ĐATN_ An toàn điện_chuong 3

Chng 3

H THNG NI T

Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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Chng 3: H THNG NI T

MC TIUSau khi hc xong chng 3 sinh vin c kh nng: Phn tch c u, nhc im, tnh nng v phm vi ng dng ca cc h thng ngun ni t chun. C kh nng tnh ton, thit k, thi cng h thng ni t tha cc tiu chun hin hnh.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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Chng 3: H THNG NI T

NI DUNG3.1 Cc h thng ni t chun

3.2 in tr sut ca t3.3 Loi ni t 3.4 Cc kiu ni t 3.5 in tr ni t 3.6 Phn tch h thng ni t hin i


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3.1. CC H THNG NI T CHUN H thng in phn phi c phn loi da vo cch b tr h thng ni t.

IT, TT, TN C, TN S, TN CS Ch ci th I ch tnh cht ca trung tnh ngun: T: Trung tnh ngun trc tip ni t. I : Cc phn t mang in cch ly vi t. Ch ci th II ch hnh thc bo v: T: Ni t trc tip N: Ni trc tip bng dy dn bo v vi im ni t ca ngun(thng l dy trung tnh)Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.1. CC H THNG NI T CHUN Trong mng TN dng thm 1 hoc 2 ch ci nh ngha cch b tr dy trung tnh v dy bo v: C : Dy trung tnh N v dy bo v PE chung nhau thnh 1 dy PEN. S : Dy trung tnh N v dy PE tch bit nhau. CS: Dy N v PE kt hp trong 1 vi phn ca h thng.


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3.1. CC H THNG NI T CHUN1. H thng IT: V thit b c ni t ring. Tit din dy PE nh hn dy N. Bnh thng trn dy PE khng c st p.

H thng IT 6


3.1. CC H THNG NI T CHUN1. H thng IT: Gim ngng qu p khi xut hin s c chm t cun cao sang cun h MBA ngun. Khi h cch in, dng s c th nht thng thp v khng nguy him.

S c th 2 xy ra trn pha khc to dng ngn mch v gy nguy him.Cn s dng thit b vn hnh khi c s c 2 pha hay lp t thit b kim sot cch in.


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3.1. CC H THNG NI T CHUN2. H thng TT: S n gin. S dng 2 h thng ni t ring nn cn lu bo v qu p. Tit din dy PE c th nh hn dy N v xc nh theo dng s c. Bnh thng, dy PE khng c st p. Khi s c, xung in p trn dy PE thp.H thng TTTrng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.1. CC H THNG NI T CHUN3. H thng TN: a. H thng TN-S Dng s c v U tip xc ln nn cn trang b thit b t ng bo v ngt ngun khi c s c. Dy PE tch bit dy N, khng ni t lp li. Bnh thng, khng c dng in v st p trn dy PE.9

H thng TN-S


3.1. CC H THNG NI T CHUN3. H thng TN: b. H thng TN-C

Ni t lp li m bo dy PE ni t mi TH. Dng s c v H thng TN-C U tip xc ln nn cn trang b thit b t ng bo v ngt ngun khi c s c. Bnh thng, v thit b, t v dy N c cng U. Khi s c st p ngun, nhiu ln. Khi ti khng i xng, trong dy PE c in.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.1. CC H THNG NI T CHUN3. H thng TN: c. H thng TN-C-S H thng ny kt hp gia TN-C(trc) v TN-S (sau). im phn dy PE t dy PEN thng l im u ca li.

H thng TN-C-STrng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.1. CC H THNG NI T CHUNPhm vi ng dng cc h thng ni t TT :mng in hn ch kim tra hay c th m rng. IT : yu cu lin tc cung cp in. TN : mng in kim tra thng xuyn hay khng m rng. - TN-S: bt buc cho mch s dng dy ng c 16mm2.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.1. CC H THNG NI T CHUNPhm vi ng dng cc h thng ni t Trong thc t, vic chn loi h thng ni t cn c vo cc yu cu sau: An ton chng in git (TN-C, TN-S) An ton chng ho hon(TN-S) Bo v chng qu p (IT) Bo v chng nhiu in t ( TT, TN-S)

Lin tc cung cp in (IT)13


3.1. CC H THNG NI T CHUNPhm vi ng dng cc h thng ni t Loi mng in Khuyn C th Khng dng s/dng s/dngMng in rt ln vi R30 Mng truyn hnh, truyn thanh Mng in vi dng r ln (>500mA) Mng ngoi tri vi ng dy trn khng My pht in d phng TT,TN,IT

TN TNTN TT IT

TT TT IT,TT TN TT

TN-C,IT IT

IT TN


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3.1. CC H THNG NI T CHUNLoi tiTi nhy cm vi dng s c ln (ng c)Ti vi mc cch in thp (l in, my hn) Thit b 1 pha s dng in p (L N) Ti vi mc gy nguy him cao (cn trc, bng chuyn) My cng c

Khuyn C th Khng dng s/dng s/dngIT TN TT,TN-S TT TT TN IT TN-C,IT TT

TN

IT

TN-S

TN-C,IT

TT


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3.1. CC H THNG NI T CHUNCc loi khcMng cp in t MBA ni sao-sao Cng trnh d chy Mng in vi trm BA khch hng Mng in vi my bin tn Mng in vi vic lin mch ni t khng m bo Thit b in t

Khuyn C th Khng dng s/dng s/dngTT IT khng IT c c dy N dy N

ITTT TT TT TN-S IT

TN-S,TT TN-C

TN,IT TN-S TN-C,IT TN-C

TTTN-S,TT

Mng iu khin t/b, cm bin PLC v t/b chp hnh


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3.1. CC H THNG NI T CHUN4. Quy nh v dy bo v PE v PEN Dy PE ni cc vt dn t nhin v v kim loi khng mang in ca cc thit b to li ng p.

Dy PE thng bc cch in mu vng sc xanh lc. Trn dy PE khng cha thit b ng ct. Dy PEN c chc nng ca dy trung tnh v dy bo v c tit din khng nh hn dy trung tnh. Phng php chn tit din dy PE v dy PEN: PP n gin ho PP ng tr nhitTrng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.1. CC H THNG NI T CHUN4. Quy nh v dy bo v PE v PEN Bi tp v d: Xc nh tit din ti thiu ca dy PE trong mng h p s dng cp n li bng ng, c v bc cch in PVC. Bit dng ngn mch chm t I=25kA, thi gian ct ngn mch ca CB tC = 30ms ?Gii

Phng php ng tr nhit

Chn SPE = 35 mm2Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.2. IN TR SUT CA T L in tr ca khi lp phng t mi cnh 1cm c n v m Bin thin trong phm vi rng v ph thuc vo: cu to, m t, to, dnh cc ht t, mui. Xc nh theo biu thc: 4aR =1+

2a

_

2a

a: khong cch gia cc cc (m)4b2)

(a2 +

b 2)

(4a2 +

b: chiu su cc chn trong t (m)

R: in tr t th hin trn my o in tr theo phng php c.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.2. IN TR SUT CA T TH a > 20b : = 2aR thay i theo ma nn tt = .Km tt : in tr sut tnh ton Km : h s thay i (h s ma)H s thay i in tr sut ca t theo ma Km

Hnh thc ni t Thanh t nm ngang Cc ng thng ng

su t b phn ni t(m) 0,5 0,81 0,8

Km

Ghi ch

1,41,8 o vo 1,251,45 ma kh 1,21,4 o vo ma ma20


3.2. IN TR SUT CA T Tnh ton s b c th dng tr s gn ng ca cho 1 s loi t c trnh by bng di:Loi t Nc bin t en t st m Nc sng,ao h t pha st t rung

Tr s in tr sut ca t Gi tr in tr Gi tr in tr sut sut gii hn(m) khi thit k(m)0,15 0,25 5 100 2 12 10 500 20 200 20 100 0,2 8 10 20 30 40 21


3.2. IN TR SUT CA TLoi t B tng t kh t pha ct Than t nh Ct t ln Gi tr in tr Gi tr in tr sut sut gii hn(m) khi thit k(m) 40 1000 20 1000 300 500 1000 5000 1000 50000 1000 10000 10000 50000 100 100 400 2000 3000 3000 20000 22


3.3. LOI NI T1. Ni t t nhin ng dn nc hay v bc kim loi (khng phi ng nhin liu) l trang thit b ni t. Ch c coi l ni t b sung 2. Ni t nhn to m bo R t nm trong gii hn cho php, n nh lu di Ni t bng cch cc thp, thanh dp hnh ch nht di 23m ng xung t 0,50,8m. Tit din cc ni t 48mm2 vi U1000V v 100mm2 vi U > 1000V.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.3. LOI NI Tc im trang thit b ni t kiu c v kiu mi

Thit b kiu c- ng KL =3550mm, d=35mm, l = 23m

Thit b kiu mi- Cc ng li thp =1316mm, d = 1,4; 2,4; 3m - Cc m li thp =1316mm, d= 1; 1,5; 3m

- Thanh thp dp d4mm, S48mm2

- Cp ng trn S25mm2 - Bng ng 50mm0,5mm - Cp ng trn S25mm2 - Li ng trn - Bn ng trn


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3.3. LOI NI Tc im trang thit b ni t kiu c v kiu mi

Thit b kiu c- Lin kt gia cc v cp + Kp kim loi + Hn in + Hn gi - Ci to t + Than + Mui

Thit b kiu mi-Lin kt gia cc v cp + c xit cp + Hn ho nhit - Ci to t + Ho cht gim in tr t

- Bng ng ni t- Hp btng kim tra ni t

- Bng ng ni t- Hp kim tra ni t bng nha tng hp 25


3.4. CC KIU NI TNi t tp trung Ni t mch vng

Khong cch cc Bng ng Cc di Hng cc ni t cc bng t ln chiuni t Cp ng lin kt cccch 2 ni cc loi tr hiu ng mp tng 11,5m. mn che. S dng khi phm vi S dng ni t m, cng trnh hp ( th) in tr sut thp, xa hoc trang thit b c U>1000V, I chm t ln. cng trnh(ngoi )Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.4. CC KIU NI TThi cng h thng ni t cn ch : Trc khi t xung t, cc (thanh) ni t bng st, thp phi nh sch g, trng km(nu cn), khng sn hoc dng cc thp bc ng. ng dy ni t chnh chn su 0,50,7m ngoi tri v t trong rnh hay ni theo tng trong nh. Dy ni t chnh v trang thit b ni vi nhau thng qua bng ng ni t. Cm ni trc tip trang thit b vi dy Bng ng ni t ni t chnh.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.5. IN TR NI T1. Xc nh in tr ni t _ a.HT ni t n ginLoi in cc Mt ct ngang Mt chiu bngd d d

Cng thc

Ghi ch

Cc chn thng ng Cc chn di t mt khong h Thanh nm ngang trn mt t Thanh nm ngang chn di t mt khong h

L h L d L h L

(1)

(1)(1)

Ld

d

(2)

Ghi ch: (1) d < di qu 3m c xem xt trong cc trng hp sau: Lp t trn c in tr sut ln.L1L2

Din tch trin khai h thng ni t b hn ch.

Gradient in th theo L 46


3.6. PHN TCH CC H THNG NI T HIN I1. Thit b, vt liu v cng ngh mi: b. Lin kt gia cc b phn ni t: c xit Hn ho nhit CADWELD - Tn dng hiu qu - Khng h v gim cht lng theo thi gian - Khng b n mn - Chu c s c lp li - Thit b nh, khng i hi ngun ngoi, khng t.

Hn Cadweld 47


3.6. PHN TCH CC H THNG NI T HIN I1. Thit b, vt liu v cng ngh mi: c. Ho cht gim in tr t: C/ty Erico Lighting Technologies cung cp cc loi ho cht gim R: EEC v GEM nhm lm cho R10 nh yu cu.

Gm ion kim loi c tnh dn in cao , ho cht gi m v ho cht kt dnh in tr t gim 5090% khi ha cht c cho vo cc vng c cao nh t st hoc ct.Trng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.6. PHN TCH CC H THNG NI T HIN I1. Thit b, vt liu v cng ngh mi: c. Ho cht gim in tr t: u im: - Bn vng, khng cn bo tr (khng b n mn do phn ng vi mui hay ho cht) - Gi R gi tr n nh - Khng b phn hu hay mc ra - Thch hp cho vic lp t ni t kh hay bn - Khng ph thuc s hin din ca nc duy tr tnh dn inTrng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.6. PHN TCH CC H THNG NI T HIN I1. Thit b, vt liu v cng ngh mi: d. Cc ho cht : Ni c in tr sut t qu cao v din tch cho vic thi cng lp t b hn ch c th s dng cc ho cht in tr ni t thp.


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3.6. PHN TCH CC H THNG NI T HIN I1. Thit b, vt liu v cng ngh mi: e. My o in tr ni t hin i: Hin th mn hnh LCD Tm o rng v chnh xc cao 2% C th o R bng phng php 2 cc hoc 4 cc o tng phn t vi s tr gip ca BI v BU T ng ho qu trnh o T nhn bit kt ni dy o v kt ni n vi t B tr in tr dy o KQ chnh xc vi R nh Chc nng lu d liu v in kt qu ra giyTrng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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3.6. PHN TCH CC H THNG NI T HIN I2. Phn mm ph tr: Cc thng s ng vo: ,L v ca cc/thanh/dy ni t, s lng cc, b rng, b di, ng knh h chn Kt qu tnh ton: R ni t, s lng ho cht Gem cn s dng

Phn mm GEM 3.1 52


3.6. PHN TCH CC H THNG NI T HIN I2. Phn mm ph tr: Chc nng phn mm GEM

- Tnh R ni t ca mt v nhiu cc khi c/ khng ho cht gim in tr Gem- Tnh R ni t ca thanh(dy) ni cc cc b tr theo ng thng khi c/ khng Gem - Tnh R ni t ca thanh(dy) ni cc cc b tr theo mch vng khi c/ khng Gem

- Hng dn lp t h thng ni t chn thng ng v chn nm ngangTrng H S phm K thut Tp.HCM _ Bi ging mn An ton in

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Tit din dy PE v dy PENTit din dy pha Sph(mm2) Cu Al PP n

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ĐATN_ An toàn điện_chuong 3