B GIO DC V O TO

I HC NNG

NGUYN NGC DNG

PHI HP TC NG GIA THIT B BO V V T NG

TRONG H THNG IN

CHUYN NGNH: MNG V H THNG IN M S: 60.52.50

LUN VN THC S K THUT

Ngi hng dn khoa hc : PGS TS L KIM HNG

NNG 2005

LI CM N Sau mt thi gian hc tp, c s ng ca nh trng, cc thy gio

Khoa in ca trng i hc Bch khoa Nng v trng i hc Bch khoa

H Ni, n nay bn lun vn tt nghip hon thnh.

Tc gi v cng bit n s gip v hng dn tn tnh, chu o ca thy gio

PGS TS L Kim Hng trong sut thi gian hc tp v thc hin bn lun vn ny.

Tc gi xin chn thnh cm n thy gio ThS L Vn, thy gio TS Trn

Vinh Tnh v cc thy gio trong Khoa in c nhng gp nhit tnh, su sc

trong bui bo v cng chi tit lun vn thc s.

Tc gi cng xin chn thnh cm n Ban Gim c i hc Nng,

Khoa in trng i hc Bch khoa Nng, Khoa in trng i hc

Bch khoa H Ni, ThS Ng Vn B (Trng phng K thut L Nng), k

s Hong ng Nam (phng iu L Nng), cc hc vin kha 6 ngnh

Mng v H thng in, gip , cung cp ti liu tc gi nghin cu v

thc hin bn lun vn ny.

Xin chn thnh cm n.

Tc gi

LI CAM OAN

Ti xin cam oan y l cng trnh nghin cu ca ring ti.

Cc s liu, kt qu nu trong lun n l trung thc v cha tng c ai

cng b trong bt k cng trnh no khc.

Tc gi lun vn

NGUYN NGC DNG

MC LC Trang ph ba

Li cam oan

Mc lc

Danh mc cc ch vit tt

Danh mc bn v

M u Trang

Chng 1 PHI HP BO V H THNG IN BNG

CU CH V BO V QU DNG 1 1.1 Cc phng thc phi hp tc ng trong bo v qu dng 1

1.1.1 Phng thc phi hp theo thi gian 1

1.1.2 Phng thc phi hp theo dng 1

1.1.3 Phng thc phi hp bo v hn hp 2

1.2 Phi hp bo v gia cu ch v cu ch 2

1.2.1 Cu ch t ri (FCO) 2

1.1.2 Phi hp bo v gia cu ch v cu ch 3

1.3 Phi hp bo v gia rle qu dng v cu ch 7

1.3.1 Rle c c tnh thi gian ph thuc 7

1.3.2 Cc tiu chun c tuyn ca bo v qu dng vi

thi gian ph thuc 8

1.3.3 Phi hp bo v gia cu ch v rle qu dng. 9

1.4 Phi hp bo v gia rle v rle 11

1.4.1 phn cp thi gian vi c tnh ph thuc 12

1.4.2 Nguyn tc phi hp. 12

Chng 2 PHI HP TC NG GIA TL V

THIT B BO V TRN LI PHN PHI 14

2.1 Phi hp tc ng gia my ct t ng li (ACR) 14

v cu ch

2.1.1 My ct t ng li (ACR) 14

2.1.2 Phi hp gia ACR v cu ch 21

2.2 Phi hp ACR v ACR. 28

2.2.1 i vi ACR thy lc 28

2.2.2 i vi ACR in t 29

2.3 Phi hp ACR v rle 30

2.4 Phi hp gia ACR v dao cch ly phn on t ng (SEC) 30

2.4.1 Tng quan v dao cch ly phn on t ng (SEC) 31

2.4.2 Phn loi v cc thng s khi la chn SEC 32

2.4.3 Phi hp gia ACR v SEC 32

Chng 3 PHI HP TC NG GIA TL V THIT B

BO V TRN LI TRUYN TI 39

3.1 Phi hp bo v bng cch kt hp MC vi h thng TL (ARS) 39

3.1.1 TL trn ng dy cao p v siu cao p 40

3.1.2 nh hng ca TL i vi n nh h thng 44

3.1.3 T ng li mt pha 45

3.2 Phi hp bo v gia TL v bo v khong cch 46

3.2.1 Tng quan 46

3.22 Cc cng thc tnh ton bo v khong cch thng dng 46

3.2.3 S vng I m rng 50

3.2.4 S tng tc theo th t bng vng I m rng 54

3.2.5 S tng tc vng II kt hp RAR v DAR 55

Chng 4 T NG HA MCH VNG 62

4.1 Tm hiu v t ng ha mch vng 62

4.1.1 ngha 62

4.1.2 Tm hiu hat ng s t ng ha mch vng 62

4.1.3 Nhng chc nng c bn ca t ng ha mch vng 64

4.1.4 S nh thi trong s t ng ha mch vng 64

4.2 Cc ch v thng s trong t ng ha mch vng 65

4.2.1 Cc ch trong t ng ha mch vng 65

4.2.2 Cc thng s trong t ng ha mch vng 66

4.3 Hat ng ca mch vng khi c s c xy ra trn cc phn on 68

4.3.1 Khi s c lu di trn phn on A 69

4.3.2 Khi s c lu di trn phn on B. 70

4.3.3 Khi s c lu di trn phn on C 71

4.4 Bng cc trng thi ca TL khi khi ng t ng 72

ha mch vng

4.41 Bng cc trng thi ca Feeder Recloser (FR) 72

4.42 Bng cc trng thi ca Mid- point Recloser (MR) 73

4.41 Bng cc trng thi ca Tie Recloser (TR) 73

4.5 T ng chuyn ti 74

4.5.1 ngha 74

4.5.2 Hot ng ca s t ng chuyn ti 75

4.5.3 S chuyn ti tr li bng tay 76

4.5.4 S chuyn ti tr li t ng 76

4.6 Phn on vng 77

4.6.1 ngha 77

4.6.2 Hot ng ca s khi SEC c t c mt ln m 78

Chng 5 NG DNG TNH TON CHO LI IN

PHN PHI TI NNG 80

(Xut tuyn 471 c cp ngun ti cc trm E10, E11)

5.1 Gii thiu xut tuyn 471E10-E11 80

5.1.1 Tng quan 80

5.1.2 Quy m ng dy 471 81

5.1.3 Cc phng thc vn hnh 81

5.1.4 Cc thit b bo v c trn xut tuyn 471E10-E11 81

5.2 Tnh ton cc thng s khi vn hnh bnh thng 82

5.2.1Tnh ton cc thng s 83

5.2.2 Bng thng s ng dy 471E11 (cp in 471E10) 83

5.2.3 Bng thng s ng dy 471E10 (cp in 471E11) 84

5.3 Tnh chn tr s chnh nh bo v rle trn li hin ti 85

5.3.1 Cc cng thc tnh ton 85

5.3.2 Kt qu tnh ton tri s chnh nh rle 89

5.3.3 Phi hp bo v bng phn mm VPROII 89

5.3.4 Phn on mch vng bng SEC 95

Kt lun. 97

DANH MC CC CH VIT TT

ACR : My ct t ng li ARS : My ct kt hp t ng li

BV : Bo v

BVKC : Bo v khong cch

BVQD : Bo v qu dng

BI : bin dng

BU : Bin in p

DLC : Dao cch ly

EIT : ng cong cc k dc

FCO : Cu ch t ri

HT : H thng in

LPP : Li in phn phi

MBA : My bin p

MC : My ct

SIT : ng cong dc chun

SEC : Dao cch ly phn on t ng

TBA : Trm bin p

TC : c tnh thi gian dng in

TL : T ng ng li

TD : H s chn thi gian

VIT : ng cong rt dc

XT : Xut tuyn

DANH MC BN V

Tn ti: Phi hp tc ng gia thit b bo v v t ng trong h thng in STT Tn bn v S bn v

1 H ng cong nng chy nh nht cu ch loi K 1.1 2 Cu ch gn ngun v xa ngun 1.2 3 Cc dng c tnh thi gian ph thuc 1.3 4 S phi hp c tuyn lm vic 1.4 5 Xc nh phn cp v thi gian 1.5 6 Nguyn tc phi hp cc bo v qu dng lin k 1.6 7 c tnh TC tiu biu ca ACR thy lc 2.1 8 S khi ca mch iu khin ACR 2.2 9 c tnh TC tiu biu ca ACR iu khin in t 2.3

10 c tnh TC tiu biu ca ACR iu khin in t 2.4 11 Minh ha s dng c tnh ct nhanh ca ACR 2.5 12 M t hot ng ng thi ca 2 ACR 2.6a 13 M t hot ng khng ng thi ca 2 ACR 2.6b 14 M t hot ng c phi hp chui 2.7 15 Phi hp c tnh ACR v cu ch 2.8 16 S phi hp ACR v cu ch 2.9 17 Chu k nhit cu ch 2.10 18 Minh ha phi hp gia ACR v cu ch pha ngun 2.11 19 Minh ha phi hp gia ACR v cu ch pha ti 2.12 20 Minh ha phi hp gia ccACR thy lc 2.13 21 Phi hp cc ACR mng hnh tia 2.14 22 Minh ha phi hp gia cc ACR in t 2.15 23 S khi ca SEC 2.16 24 S mng in phi hp thit b t ng 2.17 25 S thit k 2 xut tuyn 2.18 26 Dao cch ly phn on loi nhn tn hiu p 2.19 27 S hot ng gia ACR v SEC trong mng hnh tia 2.20 28 Phi hp thi gian hot ng ca mng hnh tia 2.21 29 S phi hp gia ACR v SEC trn mng c ngun 2 pha 2.22 30 Gin phi hp thi gian hot ng ca mng 2.23 31 S ng dy lin kt hai h thng 3.1 32 Gc quay ca roto my pht 3.2 33 Cng sut theo gc quay momen 3.3 34 Hiu qu ca TL 3 pha i vi n nh h thng 3.4 35 Thi gian gin on cng sut khi TL mt hoc 3 pha 3.5 36 Xc dnh cc vng khong cch ca BVKC 3 cp 3.6 37 S BVKC c vng I m rng 3.7 38 Ci t phng thc hot ng ca mch ARC theo thanh ci 3.8

39 Ci t phng thc hot ng ca mch ARC theo phn ng dy

3.9

40 S tng tc BV theo th t bng vng I m rng 3.10 41 S tng tc vng II kt hp vi RAR v DAR 3.11 42 Thao tc ca s t ng ng li ARC mt ln 3.12 43 Biu trnh t thi gian cc chu trnh RAR v DAR 3.13 44 S t ng ho mch vng n gin 4.1 45 S t ng chuyn ti 4.2 46 S t ng ho mch vng in hnh 4.3 47 Khi s c xy ra trn phn on A 4.4 48 Khi s c xy ra trn phn on B 4.5 49 Khi s c xy ra trn phn on C 4.6 50 S mch chuyn ti 4.7 51 S chuyn ti bng tay dng TL 4.8 52 S chuyn ti tr li t ng dng 2 TL 4.9 53 S mch vng khi c t SEC 4.10 54 S mch vng khi t SEC c mt ln m 4.11 55 S xut tuyn 471 E10 - E11 5.1 56 S xut tuyn 471 E11 (cp in 471 E10) 5.2 57 S xut tuyn 471 E10 (cp in 471 E11) 5.3 58 S xut tuyn 471 E11 cp in 471 E10 5.4 59 c tuyn phi hp gia cc TL trn ng dy 471 E11

(cp in 471 E10)- khi chm t 5.5

60 c tuyn phi hp gia cc TL trn ng dy 471 E11 (cp in 471 E10)- khi chm pha

5.6

61 S xut tuyn 471 E10 cp in 471 E11 5.7 62 c tuyn phi hp gia cc TL trn ng dy 471 E10

(cp in 471 E11)- khi chm t 5.8

63 c tuyn phi hp gia cc TL trn ng dy 471 E11 (cp in 471 E10)- khi chm pha

5.9

64 S ng dng SEC trn xut tuyn 471 E10 E11 5.10

M U

1. L do chn ti

mt h thng in vn hnh c n nh v tin cy, th cc thit b bo

v v t ng trn ng dy phi tc ng c khi c ngn mch t im s dng

n ngun in. Cc gi tr t (dng, p, thi gian tc ng) phi c tnh ton

chnh xc cho tt c cc thit b trn cng mt nhnh, mt xut tuyn bo m s

phn bit v tc ng c chn lc.

i vi li truyn ti cao p v siu cao p. Kinh nghim vn hnh cho

thy, vi ng dy trn khng c in p cng cao th cng xut hin nhiu cc s

c thong qua, chng chim mt t l rt ln (80 - 90%). Do vy, trong phn ln cc

trng hp nu ng dy c s c c c lp tc thi v t ng li thnh cng th s

gp phn ci thin tin cy cng nh gi n nh v ng b cho h thng.

i vi li in phn phi do c cc c im khc hn li truyn ti nh

cp in p

cch hp l khi xy ra s c, hn ch khu vc b mt in, qua gp phn nng

cao tin cy cng nh tnh n nh ca h thng.

- Phm vi nghin cu ca ti l kho st mt cch chi tit cc thit b bo

v c trn li in cng cc nguyn tc phi hp gia cc thit b ny. Ngoi ra, t

ng ho mch vng cng l mt vn thuc phm vi nghin cu ca ti ny.

T vic kho st l thuyt kt hp vi kt qu tnh ton ngn mch v chnh nh

ci t rle da vo phn mm VPRO II, ti cng a ra c mt phng n

phi hp hp l cho mt xut tuyn c th no trn li phn phi.

3. Mc tiu v nhim v nghin cu

Mc tiu v nhim v nghin cu ca ti l ng dng s phi hp tc ng

gia thit b bo v v t ng thc hin cc yu cu c bn sau y khi vn hnh h

thng in.

- Phi bo m tnh ct chn lc ch tch ri khi h thng on ng dy

hay xut tuyn c s c duy tr.

- Phi c lp nhanh s c ngn chn s h hng ca cc thit b lm sp h

thng.

- Ton b ph ti ch b ngng cung cp in khi c s c lu di gn ngun in.

4. B cc ca ti

Ni dung c trnh by trong tp lun vn ny gm 5 chng:

Chng 1: Phi hp bo v h thng in bng cu ch v bo v qu dng

Chng 2: Phi hp tc ng gia TL v thit b bo v trn li phn phi

Chng 3: Phi hp tc ng gia TL v thit b bo v trn li truyn ti

Chng 4: T ng ho mch vng

Chng 5: ng dng tnh ton cho li in phn phi ti Nng.

Trong 4 chng u ch mang tnh kho st l thuyt, ring chng 5 l phn

ng dng v chng ny s c p dng tnh ton c th cho cc xut tuyn trn

li in phn phi ti Nng.

Chng 1

PHI HP BO V H THNG IN BNG

CU CH V BO V QU DNG Bo v h thng in bng cu ch v rle qu dng l mt dng bo v n gin nht v c gi thnh r nht trong s cc loi bo v c dng trong h thng in.

Nguyn tc chung ca loi bo v ny l khi dng in qua ch t thit b

bo v, vt qu ngng cho php trong mt thi gian xc nh th thit b bo v

s tc ng v c lp nhanh s c ra khi li in.

Trn li phn phi loi bo v ny c xem l bo v chnh, thng c

lp t u cc xut tuyn v cc nhnh r nhm mc ch cch ly MBA hay trc

chnh h p ra khi h thng khi c s c. Tuy nhin h thng vn hnh c n

nh, tin cy, bo m c tnh chn lc s c th cc thit b bo v trn cng mt

nhnh, mt xut tuyn cn phi c mt s phi hp bo v chnh xc.

1.1 CC PHNG THC PHI HP TC NG TRONG BO V QU

DNG

Trong bo v qu dng tn ti 3 phng thc phi hp bo v sau y:

- Phng thc phi hp theo thi gian

- Phng thc phi hp theo dng

- Phng thc phi hp hn hp

1.1.1 Phng thc phi hp theo thi gian

y l phng php ph bin nht trong phi hp bo v qu dng lin k.

Nguyn tc ca phng php ny l: chn thi gian ca bo v th n (tnh t pha

ti) sao cho ln hn mt khong thi gian t so vi thi gian tc ng lu nht ca

cp bo v lin k trc n (tnh t pha ti)

tn = t(n-1)max + t (1.1)

1.1.2 Phng thc phi hp theo dng

Phi hp bo v theo gi tr dng c s dng da trn nguyn tc l dng

s c gim dn khi khong cch t ngun n im s c tng ln. Tuy nhin

phng php ny c 2 nhc im:

- Cn phi bit cng sut ngn mch ca ngun v tng tr ca ng dy

gia 2 im t thit b bo v m ta cn tin hnh phi hp.

- chnh xc ca bo v km i vi cc v tr gn ngun c cng sut ngn

mch bin ng mnh v khi dng s c cc cp bo v t thay i.

1.1.3 Phng thc phi hp bo v hn hp

Phng php ny l mt s kt hp ca 2 phng php trn v c ng

dng trn cc xut tuyn c cu trc phc tp gm nhiu nhnh r v khi thit b

bo v u tuyn c thi gian tc ng nh trc.

1.2 PHI HP BO V GIA CU CH V CU CH

Bo v mch in v cc thit b din trong mng phn phi n gin nht l

dng cu ch. Cu ch l phn bo v qu dng in v cu ch b nng chy do

nhit khi c qu dng in qua n. L mt loi bo v khng cc b, c vng tc

ng thay i trong mt khong rng ty theo dng ngn mch, nn gii hn ca n

khng th xc nh trc bi cc gi tr t ca bo v. V vy khng b st khu

vc trong i tng bo v, ngi ta thng ci t chng nhng v tr c vng

tc ng ln sang vng tc ng ca cc bo v lin k v iu ny lm ny sinh

mt vn l s gp nhiu tr ngi trong vic chn lc loi tr s c. Do vy,

khi b tr cu ch u cc xut tuyn v c xem l bo v chnh, th ngi ta

s dng mt s phng php phi hp gia cu ch v cu ch nhm trnh hin tng

hai hay nhiu cu ch c th tc ng khi c mt s c xy ra gim thiu thi gian

ngng cp in cho ph ti xa im xy ra s c.

1.2.1 Cu ch t ri (FCO)

Cu ch t ri c thit k cho mng phn phi in th di 35KV. Cu

ch t ri c th lm vic nh mt dao cch ly thao tc c, cho php ngi vn

hnh m mch bng tay.

i vi cu ch ngi ta thng quan tm n cc yu cu sau:

- Th nht l dp tt c h quang.

- Th hai l phi chu c in th nh mc khi dy ch t.

- Th ba l d dng phi hp vi cu ch khc trong b phn bo v khc.

ng cong c tnh thi gian -

dng in ca cu ch c hai dng: thi

gian nng chy nh nht v thi gian t

tng.

0.1

1

10

100

1000 200 140

100

65

25 40

15 - Thi gian nng nh nht l thi

gian t ch v khng c h quang xy ra

khi th nghim vi in th thp. Hnh

1.1 gii thiu h ng cong nng chy

nh nht cu ch loi K.

- Thi gian t tng l thi gian

chy dy ch v thi gian h quang khi

th nghim vi in th cao (khong

7200V). 0.01

103 1041021011(A)

Hnh 1.!: H ng congnng

chy nh nht cu ch loi K

1.2.2 Phi hp bo v gia cu ch (FCO) v cu ch (FCO)

Hin nay c 3 phng php c s dng trong vic phi hp bo v gia

cc cu ch l:

- Phng php phi hp dng bng phi hp.

- Phng php phi hp theo kinh nghim.

- Phng php phi hp dng c tuyn thi gian - dng in TC.

1.2.2.1 Phng php dng bng phi hp

Dy ch trong mng phn phi thng c hai loi k hiu l K v T. S khc

nhau ca chng l thi gian nng chy ch. Vi cu ch loi K th t s tc nng

chy nm trong khong t 0,6 n 8,1; trong khi loi T t 10 n 13. Do c tc

nng chy khc nhau v vy phi hp bo v c d dng ch nn s dng

cc cu ch cng loi.

Nh ch to thng cung cp cc c tnh phi hp ch ra cc gii hn

phi hp c ngh khi dng mt loi ch c th no .

Ngun Ti Cu ch gn ngun B' Cu ch xa ngun

Ti

A B

Hnh 1.2: Cu ch gn ngun v xa ngun

Bng 1.1: Phi hp gia cu ch v cu ch loi K nh

mc dy ch

di

nh mc dy ch trn

Dy ch 8K 10K 12K 15K 20K 25K 30K 40K 50K 65K 80K 100K 140K 200K

Loi ch Dng s c ln nht qua cu ch di (A)

6K 190 350 510 650 840 1060 1340 1700 2200 2800 3900 5800 9200

8K 210 240 650 840 1060 1340 1700 2200 2800 3900 5800 9200

10K 300 540 840 1060 1340 1700 2200 2800 3900 5800 9200

12K 320 710 1060 1340 1700 2200 2800 3900 5800 9200

15K 430 870 1340 1700 2200 2800 3900 5800 9200

20K 500 1100 1700 2200 2800 3900 5800 9200

25K 660 1350 2200 2800 3900 5800 9200

30K 850 1700 2800 3900 5800 9200

40K 1100 2200 3900 5800 9200

50K 1450 3900 5800 9200

60K 2400 5800 9200

80K 4500 9200

100K 2000 9100

140K 4000

T bng c tnh phi hp ny ta tham kho chn cu ch gn ngun v cu

ch xa ngun trong vic phi hp bo v:

Yu cu c bn ca phng php ny l: khi c ngn mch pha ti ca dy

ch xa ngun th dy ch ny phi ct v s c c c lp m khng cn thit phi

ct dy ch pha u ngun. Dy ch u ngun phi c nh mc cao hn v c

phi hp tt vi dy ch xa ngun c s hat ng chnh xc.

Lut phi hp yu cu thi gian ct ti a ca dy ch xa ngun s khng ln

hn 75% ca thi gian nng chy ti thiu ca dy ch gn ngun. iu ny s bo

m dy ch xa ngun s tc ng nhanh khng lm dy ch gn ngun tc ng

do nng chy tng phn.

Ngoi nhng gi tr phi hp ch, cng cn quan tm n kh nng dng lin

tc ca mi cp ch. Cc gi tr ny c cho trong bng sau:

Cc bng phi hp 1.1 v 1.2 cho ta mt phng php rt tin li phi hp

bo v gia cu ch vi cu ch.

Bng 1.2: Phi hp gia cu ch v cu ch loi T nh

mc dy ch

di

nh mc dy ch trn

Dy ch 8T 10T 12T 15T 20T 25T 30T 40T 50T 65T 80T 100T 140T 200T

Loi ch Dng s c ln nht qua cu ch di (A)

6T 350 600 920 1200 1500 2000 2540 3200 4100 5000 6100 9700 15200

8T 375 800 1200 1500 2000 2540 3200 4100 5000 6100 9700 15200

10T 530 1100 1500 2000 2540 3200 4100 5000 6100 9700 15200

12T 680 1280 2000 2540 3200 4100 5000 6100 9700 15200

15T 730 1700 2540 3200 4100 5000 6100 9700 15200

20T 990 2100 3200 4100 5000 6100 9700 15200

25T 1400 2600 4100 5000 6100 9700 15200

30T 1500 3100 5000 6100 9700 15200

40T 1700 4400 6100 9700 15200

50T 1750 4400 9700 15200

60T 2200 9700 15200

80T 7200 15200

100T 4000 13800

140T 7500

Bng 1.3: Kh nng dng lin tc

K hoc T Dng lin tc K hoc T Dng lin tc K hoc T Dng lin tc

6 9 20 30 65 95

8 12 25 38 80 120+

10 15 30 45 100 150+

12 18 40 60* 140 190

15 23 50 70* 200 200

1.2.2.2 Phng php phi hp theo kinh nghim

Phng php ny t c s dng do km chnh xc v khng th m rng

phi hp c khi trn xut tuyn cn b tr nhiu cu ch bo v. phi c d

dng ch nn dng cc cu ch cng loi v dy ch u ngun phi c chn sao

cho c dng nng chy cc i ln gp nhiu ln dy ch lin k (tnh t pha ti)

1.2.2.3 Phng php phi hp dng c tuyn TC

Nh bit c tuyn thi gian - dng in TC ca cu ch c 2 dng: thi

gian nng chy nh nht v thi gian ngt tng ln nht.

T hai c tnh thi gian ny ngi ta a ra c nguyn tc phi hp nh sau:

- ng cong ngt tng c dng phi hp vi c tnh nng chy nh

nht ca cu ch c nh mc ln hn t ti u ngun.

- ng cong nng chy nh nht c dng phi hp vi ng cong

ngt tng ca cu ch c nh mc nh hn pha ti.

Tuy nhin, khi s dng phng php phi hp ny cn ch n cc yu t

c th lm nh hng n c tnh chy nh nht ca cu ch nh:

- Sai s ca thit b. Tt c cc thit b in u c sai s, cc sai s ny ln hay

nh ty thuc vo cng ngh sn xut, k thut ng dng ca nh ch to.

- Nhit ca mi trng chung quanh. Cc ng cong TC c xy dng

vi nhit mi trng l 25o C. Nu nhit cao hn s lm gim thi gian nng

chy v thp hn th s ngc li.

- Hiu ng ca cc dng s c trc . Khi TL nhiu ln khng thnh

cng, cc dng s c c gi tr gn vi ng cong nng chy nh nht chy qua

cu ch lm tng nhit ca cu ch. Do , thi gian chy nh nht ca n gim

xung. trnh nh hng ca hiu ng ny, cu ch bo v nn c cho php

chu c dng khong 90% ca ng cong chy nh nht ca n.

- Hiu ng ca dng ti trc s c. Tng t nh hiu ng trn, dng ti

trc s c lm cho cu ch nng ln lm gim thi gian nng chy nh nht,

nh hng n c tnh TC ca cu ch.

vic phi hp c n gin, t chnh xc cao khi c tnh n cc

yu t nu trn th khi thc hin phi hp, cn phi t yu cu thi gian ct ti a

ca dy ch xa ngun s khng ln hn 75% ca thi gian nng chy ti thiu ca

dy ch gn ngun. H s 75% ni trn b cho nhng yu t gy nh hng n

c tnh TC ca cu ch. Phng php phi hp dng c tuyn TC c chnh xc

cao v hin nay n c s dng xy dng cc phn mm phi hp bo v trong

li phn phi.

1.3 PHI HP BO V GIA RLE QU DNG V CU CH

1.3.1 Rle c c tnh thi gian ph thuc

Rle lm vic vi thi gian xc nh no khi dng in vt qu gi tr

khi ng, c tnh ny gi l ph thuc. Rle c c tnh ph thuc khi ng khi

dng din vt qu gi tr khi ng, thi gian tc ng ca rle ph thuc vo tr

s dng in qua rle. Thi gian lm vic gim khi dng in tng cao. c tnh

thi gian ph thuc ca rle dng c cc dng sau:

c tnh thi gian ph thuc c gii

hn nh nht ( dc chun SIT).

10

20

50

4,03,0

2,0

1,0

0,5

0,2

0,1

1

1

2

3

2 3 110 204

Loi ny lm vic theo c tnh

dng in thi gian ph thuc cc gi tr

ca dng in ngn mch nh, khi dng

in ngn mch nh hn 10 ln dng nh

mc th rle lm vic theo c tnh ph

thuc. Khi dng ngn mch ln hn t 10

n 20 ln dng nh mc th c tnh l

ng thng, ngha l c tnh thi gian

gii hn. Loi ny c dng rng ri

bo v mng phn phi.

Thi

gi

n ta

co

ng s

a

,

- c tnh thi gian rt dc ( VIT) loi

ny c dc nhiu hn loi dc chun,

c tnh ny c tnh chn lc tt hn loi

dc chun.

Boi so Ikd

Hnh 1.3: Cc dng c tnh thi gian ph thuc

V vy loi c tnh ny c dng khi c tnh dc chun khng bo m tnh

chn lc.

- c tnh thi gian cc dc (EIT)

Loi ny cho c tnh dc nhiu hn loi rt dc v dc chun. c tnh ny thch

hp dng bo v my pht, my bin p ng lc, cp, chng qu nhit.

1.3.2 Cc tiu chun c tuyn ca bo v qu dng vi thi gian ph thuc

Hin nay tn ti cc tiu chun c tuyn sau trong bo v Rle : tiu chun

ca U ban k thut in Quc t (IEC), ca Vin k thut in-in t M (IEEE),

ca Vin tiu chun quc gia Hoa K (ANSI) Trong cc rle s hin nay thng

c mt vi loi tiu chun c tnh la chn, nhng tiu chun hay c dng

nht l ca y ban k thut in Quc t (IEC).

* Tiu chun (IEC 255-3)

Tiu chun ny c s dng trong cc rle s hin i v tiu chun ny l

duy nht trong nhiu rle qu dng c sn xut ti chu u. N bao gm cc h

c tuyn c dc khc nhau nhng c ba loi chnh hay c s dng l ICE

255-3A; IEC 255-3B v IEC 255-3C. Cng thc xc nh chung cho thi gian tc

ng v tr v ca cc h ng cong nh sau:

ttd = TD [ 1nmK ] ; ttv = TD [ 12

1

mK ] (1.2)

Trong : tt; ttv l thi gian tc ng v thi gian tr v ca Rle

m = D

NM

II l bi s dng ngn mch

K , , n c tnh theo cc cng thc di y i vi tng loi c tuyn

c dc khc nhau

1K

- ng cong dc chun (SIT) IEC 255-3A

ttd = TD [ 114,0

02,0 m ] ; ttv = - TD [ 108,1

2 m ] (1.3)

- ng cong rt dc (VIT) IEC 255-3B

ttd = TD [ 15,13m ] ; ttv = - TD [ 1

5,132 m ] (1.4)

- ng cong cc k dc (EIT) IEC 255-3C

ttd = TD [ 1802 m ] ; ttv = - TD [ 1

802 m ] (1.5)

iu cn lu l h s thi gian t TD (TMS) trong cc cng thc trn

thng ch dao ng t 0,05 n 3.

1.3.3 Phi hp bo v gia cu ch v rle qu dng

mt h thng in vn hnh c n nh v tin cy th cc thit b bo v

cn phn bit ng ngn mch t im s dng in n ngun in. Cc gi tr t

phi c tnh ton cho mi rle v cc ng c tnh ca tt c cc thit b bo v

trn cng mt nhnh c so snh bo m s phn bit. Qu trnh trn gi l s

phi hp rle v cc thit b bo v khc.

Nh cp trn, c tnh thi gian dng in ca rle dng c c

tnh ph thuc c dng chun, rt dc v cc dc, mi dng c nhng thun li

khi ng dng cho tng s c th.

Chng hn vi s phi hp bo v sau: Cu ch 400A

1MVA 2000/1A Dng Nm 30KA

3300/415V MCCB 400A

Rle MCGG32 50-200%

10,0

1,0

0,42

0,1

0,011,000

t

10,000 30,000 100,000

MCCB

Rle MCGG32

vic phi hp bo v c bo

m th ta cn tun th cc nguyn tc

chn lc sau y:

- Xc nh dng in qua rle:

Dng in t vo rle c chn sao cho

khng nh hn dng in khi y ti.

Dng in y ti c xc nh t cng

sut ca my bin p.

I = 3U

S

Hnh 1.4: S phi hp c tuyn lm vic

Gi thit ban u chn tr s t rle l 100% dng nh mc ca BI

- Xc nh c tnh cu ch v my ct MCCB. V cc c tnh dng in -

thi gian ca cu ch v my ct.

- La chn c tnh rle: Khi tnh cc gi tr t rle bo v phn bit chn

lc gia cu ch v cc thit b khc cn da vo cc c tnh ph thuc v dc, u

tin thng chn ng c tnh rle c dng cc dc. T cc ng c tnh ca cu

ch, my ct MCCB v rle, kt hp vi dng ngn mch ta xc nh c thi gian tc

ng ca cu ch, my ct v rle (tcc, tmc, trl).

Nu t s bin dng l T

S

II v gi tr t dng 100% th bi s dng ngn

mch s l:

m = S

NM

II

T ng c tnh cc dc ti tr s m v TD = 1 ta tm c thi gian tc

ng ca rle theo cng thc (1.4):

ttd = TD [ 1802 m ]

Nu thi gian ttd tm c nh hn thi gian tc ng ca rle m ta xc nh

c trn th ng cong cc dc ny l khng dng c cho trng hp ny. Bc

tip theo l chuyn sang c tnh rt dc ca rle, thi gian tc ng tt ca rle c

tnh t phng trnh (1.3) ng vi TD v m bit. t c thi gian hat ng

ca rle theo yu cu l tr, th tnh gi tr t TD = tr/tt . Trng hp ny nu cng

khng chn c th ta cn c mt s thay i bng cch chn gi tr dng t ca rle

ln hn. Chng hn vi gi tr dng t khong 140% dng nh mc ca bin dng v

vi t s bin dng bit cng vi gi tr ban u ca TD = 1 ta tm c tr s ca m v

thi gian lm vic ttd ca rle. c c thi gian hot ng theo yu cu tr th gi tr t

TD s phi l tr/tt . Khi rle c gi tr dng t ln hn v vi TD = tr/tt ta thay i dng

ngn mch (thay i tr s ca m) s dng cng thc (1.3) ta s nhn c cc tr s ca ttd

tng ng vi cc gi tr ca dng ngn mch khc nhau. Cc im trn khi c v

theo cc ng c tnh cu ch v MCCB s xc nh c ng c tnh rt dc ca

rle cho ta mt s phi hp c chn lc thch hp dng ngn mch cc i. Trn thc

t khi s dng rle kt hp vi cu ch th cn rle d phng cho cu ch, ch khng

nn lm ngc li v vi cc dng ngn mch ln, cu ch thng tc ng rt nhanh

do n thng ct trc rle m n c nhim v phi d phng. phn cp thi

gian gia cu ch v rle s l:

t = (0,3 + 0,1)tcc + 0,15 = 0,4tcc + 0,15 (1.6) 1.4 PHI HP BO V GIA RLE V RLE

Hin nay, ngi ta c xu hng s dng rle qu dng vi c tnh ph

thuc nh mt bo v thng thng thay th cho rle vi c tnh c lp, v n

khng tng ng vi kh nng chu dng ca i tng c bo v. iu ny c

ngha: khi dng ngn mch thay i trong mt phm vi rng th rle li ct s c

vi mt thi gian nh nhau. Vi dng ngn mch ln qua i tng bo v th rle

vn cha tc ng, trong khi vi dng ngn mch nh rle li ct qu sm gy gin

on ch lm vic lin tc ca i tng bo v. Do vy, phn ny ch cp

n rle qu dng vi c tnh ph thuc.

1.4.1 phn cp thi gian vi c tnh ph thuc

phn cp v thi gian vi c tnh ph thuc gia 2 rle lin k c xc

nh nh sau:

t = dpqtnMCnsrnBIsr ttttEtEE +++++ )1()1( 100100 (1.7)

Trong : Esr l sai s thi gian tng i ca rle qu dng cp ang xt v

cp bo v trc, thng c gi tr t 3% - 5%. Sai s o lng ca 2 rle lin k

nh hng n c tuyn thi gian dng, sai s ny ph thuc vo ln ca dng

tc ng.

- tMC(n-1) l thi gian ct ca my ct cp bo v trc(v pha ti) c gi tr

bng 0,1 - 0,2s i vi my ct khng kh; bng 0,06 - 0,08s i vi my ct chn

khng v bng 0,04 - 0,05 i vi my ct kh SF6. Thi gian ny c xc nh

bi thi gian truyn tn hiu ct t rle ti my ct, thi gian kch hot cun ct,

thi gian dp h quang.

- tqt l thi gian sai s do

qun tnh khin cho rle vn trng

thi tc ng mc d ngn mch

b ct c gi tr thng nh hn

0,05s. Sai s ny c hiu l khi

dng ngn mch u vo rle b

ct, n vn c th tc ng thm

mt thi gian na do nng lng

in cn duy tr cc mch dung

khng bn trong rle.

RleA

RleB

200 400 2878(I ) IN2 NM

D C B A

N2 N1

Hnh 1.5: Xc nh phn cp v thi gian

- tdpl thi gian d phng. - EBI l sai s o lng ca bin dng.

Tuy nhin cn lu sai s ca cc rle v BI l mt i lng thay i, ph thuc

dng ngn mch qua rle, tc l v tr im ngn mch. V vy, xc nh phn cp v

thi gian s ph thuc dng ngn mch ti cc v tr chuyn tip cp bo v.

1.4.2 Nguyn tc phi hp gia 2 rle lin k

Hnh 1.6: Nguyn tc phi hp cc bo v qu dng lin k

tAB

A

I> m (I ) I0 N2 NM

D ZCD C 2 ZBC B 3 ZABA Znguon

2N2

3N1

tB

C

I> I>

TBC

N3N4

phi hp tt cc rle qu d

phi thc hin cc nguyn tc c bn saung lin k vi c tuyn ph thuc, ta cn

:

- c tuyn bo v phi nm di v c nghing cng gn vi c tuyn

chu dng an ton ca i tng bo v cng tt.

- S dng cc bo v lin k c dc ca c tuyn gn ging nhau.

- Cc bo v cng xa ngun cng c gi tr t dng nh hn so vi cc bo

v gn ngun.

- Chn thi gian t phi thc hin sao cho rle s tc ng vi thi gian nh

nht ti im cui ng dy.

- Khi c ngn mch ti cc im chuyn tip gia 2 bo v lin k, thi gian tc

ng ca 2 bo v ln cn cn phi khc bit nhau mt khong thi gian t nht l bng

phn cp thi gian xc nh trong ch cc i ca h thng.

- Cc c tuyn c xc nh t bo v xa ngun nht n bo v gn ngun nht.

T c tuyn bo v chung ca cc cp ta thy, c xu hng gim thi gian

tc ng ca bo v i vi cc s c gn ngun, nhng vn bo m phn cp

thi gian ti cc im c th xy ra tc ng nhm.

WX