Phn 1 Kin thc chun b

TP H CH MINH THNG 04/2007

The Power System Simulator/Advanced Distribution Engineering Productivity TooL

DNG PHN MM PHN TCH V

TNH TON LI IN PSS/ADEPT

GIO TRNH TP HUN

S DNG PHN MM PHN TCH V TNH

TON LI IN PSS/ADEPT

Bin son-Trnh by: Nguyn Hu Phc ng Anh Tun Ch bin: PGS. TS. Nguyn Hu Phc

Bn quyn thuc Cng ty in lc 2 - EVN Mi hnh thc sao chp, in n phi c s ng bng vn bn ca Cng ty in lc 2.

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LLii nnii uu Li in phn phi v truyn ti khng ngng pht trin m rng v qui

m cng nh phc tp. Theo , cc yu cu cung cp in lin tc cho khch hng vi cht lng in nng ngy cng cao cng gia tng. Thit b trn li in phn phi hin nay vn c c im l a dng v chng loi, phc tp v cu to. Qu trnh vn hnh nhm thc hin nhng thao tc mang tnh lp i lp li nhiu ln nhng li i hi chnh xc cao v vy rt cn thit phi t ng ha bng cch a nhiu thit b t ng, x l thng tin t ng nhm tng kh nng truyn t v x l thng tin. Bng my tnh v cc phn mm chuyn dng chng ta c th ngn chn trc v hn ch hng hc trong qu trnh vn hnh li in. Nhng thnh tu mi v Cng ngh Thng tin nh v kh nng lu tr ca phn cng, tc tnh ton, cc phng php h chuyn gia, mng neuron, cung cp nhng phng tin v cng c mnh tng cng nghin cu m rng ng dng trong lnh vc in nng. m bo v gi vng mi lin h hu c ca cc thnh phn trong h thng sn xut truyn ti, phn phi v s dng in nng.

p ng kp thi cc yu cu trn, t thng 01-2005 Tng cng ty in lc Vit Nam (EVN) trc y, nay l Tp on in lc Vit Nam ch o p dng th im phn mm PSS/ADEPT tnh ton li in theo a bn do cc n v trc thuc qun l.

Phn mm PSS/ADEPT c pht trin dnh cho cc k s v nhn vin k thut trong ngnh in. N c s dng nh mt cng c thit k v phn tch li in phn phi. PSS/ADEPT cng cho php chng ta thit k, chnh sa v phn tch s li v cc m hnh li in mt cch trc quan theo giao din ha vi s nt khng gii hn. Thng 04-2004, hng Shaw Power Technologies cho ra i phin bn PSS/ADEPT 5.0 vi nhiu tnh nng b sung v cp nht y cc thng s thc t ca cc phn t trn li in.

Cng ty in lc 2-Tp on in lc Vit Nam (EVN) phi hp cng Khoa in-in t trng i hc Bch Khoa thnh ph H Ch Minh nghin cu p dng phn mm ny. Cng ty in lc 2 thc hin tp hun cho cc n v trc thuc nhm trang b kh nng s dng phn mm chun tnh ton v phn tch li in da trn phn mm PSS/ADEPT. iu ny, nhm gip Cng ty in lc 2 tng bc h thng ho, chun ho kin thc p dng tnh ton v in trong cc hot ng ca Cng ty nht l cng tc qun l k thut vn hnh li in. u tin l cc bi ton: phn b cng sut trn li, ngn mch, b

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cng sut phn khng, tin cy,l cc vn m cc n v cn gii quyt hng ngy, thm ch hng gi.

Cc Cng ty in lc cn trin khai cng tc o to n mc chi tit v s dng phn mm tnh ton k thut in chuyn ngnh nh PSS/U, PSS/ADEPT, PSS/E, cc n v trc thuc s dng thnh tho cc chng trnh ny.

Cng ty in lc 2 s trang b kin thc Cng ngh Thng tin ni chung v phn mm tnh ton k thut chuyn ngnh in ni ring cho cc n vi trc thuc trong Cng ty in lc 2 thng qua cc kho o to kt hp vi v trng i hc Bch Khoa thnh ph H Ch Minh. Tin khai ng dng cc phn mm tnh ton k thut in trong ton Cng ty theo yu cu ca EVN. To iu kin cc n v trong Cng ty tm hiu cc phng php tnh ton cc bi ton in c bn v cch xy dng thut ton tnh ton p dng trong phn mm tnh ton chuyn nghip l phn mm PSS/ADEPT ca hng Shaw Power Technologics Inc-USA. nh gi, theo di v gim st hiu qu cng tc pht trin xy dng mi, i tu ci to, qun l k thut v vn hnh li in ca cc n v da vo cng c hiu qu l phn mm tnh ton k thut in PSS/ADEPT. Lm c s i ng cn b k thut cc n v d dng tip thu v nm bt cc phm mm khc sau ny, v d nh PSS/E. EasyPower,

Vic t chc o to s gp phn nng cao kh nng ng dng my tnh, nht l s dng cc phn mm tnh ton chuyn ngnh in cho cc n v trc thuc trong Cng ty in lc 2. Ph bin kinh nghim v trin khai cc kt qu nghin cu cc phn mm, cc n v tip tc p dng vo thc t cng tc ti n v. Gp phn hon thnh tt cng tc sn xut kinh doanh ca n v trn c s cc kt qu tnh ton t cc phn mm mnh. To ra s phi hp sn sng da trn quan h tt p vn c gia Cng ty in lc 2-n v qun l li in v trng i hc Bch Khoa thnh ph H Ch Minh-n v gio dc o to

V gio trnh ny c bin son nhm mc ch phc v cho cc bui tp hun phn mm PSS/ADEPT 5.0 nh trn.

Nhm bin son rt cm n s hp tc m Cng ty in lc 2 dnh cho nhm ni ring cng nh cho Khoa in-in t trng i hc Bch Khoa thnh ph H Ch Minh ni chung. Nhm bin son cng cm n mt s cng tc vin h tr xy dng gio trnh ny.

Nhm bin son

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TTmm tttt nnii dduunngg Gio trnh ny c bin son phc v cho cc bui tp hun s dng phn

mm phn tch v tnh ton li in PSS/ADEPT 5.0. Gio trnh gm cc phn:

Phn 1: Kin thc chun b yu cu-n tp kin thc Phn 2: Hng dn s dng PSS/ADEPT Phn 3: Cc k nng s dng phn mm PSS/ADEPT-Phn cn bn Phn 4: Cc k nng s dng phn mm PSS/ADEPT-Phn nng cao

hc vin cc n v nm bt v p dng nhanh, cn c thm cc phn:

Phn 5: Cm nang s dng Phn 6: Thut ng Anh-Vit i chiu qua cc slide bi ging phn

mm PSS/ADEPT

Phn 7: Cc slide bi ging ca chuyn gia PTI software. Ngoi ra cn c Gio trnh in t lu tr trn a CD-ROM: Gm cc ti

liu a phng tin (Multimedia) h tr thm cho cc hc vin chun b bi hc trc khi ln lp, n tp sau kha hc v a phng cng tc. c thc hin bng k thut lp trnh Web v x l Multimedia (dng phim c m thanh, Web page,)

Cc chng trnh chuyn i:

1. Chng trnh Chuyn Excel DAT File. 2. Chng trnh Chuyn DAT File Excel. 3. Chng trnh x l s liu u vo

4. Chng trnh Tnh Cng Sut Ngun.

5. Chng trnh Tnh Tng Tr My Bin Th.

6. Chng trnh chia s PSS/ADEPT qua mng LAN, WAN v internet

7. H thng cc bi tp trc nghim trn my tnh sut kho hc

8. Chng trnh thi kt thc kho hc bng trc nghim trc tip trn my tnh

V cc CD-ROM:

-CD1: Gio trnh in t h tr

-CD2: Cc bi ging v bi tp

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-CD3: D liu li in

-CD4: D liu li in (tt) v source cc chng trnh h PSS/*

-CD5: Cc chng trnh h tr kho hc

Gm cc ti nguyn hc tp nh: ti liu tham kho, Users Guide, website PTI (offline, xem khng cn kt ni internet), web documents, source software PSS/ADEPT and untilities, cc phn mm chuyn i d liu v demo phc v ng dng tnh ton bng PSS/ADEPT,

Qua kinh nghip tp hun v gip cc hc vin thuc cc n v in lc p dng nhanh phn mm PSS/ADEPT. Chng ti ch trng chnh vo 4 mc tiu p dng trin khai PSS/ADEPT nh sau:

V cc ni dung nng cao:

Biu din trng thi li in trc v sau khi gii cc bi ton phn tch.

S dng cc lp d liu. T chc v qun l ph ti v khch hng s dng in. Kh nng h tr cc c s d liu khc. B sung cc thng s dy dn vo t in cu trc dy dn. B sung thit b bo v vo th vin thit b bo v.

To s Creating diagrams

Thit lp thng s mng li Program, network settings

Chy 8 bi ton phn tch Power System Analysis

BO CO Reports, diagrams

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M rng bi ton phn tch cho li in qui m ln, nhiu cp in p

nh gi li in trc v sau khi gii cc bi ton phn tch. p dng kt qu tnh ton lm c s vn hnh li in. Thc hin

lp v bo v cc k hoch tiu, trung v i tu hay pht trin mi li in.

Phn tch v tnh ton li in trn nn H thng thng tin a l-GIS.

M phng vn hnh li in. Tham kho cc phn mm tnh ton phn tch li in khc.

Nhng ni dung ny gip hc vin tm hiu thm mt s kin thc hu ch lin quan.

Chi tit ni dung s c trnh by trong phn u cc tp gio trnh v cc chng trong cc phn.

Nhm bin son

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TThhuutt nngg,, kk hhiiuu vv vviitt tttt..

CAD: Computer Aided Design CAM: Computer Aided Manufacture CNPM: Cng ngh phn mm CNTT: Cng ngh thng tin. CSDL: C s d liu. GUI: Graphic user interface. GIS: H thng thng tin a l-Geographic Information System IA: Tr tu nhn to-Inlelligence Artificielle MIS: H Thng Tin qun l NNLT: Ngn ng lp trnh. PC: Personal computer SQL: Structured query language. CB: Cn b DS: Disconect Swicth-Dao cch ly. EVN: Tp on in lc Vit Nam H s dng in: H s dng in qua cu li, qua in k ph. HT: H thng in. IEC: y ban k thut in quc t-International Electro-

technical Commission. ISO: T chc tiu chun quc t-International Organization for

Standardization Khch hng: H s dng in theo hp ng cung ng s dng in vi

ngnh in qua in k chnh. LBS: Load break switch-Dao cch ly ng ct c ti. LPP: Li in phn phi. LTD: Dao cch ly chu sc cng-Line Tenson Disconect MBA: My bin p LKV: in lc khu vc. PC HCMC: Cng ty in lc TP HCM PC 2 Cng ty in lc 2 REC: My ct t ng ng li-Recloser SCADA: H thng iu khin v gim st thu thp d liu. TP.HCM: Thnh ph H Ch Minh VHL: Vn hnh li in. KC: Khi ng ng c Network: Li in

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D liu mu c sn trn CD-ROM/DATA

Ht chng !

Ch Lin quan V d, bi tp Lu tp tin v d mu Ht chng

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Mc lc tng qut Phn Mt: Kin thc chun b CHNG 1: M HNH LI IN CHNG 2 PHN B CNG SUT CHNG 3: NGN MCH CHNG 4: BI TON KHI NG NG C V XC NH IM DNG TI U CHNG 5: PHI HP BO V CHNG 6: SNG HI CHNG 7: XC NH V TR B TI U CHNG 8: NH GI TIN CY CHNG 9: CC VN KHC CA LI IN PHN PHI Phn Hai: Hng dn s dng phn mm CHNG 1: HNG DN CI T PHN MM PSS/ADEPT CHNG 2: HNG DN S DNG PHN MM PSS/ADEPT PH LC 1: M HNH XUT TUYN DY C LP PH LC 2: NGUYN TC PHN PHI PH LC 3: KIU D LIU Phn Ba: K nng p dng-Phn c bn CHNG 1: D LIU CHUN B CHNG 2: CC BC THC HIN CHNG 3: MT S KT QU P DNG Phn Bn: Cm nang s dng Phn Nm: K nng p dng-Phn nng cao CHNG 1: X L S LIU CHNG 2: B SUNG CC THNG S VO PHN MM CHNG 3: BIU DIN, PHN TCH V NH GI KT QU TNH TON H TR

RA QUYT NH CHNG 4: C KT KINH NGHIM P DNG TI MT S LI IN CA CC

IN LC KHU VC CHNG 5: QUN L V TNH TON LI IN PHN PHI TRN NN H

THNG THNG TIN A L CHNG 6: M PHNG VN HNH LI IN CHNG 7: GII PHP CHIA S KHA CNG PHN MM TRN MY N CHO

NHIU NGI S DNG CHNG 8: TM HIU MT S PHN MM PHN TCH LI IN KHC Phn Su: Thut ng Anh-Vit i chiu qua cc slide bi ging Phn By: Cc slide bi ging ca PTI software

S DNG PHN MM PHN TCH V TNH TON LI IN

PSS/ADEPT

Phn Mt Kin thc chun b

GIO TRNH TP HUN

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MMCC LLCC CCHHII TTIITT PPHHNN 11 MC LC CHI TIT PHN 1 ........................................................................ 1 CHNG 1: M HNH LI IN............................................................. 7 I. Li in phn phi ....................................................................................... 8

I.1. Li in phn phi .................................................................................................... 9 I.2. Cc loi s h thng li phn phi:.................................................................... 10

I.2.1. S hnh tia: .................................................................................................... 11 I.2.2. S hnh tia c ci tin................................................................................ 12

II. M hnh li in ca phn mm PSS/ADEPT 5.0 ................................... 14 II.1. Nt ........................................................................................................................... 14 II.2. Ngun....................................................................................................................... 15

II.2.1. Nhiu ngun hot ng..................................................................................... 15 II.2.2. Ngun 3 pha...................................................................................................... 16

II.3. Ph ti ...................................................................................................................... 17 II.4. T b ........................................................................................................................ 18 II.5. ng dy................................................................................................................ 18 II.6. My bin th ............................................................................................................ 19

II.6.1. My bin th lc ............................................................................................... 20 II.6.2. My bin th lc c kt ni thnh my bin th t ngu.............................. 23 II.6.3. B iu p ......................................................................................................... 24

II.7. M hnh my in .................................................................................................... 31 CHNG 2: PHN B CNG SUT ......................................................... 39 I. Phng trnh i s phi tuyn ...................................................................... 40

I.1. Phng php Gauss Seidel..................................................................................... 40 I.2. Phng php Newton Raphson.............................................................................. 41

II. Phn b cng sut trong li in .............................................................. 42 II.1.1. Phng trnh cn bng cng sut ...................................................................... 42 II.1.2. Phng php Gauss Seidel ............................................................................ 42 II.1.3. Phng php Newton Raphson gii bi ton phn b cng sut................... 43

III. Phng php tnh phn b cng sut ca phn mm PSS/ADEPT 5.0 .... 45 III.1.1. Ngun .............................................................................................................. 46 III.1.2. Dy v cp ....................................................................................................... 46 III.1.3. My bin th .................................................................................................... 46 III.1.4. M hnh my in............................................................................................ 47

CHNG 3: NGN MCH......................................................................... 50 I. L thuyt bi ton ngn mch...................................................................... 51

I.1. Phng php n v tng i.................................................................................. 51 I.2. Tng tr tng ng Thevenin ............................................................................... 52 I.3. S c khng i xng ............................................................................................... 54 I.4. Xy dng mng th t ca h thng in ................................................................. 56 I.5. S c trn ng dy phn phi hnh tia: ................................................................. 57

II. Phng php tnh ngn mch ca phn mm PSS/ADEPT 5.0 ................. 58 II.1.1. Ngun................................................................................................................ 58 II.1.2. ung dy v cp ............................................................................................. 58 II.1.3. My bin p ...................................................................................................... 59

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II.1.4. M hnh my in ............................................................................................. 59 II.1.5. M hnh ti tnh................................................................................................. 60 II.1.6. Tng tr tng ng Thevenin....................................................................... 60

CHNG 4: BI TON KHI NG NG C V XC NH IM DNG TI U .............................................................................................. 63 I. Kho st v tnh ton my in.................................................................... 64

I.1. My in ng b...................................................................................................... 64 I.2. My in khng ng b........................................................................................... 64 I.3. Tnh khi ng ng c ca phn mm PSS/ADEPT 5.0 ........................................ 67

I.3.1. Ngun................................................................................................................. 67 I.3.2. My in ang hot ng................................................................................... 67 I.3.3. Khi ng my in........................................................................................... 67 I.3.4. Khi ng my bin th t iu chnh ............................................................... 67 I.3.5. Cc phng php tnh khi ng ng c ......................................................... 68 I.3.6. Gia tc ng c .................................................................................................. 69 I.3.7. Khi ng ng c tnh...................................................................................... 69 I.3.8. Khi ng ng c vi kho st n nh qu ................................................ 70 I.3.9. Nhng c trng khc ca kho st khi ng ng c .................................... 70

II. Tnh ton xc nh im dng ti u ca phn mm PSS/ADEPT 5.0 ..... 71 II.1. Gii thiu ................................................................................................................. 71 II.2. Thit t thng s kinh t cho bi ton TOPO ........................................................ 73 II.3. t cc ty chn cho bi ton TOPO....................................................................... 73

CHNG 5: THIT B BO V V PHI HP CC THIT B BO V TRN LI PHN PHI ............................................................................. 76 I. Cc thit b bo v........................................................................................ 77

I.1. Cu Ch...................................................................................................................... 77 I.1.1. Gii thiu............................................................................................................ 77 I.1.2. c tnh bo v: ................................................................................................. 78 I.1.3. Phn loi............................................................................................................. 78 I.1.4. Phm vi ng dng ca cu ch ........................................................................... 81

I.2. My Ct v Relay...................................................................................................... 82 I.2.1. Gii thiu: .......................................................................................................... 82 I.2.2. c tnh v phn loi my ct ............................................................................ 82 I.2.3. Relay: ................................................................................................................. 87

I.3. Recloser..................................................................................................................... 89 I.3.1. Gii thiu chung:................................................................................................ 89 I.3.2. Phn loi:............................................................................................................ 89 I.3.3. V tr lp t Recloser ........................................................................................ 92 I.3.4. Cc thng s chnh ca Recloser ....................................................................... 92

II. Phi hp cc thit b bo v ........................................................................ 92 II.1. C s phi hp:........................................................................................................ 92 II.2. Cc phng php phi hp gia cu ch vi cu ch:.............................................. 93

II.2.1. Gii thiu .......................................................................................................... 93 II.2.2. Cc phng php phi hp gia cu ch vi cu ch........................................ 93 II.2.3. Cu ch cho my bin p................................................................................... 97

II.3. Phi hp Recloser vi cu ch ................................................................................. 98 II.3.1. Cc nguyn tc phi hp Recloser.................................................................... 98 II.3.2. S dng c tuyn TCC c hiu chnh. ............................................................ 99

II.4. Phi hp Relay vi cu ch .................................................................................... 101 II.4.1. Phi hp cu ch pha ngun vi relay ........................................................... 102

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II.4.2. Phi hp relay vi cu ch pha ti ................................................................. 103 II.5. Phi hp Recloser vi Recloser............................................................................. 104

II.5.1. Phi hp bng cch s dng c tuyn TCC.................................................. 104 II.5.2. Nguyn tc phi hp c bn ca Recloser in t.......................................... 104 II.5.3. Nhng trng thi c bit v ph tr ca Recloser in t............................. 105

CHNG 6: SNG HI ............................................................................ 109 I. L thuyt sng hi...................................................................................... 110

I.1. Cc ngun gy sng hi trong li in: ................................................................ 110 I.1.1. Ti phi tuyn: ................................................................................................... 110 I.1.2. Bo ha mch t my bin p: ......................................................................... 114 I.1.3. My pht cp cho ti khng i xng: ............................................................. 115 I.1.4. Li in: ......................................................................................................... 115

I.2. nh hng ca sng hi n cc thit b in: ....................................................... 116 I.2.1. My in quay:................................................................................................. 116 I.2.2. My bin p:..................................................................................................... 116 I.2.3. Dy trung tnh: ................................................................................................. 117 I.2.4. Dy dn in: ................................................................................................... 118 I.2.5. Nhiu in t:................................................................................................... 118 I.2.6. T in: ............................................................................................................ 118 I.2.7. nh hng n cc thit b khc:..................................................................... 120

I.3. Phng php khc phc ha tn: ............................................................................ 121 I.3.1. Dng cun khng trit sng hi: ...................................................................... 121 I.3.2. Dng cc mch lc: .......................................................................................... 123 I.3.3. Dng b chuyn i xung trong thit b i in, iu khin:......................... 125

II. Phng php tnh sng hi ca phn mm PSS/ADEPT 5.0 ................... 126 II.1. Phng php phn tch .......................................................................................... 126

II.1.1. Ti tnh............................................................................................................ 126 II.1.2. ng c khng ng b.................................................................................. 128 II.1.3. ng c ng b............................................................................................. 129 II.1.4. T in mc shunt........................................................................................... 130 II.1.5. ng cy v cp ........................................................................................... 131 II.1.6. My bin p .................................................................................................... 133

II.2. Tnh ton sng hi.................................................................................................. 134 II.2.1. Tng dn v tng tr ....................................................................................... 134 II.2.2. Tnh ton sng hi........................................................................................... 135

CHNG 7: XC NH V TR B TI U........................................... 138 I. L thuyt b cho li phn phi:............................................................... 139 II. Phng php tnh xc nh v tr b ti u ca phn mm PSS/ADEPT 5.0....................................................................................................................... 141

II.1. Thit lp cc thng s kinh t li in cho CAPO .............................................. 141 II.2. Cch PSS/ADEPT tnh cc vn kinh t trong CAPO ....................................... 143 II.3. Thit lp cc ty chn cho php phn tch CAPO................................................. 143 II.4. Cch PSS/ADEPT tm v tr t t b ti u ......................................................... 145 II.5. Cch chy bi ton tm v tr t t b ti u......................................................... 147 II.6. Report sau khi phn tch v tnh ton .................................................................... 147

CHNG 8: NH GI TIN CY..................................................... 150 I. L thuyt bi ton nh gi tin cy....................................................... 151

I.1. tin cy l g ........................................................................................................ 151 I.2. C 4 phn lin quan n tin cy ......................................................................... 151 I.3. tin cy ca h thng in................................................................................... 151

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I.4. p ng h thng ................................................................................................... 151 I.5. An ninh h thng..................................................................................................... 151 I.6. Cc lnh vc chc nng........................................................................................... 151 I.7. Cc mc nh ga tin cy p ng tnh. ............................................................. 152

I.7.1. Mc th nht: ................................................................................................... 152 I.7.2. Mc th hai: ..................................................................................................... 152 I.7.3. Mc th ba: ...................................................................................................... 152

I.8. Cc k hiu trong tin cy: .................................................................................. 152 I.9. Ch s h thng (System Indices)............................................................................ 153 I.10. Xc nh cc ch s tin cy- .................................................................................. 154 I.11. Cc thut ng c bn ca hng hc, ct thit b v ngng cung cp in ............ 154

I.11.1. S c hng hc:............................................................................................. 154 I.11.2. Ct thit b: ..................................................................................................... 154 I.11.3. Ngng cung cp in: .................................................................................... 154

I.12. Cc ch s ti nt ti h thng phn phi ............................................................ 155 I.13. Tnh ton , r v U ................................................................................................ 155 I.14. Kh nng sn sng lm vic ca thit b ............................................................... 156 I.15. Tng quan c bn v tin cy ca h thng phn phi ...................................... 157 I.16. nh ngha cc ch tiu tin cy:........................................................................ 157 I.17. Cc tnh ton c bn cho mng hnh tia ................................................................ 160 I.18. Nguyn tc tnh ton: ........................................................................................... 160 I.19. Cc ch s tin cy c bn ti nt ti: .............................................................. 160

II. Phng php tnh nh gi tin cy ca phn mm PSS/ADEPT 5.0 .. 160 II.1.1. H s SAIFI (Tn sut ngt in trung bnh trong h thng) ......................... 160 II.1.2. H s SAIDI (Thi gian ngt in trung bnh trong h thng)....................... 161 II.1.3. H s CAIDI (Thi gian ngt in trung bnh mt v) .................................. 161 II.1.4. H s CAIFI (S ln ngt in trung bnh trn mt khch hng) ................... 161 II.1.5. H s ASAI (Mc cung cp in).............................................................. 161 II.1.6. ENS = La(i)ui ............................................................................................. 161 II.1.7. Phng php tnh ............................................................................................ 162 II.1.8. S dng module DRA trong PSS/ADEPT...................................................... 162 II.1.9. Tnh ton ch s tin cy................................................................................... 163

CHNG 9: CC VN KHC CA LI IN............................. 167 I. Cc khi nim v nh ngha v cht lng in nng .............................. 168

I.1. Cht lng in nng l g ? ................................................................................... 168 I.2. Cht lng in nng chnh l cht lng in p.................................................. 169 I.3. Ti sao chng ta cn quan tm n cht lng in nng ?.................................... 170 I.4. Cc khi nim v nh ngha ................................................................................... 170

I.4.1. Qu : ............................................................................................................. 170 I.4.2. Qu xung: .................................................................................................... 170 I.4.3. Qu dao ng: ............................................................................................. 171 I.4.4. Nhng thay i in p trong khong thi gian di:........................................ 172 I.4.5. Nhng thay i in p trong khong thi gian ngn:..................................... 173 I.4.6. S khng cn bng in p: ............................................................................. 176 I.4.7. Mo dng sng: ................................................................................................ 176 I.4.8. S dao ng in p:........................................................................................ 179 I.4.9. Nhng thay i tn s ngun in: .................................................................. 179

II. Tn tht in nng ca li in .............................................................. 179 II.1. Tng quan .............................................................................................................. 179 II.2. Tn tht in p ..................................................................................................... 180

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II.2.1. Trng hp 1 ph ti tp trung ....................................................................... 180 II.2.2. Trng hp c nhiu ph ti........................................................................... 181 II.2.3. Tnh ton tn tht in p li khi c ti phn b u ................................... 182 II.2.4. Tnh ton tn tht in p khi li c phn nhnh ......................................... 183 II.2.5. Tnh ton tn tht in p mng in c ti khng i xng ......................... 184

II.3. Tn tht cng sut.................................................................................................. 186 II.3.1. ng dy c 1 ph ti................................................................................... 186 II.3.2. ng dy c nhiu ph ti ............................................................................ 186 II.3.3. ng dy c ph ti phn b u ................................................................. 187 II.3.4. Tn tht cng sut khi ph ti c phn nhnh ................................................ 188 II.3.5. Tn tht cng sut khi ph ti bt i xng.................................................... 189

III. Cc phng php tnh ton tn tht p dng ti cc Cng ty in lc... 193 III.1. Tng qut:............................................................................................................. 193 III.2. Mt s phng php tnh tn tht in nng cho li in phn phi:................ 194

III.2.1. Cc phng php tnh ton:........................................................................... 195 III.2.2. nh gi cc phng php tnh ton: ............................................................ 198

IV. S liu tnh ton tn tht li in thnh ph H Ch Minh nm 2001.. 201 IV.1. Kt qu tnh tn tht in nng li truyn ti TP.HCM nm 2001: ................... 201 IV.2. Kt qu tnh ton tn tht in nng li in phn phi nm 2001. .................. 202

IV.2.1. Tn tht li phn phi h th: ..................................................................... 202 IV.2.2. Tn tht in nng li phn phi trung th: ................................................ 204

TI LIU THAM KHO:............................................................................ 207

CHNG 1: M HNH LI IN

7

CCHHNNGG 11:: MM HHNNHH LLII IINN

Phn mm PSS/ADEPT 5.0 l cng c hiu qu gip cho cc n v in lc phn tch v tnh ton li in trn a bn qun l. Qa trnh p dng phn mm cho thy, phn mm s dng rt tt cho cc qui trnh phn tch li in phn phi. Chng u ca gio trnh tp trung gii thiu hai ch chnh l li in phn phi v m hnh th hin cc phn t ca li in phn phi trong phn mm. Phn kin thc v li phn phi tr nn rt quen thuc vi cc in lc khu vc thuc cc Cng ty in lc, do vy c trnh by ngn gn. Phn m hnh ho cc phn t li in c trnh by chi tit. Khi kin thc ny rt quan trng, gip chng ta bc u tm hiu v qu trnh m hnh ho v li in trn my tnh. m bo tnh chnh xc v mt ton hc trong qu trnh m phng khng ch trn my tnh m cn th hin y cc tnh cht v in hc ca m hnh phn t li in c m phng.

M hnh ha v m phng bng my tnh ang l mt k thut c p dng cho tt c cc ngnh khoa hc k thut v kinh t. Nu trc kia vic thit lp mt m hnh, trin khai cc d ton, tnh ton thng k v trnh by s liu, i hi c kin thc v ton ng dng nhiu, gii cc phng trnh vi phn, tnh cc tnh tch phn, cc phng php thng k th hin nay vi s gip ca my tnh v nht l cc ngn ng lp trnh bc cao (nh Matlab, Mapple), cc kin thc ton ny tch hp hon ton trong cc hm v lnh ca cc ngn ng, to iu kin cho ngi dng tip cn trc tip v tp trung vo vn mnh nghin cu m khng phi dnh qu nhiu thi gian cho k thut lp trnh hay cng c ton l thuyt. Hin nay c hai phng php m phng m hnh ha cc phn t trong k thut m hnh ha bng my tnh. l m phng qua m hnh tnh ton v qua m hnh ha trc quan. V phng php m phng qua m hnh tnh ton ch cho php ngi dng thit k thnh nhng s n tuyn, thng dng trong cc phn mm k thut, i hi ngi s dng c nhng hiu bit c bn v lnh vc h ang nghin cu. i vi m phng qua m hnh ha trc quan th ngc li, phn ln cc phn mm i theo hng ny tp trung vo tnh ph bin, d s dng cho ngi dng. Tuy nhin, c hai phng php u c c im chung l ngi dng ch cn tp trung su vo cc ni dung k thut v thut ton gii bi ton. iu ny lm cho nhiu ngi khng c chuyn mn su v cng ngh thng tin c th gii quyt nhng vn ca chuyn mn mnh bng my tnh.

Phn mm PSS/ADEPT s dng phng php m phng qua m hnh tnh ton. Cc phn t trn li in c m hnh ch nhng ngi lm vic trong ngnh mi s dng uc. Ngi s dng ch cn hiu su v vn k thut v cc

8

thut ton v tnh ton phn b cng sut, ngn mch, b cng sut v.v..V l th mnh ca cc phng php m phng thng qua cc m hnh bng my tnh.

II.. LLii iinn pphhnn pphhii Li h thng: Li h thng bao gm cc ng dy ti in v trm bin

p khu vc, ni lin cc nh my in to thnh h thng in, c cc c im:

- Li c nhiu mch vng kn khi ngt in bo qun ng dy hoc s c l n 2 ng dy vn m bo lin lc h thng.

Vn hnh kn bo m lin lc thng xuyn v chc chn gia cc nh my in vi nhau v vi ph ti.

- in p t l10 kV n 500 kV.

Li truyn ti: Li truyn ti lm nhim v ti in t cc trm khu vc n cc trm trung gian (TTG). Cc c im ca li truyn ti:

- S kn c d phng: 2 l song song, c d phng li phn phi. Vn hnh h v l do hn ch dng ngn mch. c thit b t ng ngun d tr khi s c. in p 35, l10, 220 kV.

Thc hin bng ng dy trn khng l chnh, trong cc trng hp khng th lm ng dy trn khng th dng cp ngm. Phi bo qun nh k hng nm.

Li phn phi: Li phn phi lm nhim v phn phi in nng t cc trm trung gian (hoc TKV hoc thanh ci nh my in) cho cc ph ti.

+ Li phn phi gm 2 phn

- Li phn phi trung p c in p 6,10,15,22kV phn phi in cho cc trm phn phi trung p / h p v cc ph ti trung p.

Li h p cp in cho cc ph ti h p 380/220 V.

i tng quan tm chnh ca gio trnh tp hun ny l li in phn phi, sau y trnh by kin thc n tp v li in phn phi.

Hnh 1: S khi cp in p

9

Hnh 2: Li in truyn ti cao th

II..11.. LLii iinn pphhnn pphhii c im chnh ca h thng li phn phi l cung cp in trc tip n

ngi s dng. Trong cng cuc pht trin t nc hin nay, vic cung cp in nng l mt trong nhng ngnh quan tm hng u ca Chnh Ph ni chung v ca Thnh Ph ni ring. V vy m bo cht lng in nng th vic nghin cu, thit k h thng li in phn phi l ht sc quan trng.

H thng phn phi in nng c xy dng v lp t phi m bo nhn in nng t mt hay nhiu ngun cung cp v phn phi n cc h tiu th.

Li phn phi trung p c in p 6, 10,15,22, 35KV phn phi in cho cc trm phn phi trung h p, li h p 220/380V cp in cho cc ph ti h p.

Hnh 3: Li in phn phi trung th

10

Hnh 4: Li in phn phi h th

Hnh 5: Trm h th

m bo cung cp in tiu th t gy ra mt in nht. Bng cc bin php c th nh c th c nhiu ngun cung cp, c ng dy d phng, c ngun thay th nh my pht

Li in phn phi vn hnh d dng linh hot v ph hp vi vic pht trin li in trong tng lai.

m bo cht lng in nng cao nht v n nh tn s v n nh in p. bin thin in p cho php l 5% Um

m bo chi ph duy tu, bo dng l nh nht.

II..22.. CCcc llooii ss hh tthhnngg llii pphhnn pphhii:: Khi thit k xy dng li phn phi c th chn mt trong cc h thng in

chnh sau:

H thng hnh tia n gin.

H thng hnh vng pha cao p hnh tia pha h p

11

52

52 5252 5252 52

Trm bin p pha th cp

Cp truyn ti

My ct ng dy pha s cp

My ct chnh

H thng chn lc pha cao p h thng chn lc pha h p.

Hai ngun pha cao p h thng chn lc pha h p.

H thng mang hnh nt.

II..22..11.. SS hhnnhh ttiiaa::

* iu thun li hnh tia n gin nhn in cp in p c bn ti mt trm n v h in p xung cp s dng.

Trong trng hp ny khch hng nhn in t h thng cao p v thng qua c cu ng ct cao p, my bin p cng vi t phn phi pha h p, thit b c th tho ra bng cu dao, cch ly pha cao p, cch ly my bin p v cch ly t phn phi pha h p. ng dy pha h p chy t t phn phi ni vi cc Panelboard, y l ni tip nhn ti ca n. Mi ng dy c ni vi t phn phi thng qua my ct hay thit b qu dng.

T ng ton b ti c cung cp in t mt ngun n, iu thun li y l c th cp in cho nhiu loi ti khc nhau lm gim ti a vic lp t my bin p. Tuy nhin st p cao v hiu qu s dng li thp bi v nhng ng dy cp in bn h p l ngun cung cp n. Gi thnh ca ng dy v my ct bn h p rt cao khi dy dn v cng sut MBA trn 1000KVA.

Khi c s c thanh ci th cp hay trong my bin p ngun th s ct ton b ti. Khng th phc v cp in cho n khi vic sa cha kt thc. S c ng dy h p s ct ton b ti trn ng dy .

Mt s hnh tia ci tin c th cung cp in tt hn cho h tiu th c trnh by trong s sau y:

Hnh 6: Mt s hnh tia ci tin

12

II..22..22.. SS hhnnhh ttiiaa cc ccii ttiinn

T my bin p chnh, cc ng dy c ni n cc trm h p thng qua nhng my ct phn phi. Mi vng ph ti s nhn c in nng t trm h p n v. in p cao tng bc c h xung cp in p thp hn ph hp vi tng ph ti. My bin p c ni n cc thanh ci ph ti ca chng thng qua mt my ct.

Mi trm h p n v l s kt hp gia my bin p ba pha, cu ch bn cao p v t phn phi bn h p. Tt c c ni vi my ct hoc cu ch. Nhng mch ny c kt ni vi ti qua nhng thit b bo v.

Mi my bin p xc nh r mt vng ph ti v phi c kh nng p ng trong trng hp ti ln nht. Nu c bt k s thay i gia cc vng ph ti, i hi cc my bin p phi c cng sut ln hn so vi trong trng hp s hnh tia n gin. Tuy nhin do cng sut c phn phi n ti in p cao nn tn tht in nng, chi ph lp t gim xung, n nh in p c ci thin.

So vi s hnh tia cha ci tin, s ny s gim c chi ph u t khi cng sut yu cu ln hn 1000kVA. Mt s c pha th cp hoc my bin p phn phi ch lm mt in trong phm vi ph ti m my bin p m trch.

Vic gim s lng my bin p trn ng dy pha s cp s lm tng tnh linh hot cung cp in ca h thng. Ti u ha v vn hnh cng nh chi ph lp t h thng phi c tnh ton sao cho mc an ton v tnh lin tc cung cp in nm trong cc tiu chun ra.

Hnh vng pha cao p hnh tia pha h p:

H thng ny bao gm mt hay nhiu vng pha cao p vi hai hay nhiu my bin p ni trn mt vng. H thng ny l loi c hiu qu nht. Khi c hai vng phc v khng nh hng n nhau.

13

Hnh 7: S hnh vng pha cao p - hnh tia pha h p Mi vng pha cao p c vn hnh khi c mt cu dao phn on v tr m

ngn s hot ng song song ca nhng ngun. Khi trm n v bn h p c dng, mi my bin p c hai dao cch ly phn on v cu ch ca ti bn cao p. Bng cch ng cu dao phn on thch hp, n c th khng ni vi mt vi phn cn li ca h thng. Bng cch m c cu ng ngt my bin p, n c th khng ni mt vi my bin p ca vng.

C cu kho thng c dng ngn nga s hot ng song song ca hai ng dy ngun. Mt c cu t ng c th c iu khin gia hai my ct chnh v my ct lin kt.

S ny rt m bo v phc hi nhanh chng khi c s c:

1. Vic cch ly thit b c bn xy ra trn mt ng dy n, my ct chnh lin quan c m ra v sau my ct lin kt c ng li c th bng tay hay bng c cu chuyn i t ng.

2. Khi mt ng dy pha cao p b s c, my ct vng lin quan c m ra v thit b ct ton b ti tnh n dao cch ly vng thng m. Xc nh chnh cc phn cp b s c, sau dao cch ly phn on vng khc ng li v vic cp in cho trm n v h p c phc hi trong khi ng dy b s c c thay th.

3. Nu s c xy ra trn ng dy dn n pha ti ca mt my ct ng dy vng, my ct vng s c gi v tr m sau khi n ct v dao cch ly phn on c thao tc m ra v th on dy s c c th c phn ra v thay th.

52 52

52

5252 5252

NC

NC

NC

NO NC

NO

NC

NC

NC NC

My ct phn on My ct chnh

pha s cp

Mch vng Cm bin pht hin s c

My ct chnh pha s cp

14

Di tnh trng ny tt c cc trm n v h p c cung cp thng qua mt my ct ng dy vng khc. V th tt c ng dy ni ca vng phi c chn cung cp cho ton b ti ca vng y.

4. Khi my bin p b s c hay b qu ti, cu ch cao p ca my bin p s chy ra, v sau c cu ng ngt c thao tc m ra, khng ni my bin p vi vng na v vic tch ra vi tt c cc ti ca nhng trm n v khc khng b nh hng.

IIII.. MM hhnnhh llii iinn ccaa pphhnn mmmm PPSSSS//AADDEEPPTT 55..00 PSS/ADEPT lm vic vi m hnh h thng ba pha, bn dy vi dng tng

qut. H thng c m t bng cc thnh phn tng tr cn bng th t thun v th t khng. Cc phn t trong h thng in c m phng bao gm:

Cc nt Ngun ba pha cn bng v khng cn bng ng dy v thit b ngt My bin th ng c v my pht Ti Cc phn ng dy, thit b ngt, v my bin th ca h thng hnh thnh

kt ni gia cc nt. Ngun, ti, v cc t shunt c gn ti nt.

Ba pha ca h thng l c t tn l A, B, v C. Tt c ba pha, hai pha, hay mt pha c th th hin trong mi ng dy hay my bin th. V vy c th m hnh mt pht tuyn phn phi t mt ngun ba pha, vi mch chnh ba pha, vi cc nhnh r hai v mt pha, v vi ti ba, hai, v mt pha. Nu h thng ni t ti trung tnh th PSS/ADEPT gi thit rng dy trung tnh lin tc, c kt ni tt, v c kt ni ti tt c nt. H thng khng ni t c th c m hnh trong PSS/ADEPT bng cc qui cch k thut thch hp ca my bin th v cc tng tr ng dy, v quy cch k thut thch hp ca cc loi ti.

IIII..11.. NNtt Tt c cc mi ni ca thit b c qui nh l nt. Mi nt trong m hnh

h thng PSS/ADEPT bao gm:

im trung tnh (nu c ni t) Ba, hai, hay mt im ca pha A, B, v C

15

Cc pha c trong mt nt c xc nh bng s hin din ca chng trong ng dy, my bin th, hay thit b ngt nui n, v khng c qui nh nh l thuc tnh ca cc nt. Do , mt nt c th bao gm ban u ch mt im pha A, v sau cc im pha th hai v ba theo h thng nui n khi c nng cp t mt ln nhiu pha.

Hnh 8: M hnh nt

Mi im nt phi c t mt tn c t mt n tm k t. Tn ny c th l s, s v ch, hay mt chui k t. Tn nt c th c t theo s nht qun vi c s d liu ca ngi s dng. Tn nt khng c din dch v s lng hay ch v mc ch bo co hay lit k danh sch d liu.Ngoi ra, th t lit k cc nt c qui nh bng cch lit k chng mt cch tun t trong file d liu th ba pha. Th t tn nt c lit k trong file s thc hin vic thit lp th t tn nt lit k trong bo co, v nh hng n th t nhnh r trong bn s topo v c gii thch trong phn k.

IIII..22.. NNgguunn Nhiu ngun c th c s dng cng lc trong PSS/ADEPT. Tuy nhin, h

thng phi c t mt ngun hot ng (chng hn, mt nt c bin in p th t thun l hng s v gc l hng s). Ngun l tp hp cc ngun p ni sao cn bng c ni t c nh ti im trung tnh. Ngun c tng tr sao cho n c dng th t thun v khng.

Trong bi ton phn b cng sut, ngun c xem l c in p hng s trong th t thun, b qua tng tr th t thun. Trong tnh ton khi ng ng c v ngn mch, ngun c xem l c in p hng s sau khi nhp vo tng tr trong th t thun. Tng tr th t nghch v khng c s dng cho tt c cc tnh ton.

IIII..22..11.. NNhhiiuu nngguunn hhoott nngg

V d khi ngi s dng PSS/ADEPT mun phn tch h thng c nhiu hn mt mt ngun hot ng, chng hn, trong nghin cu k hoch phn phi. Mc d PSS/ADEPT ch cho php mt ngun hot ng th c vi k thut m hnh h thng c nhiu ngun hot ng.

16

K thut n gin l gi li mt ngun nh nt ngun v m hnh ngun cn li nh cc my cng pht tng ng, ngha l cc my in ng b c ti kW m. D liu th t ca cc ngun ny l c phn nh trong d liu th t ca cc my cng pht ring tng ng.

IIII..22..22.. NNgguunn 33 pphhaa

Mt ngun 3 pha bao gm 3 ngun in p 1 pha c u ni hnh Y. Mi ngun in p 1 pha c tr khng v gi tr in p xc nh. Ngun 3 pha c cng bin in p c 3 pha nhng cc pha lch nhau 1200 v 3 tng tr pha cng bng nhau. Mt ngun 3 pha cn c th hin qua tng tr tng th t thun, nghch v zero.

Hnh 9: Cc thnh th t ca ngun 3 pha

M hnh mt ngun 3 pha c trnh by hnh 10. Ngun c th ni vi tng tr t Zg = Rg + jXg, mi cun dy ca mi pha c tr khng ring l Zs v tr khng h cm gia 2 pha l Zm. Chng ta c 2 cch tnh ton mt ngun: mt l thng m hnh 3 pha ABC hoc thng qua cc tr khng th t thun, ngch v zero. C 2 cch u c s tng ng ln nhau. Tr khng th t thun Z1=ZsZm v th t 0 l Z0=Zs+2Zm, tr khng th t nghch Z2=Z1. Khi ngun c ni vi t, tng tr th t 0 c xc nh l Z0=Zs+2Zm+3Zg

17

Hnh 10: M hnh ngun 3 pha

IIII..33.. PPhh ttii Ph ti chnh l cc khch hng s dng in. C 2 loi: ph ti 1 pha v ph ti

3 pha v c biu din nh hnh 11 di y:

Hnh 11: M hnh ti 1 pha v 3 pha

Ph ti trong PSS/ADEPT c th ni gia 2 node (line-to-line or line-to-neutral) hoc gia pha v t (line-to-ground). Mt node trong PSS/ADEPT c th t c nhiu ph ti (khng hn ch). Ph ti 3 pha ni Wye cn c tr khng t Rg+jXg

Cc ti tnh c th c qui nh l c cng sut bng hng s, tng tr hng s, hay c tnh dng l hng s. Ngoi ra, ti c th c qui nh c ni t hay khng ni t. i vi loi ti c ni t, ti c nu trong PSS/ADEPT nh

18

c kt ni gia pha v trung tnh, trong khi , ti khng ni t c nhp vo trong pha A th thc t l c kt ni gia pha A B, ti khng ni t nhp vo trong pha B l c kt ni gia pha B C, v ti khng ni t nhp vo trong pha C l c kt ni gia pha C A. V th, pha thch hp cn phi hin th trn nhnh ni vi nt m ti khng c ni t c qui nh.

IIII..44.. TT bb Chng ta kho st t b ngang nh sau:

T b ngang dng gim st p trong mt vng xc nh bng cch pht cng sut khng ln ng dy. Ngoi ra, b ngang cn lm tng kh nng truyn ti trn li, gim tn tht cng sut v nng cao h s cng sut.

Cc t b ngang thng c lp t thnh cc gin t b v d dng trong vic ng ct cc t khi vn hnh li in.

T b ngang 3 pha c 2 cch u ni l sao v tam gic Y. Trong trng hp u Y, trung tnh c ni vi tr khng t Rg+jXg

Hnh 12 M hnh t b ngang

IIII..55.. nngg ddyy on dy chy gia hai nt. Mt on dy lun bao gm t nht mt dy pha.

N c th c mt, hai, hay ba dy pha. Mt on dy thng bao gm mt dy trung tnh, nhng dy trung tnh c th khng c trong trng hp ca h thng khng c ni t.

ng dy truyn ti c qui nh bng cc tng tr i xng th t thun v khng, v bng cc gi tr np th t thun v khng. V vy, tnh bt i xng ca ng dy truyn ti do v tr ca cc dy dn trn tr khng c th r rng i vi PSS/ADEPT; ng hn l tt c cc ng dy c gi thit l c hon v hay cc dy dn c t sao cho c th b qua s bt i xng.

19

Cc on dy mt hay hai pha phi c qui nh nh th n l ng dy ba pha vi cc pha b mt. V th, nu mt ng dy hai pha c xy dng nh hnh 13a, tng tr th t thun v khng ca n phi c qui nh nh th n c xy dng nh hnh 13b. Tng t, ng dy mt pha c xy dng nh hnh 13c phi c qui nh nh th n l ng dy ba pha c b tr nh hnh 13d.

Hnh 13 M hnh cc ng dy

IIII..66.. MMyy bbiinn tthh PSS/ADEPT c kh nng m hnh nhiu loi kt ni my bin th k c my

bin th lc, my bin th t ngu, b iu p v my bin th ba cun dy. Mt s kt ni my bin th l c m hnh ngm trong PSS/ADEPT v c phn bit bi m LOI my bin th nh c trong hnh 14. i vi mi loi kt ni c minh ho, PSS/ADEPT chp nhn d liu tng tr th t thun v khng t T in xy dng hay Tp tin d liu th v t ng s dng cc in p v dng in khi gii bi ton kt ni my bin th. Ngi s dng c trch nhim qui nh tng tr m c tng tr tht ca dy my bin th hp l trong cc kt ni c bit.

Cc kt ni my bin th m c th khng c m t trc tip bng mt trong cc loi c cho trong hnh 14 thng c th c m hnh bng cch kt hp ca cc m hnh tuyt i. Chng hn, m hnh mt dy my bin th ba pha, cn thit phi nhn bit c cch m tng my bin th mt pha ring l c kt

20

ni, v xy dng ln mt m hnh in tng ng s dng 1, 2, hay 3 m hnh my bin th ring l v cc gi tr thch hp cho cc tng tr th t thun v khng ca dy. My bin th ba cun dy c th c trnh by trong PSS/ADEPT dng m hnh sao tng ng.

IIII..66..11.. MMyy bbiinn tthh llcc

Cc loi my bin th 1, 2, 3, v 11 s dng cc kt hp thch hp ca hai dy tng ng c trnh by trong hnh 14. Tng tr th t ca my bin th c m hnh theo kiu ngc li v tr iu p ca my bin th v vn khng i bt k v tr ca iu p. Cc my bin th ba, hai, hay mt pha c in p c bn s cp l khc in p c bn th cp phi c a ra bng cch s dng cc loi my bin th .

21

Hnh 14 M hnh cc my bin p

T s vng dy n v ca my bin th, t, phi l

nom

nom

nnn

nt

1

1

2=

trong

n1nom S ca cc vng dy cun s cp c in p h mch bng vi in p c bn ca nt s cp vi thng lng nh mc trong my bin th.

n2nom S ca cc vng dy cun th cp c in p h mch bng vi in p c bn ca nt th cp vi thng lng nh mc trong my bin th.

n1 S vng thc t ca cun s cp.

n2 S vng thc t ca cun th cp.

Mt nh ngha khc ca t l vng dy, t, l

nom

oc

nom

c

nn

nv

t

1

1

2

20

=

Trong

V1oc in p tng ng vi v tr nc iu p s cp vi thng lng nh mc trong my bin th.

22

V2oc in p tng ng vi v tr nc iu p th cp vi thng lng nh mc trong my bin th.

V1nom in p tng ng vi nc iu p s cp danh nh vi thng lng nh mc trong my bin th.

V2nom in p tng ng vi nc iu p th cp danh nh vi thng lng nh mc trong my bin th.

Trong hu ht nhng khng trong tt c cc trng hp, V1nom v V2nom s bng cc in p c bn ca cc nt m cc cun dy s cp v th cp kt ni.

Bt chp vic kt ni ca dy my bin th hay v tr vt l ca cc nc iu p trn cc cun dy s cp v th cp, PSS/ADEPT yu cu v tr nc c nh r bng t l cc vng dy n v thc t, nh c nh ngha trn. Bi v t l cc vng dy n v lin kt in p s cp v th cp vi cc gi tr in p danh nh ca cc in p , h s 1.7320508 (3) khng xut hin trong t l cc vng dy c qui nh cho cc dy sao tam gic hay tam gic sao trong PSS/ADEPT. V vy t l cc vng dy n v ca mt my bin th c kt ni cho:

13.8 kV pha-pha v 7.969 kV pha-t s cp 4.8kV pha-pha v 2.771 kV pha-t th cp

Hnh sao s cp-tam gic th cp c kt ni, v c iu p cng 5% pha th cp l

(4.8 * 1.05/4.8)/(13.8/13.8) = 1.05 n v Trong khi t l cc vng dy thc t cho mi my bin th ring l l

(4.8 * 1.05)/(13.8/1.7320508) = 1.05 * (4.8/7.967) Khi dy my bin th ba pha l c hnh thnh t ba my bin th mt pha

ring l trong mi bn du ca n, cc tng tr th t thun v khng ca dy thng thng phi ci t bng tng tr r n v ca mt my bin th ring mt pha kVA c bn. (Ghi ch: kch c my bin th lun lun c qui nh trong PSS/ADEPT theo kVA/pha v tng tr c nhp vo theo n v c bn my bin th). Khi my bin th c ch to vi cc cun pha cho ba pha trn mt li n, cc tng tr th t thun v khng ca tng n v bnh thng s c cho trong bn tn ca n v c th c qui nh trc tip trong PSS/ADEPT, v kch thc my bin th phi c nhp PSS/ADEPT nh mt phn ba nh mc tng kVA.

T ng x l kt ni dy my bin th trong PSS/ADEPT c p dng ch khi tt c cc my bin th ring bit c kt ni thnh dy l c cng kch thc. Khi s dng cc my bin th pha c kch thc khng ng u, cn thit phi a ra cc nt o cho phn ci t PSS/ADEPT, v a ra cch trnh by dy khng i xng bng hai hay nhiu kt ni.

23

Ngi s dng cn phi nhn bit v qui nh c kt ni c dng trong dy my bin th v pha ca n. Pha c qui nh qua PSS/ADEPT c tham chiu ti quy c. Trong quy nh pha:

Cc pha A, B, v C l lun lun c xc nh bi cc s 1, 2, v 3, tng ng.

Cc cp pha AB, BC, v CA l lun lun c xc nh bi cc s 1, 2, v 3, tng ng.

Cc my bin th ring bit, hay cc cp cun dy trong my bin th ba pha lun lun c cp i vi cc pha A, B, v C. Chnh l, cun dy A-n-trung tnh lun lun c cp vi A-n-trung tnh hay cun A-n-B tng ng, v.v Ch c s thay i pha +30 trong my bin th sao-tam gic c th c m hnh vi PSS/ADEPT; cc s sp xp thay i pha 120 c th c bng cch cp cun dy A-n-trung tnh/cp dy B-n-C chng hn, l khng c nhn bit.

S chuyn i pha t 30 ti m 30 l c c bi o du m loi my bin th.

IIII..66..22.. MMyy bbiinn tthh llcc cc kktt nnii tthhnnhh mmyy bbiinn tthh tt nngguu

My bin th lc c kt ni trong cu hnh t ng phi c m hnh bng cch s dng loi 1, 2, 3, hay 11.

Tng tr ca my bin th t ngu t hn ca mt my bin th c kt ni trong cu hnh hai cun dy thng thng v v vy nn c nhp vo PSS/ADEPT mt cch thch hp. Cng vy, vic chuyn i kVA ca mt my bin th t ngu c tng nh c so snh ti my bin th hai cun dy chun v phi c nhp vo tng ng. Thay i cp ti t ng

My bin th lc c th c m hnh vi b iu ti (LTC) trong PSS/ADEPT. Cch thc iu chnh LTC c nh r nh vo tnh trng nhnh ca my bin th.

Mi my bin th trong PSS/ADEPT c th c cho mt dy mc tiu in p, t l cc vng dy cao nht c th n v, v t l cc vng dy thp nht c th, v bc iu p n v. Cc my bin th c th c thit k trc tip iu khin in p ti nt s cp hay th cp ca n. Nt TO trong h s minh ha nt no c hiu chnh mc nh. Cch khc, mt my bin th c th c m hnh iu khin in p ti mt nt xa qui nh t v tr my bin th xung ng dy hay gi cho in p nt TO b p ri trn dy. Tt c cc my bin th iu p, t l cc vng dy n v l c iu chnh, trong gii hn qui nh, gi in p gim st hay b trong dy mc tiu nh.

24

i vi cc my bin th LTC, cc iu p c th c t pha cao hay pha h p. Ngi s dng c th qui nh v tr t bng cch xc nh im nt TO trong d liu my bin th l pha iu p, nh c trnh by trong hnh 15

Hnh 15 Xc nh nt TO trong d liu my bin p

My bin th iu chnh in p vi cun dy ni sao v tr TO ca n s lun iu chnh in p pha-trung tnh. My bin th iu chnh in p vi cun dy ni tam gic v tr TO ca n s lun iu chnh in p pha-pha.

B b in p ri trn ng dy l mt dng c m hnh thay i in p th cp my bin th trc khi n n sensor in p. Chc nng ca b b in p ri ng dy l cho in p c nh trc tng ln gim bin ng in p dc ng dy do thay i ti n mc ti thiu.

B in p ri ng dy c thc hin bng cch tnh ton cc in p biu kin cho bi

VAPP = (in p pha-t nt TO) ZCOMP * (dng pha TO) i vi mi pha v sau xem xt bin ca VAPP (AN, BN, hay CA) cho

my bin th ni sao hay ca VAPP (AB, BC, hay CA) cho my bin th ni delta.

iu p tng ng c di chuyn nu in p biu kin di dy c qui nh trong d liu my bin th hay n c i chuyn tr xung ngc li.

Nu s dng nt xa, cc tng tr n b s c tnh ton ngi s dng xem xt. Ghi ch, tng tr n b ng trc trn iu khin nt xa.

Dy mc tiu in p ca my bin th khng c hp hn kch thc ca bc iu p my bin th, v iu ny c th khin cho vic iu chnh in p my bin th phi tm kim tip tc. Dy in p hp l quy c l mt phn trm i vi my bin th c bc 5/8%.

IIII..66..33.. BB iiuu pp

Ngc vi my bin th lc thay i bc in p t bc ny ti bc khc, B iu p n thun tng hay gim in p th cp theo yu cu bi cc iu

25

kin ti. Cc b iu p hin i thng cung cp mt dy +10% in p iu chnh trong cc bc 32/0.00625. y l cc gi tr mc nh cho vic iu chnh my bin th trong PSS/ADEPT. Cc loi my bin th 4 ti 10 v 12 ti 15 l cc m hnh tuyt i c dng cho cc b iu p gii thiu. Tng tr ca cc my bin th ny l c chnh i vi v tr iu p ngc vi cc loi 1, 2, 3 v 11 vi tng tr l hng s. Tng tr l c m t l zero lc b i nc my bin th l danh nh v b iu p cho c tnh dng thng. Lc b iu p ti mc in p y th s s dng tng tr nhp vo. i vi cc b chuyn i trung gian, in tr l mt hm ca s vng dy, v in khng l mt hm ca cc vng dy bnh phng.

B iu p c nh mc quy c theo kVA iu chnh hay amp.

V d, mt b iu p ba pha, +10%, 750 kVA thc s c th c p dng cho mch ba pha nh mc 8250 kVA v c th thay i in p ng dy dng hay m 10% nh mc. Nu c p dng ti mt pht tuyn c bn 13.2 kV, dng nh mc s l:

A.kV.

kVA 328102133

750 Tng nh mc kVA ba pha ca b iu p l:

( ) kVAA.kV. 8250328112133 = nh mc mt pha phi c nhp vo m hnh PSS/ADEPT:

kVAkVA 27503

8250

Tng tr ca mt b iu p c bit rt nh v cu hnh t ng c dng. V d minh ho nh th no tnh gn ng tng tr ca b iu p c m t trn: Nu my bin th c kt ni nh my bin th hai cun dy tiu chun, ta s c cho mi pha:

Hnh 16 M hnh b iu p My bin th phn phi quy c c tng tr khong 2%. Ngha l, nu th cp ca my bin th trn b ngt mch, tng tr ca my bin th khong chng 2% trn c s 250 kVA v in p nh mc 0.762 kV. Nu my bin th c kt ni trong cu hnh t ng, ta c:

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vi tng kVA l 2750 cho tng pha. Vi th nghim ngn mch nh trn, cng tng tr s c xc nh, tuy nhin, c bn mi l 2750 kVA v 8.38 kV. V vy, tng tr trn cc gi tr c bn l:

( ) ( )( ) %.kV.kV.

kVAkVA%X 180

3887620

25027502 2

2

==

Gi tr 0.0018 phi c nhp vo i vi khng th t thun (X1) trong PSS/ADEPT m hnh b iu p ny. Gi thit rng b iu p c ni t c nh, khng th t khng(X0) s c cng gi tr.

II.6.3.1. M hnh tng tr trung tnh trong my bin th

M hnh tng tr trung tnh ca mt my bin th c x l trong PSS/ADEPT bng cch chnh i tng tr th t khng my bin th. Mt my bin th c ni t c nh, tng tr th t khng (Z0) l ci t bng tng tr th t thun (Z1). Khi tng tr trung tnh c (Zg), tng tr th t khng c nh ngha nh sau y:

Z0 = Z1 + 3Zg

V tng tr cn phi c nhp vo theo n v trong PSS/ADEPT, tng tr trung tnh cn phi chuyn i thnh n v c bn kVA ca my bin th v in p c bn ca cun dy m tng tr ni t c kt ni.

V d sau phc tho th tc tnh ton tng tr th t khng ca my bin th ba pha, 12 MVA, 69 kV/13.2 kV, 8%, ni tam gic sao vi in tr trung tnh 10 ohm: Trn c bn my bin th chng ta c: Z1 = 0.0+j0.08p.u. Chuyn i tng tr ni t (Rg) thnh n v nh sau:

II.6.3.2. My bin th 3 cun dy

Mc d PSS/ADEPT khng c cc m hnh ring cho my bin th ba pha, chng c th c m hnh chnh xc dng tng ng hnh Y. Cc thng s tng ng c th c t nh sn xut hay t mt th nghim. Trong phn th nghim ny, mt cun dy c ngn mch v mt h mch trong khi mt in p c p dng cho cun dy cn li. Th nghim ny cho ta bit ba tr khng r

27

r biu kin khi trn in p c bn ca tng cun dy tng ng v c bn MVA chung, cc tng tr ny l: Zlh, Zlt, v Zht.

Lin h cc tng tr ny vi mch tng ng, Zlh l tng ca tng tr r r cun dy in p cao v thp Xi+Xh, v.v

Cc thng s th nghim ny l c o ti v tr nc iu p danh nh, theo, c lin quan n tng tr nhnh iu p danh nh ca mch tng ng, nh c thit k trong hnh 17 bi:

ZLH = Zl+Zh ZLT = Zl+Zt ZHT = Zh+Zt

Bi ton yu cu l: Zl = (ZLH+ZLT-ZHT)/2 Zh = (ZLH+ZHT-ZLT)/2 Zt = (ZLT+ZHT-ZLH)/2

Trong tt c cc tng tr l dng n v i vi cng mt c bn kVA.

Hnh 17 M hnh my bin p 3 cun dy

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Hnh 18 M hnh tng ng my bin p 3 pha 3 cun dy

Cc tng tr Zh, Zl, v Zt l th t thun c xc nh nh trnh by trn. ZNh, ZNl, v ZNt l cc tng tr ni t n v ca cun dy cao, h v th ba tng ng. V vy, nu cun dy hnh sao c ni t c nh, ZN bng 0. Nu cun dy hnh sao khng c ni t ZN l v cc.

V d nh nh mc ba pha ca my bin th ba cun dy l: S cp ni Y, 66 kV, 1500 kVA, ni t c nh. Th cp ni Y, 13.2 kV, 1000 kVA, 10 ohm in tr ni t. Th ba ni , 2.3 kV, 500 kVA Cc thng s th nghim l:

ZHL = 0.004 + j0.07, c bn 1500 kVA, 66-kV ZHT = 0.005 + j0.09, c bn 1500 kVA, 66-kV

ZLT = 0.005 + j0.08, c bn 1000 kVA, 13.2 kV Chuyn i ZLT thnh c bn cun dy pha cao kVA:

dng n v trn c bn 1500 kVA, ta c:

i vi th t khng:

Trong PSS/ADEPT mi nhnh ca ba cun dy tng ng c th hin bi mt my bin th ni ti nt o. in p ca nt o l tu .

29

i vi v d trn, cc kt ni c trnh by trong hnh 19

Hnh 19 V d mt my bin p 3 pha 3 cun dy

II.6.3.3. My bin th ni t

Trong mt h thng khi th cp hon ton c kt ni delta, khng c ti mt pha v h thng trung tnh ni t khng tn ti. Trong h thng , khi c ngh phc v ti mt pha, cc my bin th ni t c dng thit lp mt h thng trung tnh ni t. Hu ht cc loi my bin th ni t thng thng l loi sao-tam gic hay zig-zag. C hai loi cung cp mt ng dn tng tr thp cho dng th t khng v ng dn tng tr cao cho s ci t c cn bng cc dng ba pha v c th m hnh trong PSS/ADEPT dng my bin th lc sao-tam gic. V tr hnh sao ca my bin th cn phi c kt ni ti h thng delta nh c minh ha di cung cp ng dn cho dng t. Th cp tam gic ca dy ni t c th c ti, nhng thng th khng.

Hnh 20 My bin th ni t

Tng pha kVA v bn tn cc tng tr ca my bin th ni t phi c nhp vo trc tip trong PSS/ADEPT cho cc loi hnh sao tam gic. Tuy nhin cho cc loi zig-zag, nu kch c kVA l nh mc ca cun dy ring l ca nhnh, kVA phi c nhn 3 khi nhp vo trong PSS/ADEPT. Cch khc, lun lun

30

nhp vo tng dung lng kVA mt pha ca dy. Cho hai loi my bin th ni t, bt k tng tr trung tnh no phi c m hnh trong PSS/ADEPT bng cch hiu chnh tng tr th t khng.

II.6.3.4. My bin th lc 1 pha

My bin th lc mt pha c th c m hnh trong PSS/ADEPT bng cch dng loi 1(sao-sao), 2 (sao-delta), 3 (delta-sao) hay 11 (delta-delta) v qui nh pha nhnh thch hp. nh mc mt pha kVA phi c nhp vo trong PSS/ADEPT vi bn tn cc tng tr. Sau y minh ho vi loi my bin th lc mt pha v tho lun cch trnh by trong PSS/ADEPT v cc s hn ch t bit c th p dng:

M hnh my bin th loi 1(sao-sao) v qui nh pha nhnh l pha my bin th kt ni. Pha nhnh phi l B i vi v d cho. Ghi ch, tt c ti c nui bi my bin th ny phi c ni t v ch nhp vo trong pha i vi my bin th c kt ni.

M hnh my bin th loi 3 (tam gic-sao) v qui nh pha nhnh l pha hin hu pha sao (dy-trung tnh) ca my bin th. Pha nhnh phi l A cho v d nu v pha AB cn phi tn ti pha s cp ca my bin th.

Tt c ti c nui bi my bin th ny phi c ni t v ch nhp vo pha c qui nh cho pha nhnh my bin th.

M hnh my bin th loi 2 (sao-tam gic) v qui nh pha nhnh l pha hin din pha sao (dy-trung tnh) ca my bin th. Pha nhnh phi l A cho v d nu v pha A phi tn ti pha s cp my bin th.

Tt c ti c nui t phn th cp phi khng c ni t, c kt ni gia hai pha c ni t my bin th. i vi v d minh ho, ti th cp phi l loi khng c ni t v ch nhp vo trong pha A.

II.6.3.5. My bin th lc hnh sao m ti tam gic m

Kt ni my bin th hnh sao m ti hnh tam gic m cho php ti ba pha c phc v bi pht tuyn hai pha ni t nh c trnh by y:

Hnh 21 My bin p lc hnh sao m

31

My bin th ny c theo m hnh trong PSS/ADEPT cho tnh ton dng cng sut v khi ng ng c. Cc s tnh ton ngn mch cho nt pha th cp ca loi my bin th ny khng c x l thch hp bi cc thut ton PSS/ADEPT.

My bin th hnh sao m ti hnh tam gic m phi c m t trong PSS/ADEPT bng cch qui nh mt my bin th loi 2 (sao tam gic) vi pha nhnh my bin th c nh ngha l c hai pha pha sao ca my bin th. i vi v d c trnh by trn, pha nhnh my bin th phi nhp vo nh AB. Cc b tr pha hp l l:

Cc pha c qui nh cho my bin th cn phi tn ti trn nt chnh. Tt c ti ni t my bin th ny phi qui nh khng c ni t.

nh mc kVA ca my bin th mt pha phi nhp vo trong PSS/ADEPT cng vi tng tr qui nh trn kVA c bn.

IIII..77.. MM hhnnhh mmyy iinn Cc my in ba pha ng b v khng ng b c th c m hnh r rng

vi PSS/ADEPT. C hai loi c th c thit k nh my pht in hay ng c bng cch la chn du hiu thch hp cho thng s ti kW trong h s d liu ti th. Cc c tnh c trng ca my in c m hnh bi PSS/ADEPT phi c nhp vo trong Tp tin T in D liu My in. Cc loi ti l c dng phn bit cc loi my in:

Cc loi my in khng ng b:

Loi ti 51 70, 151 170 c nhp vo theo kW

nh mc theo kVA. Loi ti 71 90, 171 190 c nhp vo theo hp c

nh mc theo hp c. Cc loi my ng b. Loi ti 91 99, 191 199 c nhp vo theo kW

nh mc theo kVA

My in c th c m hnh ti nt ba pha trong bt k nhm ti no. My in c xem nh trc tuyn lc loi ti l dng. Bng cch thm du m loi ti (chng hn nh -51), my s c xem nh phi trc tuyn.

II.7.1.1. My in ng b

Trong bi ton dng cng sut v sau khi ng ng c ca PSS/ADEPT, m hnh my ng b (cc loi 90 99 hay 190 199) s gi in p cc bng hng s ti gi tr ngi s dng qui nh. u ra hay hp thu cng sut phn khng s c iu chnh tng ng vi in p cc. Nu yu cu phn khng ca m hnh vt gii hn kh nng phn khng c qui nh, in p cc s c chnh

32

sao cho cc gii hn khng b vt qu. im thit lp in p v gii hn phn khng ca loi my c trng c qui nh trong file T in My in. im thit lp in p c th c nh ngha khc i cho my ng b ring l trong h s d liu ti th. iu ny s b qua gi tr t T in My in.

Nu my ng b l c vn hnh trn dng nh mc ca n hay trn in p cc th mc tng nhit nh mc ca ng v st s c vt qu tng ng. Vng cung t B ti C, vi bn knh bng kVA nh mc ca my in v tm ti im gc, cho ta gii hn dng in phn ng nh mc ti in p nh mc. im B cho ta h s cng sut nh mc ca my in. Vng cung t A ti B cho ta gii hn dng in phn cm ca my in. Khi vn hnh my ng b di kch thch, c mt t thng bin cao cc u li my in. Vng cung t C ti D cho ta gii hn nhit theo t thng ny.

ng cong cng sut phn khng nh c trnh by trong hnh 22 c th c s dng xc nh cc gii hn phn khng ca my nh c yu cu bi PSS/ADEPT. Gii hn cng sut phn khng cc i v cc tiu quy c tng ng vi cc im B v C tng ng. Ghi ch, tuy nhin, cc gii hn phn khng c th thay i ty theo mc cng sut thc.

Trong tnh ton ngn mch v khi ng ng c tc thi tiu chun trong PSS/ADEPT, my ng b ang chy c xem l c in p hng s sau tng tr sau qu. Trong tnh ton ngn mch, in p c gi c nh l 1 n v. Trong tnh ton khi ng ng c tc thi, in p c gi hng s nh c xc nh t dng ti trc , hay c gi l 1 n v.

Hnh 22 M hnh my in

Khi ngn mch c a ra vi hu t TR, cc my ng b ang chy c xem nh c in p hng s pha sau tng tr qu trong th t thun.

33

Trong qu trnh tnh ton dng ti, khi ng ng c v ngn mch, cc my ng b ang chy c m t nh c minh ho trong hnh 23 trong th t nghch v khng tng ng.

i vi my ng b c cc cun dy ni tam gic, tng tr th t khng phi c ci t l 99. +j99. m t mi ni h.

Hnh 23 Cc thnh phn th t trong my in

II.7.1.2. My in cm ng

Trong tnh ton dng cng sut v sau khi khi ng ng c ca PSS/ADEPT, my in cm ng ang chy c xem nh ti cng sut hng s. H s cng sut ang chy c xc nh t ng cong in p v h s cng sut nh c qui nh trong Tp tin T in My in.

My in cm ng ang chy c m t ging nh cc my ng b trong bi ton gii ngn mch v khi ng ng c tc thi; tc l chng c xem xt nh hng s in p pha sau tng tr trong th t thun. Tng tr l tng tr sau qu quy c nh c trnh by trong hnh 23. Tng tr qu c dng khi ngn mch v my in cm ng ang chy c m t nh c trnh by trong hnh 23. S trnh by th t nghch v th t khng c minh ha trong hnh 23. Hu ht cc my in cm ng khng c ni t, tng tr th t khng thng ci t l 99. +j99. n v.

D liu m t my in cm ng s thng trng thi n nh tng ng. Mch tng ng hai nhnh quy c c trnh by trong hnh 24. Biu thc sau c th c dng bin i d liu t m hnh ny ti d liu nh c yu cu trong Tp tin T in D liu My in trong PSS/ADEPT:

34

Hnh 24 Mch in tng ng ca ng c khng ng b

II.7.1.3. Khi ng ng c tc thi v khi ng li

Khi ng mt ng c ln trong cng nghip hay h thng cng sut yu c th dn ti vic in p khng chp nhn c gim trong h thng. Khi in p gim thp ti nt ng c khi ng, thi khong khi ng s ko di v trong mt vi trng hp bt li, ng c c th khng c lc gia tc t tc nh mc. Phm vi thi gian khi ng ng c quy c t mt vi giy ti mi giy hay nhiu hn. Vic nghin cu khi ng ng c trong PSS/ADEPT cho php ngi s dng xc nh phm vi ca st p trong h thng.

Trong PSS/ADEPT, ng c khi ng c mc nh ni tip vi b khi ng ca my bin th t ngu gim dng ng c cao lin tc (t l vi in p cc ca n) v vy lm gim st p. ng c ang khi ng c m t bi tng tr rotor b kho. i vi ng c ba pha, tng tr rotor b kha l:

vi Ilr l dng rotor b kha ti in p nh mc, cch khc:

35

vi Ifl l dng y ti ti in p nh mc vung gc vi in p cc ng

c. Quy c, Ilr l khong chng 6 ln Ifl.

Bng cch m t khi ng ng c nh mt ti tng tr hng s, st p mng c th c tnh ton vi bi ton dng ti.

PSS/ADEPT cho php ngi s dng xem hai cch khi ng ng c khc nhau trn mng vi my ang chy.

Khi khi ng ng c tc thi, tt c cc my ang chy c gi s vn gi vng t thng hng s v v th gip cho ng c c khi ng. Tt c my ang chy c m hnh nh ngun in p pha sau tng tr th t thun ca n v tng tr ca n n trung tnh trong cc th t khc. Gi s vic khi ng ng c tc thi ko di trong khong thi gian rt ngn, c l 3-5 chu k trong h thng 60 Hz. T thng ca my ang chy phn tn n mt mc cn bng mi kh xa trc khi khi ng ng c t n tc nh mc.

Khi khi ng ng c li, gi thit t thng ca my ang chy b phn tn. Trong tnh trng ny, tt c cc my ang chy c m hnh nh cc ti tng ng v v th khng th h tr ng c khi ng. Hin nhin, thc t st p nghim trng hn v l c tnh khi ng ng c ln trong h thng in cng nghip.

Th t khi ng ng c nh sau:

1. ng c cn khi ng c tch khi mng bng cch ci t gi tr m cho loi ca n.

2. Khi ng ng c tc thi c thc hin. Kt qu dng ti c th c lit k, trng by, in, hay v ra.

3. Khi ng ng c li c th c thc hin. Kt qu dng ti c th c lit k, trng by, in, hay v ra.

4. Vi ng c c khi ng ti tc chy, bi ton dng ti thng thng c th c thc hin v kt qu c th c so snh vi cc bc 2 v 3.

Khi khi ng ng c tc thi trong bc 2, vic khi ng ng c tc thi thnh cng vi t l nc my bin th khi ng khc nhau c th c thc hin. iu ny cng ng trong bc 3 khi khi ng ng c li.

Nu ngi s dng ch quan tm n khi ng ng c tc thi hay khi ng li, th t 1, 2, 4, hay 1, 3, 4 cn c thc hin. Ngi s dng c cnh bo dng th t 1, 3, 2, 4 xem c hai trng hp khi ng ng c tc thi

36

hay khi ng li bi v cc iu kin tin khi ng l khng cn trong b nh sau khi khi ng ng c li.

II.7.1.4. Phng php khi ng ng c

Trong PSS/ADEPT ng c khi ng c gi s mc ni tip vi my bin th t ngu l tng (b khi ng). Tng tr my bin th t ngu c qui nh trong Tp tin T in My in trn c bn ca my bin th v mt nh n zero n v. Nc iu p my bin th t ngu c gi s pha my in v mc nh l t s nh mc (1.0) nh trong hnh 25:

Hnh 25 Khi ng ng c

Nu cc gi tr mt nh ca tng tr my bin th t ngu v nc iu p c s dng, ng c c m t khi khi ng vi in p y c p dng cho cc cc. iu ny thnh thong tham chiu n vic khi ng cho. Ch , my bin th t ngu c gi s c ngt ra (b qua) trong tnh ton dng cng sut v ngn mch.

II.7.1.4.1. in p khi khi ng ng c b gim Khi ng cc my bin th t ngu tng qut c cc nc chuyn i 50%,

65%, v 80% c th c chn gim in p cc ng c di mc bnh thng trong khi khi ng nhm gim dng ln vo. trnh by nc chuyn i 65% trong PSS/ADEPT chng hn, mt nc chuyn i 0.65 phi c qui nh khi khi ng my in.

II.7.1.4.2. Khi ng t mc shunt Trong mt vi trng hp, cc t mc shunt c ng ct trc tuyn khi

mt ng c bt u c khi ng gim st p trn h thng. Phng php ny c th c m hnh trong PSS/ADEPT n gin bng cch thm t l mt dy c nh v ch ng ct trc tuyn. Nu t phi trc tuyn khi tnh ton tin khi ng v ng vo trc khi tnh ton khi ng. Mt khi ng c chy, t phi c ngt ra (ci trng thi= 0) cho tnh ton dng cng sut v ngn mch.

II.7.1.4.3. Khi ng mm SCR Phng php khi ng ny iu khin dng khi ng ng c hay gia tc

vi thit b m t trng thi. Tng tr ng c thc ti im dng c tnh nh l

37

nghch o ca dng ng c n v ti im dng. Nu, v d, dng gii hn khi ng ng c cao ti 3 n v (300%), tng tr rotor thc b kho l ZLR = 0.33 pu.

II.7.1.4.4. Khi ng ng c dy qun ng c dy qun c hn mt mch mc song song trong dy qun stator

(thng thng l hai). N c khi ng khi p dng in p nh mc vung gc ch mt mch. Mch song song cn li c ng in khi gia tc. Tng tr ng c phi hin th phn cun dy c ng in khi gia tc. Tng tr ng c phi hin th phn cun dy c ng in u tin. Nu, v d 50% ca cun dy c ng in u tin, tng tr rotor thc b kho l ZLR = 2.0 * ZLR c bn.

Hai phng php khi ng sau c nh hng n gi tr ZLR. Cc s thay i ti ZLR c th c thc hin trc tip trong Tp tin T in My in cho cc loi my vi b khi ng t bit hay Tp tin T in My in y phi c to s dng khi khi ng ng c c thay i cc gi tr ZLR. Cch khc, gi tr ca nc chuyn i my bin th t ngu c th c qui nh thc s trnh by ZLR thay i. Tng tr khi ng ng c thc c trnh by trong PSS/ADEPT nh:

( )2tapZ

Zeff LR=

vi tap l t s nc chuyn i ca my bin th t ngu theo n v. V th, thc s nhn i tng tr rotor b kha th qui nh tap = 0.707.

Ht chng !

CHNG 2: PHN B CNG SUT

39

CCHHNNGG 22:: PPHHNN BB CCNNGG SSUUTT

Chng ta bit rng c ba phng php tnh phn b cng sut thng c s dng l: phng php Newton-Raphson, phng php phn lp nhanh, v phng php Gauss-Seidel. Mi phng php c nhng c tnh hi t khc nhau, thng th ta chn phng php c kh nng thc hin tt nht. Vic la chn phng php tnh no cn tu thuc vo cu hnh h thng, my pht, c tnh ti v mc in p ti ban u ti cc nt.

Trong chng ny, chng ta n tp li cc kin thc cn thit phc v cho vic tm hiu cch gii bi ton phn b cng sut trong phn mm PSS/ADEPT. Cc kin thc c s v phng php gii bi ton phn b cng sut nh phng trnh i s phi tuyn, sau l bi ton phn b cng sut trong li in v sau cng l tm hiu v phng php gii bi ton phn b cng sut trong phn mm PSS/ADEPT.

Trong bi ton phn b cng sut trong li in thng dng phng trnh lin lc gia in p nt v dng nt thng qua ma trn tng dn nt. Nu bit dng nt, c th tm c in p nt. Tuy vy, trong li in thng cho cng sut hn l dng in. Nh vy, phng trnh lin quan l phng trnh phi tuyn v l phng trnh phn b cng sut c gii bng phng php lp. Sau y ta n tp v phng trnh i s phi tuyn.

40

II.. PPhhnngg ttrrnnhh ii ss pphhii ttuuyynn Sau y, chng ta n li cc phng php gii phng trnh i s phi tuyn.

II..11.. PPhhnngg pphhpp GGaauussss SSeeiiddeell

T phng trnh f(x) = 0 ta suy ra x = g(x) Nh vy quan h gia ln lp th k v k+1 l x(k+1) = g(x(k))

Kt qu chp nhn khi + )k()1k( xx

=> Nhn xt: Tc

hi t chm, v th c th lm tng tc hi t bng cch dng thut ton gia tc vi h s gia tc :

x(k+1) = x(k) + [g(x(k)) x(k)] Nu c n phng trnh vi n n s:

f1(x1,x2,,xn) = c1 => x1 = c1 + g1(x1,x2,,,xn) f2(x1,x2,,xn) = c2 => x2 = c2 + g2(x1,x2,,,xn) fn(x1,x2,,xn) = cn => xn = cn + gn(x1,x2,,,xn)

Bng phng php lp, ta c c: x1(0); x2(0);; xn(0) x1(1); x2(1);; xn(1)

Trong phng php Gauss Seldel, cc gi tr mi ca cc n s xi va c tnh trong cc phng trnh trn lin c thay th ngay vo cc phng trnh k tip. Hi t s t c khi sai bit gia cc gi tr cn tnh sau so vi ln tnh trc nh hn mt h s quy nh. C th dng h s gia tc x(k+1) = x(k) + (xi(k+1) xi(k))

V d: Cho f(x) = x3 6x2 + 9x 4 = 0

x= 94x

96x

91 23 ++

= g(x) x(0) = 2 x(1) = g(2) = 2.2222 x(2)=(2.2222)= 2.5173 x(3) = 2.8966 x(4) = 3.3376 x(5) = 3.7398 x(6) = 3.9568 x(7) = 3.9988 x(8)=4.0000

41

II..22.. PPhhnngg pphhpp NNeewwttoonn RRaapphhssoonn

Cho phng trnh f(x) = c, ta xy dng c nh sau:

x(k+1) = x(k) +

)k(

)k(

dxdf

)x(fc

v i

lng )k()k(

dxdf

)x(fc

gi l sai s ln lp th k x(k) => Nhn xt: Phng php hi t rt nhanh

Nu c n phng trnh vi n n s:

=

==

nn21n

2n212

1n211

c)x,...,x,x(f...

c)x,...,x,x(fc)x,...,x,x(f

Suy ra X(k+1) = X(k) + X(k)

Vi X(k) =

)k(n

)k(2

)k(1

x...xx

= )k()k(

Jc

c(k) =

)k(nn

)k(22

)k(11

)f(c...

)f(c)f(c

V d: Gii phng trnh f(x) = x3 6x2 + 9x 4 = 0 x(0) = 6

)0(

dxdf

= 3(6)2 12(6) + 9 = 45

x(1) = 6 + 1111.145

4)6(9)6(6])6[(0 23 =+ ti cui ln lp th 1: x1(1) = x(0) + x(0) = 6 1.1111 = 4.8889 Cc ln lp k tip:

x(2) = x(1) + x(1) = 4.8889 - 2789.4037.22

4431.13 =

x(3) = x(2) + x(2) = 4.2789 - 0405.45797.129981.2 =

x(4) = x(3) + x(3) = 4.0405 - 0011.44914.93748.0 =

x(5) = x(4) + x(4) = 4.0011 - 000.40126.90095.0 =

42

J(k) =

)k(

n

n

)k(

2

n

)k(

1

n

)k(

n

2

)k(

2

2

)k(

1

2

)k(

n

1

)k(

2

1

)k(

1

1

xf

...xf

xf

............xf

...xf

xf

xf

...xf

xf

l ma trn Jacobian

IIII.. PPhhnn bb ccnngg ssuutt ttrroonngg llii iinn Phn b cng sut trong li in nhm quy hoch, hoch nh kinh t, d kin

tng lai,. Mc ch l tm gi tr in p, gc pha ti mi nt v cng sut tc ng, phn khng chy trn mi nhnh (|V|, ,P,Q). c 3 loi nt:

Nt ngun: c chn lm c s khi in p v gc pha ti bit trc. Nt ny cn bng khc nhau gia ti tiu th v cng sut pht ra do c tn tht trn li in

Nt ph ti: Ti P, Q ca ti c bit, cn in p, gc pha cha bit, cn gi l nt P - Q

Nt iu chnh in p: Ti , P, V c xc nh, gc pha v Q cn c xc dnh, cn gi l nt P V

IIII..11..11.. PPhhnngg ttrrnnhh ccnn bbnngg ccnngg ssuutt Ii = yi0Vi + yi1(Vi V1) + yi2(Vi V2) + + yin(Vi - Vn)

= (yi0 + yi1 + yi2 + + yin)Vi yi1Vi1 yi2V1 - - yinVn

Ii = Vi ==

n

1jjij

n

0jij Vyy vi j i

Cng sut ti nt i: Pi + jQi = Vi *iI hay Ii = *

i

ii

VjQP

==

=n

1jjij

n

1jiji*

i

ii VyyVV

jQP vi j i

IIII..11..22.. PPhhnngg pphhpp GGaauussss SSeeiiddeell

Vi(k+1) =

=

+

ij

n

1j

)k(jij)k(

*i

)k(*i

chSi

y

VyV

jQP

trong (j i)

43

Vi PiSch jQiSch: cng sut tc dng v phn khng (vi nt ngun, PiSch v QiSch c gi tr dng; vi nt ti, PiSch v QiSch c gi tr m

Pi(k+1) = Real

==]VyyV[V

n

1j

)k(jij

n

0jij

)k(i

)k(*i

-Qi(k+1) = Image

==]VyyV[V

n

1j

)k(jij

n

0jij

)k(i

)k(*i

Hay: Pi(k+1) = Real

+=

]VYV[Vn

ij1j

)k(jij

)k(i

)k(*i

Qi(k+1) = -Image

+=

)VYYV(Vn

ij1j

)k(jijii

)k(i

)k(*i

C th dng thm h s gia tc : Vi(r+1)c th chp nhn = Vi(r) + (Vi(r+1) Vi (r)) Vi(k+1)c th chp nhn = Vi(k) + (Vi(k+1) Vi (k)) vi = 1.3 1.7 Qu trnh hi t khi so snh gia phn thc, phn o ca in p nt gia cc

ln lp st nhau trong vng cho php: | ei(k+1) ei(k)| v | fi(k+1) fi(k)|

Tnh ton dng chy cng sut v tn tht: Iij = Il + Ii0 = yij(Vi - Vj) + yi0Vi Iji = -Il + Ij0 = yij(Vj - Vi) + yj0Vj Dng cng sut Sij t nt i n nt j v Sji t nt j n nt i ln lt l Sij =

ViIij* v Sji = VjIji* Tn tht trn ng dy ni nt i v j l: SLij = Sij + Sji

IIII..11..33.. PPhhnngg pphhpp NNeewwttoonn RRaapphhssoonn ggiiii bbii ttoonn pphhnn bb ccnngg ssuutt Do hi t bc hai, phng php Newton Raphson thng c dng. S

ln hi t khng ph thuc vo s nt

Ii = =

n

jij

n

0jiji VyyV vi j i

Vit li: Ii* = =

n

1jjijVY vi j c th bng i

Vit di dng cc: Ii = =

+n

1jjijjij VY

Cng sut ti nt i: Pi jQi = Vi* Ii = iiV =

+n

1jjijjij VY

Tch ring phn thc v phn o, ta c:

Pi = )cos(YVV jiijn

1jijji +

= (1)

44

Qi = - )sin(YVV jiijn

1jijji +

= (2)

y l phng trnh phi tuyn theo cc bin c lp, in p c tnh theo n v tng i, gc pha l rad. Ta c 2 phng trnh cho mi nt ti cho bi (1) v (2) v 1 phng trnh cho mi nt iu khin in p cho bi (2)

Theo phng php Newton Raphson:

)k(n

)k(2

)k(n

)k(2

Q...

QP...P

=

)k(

n

n)k(

2

n)k(

2

n)k(

2

n

)k(

n

2)k(

2

2)k(

n

2)k(

2

2

)k(

n

n)k(

2

n)k(

n

n)k(

2

n

)k(

n

2)k(

2

2)k(

n

2)k(

2

2

VQ

...VQQ

...Q

VQ...

VQQ...Q

VP...

VPP...P

..................VP...

VPP...P

)k(n

)k(

2

n

)k(2

V...

V

...

Trong phng trnh trn, nt i c coi l nt c s

=>

=

VJJJJ

QP

43

21

Thnh phn J1:

+= n

jijiij

i

)sin(YijVjViPi (3)

)sin(YVVPi jiijijjij

+= vi i j (4)

Thnh phn J2:

)cos(YVcosYV2VPi

jiij

n

ijijjiiiii

i

++=

(5)

)cos(YVVPi

jiijijij

+= vi i j (6)

Thnh phn J3:

+= n

jijiij

i

i )cos(YijVjViQ (7)

)cos(YVVQ jiijijjij

i = (8)

Thnh phn J4:

= n

ijjiijijjiiiii

i

i )sin(YVsinYV2VQ (9)

)sin(YVVQ

jiijijij

i += vi i j (10)

45

Cc s hng Pi(k) v Qi(k) l sai bit gia gi tr tnh ton v gi tr t sn, gi l sai bit cng sut Pi(k) = PiSch Pi(k) (11) Qi(k) = QiSch Qi(k) (12)

Cc gi tr mi ca in p nt: i(k+1) = i(k) + i(k) (13) | Vi(k+1) | = | Vi(k) | + | Vi(k) | (14) Nh vy, gii thut Newton Raphson nh sau: i vi nt ti, PiSch, QiSch cho sn, in p v pha ti nt ngun t

bng 1 v 0, suy ra | Vi |(0) = 1.0 v i(0) = 0. i vi iu chnh in p, | Vi | v PiSch- cho sn, gc pha c cho bng gc pha ca nt ngun, ngha l i(0) = 0

i vi nt ti, Pi(k) v Qi(k) c tnh t (1) v (2) v Pi(k) v Qi(k) t (11) v (12)

i vi nt iu khin in p, Pi(k) v Pi(k) tnh t (1) v (11) Cc phn t ca ma trn Jacobian (J1, J2, J3, J4) c tnh t (3), (4), .,(10) Gii phng trnh

=

VJJJJ

QP

43

21 trc tip bng phng php kh

Gauss hay tha s tam gic c sp xp ti u Tnh ton cc gi tr mi ca | Vi | v i t (13), (14) Tip tc cho n khi | Pi(k) | v | Qi(k) | nh hn mt sai s cho trc

IIIIII.. PPhhnngg pphhpp ttnnhh pphhnn bb ccnngg ssuutt ccaa pphhnn mmmm PPSSSS//AADDEEPPTT 55..00

Kho st m hnh c bn gii bi ton phn b cng sut ca PSS/ADEPT lit k di y.

Trong PSS/ADEPT, cc b phn ca li in c chia thnh nhiu loi:

im ni (cn gi l nt bus): l ni cc b phn khc trong li in gp nhau. im ni c th c hoc khng tng ng vi thit b trong thc t.

Thit b ni Shunt tng trng cho b phn vt l t ti mt im ni.

Thit b nhnh tng trng cho b phn vt l tn ti gia hai (hay nhiu) im ni vi nhau.

H thng in cp y thng l h thng ba pha, v trong PSS/ADEPT mi b phn trong li ba pha bao gm thng tin cho c ba pha v c th thao tc nh mt b phn mt pha.

46

Mt nt, chng hn nh cho ba im ni, mi im c ba pha A, B v C. Tng t vy, mi nhnh cng c ba pha (gia A vi B hoc C) gia hai nt.

S lng thc ca dy dn hoc pha l thuc tnh ca nhnh. V th, mt nhnh ba pha c th tng trng cho c mt, hai hoc ba pha.

Thit b mc Shunt, tr t in mc Shunt, u c nh ngha tng t nh nhnh, cng c 3, 2, hay 1 pha.

III.1.1. Ngun

Bi ton mng in gii trong PSS/ADEPT phi c ti thiu mt ngun ba pha cn bng. PSS/ADEPT, c th gii bi ton c nhiu ngun hot ng cng mt lc.

Mt ngun c t trng bi in p, tng tr th t thun v th t khng. Ch khi bit c cng sut ngn mch ca ngun th mi c th chuyn sang tng tr th t thun v th t khng.

III.1.2. Dy v cp

Dy ni lin hai nt vi nhau v ti thiu phi c t nht mt dy pha. Mt dy c th c 1, 2 hoc 3 dy pha. Dy chuyn v c t trng bi tng tr th t thun v th t khng, v bi in np th t thun v khng.

Dy mt v hai pha cn c t trng bi thnh phn th t thun v khng ca tng tr/ dn np. Dy mt pha ch c mt tng tr ni tip v mt thnh phn dn np. Khi nhp liu cho dy mt pha, t thnh phn th t thun v khng ca tng tr/ dn np bng nhau.

Dy dn hai pha c tng tr t cm Zs v h cm Zm. Khi nhp liu cho dy hai pha t thnh phn tng tr th t thun v khng nh cch t cho dy ba pha (vd Z1 = Zs Zm v Z0 = Zs + 2 Zm). Dy hai pha c hai thnh phn dn np, Bs c trng cho mi dy dn n t, Bm c trng cho hai dy dn vi nhau.

Tng t, rt ra cch lm cho dy ba pha, B1 = Bs + 2 Bm, B0 = Bs. Cch n gin nhp vo tng tr/ dn np l s dng lun gi tr ca dy ba pha; sai s nu c cng s rt nh. Hin nay, d liu cho cp thng c nhp ging nh dy trn khng, bng cch ch nh thnh phn th t thun v khng. i vi cp ngm, thnh phn dn np th t thun v th t khng thng thng bng nhau.

III.1.3. My bin th

PSS/ADEPT m hnh nhiu dng ni dy my bin th gm: Y-Y, Y-, -, iu chnh in p.v.v.

Mi my bin p c thnh phn tng tr th t thun v khng, gi tr ny ghi bn ngoi hoc trong bn hng dn.

47

Thnh phn tng tr th t khng t trng cho tng tr ni t trong s ni dy dng sao tam gic. Nu my bin th khng c tng tr ni t, t thnh phn tng tr th t khng bng vi th t thun.

i vi my bin th u dng -, hoc dng Y- bn phn Y ni t trc tip, t thnh phn tng tr th t khng bng vi th t thun; PSS/ADEPT kho st dng th t khng, dng th t khng ni Shunt qua t.v.v.

V PSS/ADEPT qun l cc loi my bin th v cch ni dy khc vi PSS/U, s c vi thay i trong chuyn i d liu khi s dng file d liu th raw data (*.dat) gia cc chng trnh ny.

III.1.4. M hnh my in

My in ng b v khng ng b u c m hnh ho trong PSS/ADEPT.

C hai loi ny u c thit k sn cho c dng my pht ln ng c bng cch chn c trng thch hp thng qua cng sut thc tng th, gi tr m cho bit l my pht.

III.1.4.1. My in ng b

Trong bi ton phn b cng sut, m hnh my in ng b trong PSS/ADEPT gi c nh gi tr in p l hng s bng vi gi tr ngi dng a vo. Lng cng sut phn khng pht ra hay thu vo c s dng iu chnh in p.Nu lng cng sut yu cu ca m hnh vt qu gii hn kh nng cho php th kh nng iu khin in p cng s mt theo, v my in ng b lc tr thnh ti tiu th cng sut.

Nu my in ng b hot ng dng ln hn dng nh mc, th nhit trong ng v st s ln lt tng vt mc theo. Nhng hn ch ny c t t nh l hm ca cng sut phn khng theo cng sut thc.

Cung trn t B n C, c bn knh bng cng sut nh mc ca my in, biu th t c dng nh mc in p nh mc. im B biu th h s cng sut nh mc ca my in. Cung t A n B biu th dng kch t nh mc ca my in.

Khi my in hot ng trong min di kch t, tn ti bin t thng ln trong li st. Cung t C n D biu th gii hn nhit gy ra do t thng.

ng cong cng sut phn khng dng xc nh gii hn cng sut phn khng ca my in. Gi tr ti hn ln nht v nh nht ln lt tng ng vi hai im B v C. Tuy nhin cn lu rng, gii hn cng sut phn khng c th thay i tu theo mc cng sut thc

48

Khi mt my in khi ng, n th hin qua tng tr rotor. Nu mt my in ang hot ng, v c mt my in khc cng khi ng, th my in ang hot ng s c m hnh bi mt ngun ghp sau tng tr qu .

Gi tr ca in p ngun v gc pha c xc nh bng cch cho chy chng trnh tnh ton mng in iu kin trc khi ng kha ni ng c vo mng in.

Trong m phng s c ngn mch, mt my in m hnh bi mt ngun dng gn theo sau tng tr qu hay sau qu , tu thuc vo ch no ta mun kho st.

Gi tr ca ngun c xc nh tng t nh cch lm i vi khi ng ng c (vd chy bi ton phn b cng sut trc s c).

III.1.4.2. ng c khng ng b

Trong khi m phng bi ton phn b cng sut, ng c khng ng b (DCKDB) th hin bi cng sut thc n s dng. Lng cng sut phn khng tiu th v trt c xc nh t m hnh my in. C 5 loi DCKDB trong PSS/ADEPT, tng ng vi cc mu thit k A, B, C, D, v E.

Tuy nhin, nu DCKDB i ra bn ngoi vng c Momem ln nht, n s b gi li. Khi iu xy ra, DCKDB s c biu th bi tng tr kho Rotor (locked rotor impedance).

Khi mt DCKDB khi ng, n th hin qua tng tr kho rotor. Nu mt DCKDB ang hot ng, v c mt DCKDB khc cng khi ng, th DCKDB ang hot ng s c m hnh bi mt ngun ghp sau tng tr, tng t nh trng hp my in ng b.

Trong m phng s c ngn mch, mt DCKDB m hnh bi mt ngun gn theo sau tng tr qu hay sau qu , tng t nh trng hp my in ng b.

Ht chng !

CHNG 3: NGN MCH

50

CCHHNNGG 33:: NNGGNN MMCCHH

Tnh ton ngn mch xc nh nh hng ca s c trn li in (v d: 1 hoc nhiu pha chm nhau, chm t, chm vo cy ci)

Tnh ton s c. Chui s c. - Trong tnh ton s c, tt c in p, dng in nhnh v dng in s

c khi s c xy ra ti mt hoc nhiu nt trn mng li. - Trong tnh ton chui s c: p dng tnh ton mt chui cc s c

lin tc v ring l. Tnh ton chui s c cho tt c cc loi s c c ng dng lin tc v ring l ti mi nt trong ton h thng in. Tnh ton ngn mch s s dng trng thi h thng trc khi s c xt hin.

Khi khng c s c, dng ti s c tm v in p ti cc nt trc s c c tnh.

i vi ti tnh th c quy i thnh khng tr khng i tnh theo cng st v in p ti nt m ti c ni..

My pht c ni ngun in p ni tip mt khng tr, ln v gc ca ngun c xc nh t li gii dng ti.

Mi chng trong phn kin thc n tp gm 2 chnh: phn kin thc l thuyt v phnkin thc p dng trin khai xy dng thnh thut ton trong phn mm PSS/ADEPT. Vi cch trnh by nh vy s gip cc hc vin n tp tt hn v tip thu nhanh cc kin thc trong cc phn khc.

Sau y trnh by phn l thuyt bi ton ngn mch.

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II.. LL tthhuuyytt bbii ttoonn nnggnn mmcc