tai lieu ve qlvh luoi dien va tba

5/28/2018 Tai Lieu Ve QLVH Luoi Dien Va TBA

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Dng cho ngh QLVH ng dy v trm - tp 1

giangdt - Hi p qlvh in 1

Cu hi 1: Gii thch ti sao b iu chnh in p ca my bin p li t phacun dy s cp m khng t pha cun dy th cp?Tr li :My bin p thng c mt cun dy s cp v c mt hoc hai cun dy th

cp. Khi t in p U1 vo cun dy s cp th trong cun dy ny s c dngin I1 chy qua v trn cun dy th cp xut hin in p U2. Khi c ph ti uvo cun dy th cp th trong cun dy th cp s c dng in I2 chy qua. ln ca dng in s cp v th cp tng gim theo ph ti. Quan h gia s vngdy s cp W1 v s vng dy th cp W2 vi dng in I, in p U ca my binp tun theo quy lut sau:

W - vngW1 U1~ I2~ I - Ampe

= = U - VonW2 U2~ I1~

S vng dy t l thun vi in p v t l nghch vi dng in.Do bn knh cung cp in ln trn ng dy c nhiu ph ti v cng sut tiu

th in ca cc ph ti trong mt ngy thng dao ng gy ra s dao ng inp cui ngun. My bin p lc thng c b iu chnh in p t pha cundy s cp :

+ Trc tip iu chnh s vng dy ca cun dy s cp cho ph hp in p ungun, gi c in p pha u ra ca my bin p t nh mc.

+ Hn ch c qu in p my bin p.+ Gim c tn tht in nng cho li in.

V dng in i qua cun dy s cp nh nn dng in i qua tip im ca bCA cng nh do cc kch thc ca tip im b CA cng gim i dch to, h c gi thnh. V b iu chnh in p c ch to theo kiu phnnc nn ch c kh nng iu chnh in p u ra ca my bin p gn bng nhmc.

Cc my bin p 3 pha thng dng khng c yu cu n nh in p nnthng hay dng b iu chnh in p 3 pha kiu n gin c t 3 n 5 u

phn nc, khng cho php iu chnh in p khi my bin p vn hnh mang ti.Mi khi thay i u phn nc iu chnh in p phi ct in ton b my bin

p, sau phi o in tr tip xc ri mi c php ng in. Tt c cc my bin p c yu cu n nh in p u phi lp b iu chnhin p di ti. B CA c cu to c bit cho php iu chnh c in pca my bin p ngay c khi my bin p ang mang ti. B iu chnh in pdi ti 3 pha thng c ch to 19 nc.

Cu hi 2: My bin in p lm nhim v g trong trm bin p? S ging nhauv khc nhau gia my bin p lc v my bin in p? S ging nhau v khcnhau gia my bin in p v my bin dng in?

Tr li :My bin in p l my bin p chuyn dng bin i in p c 3 nhim v:1- Cung cp in p 100V~ cho ng h Vonmt o in p pha cao th.


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2- Cung cp in p 100V~ cho cc cun dy in p ca cng t in 3pha.

3- Cung cp in p th t khng (3U0) cho r le bo chm t khi c chmt pha cao th.

My bin in p c mt s im ging my bin p lc: My bin in p v my bin p lc c ch to da trn nguyn l cm

ng in t.Nng lng in c truyn dn t cun dy s cp sang cun dyth cp thng qua qu trnh cm ng t.

My bin in p v my bin p lc c cu to c bn ging nhau, mybin in p v my bin p lc u c cun dy v li thp.

My bin in p c mt s im khc my bin p lc: Cng sut ca my bin in p thng nh cha n 1kw, dung lng S

ca my bin in p c tnh bng VA (S 250VA). Cng sut ca my bin p lc ln, dung lng S ca my bin p tnh bng

kVA (S 50kVA) My bin in p thng c kch thc hnh hc nh hn my bin p lc

rt nhiu. My bin in p c kch thc mch t v kch thc ca cc cun dy

nh. Theo chng loi v vi tng cp in p khc nhau my bin in p t thayi v cu to, kiu cch, hnh dng v kch thc.

Tu theo tng loi my bin p lc, cun dy s cp v th cp c nhiu cpin p khc nhau, trong khi my bin in p ch c duy nht mt cp in pth cp l 100 V~.

My bin p lc 3 pha c rt nhiu t u dy khc nhau, trong khi mybin in p 3 pha thng c t u dy Y0/Y0/ h.

My bin in p ging my bin dng in: My bin in p v my bin dng in cng c ch to da trn nguyn

l cm ng in t. Nng lng in c truyn dn t cun dy s cp sangcun dy th cp thng qua qu trnh cm ng in trng v t trng.

My bin in p khc my bin dng in:

V nhim v cng tc:+ My bin in p chuyn lm nhim v bin i U.+ My bin dng in chuyn lm nhim v bin i I.

V cch u dy trong li in:+ My bin in p u song song trong mch in.+ My bin dng u ni tip trong mch in.


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Cu hi 3: My bin dng in lm nhim v g trong h thng in? Ti saotrong vn hnh khng c php h mch cun dy th cp my bin dngin?Tr li :Trong h thng in my bin dng ( TI ) lm nhim v bin i dng in t tr

s ln thnh tr s nh, tr s dng in th cp nh mc ( I2m) ca my bindng c quy chun l 5A hoc 1A.Cng dng:

Dng cp in cho mch dng in ca ampe mt, watt mt, cng tin. Cc thit b o m ni trn mun u vo TI phi c ch to theo quy

chun dng in nh mc l 5A hoc 1A cho ph hp vi dng in nh mcpha th cp ca my bin dng.

Th d: Nu dng in i qua cun dy s cp ca TI l 500A, dng in nh mc

ca cun dy th cp ca TI l 5A th TI c t s bin i l:kI= 500A/5A = 100

Nu dng in i qua cun dy s cp ca TI l 500A dng in nh mcca cun dy th cp ca TI l 1A th TI c t s bin i l:kI= 500A/1A = 500

Trong cc trm bin p 110kV mi TI c ch to 2 cun dy th cp, 1 cundng cho o lng v 1 cun dng cho r le bo v. Trong cc trm bin p phnphi h th 220/380V thng dng 2 b TI, mt b dng ring cho ng h am pemt b dng ring cho cng t in. Khng cho php cc thit b o trong trmbin p dng chung 1 b TI m bo cho cng t in lm vic c chnh xc.

Trong vn hnh nu h mch th cp my bin dng s gy ra chy hng vhai nguyn nhn: Nguyn nhn 1: Gy t ha li thp lm nng mch t dn n cch in

MBD chng b gi ci.

U1~ U1m~

I1m~

I2m~ = 5A( hoc 1A )

S u dyMy bin p lc

S u dyMy bin in p

S u dyMy bin dng in

U2~


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Bnh thng trong cun dy s cp v th cp ca TI u c dng in chy quai1~ sinh ra lc t ha F1 = i1 w1i2 ~ sinh ra lc t ha F2 = i2 w2

Ta c F = F1 - F2 = i1w1 - i2w2 0Khi h mch th cp i2~ = 0

F2 = i2w2 = 0F = F1 - F2 = F1F = i1w1.

F1 gy t ha li thp TI dn n TI thng xuyn b nung nng dn n cchin ca cun dy TI b ha gi rt nhanh.

Nguyn nhn 2: Lm xut hin in p nh nhn E2 trong cun dy, chcthng cch in ca TI.

Khi vn hnh c ti cun dy s cp v th cp ca TI u c dng in chyqua: Dng in ph ti I1~ s c c tuyn hnh sin, dng in I1~ sinh ra t thng1~c dng hnh sin, t thng ny cm ng trong cun dy th cp mt dng inI2~ cng c dng hnh sin .

Khi cun dy th cp ca TI b h mch trong li thp xut hin t thng1~ tns 50Hz. ng c tuyn c dng hnh thang. Ti im i chiu (im 0) tc bin i ca t thng d/dt l ln nht s sinh ra sc in ng e2 c dng nhnhn trn cun dy th cp ca TI (xem hnh v c tuyn ca TI).

Trong biu thc (1) d1/dt l tc bin i ca t thng. k l h s t l.

e2 (kV) l sc in ng.

e2 = k (1)

Cu hi 4: C bao nhiu dng s c c bn trong h thng? V s v giithch?Tr li :

d1

dt


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C 5 dng s c c bn trong h thng in 3 pha1. Ngn mch 3 pha: ( thng km theo chm t )

ABC I "KE

I K 3 E

2. Ngn mch 2 pha: khng chm t

ABC I K2

3. Ngn mch 2 pha: chm t

ABC I K2

I K2E

4. Ngn mch 1 pha: chm tABC

I K1E

5. Ngn mch chm tti hai im khc nhau trn mt ng dy:

ABC

I K2E

Nhng nguyn nhn gy ra s c ngn mch trong h thng in:1- Nguyn nhn khch quan:


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Do st nh vo h thng in vi cng ln, in p cao, cc thit bchng st lm vic khng hiu qu.

2- Nguyn nhn ch quan :Hu ht cc s c ch quan u do con ngi gy ra:

- Do trnh k thut non yu.- Do x dng cc thit b c, lm vic km hiu qu.- Do khng thc hin ng quy trnh vn hnh v duy tu bo dng thit b.- Do mang ti khng ng quy nh cho php.- Do ph hoi (o phi ng cp, nm cht chy vo thit b lm ngn

mch...)Cc gii php k thut ngn chn v hn ch sut s c:

Mt h thng in coi l c tnh an ton, cht lng tt l h thng inc sut s c thp nht, thi gian s c nh nht. m bo c yucu ni trn h thng in cn phi c:

- H s d phng cao (thit b c cp cch in v dng in cho php cao

hn nh mc nhiu ln)- C phng thc vn hnh hp l.- Khng xy ra qu ti h thng in, qu ti my bin p.- Cn phi c nhiu ngun in d phng.

Cu hi 5: S khc nhau gia my ct in v cu dao,cu ch? Gia ptmt v cu dao cu ch? Nu trnh t thao tc thit b ?Tr li :Trong trm bin p v li in thng x dng my

ct in, cu dao, cu ch, p t mt: My ct in:

+ Chu c dng in ngn mch ti 25kA vi my ct SF6.+ Chu c dng in ngn mch 300kA vi my ct chn khng.

+ S ln ng ct trong ch s c t ti 50 n 100 ln, 20.000 ln trong ch mang ti+ My ct in cho php ng ct ch mang ti v ch ngn mch.+ Thi gian ct ca my ct c th t ti 45mmgiy.+ My ct in mun lm vic c phi c thm b TI v h thng r le bo v.

+ Thng c dng in p cao t 3kV tr ln.+ Dng in nh mc thng thng l 630A,

1250A, 2500A, 3000A.+ Thao tc my ct bng in v c kh. T ng

hoc bn ta .

Hnh nhMy ct t ng ng li


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Cu dao cao th+ Nhim v chnh l cch ly ngun in

vi ph ti phc v cho cng tc vn hnh,duy tu bo dng thit b in.

+ Cu dao cao th thng c ch to theo

in p li in v cp dng in 100A,200A, 400A, 600A, 800A, 1000A, 1250A,2500A.

+ Cu dao cao th thng c ng ctthng qua b truyn ng c kh m bokhong cch an ton cho ngi vn hnh.

+ Dng in nh mc ca cu dao bao gicng phi ln hn dng in ph ti i quady dn.

+ Khng cho php thao tc cu dao trong ch c ti.

+ Cu dao ph ti l loi cu dao c trang bthm b dp h quang v l so ct, cho phpthao tc trong ch mang ti. Tuy nhincu dao ph ti khng th lm vic c nhmy ct v n khng c trang b h thngbo v r le.

Thit b chng st

Cu dao

Auto reclosers( my ct t ng

ng lp li)

Tt c c thaybng mt c cung ngt: Cudao phn on

c iu khin

CU DAO PHN ON C IU KHIN

Hnh nhCu dao ph ti trung th

Hnh nhCu dao ph ti 12,24,36kV


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Cu ch cao th

THNG S K THUT CA CU CH T RI

TT Thng s k thut n v 24kV 35kV

1 in p nh mc kV 22 352 in p ln nht kV 24 38,53 iu kin mi trng lm vic Nhit i ho4 iu kin lp t Ngoi tri5 Nhit mi trng lm vic oC 5- 456 Tn s nh mc Hz 50

7in p chu ng tn s ngun n t v v gia cc cc

t ( 10 sec) kVrms 50 60 Kh ( 1 pht ) kVrms 60 70

8 in p chu ng xung st 2.2/50s (BIL)

n t v gia cc cc

kV (peak) 125 170

9 Dng in nh mc A 10010 Dng in ngn mch nh mc ( 1s) kA 12 1011 Dng ng, ct MBA khng ti A 2,512 Dng ng, ct ng dy khng ti A 1013 Chiu di ng r mm/kV 25

14 Tiu chun ch toIEC 265,282ASNIC 37,41ANSIC37,42

c lp ni tip sau cu dao cao th. y l thit b bo v n gin trong mch

in m yu cu bo v khng cao lm, Cu ch ch yu dng bo v ngn mch. Thng dng li trung p 35kV tr

xung. Cu ch t ri thng dng li in trung

p. cp in p110kV khng dng cu ch.

Cu ch ui xoy Cu ch np s Cu ch thch anh

HNH NH CU CH H TH

Cu ch t ri 12, 24, 36kVc dng in r khc nhau


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Trong trm 110kV cu ch thng dng bo v cho cc my bin in p cpin p 6kV, 10kV, 22kV, 35kV.ptmt

Vi cng sut ph ti ln thng dng loi ptmt c iu khin c tnh nnggn ging nh my ct in cao th, ngi ta cn gi loi ptmt ny l my ct

in h th. BNG THNG S K THUT CA PTMT

TT Hng mc nv

yu cu

1 kiu 3 pha 3cc

2 in p nh mc V 6003 Tn s h thng Hz 50

4 in p chu ng tn s ngun trong 1 pht kV 2,55 in p xung nh mc( 1.2/50ms ) kV 8

6

Kh nng chu ng dng ngn mch Icuti in p 380/400V

kA 25

Im = 100A kA 25 Im = 150A kA 35 Im = 250A kA 35 Im = 400A kA 35 Im = 500A kA 35

Im = 630A kA 35 Im = 800A kA 50

7 Kh nng chu ng dng ngn mch Ics = 50% Icu8 S ln thao tc Ln 15.0009 c tnh bo v: c tnh C: theo tiu chun IEC947- 210 Gii chnh nh

10-1p t mt 250A

Bo v qu dng (Overload protection ) (0,8-1) ImBo v ngn mch ( Short circuit protection ) (5- 10) Im

10-2p t mt 250A

Bo v qu dng (Overload protection ) (0,4-1) ImBo v ngn mch ( Short circuit protection ) (2- 10) Im

ptmt thng c dng in p thp t1000V tr xung.

Dng in nh mc ca ptmt thng thngt 15A n 3000A, chu c dng in ngnmch ti 12kA.

Cho php ng ct trong ch mang ti v ngnmch.

Thng thng bn trong ptmt khng cn phil thm TI.

Hnh nh p t mt


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Hnh nhCu dao h th kiu v nha

Cu dao h th thng i lin vi cu ch. Dng in nh mc ca cu dao v cu

ch phi c la chn ph hp vi dng in nh mc ca ph ti v dng incho php i qua dy dnIcd IcfIcc = 2,5Itt

Icf l dng in cho php i qua dy dn.Itt l dng in tnh ton ca ph ti.

Cc cu dao c cht lng tt thng c thm li dao ph. Li dao ph s ct rasau khi li dao chnh ct, tc ct ca li dao ph rt nhanh nh c trang b

thm l so ct. Li dao ph lm nhim v bo v li dao chnh khng b chytrong qu trnh thao tc.

Trnh t thao tc: bo m cho cc thit b in lm vic bnh thng cnphi thc hin cc thao tc theo trnh t nh sau: Khi ng in phi ng cu dao trc, ng my ct hoc ng p t mt sau. Khi ct in phi ct my ct hoc p t mt trc, ct cu dao sau.

BNG THNG S K THUT CU DAO H TH KIU HP ST

Cu dao h th in p nh mc

Um 400V. Dng in nh mc

Im 3000A.

Nhim v chnh ca cu dao h th l cch ly ngun in vi ph ti, phcv cho cng tc vn hnh v duy tu bodng thit b in. Trong mch in tnht pha ngun in cu dao phi b trtrc ptmt. Cho php thao tc cu daoc ti trong phm vi dng in nh mcca cu dao.

Hnh nhcu dao an ton kiu hp st


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Kiu S cc

in p phc v ti a nhmc (V)

Kh nng chuin p cch

in/pht (kV)

Pha-pha

Pha-v

Dng in nh mc 40oC(A)

Phn t bo v: Cu chy ng Cng dng in qu ti

(A)

Cch in gia pha vi pha v

pha vi v

Kch thc ngoi (khi tay y v tr ng) v khi lng.

Kch thc ngoi

Khi lng (kg)

KCH THC HNH HC CU DAO H TH KIU HP ST


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BNG TNH SN DNG IN NH MC CA DY CHY CU CH


Kch thcngoi

CDH3PIN100A150A200A

CDH3PIN250A300A400A500A

CDH630A800A

1000A

CDH3P2N100A150A200A

CDH3P2N250A400A

CDH3P2N630A800A1000A

CDH3P2N1600A2000A

CDH3P2N2500A3000A

A 330 440 530 305 630 650 764 869M 260 332 430 258 500 527 618 720Q 190 235 350 190 330 330 500 500B 460 615 880 460 413 665 810 860N 408 564 710 408 600 600 750 850P 350 460 630 350 500 500 650 750

C 230 - - 230 320 365 531 552D 171 220 260 187 237 237 336 352 8.5 10.5 12.5 8.5 10.5 12.5 16.5 16.5

Khi lng (kg)

999

19191920

43.646

46.8

999

32.534

41.242.846

73.696

110120


Kch thc ngoi

CDH4CIN100A150A200A

CDH4CIN250A300A400A500A

CDH4CIN630A

CDH4C2N100A150A200A

CDH4C2N250A300A400A500A

CDH4C2N1600A2000A

CDH4C2N2500A3000A

A 365 740 630 365 740 776 1090M 318 610 535 318 610 652 900Q 250 440 445 250 440 455 500

B 460 413 880 460 413 665 860N 408 600 710 408 600 600 900P 350 500 630 350 500 500 750C 230 320 - 230 320 365 552D 205 237 - 205 237 237 352 8.5 10.5 12.5 8.5 10.5 12.5 12.5

Khi lng (kg)

1212

12

4046

4848

54 1212

12

4046

4848

5457

6161.5

150160


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BNG TNH SN DNG IN NH MC CA DY CHY CU CHCHO MY BIN P PHN PHI H TH

TTcngsut

MBA(kVA)

6kV 10kV 15kV 24kV 35kVdnginnhmc(A)

chngloidydn

dnginnhmc(A)

chngloidydn

dnginnhmc(A)

chngloidydn

dnginnhmc(A)

chngloidydn

dnginnhmc(A)

chngloidydn

1 30 2,89 6k 1,73 3k 1,16 2k 0,79 2k 0,5 1k2 50 4,82 8k 2,98 6k 1,93 3k 1,31 2k 0,83 2k3 75 7,23 12k 4,34 6k 2,89 6k 1,97 3k 1,24 2k4 100 9,63 15k 5,78 8k 3,85 6k 2,63 6k 1,65 3k5 160 15,41 25K 9,25 12K 6,17 10K 4,20 6K 2,64 6K6 200 19,27 25K 11,56 15K 7,71 10K 5,25 8K 3,3 6K7 250 24,08 30K 14,45 20K 9,63 15K 6,57 10K 4,13 6K8 320 30,83 40K 18,50 25K 12,33 20K 8,41 12K 5,28 8K9 400 38,54 50K 23,12 30K 15,41 25K 10,51 15K 6,61 10K

10 560 53,95 80K 32,37 50K 21,58 30K 14,71 25K 9,25 15K11 630 60,69 100K 36,42 65K 24,28 40K 16,55 30K 10,4 20K12 1000 96,34 57,80 80K 38,54 65K 26,27 40K 16,52 25K13 1600 154,14 92,49 61,66 100K 42,04 65K 26,42 40K14 2500 240,85 144,51 96,34 65,69 100K 41,29 65K

15 3200 308,29 184,79 123,31 84,08 52,85 80K16 4000 385,36 231,21 154,14 105,10 61,06 100K

Vt liungknh dychy (mm)

Dng in nh mc

Ch ng Nhm

0,2 0,5 8 20.3 1,2 12 60,4 1,5 14 100,5 1,8 16 140,6 2,6 21 180,7 3,2 28 180,8 4,3 36 201,0 6,0 48 321,2 9,0 69 401,4 11,5 81 50

1,6 14 100 601,8 17 120 702,0 20 145 802,2 25 175 972,4 30 - 1152,6 35 - 125


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Cu hi 6: TI hnh xuyn treo c cp lm vic nh th no? Ti sao dy tipa c cp li phi lun trong lng TI hnh xuyn?

Tr li :Ti cc trm bin p 110kV thng dng loi cp XLPE lm cp xut tuyn

trung th, cp ny thng c bao bc bn ngoi 1 lp ai thp (Fe) bo v vc hc, ngoi cng ca cp li c bc mt lp nha dy bng PVC bo vcho ai thp khi b r. Di u cp c lp mt my bin dng hnh xuyn ctn l my bin dng th t khng, ai thp ti c cp c hn mt dy tip a.

TI hnh xuyn treo c cp lm vic nh sau: Bnh thng khi khng c chm ts khng c dng in i qua ai thp, khic s c chm t 1 pha dng in chm t s xut hin v i qua ai thp xungt. Nu im ni t ca c cp nm pha trc my b in dng dy ni tkhng lun qua my bin dng th dng in chm t khng i qua my bin

dng, my bin dng s khng c tc dng trong mch bo v r le bo v chmt. Trong li in trung im cch in, khi xy ra chm t dng in th tkhng (3I0) i qua im chm t rt nh.

+ Dng in chm t c chiu i t thanh ci ra ng dy v i qua imni t nm sau my bin dng.

+ Vi cc ng dy cng u chung mt thanh ci th dng in 3I0 xut hintrn cc l ng dy s cng c chiu i t ng dy vo thanh ci sau lngqua cun dy my bin p chnh ri i v pha ng dy ang c chm t 1 pha

v chui xung t. Dng in chm t c gi tr bng tng dng in th t khngtrn thanh ci 3I0. Mun cho bo v chm t lm vic c th dy tip a ti c cp bt bucphi c lun pha bn trong ca my bin dng tp trung c hon tondng in chm t Th t khng 3I0 i qua.

Cu hi 7: Trong trm bin p phn phi h th cng t in t pha trc vsau my bin p c g khc nhau?

Dy tip a ti c cplun qua my bin dng.


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Tr li :Trong trm bin p cng t in c t pha trc hoc pha sau my bin th

u lm nhim v o m in nng. C mt s im khc nhau: Cng t in t pha cao thl cng t o m in nng pha trc mybin th, lm vic c cng t s phi u qua my bin in p v my bindng in cao th.

+ Treo cng t in pha cao th s o m c ton b in nng tiu thca trm bin p.

+ Trong trm bin p 110kV pha cao p v pha trung p u lp TU v TI nncng t in thng c t pha 110kV v tt c cc l ra pha trung p,bng cch ny ngi ta s o c in tiu th ca trm bin p v cc l ra.

+ Treo cng t pha cao th phi lp thm my bin in p v my bin dngin cao th nn c gi thnh xy dng tng. Cng t in t pha h thl cng t o m in nng pha sau my binp.

+ Trm bin p phn phi c dung lng nh nn cng t in t pha h th.+ V MBD lp sau my bin p lc nn s khng o m c tn tht in

nng trong ni b my bin p v tn tht in nng trn cc on ng dy tmy bin p n cng t.

+ Vi nhng trm bin p phn phi h p ngi ta thng ch t TI h th gim gi thnh xy dng.

+ Khi t cng t in pha h th, ngi ta thng phi a thm vo h squy i tnh ton gi thnh tiu th in. Cch lm ny s gy ra sai lch ktqu o m.

S u dy cng t in S u dy Cng t int pha cao th c TU v TI t pha h th 380/220V ch c TI

Cu hi 8: V sao TI cao th thng u 2 pha A, C m khng u pha B?Nu u TI pha A, B hoc pha C, B c c khng? Ti sao cun dy th cpmy bin in p thng c ni t pha b m khng ni t pha a hoc phac?


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Tr li:Trong trm bin p, mch cng t o m cao th ta hay gp trng hp TI lp

pha A,C m khng lp pha B. y l quy c chung trong vic u dy hthng cng t.

Khng u TI pha A, B hoc C,B v:Cng t o m in nng t pha cao th thng hay dng loi cng t 3 pha

2 phn t, cun dy in p ca cng t c cp in t my bin in p bngin p dy

Uab = Ucb = 100V~.My bin in p 3 pha c ni t pha B nn trong s u dy vi cng t

in loi 3 pha 2 phn t bt buc phi u pha a, c. ph hp th t pha trongs u dy cng t TI phi lp pha A, C.

TU ni t pha b, khng c ni t cc pha a hoc c v:Theo s u dy khi my bin dng t pha A v C, hai cun dy in p

ca cng t in phi u vo in p dy Uab v Ucb.

+ Nu ni t pha c th hai cun dy in p ca cng t in li u voin p dy Uac v Ubc ca TU. (Hnh 2)

+ Nu ni t pha a th hai cun dy in p ca cng t in li u voin p dy Uca v Uba ca TU. (Hnh 3)

Mun cng t lm vic ng ta phi cho ni t cun th cp pha b ca TU.

Cu hi 9: Cng t in v cng v cng t in hu cng c g khc nhau? Tisao cc cc u dy ca hai loi cng t ny li ging nhau?Tr li :

Cng t v cng dng m in nng v cng, cng t hu cng dng m in nng hu cng, quy nh v s u dy ca cun dy dng in vcun dy in p ca hai loi cng t nh sau (Hnh 1, hnh 2):

1- Cng t Hu cng:Vi li in cao th Vi li in h th

dng in Ia i vi in p Uab - dng in Ia i vi in p Uao dng in Ib i vi in p Ubc - dng in Ib i vi in p Ubo dng in Ic i vi in p Uca - dng in Ic i vi in p Uco

2- Cng t V cng:

Hnh 1 Hnh 2 Hnh 3


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Vi li in cao thv h th dng in Ia i vi in p Ubc dng in Ib i vi in p Uca dng in Ic i vi in p Uab

Cch u dy bn trong cng t v cng hoc hu cng c tun theo quynh v cc tnh v th t pha ca cun dy dng in v in p trn s . tin cho vic u dy cc cc u dy trn hng boc v cch u dy bn ngoica hai loi cng t ny c lm ging nhau. Mun nhn bit 2 loi cng tni trn ta cn phi xem k hiu kWh, kVArh mt ngoi cng t.

Hnh 1: Cng t hu cng v v cng 380/220V 5Aloi 3 pha 3 phn t

Hnh 2: Cng t hu cng v v cng cao th 100V~/ 5Aloi 3 pha 2 phn t

Hnh nh Cng t in


18/157



Hin nay ti cc im o m ranh gii trn li in hoc ti cc trm binp ph bin dng loi cng t 3 pha 3 phn t (Hnh 3).

Cu hi 10: Trnh by cu to v nguyn l lm vic ca my bin p lc? Ti saoni my bin p lc va l ngun in trung gian li va l ph ti ca li in?

Tr li :

E2 = i2 (Z0 + Z2) = i2Z0 x i2Z2 = U0 + U2- U0 l in p ging trn ni b cun dy W2- U2 l in p ging trn ph ti mch ngoi Z2

Mi my bin p lc u c mt dung lng ti hn lm nhim v cung cpin trc tip cho ph ti, n ng vai tr mt ngun in trung gian phn phinng lng in ca ngun in. Trong vn hnh mi my bin p lc tiu th

Hnh 3: S u dy cng t hu cng v v cngcao th 100V/ 5A loi 3 pha 3 phn t

Cu to: Xem hnh nhNguyn l lm vic :

My bin p c ch to theo nguynl cm ng in t. Khi c in p xoaychiu t vo cun s cp W1 , trongcun dy s cp s c 1 dng in i1chy qua, dng in i1 cm ng trong lithp 1 t thng 1. T thng 1 mcvng qua cun dy th cp W2 sinh ra

trong cun dy th cp 1 sc in ngcm qua. Do cun dy th cp ca mybin p c tr khng nn ti cun dyth cp xut hin 1 in p ging U0 lcn sc in n :

Hnh nh my bin p phn phi


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mt lng cng sut khng ti P0 v cng sut ngn mch PN nn trong h thngin my bin p ng vai tr ph ti.

Hnh v m tHnh dng bn ngoi MBA

THNG S K THUT CA MY BIN P DO VIT NAM SN XUT

- 1 l t thng.- U1 l in p s cp- U2 l in p th cp- w1 l cun dy s cp- W2 l cun dy th cp

Cu to my bin p1. Thng du ph

2. ng ch th mc du3. ng ni thng du chnh v thng

du ph4. Thng du chnh5. S MBA6. Cnh tn nhit7. Li thp MBA8. Cun dy s cp v cun dy th

cp

9. Du my bin p (trong thng du)

7

8

U1~

U2~

W1

W2


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Cu hi 11: Nhng kim loi no thng dng ch to dy dn in? So snhc tnh k thut ca tng loi? Ti sao ngi ta khng dng dy nhm li thptrong li in h th 0.4kV?Tr li:

Vt liu thng dng ch to dy dn in l ng, nhm, thp...

BNG SO SNH C TNH K THUT

Tnvtliu

in trsut Kh nng chu ko c tnh k thut

ng(Cu) = 0,017241

mm2/m

=38 39kg/mm2 ng thanh=26 28kg/mm2 ng mm

- dn nhit tt- dn in tt- chng n mn

cao

Nhm(Al)

= 0,0295mm2/m= 16 17 kg/mm2 nhm thanh= 8 kg/mm2 nhm mm

- dn nhit tt- dn in tt- kh nng chng

n mn kmhn ng

Thp(C)

= 0,1mm2/mloi nguyn cht = 0,13mm2/mloi c nhiu cacbon

=120 150 kg/mm2- dn in km- dn nhit bnh

thng- b n mn mnh

Khi in p cao trn 1000V v tn s cao trn 1000Hz s xut hin hiu ngb mt. Trong thc t li in cng nghip thng c tn s 50Hz, li in


22/157



thng tin truyn thanh thng dng in p thp nhng li c tn s cao hng kHz(1kHz = 1000Hz) hoc hng MHz (1MHz = 1000kHz). Dng in i qua dy dns phn b ra pha mt ngoi ca dy dn, li thp ng vai tr tng cng lc cgii ng dy v vy li in cao p tn s cng nghip 50Hz cho php dngdy nhm li thp lm dy dn in. Khng dng dy nhm li thp lm dydn in trong li in h th 0,4kVv vi in p thp < 1000V tn s cngnghip 50Hz( 60Hz) s c hiu ng b mt rt nh nn li thp ca dy nhm lithp

Dy nhm li thp (ACSR)Aluminium conductor steel reinforcedTCVN 5064 : 1994 & TCVN 5064:

ard - Drawn aluminium strandedonductorCVN 5064 : 1994 & TCVN 5064:1/95

Titdin danh

nhNominalArea

Kt cuStructure

Titdin tnh

tonCalculated

Area

ng

knh tngOverall

Diameter

Trnglng

gn ngApprox.Weight

in trDC 200C

DCResistance

at 200C

Lc kot nh

nht

Minimumbreaking

load

Chiu

di snxut

Lengthmm N /mm mm mm kg/km /km N m16 7/1.70 15.88 5.10 43 1.8007 3.021 2.00025 7/2.13 24.93 6.39 68 1.1489 4.500 2.00035 7/2.51 34.62 7.53 94 0.8347 5.913 2.00050 7/3.00 49.46 9.00 135 0.5748 8.198 2.00070 7/3.55 69.25 10.65 189 0.4131 11.288 2.00095 7/4.10 92.37 12.30 252 0.3114 14.784 2.000120 19/2.80 116.93 14.00 321 0.2459 19.890 2.000

150 19/3.15 147.99 15.75 406 0.1944 24.420 1.500185 19/3.50 182.71 17.50 502 0.1574 29.832 1.500240 19/4.00 238.64 20.00 655 0.1205 38.192 1.500300 37/3.15 288.2 22.05 794 0.1000 47.569 1.500400 37/3.66 389.08 25.62 1072 0.0740 63.420 1.500

Dy nhm li thp (ACSR)

Dy nhm trn xon (A)


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BNG TRA CU CP TRN

Tit dindanh nh

NominalArea

Kt cu Structure Titdin tnhton

CalculatedArea

ngknh tng

OverallDiameter

Trng lng gnng Approx. Weight in tr DC

200C DC

Resistanceat 200C

Lc kot tithiuMinimum

breakingload

Chiudi sn

xutLength

Phn

nhmAluminium

Phn

thpSteel NhmAluminium ThpSteel TngTotal

mm2 N0/mm N0/mm mm2 mm kg/km kg/km kg/km /km N m

35/6.2 6/2.80 1/2.80 36.9/6.15 8.40 100 48 148 0.7774 13.524 2.000

50/8.0 6/3.20 1/3.20 48.2/8.04 9.60 132 63 195 0.5951 17.112 2.000

70/11 6/3.80 1/3.80 68.0/11.3 11.40 188 88 276 0.4218 24.130 2.000

70/72 18/2.20 19/2.20 68.4/72.2 15.40 188 567 755 0.4194 96.826 1.200

95/16 6/4.50 1/4.50 95.4/15.9 13.50 261 124 385 0.3007 33.369 1.20095/141 24/2.20 37/2.20 91.2/141 19.80 251 1106 1357 0.3146 180.775 1.000

120/19 26/2.40 7/1.85 118.0/18.8 15.15 324 147 471 0.2440 41.521 1.200

120/27 30/2.20 7/2.20 114.0/26.6 15.40 320 208 528 0.2531 49.465 1.200

150/19 24/2.80 7/1.85 148.0/18.8 16.75 407 147 554 0.2046 46.307 1.200

150/24 26/2.70 7/2.10 149.0/24.2 17.10 409 190 599 0.2039 52.279 1.200

150/34 30/2.50 7/2.50 147.0/34.3 17.50 406 269 675 0.2061 62.643 1.200

185/24 24/3.15 7/2.10 187.0/24.2 18.90 515 190 705 0.1540 58.075 1.200

185/29 26/2.98 7/2.30 181.0/29.0 18.82 500 228 728 0.1591 62.055 1.000

185/43 30/2.80 7/2.80 185.0/43.1 19.60 509 337 846 0.1559 77.767 1.000

185/128 54/2.10 37/2.10 187.0/128.0 23.10 517 1008 1525 0.1543 183.816 1.000240/32 24/3.60 7/2.40 244.0/31.7 21.60 673 248 921 0.1182 75.050 1.200

240/39 26/3.40 7/2.65 236.0/38.6 21.55 650 302 952 0.1222 80.895 1.200

240/56 30/3.20 7/3.20 241.0/56.3 22.40 665 441 1106 0.1197 98.253 1.200

300/39 24/4.00 7/2.65 310.0/38.6 23.95 830 302 1132 0.0958 90.574 1.200

300/48 26/3.80 7/2.95 295.0/47.8 24.05 812 374 1186 0.0978 100.623 1.200

300/66 30/3.50 19/2.10 288.5/65.3 24.50 796 517 1313 0.1000 117.520 1.200

300/67 30/3.50 7/3.50 288.5/67.3 24.50 796 527 1323 0.1000 126.270 1.200

300/204 54/2.65 37/2.65 298.0/204.0 29.15 823 1603 2426 0.0968 284.579 1.200

330/30 48/2.98 7/2.30 335.0/29.1 24.78 924 228 1152 0.0861 88.848 1.200

330/43 54/2.80 7/2.80 332.0/43.1 25.20 918 337 1255 0.0869 103.784 1.200

400/18 42/3.40 7/1.85 381.0/18.8 25.95 1052 147 1199 0.0758 85.600 1.200

400/22 76/2.57 7/2.00 394.0/22.0 26.56 1089 172 1261 0.0733 95.115 1.200

400/51 54/3.05 7/3.05 394.0/51.1 27.45 1090 400 1490 0.0733 120.481 1.200

400/64 26/4.37 7/3.40 390.0/63.5 27.68 1074 498 1572 0.0741 129.183 1.200


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Dy ng trn xon (C)

Hard - Drawn copper stranded conductorTCVN 5064 : 1994 & TCVN 5064: S1/95

Tit din danhnhNominal Area

Cu trcStructure

Tit dintnh tonCalculatedArea

ngknh tngOverallDiameter

Trnglnggn ngApprox.Weight

in trDC 200CDCResistanceat 200C

Lc kot nhnhtMinimumbreakingload

Chiudi snxutLength

mm N /mm mm mm kg/km /km N m16 7/1.70 15.88 5.10 142 1.1573 6.031 2.00025 7/2.13 24.93 6.39 224 0.7336 9.463 2.00035 7/2.51 34.62 7.53 311 0.5238 13.141 2.00050 7/3.00 49.46 9.00 444 0.3688 17.455 2.00070 19/2.13 67.67 10.65 612 0.2723 27.115 1.50095 19/2.51 93.97 12.55 850 0.1944 37.637 1.200

120 19/2.80 116.93 14.00 1058 0.156 46.845 1.000150 19/3.15 147.99 15.75 1338 0.1238 55.151 800185 37/2.51 182.99 17.57 1659 0.1001 73.303 700240 37/2.84 234.27 19.88 2124 0.0789 93.837 600300 37/3.15 288.20 22.05 2614 0.0637 107.422 500400 37/3.66 389.08 25.62 3528 0.0471 144.988 350

Si dy nhm trn k thut in


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Si dy nhm trn k thut inElectrotechnical round aluminium wireTCVN 5934 - 1995

ngknh siDiameter

Sai schophp

Tolerance

Mt ct

SectionalArea

Su t ko t t ithiu MinimumTensile Strength

dn di t ithiu MinimumElongation Trng

lnggnng

Approx.Weight

in trDC 200CDC

Resistanceat 200C

Sicng

HardWire

Si nacngSemi-

HardWire

Sicng

HardWire

Si nacngSemi-

HardWiremm mm mm kg/mm kg/mm % % kg/km /km1.4 0.02 1.539 17.0 9 14 1.0 2 4.154 18.3891.6 0.02 2.010 17.0 9 14 1.3 2 5.426 14.0731.8 0.02 2.543 17.0 9 14 1.3 2 6.867 11.1202.0 0.02 3.140 17.0 9 14 1.3 2 8.478 9.0082.3 0.02 4.153 17.0 9 14 1.3 2 11.212 6.8122.6 0.03 5.307 16.5 9 14 1.5 2 14.328 5.3312.9 0.03 6.602 16.5 9 14 1.5 2 17.825 4.2853.0 0.03 7.065 16.5 9 14 1.5 2 19.076 4.011

3.2 0.03 8.038 16.5 9 14 1.5 2 21.704 3.5203.5 0.04 9.616 16.5 9 14 1.5 2 25.964 2.942

3.7 0.04 10.747 16.5 9 14 1.5 2 29.016 2.6333.8 0.04 11.335 16.5 9 14 1.5 2 30.606 2.4974.0 0.04 12.560 16.0 9 14 2.0 3 33.912 2.2524.2 0.04 13.847 16.0 9 14 2.0 3 37.388 2.0454.5 0.05 15.896 16.0 9 14 2.0 3 42.920 1.780


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Si dy ng trn k thut

Si dy ng trn k thut inElectrotechnical round copper wireTCVN 5934 - 1995

ngknh siDiameter

Sai s chophpTolerance

Mt ctSectionalArea ight

in tr DC 200CDC Resistance at 200C

Sut ko t ti thiuMinimum TensileStrength

dn di ti thiuMinimum Elongation

Si cngHard Wire

Si m mSoft Wire

Si cngHard Wire

Si m mSoft Wire

Si cngHard Wire

Si m m SoftWire

mm mm mm kg/km /km /km kg/mm kg/mm % %0.40 0.01 0.1256 1.118 142.91 138.22 40 20 28 0.6 20

0.45 0.01 0.1590 1.415 112.92 109.21 40 20 28 0.6 20

0.50 0.01 0.1963 1.747 91.46 87.81 40 20 28 0.6 20

0.55 0.01 0.2375 2.113 75.59 72.57 40 20 28 0.6 20

0.60 0.01 0.2826 2.515 63.52 60.98 40 20 28 0.6 25

0.65 0.01 0.3317 2.952 54.12 51.96 40 20 28 0.6 25

0.70 0.015 0.3847 3.423 46.67 44.8 40 20 28 0.6 25

0.80 0.015 0.5024 4.471 35.73 34.3 40 20 28 0.6 250.90 0.015 0.6359 5.659 28.23 27.10 40 20 28 0.6 25

1.0 0.02 0.7850 6.987 22.87 21.95 40 20 28 1.6 301.2 0.02 1.130 10.061 15.88 15.24 40 20 28 1.6 30

1.4 0.02 1.539 13.694 11.67 11.20 40 20 28 1.6 301.6 0.02 2.010 17.885 8.932 8.575 40 20 28 1.6 30

1.8 0.02 2.543 22.636 7.057 6.775 40 20 28 1.6 302.0 0.02 3.140 27.946 5.656 5.488 40 20 28 1.6 30

2.3 0.02 4.153 36.959 4.277 4.150 40 20 28 1.6 30

2.6 0.02 5.307 47.229 3.347 3.247 40 20 28 1.6 30

2.9 0.02 6.602 58.756 2.690 2.610 40 20 28 1.6 30

3.2 0.03 8.038 71.542 2.209 2.144 38 20 27 1.5 30

3.5 0.03 9.616 85.585 1.847 1.792 38 20 27 1.5 30

3.7 0.03 10.747 95.645 1.653 1.603 38 20 27 1.5 30

4.0 0.04 12.56 111.784 1.414 1.372 38 20 27 1.5 304.3 0.04 14.515 129.180 1.224 1.187 38 20 27 1.5 30

4.5 0.04 15.896 141.477 1.117 1.084 38 20 27 1.5 305.0 0.04 19.625 174.663 0.905 0.878 38 20 27 1.5 30


27/157




28/157




29/157



Cu hi 12: H thng in gm my phn t? Nhim v ca cc phn t trong hthng in? Nu cc ch tiu nh gi cht lng h thng in?

Tr li :H thng in bao gm 3 phn t :

1- Ngun in: Nh my pht in, lm nhim v sn sinh ra nng lng

in2- Li in: Bao gm ng dy ti in v cc trm bin p.3- Ph ti: L cc thit b tiu th in nng.

C 2 ch tiu quan trng nh gi cht lng h thng in:1- Tn s (f ) : Lun n nh tn s 50Hz.2- in p (U ): Lun m bo ch in p nh mc U = U m.

Mt h thng in c cht lng tt phi lun m bo c hai ch tiu trn.

Cu hi 13: Du bin th lm nhim v g trong my bin p? Nu cc tiu

chun quan trng nht ca du my trong vn hnh? Phng php qun l du mybin p trong vn hnh?Tr li :Du bin p lm 2 nhim v :

1- Cch in cho my bin p .2- Lm mt cho my bin p theo nguyn tc i lu tun hon.

C 3 ch tiu quan trng nht ca du my bin p trong vn hnh:1- in p chc thng [kV]

Th nghim in p chc thng ca du bng cc th du, khong cch phng

in gia 2 cc mang in p cao trong mi trng cha y du l 2,5cm.- Cp in p di 15kV:+ 30kV vi du mi trong MBA cha qua vn hnh.+ 25kV vi du trong MBA ang vn hnh.

- Cp in p di 15kV n 35kV:+ 35kV vi du mi trong MBA cha qua vn hnh.+ 30kV vi du trong MBA ang vn hnh.

- Cp in p di 110kV:+ 45kV vi du mi trong MBA cha qua vn hnh.+ 40kV vi du trong MBA ang vn hnh.

- Cp in p 110kV n 220kV:+ 60kV vi du mi trong MBA cha qua vn hnh.+ 55kV vi du trong MBA ang vn hnh.


30/157



- Cp in p 500kV:+ 70kV vi du mi trong MBA cha qua vn hnh.+ 65kV vi du trong MBA ang vn hnh.2- Nhit chp chy kn: Khng thp hn 1350 C, suy gim khng qu

5% so vi ln phn tch trc.3- Tr s axt: khng qu 0,25mg KOH trong 1g du.

Qun l du trong vn hnh :- Bnh thng mi nm phi th nghim nh k mu du 1 ln.- MBA lm vic trong tnh trng y ti hoc qu ti thng xuyn th phi rt

ngn thi gian th nghim nh k.- Khi s c chy my bin p thng l km theo du b chy, cht lng du

MBA suy gim, phi thay du.- Khi i tu MBA phi thay du.- Khi mc du trong my bin p gim thp, phi b xung du theo hng dn

ca nh ch to.

- Du b xung vo my phi c cng gc du hoc c gc du tng ng.- Phi kim nh li du trc khi vo my theo cc tiu chun k thut

ca ngnh in.

Cu hi 14: Nu cc thng s k thut ghi trn bin nhn ca mt my bin plc phn phi h th? Gii thch ngha ca cc thng s ?

Tr li:Cc thng s k thut trn bin nhn ca mt my bin p lc phn phi h th l:

1. Sm [kVA]: Dung lng nh mc ca my bin p.

2. Um1, Um2 [kV]: in p nh mc ca cun dy pha s cp v th cp camy bin p.3. Im1, Im2 [A]: Dng in nh mc ca cun dy pha s cp v th cp ca

my bin p .4. UN% (cn gi l UK%): in p ngn mch tnh theo phn trm, cho ta bit

tn tht in p trong cun dy my bin p khi my bin p mang ti.UN

UN% = 100Um

5. I0% : Dng in khng ti ca my bin p tnh theo phn trm dng innh mc ca my bin p.I0

I0% = 100Im

6. P0 [kW]: Tn tht khng ti l mt tr s khng i vi mi my bin p, nkhng ph thuc vo tnh trng vn hnh mang ti ca my bin p.

7. f [Hz]: Tn s ca ngun in.8. Trng lng ton b ca my bin p [kG]9. Trng lng ca du my bin p [kG]

Cu hi 15: Trc khi a mt my bin p lc vo vn hnh phi lm nhng thnghim g, nu cc hng mc cn th nghim v gii thch?


31/157



Tr li :Cc hng mc cn th nghim my bin p trc khi a vo vn hnh bao gm:

1- o R cch in bng m gm mt 2500 V- Gia cc cun dy cao v cun dy h.- Gia cc cun dy cao v cun dy cao.- Gia cun dy cao v v.- Gia cun dy h v cun dy h.

2- o in tr 1 chiu ca cc cun dy.3- o t s bin my bin p.4- o in p ngn mch UN%5- o dng in khng ti I0.6- Th nghim du my bin p.

y l nhng hng mc th nghim quan trng cn phi lm trc khi ng inmy bin p.

Cu hi 16: vng v khong cch ti t l g? Biu din bng hnh v? vng v khong cch ti t ph thuc vo cc yu t g?Tr li:

+ vng f ca dy dn l khong cch thng ng t im thp nht cady dn n ng thng cng dy trn 2 u s.

+ Khong cch ti t h ca dy dn l khong cch gn nht tnh t dy dnn mt t.

T cng thc tnh vng :g.l Trong : - g l t ti ca dy dn

f = - l l khong ct.8. - l ng sut ko ca dy dnTa suy ra :

+ f cng ln khi g v khong ct l cng ln, ng sut ko ca dy dn cngnh, v ngc li f cng nh khi g v khong ct cng nh, ng sut koca dy dn cng ln.

+ Qua hnh v ta thy: Khong cch ti t h ca dy ph thuc vo f v cao ca im treo dy.


32/157



Cu hi 17: Biu din lc tc dng ln u ct ti cc v tr ct xut tuyn, ctcui, ct no gc, ct no trung gian, ct chuyn hng, ct trung gian?Tr li :

Cu hi 18: Tn tht in p l g?Nu cc gii php lm gim tn tht in p?

Tr li:Tn tht in p l lng in p b mt i trn ng dy trong qu trnh chuynti, tn tht in p gy ra st in p trn ng dy ti in.

U = U1U2Tn tht in p l mt ch tiu quan trng ca li in:

U

S1 S 2 S 3 S 4 S 5

1- Ct no u cui, 2- ct gc,3- ci no trung gian, 4- Ct chuyn hng, 5- Ct trung gianF1, F2: lc cng dy. Fc: lc ct. FN: Lc no ct. F: Lc tng hp


33/157



U% = 5%U1

Nu tn tht in p ln s lm cho cc thit b dng in khng hot ng c,gim nng sut ca hiu sut thit b dng in, gy ra tn tht in nng trnng dy ti in.

Cc gii php lm gim tn tht in p :1- Phi lm gim in tr R v in khng X ca ng dy bng cch :

+ C bn knh cung cp in hp l.+ Chn dy dn c in tr sut nh, c tnh dn in tt.+ Tng cng tit din dy dn, c h s d phng cao.+ Hn ch ti a cc mi ni, cc mi ni phi c R tip xc nh nht

2 - P hi la chn cp in p li in ph hp vi cng sut chuyn ti v bnknh cung cp in, iu chnh in p u ngun lun t in p nh mc.

3 - t thit b b cng sut v cng cho thit b in.

Cu hi 19: Hy gii thch ngha ca t u dy my bin p? Ti sao khi hasong song cc my bin p bt buc phi c cng chung mt t u dy?Tr li :

Cc cun dy ca my bin p 3 pha thng c mt trong ba cch u dy sau:+ Y (sao)+ (tam gic)+ Z (zch zc) loi ny t dng.

Ty theo thit k cc cun dy s cp v th cp MBA thng c mt chiu qundy mt v mt kiu u dy nht nh. Khi vn hnh s xut hin gc lch pha

gia in p pha cao th v h th. Gc lch pha in p ph thuc vo cch udy ca cc cun dy v to ra t u dy nh: Y/-5 ,Y/ -11, Y/Yo - 6, Y/Yo -12. Quy c t tn t u dy nh sau:Dng kim ng h thi gian lm mu so snh. Quy c:

+ Nu trn mt ng h c 12 vch chia th khong chia ca mi vch l 30o.+ Quy c vc t in p s cp U1 tng ng vi kim di ca ng h v tr

12 gi.+ Quy c vc t in p th cp U2 tng ng vi kim ngn ca ng h, kim

ngn nm v tr tng ng vi gc lch pha ca in p th cp U2 vi inp s cp U1 l 300, 600... 3600.+ Mt vng trn c 3600. Nu ly 3600 chia cho 300 ta s c 12 vch, tn t u

dy ca my bin p s ly ln lt t 1 n 12.

Th d: T u dyY/Yo -12

Nu cun dy s cp v

th cp cng u sao ctrung im cun th cpni t (0) v c cngchiu qun dy, Khi vnhnh s xut hin gc lchpha ca in p pha scp v th cp l 3600, ly


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Nu cun dy s cp v th cp cng u sao, trung im cun dy th cp nit (0) nhng c chiu qun dy ngc nhau khi vn hnh s xut hin gc lchpha ca in p pha s cp v th cp l 1800, ly 1800 chia cho 300 c 6 ta ct u dy Y/Yo- 6.T u dy l mt tiu chun quan trng dng cho ha song song cc MBA

nu ho hai my bin p khc t u dy s xut hin s lch pha in p ti ucc my bin p dn n s c ngn mch.Trc khi ho song song 2 my bin p phi kim tra li t u dy thc t bng

cch o in p gia 2 u cc ca 2 my bin p.in p o c l:

Ua1- a2 = 0Ub1- b2 = 0Uc1- c2 = 0

MT S T U DY THNG DNG CA MY BIN P LC

Y/ Y0

T u dys cundy cao p

s cundy h p Biu vc t

Y/ Y6

/ 0

Nhm nidy khc

4; 8

10; 2

4; 8

T u dy Y/ Y0- 12


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Cu hi 20: Nu cc tiu chun ha song song hai my bin p? Gii thch v saomy bin p c cng dung lng, cng cp in p UK% li khng hon ton gingnhau?Tr li :Cc tiu chun ha song song hai my bin p l:

- phi c cng sut tng ng, khng chnh lch nhau qu 3 ln.- Phi c cng cp in p.- Phi c cng t s bin (KU1= KU1)- Phi c cng cc tnh (cn gi l th t pha)

- Phi c cng in p ngn mch tnh theo phn trm UK% hoc UN%- Phi c cng t u dy.- cp in p 380/220V cn thm yu cu: Dy trung tnh 2 MBA ni chung.

Tuy rng cc MBA c cng dung lng, cng cp in p nhng c th vt liuch to khng hon ton ging nhau, dy qun khng cng tit din, s vng dykhng bng nhau, cc bi dy qun cht hoc qun lng, khong cch cc vngdy khng u nhau.vv... s lm cho UK% khng hon ton ging nhau.

Cu hi 21: Phn bit :- in nng hu cng v in nng v cng- Cng sut hu cng v cng sut v cng- in nng tiu th v tn tht in nng

Tr li :

/ 6

Y/ 11

Y/ 5

10; 2

3; 7

9; 1


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in nng hu cng:L in nng c chuyn ha thnh

cng hu ch di dng c nng, nhitnng, ha nng tnh trong mt khongthi gian

AP = P . t [kWh]

in nng v cng:L in nng c chuyn ha thnh

cng v ch tn ti trong t trng vin trng (cun dy in t, t in...)tnh trong mt khong thi gian

AQ = Q . t [kVArh]Cng sut hu cng:

L cng sut tiu th c bin thnhcng sut tc dng di dng c nng,nhit nng, ha nng, quang nng...Cng sut hu cng c xc nh ti 1thi im.P = S.cos [kW]

Cng sut v cng:L cng sut tiu th in c chuyn

ha di dng in trng v t trng.Cng sut v cng c xc nh ti 1thi im.

Q = S.sin [kVAr]in nng tiu th:

in nng tiu th l lng in nngm ph ti tiu th tnh trong mtkhong thi gian.

A = Pt + jQt [kwh]

Tn tht in nng:Tn tht in nng l nng lng in

b mt mt trn h thng in trong qutrnh vn hnh tnh trong mt khongthi gian.

A =Pt [kwh]

Cu hi 22: Hy gii thch v sao li in phn phi 3 pha 4 dy cun th cpca my bin p bt buc phi u theo s hnh sao v c thm dy trung ha?Tr li:

Li in phn phi 3 pha 4 dy cun th cp ca MBT bt buc phi u theos hnh sao c thm dy trung tnh to ra c 2 cp in p 220V/ 380V in p 380V l in p dy Uab, Ubc, Uca, in p 220V l in p pha Uao, Ubo, Uco. Quan h gia in p dy v in p pha:

U dy = 3 U pha Trung im ca cun dy h th my bin p ni t c gi l ni t lm

vic. Khi vn hnh nu xy ra s c ngn mch 1 pha pha th cp my bin

p s gy ra dng in ngn mch ln cc thit b bo v nh cu ch,aptmt khi ng ct in bo m an ton cho li in. Trn dy trung tnh s c ni t mt s im c gi l ni t lp li to

nn mt ng dy trung tnh d phng i qua t, hn ch c nguy c quin p ni b khi b t dy trung tnh. V cc ph ti 1 pha dng in p220V thng c cng sut khng bng nhau, dy trung tnh ng vai tr to rain p pha. Nu xy ra t dy trung tnh ca ngun in th dy trung tnh schuyn thnh im ni dy trung gian ca cc ph ti 1 pha. Lc ny in ppha chuyn thnh in p dy, in p t vo ph ti 1 pha s phn b li theotr khng ca cc ph ti dn n tnh trng mt s ln ph ti 1 pha b quin p, ta gi l qu in p ni b gy ra chy hng cc thit b dng in.


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Cu hi 23: Gii thch v sao trc khi ng in my bin p phi th nghimkhng ti? Dng in khng ti c lin quan g n vic nh gi cht lng mybin p?

Tr li :Th nghim khng ti c thc hin bng cch ng in vo cun dy th cp

c in p thp ca my bin p v h mch cun dy s cp, sau o dng inkhng ti cun dy th cp my bin p.

Trc khi xut xng my bin p phi lm th nghim khng ti 3 pha xcnh dng in khng ti I0 v tn tht khng ti P0 ca my bin p.

Trc khi ng in vn hnh my bin p cng phi lm th nghim khng ti.Th nghim khng ti trc khi vn hnh ch yu l kim tra v pht hin xemcc cun dy ca my bin p c b chm chp khng. Trng hp th nghimkhng ti trong vn hnh ch cn lm ln lt vi tng pha v ch cn dng ngunin c in p khong 220V~, sau khi c kt qu o dng khng ti Io ta s tnhton quy i v tr s thc.

Mi mt my bin p s c mt dng khng ti khc nhau. Tr s dng inkhng ti Io thng t thay i theo thit k nn khi o c dng in khng ti tac th xc nh ngay c cng sut ca my bin p.

Cu hi 24: Nu nhng nguyn nhn gy ra tn tht in p v tn tht innng? Tn tht in p c lin quan g n tn tht in nng? Nu cc bin phplm gim tn tht in p v tn tht in nng? Ti sao khi vn hnh lch pha tntht in nng li tng ln?Tr li :

Nhng nguyn nhn gy ra tn tht in p v tn tht in nng :Tn tht in p v tn tht in nng sinh ra trong qu trnh truyn ti vtiu th in. Nguyn nhn l do :1- Trn ng dy dn in c in tr R v in khng X.2- Do cc my bin p c tn tht cng sut trong cun dy v tn tht khng

ti trong li thp3- Do tiu th nhiu cng sut v cng trn li in, ch yu do cc ph ti c

thnh phn in cm nh cun dy my bin p, cun dy ng c in,cun cm c li thp... lm gim cos ca li in.

4- Do ch vn hnh ca li in :+ Tn tht cng ln khi cng sut tiu th in ca ph ti cng ln.+ Tn tht cng ln khi thi gian s dng cng sut cc i cng ko di

(thi gian s dng cng sut cc i k hiu l TMax).+ Do my bin p thng xuyn vn hnh trong tnh trng non ti hoc

khng ti.+ Do tnh trng lch ti cc pha, tnh trng ny thng xy ra trong li

in phn phi h th.Tn tht in p lin quan trc tip n tn tht in nng v :

Khi li in khng ti ch tn ti in p khng c dng in i qua ths khng c tn tht in p v tn tht in nngU=0, A=0.


38/157



Khi li in c ti, trong dy dn s c dng in I chy qua. Do dy dn cin tr R v in khng X nn trn dy dn xut hin tn tht in pU 0

Tn tht in p:

xx x

Tn tht in nng c tnh bng:

gi thit nu ph ti ca mng in khng thay i ta c

Trong : Imax l dng in cc i. R l in tr ca ng dy. l thi gian tn tht cng sut ln nht, l thi gian m mng in lin

tc chuyn ch cng sut ln nht Pmax (hay Imax) s gy ra mt tn thtin nng trong mng in ng bng tn tht in nng thc t ca mngin sau 1 nm vn hnh.

R rng tn tht in nng v tn tht in p c lin quan trc tip n nhau,chng u ph thuc vo in tr ng dy (R) v tnh trng mang ti ca mngin.

Cc bin php lm gim tn tht in p v tn tht in nng :1. Nng cao h s cng sut cos cc h dng in ch yu l cc x nghip

c th l la chn cng sut ca ng c hoc loi ng c cho ph hp, nng caoh s ph ti kB...hn ch lm vic khng ti.

cosl h s cng sutc tnh bng:

P P l cng sut tc dngcos =

S S l cng sut biu kin

Phn phi cng sut tc dng v cng sut phn khng trong mng in theomt phng thc hp l nht. Gim cng sut phn khng chuyn ti trong mngin. B v cng bng my b ng b hoc bng t in tnh.

2. My bin p vn hnh theo phng thc tn tht in nng t nht, vn hnhkinh t trm bin p bng cch ha ng b my bin p.

3. Nng cao mc in p vn hnh ca mng in.

A=P.t

A = 3I2max R

U% =P.R + Q.X

Um1001000


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4. Nng cao cp in p nh mc ca mng in.5. La chn s ni dy hp l nht cho mng in

Th d: Nn dng mng in kn thay cho mng in h. Bn knh cung cp in ph hp theo tiu chun cho php. Kim tra thng xuyn tnh trng tn tht in p, tn tht in nng v thchin cn o pha thng xuyn trong li in phn phi h th 220/380V,trong li in 110kV c 200km li c 1 ln hon thnh hon v pha gimin khng ca ng dy.

Trong li in h th 220/380V nu vn hnh lch pha th tn tht in p,tn tht in nng tng ln v: Khi vn hnh lch pha trn dy trung tnh xuthin mt dng in khng cn bng Io chy qua v bng tng hnh hc dngin trong cc pha.

I0 = IA + IB + IC(k hiu mi tn biu din i lng vct)

Dng in ny gy ra trong dy trung tnh mt tn tht in p:

U0 = IAro + IBro + ICro (Cng vct)ro l in tr ca dy trung tnh.

Dng in i trong dy pha gy ra tn tht in p trong cc dy pha l:

UPA = IAr UPB = IBr UPC = ICr (Cng vct)Trong r l in tr ca dy pha.

Tn tht in p ton phn ca 1 pha s bao gm c tn tht in p trongdy pha v trong dy trung tnh :

LUA = ( + ) - ( PB + PC )

Um F F0 2 .Fo . Um

PBL 1 1 LUB = ( + ) - ( PA + PC )

Um F F0 2 .Fo. Um

PCL 1 1 LUC = ( + ) - ( PA + PB )

Um F F0 2 .Fo. Um

Trong - P [ kW] Pm Cng sut tc dng.- U [ kV]: Um in p nh mc.- [m/. mm2] l in dn sut ( ca ng l 53, ca nhm l

48)

PAL1 1


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- Fo, F [ mm2 ] Fo, F l Tit din ca dy dn trung tnh v dy pha.

Nh vy khi vn hnh lch pha tn tht in nng trn ng dy s tng ln vngoi tn tht in p trn dy pha cn c thm tn tht in p trn dy trungtnh.

Cu hi 25: T b c vai tr g trong vic gim tn tht in nng trn li in?Tr li:

T b c vai tr tch cc trong vic gim tn tht in nng trn li inTrong thc t ph ti in l cc ng c in khng ng b c cos rt thp,

ngoi ra cc ph ti khc nh cc my bin th phn xng, cc l in kiu cmng, my bin th hn, qut in, n tup, cc loi n hunh qung co cng tiuth kh nhiu cng sut phn khng v cng c cos thp. ng nhin khing dy chuyn ti thm mt lng cng sut phn khng Q ln s lm hn chnhiu n kh nng dn in ca dy dn, lm cho dy dn b pht nng v lmcho tn tht in nng tng ln.Th d: Mng in c ph ti l P- jQ th tn tht cng sut trong mng l:

P1 = R v Q1 = XU2 U2

P- jQ l cch biu din di dng phcP l cng sut tc dng. kWQ l cng sut phn khng. kVArX l in khng ng dy.

R l in tr ng dy. U l in p ca im t t b. V(kV).

Nu ta t t b ngay ti h dng in, t b s a vo li mt dng inmang tnh cht in dung IC v pht ra 1 cng sut phn khng gi l Qb. Cngsut phn khng cn chuyn ti trn ng dy s gim xung cn l Q - Qb

P2 = R v Q2 = X

U2 U2Nh vy t b c tc dng hn ch cng sut v cng pht sinh trn li in cithin c cos v gim c tn tht in nng.

Cu hi 26: S khc nhau v u nhc im trong vic t t b pha cao th vpha h th?Tr li :

t t b pha cao thC li ch:

+ Gi thnh u t tnh theo kVAr/ng r hn pha h th v khi b pha caoth thng t dng thit b iu chnh dung lng b.

P2 + Q2 P2 + Q2

P2 + (Q - Qb)2 P2 + (Q - Qb)

2


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+ B c c dung lng Qpt ca ph ti pha h th v dung lng Qo trongni b MBT

Khng c li ch:+ T in cao th thng lp cp in p trung p nn yu cu lp t s phc

tp hn, chim nhiu din tch v khng gian hn.+ Do dung lng t khng cao lm nn ch dng cc thit b ng ct v bo v

n gin nh cu dao cu ch, trm bin p 110kV u cp cp n nhm tthng t 1 my ct khng t thit b iu chnh dung lng b v gi thnh ut s cao ln rt nhiu. Trong li in ch c cc trm pht b c dung lng lnngi ta mi a vo h thng iu chnh dung lng b, trong trng hp nyngi ta dng nhiu my ct in v cc t hp b r le iu khin t ng.

t t b pha h thC li ch :+ Qun l vn hnh v sa cha n gin v in p thp s d lp t, chim

t din tch v khng gian.

+ Thng c t cc thit b ng ct, iu khin v bo v. D dng iuchnh c dung lng b theo ch cng sut, in p, cos.

Khng c li ch:+ Gi thnh u t tnh theo kVAr/ ng t hn pha cao th mt t v c thm

cc thit b iu chnh dung lng b.+ Ch b c trong phm vi cng sut ph ti h th ca mt my bin p.

Cu hi 27: Cch tnh ton dung lng t b. Khi dng in tr phng in bngbng n nn u theo s hnh sao hay tam gic?

Tr li :Dung lng t b c xc nh theo cng thc:

Qb = P( tg1 - tg2) .Qb = P.tg. .

Trong : P l ph ti tnh ton ca cc h tiu th in kw, 1 l gc ng vi h s cng sut cng sut trung bnh cos1 trc khi b 2 l gc ng vi h s cng sut cng sut trung bnh cos2 sau khi b .

Thng cos2 ly bng 0,8- 0,95. h s iu chnh dung lng b thc t khi c thm gii php nng cao

cos khng cn lp thit b b.C th dng bng tnh sn (1-1) kt hp vi cng thc (1):

khi bit cos1 v cos2 tra bng (1-1) bng cch ging 2 tr s cos1 v cos2 vmt to ta c tr s tg = ( tg1 - tg2)

Dung lng t b Qb = P.tg.Tc dng ca in tr phng in trong mch in t b:in tr phng in trong mch in t b c tc dng trit tiu in p d trn tngay sau khi ct in t b. Nu trn t cn lu in tch d s nguy him chongi vn hnh nu nh v tnh chm vo in cc ca t in.Quy nh:

(1)


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Sau 30 pht in p d ch c php tn ti trn cc t in di 65V in tr phng in khng c php tiu hao cng sut tc dng qa

1W/1kVAr tnh theo dung lng t. tin cho vic theo di qu trnh phng in ca t ngi ta dng bng n lm

R phng in. Thng dng bng n c cng sut 40W/230V hoc 60W/230V ni tr ca

1 bng n l:U2 220 x 220

R= = = 1210

P 40

U2 220 x 220R= = = 807

P 60 Do in p ngun in l 220V nn hay u cc bng n theo s hnh Y.Cch u ny tin cho thi cng nhng khng c li cho vn hnh v nu c 1 nhm

bng n ca mt pha b chy th s c mt nhm t khng c dp in tch d. u bng n theo s tam gic dng in p dy tt hn v nu xy ra trnghp mt nhm bng n b chy in tch d trn cc pha t vn c trit tiu qua2 nhm bng n cn li. V in p ca ngun l 380V m bng n chu in pnh mc 220V nn mt vai ca s u tam gic phi dng ti thiu l 2 bngn. Cc t in h th thng lp sn in tr dp in tch d bn trong.

Cu hi 28- V sao t b 3 pha thng u theo s tam gic, ch b cho liin bng t in 3 pha m khng b 1 pha? Nu nguyn nhn gy ra tn thtin nng do t b trong vn hnh?Tr li:

V cu to: Cc t in cao th thng c ch to 1 pha, c in p dy Ud do khi u vo li phi u t theo s tam gic. Cc t in h th thngc ch to kiu 3 pha c u sn theo s tam gic chu in p dy. V mt vn hnh: nu u t theo s tam gic c li hn, so vi cch u ttheo s Y cng tr s in dung C [Fara] nh nhau th dung lng ca t tng

c ln gp 3, .Q = Ud

2 C = ( 3 Uf)2 C = 3 QY

T in

in tr phng in

S u dytrong ni b t in


43/157



V cc ph ti 1 pha thng nm trong li in phn phi tiu ph cng sut vcng nh nn khng b cho 1 pha. Trong qu trnh vn hnh t in no cng sinh s ra 1 t nhit lng lm nngnh v t in. Nu cht in mi ca t b km cht lng t s rt nng gy ratn hao in nng ln. T thng c u song song thm in tr phng in, t b cao th thng

c in tr phng in bng 2M. Khi ct in t, in tch d s phng inqua cc in tr song song . y l nguyn nhn gy ra tn tht in nng cat in. Vi dung lng 100 kVA th sut tn tht ln nht do t b gy ra l 0,1W/kVAr.

Cch gim tn hao ca t: Cn phi la chn dung lng t hp l. Chn im t t b ti ni c Q ln,

cos thp. La chn tr s in tr phng in ph

hp vi dung lng b nm trong phmvi quy nh: 1W / 1kVAR.

Nu qu b Qb > Q rt d gy nn qu inp ph hng t. chng hin tng qu b

trong vn hnh cn phi thng xuyn iuchnh dung lng t bng cch phn chia tb thnh cc nhm nh v t thit b t ngiu chnh dung lng b.

k 1 k2 k 3

AB - 500V

380/220V t hanh c i t in h t h

c o s pl c

K1 K2 K3

b iu k hin

kh i ng t

Hnh nhCc loi t b


44/157



Nguyn nhn gy ra tn tht in nng do t b trong vn hnh?

B bng t b cho trm bin p


45/157



hi 29: in

in

hoc

c i

=


46/157



hi 30: in in y bit php cun dy in

+ + + +

+ +


47/157



l

Ph l c t ham kho


48/157



hi 31: Trnh

- - a nhm

cun in.

Hnh nh

My bin dng trung p n 36kV

Hnh nh

My bin in p n 36kV

Hnh nhMy bin dng h p 0,4kV


49/157



.

+

M12 = C12 1 I cos ( 900 - )

M12 = C12 ( C1 I1 ) ( K 2 f I2 ) sin = C12 C1 K2 I1 I2 f sin


50/157



U

I2 =L

V

2

1

3

Hnh nhCng t in 1 pha

Hnh nhcng t in 3 pha


51/157



hi 32: Trnh ca

-

- -

-

S nguyn l S nguyn lcng t 3 pha 3 phn t cng t 3 pha 2 phn t

hi 33:

tnh theo cng t mu

-


52/157



1 2-

-

-

-

- + + +

-

-

+

+


53/157



Hnh nh

Cu hi 34: Trong h thng in c trung im khng ni t khi xy ra chmt 1 pha trn ng dy v chm t 1 pha trn thanh ci th bo v no tc ng?Hy trnh by nguyn l lm vic ca 2 loi bo v chm t trn?

Tr li :1- Trng hp chm t trn ng dy:

- Khi cch in 1 pha trn li in b hng th xy ra chm t. Trn ng dyxut hin dng in chm t (3I0). Dng in ny i t pha ng dy vthanh ci trm, lng qua my bin p chnh, v pha b chm t ri xung t.Dng in 3I0 ny ph thuc vo+ Tnh trng chm t (chm t qua in tr ni t ln hay b).+ Chiu di ng dy (km).+ Cp in p ca li in (kV).

Gi tr dng in chm t c th tnh tng i nh sau:

Ul3I0 = vi DK .

350

Ul3I0 = vi cp ngm.

10Trong : l l chiu di ng dy [ km ]

U l in p ca ngun in [ kV ]

H thng bo v r le chm t 1 pha bao gm:+ Mt my bin dng th t khng TI0 c dng hnh xuyn treo trn c cp xut

tuyn.+ Mt r le th t khng RT0 c u vo my bin dng th t khng TI0

Cng t in t kiu VISIONCng t in 3 pha 2 phn t trong

mch o m cao th cao th


54/157



+ Mt r le trung gian i tc ng my ct in ca l ng dy ang c chmt.

+ Mt r le in p bo chm t 3U0 u vo cun dy tam gic h ca TU.Bnh thng s khng c dng in 3I0 i qua r le. Khi xy ra chm t mt

ng dy no , lp tc trn my bin dng th t khng ca ng dy ang cchm t xut hin dng in 3I0, dng in ny c chiu i t pha thanh ci rang dy, r le khi ng i tc ng my ct. Cc ng dy khc c cngchung thanh ci vi ng dy ang b chm t s c dng in 3I0 i t phang dy v thanh ci. Cc dng in 3I0 ny cng i qua TI0 ca bn thn nnhng c chiu ngc vi chiu ca ng dy c chm t. cc bo v chmt ca nhiu ng dy khng cng khi ng mt lc, gy ra tc ng sai ngita dng phng php so snh gc lc pha ca in p U= 100V~ ly trn TU vdng in 3I0 ly trn cc TI0. in p v cc dng in ny cp cho cc r leRT0, khng nh c ch khi no c dng 3I0 i t pha thanh ci ra ng dymi cho php r le khi ng.

Do dng 3I0 nh, 3I0 1A nn r le khng khi ng c, cn phi tng 3I0 lnbng cch dng thm my bin p to trung tnh. My bin p to trung tnh dng to ra dng in 3I0L. Khi chm t dng in 3I0L mang tnh in cm xuthin trn cc cun dy my bin p to trung tnh cng lng qua my bin p chnhv i vo im chm t. Kt qu ta c dng in tng 3I0 c gi tr ln hn dngin 3I0C nhiu, dng in 3I0C mang tnh in dung. Dng in chm t tng3I0 c tnh nh sau:

3I0 = 3I0L + 3I0C cng vc t.

3I0 = 3I0L - 3I0C cng i s.

+ Vi li in 110kV o in p cao, tuyn dy c chiu di ln nn khi xy rachm t 1 pha th dng in chm t s qu ln cn phi gim i bng cch nit trung im my bin p 110kV,Khi chm t 1 pha 110kV, in p ca pha b chm t bng0. Dng in tng

ln bng dng in ngn mch 1 pha.Trong cun dy 110kV xut hin 1 dng in khng cn bng i qua im ni t

chung:

IA + IB + IC = IODng in IO i qua cun dy 110kV mang tnh in cm c k hiu l I0L.Dng in chm t tng I0 c tnh nh sau:

I0 = I0C + I0LI0 = I0C - I0L

Nh vy c th iu chnh c dng in chm t bng cch tng gim sim ni t ca cc trung im cun dy my bin p 110kV.


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2- Trng hp chm t trn thanh ci:Khi chm t mt pha trn thanh ci cng xut hin dng in chm t 3I0

khi ng bo v chm t th 3TI tng phi u dy theo s b lc th tkhng, 3 cun dy th cp ca 3 TI u theo s sao , t im chung ca 3cun dy th cp TI n im ni t ta u ni tip th m mt r le th t khng.

Trong s di RIa, RIb, RIc l 3 r le dng in dng cho bo v qu dng,R3I0 l r le bo v chm t.

S nguyn l bo v chm t 1 pha trn ng dy


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Cu hi 35: Vai tr ca t chnh lu v h thng c quy trong trm bin p110kV? Hy gii thch v sao trong trm bin p 110kV t chnh lu khng ththay th vai tr ca h thng c quy?

Tr li : T chnh lu & h thng c quy trong trm bin p 110kV lm nhim v cungcp in 1 chiu 220V/ DC cho:

+ H thng r le bo v.+ n tn hiu trn mng in trung tm.+ Thao tc my ct in.Dung lng ca c quy t 200 300A/h (ampe/gi). T chnh lu thng c

dung lng nh t 2 n 5kVA trong khi dng in thao tc ca 1 my ct cth cn n t 50A 95A nn t chnh lu khng c kh nng cung cp nnglng in cho thao tc my ct & bo v r le. in cho t chnh lu l ngun in xoay chiu 220V/380V ly my bin pt dng, khi xy ra s c ngn mch, in p ca my bin p t dng b gim tngt dn n in p 1 chiu ca t chnh lu cng gim theo gy nh hng trctip n cht lng in p 1 chiu ca h thng bo v r le dn n h thng bov r le s t chi tc ng.Chnh v vy:

"T chnh lu khng th lm vic thay th cho h thng c quy 220V trong trmbin p".

Cu hi 36: My bin th t dng lm nhim v g trong trm bin p? Ti saokhng cho php cc my bin p t dng cp in cho cc ph ti bn ngoi trmbin p?

S nguyn l h thng in mt chiu trong trm bin p 110kV


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Tr li :My bin th t dng chuyn lm nhim v cp in cho cc ph ti trong phm

vi mt trm bin p ln c cp in p 110kV, my bin p ny thng c cpin p 6,10,22,35kV/0,4kV Cc ph ti ca my bin p t dng l:

- T chnh lu.- nh sng lm vic trong trm.- Qut gi my bin p.- in tiu ph sinh hot.- Cc ng c in.

in t dng c vai tr v cng quan trng trong vn hnh, nu khng c in tdng trm bin p phi ngng vn hnh. Trong mt trm bin p 110kV thngthng s c 2 my bin p t dng, mi my bin p t dng phi ly in t mtmy bin p chnh khc nhau d phng nng.Khng c php ly in t dng cp cho cc ph ti tiu ph bn ngoi

phng kh nng gy s c ch quan lm mt in t dng, khng m bo an ton

cho vn hnh trm bin p.

Cu hi 37: Cho s mt trm bin p 110kV, hy cho bit cch c s vnhnh mt trm bin p:

- Thit b in.- V tr lp t.- Cch k hiu tn thit b theo s vn hnh.

Tr li :c s theo trnh t sau:

- Tn trm bin p.- Tng dung lng trm bin p cn gi l cng sut t (kVA)- S lng my bin p- Dung lng ca tng my bin p ( kVA ).- Cp in p ca tng my bin p (Cao p110/ Trung p kV/ Trung p kV) .- Nguon in 110kV cp n trm bin p.- Nu nhng c im ca s nu c(c dng s cu khng? C thanh ci

mch vng khng?...)- S lng h thng thanh ci trung p C1, C2, C3, C4 nu c

- Gii thiu v cc thit b in t trn cc h thng thanh ci (cu dao, my ctlin lc).- c tn thit b theo qui c trong s vn hnh:

+ MBA : T1 , T2.+ Thanh ci theo cp in p 110kV(C1110kV, C2110kV, C135kV, C2 35kV, C110kV...)

+ My ct lin lc thanh ci110kV - 112, 35kV- 312(334), 22kV- 412(434), , 10kV - 912(934), 6kV-612(634).

+ My bin dng in (TI - cp in p - t s bin dng)+ My bin in p (TU1 , TU2 , U s cp / 0,1kV )+ My bin p t dng TD1, TD2 ( U s cp / 0,4kV )+ My ct tng


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131, 132 l my ct tng 110kV331, 332 l my ct tng 35kV431, 432 l my ct tng 22kV931, 932 l my ct tng 10kV631, 632 l my ct tng 6kV.

+ Cu dao tng.+ Cu dao lin lc.+ Cc l ra

c theo trnh t: Cp in p, s 7 ( 8, 9), th t l ra.Th d: 172 ng dy 110kV l s 2.

371 ng dy 35kV l s 1.472 ng dy 22kV l s 2.974 ng dy 10kV l s 4.683 ng dy 6kV l s 3.

Cu hi 38: Cho s nguyn l b iu chnh in p di ti ca my bin p110kV hy gii thch cu to v nguyn l lm vic ca b iu chnh in p diti theo s cho?Tr li:B iu chnh in p di ti lm nhim v iu chnh in p ca my bin p

trong iu kin c ti.Gm 2 phn:

B cng tc P cn gi l dao la chn lm nhim v chn trc nc in p lmvic ca my bin p. B cng tc P nm trong thng du chnh ngay bn cnh

my bin p, cc u dy ca cun dy iu chnh u vo cng tc P. B cng tc Kcn gi l b cng tc dp la nm trong mt thng du ring gi

l thng du cng tc K. B cng tc K c vai tr gn ging nh mt my ctin, c tc lm vic cc nhanh t 45miligiy n 50miligiy chu cdng in ngn mch tm thi t 200 n 600A, thi gian ngn mch tm thi0,1 n 6miligiy l thi gian hai tip im la chn P cng ng mt lc to rangn mch mt s vng dy ca mt nc iu chnh phn p.

Khi dao la chn P chuyn ng trc v chn xong phn nc my bin p, btc K mi chuyn ng. Mi pha ca b cng tc K c 4 cp tip im, tng

i cp tip im c lp in tr hn ch dng in c cng sut 200A (600A)cn gi l in tr ngn mch. 4 tip im ng ca cng tc K c ni chung, 2 tip im tnh u v cui

ca cng tc K c ni vo hai u dao chn l ca cng tc P, 4 cp tip imca cng tc K c cu to hnh khi ch nht, tip im lm vic theo kiu ngthng to ra tip xc mt. Cng tc K theo chuyn ng theo kiu c cu cu ltngha l bin chuyn ng quay ca trc truyn thnh chuyn ng thng. Ccnc iu chnh ca cun dy iu chnh in p u vo dao la chn theo hchn (2,4,6,8,10),& l (1,3,5,7,9).

Thng thng my bin p c ch to cun dy iu chnh ring, dng thmmt dao o chiu. S u dy o chiu cc tnh c vai tr o ngc cc tnhcun dy iu chnh lm cho t thng ca cun dy iu chnh ngc vi chiu t


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thng ca cun dy chnh c tc dng tng gp i s lng nc iu chnh inp, gim bt c mt na s vng cun dy iu chnh,

u cc chung ca dao la chn u vo hai cc chnh 31 thuc h l, 32 thuch chn, vi pha A s c tn l 31A , 32A, vi pha B c tn l 31B, 32B vi pha Cc tn l 31C, 32C. u cc chung 3 pha ca cng tc K ni ra s trung tnh110kV MBA.

Gi s my bin p ang lm vic nc c l nc 1, nh vy tip im s 2 angni vo cc 32 A, nc s 1 ang ni vo cc 31A. Mun chuyn v nc 3 th daochn bn l phi chuyn t nc 1 v nc 3 trc, sau cng tc K bt v 31A.

Trong qu trnh cng tc Klm vic, 6 in tr R c tr s ging nhau (t 4 n 8) ging nhau dng hn ch dng in ngn mch ti thi im nc 3 v nc 2ca cun dy iu chnh b chp tt, lc ny in tr cc in tr R ng vai trph ti, Ton b 12 b tip im dng cho 3 pha ca cng tc K, 1 b tip im nichung ca b cng tc K (ni ra s trung tnh) v 6 in tr ca b cng tc K c ngm trong du. Khi ngn mch cun dy iu chnh, nhit lng sinh ra s

tn nhanh trong thng du cng tc K. Tt c cc chuyn ng trn u thc hinbng c cu c kh, l xo th nng t pha di b cng tc K. B cng tc P vcng tc K dng chung mt b truyn ng.C mt s b CA kiu hnh V, tip im ca b CADT chuyn ng lt

qua lt li, nguyn tc lm vic tng t ging nhau, ch khc nhau c cu truynng c kh.

S nguyn l b t ng iu chnhin p di ti biu din cho mt pha

-

1

+10

9 7

5

3

28 6 4

k

13

5

792468

10

R2

R1

32- a

31- a

cun dy chnh

Dao o chiu

Cun dy iu chnh

Dao lachn chn

Dao lachn l

Cng tc K

A

0


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Cu hi 39: Hy gii thch v sao my bin p 110kV/ 22kV/ 10kV phi dng t

u dy sao khng, sao khng, tam gic (Y0/ Y0/)?Cc my bin p phn phi h th cp in p 22kV/ 0,4kV phi dng phidng t u dy sao khng, sao khng (Y0/ Y0) hoc t u dy tam gic, saokhng (/ Y0)?Tr li :- Cc My bin p c cng sut ln thng dng 1 cun dy u chng snga hi bi 3 xut hin trong mch t gy nng my bin p v gy tn tht trongni b my bin p. Do my bin p 110kV/22kV/ 10kV phi dng t u dysao khng, sao khng, tam gic (Y0/ Y0/).

- Cc my bin p phn phi h th 22/ 0,4kV thng u Y0/ Y0 cn bngin p cho my bin p 110kV, nu trn li 22kV xut hin tnh trng lch ti (IA IB IC) th my bin p 110kV cng b nh hng, vic cn bng pha cng clm ging nh trn li in 380V/ 220V, trong trng hp ny li in 22kVphi lp thm dy trung tnh.- Do my bin p phn phi h th thng xuyn vn hnh trong lch pha dngin nn cp in p 22kV/ 0,4kV phi dng t u dy tam gic sao khng(/Y0), cun dy 22kV u c tc dng ngn nga nh hng ca s lch phadng in cho MBA 110kV, trong trng hp ny li in 22kV khng c dy

trung tnh.

Hnh vm t cu to b CADT

R le dng du Np y

Gin chp sng cng tc K


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Cu hi 40: Ti sao t in tng trung th v t lin lc trung th thng x dngba my bin dng, cc t in ng dy thng x dng hai my bin dng?Tr li:

+ Nu dng 3 my bin dng h thng bo v r le s lm vic tin cy hn nhngtn thm thit b. H thng r le u theo s b lc th t khng dng 3 TIu theo s hnh Y bo v qu dng v bo v chm t thanh ci .

+ i vi ng dy dng 2TI va cho bo v qu dng v bo v ct nhanhlm vic.

+ Vic lp TI 2 pha cho cc t ng dy ph hp vi h thng m in nngkhi dng cng t loi 3 pha 2 phn t.

Cu hi 41: Gii thiu cc bo v r le cho mt my bin p 110kV? Bo v solch my bin p lm vic nh th no? C g khc nhau gia bo v so lch vibo v qu dng, ct nhanh? Bo v qu dng v bo v ct nhanh c ng dngtrong s bo v r le no?

Tr li: Bo v chnh MBA gm c:

- Bo v So lch- Bo v ga Ct in cc pha khng thi gian.- Bo v dng du

Bo v d phng MBA:- Bo v qu dng 110kV Ct in cc pha c thi gian.- Bo v nhit du tng cao Bo tn hiu, khi ng qut gi.

Bo v So lch l bo v chnh cho my bin th da trn s so snh dngin th cp cc pha ca TI t trc v sau my bin th, quy nh vng bov so lch nm trong phm vi t TI cc pha ca my bin p. Khi vn hnhbnh thng do dng in th cp ca TI cc pha cn bng nn khng c dngin i qua r le so lch, khi c chm chp mt trong cc cun dy my bin pth dng in i qua b TI ca cun dy s tng ln t bin lm xut hindng in khng cn bng qua r le so lch. lin mt lc r le so lch khing tt c cc my ct in tng cc t ng tch my bin th b s c rakhi vn hnh.

Bo v So lch khc vi bo v qu dng v ct nhanh l:+ Trong bo v qu dng v ct nhanh lun tn ti dng in th cp 5A khis c dng in s tng ln t 1,5 n 7 ln so vi nh mc.+ Trong bo v so lch th khng khng bao gi c php c dng inkhng cn bng i qua r le so lch. Ch cn mt dng in rt nh xut hintrong r le so lch l bo v r le tc ng ngay. Trc khi a bo v solch vo lm vic cn phi th nghim hiu chnh sao cho dng in khng cnbng i qua r le so lch trit tiu hon ton.

I so lch = I1-2 + I2-2 = 0 (I1-2, I2-2 l dng in th cp ca TI1 v TI2).

Bo v qu dng, ct nhanh: Dng trong bo v r le cho ng dy v thanhci.


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Bo v qu dng: Dng trong bo v r le tng pha trung p v pha cao p110kV.

Cu hi 42: Hy nu ging nhau v khc nhau gia ni t lp li v ni t anton trn ng dy? Hy gii thch v sao tr s in tr tip a trong trm binp Rt 4, trong khi li quy nh in tr tip a lp li l Rt 10.Tr li :

Ging nhau:- Cng c lm trn ng dy.- Cc tip a u c chn chn su cch mt t khong 0.5m-0.8m.- C th dng b ni t c cu to ging nhau.Khc nhau:

- Nhim v ca tip a an ton l m bo an ton cho con ngi khi tip xcvi cc gi thit b mang in. Dy tip a lm bng dy thp m10, cni t x st n cc tip a.

- Nhim v ca tip a lp li l ngn nga nguy c qa ti in p ni b do

t dy trung tnh, ph hng thit b. Dy tip a lp li c lm bng dyng nhiu si c tit din ti thiu l 25mm2, c ni t dy trung ha ncc tip a.

in tr tip a trung im my bin p v tip a lp li c tr s khc nhau:+ Trong trm bin p tip a Rt 4.+ Trn ng dy thng lm tip a lp li ti v tr ct cui, ct gc, ct c

nhiu nhnh dy cng sut ln nn to thnh nhiu mch tip a song songc Rt 10.

1

Rtip a = R tip a Rtip a trung im my bin pnTh d : C 3 im tip a lp li th

Dng in th cp ca TII1-2 = I2 -2

Dng in i vo R le so lch = 0

TI1

TI2


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1R tll = 10 = 3,3 4

3Kt qu tnh ton cho thy tng gi tr in tr tip a lp li cng nh tng ng

vi gi tr in tr tip a ti trm. Mc d tr s Rt ti trm v Rtip a ca 1 vtr trn ng dy c khc nhau nhng vn m bo cho h thng tip a chunglm vic tt.

Cu hi 43: C my loi tip a trong li in cao h th? Hy nu cc quynh v cc tr s in tr tip a tiu chun trong trm bin p v ng dy trnkhng?Tr li :

Trong li in cao h th c 3 loi tip a : Tip a an ton: Bo m an ton cho ngi khi tip cn vi cc vt angmang in nh cc tip a v t in, cc gi thit b in, x s, v cp

in. Tip a lm vic: Bo m tnh trng lm vic bnh thng ca cc thit bin. Trong trm bin p tip a lm vic l tip a t ti trung im my binp, tip a lp li, tip a im cui cun dy tam gic h ca my bin in p,tip a im cui ca cun dy th cp my bin dng in. Tip a chng st: Chng qu in p kh quyn do st gy ra.

Quy nh v cc tr s in tr tip a tiu chun trong trm bin p v ngdy trn khng:

+ Tip a an ton

Trong trm bin p Rtip a 4 (vi trm bin p h p)Rtip a 10 (vi trm bin p cao p 6,10,35kV)Rtip a 0,5 (vi trm bin p cao p110kV)

Ngoi ng dy ty theo in tr sut ca t Rtip a s khc nhauNu t < 10

4 cm Rtip a = 10Nu 104 cm t 5.10

4 cm Rtip a = 15Nu 5.104 cm t 10

5 cm Rtip a = 20 t > 10

5 cm Rtip a = 30

+ Tip a lm vicTrong trm bin p : Rtip a 0,5.

Ngoi ng dy : Rtip a lp li 10.

+ Tip a chng st Rtip a 0,5.

Cu hi Tr li :


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im khng nit. ( )

r

+


65/157



+ + +

h s

Cu hi 45: Gii thch v sao cc tip a v cc b phn ni t phi chn succh mt t t 50- n 80cm?

Tr li:

125

250


66/157



in tr ca t c c trng bng tr s in tr sut k hiu l ( r ), lin tr ca 1 cm3 t ( hay ca 1m3 t ) c n v lcm ( haym ). phthuc vo

+ m ca t.+ nhit mi trng.+ chng loi t, cht ca t.+ thi gian trong nm( ma ).

Nhit ca t ph thuc vo rt nhiu nguyn nhn v c nh hng trc tipn in tr sut ca t. Kh m c trong t l nhng cht in phn, khi nhit tng ln th in tr sut ca t gim i, nhng kh m c trong t b bay i htth in tr ca t li tng ln rt nhanh.

Khi c dng in ln i qua (l dng in st hoc dng in chm t), nhit ca t tng hn 1000C lm cho qu trnh bc hi ca nc trong t tngnhanh, vng t trn c chiu dy t 50- 80cm thng kh ro, do cc b phnni t cn phi chn su di lp t t c vo min t c in tr sut

nh t c hiu qu kinh t v ch tiu kim loi.Khi thi cng cc cng trnh ni t cn phi m nn t cng cht cng tt,

cht ca t ph thuc vo mt lin kt gia cc ht trong t tng, khnng tip xc lm cho t dn in tt hn. cht ca t nh hng trc tipn tr s in tr ca t.

Th d: Nu tng p lc nn ln t t 0,2 n 9 Tn/m2 in tr ca t s gimi t 10 n 40%.

chn su ca b phn ni t

Mt t


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Bng tr s gn ng ca in tr sut () ca t v nc

Tn ca cc loi t v ncTr s in tr sut x104 cm

Thay itrong phm vi

Khi m bng1020% trong t

t st t pha st t ct t pha ct t en t vn, rung t ln nhiu si t sn ni t ln than bn

Nc bin Nc sng Nc ao h Nc sui Nc ngm

t 0,8 7 tr lnt 0,4 1,5 tr lnt 4,0 7,0 tr lnt 1,5 4,0 tr lnt 0,09 0,53 tr lnt 0,15 0,6 tr lnt 1,5 4,0 tr lnt 20 40 tr lnt 0,1 0,3 tr ln

t 0,002 0,01 tr lnt 0,1 1,0 tr lnt 0,4 0,5 tr lnt 0,1 0,6 tr lnt 0,2 0,7 tr ln

0,41,07,03,02,00,4--

0,2-

-----

Cu hi 46: Th no l ni t nhn to, ti sao b phn ni t nhn to lmbng thp m khng lm bng ng hoc bng nhm?Tr li :

Ni t nhn to l cc b phn ni t c chn xung t c hnh dngkhc nhau hn vi nhau v tip xc trc tip v in vi t. Cc b phn ni tthng c m thic hoc m km tip xc vi t tt hn.

B phn ni t gm c cc ni t v thanh ni t. Cc ni t thnglm bng cc loi thp: Thp trn c, thp gc, thp ng ng thng ng xungt su di mt t 0,5m0,8m. Thanh ni t hn lin h cc cc ni tvi nhau thng c ch to bng thp dt, thp trn c.

Ti vng t gn bin hay gn cc nh my ho cht tit din khng cnh hn 100mm2. Cc tiu chun quy nh trong bng phi tng ln gp 2.

Dng ng lm b phn ni t cng c nhng gi thnh cao, nu nmgn vt lm bng kim loi nh v ng cp in, ng nc...s xut hin dngin in phn i trong t: ng l cc catt, cc vt lm bng kim loi kia lcc ant, sau mt thi gian cc b phn bng kim loi kia s b n mn v b phhu do in phn. Do khng c dng ng lm b phn ni t.

Khng dng nhm lm b phn ni t v khi b chn trong t nhmthng b n mn ho hc rt nhanh.


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BNG KCH THC CA CC LOI THP DNG LM B PHN NI T

Loi thp t trong nh

t ngoi tri

Chn trong t

Thp trn c 5mm 6mm 6mmThp gc Tit din 24mm2

Dy 2mmTit din 48mm2

Dy 2,5mmTit din 48mm2

Dy 4mmThp ng Dy 1,5mm Dy 2,5mm Dy 3,5mmThanh bng thp dt Tit din 24mm2

Dy 3mmTit din 48mm2

Dy 4mmTit din 48mm2

Dy 4mm

Cu hi 47: Trnh by cch tnh ton n gin in tr ca cc b phn ni tdng cc v thanh ni ngang trong li in c tn s cng nghip l 50HZ?

Tr li:Khi tnh ton in tr ni t

Phi da vo tiu chun ni t so snh ( xem thm cu hi 43, 44 ) Phi bit loi t v nc ca v tr lm tip t chn c tr s in tr

sut tng i - m ( xem thm cu hi 45 )1- Tnh in tr (rc) ca mt cc chn thng ng trong t, t c thnh phn cuto ng nht ( = khng i):

Dng cng thc rc = (lg + lg ) []

1 d 2 4t - 1Trong : - in tr sut ca tm.l - Chiu di cc m.d - ng knh ngoi ca cc m.t - chn su ca cc, m ( tnh t mt t n im gia ca cc )

2,30,366(*) l t s trong 2,3 l h s chuyn i t lgarit t nhin- ln

sang lgarit c s 10 (lg ).

Nu coi nh vng t c cu to ng nht ( = const ) th c th dngcng thc tnh ton s b:

rc = [ ]

l

0,366(*) 2l 1 4t + l


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Nu cc dng loi thp gc th tnh iv thp trn bng cng thc

dgc = 0,95d

Th d:Cc c chiu di l = 5m, ng knh d =12mm,

c chn su t = 0,7 + 2,5 m = 3,2m, thay vo cng thc

rc = (lg + lg ) []1 d 2 4t - l

Ta c rc = 0,228. []Gi s loi t pha ctTra bng chn : = 2.104 .cm = 2.102 .m

(xem bng tr s gn ng cu hi 45 )

rc = (lg + lg ) []5 0,012 2 4.3,2 - 5

rc = 45,6.Nu tnh s b:

2.102

rc = = = 40.

l 5

2- Tnh in tr ( rth ) ca mt thanh nm ngang trong t, t c thnh phn cuto ng nht ( khng i ):Thanh ngang kt hp vi cc thp chn thng ng trong t to thnh mt b

phn ni t hn hp cc v thanh lm tng hiu qu s dng. Thanh ngang clm bng thp dt hoc thp trn.

in tr ca mt thanh t nm ngang trong t c xc nh theo cng thc:

Vi thp dt:

0,366(*) 2l 1 4t + l

0,366(*) 2.5 1 4.3,2 + 5


70/157



Trong : l - Chiu di ca thanh,mrth = lg b - Chiu rng ca thanh, m

t - chn su ca thanh( so vi mt t ), m

Vi thp trn:Trong : l - Chiu di ca thanh,m

rth = lg , d - ng knh ca thp trn, mt - chn su ca thanh

( so vi mt t ), mDng cng thc rt gn:

Trong : L- tng chiu di ca cc dy dnrth = lg , ca b phn ni t, cm

t - chn su ca thanh( so vi mt t ), m

Cng thc tnh s b: d - ng knh ca thp trn, mK - l h s ph thuc vo hnh dng

ca b phn ni t trong bng

Kiu b phn ni tK hiu quy c

l1/l2 K

- 1

- 1,27

- 1,46

- 2,38

- 5,53

- 8,45

l1

l2

1,523

4

5,816,428,17

10,4

o,366

1

2l 2

b.t

o,366

1

l 2

d.t

o 37

L

KL2

t.d

2rth

l

BNG TRA H S K


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Cu hi 48: Cch xc nh in tr thun ca 1 cun dy my bin p 3 pha khicun dy u?Tr li:Ta ln lt o in tr thun ca ca cc cun dy my bin p theo s sau:

S thay th 1 S thay th 2 S thay th 3

Khi o in tr mt chiu ca cc cun dy my bin p 3 pha u bng cu oin tr s khng xc nh c tr s in tr thun ca tng pha ca cun dy v

lc ny s o ca cu o ch cho bit tr s tng tr ca cc cun dyTh d: Tng tr ca RAB nu tnh ton theo s thay th 1 s l

( Rca + Rbc). Rab Rca Rab + Rbc RbcRAB = =

( Rca + Rbc) + Rab Rca + Rbc + Rab

Mun tm c tr s in tr thun ca tng pha cun dy ta phi tnh ton litheo cng thc di y:

( RAB + RBC - RCA )( RAB - RBC + RCA)2 ( - RAB + RBC + RCA )

( RAB + RBC - RCA ) ( - RAB + RBC + RCA)2( RAB - RBC + RCA )

( RAB + RBC - RCA ) ( - RAB + RBC + RCA)2( RAB + RBC - RCA )

Rab = RAB +

Rbc = RBC +

Rca = RCA +


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Cu hi 49: Dng in khng ti ca my bin p l g? Cch th nghim xcnh dng in khng ti ca mt my bin p?

Tr li:Khi my bin p c u vo ngun in, cun dy th cp my bin p h

mch, trong cun dy s cp my bin p s c dng in khng ti chy qua.Dng in khng ti c k hiu l Io.Khi my bin p vn hnh khng ti s xut hin t thng khp kn chy trong li

thp, do c t tr nn li thp b pht nng gy ra tn hao khng ti. Tn haokhng ti c xc nh gin tip qua s o ca dng in Io. Dng in khng tiIo cho bit mc tn hao khng ti ca my bin p ln hay nh. Dng inkhng ti thng c tiu chun ho vi tng nh ch to.

ln ca dng in khng ti ph thuc vo.- Cht lng thp si lch dng lm mch t c thm t cao hay thp.- dy ca li thp si lch.- Cht lng cch in ca l thp.

- Cng ngh ch to (t dp, lp ghp mch t ...) tt hay xu.Th nghim khng ti trc khi vn hnh thng c lm nh sau:

- Dng hp b th nghim lm thit b o (hp b K50 hoc K540).- To in p thp 220V~ a vo cun dy my bin p c in p nh

mc nh, cun dy cn li h mch.

S nguyn l th nghim khng ti 1 pha

Trong vn hnh dng khng ti Io o c khng cn ng bng tr

s thc m ch dng lm c s xc nh xem cun dy ca my bin p c bchm chp hay khng. Nu c hin tng chm chp trong cun dy th dng in

My bin p My bin po lng Th nghim

U~


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khng ti gia cc pha o c s b lch nhau v s sai khc vi dng khng tica nh ch to, lc ny khng c php ng in my bin p.

V cc t thng 3 pha i qua tr gia ca li thp b ngc chiu nhau nn ti trgia t thng s c tr s nh hn t thng ca 2 tr bn, dn n dng in khngti ca pha B nh hn dng in khng ti ca hai pha A v C. Dng in khngti ca 2 pha bn A v C bng nhau. Trng hp khi lm th nghim khng ti bngngun in 1 pha cng s xut hin s lch dng khng ti tng t nh trnghp th nghim dng khng ti 3 pha nhng nguyn nhn li do tr gia (pha B) ctn tht t ln hn hai tr bn (pha A,C).Ch : Trc khi lm th nghim khng ti ngi ta thng quay in tr cch

in bng Mgmmt o in tr 1 chiu ca cc cun dy bng cu o, k V vy trc khi lm th nghimkhng ti cn phi kh in tch d bng cch ln lt chp tt cc cun dy camy bin p bo v thit b o v trnh sai s ca php o.

in

in p nh mc chun ca in nn

u cc


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BNG TRA CP CHNH XC V PHM VI NG DNGCA MY BIN DNG V MY BIN IN P

Cp chnhxc

My bin dng My bin in pPhm vi ng dngI1

I1mSai s ln nht Sai s ln nhtV dngin [%]

V gc[pht]

V inp[%]

V gc[pht]

0,2 1001202010

0,20,350,5

101520

0,2 0,2 Dng trong o lngchnh xc, trong thnghim...vv

0,5

1

10012020

101001202010

0,50,75

1,01,01,52,0

4050

60180100120

0,5

1

20

40

Dng trong cc dngc o v r le trong

cc nh my in vtrm bin p, ringo m in nngdng cp 0,5.

3,010,0

12050050120

3,010,0

khngquy nh

3,0 khngquy nh

r le thng thng vng h ch th

BNG LA CHN V KIM TRA MY BIN DNG

tht

Tn i lng la chn v kim tra K hiu Cng thc tnh ton

1 in p nh mc[kV] U1mBI UmBI Ummng2 Dng in s cp nh mc[A] I1mBI I1mBI Ilvmax3 Ph ti nh mc ca cun dy th cp S2m S2mBI S2tt

4 H s n nh lc in ng trong kixk

k 2 I1mBI

5 Lc tc dng cho php ln u s, kG Fcfl

Fcf 0,88.10-2. i2xk [kG]a

6 H s n nh nhit kn

I. tgtkn

I1mBI t2 n

v mybin in p

r le bochm t

Cun th cp u tam gic h

S NGUYN L MY BIN IN P

R3U0

U1~

U2=100V~

cuch


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