn oan.Thng sphn oan bng sngun cung cp vami mt ngun sec

ni vaomt phn oan, cac ng dy c phn bu trn cac phn oan.

S phn oan bng mt dao cach ly nh hnh 3-3a.Bnh thng dao cach ly phn oan CLpcothong hoc m, mi tnh trang vn

hanh cou - nhc im ring.

- Vn hanh vi dao cach ly phn oan ong:

+ u im: Ngun vaphutai phn bu, cahai phn oan lam vic song songam bao vn hanh kinh t.


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+ Nhc im: Khi congn mach trn mt phn oan bt kyth tt cacac mayct ngun u ct ra, toan bs b mt in. Khi ngn mach trn cac ng dy thdong ngn mach seln.

Thng chvn hanh nay c ap dung cac nhamay in.

- Vn hanh vi dao cach ly phn oan m:

+ u im: Khi congn mach trn mt phn oan nao th chi cophn oan obmt in, phn oan con lai vn lam vic bnh thng. Hn na khi ngn mach trnng dy th dong ngn mach sebehn nn ta cothchon kh cuin hang nhe.

+ Nhc im: Cac ngun vaphutai lam vic ring renn vn hanh khng kinh t.

Thng chvn hanh nay c ap dung cac tram bin ap.Khi phn oan bng mt dao cach ly (hnh 3-3a) th ta cothsa cha tng phn

oan hay dao cach ly thanh gop cua phn oan mach cophn oan ob mt in.V du:Sa cha phn oan IGiathit dao cach ly phn oan ang ong, khi osa cha phn oan I th ta

thc hin cac bc thao tac sau:- Ct tt cacac may ct mach ng dy vamay ct ngun ni vao phn oan I.- Ct cac dao cach ly thanh gop ni vao phn oan I.- Ct dao cach ly phn oan CLp(Ct luc codong in khng tai rt nho)- Thc hin cac bin phap an toan a phn oan I vao sa cha.Luc nay ch cophn oan I mt in con cac mach ni vao phn oan II vn lamvic bnh thng.* Giasang vn hanh vi dao cach ly phn oan ong th xut hin ngn mach

trn thanh gop, khi obao vrle sea tn hiu n ct tt cacac may ct ngun (MC3vaMC4)Toan bs b mt in. Luc nay nhn vin vn hanh phai xlynh sau:

- Ct tt ca may ct cua cac mach mabao vrle cha ct.

PI

N1

PII

N2Hnh 3.3a

Clp

MC5

CL51

CL52

MC1

CL12

CL11

MC2

CL22

CL21

MC4

CL42

CL41

MC3

CL32

CL31

MC6

CL61

CL62

D1 D2 D3 D4


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nhamay vaphutai u dung s mt hthng thanh gop c phn oanbng may ct . May ct MCp1thng ong, may ct MCp2thng m.

Tuy conhng u im trn nhng s h thng mt thanh gop phn oan bngmt may ct vn con nhng nhc im sau :

- Khi sa cha mt phn oan nao oth cac htiu thuquan trong seb mt ngundtr, con cac hcung cp bng 1 ng dy semt in hoan toan trong sut thi giansa cha.

Khi ngn mach trn 1 phn oan th cac may ct ni vao phn oan o ct ranhng tt ca cac ngun vn con tip tuc cung cp cho phn oan kia. S hnh 3-6c sdung rng rai cp (6 - 10) KV cua cac tram bin ap cln ng dy nhiu vathit b phn phi nhamay thuy in nho.3.S hthng mt thanh gop phn oan ni mach vong:

Trong thit b phn phi cp in ap may phat cua cac nhamay nhit in trung tmthng sdung s nh hnh 3-7.

- Khi ngn mach tai N2 th may ct MC1 vaMC3 ct P1 cua thanh gop TG2 b mt

in hoan toan.tng tin cy cung cp in mach

may ct phn oan P2 ngi ta thng trangb thm thit b t ng ong ngun d tr(TD), luc nay di tac dung cua thit bTD may ct phn oan Mcp2 ong lai P1 c cung cp in tng dy D2.

- Khi ngn mach tai N1 th may ctMCp1 va cac may ct co lin quan nphn oan I (PI) cua thanh gop TG1 b ctra, luc nay may ct phn oan hai MCp2 tng ong lai.

- Khi sa cha 1 phn oan semt bt nguncung cp. Co th khc phuc bng cach ni mtngun cung cp vao cahai phn oan bng hai mayct nh hnh 3-6 , nh vy sedn n thit b phnphi cng knh, t tin. Trong s nay khi cos

c trn ngun th cahai may ct cua ngun onivao 2 phn oan u b ct.

MCp1

MCp2TG2

TG1P1 P2

N2N1

MC1 MC2

MC4MC3

N2

N1

Hnh 3-5

D1 D2

N1 N2

MCp

Hnh 3-6


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- S nay las 1 hthng thanh gop c phn oan bng may ct, trong osphn oan bng sngun cung cp vacac phn oan c ni vi nhau qua khangin phn oan nhm han chdong ngn mach, con cac ng dy cp in ap mayphat thng c ly qua khang in ng dy.

- Tac dung cua khang in ng dy: Nh co khang in ng dy lam giamdong ngn mach khi xay ra ngn mach sau khang mata cothchon c cac kh cuinhang nhe(May ct hp b) sau khang. ng thi tao in ap d trn thanh gop khi congn mach trn ng dy sau may ct hp b.

n gian s vatng cao tin cy ngi ta thng dung khang in nhomhay khang in kep. u im cua khang in kep laco thcung cp cho nhiu ngdy mau ni vao thanh gop in ap may phat ch comt .

- Mach tdung c ly qua bin ap tdung (hoc qua khang in nu in ap tdung cung cp vi in ap may phat Utd = Uf). Khi s phn oan bng bn tr lnthng ni cac phn oan thanh gop thanh mach vong kn (hnh 3-7). Tac dung cua vicni mach vong:

- Nhni mach vong malam giam schnh lch in ap gia cac phn oan.V dukhi may phat mt phn oan bt kyngh th phutai phn oan osec

cung cp t hai pha, do o tn tht in ap qua khang in se be va cho phep chonkhang in phn oan codong nh mc behn trng hp khng ni mach vong.

- Nhni mach vong makhi cosctrn bt kyphn oan nao th cac may phatni vao cac phn oan con lai vn lam vic song song.

Trong s ni mach vong dong nh mc cua khang in phn oan thng chonbng (50-60)% dong nh mc cua may phat, con in khang bng (8-12)%.

%F2

B1

PII

%F4

B2

PIV

%F1

PI

%F3

PIII

CL1 CL2 CL4CL3

Hnh 3 - 7

CLK1

N1

Td Td Td Td

CL12CL11


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+ Thao tac sa cha dao cach ly phn oan CL12:- Ct tt ca cac may ct ni vao phn oan 2.- Ct tt ca cac dao cach ly ni vao phn oan 2.- Ct dao cach ly CL11.

- Thc hin cac bin phap an toan tin hanh sa cha dao cach ly CL12.+ Sau khi sa cha dao cach ly CL12 xong ta khi phuc lai slam vic cua phnoan 2 nh sau:

- Mni t an toan- ong tt cacac dao cach ly ang m.- ong tt cacac may ct ni vao phn oan 2 ( trmay ct mach may phat).- ong may ct mach may phat cn chuyn hoang b.+ Khi congn mach tai N1: Bao vrle a tn hiu ct cac may ct ni vao phn

oan 3 (May ct u ng dy n thng khng ct). Luc nay nhn vin vn hanhphai xlynh sau:

- Ct cac may ct mach ng dy mabao vrle cha a tn hiu ct.- Ct dao cach ly CLK1.- ong cac may ct ni vao phn oan 3.- ong may ct mach may phat F3 (chuyn hoang b)- Thc hin cac bin phap an toan sa cha sc.

Nhc im cua s : V comach vong nn thit b phn phi cng knh, phctap, t tin vakhokhn trong vn hanh.


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3.4.S Hthng hai thanh gop

1.

t vn :Sau khi phn tch svn hanh cua s mt hthng thanh gop ta nhn thy s

nay conhng nhc im c ban nh sau:-Khi sa cha thanh gop hoc dao cach ly thanh gop cua mt mach nao oth tt ca

cac mach ni vao thanh gop (hay phn oan) u phai ngng lam vic trong sut thigian sa cha.

-Khi xay ra ngn mach trn thanh gop th toan bcac mach ang lam vic se b mtin.

- Khi sa cha may ct cua mt mach bt kyth mch ob mt in trong sut thigian sa cha. khc phuc nhng nhc im nay ta dung s hai hthng thanh gop nhhnh sau.

2. M tas :

S gm hai hthng thanh gop TG1 vaTG2, conhim vudtrqua lai chonhau vac ni vi nhau qua mach may ct ni MCN.

Mi mach c ni vao hai HTTG qua mt may ct va ba dao cach ly (2 daocach ly thanh gop va1 dao cach ly nm vpha ng dy goi ladao cach lyng dy)

V du: ng dy D1 c bao vbng MC1; CL1 vaCL2 lacac dao cach ly thanhgop, CL3 ladao cach ly ng dy.

TG2

TG1

MCN

CLN1 CL2 CL1

CL3

MC1MC1

CLN2

D1 D2

B1

D3 D4

B2


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3. Cac chvn hanh:

Bnh thng thng s vn hanh song song trn hai thanh gop: May ct niong, cahai thanh gop u coin valam vic song song vi nhau ging nh s mththng thanh gop c phn oan bng may ct. Cac mach ngun vang dy cphn bu trn hai HTTG. V du: D1, D3 vangun B1 lam vic trn TG1 (cac dao

cach ly ni vao thanh gop 1 ong con cac dao cach ly ni vao thanh gop 2 m) conD2,D4 vaB2 lam vic trn TG2 (cac dao cach ly ni vao thanh gop 2 ong con cac daocach ly ni vao thanh gop 1 m).

(khi oMC1 ong, CL1 vaCL3 ong con CL2 ct, .....)

Trong mt s trng hp co thvn hanh trn mt thanh gop va thanh gop naygoi lathanh gop lam vic (TGLV), thanh gop con lai goi lathanh gop dtr( TGDT).Trong chvn hanh nay th may ct ni m, hai dao cach ly mach may ct ni cotnht mt dao m, cac dao cach ly ni vi TGLV ong con cac dao cach ly ni vi

TGDT m. Luc nay s vn hanh nh s mt hthng thanh gop khng phn oan.4. Cac thao tac c ban:Gia thit bnh thng s vn hanh song song trn haithanh gop: May ct ni ong, ng dy D1, D3 vangun B1 lam vic trn TG1 conng dy D2, D4 vaB2 lam vic trn TG2.

a. Thao tac sa cha thanh gop TG1:sa cha hthng thanh gop lam vic tacn thao tac chuyn tt cacac mach ang lam vic trn thanh gop nay vlam vic trnthanh gop con lai.

(Chuyn toan bcac mach vlam vic trn mt thanh gop TG2)- Khoangun thao tac cua MCN tranh ct nhm- ong cac dao cach ly thanh gop cua cac mach ang lam vic trn TG1 vao TG2- Ct tt cacac DCL cac mach ni vao TG1- Ct MCN vahai DCL hai bn- Thc hin bin phap an toan sa cha TG1b. Thao tac sa cha dao cach ly thanh gop CL1:sa cha dao cach ly th yu

cu hai u dao cach ly phai khng congha ladao cach ly ni vi thanh gop nao ththanh gop ophai mt in.

(Chuyn toan bcac mach vlam vic trn mt thanh gop TG2)

- Khoangun thao tac cua MCN tranh ct nhm- ong cac dao cach ly thanh gop cua cac mach ang lam vic trn TG1 vao TG2

(trdao cach ly mach ng dy D1)- Ct tt cacac DCL cac mach ni vao TG1- Ct may ct MC1 vadao cach ly CL3- Ct MCN vahai DCL hai bn- Thc hin bin phap an toan sa cha TG1c. Thao tackhi phuc slam vic cua cac mach khi sctrn mt thanh gop:


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Giasthanh gop TG1 b sc. Cac MC cua cac mach ni vao TG1 ct, MCN ct,TG1 mt in. Phai thao tac chuyn toan bcac mach trc y lam vic trn TG1 vlam vic trn TG2 theo trnh tsau:

- Ct tt cacac may ct cua cac mach ang lam vic trn thanh gop mt mabao vrle cha a tn hiu ct.

- Ct tt cacac dao cach ly thanh gop ni vao TG1- ong cac dao cach ly thanh gop cua cac mach vao TG2- ong cac MC cua cac mach vao TG2 theo thtngun trc, ng dy sau- Thc hin bin phap an toan sa cha TG1

Nh vy cac ng dy lam vic trn TG1 ch mt in trong mt khoang thi gianthao tac chuyn nosang lam vic trn TG2.

Nu nh ta cho vn hanh trn mt thanh gop th khi ngn mach trn thanh gop naytoan bs seb mt in. tranh iu nay xay ra ngi ta thc hin cac bin phap:

- Vn hanh song song trn hai thanh gop (TBPP in ap 35KV)- Phn oan thanh gop lam vic nh hnh di (s nay thng gp cac nhamay

in)

TGLV c phn thanh 2 phn oan laP1 vaP2. Hai phn oan ni viTGDT bng MCN1 vaMCN2 v tr thng ct.

Bnh thng cac mach c phn blam vic trn hai phn oan, ging nh smt HTTG cophn oan. TGDT bnh thng khng coin, noc dung coththay thtng phn oan mt cua TGLV khi cnsa cha.

Khi ngn mach trn mt phn oan, th phn oan osemt in. Sau ota thaotac chuyn cac mach trc dy lam vic trn P nay vlam vic trn TGDT.

TGDT

TGLV P1

MCN1

CL

CL

CL3

MC1MC1

D1

F1

D3 D4

F2

MCN2

Kp MCp

P2

D2


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d. Sa cha may ct cua mt mach:

Giass ang vn hanh trn mt thanh gop lam vic TGLV. Khi sa cha mayct MC1, co th thao tac dung MCN kt hp viTGDT tam thi thay thcho MC1theo trnh tsau: Kim tra thanh gop dtr

Ththanh gop dtrbng in (ong hai CL hai bn MCN vaong MCN)

Nu TGDT tt th ct MCN ra Ct MC1 vahai cach ly CL1 vaCL3

Thc hin bin phap an toan thao u ni cua MC1 valp cu ni CN (nh hnhve)

ong hai dao cach ly CL3 vaCL2 ong may ct ni MCN Chnh nh thng sBVRL cua MCN cho phuhp vi bao vcua ng dy D1.Nh vy khi sa cha may ct cua mt mach nao th mach ophai mt in trongthi gian khalu thao tac s , ta cothkhc phuc nhc im nay bng cach lpthm dao cach ly CLS. Khi otrnh tthao tac sa cha MC1 nh sau:

Kim tra thanh gop dtr Ththanh gop dtrbng in (ong hai CL hai bn MCN vaong MCN)

Nu TGDT tt th ong dao cach ly CLS Ct MC1 vahai cach ly CL1 vaCL3

Thc hin bin phap an toan thao u ni cua MC1

Chnh nh thng sBVRL cua MCN cho phuhp vi bao vcua ng dy D1.

TGDT

TGLV

MCN

F1

CL1

CL3

MC1

D1

CL2

CN

CL4CL5

CLS


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Rorang trong quatrnh sa cha may ct ng dy khng b mt in. Tuy nhin phailp thm dao cach ly CLS cho tt cacac mach lam cho thit b phn phi cng knhng thi khi sa cha may ct s phai vn hanh trn mt thanh gop nu luc nay xayra ngn mach trn thanh gop nay mt in toan b. Khc phuc ta dung s hai hthng thanh gop cothanh gop vong.

5. u - nhc im: Qua phn tch cac thao tac c ban cua s ta rut ra c cacu nhc im cua s nh sau:

a.

u im:

Cothln lt sa cha tng thanh gop mt mavn am bao cung cp in chocho phutai.

Cothln lt sa cha tng dao cach ly thanh gop cua mt mach bt kyth chcomach nay b mt in.

Khi phuc nhanh chong slam vic cua s khi congn mach trn thanh gop.

Khi sa cha may ct cua mt mach bt ky th mach o ch ngng lam victrong thi gian thao tac s .

b.Nhc im: Dao cach ly phai thao tac luc coin.


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3.5. Cac dang s ni in n gian

Khi smach ni vi cp in ap U = (35 220) KV t th ngi ta thng sdungs n gian. c im cua cac dang s nay lakhng xy dng hthng thanh gopcp in ap cao, slng may ct t thm ch cokhi khng cn t may ct cp in apcao cho nn giam nhiu chi ph vthit b in, vt liu xy dng vagiathanh thit bphn phi, ng thi thi gian thi cng cung nhanh chong.

1. Dang s bmay bin ap - ng dy: S bmay bin ap-ng dylamt trong nhng dang s n gian hoac sdung phbin cac tram bin ap.Trong s nay cac phn tcua bc mc ni tip vi nhau, khng colin hngangvi cac bkhac. Khi coh hong mt phn tbt kycua bth cabongng cungcp in.

Xet s b MBA-Dcua cac tram bin ap ni vao

ng dy chnh nh trnhnh 3-14.- ng dy D1 vamay binap B1 tao thanh mt b ( cot may ct MC2): Khi ngnmach trn ng dy tai im

N1 th cac may ct MC1 vaMC2 se ct dn n mt in

toan bs . Khi scmaybin ap th MC2 , MC3sect.Hnh 3 - 14

giam giathanh chi ph cua tram coththay thmay ct MC2pha cao ap cuamay bin ap bng dao cach ly tng CLt(hnh b). Trong trng hp nay mun sacha may bin ap th ct may ct MC3sau oct dao cach ly tng Clt luc nayCLtch ct dong in khng tai cua may bin ap, thao tac nay cho phep tuy thuc vaocng sut may bin ap vacp in ap. Hin nay vi may bin ap dung thep can ngui, cp in ap 35KV th dong khng tai Ikt1% Im, con cp in ap 110KV th Ikt

2,5% ImDo odao cach ly tng co th cho phep ct dong khng tai cua cac maybin ap cng sut ln. V duvi cp in ap (20 35)KV khi khoang cach hai cccuadao cach ly tng Clt d=(1,31,5)m th cho phep ct dong thoacua may bin ap co cng sut nhohn 40MVA ( may bin ap TD-40.000/35 co Io=0.65% Im=4.3A). cp in ap 110KV khi d=2,5 m , quy trnh cho phep ct dong khng tai cua MBA n80MVA ( TDH-80.000/110 co Ikt=1,5%Im=6.3A) .

Khi ngn mach trong may bin ap th bao vr le setac ng ct MC3sau oatn hiu n ct MC1( Tn hiu nay cothtruyn bng cap ring theo ng dy thng

tin hay ng knh cao tn cua cap cao ap) . Sau khi MC1 ct ra thdao cach ly tngCLt tng mra. Di tac dung cua thit b tng ong lp lai ng dy (TL)


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may ct MC1u ong dy chnh sec tng ong lai cung cp cho cac trambin ap khac.

Vic ct may ct MC1coththc hin bng cach khac makhng cn phai coxungi ct MC1 nh trn. Khi nay phai dung dao ngn mach NM t u cc cua maybin ap. Khi ngn mach trong may bin ap th bao vr le tac ng ct MC3 vaa tn

hiu ong dao ngn mach NM tao ngn mach nhn tao gia ng dy vi t, luc naydong ngn mach ln lam cho MC1sect tin cy. Sau odao cach ly tng CLtmravathit b TL tng ong trlai MC1cung cp cho cac bkhac.

Vic btr dao ngn mach tuy theo mang in : Trong mang trung tnh cach inth phai t dao ngn mach trn cahai pha tao ngn mach hai pha cham t, con trongmang trung tnh trc tip ni t th ch cn t mt pha tao ra dang ngn mach mtpha.

Mun ong may bin ap trlai ta thao tac nh sau :

- ong dao CL1pha cao ap vaong dao cach ly CL2pha haap.- ong dao cach ly tng CLt.- ong may ct MC3 .Dao cach ly CL1dung sa cha dao cach ly tng Clt .

Cn lu yla dao cach ly tng khng cn t nu tram bin ap latram cut.2. S cu:

B2B1

MC1 MC2

CL1 CL2

N1 N2

MC5

CL6CL5

S CU NGOAI

MC3

D1

MC4

D2

CL7 CL8

S nay cosmay ct t hn somach nhng tin cy cung cp in

vn cao, c sdung tai cac tram cohai ng dy vahai may bin ap, thccht lahai bng dy - may bin apco lin h ngang bng cu ni dungmay ct in.

Trong s cu may ct cothtv pha ng dy hoc v pha maybin ap, tuy thuc vao v tr may ctmata cohai loai s cu: S cu

trong vas cu ngoai.a. S cu ngoai: Las cu

co t may ct v pha may bin ap.Trong s nay pha may bin apB1, B2 c btr hai may ct MC3 vaMC4, con cac mach ng dy ch


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b tr dao cach lyCl7, CL8. mach cu ni ta t may ct MC5 ngoai ra con cocudao cach ly CL5 vaCL6 c sdung khi sa cha MC5.

- Ch lam vic bnh thng th may ct MC5 thng ong, Cl5 va CL6 m(hoc 1 ong, mt m). sa cha MC5 trc tin ta phai ong CL5 vaCL6 ri mict may ct MC5 vahai dao cach ly hai u may ct ri thc hin cac bin phap an toan

a MC5 ra sa cha.+ Khi schay sa cha mt may bin ap hoc may ct mach may bin ap th

hai ng dy vn lam vic song song.V du: Khi mun sa cha may bin ap B1

- Ct may ct MC1 vaMC3- Mhai dao cach ly hai u MC1 vaMC3.- Thc hin cac bin phap an toan sa cha may bin ap B1

Luc nay ngun N2 secung cp cho cahai ng dy qua may bin ap B2.

+ Khi xay schoc cn sa cha ng dy: Giassa cha ng dy D1- Ct cac may ct MC3 vaMC5may bin ap B1tam thi ngng cung cp in- Mdao cach ly CL7ng dy D1 hoan toan b cach ly- ong hai may ct MC3 vaMC5 trlai 2 may bin ap B1, B2 cung cp in cho

ng dy D2.- Thc hin cac bin phap an toan sa cha ng dy D1.

Sau khi sa cha xong mun ong lai ng dy D1 th phai thao tac nh sau:- Thao ni t an toan- Ct may ct MC3 vaMC5- ong lai dao cach ly CL7- ong lai cac may ct MC3 vaMC5.Pham vi sdung: Trong s cu ngoai thao tac ong ct mt may bin ap

n gian hn nhiu so vi ong ct mt ng dy. V vy s nay c sdung nhng tram bin ap coth phutai thay i nhiu, tai nhng giphutai cc tiu sectbt mt may bin ap nhm giam tn tht in nng vacac ng dy ni vao tram cochiu dai bexac sut scnho.

b. S cu trong: Las cu cot may ct vpha ng dy. Trong s nay

mi ng dy c bao vbng mt may ct ring con cao ap may bin ap khng dungmay ct madung dao cach ly. mach cu ni ta t may ct MC5 ngoai ra con cocudao cach ly CL5 vaCL6 c sdung khi sa cha MC3, MC4, MC5.- Chlam vic bnh thng th may ct MC5 thng ong, Cl5 vaCL6 m(hoc

mt ong, mt m).- Khi coschoc cn sa cha ng dy: Giascn sa cha ng dy D1

+ Ct MC3+ Ct hai dao cach ly hai u MC3

+ Thc hin cac bin phap an toan sa cha ng dy D1.


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Luc nay cac may bin ap B1 va B2 vn lam vic bnh thng cung cp in chong dy D2.- Khi xay ra sctrong may bin ap B1: MC1, MC3, MC5 ct ra ng dy

D1 b mt in. khi phuc lai slam vic cua ng dy D1 nhn vin vn hanh phaict dao cach ly CL1 sau oong lai may ct MC3 vaMC5 ri thc hin cac bin phapan toan sa cha may bin ap B1.

- Khi cn sa cha may bin ap B1: Ct may ct MC1 sau omdao cach ly CL1,nh vy CL1 phai ct dong khng tai cua may bin ap nn ta cn phai kim tra khanngct cua dao cach ly CL1 theo iu kin: IcdclI0. Nu khng thoaman th ta phai thao

tac nh khi scmay bin ap.Pham vi sdung: Trong s cu trong vic thao tac ong ct ng dy n

gian hn nhiu so vi vic ong ct mt may bin ap v vy s c sdung nhngtram BA t ong ct may bin ap coTPT bng phng, ng dy dai, xac sut sscln.Trong cahai s cu cach ly CL5-CL6 c dung khi sa cha hoc kim tra bt kymt trong 3 may ct: MC3, MC4, MC5. chvn hanh bnh thng 2 dao cach lynay: 1 ong, 1 m. Mun sa cha may ct (MC3):

+ ong dao cach ly ang m.+ Ct MC3 cn sa cha mcac dao cach ly lp kem theo vi MC3.

B2B1

MC1 MC2

MC3

CL1 CL2

N1 N2

CL3 MC5 CL4

S CU TRONG

CL6CL5

D1 D2

MC4


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+ Thc hin cac bin phap an toan sa cha MC3.Lc nay MC4 sebao vcho cahai ng dy D1 vaD2, luc nay nu ngn mach trnng dy D1 hoc D2 th MC2 sect lam mt in toan b.

- Mun sa cha MC5 :+ ong dao cach ly CL5, CL6.

+ MMC5 vahai dao cach ly hai u.+ Thc hin cac bin phap an toan tin hanh sa cha .Luc nay nu xay ra ngn mach trn bt kyng dy nao th cahai may ct MC3 va

MC4 u ct dn n mt in toan b.


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3.6. S a giac

c im s : Smay ct bng smach bng scanh cua a giac nhng mi mtmach lai c bao vbng hai may ct do ocothln lt sa cha cac may ct makhng b mt in.

- u im: mc dumi mt mach c bao vbng hai may ct nhng smay ct vnbng smach nn giathanh thit b phn phi segiam.- Trong s a giac cac may ct ni vi nhau thanh mach vong nn con goi la s

vong, s a giac n gian nht las tam giac.a. S tam giac :

Luc nay ng dy D1 vn c bao vbng may ct MC3.Nhn Xet: Trong s nay dao cach ly ch dung tao khoang cach an toan ng

thi khi cn kim tra sa cha may ct khng phai thao tac s nhiu nn s co

tin cy cao.Nhc im: Khi sa cha may ct mach vong b hnu luc nay nu ngn machxay ra trn ng dy D2 th may ct MC2 sects sengng lam vic.- Ngn mach trn ng dy D1 hoc sa cha D1 yu cu phai ct MC1 vaMC3 sau

omdao cach ly CL1, duy tr may ct dtrta cho ong lai MC1 vaMC3.- Nu ngn mach trn ng dy D1 mamt trong hai may ct MC1 hoc MC3 khng

ct mt in toan b. y lanhc im ln cua s bao vbng hai may ct,khc phuc ta phai thng xuyn kim tra may ct matrong s nay vic kimtra may ct c thc hin ddang.

MC3

MC2MC1

D2D1

N

S TAM GIAC

- c sdung khi co3 mach (1 ngun vahaiphutai)

- Mi may ct tao thanh mt canh cua tam giac

con cac ng dy vangun ni vao cac nhcua tam giac.-

Vn hanh bnh thng: Cac dao cach ly vamay ct v tr ong, mi mach c bao vbng hai may ct (ng dy D1 c baovbng hai may ct MC1 vaMC3)

- u im: Co th ln lt kim tra sa chatng may ct mt makhng comach nao bmt in.V du: Kim tra may ct MC1: Ct may ctMC1, mdao cach ly hai u may ct MC1va thc hin cac bin phap an toan amay ct MC1 ra kim tra.


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u im: tin cy cao, tit kim c may ct nn kinh t (Khi sa cha mayct thao tac n gian khng b mt in)-Nhc im:

+ Khng thtng thm smach+ Phai chon dong lam vic nh mc cua may ct theo iu kin lam vic cng

bc khi sa cha mt may ct.+ Bao vrle phc tap v phai bao vcho mach vong.

b. S tgiac: S tgiac lamt dang cua s a giac co4 may ct dung bao vcho 4 mach. Mi mt mach c bao vbng hai may ct nn khi sa cha kimtra mt may ct bt kyth khng b mt in.

- Mun kim tra sa cha MC1:+ Ct may ct MC1, mhai dao cach ly hai u may ct MC1.+ Thc hin cac bin phap an toan sa cha.

Mach vong b h.

- Mun kim tra ng dy D1:

+ Ct may ct MC1 vaMC2 ri mdao cach ly CL1.+ ong lai MC1 vaMC2 duy tr mach vong kn.

S TGIAC

D1

MC2

N1

B1

CL

B2

N2

CL4

MC1

MC4

MC3

CL1CL2

D2


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- Sa cha may bin ap B1 ( SV tthc hin)Chuy: Phai ct cac may ct vadao cach ly pha haap may bin ap B1, nu B1 ni

vi may phat th phai dng may phat trc khi thc hin cac bin phap an toan nh nit...

* u im: S n gian, t may ctkinh t, ddang sa cha kim tra may

ct.* Nhc im:

+ Nu ngn mach trn mt mach nao ov dung dy D1 mamt trong hai mayct MC1 hoc MC2 khng ct, chng han MC2 khng ct th MC4 ctB1 ngnglam vic, khc phuc phai thng xuyn kim tra may ct.

+ Phai chon dong lam vic nh mc cua may ct theo iu kin lam vic cn bckhi sa cha mt may ct.

+ Bao vrle phc tap v phai bao vcho mach vong.

c s dung rng rai cac cp in ap 110 KV tr ln nht la cac tram500KV


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3.7.S Hthng mt thanh gop cothanh gop vong

S 1 hthng thanh gop conhc im lakhi sa cha may ct cua 1 mach btkyth mach ophai mt in trong sut thi gian sa cha, khc phuc nhc imnay ngi ta sdung s 1 hthng thanh gop coTGV, s nay c sdung rng

rai cp in ap 35KV.

1. M tas :Trong s nay hthng thanh gop c phn thanh hai phn oanbng MCp. Mi phn oan lin lac vi TGV qua 1 mach may ct vong.- May ct vong MCV1 (hoc MCV2) c ni vi h thng thanh gop (HTTG)

lam vic qua dao cach ly CLV1 (CLV3) va ni vi thang gop vong qua dao

cach ly CLV2 (CLV4).- Cac mach ng dy vamay bin ap ni vi HTTG lam vic qua 2 dao cach ly:

Mt dao cach ly thanh gop va mt dao cach ly ng dy hoc may bin ap(ging nh s mt h thng thanh gop) va c ni vi thanh gop vong(TGV) qua DCL vong.

- Phn oan cua HTTG lam vic lin lac vi nhau qua may ct phn oan (MCp)vahai DCL: CLp1vaCLp2.

Ta thy s nay vc ban ging s hai HTTG nhng cothm mach MCVvaHTTG vong.

B1 B2

MCV1 MCV2

P1 P2MC

TGV

MC1

CL1V

CL2

CL1

D1

CLV3

CLV2

CLV1

CLp2CLp1


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* Nhim vucua MCV vaTGV: MCV kt hp vi TGV cothkim tra hoc sacha MC cua 1 mach bt kymavn am bao cung cp in cho mach o.

MCV1 coththay thcho 1 may ct cua bt kymach nao trn PI.MCV2 coththay thcho 1 may ct cua bt kymach nao trn PII.Lu y: TGV khng phai ththay thcho 1 phn oan cua thanh gop lam vic.

2. Trang thai vn hanh bnh thng:+ Tt cacac dao cach ly ni vi thanh gop vong u m.+ MCV vadao cach ly 2 u cua nom.Do oTGV bnh thng khng coin.+ MCp ong, s vn hanh ging nh s 1 HTTG c phn oan bng may

ct.

V du: sa cha may ct MC1 ta phai thc hin trnh tcac bc thao tac :- Quan sat vakim tra TGV bng mt nu khng phat hin nhng hong hoc ln

th chuyn sang bc kim tra bng in.- Kim tra bng in:

+ ong 2 dao cach ly hai u MCV1.+ ong MCV1 (lu y: Bao vrle cho MCV c chnh nh vi thi gian tac

ng nhonht). Nu TGV b scth MCV1 sect ra ngay, nu TGV tt th ta thchin cac bc thao tac tip theo :

- Ct MCV1 ra trlai.- ong dao cach ly CLV1, chuyn BVRL cua MC1 cho MCV1.

- ong MCV1 ri ct MC1 vahai dao cach ly CL1, CL2.- Thc hin cac bin phap an toan sa cha MC1.

Luc nay MCV1 lam nhim vubao vcho D1 thay cho MC1.giam giathanh cua s ngi ta cothdung 1MCV ni vao 2 phn oan nh hnhdi y.

Trang thai vn hanh bnh thng:- MCV thng m.- Hai dao cach ly CL3 vaCL4 cot nht mt dao cach ly m(nu cahai dao cach ly

u ong th MCp khng con tac dung).Do oTGV bnh thng khng coin.

- MCp ong, s vn hanh ging nh s 1 HTTG c phn oan bng may ct. Khi cn sa cha may ct ni vao phn oan nao th dao cach ly cua mach MCV

tng ng vi phn oan oong, dao cach ly ni vi phn oan con lai m.- V du: Sa cha may ct MC1:

+ Kim tra thanh gop vong bng mt+ ong dao cach ly CL4 vaCL5.+ ong MCV ththanh gop vong bng in.


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Nu thanh gop vong tt th ta mMCV vaong dao cach ly CL3, sau oong laiMCV.

+ Ct may ct MC1, m2 dao cach ly CL1 vaCL2 .+ Thc hin cac bin phap an toan sa cha may ct MC1.

Sau khi sa cha xong MC1, SV thc hin thao tac a MC1 vao vn hanh.

Thao tac sa cha phn oan I (SV thc hin).Khi sa cha phn oan I th phn oan nay phai mt in, tt cacac mach ang lamvic trrn phn oan I u b mt in nh tinh thn s mt hthng thanh gopphn oan. Tuy nhin y chung ta nhcoTGV vaMCV nn chung ta cothduytr slam vic trn phn oan I (thng lamach ngun).

B1

MCV

P1

B2

P2MC

TGV

MC1

CL1V

CL2

CL1

CL3 CL4

CLV

D1


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3. 8. S Hthng hai thanh gop cothanh gop vong

Sau khi phn tch svn hanh cua s hai hthng thanh gop ta nhn thy trongs nay khi cn sa cha may ct cua mt mach bt kyth mach otam thi b mtin trong thi gian thao tac sdung may ct ni thay thcho may ct cua mach nay

vacac bc thao tac tng i phc tap. i vi cp in ap 110 KV, khi smach nivao thanh gop nhiu cn phai thng xuyn kim tra sa cha may ct tng tin cycung cp in va giam s lng thao tac s ngi ta s dung s hai HTTG coTGV.

1.

M tas :

Trong s nay:- May ct vong (MCV) c ni vao hai hthng thanh gop (HTTG) qua hai dao

cach ly CLV1, CLV2 vani vi thang gop vong qua dao cach ly CLV3.- Cac mach ng dy vamay bin ap ni vi hai HTTG qua 3 dao cach ly: Hai

dao cach ly thanh gop (ging nh s hai hthng thanh gop) vac ni vithanh gop vong (TGV) qua DCL vong.

- Hai HTTG ni vi nhau qua may ct ni (MCN) vahai DCL: CLN1 vaCLN2.Ta thy s nay vc ban ging s hai HTTG nhng cothm mach MCV

vaHTTG vong.

B1

N1

B2

N2

CL1V

CL13

CL11

CL12

MC1

CL2V

CL23

CL21

CL22

MC2

CLV3

CLV1

CLV2

MCV

MCN

CLN2

CLN1

TGV

TG1TG2

D1 D2

Hnh 8-1


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* Nhim vucua MCV vaTGV:MCV kt hp vi TGV lam nhim vuthay thchomay ct cua mt mach bt kykhi cn kim tra sa cha mach nay (TGV khng ththaythcho thanh gop lam vic).

2. Vn hanh s :

a. Trang thai vn hanh bnh thng:- Tt cacac dao cach ly ni vi thanh gop vong u m.- MCV trang thai m, cac dao cach ly CLV1 vaCLV2 cothmt ong, mt

mhoc cahai u m.- MCN ong, s vn hanh song song ging nh s 1 HTTG c phn

oan bng may ct, cac mach ngun vaphutai c phn bu cho cahaithanh gop.

Giasng dy D1 vamay bin ap B1 lam vic trn thanh gop TG1,ng dy

D2 vamay bin ap B2 lam vic trn thanh gop TG2.b. Sa cha may ct cua mt mach bt ky( giassa cha MC1)Cac bc thao tac sa cha MC1 nh sau:

- Kim tra TGV:+ Kim tra TGV bng mt phat hin nhng hong hoc ln nh ran nt s,...+ Kim tra TGV bng in: ong dao cach ly CLV1, CLV3 ri ong MCV.

Nu TGV b scth MCV sect ra vi thi gian gn bng khng, nu TGV lam

vic tt th ta thc hin tip cac bc thao tac sau:- Ct MCV vachnh nh thng sBVRL cua MCV ging nh may ct MC1.- ong dao cach ly CL1V.- ong may ct MCV.- Ct may ct MC1.- Ct dao cach ly CL13 vaCL11.- Thc hin cac bin phap an toan sa cha may ct MC1.Luc nay MCV sebao vcho ng dy D1 thay cho may ct MC1.Nh vy khi sa cha may ct MC1 th ng dy D1 vn c cung cp in va

2 HTTG vn vn hanh song song.* Chuy: Khi sa cha CL13 hoc CL1V th ng dy D1 bt buc b ngng cung

cp in.

giam giathanh cua s ngi ta dung mt MCVN thay v phai dung MCVvaMVN ring s nh hnh 8-2.

MCVN ch co th thc hin mt trong hai nhim vu: Hoc lam nhim vuMCV

hoc lam nhim vuMCN .


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Bnh thng s vn hanh song song nn MCVN lam nhim vuMCN, luc nay cacdao cach ly CLV3, CLV2 mvacac dao cach ly CLV1, CLN ong.

Khi cn sa cha may ct cua mt mach nao th ta phai chuyn s vvn hanhtrn mt thanh gop MCVN co th thc hin nhim vuMCV ( kt hp vi TGV thay thmay ct cn sa cha).

Khi may ct MCVN lam nhim vuMCV thay thcho may ct cua mt mach thCLN m, CLV3 ong con CLV1 vaCLV2 secomt dao ong, mt dao mtuythucvao may ct cn sa cha ang lam vic vi thanh gop nao.Khi smach nhiu thao tac chuyn thanh gop mt nhiu thi gian vatng

tin cy cung cp in th ngi ta sekhng tit kim masdung MCV vaMCN ring.

B1

N1

B2

N2

CL1V

CL13

CL11

CL12

MC1

CL2V

CL23

CL21

CL22

MC2

CLV3

CLV1

CLV2

MCV

CLN

TGV

TG1

TG2

D1 D2

Hnh 8-2


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Trong s nay : Dao cach ly ch thao tac khng in nn vn hanh an toan, tnham bao cao.

- Nhc im : Smay ct nhiu, khi co1 mach leth phai co1 mach c bao vbng hai may ct nn tng thm smay ct do ogiathanh s tng.

3.10. Mt sdang s cua Nhamay in vatram bin ap


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Nhom Nhamay i

S NhamayNhit in ngng hi


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Nhom Nhamay i

S NhamayNhit in trch hi


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Nhom Nhamay i

S Nhamay Thuyin


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Nhom Nhamay i

S Tram bin ap


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Nhom Nhamay i

Tram b


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Nhom Nhamay i

S Tram bin ap trung gian


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Chng 4

MAY BIN AP IN LC

4.1. Mu

4.1.1 Khai nimMay bin ap (MBA) lamt thit b in ttnh, lam vic da trn nguyn lycam ngin tthc hin nhim vubin i in nng tcp in ap nay sang cp in ap khaccho phuhp vi yu cu truyn tai vasdung in.

in nng c truyn tai tnhamay in (NM) n htiu thuthng qua nhiuln bin i in ap bng cac may bin ap tng vagiam ap. Do otng cng sut t cuamay bin trong h thng in thng gp (4 - 6) ln tng cng sut cac may phat cotrong hthng. Mc duhiu sut MBA tng i cao (98%) nhng tn tht in nng

hang nm trong may bin ap vn rt ln. V vy ngi ta mong mun giam sbc maybin ap, giam cng sut t may bin ap vasdung chung at hiu quacao hn. iunay coththc hin c bng cach thit khthng in hp ly, sdung may bin apt ngu trong nhng mang in thch hp va tn dung kha nng tai cua may bin ap,khng ngng cai tin cu tao may bin ap gop phn nng cao tin cy va tit kimnguyn vt liu.

Xu thhin nay ngi ta chtao MBA vi cp in ap cao vathay i cu truc

tng cng sut n v, vi vic sdung thep can ngui cocach in tt vahthng lammat tt ngi ta cothchtao nhng loai MBA cocng sut n v ln. Tuy nhin cngsut n v con b han chbi kch thc, trong lng vaiu kin chuyn ch, ngaynay ngi ta achtao c MBA cac csau :

MBA ba pha : in ap (220 - 330) KV Cng sut 630 MVAin ap 500 KV Cng sut 1.200 MVA

MBA tngu : in ap 500 /110 KV Cng sut 1.500 MVAMBA mt pha : in ap 500 KV Cng sut 1.600 MVATrong thc tngi ta cgng chon MBA ba pha v tn tht trong MBA ba pha be

hn trong MBA mt pha cocung cng sut t(12 - 15) %, kch thc, trong lng, gathanh cung giam so vi MBA mt pha. V vy khi khng chon c MBA ba pha michon MBA mt pha .

4.1.2 Phn loai may bin ap

- Phn loai theo spha: May bin ap 1 pha (O), may bin ap 3 pha (T).

- Phn loai theo scun dy gm co:

+ MBA ba cun dy (T)+ MBA hai cun dy .


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Ngoai ra con coloai MBA cocun dy phn chia haap, thng sdung khicn ni bmt smay phat vao MBA vanhvy lam giam c kt cu thit b phnphi hoc c dung trong s tdung cua nhamay in vacac tram giam ap nhmgiam dong ngn mach pha haap.

- Phn loai theo phng phap lam mat gm co:

+ May bin ap kiu kh: Cach in lain mi rn, lam mat bng khng kh (C).+ May bin ap kiu du: Cach in vami trng lam mat chuyu ladu.

Lam mat tnhin bng du (M)

Lam mat bng du tun hoan tnhin vacoquat gio().Tun hoan cng bc du coquat gio()

Tun hoan cng bc cua nc vadu coquat gio()- Theo phng phap iu chnh in ap: May bin ap thng, may bin ap diu ap

di tai (H).V du: May bin ap Lin X ky hiu: ATTH 100/220: May bin ap t ngu ba

pha, ba cun dy iu ap di tai, lam mat bng du tun hoan cng bc coquat gio,cng sut nh mc 100 MVA - in ap cao 220 KV.

4.2. Cac thng scua may bin apCac may bin ap c tnh toan, chtao vi mt chlam vic lu dai valin tuc

nao ogoi lach nh mc, y la ch lam vic cua may bin ap ng vi cac

thng svaiu kin nh mc: in ap U = Um, tn s f = fm, cng sut S = Smvaiu kin mi trng nh khi tnh toan thit k( tmt= ttk).

4.2.1 . Cng sut nh mc may bin apCng sut nh mc lacng sut toan phn ( biu kin) c nhamay chtao qui

nh trong lylch MBA. May bin ap cothtai c lin tuc cng sut nay (S = Sm )khi in ap laUm, tn slafmvaiukin lam mat lanh mc vakhi otui thocuaMBA sebng nh mc .- i vi MBA hai cun dy cng sut nh mc lacng sut cua mi cun dy.

- i vi MBA ba cun dy ngi ta cothchtao cac loai sau:+ 100/100/100 la loai co cng sut cua mi cun dy u bng cng sut nh

mc.+ 100 /100 /66,7 laloai cocng sut cua hai cun dy bng cng sut nh mc va

cng sut cua cunthba bng 66,7% cng sut nh mc .- i vi MBA tngu th cng sut nh mc lacng sut cua mt trong hai u

s hoc thcp mahai u nay co lin h tngu vi nhau, cng sut nay con goi lacng sut xuyn .

4.2.2. in ap nh mcin ap nh mc cua may bin ap lain ap cua cac cun dy khi khng tai cqui nh trong lylch may bin ap .


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T sbin i in ap :

m

m

UTSU

K= Goi laT sbin ap .

4.2.3. Dong in nh mc

Dong in nh mc ladong in cua cac cun dy c nhamay chtao qui nh,vi cac dong in nay th may bin ap lam vic lu dai makhng b quatai. Dong innh mc xac nh nh sau:

mi

mimi

3U

SI =

4.2.4. in ap ngn mach Un%in ap ngn mach lain ap gia hai u cun s cp khi ngn mach cun thcp

th dong in trong cun dy s cp bng dong in nh mc.

Yngha :in ap ngn mach c trng cho in ap ri trn tng tr cun dyMBA khi dong chay trong cun dy bng dong nh mc vadung xac nh tng trcun dy MBA. Khi Um, Smtng th Uncung tng.

V du: Vi Uc = 35 KV ; Sm = 630 KVA th Un = 6,5 % .Uc = 35 KV ; Sm = 80.000 KVA th Un = 9 % .

Khi Un tng th giam c dong ngn mach nhng setng tn tht cng sut, tn thtin ap trong may bin ap vagiathanh MBA cung tng .

- UN% lat lphn trm in ap ngn mach so vi in ap nh mc.

100.U

U%Udm

NN = [%]

UNc xac nh bng th nghim ngn mach: ( s nh hnh sau)

Ni tt cun dy thcp, tng in ap ngun a vao cun dy s cp cho n khich strn Ampe kbng dong nh mc th giatr UNchnh lach strn voltmet.

- Khi ngn mach UNrt nhonn tthng trong may bin ap cung rt nhongha lata xem nh dong khng tai I0= 0, trong s thay thta cothbonhanh xm-rm.

Ta co: UN% = .100U

.ZI

m

m

m

=%100.U

UN [%]

V

A

UNUN

xm

rm

Xn= x1+x2'

rn = r1+r2'

Im


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Z = .100I%.UU

m

mN []

Chuy: Khi th nghim ngn mach in ap t vao hai u cun dy s cp nhonndong in bng dong nh mc nhng khi ngn mach scin ap h thng cogiatr

ln nn dong ngn mach rt ln.4.2.5. Dong in khng tai Io%

Dong in khng tai laai lng t trng cho tn hao khng tai cua MBA, phuthuc tnh cht t, cht lng cung nh cu truc lp ghep cua loi thep. Ngay nay ngita sdung thep tt chtao MBA nn dong I0giam

I0% biu th bng phn trm so vi dong in nh mc ImQuan hgia dong khng tai vatn hao khng tai:

.100S

Q.100

S

S.100

S

.I.U3.100

U3/S

I.100

I

I%I

m

Fe

m

0

m

0m

mm

0

m

0

kt ====

Tr scua dong khng tai c xac nh nhth nghim khng tai: Ta cho hmachcun thcp vaa vao cun s cp in ap bng in ap nh mc th giatr dong ino c mach s cp chnh lagiatr dong khng tai.

4.3.6. Tu dy cua may bin apTrong cac may bin ap ba pha cac cun dy cothni lai vi nhau thanh hnh sao

(Y), tam giac () hay ni ziczag. Khi ni sao ta ly ba u cui ni chung vaba u conlatdo ( hnh a), ni tam giac th u cui cua pha nay ni vi u u cua pha kia(hnh b). Khi ni ziczag cun dy cua mi pha c chia lam hai na vac qun trnhai trukhac nhau, hai na nay c ni ni tip ngc nhau (hnh c).

Kiu ni ziczag rt t dung v tn nhiu ng hn vach gp trong cac may binap dung cho thit b chnh lu hoc trong cac may bin ap o lng hiu chnh sai svgoc lch pha.Thng thng cac may bin ap hay dung cac tu dy Y/Y0, Y/, Y0/ (Y0 cac cundy c ni theo hnh sao vatrung tnh ni t trc tip).

Vy : Tni dy cua may bin ap c hnh thanh do sphi hp kiu ni dy scp so vi kiu ni dy thcp vanobiu th goclch pha gia in ap dy s cp vathcp cua may bin ap.

V

A

UmI0

Um

xm

x1

r1

I0

rm


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Ngi ta qui c biu th tu dy MBA da vao goc lch pha sc in ng cuapha s cp E1 vathcp E2 .

Goc lch pha bin thin t0 n 360 , ly n v la30 , cho nn tu dy

cothtt0 n 11 vathng dung kim ng hbiu th: Kim gicua ng hbiuth vect in ap dy s cp t cnh con s12, kim phut biu th vect in ap thcp tng ng cac con s1,2, ... 12 tuytheo goc lch pha gia cac in ap nay la30,60,...360.

i vi MBA ba pha khi ni Y - Y th tu dy chn 0, 2, 4, 6, 8, 10; khi u Y -th tu dy le1, 3, 5, 7, 9, 11 .

Vit nam vaLin x thng sdung tu dy Y - Y/ 0 vaY-/11. Cun caoMBA thng ni hnh Y con cun hathng ni hnh tam giac v cac lydo sau:

- Khi ni hnh sao th in ap t ln cun dy: 3

U

UU dfcd == . Do ocach in

cua cac cun dy c tnh toan thit ktheo theo in ap pha cho nn cach in hangnhe, gia thanh giam. Hn na pha cao ap dong in lam vic bnh thng nho (

=

d

dU.3

SI ) nn khi ni sao mc dudong chay qua cun dy ( Icd= Id) tng 3 ln

so vi khi ni tam giac nhng tit din dy qun cung khng tng ln nhiu. Cun dy ni sao thng ly ra im trung tnh khi cn ta ni t trung tnh.- Khi ni tam giac th dong chay trong cun dy giam i 3 ln (Icd =Id/3) nn ch

cn tnh toan tit din dy qun theo If, mai vi cp in ap thp dong in lam vic

A

B

A

CHnh a

A B C

X Y Z

A B C

X Y Z

B C

X Y Z

Hnh a Hnh b Hnh c

B

A,Y

C

B,Z

X,CHnh b Hnh c


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bnh thng ln nn khi chtao madong in tnh toan giam i 3 ln th setit kimc mt khi lng ln kim loai mau.

Ngoai ra khi cun hamay bin ap ni tam giac con co tac dung khep mach cacsong hai bc cao cua dong thoakhi cohin tng bt i xng tai hoc ngun. Nhvy cac thanh phn dong in bc cao khep vong trong cun tam giac makhng chaytrong mang.

Thng i vi MBA cocp in ap U 220 KV vaMBA tngu th trung tnhbt buc phai ni t trc tip . Hin nay Vit nam mang 110 KV trln u ni ttrc tip im trung tnh, tuy nhin giam dong ngn mach mt pha ngi ta co thkhng ni t mt sim trung tnh nhng khi ocn phai t chng set van im

trung tnh bao vkhi coset anh vao MBA trn caba pha, thng chon cp in apcua chng set van nhohn in ap nh mc cua MBA mt cp.* Gian vect vacach u dy cua hai tni dy Y-Y/0 vaY-/11:

- Tu dy Y-Y/0:

- Tu dy Y-/11:

Z

z

A B C

X Ya

b c

x y

A.E

a

.

E

Hnh 1

A

.

E

B

.

EC

.

E

AB.U

a

.

E

c

.

E b.

E

ab

.

U

A

UdUcd

A

B

C

Id

IcdUd

A

B

C

Id

Icd

Ucd

CB


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ITladong in chay trong ng dy pha UTIchladong in trong cun chung:

Ich= IT - IntGiathit boqua tn tht trong MBA:

S=UC.IC=UT.ITHay cothvit lai:

S={(UC-UT )+UT}. IC= = (UC-UT ).IC+ UT.ICt: SBA= (UC-UT ).IC la cng sut truyn tCA sang TA bng quan hin t,

goi lacng sut bin ap.S = UT.IClacng sut truyn tCA sang TA bng quan hin, goi lacng

sut in.Nh vy : S = SBA+ S; ngha lalng cng sut S truyn tai tbn cao ap sang

trung ap bng hai quan h:- Quan hcam ng in tvi lng cng sut laSBA; khi ocun ni tip vacun

chung c xem ln lt lacun s vath trong may bin ap thng.- Quan hvin gia hai cun cao ap vatrung ap vi lng cng sut laS

Nu mba lam vic ch nh mc (in ap, dong in trong cac cun dybng nh mc va cng sut xuyn bng nh mc S=Sm), th t l gia cng suttruyn tai bng quan htso vi cng sut xuyn (nh mc) sebng:

cl

BAC

T

CC

CTC

dm

BA KK11

UU1

IUIUU

SS ====

.).(

trong oKcl c goi lahscolicua may bin ap tngu

Nh vy, chnh mc th phn cng sut truyn tai tCA sang TA bngquan hin tch bng (Kcl.Sm). V vy kch thc mach tc chon theo cngsut nay , vagoi lacng sut mu:

Smu = Kcl.Sm

V Kcl


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Nh vy loi thep cung nh cac cun dy ni tip vacun chung, u c thit ktheo Smu nn nocon goi lacng sut tnh toan:

Stt = Smu = Kcl.SmKhi Kcl cang nhoth may bin ap tngu cang coliV duMBA tngu 220/110KV cng sut nh mc 100MVA th loi thep vacac

cun ni tip vacun chung ch cn ch tao theo Sm=50MVA ( bng loi thep vacaccun dy cua MBA thng coSm=50MVA)

may bin ap tngu ba pha, ngoai cun cao ap va trung ap ni Yo, ngi tacon chtao thm cun dy haap ni tam giac.

V cun haap dc qun ring bit, nn noch coquan hcam ng in tvihai cun CA vaTA. V kch thc mach tch chtao theo cng sut mu nn cng sutcua cun HA cung ch c thit kcocng sut khng ln hn cng sut mu SmHA

Smu (thng thng labng). Ngoai ra cng sut chtao cua cun hakhng c nhohn 25% cng sut nh mc, v nu nhohn th cun haap sekhng am bao n nhng khi ngn mach ngoai.

0,25 SmSmHASmuCun haap nay c dung ni may phat, hoc cung cp cho phutai, hoc ni

thit b bucng sut phan khang, hoc dung cung cp in tdung.... hoc ch dungkhep mach cac song hai bc cao chuyu labi ba.

may bin ap tngu giam ap cun dy c btr trn loi thep theo thtHA-

TA-CA, khi oun%H-C=2530% secotac dung giam c dong in ngn mach; con ivi cac may bin ap tng ap th cac cun dy c btr theo thtTA-HA-CA, khi nayun%H-C=1013% secotac dung lam giam in khang x, do oselam giam tn tht inap vacng sut. Hin nay ngi ta achtao cac may bin ap tngu dung c cho cahai trng hp tng ap hoc giam ap. Chng han TN 220/110/HA coUN (C-T)=11%, UN(C-H)=20% vaUN(T-H)=32%

4.3.2. Cac chlam vic cua may bin ap tngu

May bin ap tngu coth lam vic cac chsau:

H T C

a

x

XAT

AC

a/ MBA giam ap

T H C

X

x

aAT

AC

a/ MBA tng ap


63/138


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Ich=IT-ICCng sut tai cua cun ni tip:

Snt = Unt.Int= (UC-UT).IC= Kcl.UcIc=Kcl.S ;Cng sut tai cua cun chung:

Sch= UT.Ich= UT(IT-IC) = Kcl.S ; Cun ha Sh=0c bit, nu cng sut truyn tai bng cng sut nh mc cua TN (S=Sm), th:

Snt = Sch= Kcl.Sm = Smu; Sh=0

Nh vy, mc du cac cun dy va loi thep c ch tao bng cng sut munhng may bin ap tngu vn cho phep truyn tai mt lng cng sut bng Sm tCA sang TA va ngc lai. Khi o mi cun dy ni tip va cun chung va y taingha labng cng sut chtao Smu.

Snt = Sch= Kcl.Sm = Smu; Sh=0

2. Chbin ap:a. Truyn cng sut tHA sang CA, pha TA khng tai:

Giathit boqua tn tht :S = UH.IH = UC.ICV cng sut chtao cua cun hach bng Smu, nn ta cou kin:S Smu = Kcl.SmDong in trong cun halaIH; trong cun chung vacun ni tip la:Ich=Int=IC=S/UC

Cng sut tai cua cun chung :Sch=Uch.Ich =UT.S/UC = (1-Kcl) S

UcUT

C

T

O

IT

IC

ICh

Int

S

O

UcUT

CIC

Int= IChIH

SH

T

(UC- UT)


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Cng sut tai cua cun ni tip:Snt=Unt.Int =(UC- UT).S/UC = Kcl.STrong trng hp gii han S=Smu; th:Sch=(1-Kcl)Smu SmuVaSnt = Kcl.Smu Smu;

Ngha lacahai cun ni tip vacun chung u non tai; vado ocothcho pheptruyn thm mt lng cng sut nao ona tTA sang CA nh sexet phn sau.b. Truyn cng sut tHA sang CA, pha TA khng tai:

Giathit boqua tn tht :S = UH.IH = UT.ITV cng sut chtao cua cun hach bng Smu, nn ta cou kin:S Smu = Kcl.Sm

Dong in trong cun halaIH; trong cun chung la:Ich = IT= S/UTCng sut tai cua cun chung :Sch=Uch.Ich =STrong trng hp gii han S=Smu; th cun havacun chung tai ung bng cng sutnh mc cua no: SH=SHm=Smu; Sch= Schm =Smu

Mc ducun cao ap khng tai nhng khng thtruyn thm mt lng cng sutnao na tCA sang TA, v khi oselam quatai cun chung.3. Chlin hp

a. Chtruyn cng sut CATA (tngu)va HATA (bi n ap)

O

UT

C

ICh

IH

SH

T IT=Ich

O

UT

C

IH(BA)

SH

TIT(TN)

SC

IC(TN)Int(TN)

Ich(TN)

IT(BA)IT(BA)

IT


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tnh cng sut tai cua cac cun dy may bin ap tngu chlin hp nayta dung phng phap xp chng hai chsau:- Chtngu: truyn tbn CA sang cho phutai pha TA lng cng sut SC.- Chbin ap: truyn tbn HA sang cho phutai pha TA lng cng sut SH.

Nu khng xet n khanng quatai cho phep cua MBA th SCSm vaSHSmu.Thnh ve trn, thy rng trong cun dy chung hai dong in hai ch t

ngu vabin ap cung chiu nhau, nn cun chung db quatai nht. V vy cnkim trakhanng tai cua cun nay.

Theo kt quatnh toan hai chTN vaBA trn, ta ddang thy c:- chtngu:Cng sut cun dy ni tip: Snt(TN)=Kcl.SCCng sut cun dy chung Sch(TN) = Kcl.SC- chbin ap:

Cng sut cun dy ni tip: Snt(BA)= 0Cng sut cun dy chung Sch(TN) = SH- Tng hp hai ch(lin hp):Cng sut cun dy ni tip: Snt = Kcl. SC SmuCng sut cun dy chung: Sch= Sch(BA)+Sch(TN) = SH+Kcl. SCiu kin kim tra khanng tai cua cun chung:Sch = SH+Kcl. SC SmuHay cothtnh theo cng sut tac dung P vacng sut phan khang Q:

SmauQKclQPKclPSch 2CH2CH +++= ).().( Thy rng nu atruyn cng sut cng sut mu tHA sang TA th khng th

truyn thm mt lng cng sut nao na tCA sang TA; vanu a truyn cng sutnh mc Sm tCA sang TA th khng thtruyn thm mt lng cng sut nao na tHA sang TA.

b. Chtruyn cng sut TACA (tngu)va HA

CA (bi n ap)

- Chtngu: truyn tbn TA sang cho phutai pha CA lng cng sut ST.- Chbin ap: truyn tbn HA sang cho phutai pha CA lng cng sut SH.

O

UT

C

IH(BA)

SH

T

IC(TN)

STIT(TN)

Int(TN)

Ich(TN)

IC(BA)

Int(BA)= Ich(BA)

IC


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Nu khng xet n khanng quatai cho phep cua MBA th STSm vaSHSmu.Thnh ve trn, thy rng trong cun dy chung hai dong in hai ch t

ngu vabin ap ngc chiu nhau nn khng b quatai; con trong cun dy ni tip haidong in hai chcung chiu nhau, nn db quatai nht. V vy cnkim tra khanng tai cua cun ni tip.

Theo kt quatnh toan hai chTN vaBA trn, ta ddang thy c:- chtngu:Cng sut cun dy ni tip: Snt(TN)=Kcl.STCng sut cun dy chung Sch(TN) = Kcl.ST- chbin ap:Cng sut cun dy ni tip: Snt(BA)= Kcl.SHCng sut cun dy chung Sch(TN) = (1-Kcl).SH- Tng hp hai ch(lin hp) ta tnh c cng sut tai cua cun dy ni tip:

Snt = Kcl. SH + Kcl. SCiu kin kim tra khanng tai cua cun ni tip:

Sch = Kcl (SH + SC) SmuHay cothtnh theo cng sut tac dung P vacng sut phan khang Q:

SmauQQPPKSch 2

TH2

THcl +++= )()(.

Thy rng nu atruyn cng sut cng sut nh mc tTA sang CA th khngthtruyn thm mt lng cng sut nao na tHA sang CA; tuy nhin nu atruyncng sut mu Sm tHA sang CA th con cothtruyn thm mt lng cng sut na

tTA sang CA.i vi may bin ap tngu ba pha cac kt quatrn vn ung.

4.3.3. u nhc im-c im vapham vi sdung MBATN1. u im:- V cac cun dy vamach tmay bin ap tngu u c tnh toan chtao theo

cng sut mu ch bng Kcl.Sm ( nhohn Sm) cho nn tiu hao vt liu, kch thc,trong lng vagia thanh senhohn so vi may bin ap ba pha ba dy qun cocungcng sut nh mc. Chnh nhvy secho phep chtao c cac may bin ap tngu co

cng sut n v ln.- Tn tht cng sut trong MBA tngu noi chung nhohn so vi MBA 3 dy qun

nht lakhi lam vic vi chhaap (Tcao ap sang trung ap ) , con chtng apth u im nay ch phat huy tac dung khi cng sut truyn ttrung ap sang cao ap . Contn tht khng tai vatn tht in ap cung behn bin ap thng .

- in khang gia cun cao vacun trung trong MBA tngu behn so vi MBAthng nn iu chnh in ap trong MBA tngu ddang hn.2. Nhc im

- MBA tngu coquan hvin gia cun cao vacun trung nn song quain ap(kh quyn, ni b) cothtruyn tbn mang cao ap sang mang trung ap nn lam cho


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cach in trong nhng iu kin nay xu i vado ocac u ra cua MBA tngu vphiacao vatrung ap thng t chng set van khng kem dao cach ly.

- Ch dung MBA tngu trong trng hp mang in ap cao vatrung cotrung tnhtrc tip ni t, v nu dung MBATN trong mang cao ap vatrung ap cotrung tnh cachin th khi cham t mt pha pha cao ap th in ap pha cua hai pha khng cham ttrong mang in ap cao setng ln bng in ap dy, nhng in ap hai pha khng hhong pha in ap trung tng ln rt ln . V dui vi mang 110/35KV, khi cham tmt pha pha 110KV th bn trung ap 35KV in ap hai pha khng cham t setng lnkhoang 3,8 ln .

- Do in khang gia cun cao va cun trung be nn dong in ngn mach trongmang cao vatrung ap seln hn nhiu so vi trng hp dung MBA ba dy qun.

- V MBA t ngu lun lun lam vic vi mang trung tnh ni t nn dong inngn mach rt ln . Nu dung MBA tngu lam nhim vutng ap thaap sang trung

ap vacao ap th khng coli v luc nay phai chon cng sut nh mc MBA tngu :S

mTN SH / Kcl

valuc nay tn tht cng sut cothkhng nhohn so vi MBA 3 dy qun.4.4. Khanng tai cua may bin ap4.4.1 t vn

Ta abit cng sut nh mc cua may bin ap lacng sut biu kin tnh bngKVA mamay bin ap cothmang tai lu dai trong iu kin nh mc cua in ap, tns, nhit mi trng cung nh iu kin lam mat; khi otui thosebng nh mc.

Nhng trong thc tmay bin ap thng lam vic khac chnh mc. Phutaicua may bin ap lun lun thay i theo thi gian , co luc nhohn co luc lai ln hncng sut nh mc Sm, ngha lacokhi non tai cokhi quatai. Cahai chvn hanhnay u khng kinh t. Thc tcho thy rng may bin ap cothmang tai quanh mctrong mt thi gian nao ocua ngay hoc cua nm matui thocua may bin ap khnggiam, nu trong phn thi gian con lai cua ngay hoc nm omay bin ap lam vic nontai so vi nh mc. May bin ap cho phep lam vic chnay hay chkhac khngphai c quyt nh bi cng sut nh mc maphai cn cchuyu vao huy hoai

cach in, nhit cc ai cua cun dy vacua du trong giai oan c xet.

4.4.2. Khanng tai cua may bin apKhanng tai cua may bin ap latp hp cac chmang tai bnh thng vaqua

tai cua may bin ap. Kha nng tai cua MBA khng th biu din bng n v KVAc, v noc xac nh bng mt loat cac iu kin nh: th phutai, thi gian tntai chvn hanh, nhit mi trng lam mat..

V vy mun xac nh mt ch lam vic nao ocuamay bin ap mt nhit

mi trng nao oth cn phai xac nh c nhit cun dy, nhit du vamchuy hoai cach in.


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4.4.3. giaci cach inTrong may bin ap ng lc, ngi ta dung chuyu cach in cp A, nhit cho

phep cua cach in nay ln n 105OC.Trong vn hanh, khi nhit tng th phan ng hoa hoc tng, lam cho cach in

b x cng, bn c vabn in cua vt liu cach in cung giam vata goi cachin b giaci. Sgiaci c c trng bng giaci cach in vacothbiu dinphuthuc vao nhit .

Theo nh lut Arenius, khi nhit bin thin trong khoang t80OC n 140OCth tui tho trung bnh cua vt liu cach in cp A phu thucvao nhit theo biuthc sau:

= . aeAV trong oA, a lacac hng sphuthuc vao vt liu cach inlanhit im nong nht cua cun dy MBA (0C)

Ngi ta axac nh c i vi cach in cp A:A=(1,57,5).104nm; a = 0,115 (1/0C)

ch nh mc, nhit im nong nht cua cun dy bng nh mc vabng 98OC th tui thosebng nh mc:

dma

dm eAV = .

Tui thotng i cua cach in sela:

)(*

ma

m

e

V

VV ==

ai lng nghch ao L=1/V* c goi lagiaci cua c

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