GIAO TRINH ROLE ÐH 2011-1 ban

7/29/2019 GIAO TRINH ROLE H 2011-1 ban

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TP ON IN LC VIT NAMTRNG I HC IN LC

GIO TRNH I HC

BO V RLE

TRONG H THNG IN

Ti liu tham kho ni b dng trong

Khoa H thng in

TRNG I HC IN LC

CC TC GI

THs. Nguyn Vn t Khoa H thng inTS. Nguyn ng Ton Khoa H thng in

H ni 2010


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LI TA

Gio trnh Bo v rle trong h thng in c dng ging dy cho sinh vinngnh H thng in trng i hc in lc v lm ti liu tham kho cho nhng ngi lmcng tc k thut v vn hnh cc thit b bo v trong h thng in.

Gio trnh a ra mt s vn c bn ca k thut bo v h thng in bng rle, ccnguyn tc tc ng v cch thc hin cc loi bo v thng gp. i vi mi phn t trongh thng in, gio trnh trnh by tm tt cc ch lm vic, tnh trng h hng v lm vickhng bnh thng, m t nguyn l lm vic v chc nng cc phn t chnh trong s bov.

Gio trnh gii thiu v xem xt vic bo v cc phn t chnh trong h thng in baogm: ng dy truyn ti, my pht in, my bin p, thanh gp, ng c in, t in,khng in, cp in.

Ton b cun sch chia lm 8 chng. y l ln ti bn th nht, cc tc gi cgng chnh sa nhng thiu st ca ln xut bn trc v cp nht thm mt s kin thc mi,nhng chc chn khng th trnh khi nhng thiu st. Nhng nhn xt v gp ca bn c

xin gi cho Khoa H thng inTrng i hc in lc 235 Hong Quc Vit - H Ni.Email.

Tel :


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LI CM N


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MC LC

LI TA ...................................................................................................................................... iii

LI CM N............................................................................................................................... iv

MC LC ......................................................................................................................................v

DANH MC HNH V ................................................................................................................ ixDANH MC BNG.....................................................................................................................xv

PHN I: CC NGUYN L BO V........................................................................................xvi

CHNG 1: KHI NIM CHUNG ........................................................................1

1.1 NHIM V BO V R LE................................................................................................... 1

1.2 YU CU CA BO V R LE............................................................................................ 2

1.2.1 Tnh tin cy ....................................................................................................................... 2

1.2.2 Tnh chn lc..................................................................................................................... 2

1.2.3 Tnh tc ng nhanh .......................................................................................................... 31.2.4 nhy............................................................................................................................. 4

1.2.5 Tnh kinh t ....................................................................................................................... 4

1.3 CC B PHN CA H THNG BO V RLE................................................................ 4

1.4 MY BIN DNG IN (BI, CT).......................................................................................... 7

1.4.1 Khi nim v my bin dng in ...................................................................................... 7

1.4.2 S thay th v k hiu my bin dng in.................................................................... 7

1.4.3 Sai s ca my bin dng v yu cu v chnh xc ........................................................ 8

1.4.4 Tnh ton ph ti ca my bin dng in .........................................................................10

1.4.5 Ch h mch th cp ca my bin dng in ..............................................................10

1.4.6 Cc s ni my bin dng in.....................................................................................11

1.5 MY BIN IN P (BU, VT, PT).......................................................................................14

1.5.1 Khi nim v my bin in p .........................................................................................14

1.5.2 Sai s ca my bin in p v yu cu v chnh xc ....................................................15

1.5.3 Cc s ni my bin in p.........................................................................................16

1.6 NGUN IN THAO TC ...................................................................................................18

1.6.1 Ngun in thao tc mt chiu..........................................................................................18

1.6.2 Ngun in thao tc xoay chiu ........................................................................................191.7 KNH THNG TIN TRUYN TN HIU .............................................................................21

1.7.1 Cc loi knh truyn tn hiu.............................................................................................21

1.7.2 Yu cu i vi knh truyn tn hiu.................................................................................23

1.7.3 Mi trng truyn tn hiu v nhiu...................................................................................23

1.8 THNG TIN CN THIT PHC V TNH TON BO V RLE.....................................25

1.8.1 Nguyn l lng dng trong mc ch bo v ...............................................................25

1.8.2 Tnh ton ngn mch/s c ...............................................................................................27


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1.9 CU HI N TP .................................................................................................................28

CHNG 2: CC K THUT CH TO RLE ...............................................29

2.1 LCH S PHT TRIN CA RLE .....................................................................................29

2.2 PHN LOI RLE ................................................................................................................30

2.3 RLE IN C .....................................................................................................................34

2.3.1 Rle dng in kiu in t ..............................................................................................342.4 RLE DNG IN KIU CM NG ..................................................................................37

2.4.1 Nguyn tc tc ng .........................................................................................................37

2.4.2 Lnh vc ng dng: ..........................................................................................................39

2.4.3 Rle in p .....................................................................................................................39

2.4.4 Rle thi gian...................................................................................................................40

2.4.5 Rle trung gian .................................................................................................................40

2.4.6 Rle tn hiu .....................................................................................................................41

2.5 RLE IN T.....................................................................................................................41

2.6 RLE K THUT S ...........................................................................................................44

2.7 CU HI N TP .................................................................................................................46

CHNG 3: CC NGUYN L BO V R LE H THNG IN .............47

3.1 BO V QU DNG IN ..................................................................................................47

3.1.1 Nguyn tc tc ng .........................................................................................................47

3.1.2 Bo v dng in cc i. .................................................................................................47

3.1.3 Bo v dng in ct nhanh ..............................................................................................49

3.1.4 Bo v dng in cc i c b kim tra in p ...............................................................49

3.1.5 Bo v dng in ba cp ...................................................................................................503.1.6 nh gi bo v qu dng in .........................................................................................52

3.2 BO V QU DNG IN C NH HNG CNG SUT............................................53

3.2.1 Nguyn tc tc ng .........................................................................................................53

3.2.2 Phn t nh hng cng sut ...........................................................................................54

3.2.3 La chn thi gian cho bo v dng in c nh hng cng sut....................................54

3.2.4 La chn dng in khi ng..........................................................................................55

3.2.5 Bo v dng in c hng ba cp ....................................................................................56

3.2.6 nh gi bo v dng in c nh hng cng sut .........................................................56

3.3 NGUYN L BO V KHONG CCH .............................................................................57

3.3.1 Nguyn tc tc ng .........................................................................................................57

3.3.2 Cc c tnh khi ng ca bo v khong cch ................................................................59

3.3.3 Nguyn tc thc hin rle khong cch .............................................................................60

3.3.4 La chn gi tr khi ng ................................................................................................60

3.3.5 Nhng yu t lm sai lch n s lm vic ca rle khong cch ......................................61

3.3.6 nh gi v bo v khong cch .......................................................................................62


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3.4 BO V SO LCH.................................................................................................................62

3.4.1 So lch dng in .............................................................................................................62

3.4.2 So snh pha ca dng in ................................................................................................65

3.4.3 nh gi v bo v so lch................................................................................................66

3.5 CU HI N TP .................................................................................................................66

PHN II: BO V CC PHN T TRONG H THNG IN ................................................67CHNG 4: BO V CC NG DY TI IN ........................................68

4.1 KHI NIM CHUNG.............................................................................................................68

4.2 BO V QU DNG IN ..................................................................................................69

4.2.1 Bo v qu dng in ct nhanh ........................................................................................69

4.2.2 Bo v qu dng in c thi gian ....................................................................................70

4.2.3 Bo v qu dng c kho in p thp ..............................................................................71

4.2.4 Bo v qu dng in c hng ........................................................................................72

4.2.5 Bo v qu dng ct nhanh c hng ................................................................................74

4.3 BO V SO LCH DC NG DY TI IN ..............................................................75

4.3.1 Bo v so lch dng in c hm......................................................................................75

4.3.2 Bo v so lch dng dy dn ph ......................................................................................77

4.3.3 Bo v so snh pha dng in ...........................................................................................78

4.4 BO V KHONG CCH ...................................................................................................81

4.4.1 Chn gi tr khi ng v thi gian lm vic r le khong cch .........................................81

4.4.2 Bo v khong cch cc ng dy c t t in b dc :.............................................83

4.5 BO V SO SNH HNG .................................................................................................85

4.6 NGUYN L BO CHNG CHM T.............................................................................874.6.1 Nguyn tc tc ng .........................................................................................................87

4.6.2 Bo v qu dng in th t khng ...................................................................................88

4.6.3 Bo v qu dng in th t khng c hng....................................................................88

4.6.4 Bo v chng chm t chp chn .................................................................................91

4.7 CU HI N TP .................................................................................................................92

CHNG 5: BO V MY PHT IN NG B .........................................93

5.1 CC DNG H HNG V TNH TRNG LM VIC KHNG BNH THNG CA

MY PHT IN .......................................................................................................................93

5.2 BO V CHNG CHM T CUN DY STATO ...........................................................94

5.3 BO V CHNG NGN MCH GIA CC PHA ..............................................................98

5.3.1 Bo v so lch hm...........................................................................................................99

5.3.2 Bo v khong cch ........................................................................................................101

5.3.3 Bo v qu dng in .....................................................................................................102

5.4 BO V CHNG CHM CHP CC VNG DY TRONG MT PHA CA CUN

STATO.......................................................................................................................................103


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5.5 BO V CHNG CHM T CUN DY R TO ..........................................................105

5.6 BO V CHNG DNG IN TH T NGHCH............................................................109

5.7 BO V CHNG MT KCH T.......................................................................................110

5.8 BO V CHNG QU TI CHO CUN DY STATO V RTO MY PHT IN ....112

5.9 BO V CHNG QU IN P........................................................................................113

5.10 BO V CHNG TN S GIM THP ..........................................................................1145.11 BO V CHNG LUNG CNG SUT NGC ...........................................................115

5.12 CU HI N TP .............................................................................................................116

CHNG 6: BO V MY BIN P ................................................................117

6.1 CC H HNG V NHNG LOI BO V THNG DNG.......................................117

6.2 BO V SO LCH DC......................................................................................................117

6.3 BO V QU DNG IN ................................................................................................119

6.4 BO V KHONG CCH ..................................................................................................120

6.5 BO V BNG R LE KH (BUCHHOLZ)........................................................................121

6.6 BO V CHNG CHM T CA MY BIN P .........................................................122

6.7 BO V QU NHIT CHO MY BIN P .......................................................................123

6.8 LA CHN PHNG THC BO V MY BIN P ....................................................126

6.9 CU HI N TP ...............................................................................................................127

CHNG 7: BO V CC H THNG THANH GP ...................................115

7.1 CC DNG H HNG .......................................................................................................115

7.1.1 Nhng trng hp khng cn t bo v ring................................................................115

7.1.2 Nhng trng hp cn t bo v ring cho thanh gp....................................................116

7.2 CC LOI S THANH GP ........................................................................................1167.2.1 S mt h thng thanh gp.........................................................................................116

7.2.2 S hai h thng thanh gp c mt my ct trn mch .................................................117

7.2.3 S thanh gp mi mch in c ni vi h thng thanh gp qua hai my ct in...119

7.3 BO V SO LCH TON PHN THANH GP .................................................................120

7.3.1 Nhng c im khi thc hin bo v so lch ton phn thanh gp..................................120

7.3.2 Bo v so lch dng in c hm....................................................................................122

7.3.3 Bo v so lch thanh gp dng r le tng tr cao ............................................................124

7.3.4 Bo v thanh gp dng nguyn l so snh pha dng in ................................................126

7.4 BO V SO LCH KHNG TON PHN THANH GP ..................................................127


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DANH MC HNH V

Hnh v 1-1: V d v tnh chn lc ca bo v rle ........................................................................... 3

Hnh v 1-2: Cu trc tng qut ca h thng bo v .......................................................................... 5

Hnh v 1-3: V d v mt cu trc ca h thng bo v ..................................................................... 6

Hnh v 1-4: S cu trc ca h thng bo v c d phng tng cng tin cy...................... 6Hnh v 1-5: My bin dng cao p, h p v s nguyn l ca my bin dng.............................. 7

Hnh v 1-6: Sai s ca BI v s thay th ca BI dng trong bo v ............................................... 9

Hnh v 1-7: Ni tip hai my bin dng...........................................................................................10

Hnh v 1-8: ng cong t ho (a) v quan h ca dng in s cp iS, t thng F,.........................11

Hnh v 1-9: Cc ni BI v rle theo s hnh sao ..........................................................................11

Hnh v 1-10: S ni mt rle vo hiu dng in hai pha v s vc t ca dng in th cp

qua rle khi ngn mch 2 pha v ba pha ............................................................................................12

Hnh v 1-11: Cc s b lc dng in th t khng: a) s nguyn l, b) b lc dng ba my

bin dng, c) b lc mt my bin dng dng cho ng dy trn khng, d) b lc mt my bin dng

dng cho ng dy cp ngm ..........................................................................................................13

Hnh v 1-12: Cc s b lc dng in th t nghch LI2: a) S cu trc, b) mch in, c) th

vc t i vi thnh phn th t thun, d) th vc t thnh phn th t nghch ..............................14

Hnh v 1-13: My bin in p cao p, h p v s nguyn l ca my bin in p ....................15

Hnh v 1-14: S ni cc BU theo hnh sao: a ni vo in p dy, b) ni vo in p pha, c) in

p ba pha v dy trung tnh ca HT ................................................................................................16

Hnh v 1-15: S ni cc BU theo hnh V/V.................................................................................16

Hnh v 1-16: Cc s b lc th t khng, a) cun tam gic h, b) b lc in p th t khng trung tnh my pht in ...................................................................................................................17

Hnh v 1-17: S nguyn l ca b lc in p th t nghch........................................................18

Hnh v 1-18: S dng rle dng in c c tnh thi gian ph thuc c gii hn lm vic vi

dng in thao tc mt chiu .............................................................................................................19

Hnh v 1-19: S bo v dng in dng ngun thao tc xoay chiu theo phng php kh ni tt

cun ct ca my ct .........................................................................................................................20

Hnh v 1-20: S bo v dng in ni vo dng in thao tc xoay chiu qua bin dng bo ho

trung gian .........................................................................................................................................20

Hnh v 1-21: S b cung cp lin hp .........................................................................................21

Hnh v 1-22: S ngun cung cp bng b t np sn ...................................................................21

Hnh v 1-23: Lin h gia cc thit b lm vic vi knh truyn tn hiu ..........................................22

Hnh v 1-24: Nguyn l so snh bin hai i lng u vo ........................................................26

Hnh v 1-25: Nguyn l so snh pha (a) v biu so snh hai tn hiu u vo hnh sin lch pha

nhau (b) ............................................................................................................................................27

Hnh v 2-1: So snh gia rle s v rle thng thng .....................................................................30


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Hnh v 2-2: Phn loi rle theo cc i lng u vo .....................................................................31

Hnh v 2-3: Cc loi s ca h thng bo v rle ........................................................................32

Hnh v 2-4: Mt s loi rle in t: a) Rle in t c phn ng ng m, b) C phn ng quay,

c) phn chuyn ng tnh tin............................................................................................................35

Hnh v 2-5: Quan h gia tr s tc thi ca m men quay Mt v cc thnh phn ca n vi thi gian

i vi rle dng in in t ...........................................................................................................36Hnh v 2-6: Vng ngn mch ca rle v th vc t. ....................................................................36

Hnh v 2-7: Rle dng in: a) c vng cm ng ngn mch, b) v th vc t. .............................38

Hnh v 2-8: R le thi gian ..............................................................................................................40

Hnh v 2-9: Cc s ni r le trung gian: a)S ni cc rle RG song song, b) ni tip, c) song

song c t gi bng cun dy ni tip ...............................................................................................41

Hnh v 2-10: S ni dy ca rle tn hiu, a) ni tip, b) song song .............................................41

Hnh v 2-11: Rle dng in chnh lu: a) S nguyn l, b) dng in chnh lu [I]....................42

Hnh v 2-12: Cc s san bng dng in chnh lu, .....................................................................43

Hnh v 2-13: S so snh dng in I vi i lng chun Ich ......................................................44Hnh v 2-14: S khi ca r le s................................................................................................45

Hnh v 2-15: S t kim tra cc khi chc nng trong rle s .....................................................46

Hnh v 3-1: Th d v cch tnh dng in khi ng ca bo v dng in cc i a) S nguyn

l, b) Chn dng in khi ng .......................................................................................................48

Hnh v 3-2: Bo v qu dng in ct nhanh, a) S nguyn l, b) Cch chn dng in khi ng

.........................................................................................................................................................49

Hnh v 3-3: S nguyn l ca bo v dng in cc i c b phn kim tra in p. ..................50

Hnh v 3-4: S nguyn l ca bo v dng ba cp. ......................................................................51

Hnh v 3-5: Tnh dng in v thi gian tc ng ca bo v dng ba cp........................................52

Hnh v 3-6: Bo v qu dng in c hng a) Mch vng, b) ng dy song song, c) ng dy

c hai ngun cung cp, ......................................................................................................................53

Hnh v 3-7: Bo v qu dng in c hng: a) S nguyn l bo v qu dng, b) c tnh pha

ca b phn nh hng cng sut.....................................................................................................54

Hnh v 3-8: Phi hp thi gian tc ng ca bo v qu dng in c hng vi thanh gp c nhiu

mch ng dy................................................................................................................................55

Hnh v 3-9: Cc cu hnh li in phc tp bo v qu dng c hng khng m bo tnh chn lc:

a) Mng vng c nhiu ngun cung cp. b) Mng vng c mt ngun cung cp khi c lin h ngangkhng c ngun (ng dy BD)......................................................................................................57

Hnh v 3-10: Nguyn l o tng tr, a) S li in; b) Vng bin thin ca tng tr ph ti;

c)Tng tr o trong iu kin s c; d) c tnh khi ng ca b phn khong cch........................58

Hnh v 3-11: Cc c tuyn tng tr khi ng thng gp: a) Tng tr khng hng (ZK=const); b)

Tng tr c hng (vng trn qua gc to ); c) Vng trn lch tm; d) Hnh thu knh, e,g) Hnh

a gic; h) 7SA513..........................................................................................................................59


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Hnh v 3-12: S phi hp tng tr khi ng v c tnh thi gian gia ba vng ca bo v

khong cch. .....................................................................................................................................60

Hnh v 3-13: S phn b dng in trn cc nhnh ca ng dy mch kp ...................................61

Hnh v 3-14: Bo v so lch dng in a) S nguyn l, b) th vct dng in khi ngn mch

ngoi vng v trong ch bnh thng, c) Khi ngn mch trong vng. ............................................63

Hnh v 3-15: S nguyn l ca bo v so lch c hm b sung bng dng in hi bc hai dngcho bo v my bin p hai dy qun ................................................................................................65

Hnh v 3-16: Bo v so snh pha dng in: a) S nguyn l b) c tnh gc pha bo v. ..........66

Hnh v 4-1: Bo v ct nhanh ng dy c hai ngun cung cp ......................................................69

Hnh v 4-2: c tnh thi gian ca bo v qu dng in, a) c lp, b) Ph thuc. .........................70

Hnh v 4-3: Phi hp c tuyn thi gian ca bo v qu dng in trong li in hnh tia (a) cho

trng hp c tuyn c lp (b) v c tuyn ph thuc (c) .............................................................71

Hnh v 4-4: Bo v qu dng in c kho in p thp ...................................................................71

Hnh v 4-5: Bo v qu dng in c hng: a) ng dy hai mch song song, b) cch chn thi

gian lm vic ca bo v ...................................................................................................................73Hnh v 4-6: Phi hp c tuyn thi gian ca bo v qu dng in c hng trong li in c hai

ngun cung cp .................................................................................................................................74

Hnh v 4-7: Bo v qu dng in ct nhanh khng c hng (a) v c hng (b)...........................75

Hnh v 4-8: Bo v so lch dc c hm, a) S nguyn l, b) th vc t ca dng in lm vic

ILV v dng in hm IH khi c ngn mch ngoi (b) v trong vng (c) ..............................................76

Hnh v 4-9: c tnh lm vic ca bo v so lch c hm (1) v tng quan gia dng in lm vic

Ilv v dng in hm IH khi ngn mch trong vng bo v v ngun cung cp t mt pha (2) ...76

Hnh v 4-10: Bo v so lch dng in c hm, dng dy dn ph ...................................................77

Hnh v 4-11: Cng dng in gim bt dy dn ph trong s bo v so lch dng in...........78

Hnh v 4-12: S khi bo v so snh pha dng in tng pha ring bit ......................................79

Hnh v 4-13: Tn hiu so snh pha dng in cho trng hp ngn mch ngoi vng (a)

v trong vng (b) bo v ...................................................................................................................80

Hnh v 4-14: S dng t hp my bin dng BI nhn in p u ra mt pha U t dng in

3 pha.................................................................................................................................................80

Hnh v 4-15: Phi hp tng tr khi ng v c tnh thi gian gia ba vng tc ng ca bo v

khong cch, a) S li in, b) Phi hp c tnh khi ng v thi gian....................................82

Hnh v 4-16: Phi hp cc vng bo v khong cch trong trng hp t thanh ci cui ng dy cnhiu dy ra ......................................................................................................................................83

Hnh v 4-17: in khng ng dy ph thuc vo dung khng v v tr t t b dc.....................84

Hnh v 4-18: Bo v khong cch trn ng dy c b dc, a) S nguyn l, b) khi b t lm

vic bnh thng, c) khi b t b ni tt .............................................................................................85

Hnh v 4-19: S nguyn l ca bo v theo hng cng sut th t khng ................................86


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Hnh v 4-20: S nguyn l ca bo v so snh hng cng sut th t khng truyn tn hiu cho

php............ ....... ....... ...... ....... ...... ...... ....... ...... ..... ....... ....... ....... ....... ....... ........ ....... ....... ....... ....... ......86

Hnh v 4-21: S bin thin ca dng (a) v p (b) ti ch t bo v trc v sau thi im s c (t =

0)......................................................................................................................................................87

Hnh v 4-22: Phn b dng in s c (in dung) khi c chm t trn cc ng dy khc nhau

trong li in hnh tia c trung tnh khng ni t. (a) Chm t ng dy D3; (b) Chm t ngdy D1..............................................................................................................................................89

Hnh v 4-23: S xc nh gc lch pha 0 gia dng (I0) v p (U0) th t khng......................89

Hnh v 4-24: S nguyn l s dng chung cho ton trm mt b xc nh hng cng sut th t

khng, c i ni trong mch dng in th t khng ca cc ng dy..........................................90

Hnh v 4-25: Mc in tr song song vi cun Petersen tng nhy ca bo v chng chm t

.........................................................................................................................................................91

Hnh v 4-26: Nguyn l ca s bo v chng chm t chp .....................................................92

Hnh v 5-1: Chm t trong cun dy Stato my pht in...............................................................95

Hnh v 5-2: Bo v c hng chng chm t cun dy stato my pht in u trc tip vi thanh

gp in p my pht: a) S nguyn l, b) th vc t...............................................................95

Hnh v 5-3: Phn b thnh phn hi bc ba dc theo cun dy stato my pht in, a) ch bnh

thng; b) khi chm t trung im; c) u cc my pht in. ...................................................96

Hnh v 5-4: S bo v 100% cun dy stato chng chm t theo hi bc 3: a) s nguyn l, b)

th vc t trong ch vn hnh bnh thng, c) khi c chm t gn trung im my pht in...97

Hnh v 5-5: S bo v 100% cun dy stato chng chm t c a thm in p hm 20Hz vo

trung im my pht in..................................................................................................................98

Hnh v 5-6: Ngn mch ba pha trong cun dy stato my pht in ng b, a) s nguyn l, b)phn b sc in ng theo s vng ca cun dy, c) v quan h gia dng s c vi s vng dy b

ngn mch ...................................................................................................................................100

Hnh v 5-7: Bo v so lch dng in c hm cun dy stato my pht ..........................................100

Hnh v 5-8: Bo v so lch dng r le tng tr cao t cho my pht in: a) S nguyn l, b)

Mch in ng tr v phn b in p trong ch lm vic bnh thng, c) Mch in ng tr v

phn b in p khi c ngn mch ngoi v nhm BI2 b bo ho hon ton....................................101

Hnh v 5-9: Bo v khong cch cho b MP-MBA: a) S nguyn l, b) c tnh thi gian......102

Hnh v 5-10: c tuyn khi ng ca r le khong cch dng lm bo v cho my pht in .......102

Hnh v 5-11: Bo v qu dng c kha in p thp lm bo v d phng cho my pht in ........103

Hnh v 5-12: Bo v so lch ngang chng ngn mch gia cc vng dy ca my pht in cng sut

ln: a) S nguyn l, b) c tnh khi ng................................................................................104

Hnh v 5-13: Bo v cun dy my pht in c hai nhnh song song chng chm chp gia cc vng

dy..................................................................................................................................................104

Hnh v 5-14: Chm t trong cun dy roto MP, a) Chm t mt im, b) Hai im..................105


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Hnh v 5-15: Bo v chng chm t mt im trong cun dy roto my pht in dng in p ph

mt chiu: a) S nguyn l, b) Dng in qua r le theo v tr im chm t v khi dng ngun

in ph xoay chiu: c) S nguyn l, d) Dng in qua r le.....................................................105

Hnh v 5-16: S bo v chng chm t cun dy roto my pht in c h thng kch t khng

chi than vi it chnh lu lp trc tip trn thn roto da trn nguyn l o in dn ...................106

Hnh v 5-17: c tnh bin thin ca tng tr i vi t ca mch kch thch Hnh v 5-16 v ctnh tc ng ca r le o in dn chng chm t mch roto my pht in ng b: 1) c

tnh ct, 2) c tnh cnh bo ..........................................................................................................107

Hnh v 5-18: S nguyn l pht hin chm t trong cun dy roto my pht in dng ngun in

ph 1Hz c dng sng ch nht (a) v dng sng t vo b phn o UM i vi cc in tr chm t

khc nhau (b v c) ...........................................................................................................................108

Hnh v 5-19: Bo v chng dng in th t nghch t my pht in, a) s nguyn l, b) c

tnh thi gian ph thuc t l nghch, c) c lp c 2 cp .................................................................109

Hnh v 5-20: Bo v chng mt kch t my pht in, a) Thay i hng cng sut phn khng Q, b)

Thay i tng tr o c cc MF, c) Gii hn thay i ca cng sut MP.............................111

Hnh v 5-21: S bo v chng mt kch thch my pht in s dng r le in khng cc tiu:

a) S nguyn l, b) th vc t, c) Cc dng sng ca cc i lng tng ng ......................111

Hnh v 5-22: Quan h gia mc qu ti v thi gian qu ti cho php ca cc cun dy MP ........113

Hnh v 5-23: S nguyn l bo v chng qu ti cun dy my pht in vi 2 knh o lng c

lp ..................................................................................................................................................113

Hnh v 5-24: Bo v chng qu in p hai cp t my pht in ..............................................114

Hnh v 5-25: Thi gian tch hp cho php vn hnh my pht in tn s cao .............................115

Hnh v 5-26: S nguyn l ca bo v chng cng sut ngc ..................................................116Hnh v 6-1: Cn bng pha v tr s ca dng in th cp trong bo v so lch my bin p 2 v 3

cun dy bng my bin dng trung gian BIG.................................................................................118

Hnh v 6-2: S nguyn l bo v so lch c hm cho my bin p 3 cun dy HM- hm theo thnh

phn hi bc 2 trong dng in t ho MBA....................................................................................118

Hnh v 6-3: S nguyn l (a) v c tnh thi gian (b) ca bo v khong cch t MBA hai

cun dy (hoc MBA t ngu) ........................................................................................................120

Hnh v 6-4: V d v r le kh t cho my bin p ........................................................................122

Hnh v 6-5: Bo v chng chm t c gii hn dng cho my bin p : a) MBA hai cun dy, b)

MBA t ngu..................................................................................................................................122Hnh v 6-6: S ph thuc tng nhit ca du so vi nhit mi trng lm mt v tng

nhit cun dy so vi nhit ca du vo ph ti xc lp..........................................................124

Hnh v 6-7: S bo v qu nhit my bin p ............................................................................126

Hnh v 6-8: Phng thc bo v my bin p hai cun dy cng sut b ........................................126

Hnh v 6-9: Phng thc bo v my bin p ba cun dy cng sut ln ........................................127

Hnh v 6-10: Phng thc bo v my bin p t ngu cng sut ln .............................................127


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Hnh v 7-1: Th d cc s ni in khng cn t bo v thanh gp ring.................................115

Hnh v 7-2: Th d cc s ni in cn bo v ring cho thanh gp ...........................................116

Hnh v 7-3: Cc loi s mt h thng thanh gp........................................................................117

Hnh v 7-4: S hai h thng thanh gp c mt my ct trn mt mch ......................................119

Hnh v 7-5: S hai thanh gp mi mch c ni vi hai h thng thanh gp qua hai my ct in

.......................................................................................................................................................119Hnh v 7-6: S hai h thng thanh gp c ba my ct trn hai mch .........................................119

Hnh v 7-7: S hai h thng thanh gp c bn my ct trn ba mch .........................................120

Hnh v 7-8: S b tr h thng thanh gp theo hnh a gic ......................................................120

Hnh v 7-9: Bo v so lch ton phn ca thanh gp n ...............................................................121

Hnh v 7-10: Bo v so lch ton phn thanh gp c phn on vi cc phn t phn b ln c hai

phn on .......................................................................................................................................121

Hnh v 7-11: S nguyn l so lch dng in c hm bo v thanh gp n ........................122

Hnh v 7-12:c tnh bo v thanh gp dng dng in hm .........................................................123

Hnh v 7-13: S bo v mt h thng thanh gp c phn on ..................................................123Hnh v 7-14: S bo v so lch c hm h thng hai thanh gp .................................................124

Hnh v 7-15: Bo v thanh gp bng r le tng tr cao ................................................................124


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DANH MC BNG

Bng 1-1: Mt s v d v cc t s ca BI ......................................................................................... 8

Bng 1-2: Cp chnh xc ca mt s loi my bin dng in............................................................. 8

Bng 1-3: Gii hn sai s ca BI c cp chnh xc 5P v 10P............................................................. 9

Bng 1-4: Gii hn sai s ca BU dng cho bo v ...........................................................................16

Bng 2-1: Cc k hiu v loi rle ....................................................................................................32

Bng 6-1: Cc loi bo v thng dng cho my bin p.................................................................117


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PHN I: CC NGUYN L BO V


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CHNG 1: KHI NIM CHUNG

1.1 NHIM V BO V R LE

Khi thit k hoc vn hnh bt k mt h thng in (HT) no, chng ta cng umong mun HT phi c vn hnh ch an ton, tin cy, v kinh t nht. Mt HTthng rng ln v qui m, tri di trong khng gian vi nhiu thit b in khc nhau t phn

pht in, truyn ti v phn phi in nng. Do , trong bt c HT no cng c th phtsinh cc h hng v cc tnh trng lm vic khng bnh thng i vi cc phn t trongHT . Nguyn nhn dn n cc h hng, hay s c i rt a dng:

Do cc hin tng thin nhin: nh ging bo, ng t, l lt, ni laDo con ngi: sai st trong tnh ton thit k, sai lm trong cng tc vn hnh, thiu st

trong bo dng thit b in

Cc yu t ngu nhin khc: gi ci cch in, thit b qu c, nhng h hng ngunhin, tnh trng lm vic bt thng ca HT

Cc s c nguy him nht c th xy ra trong HT thng l cc dng ngn mch. Khingn mch, dng in tng cao ti ch s c v trong cc phn t trn ng t ngun nim ngn mch c th gy ra nhng tc ng nhit v c nguy him cho cc phn t n chyqua. H quang ti ch ngn mch nu tn ti lu c th t chy thit b, gy ha hon.

Ngn mch cng lm cho in p ti ch s c v khu vc li in ln cn b gim thp, nhhng n s lm vic bnh thng ca cc h tiu dng in. Trng hp nguy him nht,ngn mch c th dn n mt n nh v tan r hon ton HT.

Cc dng ngn mch thng gp trong HT:

Ngn mch ba pha chim khong 5%Ngn mch hai pha chim khong 10%Ngn mch hai pha ni t chim khong 20%Ngn mch mt pha chim khong 65%

Phn loi h hng theo thit b trong HT, vi t l h hng:

ng dy ti in trn khng chim khong 50%ng dy cp chim khong 10%My ct in chim khong 15%My bin p chim khong 12%My bin dng in, bin in p chim khong 2%Thit b o lng, iu khin, bo v chim khong 3%Cc loi khc chim khong 8%

Ngoi cc loi ngn mch, trong h thng in cn c cc tnh trng lm vic khngbnh thng. Ph bin nht l hin tng qu ti, lc dng in ti tng, lm tng nhit ca cc phn dn in. Nu tnh trng qu ti ko di, lm cho thit b in b pht nng qugii hn cho php, lm cho cch in ca chng b gi ci v i khi b ph hng dn n ccs c nguy him nh ngn mch. Chnh v vy m trong khi tnh ton thit k v vn hnh


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HT, ngi ta cng rt phi quan tm n cc tnh trng lm vic khng bnh thng, v nchnh l cc nguyn nhn dn n cc s c nguy him.

Do , nhim v ca cc thit b bo v rle l pht hin v nhanh chng loi tr phnt b s c ra khi h thng in nhm ngn chn v hn ch n mc thp nht nhng huqu tai hi ca s c. Ngoi ra, thit b bo v cn ghi nhn v pht hin nhng tnh trng lmvic khng bnh thng ca cc phn t trong HT. Tu mc quan trng ca thit b inm bo v rle c th tc ng i bo tn hiu hoc ct my ct in.

Thit b t ng c dng ph bin nht bo v cc HT hin i l cc rle. Ngynay, khi nim rle thng dng ch mt t hp thit b thc hin mt hoc mt nhmchc nng bo v v t ng ha HT, tha mn nhng yu cu k thut ra i vi nhimv bo v cho tng phn t c th cng nh cho ton b h thng.

1.2 YU CU CA BO V R LE

1.2.1 Tnh tin cy

L tnh nng m bo cho thit b bo v lm vic ng, chc chn. Cn phn bit haikhi nim sau:

tin cy khi tc ng: l mc chc chn rle hoc h thng bo v rle s tc ngng. Ni cch khc, tin cy khi tc ng l kh nng bo v lm vic ng khi c sc xy ra trong phm vi c xc nh trong nhim v bo v.

tin cy khng tc ng: l mc chc chn rng rle hoc h thng rle s khnglm vic sai. Ni cch khc, tin cy khng tc ng l kh nng trnh lm vic nhm ch vn hnh bnh thng hoc s c xy ra ngoi phm vi bo v c quinh.

Trn thc t tin cy tc ng c th c kim tra tng i d dng bng tnh ton

thc nghim, cn tin cy khng tc ng rt kh kim tra v tp hp nhng trng thi vnhnh v tnh hung bt thng c th dn n tc ng sai ca bo v khng th lng trcc.

nng cao tin cy nn s dng rle v h thng rle c kt cu n gin, chcchn, c th thch qua thc t s dng v cng cn tng cng mc d phng trongh thng bo v. Qua s liu thng k vn hnh cho thy, h thng bo v trong cc h thngin hin i c xc sut lm vic tin cy khong (95 99)%.

1.2.2 Tnh chn lc

L kh nng ca bo v c th pht hin v loi tr ng phn t b s c ra khi h

thng in. Xt v d i vi mng in cho Hnh v 1-1.Khi ngn mch ti im N1 trn ng dy BC, m bo tnh chn lc th bo vphi ct my ct 5 u ng dy b h hng BC. Nh vy tt c cc h tiu th in(tr nhng h ni vo thanh gp C) s tip tc lm vic bnh thng sau khi my ct 5.


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Hnh v 1-1: V d v tnh chn lc ca bo v rle

Khi ngn mch ti im N2, bo m tnh chn lc th bo v cn phi ct cc myct 1 v 2 hai u ng dy b h hng v vic cung cp in cho trm B vn cduy tr.

Theo nguyn l lm vic, tnh chn lc ca cc bo v c phn ra:Bo v c tnh chn lc tuyt i: l nhng bo v ch lm nhim v khi s c xy ra

trong mt phm vi hon ton xc nh, khng lm nhim v d phng cho bo v t cc phn t ln cn (v d nh bo v so lch dc cho my pht in hoc my bin p(MBA)).

Bo v c tnh chn lc tng i: ngoi nhim v bo v chnh cho i tng cbo v cn c th thc hin chc nng bo v d phng cho phn t ln cn ( v dtrn: Bo v 5 c th lm bo v d phng cho bo v 6). thc hin yu cu v chn lc i vi cc bo v c tnh chn lc tng i, cn

phi c s phi hp gia c tnh lm vic ca cc bo v ln cn nhau trong ton h thngnhm mbo mc lin tc cung cp in cao nht, hn ch n mc thp nht thi gianngng cung cp in.

1.2.3 Tnh tc ng nhanh

Tnh tc ng nhanh ca bo v rle l yu cu quan trng v vic cch ly cng nhanhchng phn t b ngn mch, s cng hn ch c mc ph hoi cc thit b, cng gimc thi gian st p cc h dng in, gim xc sut dn n h hng nng hn v cngnng cao kh nng duy tr n nh s lm vic ca cc my pht in v ton b HT. Tuynhin khi kt hp vi yu cu chn lc, tho mn yu cu tc ng nhanh cn phi s dngnhng loi bo v phc tp v t tin. V vy yu cu tc ng nhanh ch ra tu thuc vonhng iu kin c th ca HT v tnh trng lm vic ca phn t c bo v trong HT.

Bo v rle c gi l tc ng nhanh (c tc cao) nu thi gian tc ng khngvt qu 50ms (2,5 chu k ca dng in tn s 50Hz). Bo v rle c gi l tc ng tcthi nu khng thng qua khu tr (to thi gian) trong tc ng rle. Hai khi nim tc ng

nhanh v tc ng tc thi c dng thay th ln nhau ch cc rle hoc bo v c thigian tc ng khng qu 50ms.

Thi gian ct s c tC gm hai thnh phn: thi gian tc ng ca bo v tBV v thigian tc ng ca my ct tMC : MCBVC ttt

Vi HT hin i, yu cu thi gian loi tr s c rt nh, m bo tnh n nh.i vi cc my ct in c tc cao hin i tMC = (20 60)ms (t 1 3 chu k 50Hz).

Nhng my ct thng thng c tMC 5 chu k (khong 100ms 50Hz). Vy thi gian loitr s c tC khong t 2 8 chu k tn s 50Hz (khong 40160ms) i vi bo v tcng nhanh.


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i vi li in phn phi thng dng cc bo v c chn lc tng i, bo vchnh thng thng c thi gian ct s c khong (0,2 1,5) giy, bo v d phng khong(1,52,0) giy.

1.2.4 nhy

nhy c trng cho kh nng cm nhn s c ca rle hoc h thng bo v.

nhy ca bo v c c trng bng h s nhy Kn l t s ca i lng vt l t vorle khi c s c vi ngng tc ng ca n. S sai khc gia tr s ca i lng vt l tvo rle v ngng tc ng ca n cng ln, rle cng d cm nhn s xut hin ca s c,ngha l rle tc ng cng nhy.

nhy thc t ca bo v ph thuc vo nhiu yu t nh: Ch lm vic ca HT(mc huy ng ngun max hay min), cu hnh ca li in (cc ng dy lm vic songsong, hay n l), dng ngn mch (ba pha, mt pha, ), v tr ca im ngn mch (gnngun, hay xa ngun), . . .

i vi cc bo v chnh thng yu cu phi c h s nhy t 1,52,0 cn i vibo v d phng h s nhy t 1,21,5.

1.2.5 Tnh kinh t

Cc thit b bo v c lp t trong HT khng phi lm vic thng xuyn trongch vn hnh bnh thng, m ch lun lun sn sng ch n nhng bt thng vs c c th xy ra c nhng tc ng chun xc.

i vi cc trang thit b in cao p v siu cao p, chi ph mua sm, lp t thit bbo v thng ch chim mt vi phn trm gi tr ca cng trnh. V vy yu cu v kinh tkhng ra, m bn yu cu k thut trn ng vai tr quyt nh, v nu khng tho mnc cc yu cu ny s dn n hu qu tai hi cho h thng in.

i vi li in trung p v h p, s lng cc phn t cn c bo v rt ln, vyu cu i vi thit b bo v khng cao bng thit b bo v cc nh my in hoc li

truyn ti cao p. V vy cn phi cn nhc tnh kinh t trong la chn thit b bo v sao choc th m bo c cc yu cu k thut v chi ph thp nht.

Nm yu cu trn trong nhiu trng hp mu thun nhau, v d mun c c tnhchn lc v nhy cao cn phi s dng nhng loi bo v phc tp, bo v cng phc tp,cng kh tha mn yu cu v tin cy; hoc nhng yu cu cao v k thut s lm tng chi

ph cho thit b bo v. V vy trong thc t cn dung ha mc tt nht cc yu cu trntrong qu trnh la chn cc thit b ring l cng nh t hp ton b cc thit b bo v, iukhin v t ng trong h thng in.

1.3 CC B PHN CA H THNG BO V RLE

Trong trng hp tng qut gm, mt h thng bo v rle c m t trong Hnh v1-2, bao gm cc b phn chnh nh sau:


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Hnh v 1-2: Cu trc tng qut ca h thng bo v

1 B phn o lng: gm cc my bin dng in (BI hoc l CT), my bin in p (BUhoc l VT), cc thit b o lng khc lm nhim v o lng cc i lng dngin, in p, tn s Cc tn hiu s cp c th c a vo cc b lc cc thnh

phn i xng, hoc cc thit b bin i AC/DC a tn hiu vo h thng cc rle2 B phn phn tch v so snh logic: gm cc rle c nhim v l phn tch v so snh

cc tn hiu a vo vi cc gi tr khi ng cho trc nh gi tnh trng lm vicca HT l bnh thng, khng bnh thng (qu ti) hay l s c. Tng ng vi cc

tnh trng , rle s gi tn hiu n c cu thc hin. i vi mi nguyn tc bo vkhc nhau th s c cc loi rle vi phng php tnh ton khc nhau.3 B phn thc hin: gm cc rle trung gian, my ct (MC) c nhim v thc hin

vic bo tn hiu, hoc ct my ct trong cc trng hp s c4 H thng ngun in mt chiu: c nhim v l cung cp ngun cho h thng cc rle,

cun ct ca MC, chung, n5 Knh thng tin truyn tn hiu: dng truyn tn hiu iu khin, phi hp bo v,

thng tin Trong Hnh v 1-3, tip im ph MCF ca my ct in (hoc ca rle phn nh v tr

ca my ct) c kh nng ct dng in ln ngt mch dng in cung cp cho cun cttrc khi tip im ca rle tr v, m bo cho tip im ca rle khi b chy v phi ngtdng in ln.

Nhng nm trc y s bo v rle thng c t hp t nhiu rle v nhiu thitb ring l, mi phn t hoc nhm phn t thc hin mt chc nng nht nh trong s bo v. Ngy nay mi i tng cn c bo v ch cn dng mt b bo v. tng cng tin cy c th t thm mt b th hai vi tnh nng tng ng nhng hot ng theomt nguyn l khc hoc do nh sn sut khc ch to.

Cc phn t trong h thng in

~BUF

M

/D /C

o lng v x ltn hiu(BI, BU,

AC/DC)

Phn tch, so snhlogic pht hin s

cGm cc loi rle21, 50, 51, 87

Mch iu khincc tn hiu, mch

my ct,

~=

Ngun mt chiu

Hin th v ghi nhs kin


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Hnh v 1-3: V d v mt cu trc ca h thng bo v

Nguyn l d phng ny cn c p dng cho mch my bin dng in v in p,cho ngun in thao tc v cho c cun ct ca my ct in nh Hnh v 1-4.

Hnh v 1-4: S cu trc ca h thng bo v c d phng tng cng tin cy

Thanh gp

BI My ct inMch in c bo v

MCF

CC Ngun KK

RL

BU Cu ch Tn hiu c t

- +

My ct in

MCMC

BI1 BI2

CC CC2 N2

N1

KK

+

+

BV

BV2

CCh1

CCh

BU

Mch c bo v


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1.4 MY BIN DNG IN (BI, CT)

1.4.1 Khi n im v my bin dng in

My bin dng in (BI, CT= Current Transformer) l mt loi thit b in dng bin i dng in ln pha mch s cp v cc dng in th cp tiu chun (1A, hoc 5A)

dng cho mc ch bo v v o lng. ng thi cc my bin dng cn lm nhim v cchly gia mch s cp c dng in ln, in p cao khi mch bo v pha th cp. iu nycho php ch to theo qui chun cc thit b bo v v o lng, cng nh cc thit b t ngkhc.

1.4.2 S thay th v k hiu my bin dng in

i vi mt s thit b o lng v bo v lm vic theo gc lch pha ca dng in cnphi ni ng u cc cun dy s cp v th cp ca my bin dng. Cc u cun dy scp c k hiu S1 v S2, cn cc u cun dy th cp T1 v T2. Cc u cng tn (i khil S1 v T1) i khi c nh du (*) hoc nu trn hnh v khng ghi k hiu th c hiul u cng tn (S1 v T1 hoc S2 v T2) nm cnh nhau. Cc u dy c xc nh theo quytc sau: Chn u S1 ca cun s cp vi qui c l khi gi tr tc thi ca dng in s cpIS i t u S1 n S2 cn dng in th cp IT s i t T2 n T1 (Hnh v 1-5 - a).

Hnh v 1-5: My bin dng cao p, h p v s nguyn l ca my bin dng

Cc u dy ca my bin dng c th c kim tra bng thc nghim. Theo s n gin gm mt Miliampemet c thang o v hai pha v mt b pin hoc c quy nh Hnh


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v 1-5 - b. Nu cc u dy u ng nh hnh v th khi cng tc K ng kim ca mA lchv pha cc dng (+), cn khi cng tc K m th kim s lch v pha cc m (-).

1.4.3 Sai s ca my bin dng v yu cu v chnh xc

Cc cun s cp ca BI thng c mt n hai vng, trong khi cun dy pha th cpca BI thng c nhiu vng dy. Nu b qua tn tht th

I

ST n

II

trong :IT: Dng in pha th cp ca BI.IS: Dng in pha s cp ca BI.nI: T s bin i ca my bin dng.

Cc t s bin i thng c ca BI cho trong bng sau

Bng 1-1: Mt s v d v cc t s ca BI

Dng in 50:5 100:5 200:5 400:5 600:5 1000:5 2000:5

T s 10 20 40 80 120 200 400

Tuy nhin th bao gi cc my bin dng in cng c tn tht, c dng in t ha I .Dng in t ha t l vi tng tr mch ca mch th cp v th sai s ca BI t l vi tngtr th cp ca BI. Cc loi sai s ca BI gm c:

1 Sai s v tr s dng in: bng hiu s gia bin dng in s cp sau khi tnh

i (IS) v dng in th cp IT. sai s % = 100.I

II.n

S

STI

2 Sai s gc i: bng gc lch pha gia vc t dng in s cp v vc t dng in th

cp.3 Sai sphc hp Fi: bng tr s hiu dng ca dng in th cp l tng vi dngin th cp thc t, n bao gm cc sai s v tr s v sai s v gc pha c kt hp xtn nh hng ca cc hi bc cao trong dng in t ho.

Fi% = 100.S

T

STi

I

dtiinT 0

2)(1

trong :Fi%: Sai s phc hp tnh bng %.T: Chu k ca dng in xoay chiu S.

ni: T s bin i ca my bin dng.iT: Gi tr tc thi ca dng in s cp.IS v iS tng ng l gi tr hiu dng v tc thi ca dng in s cp

Cp chnh xc ca my bin dng dng cho o lng v bo v theo Bng 1-2.

Bng 1-2: Cp chnh xc ca mt s loi my bin dng in

Theo tiu chunLnh vc p dng EEC

(Chu u)VCD(c)

ANSI(M)


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Ly chun dng c o ng h mu 0,1 0,1 0,2o chnh xc 0,2 0,2 0,3o m in nng 0,5 0,5 0,6o lng cng nghip i lng U,I,P,Q 1,0 1,0 1,2Mch Ampemet, Volmet, rle qu dng qu p 3,5 3,0 1,2Li t dng cho bo v 5P, 10P 5P, 10P C, T

Cc thit b bo v rle phi lm vic trong iu kin s c vi dng in s cp vtnhiu ln so vi dng in nh mc, tuy vy vn phi m bo chnh xc cn thit.

Tr s dng in s cp m BI cn m bo c chnh xc yu cu c gi ldng in gii hn theo chnh xc.

T s dng in gii hn theo chnh xc v dng in nh mc gi l h s gii hntheo chnh xc.

Cc BI dng cho thit b bo v c cp chnh xc 5P v 10P, sai s cho php v tr s(fi); gc pha (i, pht) v sai s phc hp (Fi%) theo Bng 1-3

Bng 1-3: Gii hn sai s ca BI c cp chnh xc 5P v 10P

Cp chnh xc fi% i, pht Fi%

5P 1 5

10P 360

10

H s gii hn theo chnh xc: 5, 10, 15, 20 v 30

5%iF

10%i

F

Hnh v 1-6: Sai s ca BI v s thay th ca BI dng trong bo v

Thng s ca BI dng trong o lng thng c k hiu theo ph ti nh mc v cp chnh xc, chng hn 15VA; 0,5; cn BI dng trong bo v c k hiu theo ph ti nhmc, cp chnh xc v h s gii hn theo chnh xc, chng hn 10VA, cp 10P10 (s 10sau cng l h s gii hn theo chnh xc). Trn Hnh v 1-6 gii thch sai s v s s thay th ca ca BI dng trong bo v.


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1.4.4 Tnh ton ph ti ca my b in dng in

Trong s bo v, ph ti ca my bin dng in c th c c trng bng cngsut u ra pha th cp Spt(VA) hoc tng tr pha ph ti Zpt (). Tng tr pha th cp caBI gm c in tr ca rle, in tr dy ni ph v in tr tip xc. Tng tr ph ti cngln th cng sut tiu th pha th cp cng cao, v sai s ca bin dng cng ln.

Tpt

T

Tpt I

S

IUZ 2

V d nu BI c cng sut l 10VA, nu dng in danh nh th cp l 5A th ph tipha th cp l: Z5A = 10/5

2=0,4 , nu dng in danh nh pha th cp l 1A th ph tipha th cp l : Z1A = 10/1

2=10

Trong mt s trng hp gim sai s ca bin dng, ngi ta gim in p u racun th cp bng cch ni tip hai cun bin dng c cng t s li vi nhau nh hnh v:

Hnh v 1-7: Ni tip hai my bin dng

Khi ph ti pha th cp s gim xung mt na v c tnh ton nh sau:

22

ZIUU TptT

V ph ti ca mi bin dng l

2Z

I1.

2ZI

IUZ

T

T

T

Tpt

1.4.5 Ch h mch th cp ca my bin dng in

T s thay th ca BI trn Hnh v 1-6 khi mch th cp ca BI b h, nu pha scp c dng in th ton b dng in s cp y s lm nhim v t ho, t cm Bm tng lnt ngt gy bo ho cho mch t nn cc ng cong bin thin theo thi gian ca t cmB v t thng F c dng bng u. Khi dng in s cp qua tr s khng, sc in ng cmng trong cun th cp ca my bin dng c dng nh nhn vi bin rt ln (Hnh v1-8). c bit trong ch s c, khi dng in s cp t bi s ln, sc in ng cm ng

pha th cp c th n hng chc kilvn, rt nguy him cho ngi v thit b bn th cp.V vy khng c h mch pha th cp ca BI trong khi pha s cp c dng inchy qua. Trong trng hp cn thc hin i ni pha th cp khi c dng in chy quacun s cp th phi ni tt cc cc th cp ca BI trc khi tin hnh i ni. Ch lmvic vi cun th cp b ni ngn mch l ch lm vic bnh thng ca my bin dng.

UT1

Z

Uti

UT2IT

IS


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11

, ,T

e B

( )B

I

Hnh v 1-8: ng cong t ho (a) v quan h ca dng in s cp iS, t thng F,

t cm B v sc in ng th cp eT theo thi gian (b)

1.4.6 Cc s ni my bin dng in

1.4.6.1S ni cc BI theo hnh sao y Trong s ny cc bin dng in t trn c ba pha, cun dy ca rle c ni vo

dng in ba pha ton phn (Hnh v 1-9- a). Dy trung tnh (dy v) bo m s lm vicng ca s khi ngn mch chm t. Khi h thng lm vic bnh thng v khi ngnmch khng chm t dng in 0I3 0 v trong dy trung tnh, v nguyn tc, khng cdng in. Khi ngn mch chm t dng in chy trn dy trung tnh l:

cba0 IIII3

S hnh sao hon ton c th lm vic c khi ngn mch mt pha. Tuy nhin, hinnay bo v chng ngn mch mt pha, ngi ta thng dng s hon ho hn c b lcthnh phn th t khng.

a) S hnh sao y b) S hnh sao khuyt

Hnh v 1-9: Cc ni BI v rle theo s hnh sao


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12

1.4.6.2S ni cc BI theo hnh sao khuytCc bin dng in ch t trn hai pha, cun dy ca rle cng ni vo dng in pha

ton phn (Hnh v 1-9-b). Khi khng c thnh phn dng in th t khng, dng in trndy v bng:

cav III hay bv II

Nh vy trong s ny dng in IV tn ti c trong tnh trng lm vic bnh thngv dy v bo m s lm vic bnh thng ca cc bin dng in trong tnh trng ny. Dyv cn bo m s tc ng ng ca bo v khi ngn mch hai pha trong mt pha khngt bin dng in (pha B) v khi ngn mch nhiu pha chm t.

Khi ngn mch mt pha pha khng t bin dng in (pha B Hnh v 1-9 - b), s hnh sao khuyt s khng lm vic, v vy s ny ch dng chng ngn mch nhiu

pha.

1.4.6.3S ni mt rle vo hiu s dng in hai phaS ny cn c gi l s hnh s 8 (Hnh v 1-10), dng in i vo rle l:

caR III

tnh trng lm vic i, hoc ngn mch i xng th dng in i vo rle l:

caR I3I3I .Nh vy, h s s l: 3ks .

S dng mt rle ni vo hiu s dng in hai pha c nhy ph thuc vo dng

ngn mch:k

Rn I

Ik

Hnh v 1-10: S ni mt rle vo hiu dng in hai pha v s vc t ca dng in

th cp qua rle khi ngn mch 2 pha v ba pha

Khi ngn mch ba pha dng in trong rle NT)3(R)3( I3I (Hnh v 1-10), trong NT)3(I l dng in ngn mch ba pha quy i v pha th cp ca bin dng in.

Khi ngn mch hai pha c t bin dng in (AC) NT)2(RAC)2( I3I .Khi ngn mch hai pha, trong mt pha khng t bin dng in (AB hoc BC):

NT)2(

RBC)2(

RAB)2( I3II .

Gi s khi ngn mch 2 pha v 3 pha gi tr dng in ngn mch bng nhau:

NT)2(

NT)3( II ta c: 1:1:2:3k:k:k:k nBC)2(nAB)2(nAC)2(n)3(


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Nh vy hai trong ba trng hp ngn mch hai pha, s c nhy 3 ln b hnkhi ngn mch hai pha. y l khuyt im ca s ni mt rle vo hiu s dng in hai

pha.

1.4.6.4B lc dng in th t khngCc s b lc dng in th t khng c v Hnh v 1-11. lc dng in th

t khng c th cng trc tip dng in th cp ca ba pha ( Hnh v 1-11- b) hoc cng tthng caba pha dng in xoay chiu (Hnh v 1-11-c,d)

3o

Hnh v 1-11: Cc s b lc dng in th t khng: a) s nguyn l, b) b lc dng ba

my bin dng, c) b lc mt my bin dng dng cho ng dy trn khng, d) b lc mtmy bin dng dng cho ng dy cp ngm

i vi s b lc dng in th t khng nh Hnh v 1-11-b thng c dngtrong li in c dng chm t ln. Nhc im ca s ny l c dng khng cn bng u ra ca b lc ln ch lm vic bnh thng do c tnh ca cc BI trong b lc cth khc nhau.

i

o

i

CBAcbaR n

I3

n

IIIIIII

Trong li c dng chm t b (trung tnh cch in hoc ni t qua in khng ln)

dng cc b lc th t khng lm vic theo nguyn l cng t thng ca ba pha dng in scp (Hnh v 1-11-c,d).

Ch : Khi lp bin dng th t khng u cp, dy ni t v cp phi xuyn limch t kh thnh phn t thng do dng in phn b trong t c th chy qua v cpv dy ni t gy nn.

1.4.6.5B lc dng in th t nghch (LI2)S nguyn l ca b lc dng in th t nghch (LI2) nh Hnh v 1-12. Dng in

th cp ca BI pha A l ITA chy qua R1, dng in th cp ca BI pha C l ITC chy qua R2


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v X ni tip nhau. Cc dng in ny gy nn cc thnh phn in p ging tng ng: UR1,UR2, UX.

u ra ca b lc LI2 Hnh v 1-12-b ta c: 2XR1Rnm UUU

trong : X2R2XR UUU Tr s ca cc in tr R1, R2 v cm khng X c chn sao cho trong ch i xng

ta c (Hnh v 1-12-c):UR1 = UR2 v Umn = 0

Khi xut hin dng th t nghch, in p u ra ca b lc Umn c tr s ln (Hnh v1-12-d).

Hnh v 1-12: Cc s b lc dng in th t nghch LI2: a) S cu trc, b) mch in,

c) th vc t i vi thnh phn th t thun, d) th vc t thnh phn th t nghch

1.5 MY BIN IN P (BU, VT, PT)

1.5.1 Khi n im v my bin in p

My bin in p (BU, VT= Voltage Transformer hoc PT= Potential Transformer) lmnhim vbin i in p cao pha s cp xung in p th cp tiu chun 100V hoc 110V dng cho mc ch bo v v o lng, ng thi cch ly cc thit b mch th cp khiin p cao pha s cp.

Cc my bin in p cao p, h p v s nguyn l c trnh by nh Hnh v1-13


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Hnh v 1-13: My bin in p cao p, h p v s nguyn l ca my bin in p

Cch nh du cc u dy ca cc cun s cp v th cp ca BU cng hon tontng t nh i vi cch nh du cc u dy ca BI. Cc u cun dy s cp c k

hiu S1 v S2, cn cc u cun dy th cp T1 v T2. Cc u cng tn (i khi l S1 v T1)i khi c nh du (*) hoc nu trn hnh v khng ghi k hiu th c hiu l u cngtn (S1 v T1 hoc S2 v T2) nm cnh nhau.

1.5.2 Sai s ca my bin in p v yu cu v chnh xc

Cng tng t nh BI, cc BU cng c cc sai s.

1 Sai s v tr s in p c tnh theo cng thc:

%100.U

UUn%F

S

STUU

Trong :FU%: Sai s tnh bng %.nU: T s bin i ca BU, nU=USd/ UTdUS, UT: Gi trtng ng ca in p o c trn cc ca cun s cp v thcp.

2 Sai s gc U: bng gc lch pha gia vc t in p s cp v vc t in p th cp.3 Cc BU c phn loi theo cp chnh xc dng cho bo v c cho bng di:

S1*T1*

S2T2

Ti


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Bng 1-4: Gii hn sai s ca BU dng cho bo v

Cp chnh xc fu (%) u (pht)3P 3 1206P 6 240

Ghi ch: in p thay i trong gii hn (0,051)Umcp (qu in p ln nht chophp). Ph ti thay i trong gii hn (0,251)SPtm vi cos = 0,8.

1.5.3 Cc s ni my bin in p

1.5.3.1S ni cc my bin in p BU theo hnh saoC th dng ba bin in p mt pha hoc mt bin in p ba pha nh hnh v

(a) (b) (c)

RL RL RL RL RL RL RL RL RL

Hnh v 1-14: S ni cc BU theo hnh sao: a ni vo in p dy, b) ni vo in p pha,

c) in p ba pha v dy trung tnh ca HT

S c th cung cp cho rle cc in p dy, cc in p pha v cc in p gia cc

pha v im trung tnh ca h thng in p dy. Trn Hnh v 1-14 in p t vo cc rle:

3

UUU acaba0

;

3

UUU bcbab0

;

3

UUU cbcac0

thc hin s ny cng c th dng my bin p ba pha nm tr.

1.5.3.2S ni cc my bin in p BU theo hnh VS ni my bin in BU theo hnh V (sao khuyt) nh Hnh v 1-15. S c

to thnh bi hai bin in p mt pha ni vo hai in p dy bt k ca mng s cp vc dng rng ri trong cc h thng in p di 35kV khi khng cn phi nhn in p

pha i vi t.

RL RL RL RL RLRL

Hnh v 1-15: S ni cc BU theo hnh V/V


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1.5.3.3S lc in p th t khng (LU0)S c to thnh bi ba bin in p mt pha hoc mt bin in p ba pha nm tr

c hai cun dy th cp, mt cun dy ni hnh sao c trung tnh ni t, mt cun ni hnhtam gic h. in p t vo rle ni vo hai u tam gic hHnh v 1-16 a

cbaR UUUU

=1

( )A B CU

U U Un

=3

O

U

Un

Hnh v 1-16: Cc s b lc th t khng, a) cun tam gic h, b) b lc in p th t

khng trung tnh my pht in

Cng c th nhn nhn c in p U0 bng cch ni t im trung tnh ca h thng, thd ca my pht in Hnh v 2-3- b qua mt bin in p mt pha. Rle c ni vo cunth cp ca bin in p. Khi chm t s c dch chuyn in p

U0 ca im trung tnh v trn cc cc ca rle c in p l R 01

U Uun

.

1.5.3.4S lc in p th t nghch (LU2)S nguyn l ca b lc in p th t nghch (LU2) nh Hnh v 1-17

a) S nguyn l b) s ni cc t

a

b

c

C1R1

C2R2

UmnLU2

a b c

m

n

ZPT


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c) Khi khng c dng th t nghch d) Khi c dng th t nghch

Hnh v 1-17: S nguyn l ca b lc in p th t nghch

Cc in tr tc dng R1, R2 v t C1, C2 c ni vo in p dy pha th cp camy bin in p. Thng s ca t in v in tr c chn theo quan h:

11

3R

C v2

2.31R

C

ch in p i xng bnh thng (ch c thnh phn in p th t thun U1),in p u ra ca b lc Umn = 0 (Hnh v 1-17 -c). i vi in p ba pha th t nghch U2,( Hnh v 1-17 -d) in p u ra ca b lc LU2 bng:Umn = 3 .UT. Trong UT l in pdy pha th cp ca bin in p.

1.6 NGUNIN THAO TC

Cc ngun in thao tc dng cung cp in cho h thng rle bo v, iu khin, vbo tn hiu, thao tc ng v ct my ct v dng vo mt s mc ch khc trong cc nhmy in, trm bin p, trung tm vn hnh iu khin HT

Ngun in thao tc cn bo m cc yu cu sau:

c lp hon ton vi ch lm vic xoay chiu nng lng cung cp cho h thng bo v, iu khin, tn hiu, v lm vic chc

chn trong qu trnh lm vic

An ton, tin cy v kinh tHin nay thng dng ngun in mt chiu do c quy cung cp v ngun in xoay

chiu do bin dng in, bin in p v mng in p thp cung cp.

1.6.1 Ngun in thao tc mt chiu

Thng dng cc b cquy c in p nh mc ty theo m hnh trm, v in p nhmc ca cc thit b bo v. Thng thng in p ca cc thit b t 24, 48, 110 hoc 220V.Thit b bo v cn phi lm vic chc chn khi in p ca ngun c quy dao ng trongkhong (0,8 - 1,1 )Um.

u im ca cc ngun in thao tc mt chiu l s c lp hon ton ca chng ivi in p v tnh trng lm vic ca h thng c bo v.

B

AC

n m

UCA

UBC

UAB

Umn

UBn

UmB

UAm

UnC

2A

B C

BCABBnmB

CA

UnC

UAm

1

Umn=0


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Tuy nhin chng cng c mt s khuyt im ln sau:

c hi (nht l cc c qui ch)Cn t v chm sc c quyMng thao tc ca cc phn t lin h vi nhau, kh pht hin im chm t.

V d: S nguyn l mt pha dng rle dng in c c tnh thi gian ph thuc cgii hn c trnh by trn Hnh v 1-18

1RIT 4RG

2MC

+

-

T b c qui

CC

N1

N2

3BI5

6

Tn hiu

T

Hnh v 1-18: S dng rle dng in c c tnh thi gian ph thuc c gii hn lm vic

vi dng in thao tc mt chiu

Khi bo v khi ng rle dng in 1 RIT khp tip im v u dng ca ngunin thao tc mt chiu t vo cun ct CC ca my ct 2MC. Sau khi my ct m, tip imBT ca b phn truyn ng my ct m ra, ngt mch dng in thao tc trc khi tip imca rle RIT m trnh h hng tip im ca rle do dng in qua cun ct ln. Rle

trung gian 4 RG dng kim tra mch ct. Khi c h hng trong mch ny, tip im 4 RGng li v cho tn hiu. in tr 5 lm gim dng in qua cun ct n tr s b hn tr sdng in lm vic ca n.

Trong mch mt chiu c khi chm t ti hai im (th d ti N1 v N2 trn Hnh v1-18 tip im ca rle b ni tt lm cho bo v tc ng nhm. V vy cn phi t bo vchng chm t mt im tc ng bo tn hiu trong mch mt chiu.

1.6.2 Ngun in thao tc xoay chiu

Xu hng dng ngun in thao tc xoay chiu c c bit ch trong nhng nmgn y. Sau y ta s xt mt s s thng dng.

1.6.2.1S kh ni tt cun ct ca my ct.Cun ct ca my ct bnh thng b ni tt bi tip im thng ng ca rle 1RIT

nh Hnh v 1-19. Khi bo v tc ng, rle thay i trng thi ca cc tip im v kh nitt cun ct my ct. Cng sut ca cun ct kh ln. V vy khi ct bin dng in c th bqu ti v sai s s tng ln. Tuy nhin i vi bo v iu ny khng nh hng g, nukhng v sai s tng ln m dng in qua rle gim xung thp hn dng in tr v.


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Hnh v 1-19: S bo v dng in dng ngun thao tc xoay chiu theo phng php kh

ni tt cun ct ca my ct

1.6.2.2S dng bin dng bo ho trung gian.Khi khi ng rle RIT ng tip im thng m a dng in thao tc t bin dng

bo ho trung gian 3 BIBH vo cun ct CC (Hnh v 1-20-a). Nh bo ho nn 3BIBH bom c dng in th cp gn nh khng i, cho b phn truyn ng ca my ct lmvic khi dng in s cp vt qu gi tr ti thiu cho.

Hnh v 1-20: S bo v dng in ni vo dng in thao tc xoay chiu qua bin dng

bo ho trung gian

Thc t vn hnh cho thy trong s ny khi bi s dng in ngn mch tng, domch th cp ca BIBH h, hin tng h mch pha th cp ca bin dng in c th rtnguy him. khc phc khuyt im ny ngi ta dng s vi rle RIT c tip imchuyn tip (Hnh v 1-20-b). Trong s ny, bnh thng cun th cp ca 3BIBH cni tt bi tip im thng ng ca rle RIT.

1.6.2.3B cung cp lin hp.B cung cp lin hp dng cho dng in thao tc bng cch tng hp cc dng in

chnh lu t cc ngun dng in (bin dng in) v in p (bin in p). T in 3 dng gim bt ph ti ca bin dng in (b thnh phn phn khng) v n nh in p trn

b chnh lu nh Hnh v 1-21.

Trong cc b cung cp lin hp cn chn pha ca dng in v in p sao cho cngsut nhn c l ln nht.


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Hnh v 1-21: S b cung cp lin hp

1.6.2.4Dng nhng t in c np sn.Ngun ca dng in thao tc l l b t in 1 c np in qua bin in p 2 v

chnh lu 3 (Hnh v 1-22). Nng lng CU2/2 tch trn t in phi ln hn nng lnglm vic ca cun ct my ct. My bin p tng 4 (t 100V ln 400V) dng gim bt indung C ca t in. in tr 5 dng hn ch dng in np ca t in v dng in quan khi chnh lu 3 b chc thng. Tuy nhin in tr ny li lm tng thi gian np ca tin, gy tr ngi ln cho cc thit b t ng ng tr li tc ng nhanh.

Rle in p 6RU c tc dng ngn chn dng in ngc qua chnh lu khi in ppha s cp st xung.

u im ca ngun in thao tc dng t in c tch in trc l s c lpca n i vi cc dng h hng ca phn t c bo v. Tuy nhin ngun in thao tc nych c th tc ng trong thi gian ngn nn khng th dng cung cp cho cc b phnca bo v tc ng c thi gian (nh rle thi gian chng hn).

Hnh v 1-22: S ngun cung cp bng b t np sn

1.7 KNH THNG TIN TRUYN TN HIU

1.7.1 Cc loi knh truyn tn hiu

phc v cho vic truyn d liu, thng tin lin lc, iu khin, bo v v t ngho, h thng in c th dng nhiu loi knh truyn tn hiu khc nhau.

Dy dn ph/cp thng tin ca ngnh in hoc mng bu chnh vin thngKnh ti ba (PLC): Ti tn hiu tn s cao bng dy dn ca ng dy ti inKnh thng tin v tuyn siu cao tn (viba)Cp quang


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i vi h thng bo v r le, knh truyn tn hiu c s dng trong cc s bo vso lch hoc trong cc s iu khin lin ng cc bo v ln cn nhau nhm mc chnng cao tin cy ca cc bo v trong vic loi tr s c, hoc tc ng nhm.

V d nh trong s bo v so lch (so lch pha hoc so lch dng in), tn hiu haiu phn t c bo v (gc pha ca cc dng in hoc bin v gc pha ca cc dngin tu theo phn loi bo v) c truyn qua knh dn tin hnh so snh ti v tr tthit b bo v r le.

Hnh v 1-23: Lin h gia cc thit b lm vic vi knh truyn tn hiu

Thng dng ba loi tn hiu iu khin sau:

Tn hiu ct lin ng: ct ng thi cc my ct cc pha khc nhau ca phn tc bo v hoc my ct ln cn vi my ct b h hng.

Tn hiu cho php: My ct ch c th c ct ra khi nhn c tn hiu cho php ngthi vi s tc ng ca thit b bo v r le lm nhim v bo v chnh chng li ccs c ang xt.

Tn hiu kho: My ct ch c th c ct ra khi khng c tn hiu kho ng thi vis tc ng ca thit b bo v r le lm nhim v bo v chnh chng li loi s cang xt.Lin h gia cc thit b lm vic vi knh truyn tn hiu c minh ho trn Hnh v

1-23

S

bo vr le

Ct lin ng

KNH

TRUYN

TN HIU

Cho php

Kho

Ct lin ng

Cho php

Kho

S bo vr le

Tn hiu iu khin(Pht)

Tn hiu iu khin(Thu)

o xa

iu khin xa

Thoi

D liu

Thng tin

o xa

iu khin xa

Thoi

D liu

Thng tin

ng dy ti in

U ICtU I Ct


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1.7.2 Yu cu i vi knh truyn tn hiu

Thi gian loi tr s c bao gm thi gian tc ng ca r le, thi gian truyn tn hiuv thi gian ct ca my ct. Thi gian loi tr s c c xc nh t iu kin m bo chos n nh ca h thng, hn ch hu qu ca ngn mch, nhanh chng phc hi vic cungcp in cho h tiu th Thng thng thi gian truyn tn hiu cng gn bng thi gianlm vic ca bo v r le, i vi cc li in cao p v siu cao p thi gian ny vo

khong (15 40)ms ty tng loi bo v.Cc knh truyn thng b nh hng ca cc nhiu khc nhau tu theo loi knh

truyn. Cc nhiu ny c th lm cho bo v tc ng sai hoc mt tn hiu iu khin. ctrng cho tnh nng truyn i vi tng loi tn hiu iu khin, thng dng ba thng s sau

Thi gian lm vic cc i Tac.Xc sut hin tn hiu l PVC. an ton (1- PVC). 100%Xc sut mt tn hiu iu khin PMC. ph thuc (1- PMC). 100%

1.7.3 Mi trng truyn tn hiu v nhiu

1.7.3.1Dy dn ph hoc cp thng tinDy dn ph hoc cp thng tin in lc thng c t cng rnh vi cp cao p hoc

trong rnh cp ring hay bng dy trn trn ct. V cc dy dn ph hoc cp thng tin ct song song vi ng dy ti in nn c sc in ng cm ng. in p cm ng tn scng nghip thng c tnh ton sao cho cc thit b th cp c th chu ng c.

hn ch in p cm ng dng cc van chng qu in p ni tt cc dy dn phtrong trng hp in p tng cao (khi xut hin qu trnh qu ), nhng n c th lm cho

bo v khng tc ng trong trng hp qu in p gy nn bi s c chnh m bo v phi

tc ng. Cc thit b th cp phi chu ng ni in p cm ng khi c st nh hoc khing ct bn pha s cp ca h thng in.

Dy dn ph v cp thng tin dng cho bo v c s dng t u th k 20, tuy nhinphm vi s dng b hn ch v tin cy thp v gi chi ph tng i cao. i vi cc hthng in tp trung, khong cch gia cc u pht v thu tn hiu khng ln, c th dngdy ph hoc cp thng tin ring.

Nu dng knh truyn tin ca h thng vin thng th kh nng qu in p pha thcp c th thp hn v l trnh ca knh thng tin khc vi l trnh ng dy ti in, tuynhin cc thit b pha th cp cng phi c kh nng chu mt mc qu in p nht nh.

Trong mt s trng hp s c chm t, th im ni t ca nh my in v trm

bin p c th kh cao, v vy cn phi dng bin p phn cch m bo an ton cho ngiv thit b ca h thng bu chnh vin thng. Cc bin p phn cch phi chu ng cin p kh cao (n 15kV).

Dy dn ph v cp thng tin lm vic vi tn hiu truyn dn t mt chiu n 200Hzxoay chiu, vi bn knh 11km, thch hp vi bo v so lch.

Trong li 110kV thng khng yu cu thi gian tc ng ca bo v tht nhanh, ccknh thu bao c th dng chung cho in thoi, o lng v bo v do chi ph thu baotng i thp.


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Vi li in 220 500kV, yu cu v thi gian ca bo v phi nhanh hn v knhtruyn phi c tin cy cao hn nn phi thu bao ring cc knh truyn dng cho bo v.

1.7.3.2Cc knh ti ba (PLC)i vi nhng ng dy di hoc i qua nhng a hnh phc tp vic lp t dy dn

ph gp nhiu kh khn v tn km. Trong trng hp ny s dng dy dn ca chnh ngdy ti in truyn tn hiu cao tn dng cho bo v v thng tin lin lc. u im l dy

dn chc chn hn, tn hao trong truyn tn hiu s thp hn, knh truyn ho n ton nm diquyn kim sot ca cng ty in lc.

C th s dng mt hay hai pha ca ng dy ti in bng cch t cc b chn haiu ng dy c bo v. Cc b chn ny c tng tr rt b i vi dng in tn s cngnghip nhng rt ln i vi tn hiu cao tn dng cho thng tin bo v cc tn hiu nykhng lan truyn ra ngoi phm vi ng dy bo v.

S hai pha tuy c tn km hn so vi s pha - t, nhng mc tn hao khi truyntn hiu s thp hn v khng b ph thuc vo in tr t cng nh ni t v vy cdng rng ri. Tn hao tn hiu trn ng dy t ph thuc vo ma m.

Cng sut u ra ca thit b pht cao tn thng t 2 100W (+50dBm) tu tng

tng quan gia tn hiu nhiu.Mc tn hiu truyn cao nht hoc thi gian truyn tn hiu d i nht tu thuc vo tng

quc gia khng nh hng n h thng thng tin v truyn thng ton quc.

Khi c st nh vo ng dy hoc ng dy b s c hay thao tc dng ct, c thgy nhiu mnh n knh thng tin. Mc d nhng nhiu ny ch xy ra trong thi gian ngn(khong vi ms) nhng n c th lm cho thit b thu cao tn b qu ti. Cc thit b thuc hthng ct lin ng phi c chnh nh khng xy ra tc ng nhm.

Cn ch trng hp dng nguyn l truyn tn hiu cho php v tn hiu cho phpc truyn qua on ng dy b s c. Mc tt dn ca tn hiu cao tn truyn quakenh dn ph thuc vo loi s c, tuy nhin thng chn trong gii hn gia 20 n 30dB.

1.7.3.3Cc knh v tuyn vi baCc knh vi ba cho php truyn tn hiu trong mt di kh rng v s dng cc modem

vi nng lc truyn rt ln. Tn hiu bo v v iu khin c th truyn ni tip vi di ln v m ho phc tp m bo tin cy ca truyn tin nhng vn phi gi c tc truyn rt cao. Trn thc t, c th dng chung cc thit b v tuyn tiu chun trong thngtin vo mc ch truyn tn hiu bo v v iu khin trong h thng in.

Thng cc thit b vi ba lm vic vi tn s t 0,2 10GHz v cc thit b vi ba lmvic c nh hng v di tn s c nh trc nn t b nhiu, cho php s dng ngthi nhiu knh thng tin v m rng di tn s ca tn hiu truyn dng cho c mc chthng tin (thoi) ln truyn d liu.

H thng truyn tn hiu bng knh v tuyn siu cao tn (vi ba) c s dng rng ri lin h cc trung tm iu khin vi nhau. Khi l trnh ca cc knh vi ba trng hp vi ltrnh ca ng dy ti in, c th s dng cc knh vi ba vo mc ch truyn tn hiu bov. Trn thc t cc trm vi ba khng trng hp vi cc trm u v cui ca ng dy tiin nn kh nng s dng cc knh vi ba trc tip truyn tn hiu bo v thp hn so vicc knh ti ba ca h thng.

Mc tt dn ca tn hiu vi ba khng ph thuc s c trn ng dy ti in nhngb nh hng ca nhiu v tuyn, nhiu ny thng do bn thn cc thit b v tuyn gy nn.Chiu cao ca cc ct ng ten vi ba c hn ch nh hng ca gi bo v thay i nhitkhng tc ng nhiu n s lm vic ca ng ten.


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1.7.3.4Cc knh cp quangCp quang l nhng si thu tinh nh c kh nng truyn nh sng i xa. Trong h

thng in cp quang thng c ch to kt hp bn trong dy nhm li thp lm nhimv chng st trn cc ng dy ti in.

So vi cp thng tin dng tn hiu in, cp quang c u im l nng lc truyn ti rtln v khng b nhiu bi sng in t. Tn hiu quang sau khi c m ho, c truyn

theo si quang n u nhn, ti y s phi gii m chuyn thnh nhng thng tin cnthit.

Thit b m ho v gii m thng c s dng c tn s tng ng vi bc sng850, 1300, 1550 nanomet. Khong cch c th truyn tn hiu quang trc tip ph thuc vomc suy gim v tn x ca tn hiu trong h truyn dn nh sng, ph thuc vo chngloi, cht lng ca si quang v bc sng ca ngun pht tn hiu.

Vi cc knh truyn tn hiu quang tn s hng trm megahec khong cch truynhng chc kilomet, khi khong cch ln hn cn c nhng trm lp trung gian. Cc knhtruyn bng cp quang hin i c kh nng truyn ti ln cc tn hiu thoi, o lng, iukhin v bo v.

Hin nay cp quang c ch to kt hp vi cp lc gim gi thnh v tng tnh bn

vng, an ton ca tuyn cp quang v c s dng rng ri khng nhng trong cc h truynti cao p v siu cao p m cn c dng i vi li in trung p v h p.

1.8 THNG TIN CN THIT PHC V TNH TON BO V RLE

1.8.1 Nguyn l lng dng trong mc ch bo v

1.8.1.1o lng mt i lng u voi lng u vo X ca rle thng l nhng i lng tng t (dng in, in

p) c ly ra tpha th cp ca my bin dng in v my bin in p.

Tr s hiu dng, tr s tuyt i hoc tr s tc thi ca i lng u vo c so snhvi ngng tc ng ca rle (cn gi l tr s chnh nh ca rle). Nu i lng u vo

bin thin vt qu (i vi rle cc i) hoc thp hn (i vi rle cc tiu) ngng chnhnh th rle s tc ng. Sau khi tc ng xong nu i lng u vo bin thin theo chiungc li v vt qu tr s tr v XTV, rle s tr v trng thi ban u trc lc khi ng.Tr s XTV c gi l ngng tr v hoc tr s tr v. Tr s tr v v tr s khi ng clin h vi nhau qua h s tr v kV:

k

TVV X

Xk

i vi cc rle in c kV 1, thng thngkV = 0,85 0,9 i vi rle cc i.

kV = 1,1 1,15 i vi rle cc tiu.

i vi rle tnh v rle s kV 1.Khi nim rle cc i (tc ng khi i lng u vo tng) v rle cc tiu (tc ng

khi i lng u vo gim) c nh hng n cu trc ca rle in c (cun dy, l xo, tipim). i vi rle tnh v rle s chc nng cc i v cc tiu d dng i ch cho nhau

bng php nghch o tn hiu l gic u ra ca rle.


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1.8.1.2So snh nhiu i lng u voRle c th tc ng trn c s so snh nhiu i lng u vo nh rle khong cch,

so lch, nh hng cng sut v.v.. lm vic vi hai i lng u vo. Trong trng hp tngqut, hai i lng u vo X1, X2 l t hp ca dng in I v in p U ca phn t bo v:

IKUKX

IKUKX

432

211

y cc h s t l K1, K2, K3, K4 l nhng h s phc. Ty tng loi bo v (loirle) c th chn nhng tr s thch hp cho nhng h s ny. Nh rle so lch dng in, haii lng dng so snh l vc t dng in hai u phn t c bo v 1I v 2I , khi ychn K1 = K3 = 0 v K2 = K4 = 1. i vi rle khong cch, hai i lng dng so snh lin p ch t bo v v dng in chy qua phn t c bo v nn ta chn K1 = K4 = 1 vK2 = K3 = 0.

Vi cc rle lm vic theo hai i lng u vo thng ngi ta dng hai nguyn l sosnh: so snh bin v so snh pha.

1.8.1.3So snh bin

Trong cc rle lm vic theo hai i lng u vo (chng hn X1) tc ng theo chiuhng lm cho rle khi ng cn i lng kia (X2) tc ng theo chiu hng ngc li(hm, cn tr s tc ng ca rle).

Tn hiu u ra Y s xut hin khi: 21 XX

trong : 1X tn hiu u vo khi ng, 2X tn hiu u vo hmNguyn l so snh bin hai i lng in c s dng trong bo v so lch v bo

v khong cch nh Hnh v 1-24.

Hnh v 1-24: Nguyn l so snh bin hai i lng u vo

1.8.1.4So snh pha.So snh pha phn nh gc lch pha gia cc i lng u vo, nu gc lch pha vt

qu (ln hn hay b hn) tr s pha nh trc rle s tc ng.

Cc i lng tng t u vo X1, X2 qua cc b bin i BD1, BD2 bin thnh ccxung ch nht X1, X2 vi thi gian trng pha l tK c gi l so snh thi gian trng hp

pha. Nu thi gian trng hp pha tK ln hn thi gian t t ca b phn thi gian th s xuthin tn hiu u ra (Y = 1).


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K

,K K

t

Hnh v 1-25: Nguyn l so snh pha (a) v biu so snh hai tn hiu u vo hnh sin lch

pha nhau (b)

Trn Hnh v 1-25 trnh by biu so snh na chu k dng ca hai i lng uvo hnh sin X1 v X2. Cng c th tin hnh so snh c na chu k m tng mc tcng nhanh ca b phn so snh. tng chnh xc ca b phn so snh pha c th lc v kh thnh phn mt chiu cng nh cc sng hi bc cao trong cc i lng u vo X1 vX2 trc khi a vo b so snh.

1.8.2 Tnh ton ngn mch/s c

1.8.2.1Ch h thng inS c nguy him nht trong HT chnh l s c ngn mch. Hu qu ca ngn mch

li ph thuc rt nhiu vo ch lm vic, hay ch huy ng cng sut ca HT. Ngnmch cc thi im vn hnh HT khc nhau s cho kt qu tnh ton khc nhau. Nu ch huy ng cng sut max v min chnh lch nhau ln, th dng in ngn mch s khcnhau rt nhiu. Thng thng khi tnh ton t thng s ngi ta thng tnh cho ch huyng cng sut max (cc my pht, my/thit b b huy ng ht cng sut, ph ti trong hthng l ln nht). Cn ch huy ng cng sut min (mt s my pht c th b ct ra

bo dng, sa cha) th dng kim tra nhy ca cc bo v.

1.8.2.2Cu hnh h thngCu hnh h thng c ngha rt quan trng trong vic tnh ton bo v cho HT, Cu

hnh h thng cn thit cho vic la chn phng thc bo v, cng nh loi bo v. V dng dy hnh tia, mt ngun th ch cn t mt bo v pha u ngun, nhng ng dykp, hoc mch vng th c th phi t thm b phn nh hng cng sut. Hn na, trongHT vn hnh theo c ch th trng, hoc vi s c mt vi dung lng ln ca h thngin phn tn, th dng cng sut/dng in c thay i lin tc, do cng nh hng nvic la chn thng s bo v, chiu/hng tc ng ca bo v. Cc s h thng thanhgp khc nhau, ng dy ti in nhiu nhnh r, hoc c thit b b, FACTS, hay HVDCcng s c quan tm rt nhiu khi tnh ton bo v rle.


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1.8.2.3Dng/loi s cKhi tnh ton mt h thng bo v, ngi ta mong mun n s bo v c tt c cc

dng/loi s c c th xy ra trong h thng. Do cc dng/loi s c s cn phi c quantm, nghin cu, tm hiu nguyn nhn, v c ch xy ra t c cc phng thc bo vtng ng v hiu qu. C th k v d y mt s s c nh:

i vi ng dy trn khng/cp ngm:Cc dng ngn mch: ba pha (N3), hai pha (N2), hai pha ni t (N1-1), chmt mt pha

i vi my pht in:Ngn mch gia cc pha, ngn mch gia cc vng dy trong mt pha, qu ti,qu in p, mt cn bng pha, mt kch thch, qu tc , suy gim tn s, chmt cun dy roto, h hng h thng lm mt

i vi my bin p:Ngn mch gia cc pha, ngn mch gia cc vng dy trong mt pha, thngthng du,

i vi ng c in:Ngn mch gia cc pha, chm t v ng c

1.8.2.4Tnh ton ngn mch theo tiu chunThng thng vic tnh ton ngn mch c thc hin bi cc cng c tr gip,

thng l cc phn mm my tnh chuyn dng, v vic tnh ton ngn mch cng cn phitun theo cc tiu chun quc t. Hin nay hay dng tiu chun quc t IEC: 60909-0, 1, 2, 4.

1.9 CU HI N TP

1 Hy nu nhim v v cc yu cu ca h thng bo v r le?2 Nu nh ngha v my bin dng in? Hy v s nguyn l lm vic v iu kin

chn my bin dng in l gi? Cch nh du cc u dy v cc ch khi ni mybin dng in?

3 Nu nh ngha v my bin in p? Hy v s nguyn l lm vic v iu kinchn my bin in p l gi? Cch nh du cc u dy v cc ch khi ni my binin p?

4 Cc yu cu i vi ngun in thao tc? Nu u nhc im ca tng loi ngun thaotc?

5 Nu nhim v v yu cu ca h thng knh thng tin lin lc?6 V sao phi tnh ton ngn mch phc v tnh ton bo v r le?


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CHNG 2: CC K THUT CH TO RLE

2.1 LCH S PHT TRIN CA RLE

Nhng rle u tin c ch to da trn nguyn l in c v c s dng cho inbo vo nhng nm 30 ca th k 19. Ngy nay, thut ng rle dng ch tp hp cc thitb t ng bo v HT, iu khin v iu chnh t ng, lm nhim v chuynmch trong cc h thng thng tin,

Cui th k 19, rle bt u c s dng bo v cc phn t trong HT di dngc cu cu in t tc ng trc tip lp sn my ct in. Tuy nhin ch th k 20 khi ccHT pht trin, k thut bo v rle mi c p dng rng ri. C th nu mt s mcthi gian ng lu :

Nm 1901: Xut hin rle cm ng dng in.Nm 1908: Bo v so lch dng in.Nm 1910: Rle hng cng sut v bo v qu dng c hng.u nhng nm 1920: Bo v khong cch.Cui nhng nm 1920: Bo v dng tn hiu tn s cao truyn theo dy dn ca mch

in c bo v (PLC).

Nhng nm 1960: Rle tnh (khng c tip im ng) in t v bn dn.Nhng nm 1970: Rle s, h thng bo v dng k thut vi x l v my tnh.

Ngy nay cc nh ch to v sn xut rle trn th gii u chuyn hng sang kthut s. Tuy nhin nc ta s lng rle in c v rle in t cn ang c s dngkh nhiu trong h thng in do iu kin lch s. i vi cc cng trnh mi c xy dngth ch yu s dng rle s do cc u im sau:

Chc nng hot ng ca rle c m rng ra rt nhiu so vi cc th h rle trcy, d dng m rng kh nng o lng, bin i tn hiu, so snh v t hp l gctrong cu trc ca rle. C th kt hp nhiu nguyn l pht hin s c v bo v trongmt h thng rle.

Ngoi chc nng bo v v cnh bo, rle s hin i cn c th thc hin nhiu nhimv quan trng khc nh:

Ghi chp cc thng s vn hnh v s cXc nh v tr s cThc hin lin ng vi thit b bo v v t ng ca phn t ln cn

ng trli my ct inD dng ghp ni vi nhau v vi cc thit b bo v, t ng, thng tin v o lngkhc trong h thng, d dng ghp ni vi h thng my tnh.


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Hnh v 2-1: So snh gia rle s v rle thng thng

Thng s ca bo v c th chnh nh gin tin vi chnh xc cao v d dng thchin cng vic chnh nh thng s t xa hoc chnh nh t ng theo nguyn l tthch nghi.

Cng sut tiu th b, kch thc gn nh, d dng chun ho kch thc.Gi thnh tng i tnh theo tng quan gia chi ph v chc nng ca h thng bo

v th rle k thut s v my tnh r hn h thng rle in c.

2.2 PHN LOI RLE

Rle l thit b chnh trong h thng thit b bo v Rle ch tc ng chuyn mch,chuyn trng thi. Phn t rle nhn mt tn hiu u vo (X) hay mt s tn hiu u vo(X1, X2, X3,) thng l nhng tn hiu tng t, bin i v so snh tn hiu ny vingng tc ng cho tn hiu u ra (Y) di dng xung ri rc vi hai trng thi i lp:c xung (trng thi 1) v khng c xung (trng thi 0).

(a): K hiu rle lm vic vi mt i lng u vo(b): K hiu rle lm vic vi nhiu i lng u vo(c,d): c tnh khi ng, tr v ca rle cc i vi mt i lng u vo(e,g): c tnh khi ng, tr v ca rle c

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