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