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điệnTRANSCRIPT
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CNG TY IN LC I
X NGHIP IN CAO TH MIN BC
TI LIU BI HUN
CNG NHN VN HNH TRM V
NG DY
H ni 2008
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MC LC
PHN I : K THUT IN.
1. in nng l g ?
2. Dng in l g ? Tc dng ca dng in? Nu cng thc tnh dng in ?
3. Hiu in th l g ? in p l g , n v o ?
4. in trng , cng in trng l g ?
5. T trng l g ?
6. Phn bit in mt chiu v in xoay chiu hnh sin ?
7. Chu k dng in xoay chiu ( hnh sin ) l g ? Tn s dng in xoay chiu
( hnh sin ) l g, n v o ?
8. in tr l g ?
9. in tr phi tuyn l g ?
10. Nu cng thc tnh in tr ? Gii thch ngha, n v tnh ca mi i
lng trong cng thc tnh ?
11. Tnh in tr tng ng trong mch ni tip, song song ?
12. Cho bit in tr ph thuc vo nhit d ?
13. Khi no cn din tr ln, khi no cn in tr nh ?
14.Cm khng l g ? Cng thc tnh cm khng, n v o ?
15. Dung khng l g? Cc cng thc tnh dung khng, n v o ?
17. Tng tr l g? Cng thc tnh ?
18. Cc dng cng sut ? n v tnh tn i lng ? Quan h gia cc cng
sut ?
19. Nu nhng thit b cung cp cng sut tc dng, phn khng , Thit b no
tiu th cng sut tc dng, cng sut phn khng ?
20. H s cng sut l g ? ngha v cch nng cao h s cng sut ?
21. Tit din dy dn c chn cn c vo nhng i lng no ?
22. T in l g, cu to v c im ca t in ? Cc cng thc lin quan n
t in ?
23. Tnh in dung mc ni tit va mc song , hn hp .
24. Nguyn l cm ng in t l g ?
25. H cm l g? Nu tc dng tng h ca 2 dy dn thng song song mang
in ?
26. Hin tng t cm ?
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27. Cng dng ca o pha ca ng dy truyn ti in ?
28. Nguyn tc hot ng ca my pht in 1 chiu , xoay chiu ?
29. Nguyn l bin i dng in xoay chiu ?
30. Quan h dng , p trong mch xoay chiu thun tr, thun cm, thun dung
R, L, C ni tip, song song v hin tng cng hng ?
31. Cch to ra h thng in xoay chiu 3 pha, xoay chiu 3 pha 4 dy ?
32. Quan h gia in p pha , in p dy, dng in pha , dng in dy trong
mch u sao, tam gic, cng sut trong mng xoay chiu 1 pha, 3 pha ?
33. Phn tch mng 3 pha trung tnh cch in ( khng ni t ) ?
34. Phn tch mng 3 pha trung tnh ni t qua cun dp h quang ?
35. Phn tch mng 3 pha trung tnh trc tip ni t ?
36. Ti sao trong h thng in p t trung p tr ln ngi ta ch truyn ti 3
dy pha ( khng c day trung tnh ) ?
37. Khi nim v sn xut in nng, truyn ti v phn phi ?
38. Tn tht cng sut , tn tht in nng , ngha ? Tn tht in nng kinh
doanh, tn tht in nng k thut l g ? cc bin php khc phc ?
39. Cch tnh tn tht in nng trong my bin p, trong mt ng dy cp
cho ph ti ?
40.Tn tht in p l g ? Cch tnh tn tht in p ?
41. Tnh tn tht in p trong my bin p v trn ng dy truyn ti in ?
Quy nh v thay i in p trong h thng in ?
42. Tai sao phi nng cao in p truyn ti in nng i xa ?
43. Phn bit mt s khi nim : Khng in, khng ti, ti nh mc, non ti,
y ti v qu ti ?
44. Chnh lu dng in xoay chiu l gi? V v gii thch mch chnh lu
dng in xoay chiu ?
45. Th no l in p bc, in p tip xc, cch di chuyn ra khi vng c
in p bc? V hnh minh ha ?
46. Cc khi nim chung ni t trong h thng in ?
47. Nu cc quy nh v ni t trong h thng in ?
PHN II : THIT B IN .
a. c quy .
1. Cu to ca c quy axit, c quy kim ?
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2. ng dng ca c quy trong trm bin p v u im ca n ?
3. Cc thng s k thut ca c quy axt v c quy kim ?
4. Phn loi c quy, so snh u khuyt im ca chng ?
5. Cch chn c quy, v cch u c quy khi s dng ?
6. Vn hnh v s dng c quy ?
7. Cch np hnh thnh mt c quy mi ?
8. Cc h hng c quy v cch sa cha ?
9. My np l g ? nguyn l lm vic ca my np ?
10. Quy trnh vn hnh h thng c quy ca trm anh , ch ang lm vic
b. My bin p .
1. My bin p l g ? Phn loi my bin p ?
2. Nguyn l lm vic ca my bin p ?
3. Cc t u dy ca my bin p 3 pha ?
4. Trnh by v tn tht in p v tn tht in nng trong my bin p ?.
5. ngha cc thng s k thut c bn ca my bin p ?
6. B iu chnh di ti l g? Cng dng v nguyn l lm vic ?
7. B iu chnh khng in l g ? Cng dng v nguyn l lm vic ?
8. Cu to cc thit b chnh ca my bin p ?
9. Cu to v nguyn l lm vic cc thit b ph ca bin p ? Vai tr ca n
trong my bin p ?
10. Cng dng du trong my bin p ?
11. H thng lm mt my bin p, cng dng, phn loi ?
12. Cc h hng ca my bin p v cch x l ?
c. My ct in .
1. My ct in l g ?
2. Phn loi my ct in, u khuyt im ca tng loi ?
3. Cu to v nguyn l lm vic ca my ct in dp h quang bng kh SF6 ?
4. . Cu to v nguyn l lm vic ca my ct in dp h quang bng du
cch in ?
5. Cu to v nguyn l lm vic ca my ct in dp h quang bng chn
khng ?
6. S nguyn l lm vic ca b truyn ng l so ?
7. S nguyn l lm vic ca b truyn ng bng du thy lc ?
8. S nguyn l lm vic ca b truyn ng bng khng kh nn
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9. Cc thng s chnh v yu cu ca my ct din ?
10. Cc h hng thng gp trong my ct in v cch x l ?
d. Dao cch ly .
1. Dao cch ly l g ?
2. Cu to v phn loi dao cch ly ?
3. Cc thng s k thut ca dao cch ly ?
4. Cc h hng v cch x l ?
e. My bin dng in .
1. My bin dng in l g ? Phn loi my bin in p ?
2. Cu to v nguyn l lm vic ca my bin in p kiu t in ?
3. Cu to v nguyn l lm vic ca my bin in p kiu in t ?
4. Cc thng s c bn ca my bin in p ?
5. Sai s ca my bin in p, Ch lm vic ca my bin in p ?
6. S khc bit c bn ca my bin dng in v my bin p t dng ?
7. Cc h hng v cch x l ?
g. My bin dng in .
1. My bin dng in l g ?
2. Cu to v nguyn l lm vic ca my bin dng in ?
3. Cc thng s c bn ca my bin dng in ?
4. Phn loi v ch lm vic ca my bin dng in ?
5. So snh my bin dng in v my bin in p ?
6. Sai s ca my bin dng , phn bit my bin dng v my bin p khc,
nhng khc bit c bn gia chng ?
h. T in .
1. Cng dng ca t in cao th ?
2. Cu to ca t in cao th ?
3. Cc thng s ca t in cao th ?
4. B dc l g, tc dng ca b dc ?
5. B ngang l g, tc dng ca b ngang ?
6. u ni t in cao th vo li nh th no ?
7. Bo v cho cc t in cao th, nhng lu khi lm vic vi t in cao th ?
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8. So snh u nhc im ca my b ng b vi t in ?
i. ng c khng ng b .
1. Cu to ca ng c khng ng b 3 pha, 1 pha ?
2. ng dng ca ng c khng ng b 3 pha , 1 pha trong cc trm bin p ?
k. Cc thit b chng st ?
1. Cc loi chng st trong li in ?
2. Cc thng s ca thit b chng st ?
3. Cu to v nguyn l lm vic ca cc loi chng st van ?
PHN III : MCH IU KHIN , O LNG .
1. Mch nht th l g ? Mch nh th l g ?
2. Cc chc nng ca mach iu khin , o lng trong trm bin p ?
3. V sao mch nh th ( iu khin, bo v ) s dng ngun in 1 chiu
thay v mch xoay chiu ?
4. Cc loi s in trong trm bin p, k hiu trong mch in ?
5. S ni ba my bin p ?
6. S ni ba my bin dng in ?
7. Mch in ni 3 am pe k o cng dng in trn 3 pha ?
8. Mch in dng 1 am pe k v mt kha chuyn mch dng in 3 pha 9.
Mch in ni 3 vn k o in p dy ca 3 pha ?
10. Mch in dng mt vn k v kha chuyn mch o in p 3 pha ?
11. Mch in dng mt ot k ba pha ba phn t o cng sut tc dng ?
12. Mch in dng mt var k ba pha ba phn t o cng sut phn khng ?
13. Phn tch mch in nguyn l iu khin ca my ct in ? ng dng i
vi cc loi my ngt ca Siemens, ABB
14. Nguyn l lm vic ng , ct my ngt ti ch ?
15. Mch iu khin dao cch ly ?
16. Mch iu khin b lm mt my bin p ?
17.ch iu khin b chuyn nc my bin p ?
18. Mch bo tn hiu chm t ?
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PHN IV : RLE BO V .
1. Cng dng v cc yu cu ca rle ?
2. Th no l bo v chnh, bo v d phng ?
3. Lit k cc rle bo v cho my bin p ?
4. Lit k cc rle bo v cho ng dy ?
5. Nguyn l lm vic ca rle bo v ct nhanh ? Nguyn tc chn dng khi
ng ca rle bo v ct nhanh ?
6. Nguyn l lm vic ca rle qu dng ? Nguyn tc chn dng khi ng ca
rle bo v ?
7. Nguyn l lm vic ca rle km p ? Nguyn tc chn dng khi ng ca
rle bo v ?
8. Nguyn l lm vic ca bo v so lch dc my bin p ? Nguyn tc chn
dng khi ng ca rle bo v ?
9. Nguyn l lm vic ca bo v khong cch ? Nguyn tc chn dng khi
ng ca rle bo v ?
10. Nguyn l lm vic ca rle qu dng c hng ? Nguyn tc chn dng
khi ng ca rle bo v ?
11. Nu cc chc nng ca cc loi rle k thut s hin c ca X nghip cho
cc loi rle bo v :
- Rle khong cch .
- R le qua sdng .
- R le so lch.
12. Cch khai thc cc thng tin trn cc loi r le k thut s ?
13. Bo v tn s thp F81 l g ? Nguyn tc chnh nh ca bo v ny nh
th no ?
14. Ti sao phi t thit b t ng lai trn ng dy ?
15. Quy trnh vn hnh cc rle bo v k thut s mt s hng nc ngoi ang
lp t ti cc trm ca x nghip .
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PHN V : VN HNH TRM V CNG TC IU H THNG
IN .
1. c im vn hnh trm ?
2. Nhng yu cu i vi nhn vin vn hnh trm ?
3. nhim v chung ca nhn vin vn hnh trm bin p trong ch lm vic
bnh thng ?
4. Nhim v ca trc chnh - nhn vin vn hnh trm bin p ?
5. Nhim v ca trc ph - nhn vin vn hnh trm bin p ?
6. Ch giao nhn ca ca nhn vin trc trm bin p ?
7. Nhim v ca trm trng ?
8. Th no l tro lu cng sut ?
9. H thng iu ca h thng in Quc gia t chc nh th no ?
10. Th no l quyn iu khin ca mt cp iu ?
11. Th no l quyn kin tra ca mt cp iu ?
12. Chc nng nhim v ca cng tc iu l g ?
13. Hy nu nhng th tc khi a mt thit b ra sa cha , a vo vn hnh
sau khi sa cha xong ?
14. Hy nu nhng quy nh phn cp iu khin , kim tra ca iu min
cho cc thit b ca trm ni anh, ch ang lm vic ?
15. Cc quy nh v iu chnh in p trong h thng in ?
- nh hng ca in p ti li in nh th no .
- Cch thay i tn tht in p .
- Cch thay i in p ti cc im nt, ti u li in .
16. Cc nhn vin vn hnh trm tham gia iu chnh in p trong h thng
in nh th no ?
17. Cc quy dnh v iu chnh tn s h thng in ?
- nh hng ca tn s ti cc ph ti .
- Cc bin php iu chnh tn s .
18. Cc nhn vin vn hnh trm tham gia cc cng vic g gp phn iu
chnh tn s ?
19. Quy trnh vn hnh v x l s c my bin p lc ?
- Quy nh v vn hnh my bin p ch bnh thng, ch s c .
- Quy nh v ch kim tra my bin p trong vn hnh .
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- Quy nh v cc th tc a my bin p vo vn hnh sau khi i tu
sa ch xong .
- Quy nh cc th tc cn thit khi a my bin p mi lp t vo vn
hnh .
- Quy nh v qun l du my bin p .
- ngha cho 2 my bin p vn hnh song song .
- iu kin 2 my bin p vn hnh song song .
- Gii thch ngha tng iu kin .
- Cch x l s c my bin p .
- Cch x l bt bnh thng ca my bin p
- Cc trng hp phi tch my bin p ra khi vn hnh .
- Quy nh v lm mt my bin p .
- Quy nh v mc du trong bnh du ph, quy nh v nhit lp du
trn cng ca my bin p .
- Quy nh v im trung tnh cun dy 110kV ca my bin p
20. Quy trnh vn hnh my ct in ? Quy trnh vn hnh dao cch ly
21. Quy trnh vn hnh my bin in p, my bin dng ?
22. Quy trnh vn hnh cc thit b t ca X nghip ?
23. Quy trnh nh s thit b do B Cng nghip ban hnh ?
24. Quy trnh thao tc cc thit b trong h thng in do B Cng nghip ban
hnh ?
- Cc quy nh c bn thao tc ng ct cc thit b .
- Thao tc my bin p.
- Thao tc my ct in .
- Thao tc dao cch ly.
- Thao tc ng dy ...
25. Quy trnh X l s c B Cng nhip ban hnh .
- Nguyn tc c bn x l s c trong h thng in .
- Quy nh cho nhn vin vn hnh x l s c trong h thng in.
- Quy nh x l khi mt in ton trm .
- Quy nh x l khi s c my bin p ca trm do bo v chnh lm vic
.
- Quy nh x l s c khi bo v d phong my bin p tc ng.
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- Quy nh x l s c khi cc ng dy trung p tc ng b s c r
le bo v tc ng ....
26. Phn tch kt cu s ca cc trm bin p 110kV hin c ti X nghip,
nh gi u nhc im ?
27. Trong cc trm bin p thanh ci c nhim v g, hy phn tch tng loi h
thng thanh ci .
28. Quy nh vn hnh h thng t dng trong trm , V s h thng t dng
trong trm .
29. Quy nh vn hnh h thng in 1 chiu, h thng in 1 chiu cp cho cc
ph ti no ?
30. Quy nh vn hnh h thng c quy ca trm, V s h thng chnh lu
cp in cho h thng mt chiu v np cho c quy ?
Phn thc hnh .
31. V v thuc s nht th trm anh chi ang lm vic, Ghi y cc
thng s tng thit b v quy nh nh s trn s ?
32. Thc hin khai thc cc thng tin trong rle k thut s ca trm anh ch
ang lm vic, ng thi khai thc cc thng tin trn rle k thut s trang b
cho cc trm ca X nghip ?
33. Vit phiu thao tc tch 1 ng dy ra sa cha ?
34. Vit phiu thao tc tch TU thanh ci trm ra sa cha ?
35. Vit phiu thao tc tch my bin p chnh ra sa cha ?
36. Vit phiu thao tc tch thanh ci 35kV, 22kV, 10kV, 6kV ?
37. Nm vng cc th tc v thc hin trong phiu cng tc ?
38. Thc hnh cc cng vic cho nhn vin vn hnh trm ?
39. Cch t v tho tip a di ng trong tram ?
40. Thc hnh thao tc a cc loi my ct vo vn hnh .
41. Cch u h thng qut mt my bin p ?
42. Sa cha mt s hng hc n gin ca my ngt ?
PHN VI : K THUT NG DY .
1. Li in truyn ti v phn phi l g, ngha ?
2. Ranh gii qun l gia ng dy v trm ?
3. Quy nh v hnh lang an ton cc cp in p ?
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4. Cc hng mc vf thi gian quy nh khi kim tra ng dy ban ngy, ban
m ( nh k, t xut , s c ) ?
5. Quy nh an ton trong cng tc kim tra m ng dy ?
6. Gii thch hin tng tng p cui ng dy khi khng ti ?
7. Tiu chun vn hnh ca ct, chui s, dy dn, dy chng st ?
8. Cng dng ca cc ph kin trn ng dy 110kV ?
9. ng dy (ct, dy dn) ti in thng chu nhng lc tc dng no ?
10. Lit k cc loi ct hin c trn ng dy ti in ?
11. Cho bit vai tr cc loi ct : thng, gc, no thng , no gc, vt,
dng?
12. V sao khong cch cc ct v cao cc ct khng u nhau ?
13. Lit k cc ph kin trn ct dng ?
14. Ct b nghing ( dc tuyn, ngang tuyn ) lm th no nhn bit ?
15. Cng dng ca b chng no ct? Thng x dng cho koi ct no ?
16. Cng dng ca mng ct in? Cc lc tc dng ln mng ct in ?
17. Cc bin php chng ln ct in, chng lt ct v chng nh mng no ?
18. Cc loi dy pha v cc c ai p hin c trn li in, gii thch ngha
cc loi dy pha ?
19. Dy nhm li thp, cng dng ca thp v nhm ?
20. Lit k cc loi dy chng st hin c trn ng dy ti in ?
21. Cho bit khong cch n t ca dy dn theo cp in p v vng dn c ?
22. V sao phi ni t lu ng ?
23. Cho bit gc bo v ca dy chng st ( cho 1 dy, cho 2 dy )
24. Ti sao c ng dy li phi dng 2 dy chng st, 1 dy chng st, khong
cch ngn nht gia dy dn v dy chng st ?
25. Gii thch hin tng st nh vo dy dn ?
26. Ti sao mt trong ca s li lm vo v c nhng ng cong nhp nh ?
27. V sao trong nhng cn ma u ma ta thng thy trn b mt ngoi ca
s b phng in chp tt ?
28. Ti sao c vi ni phng ca chui s nghing ( khng vung gc ) so vi
mt t ?
29. Cch nhn bit cp in p ca 1 ng dy ti in ang vn hnh ?
30. Ti sao c ct c 1 chui s c ct c 2 chui s song song trn mt pha ?
31. Chn loi s cch in vng nhim bn, thc hin nh th no ?
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32. ng dy c cp in p110kV vn hnh 35kV c c khng ?
33. ng dy c cp in p thp hn 110kV vn hnh in p 110kV phi
thc hin cc bin php g ?
34. Cc h s cn thit khi nghim thu qun l ng dy ?
35. Cng dng ca t b trn ng dy ?
36. Gii thch v sao ng dy cao th , dy chng st c ni t trc tip
vo ct hoc cch in ?
37. Khi thy dy t ri xung t hoc cn l lng ngi cng nhn phi lm
g ?
38. Khi cng tc trn ng dy vt ng st, ng t, ng lng c
ngi v xe c qua li, sng mng c thuyn b qua li th phi p dng bin
php g ?
39. Cht cy dc tuyn phi tun theo nhng quy nh g ?
40. o tip a ct cho php tin hnh khi ng dy ang vn hnh nhng phi
m bo cc iu kin g ?
41. Khi lm vic trn ng dy ct in nhng gn hoc giao cho vi
ng dy ang vn hnh th phi m bo cc iu kin g ?
42. ng dy ang vn hnh, khi sn x v phn trn ca ct phi thc hin
nhng quy nh g ?
43. Khi lm vic trn ng dy ct in nhng i chung ct vi ng dy
ang vn hnh th phi tun theo nhng quy nh g ?
44. Quy nh v hnh lang an ton li in theo nghi nh ca nh nc hin
nay l g ?
45. Vic kim tra bt thng cc ng dy trn khng hoc trn tng on
ng dy trn khng phi tin hnh nh th no ?
46. Thi gian quy nh v i tu 1 ng dy ?
47. Khong cch an ton t ng dy 110kV n cc ng dy trung th, h
th v thng tin ?
48. Nh th no l mi ni t yu cu k thut ?
49. S lch bao nhiu ( so vi phng ng ) th phi ko li ?
50. Tiu chun vn hnh cho php nghing ca x ?
Phn thc hnh .
48. Cch xc nh phm vi hnh lang ti hin trng ?
49. Lit k v nu cc dng c thi cng ?
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50. Cch s dng dy da an ton ?
51. Cch x l khi ct nghing ?
52. Trnh t trng 1 ct b tng bng t ?
53. Trnh t dng mt ct st ?
54. Trnh t lp x 110kV ( ct b tng ) ?
55. M t cch leo ct b tng, ct st ?
56. Cch sn ct st ?
57. Cch sa ca mng ct b tng ?
58. cch p chn ct st ?
59. Trnh t thao tc thay 1 chui s cng chui n ?
60. Trnh t thao tc thay mt chui s cng chui i ?
61. Trnh t thao tc thay 1 chui s ?
62. Cch buc ti quay cp ?
63. Cch i cp Puli i, n ?
64. Trnh t thu hi dy dn v vy chng st ?
65. Thao tc ra dy ( kim tra dy ) ?
66. Cch ly vng ca ng dy ?
67. Trnh t cng tc thay dy ?
68. Trnh t cng tc ko dy mi ?
69. Trnh t sang dy ct mi ?
70. Cch d tm im s c t dy pha chm t ?
71. Trnh t p ni 1 dy nhm li thp ( di t, trn cao ) ?
72. Cch cun tc dy 1 dy pha ?
73. B tr nhn lc, dng c thay mt on dy khi qua sng, ng t ?
74. Cch thay t chng rung ?
75. K thut lp v tho dy tip a lu ng ? Tiu chun ca tip a lu
ng ?
76. Dng c v cch o in tr tip a ct ?
PHN I : K THUT IN
1. in nng l g ?
in nng l mt dng nng lng c cc tnh cht sau :
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- D dng chuyn ho thnh cc dng nng lng khc nh : c nng, nhit
nng
- Khng th d tr c nh cc dng vt cht khc ngoi tr cc ngun in
mt chiu nh c quy, pin ..
- c to ra bng : sc gi, sc nc, nhit ( than , du ), nng lng khc nh
nguyn t, nng lng mt tri, gas .
- Rt nguy him nu s dng khng ng quy nh an ton.
- Tc dn truyn nng lng rt nhanh .
- n v o in nng l lng cng sut in s dng trong mt khong thi
gian, k hiu l A; n v o l kWh, Wh, MWh.
2. Dng in l g ? Tc dng ca dng in? Nu cng thc tnh dng in ?
- Dng in l dng chuyn ri c hng ca cc ht mang in trong
in trng.
- Chiu dng in theo quy c l chiu chuyn ng ca cc in tch
dng .
- Cc tc dng ca dng in:
+ Tc dng nhit ( lm cho vt dn nng ln )
+ Tc dng quang ( pht sng bng n )
+ Tc dng t.( trong my bin p )
+ Tc dng ha hc ( dng in chy qua cht in phn )
+ Tc dng sinh l
3. Hiu in th l g ? in p l g , n v o ?
- in th ti mt im M trong in trng l i lng c trng ring
cho in trng v phng din to ra th nng khi t ti mt in tch q.
N c xc nh bng thng s gia cng ca lc in tc dng ln q khi q di
chuyn t M ra v cc v ln ca q.
VM = MA
q
Trong : + VM l in th ti im M
+ MA l cng ca lc in tc dng ln q khi q di chuyn t
M ra v cc
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15
+q l ln ca in tch q.
- Hiu in th gia hai im M, N trong in trng c trng cho kh
nng sinh cng ca in trng trong s di chuyn ca mt in tch t M n
N. N c xc nh bng thng s gia cng ca lc in tc dng ln in
tch q trong s di chuyn t M n N v ln ca q.
UMN = VM - VN = MNA
q
Trong : + VM, VN l in th ti im M, N.
+MNA l cng ca lc in tc dng ln q khi q di chuyn t
M n N.
+q l ln ca in tch q.
Hiu in th trong h SI tnh bng Vn ( V ), mt Vn l hiu din th
gia hai im M,N khi dch chuyn in tch dng 1 Culng (+1C) t M n
N, thc hin cng dch chuyn l 1 Jun .
4. in trng , cng in trng l g ?
- in trng l mt dng vt cht (mi trng) bao quanh in tch v
gn lin vi in tch. in trng tc dng lc in ln cc in tch khc t
trong n
Mt in tch Q nm ti mt im trong khng gian s gy ra xung quanh
n mt in trng. Mt in tch q nm trong in trng s b Q tc dng
mt lc in. Ngc li, q cng gy ra mt in trng tc dng ln Q mt lc
trc i.
QqF
qQF
- Cng in trng ti mt im l i lng c trng cho tc dng
lc ca in trng ti im . N c xc nh bng thng s ca ln
lc in F tc dng ln mt in tch th q (dng) t ti im v ln
ca q.
+
+
Q
O
q
M
-
16
E = F
q
Trong : - E l cng in trng ti im m ta xt
- F l ln ca lc in tc dng ln in tch th.
- q l ln ca in tch th.
5. T trng l g ?
- T trng l mt dng vt cht tn ti trong khng gian m biu hin c
th l s xut hin ca lc t tc dng ln mt dng in hay mt nam chm t
trong n.
- Nam chm v dy dn mang dng in sinh ra trong khong khng gian
xung quanh n mt t trng.
- pht hin s tn ti ca t trng trong mt khong khng gian no
, ngi ta s dng kim nam chm nh, t ti nhng v tr bt k trong khong
khng gian y. Nu khng c tc dng ca t trng ca dng in hay mt
nam chm th kim nam chm ni trn lun nm theo hng nam - bc. Khi c
tc dng ca t trng ca mt dng in hay mt nam chm, kim nam chm
ni trn s quay n mt v tr cn bng xc nh; v tr ny ph thuc vo ch
t kim nam chm trong t trng.
6. Phn bit in mt chiu v in xoay chiu hnh sin ?
- Dng in mt chiu ( l tng ) : L dng in c ln v chiu khng i
theo thi gian.
- Dng in xoay chiu ( iu ho hnh sin ) : L dng in c ln v chiu
thay i theo thi gian vi mt quy lut hnh sin .
7. Chu k dng in xoay chiu ( hnh sin ) l g ? Tn s dng in xoay
chiu ( hnh sin ) l g, n v o ?
- Chu k dng in xoay chiu : L thi gian gia hai ln lp li lin tip
mt trng thi ging nhau ca dng in.
K hiu l T, n v o l giy (s).
- Tn s dng in xoay chiu : L s chu k dng in xoay chiu trong
mt n v thi gian (s).
-
17
K hiu l f, n v o l Hez ( Hz ).. Tn s dng in xoay chiu nc
ta l 50 Hz.
T cng thc :
1
f = ----------
T
Suy ra : 1 1
T = ------- = ------ = 0,02s
F 50
8. in tr l g ?
- in tr l i lng vt l c trng cho s cn tr dng in ca vt
mang in.
n v o in tr l Ohm ( )
9. in tr phi tuyn l g ?
- in tr phi tuyn l in tr c gi tr thay i theo in p t ln n.
- in p bnh thng ( in p nh mc ) R ln.
- in p tng cao R gim .
in tr phi tuyn c c tnh VA l mt ng cong.
- Cng dng : Ch to chng st van .
10. Nu cng thc tnh in tr ? Gii thch ngha, n v tnh ca mi i
lng trong cng thc tnh ?
1. nhit nht nh, in tr ca dy dn ng cht hnh tr c tit din S,
chiu di l, c th tnh bng cng thc n gin , c thit lp bng th nghim
:
- Cng thc tnh in tr:
R = .l
S
Trong :
R : in tr, tnh bng ohm ( )
-
18
: l in tr sut ca dy dn.( m )
l : l chiu di ca dy dn ( m )
S : tit din ca dy dn .m2
Cc cht in mi c in tr sut rt ln, c th ti 108 m . Kim loi c
in tr sut rt nh khong 10-8 n 10-6 m.
in tr sut ca vt liu 200C
Vt liu in tr sut ( m )
ng
Nhm
St
Vng
Bc
Ch
Km
Wonfram
Niken
Platin
Thic
Thu tinh
S
H phch
1,72.10-8
2,63.10-8
10.10-8
2,2.10-8
1,6.10-8
20,8.10-8
5.92.10-8
5,55.10-8
8,69.10-8 mm, 9,52.10-8 cng
10,3.10-8
11,4.10-8
109
1013
1019
2. Tnh theo nh lut ohm ta c :
U
R = -------
I
Trong :
U : Hiu in th ( V )
I : Cng dng in ( A )
R : in tr ( )
Ohm ( ) l in tr ca vt dn ng cht sao cho khi hai u vt dn
c hiu in th khng i 1 vn ( V ) th trong vt dn c dng in cng 1
ampe ( A ) chy qua
-
19
11. Tnh in tr tng ng trong mch ni tip, song song ?
- Mch ni tip :
Rt = R1 + R2 + .. + Rn
- Mch song song :
1/Rt = 1/R1 + 1/R2 + . + 1/Rn
12. Cho bit in tr ph thuc vo nhit d ?
Bng th nghim ngi ta nhn thy khi nhit tng , in tr ca bt k
kim loi no cng tng, cn i vi cht in phn th hin tng s ngc li,
in tr ca dung dch in phn gim khi nhit tng .
Cng thc biu th s ph thuc ca in tr vo nhit :
R = R0 ( 1 + t )
Vi :
R : in tr vt dn ( )
R0 : in tr vt dn 00C
: H s nhit ca in tr . 1/ 0C
t : Nhit ca vt ti thi im ta tnh ( 0 C )
Bng h s nhit ca mt s cht .
Vt liu H s nhit ( 1/ 0C )
ng thanh
Nhm
St
Thp
Vng
Bc
Ch
Km
0,0040
0,0040
0,00657
0,0045
0,00365
0,0036
0,00428
0,00419
-
20
Niken
Thic
Platin
Wonfram
0,0044
0,0044
0,00392
0,00468
Hin tng siu dn: khi nhit h xung di mt nhit T0 no
in tr ca kim loi ( hay hp kim ) gim t ngt n gi tr bng khng.
Hin tng gi l hin tng siu dn.
13. Khi no cn in tr ln, khi no cn in tr nh ?
Nhng ch cn cch in th in tr cng ln cng tt. V d : S cch
in, v dy dn, ng, gng tay, so cch in
Cn in tr nh ti nhng ch tip xc, mi ni, h thng ni t.
14.Cm khng l g ? Cng thc tnh cm khng, n v o ?
- Khi dng in xoay chiu chy trong cun dy s xut hin i lng xu
hng cn tr dng in , i lng ny gi l cm khng.
- Cng thc tnh: XL = L, n v o l .
Trong : XL l cm khng.
- L l t cm ca cun dy.
- l tn s gc. = 2f vi f l tn s dng in.
15. Dung khng l g? Cc cng thc tnh dung khng, n v o ?
- Dung khng l mt i lng c trng cho kh nng cn tr dng in
xoay chiu i qua t in.
- Cng thc tnh: XC = 1/ C.
Trong - XC l dung khng.
- C l in dung ca t in.
- l tn s gc. = 2f vi f l tn s dng in.
16. Tng tr l g? Cng thc tnh ?
-
21
Tng tr l mt i lng vt l c trng cho mch in xoay chiu, th
hin mi quan h gia in p t ln mch v dng in chay qua mch ( s
cn tr i vi dng in xoay chiu )
K hiu : Z n v :
Ta c theo nh lut ohm : Z = u/i
u : Hiu in th xoay chiu t ln mch. ( V )
i : Dng in xoay chiu chy trong mch ( A )
Hoc : Z = R2 + ( RL - Rc )2
Trong :
R : in tr thun .
RL = XL : Cm khng
RC = XC : Dung khng.
17. Cc dng cng sut ? n v tnh tng i lng ? Quan h gia cc
cng sut ?
- Cng sut tc dng P l cng sut trung bnh trong mt chu k:
Sau khi tnh ton ta c: osP UIc
n v o cng sut tc dng l W, kW, MW
Cng sut tc dng P c trng cho s bin i in nng thnh cc dng
nng lng khc nh c nng, nhit nng v.v...
- Cng sut phn khng Q c trng cho cng qu trnh trao i nng
lng in t trng. Cng sut phn khng c tiu th ng c khng
ng b, my bin p, trn ng dy in v mi ni c t trng.
Biu thc tnh ton: sinQ UI
Cng sut phn khng c th c tnh bng tng cng sut phn khng
ca in cm v in dung cc nhnh trong mch in:
2 2L C Ln n Cn nQ Q Q X I X I
Trong : XLn, XCn, In ln lt l cm khng, dung khng, dng in mi
nhnh.
n v o ca Q l VAr, kVAr hoc MVAr.
- Cng sut biu kin S hay cng sut ton phn bao gm cng sut tc
dng v cng sut phn khng, c nh ngha di dng biu thc sau:
-
22
S = UI = 2 2P Q
n v o ca S l VA, kVA hoc MVA.
- Quan h gia S, P, Q c m t bng mt tam
gic vung, trong S l cnh huyn, P v Q l hai cnh
gc vung. Tam gic nh hnh bn gi l tam gic cng
sut.
P = S cos
Q = S sin
Q
tg = ----- = arctgQ/P
P
18. Nu nhng thit b cung cp cng sut tc dng, phn khng , Thit b
no tiu th cng sut tc dng, cng sut phn khng ?
- Cc thit b tiu th cng sut phn khng l : ng c khng ng b, n
hunh quang , my bin p, cun khng in, l h quang
- Cc thit b cung cp cng sut phn khng : T in b ngang, my b ng
b, my pht vn hnh ch b ( qu kch t ).
Ngoi ra c thit b va cung cp va tiu th cng sut phn khng :
ng c ng b, my b ng b ..
- Cc thit b cung cp cng sut tc dng : Cng sut tc dng c cung cp
t cc my pht in ca cc nh my in . ( thu in, nhit in, in nguyn
t, Diesel )
- Cc thit b tiu th cng sut tc dng l cc thit b ng lc , ng c, my
bm, cc l in, l cao, nh sng sinh hot
19. H s cng sut l g ? ngha v cch nng cao h s cng sut ?
- H s cng sut l t s gia cng sut tc dng P v cng sut biu
kin S.
P
Cos = -------
S
P : Cng sut tc dng .
Q
P
S
-
23
S : Cng sut biu kin.
- ngha ca vic nng cao h s cng sut cos:
1. My pht in lm vic vi dng v in p nh mc, vi Cos = 1 s pht
ra cng sut tc dng t l vi Cos. Cos cng thp, cng sut tc dng pht ra
cng b v do khng tn dng c kh nng pht cng sut tc dng ca
my pht in .
2. Ph ti dng in yu cu mt cng sut tc dng nht nh vi in p U t
bin i. Nu Cos thay i, dng in s thay i. Dng in ti tiu th t l
nghch vi Cos; Cos cng thp, dng in ti tiu th cng ln. Dng in
tng s tng tn tht in p v in nng trn ng dy.
3. Nu cos cng thp, tn tht in p cng ln, do m bo in p
khng gim qu nhiu ta phi tng tit din dy dn, lm tng vn u t xy
dng ng dy .
- Mt s nht xt
+ Gim c lng cng sut phn khng truyn ti trn ng dy t
gim tn tht cng sut v tn tht in p trong mng in.
+ Tng kh nng truyn ti ca ng dy v my bin p.
+ Tng kh nng pht cng sut tc dng ca cc my pht in.
- Cc bin php nng cao h s cng sut cos:
+ Nng cao h s cng sut cos t nhin: l tm cc bin php cc h
tiu th in gim bt c lng cng sut phn khng tiu th nh gim thi
gian chy khng ti ca cc ng c, thay th cc ng c thng xuyn chy
non ti bng cc ng c hp l hn...
+ Nng cao h s cng sut cos bng bin php b cng sut phn
khng. Thc cht l t cc thit b b ti cc nt trn h thng m thiu
cng sut phn khng (biu hin in p vn hnh thp) hoc gn cc h tiu
th in cung cp cng sut phn khng theo yu cu ph ti.
20. Cch tnh h s cng sut? Cng thc tnh dng in ?
-
24
a. Cch tnh h s cng sut :
- Mch mt pha :
P P
T cng thc : P = U.I Cos Cos = ------- = ----
U.I S
P
S = P2 + Q2 Cos = ---------------
P2 + Q2
Vi : P : Cng sut tc dng.
Q : Cng sut phn khng.
S : Cng sut biu kin.
- Mch ba pha i xng :
P = 3 U.I Cos
P
Cos = --------
3 U.I
b. Cng thc tnh dng in :
- Mch mt pha :
I = U/Z
I : Gi tr hiu dng ca dng in .( A )
U : Gi tr hiu dng ca in p .( V )
Z : Tng tr ( )
- Mch ba pha i xng :
S
I = ------
3 U
P
Hoc : I = ----------
3 UCos
-
25
21. Tit din dy dn c chn cn c vo nhng i lng no ?
* Tit din dy dn c chn theo mt dng in kinh t.
tbkt
kt
IS
J
Trong : - Skt l tit din dy dn (mm2)
- Itb l dng in trung bnh qua ph ti.
- Jkt: mt dng in kinh t (A/mm2)
Bng 1. Mt dng in kinh t
Tn
Mt dng kinh t A/mm2 vi thi gian s
dng cng sut cc i, gi
1000 - 3000 3000 - 5000 5000 - 8760
- Thanh dn (gp):
ng
Nhm
2,5
1,3
2,1
1,1
1,8
1,0
- Cp in lc cch in
bng giy tm du li:
ng
nhm
3,0
1,6
2,5
1,4
2,0
1,2
* Kim tra theo iu kin pht nng lu di :
Icpbt Icb = Ilvmax
Icpbt : Dng in cho php bnh thng. Gi tr c hiu chnh theo
nhit .
Icb : Dng in cng bc .
Ilvmax : Dng in lm vic cc i.
* Kim tra theo iu kin vng quang :
Uvq Udmht
Trong : Uvq : in p ti hn c th pht sinh vng qung.
Udmht : in p nh mc ca h thng
-
26
Nu dy dn 3 pha b tr trn nh ca tam gic u gi tr Uvq trong iu
kin thi tit kh ro v sng, p sut khng kh l 760mmHg, nhit mi
trng xung quanh 250C c th xc nh theo cng thc sau:
Uvq = 84.m.r.lg a/r ( kV )
Trong : r : bn knh ngoi ca dy dn.
a : Khong cch gia cc trc dy dn.
m : H s xt n x x ca dy dn. i vi dy mt si,
thanh dn lu ngy trong khng kh m = 0,93 - 0,98. i vi dy nhiu si
xon ly m = 0,83 - 0,87
22. T in l g, cu to v c im ca t in ? Cc cng thc lin quan
n t in ?
- T in l mt h hai vt dn t gn nhau v ngn cch nhau bng mt
lp cch in (in mi). T in thng dng tch v phng in trong
mch in, mun tch in cho t in ngi ta ni hai bn cc ca t in vi
ngun in, bn ni vi cc dng s tch in dng, bn ni vi cc m s
tch in m. Khi t in c tch in th in trng trong t in s d tr
mt nng lng, l nng lng in trng.
- i lng c trng cho kh nng tch in ca t in mt hiu in
th nht nh gi l in dung ca t in. N c xc nh bng thng s
gia in tch ca t in v hiu in th gia hai bn ca n.
QC
U
- Cu to : thng l loi t giy ngm du c bit, gm hai bn cc l
cc l nhm di c cch in bng cc lp giy. Ton b c c nh trong
mt thng c hn kn, hai u bn cc c a ra ngoi nh hai s xuyn .
- c im :
+ Trong t in , in tch cc cc ca t in bng nhau v gi tr
nhng ngc nhau v du .
+ T in ch yu tch lu ( v gii phng ) nng lng in trng .
+ Tn hao do in tr nhit t rt nh .
+ T in cho dng in xoay chiu ( AC ) i qua nhng ch np v
phng in tch trong mch mt chiu ( DC ).
-
27
23. Tnh in dung mc ni tip v mc song song , hn hp .
- in dung ca b t mc ni tip: 1/Ct = 1/C1 + 1/C2 + ... + 1/Cn
- in dung ca b t mc song song: Ct = C1 + C2 + ... Cn.
24. Nguyn l cm ng in t l g ?
- Hin tng cm ng in t: Khi t thng qua mch kn bin thin th
trong mch kn xut hin sc in ng cm ng. Hin tng cm ng in t
ch tn ti trong khong thi gian t thng qua mch kn ( khung dy ) bin
thin .
V d : T thng qua mt din tch gii hn bi khung dy ( vng dy ):
= BS Cos
Trong : : T thng
B : T trng xuyn qua vng dy.
S : Din tch khung dy .
: L gc to bi vc t n vung gc vi khung v vc t B.
T : ec = -/t
ec : Sc in ng cm ng.
: bin thin t thng
25. H cm l g? Nu tc dng tng h ca 2 dy dn thng song song
mang in ?
1. H cm l g :
- Hin tng h cm l hin tng xut hin t trng trong mt cun
dy do dng in bin thin trong cun dy khc to nn.
- T thng h cm trong cun dy 2 do dng in i1 to nn l:
21 1Mi vi M l h s h cm gia 2 cun dy.
- Khi i1 bin thin s to nn in p h cm t ln cun dy 2:
21 121d di
u Mdt dt
- Tng t in p h cm ca cun dy 1 do dng in i2 bin thin to
nn l:
-
28
12 212
d diu M
dt dt
2. Tc dng tng h ca 2 dy dn thng song song mang in .
Lc tc dng gia hai thanh dn thng song song mang in th t l
thun vi tch cc dng in trong cc thanh dn v t ln nghchvi khong
cch gia hai thanh. Lc tc dng gia cc thanh dn s l lc ko ( ht ) nu
cc dng trong hai thanh dn l cng chiu vi nhau; trng hp ngc li s l
lc y .
2I1I2
F = k --------- l
r
Trong :
F : Lc tc dng tng h ln mt on dy di l
l : Chiu di ca on dy dn. ( m )
I2.I2 : Cng dng in ( A )
0
H s : k = --------
4.
Trong :
: t thm mi trng
0 : t thm trong chn khng.
0 : 4.10-7
H/m = 1,26.10-6
H/m
26. Hin tng t cm ?
- Hin tng t cm l hin tng cm ng in t xy ra trong mt mch
in c dng in m s bin thin t thng qua mch c gy ra bi s bin
thin ca cng dng in qua mch.
- Khi trong mch in c cng dng in bin thin th trong mch
xut hin sut in ng t cm. Gi tr ca n c tnh theo cng thc:
etc = d
dt
=
diL
dt -L I/t
Trong : - etc l sut in ng t cm.
- l t thng mc vng vi dy dn. = L.i
-
29
- L l t cm ca cun dy.
27. Cng dng ca o pha ca ng dy truyn ti in ?
- V ng dy truyn ti in c s cm ng gia cc pha vi nhau. Mt
khc dy dn b tr nm ngang nn xut hin dung khng gia dy dn vi dy
dn, gia dy dn vi mt t khng i xng cc thng s L, C gia cc pha, v
vy ngi ta phi o pha .
- Cng dng ca o pha ng dy truyn ti cao p l cn bng in
khng v in dung tng h gia cc pha t lm cn bng in p gia cc
pha cui ng dy ti in v cn bng in dung tng h gia cc pha .
28. Nguyn tc hot ng ca my pht in 1 chiu , xoay chiu ?
My pht in mt chiu :
a. Cu to : Gm mt khung dy c th quay xung quanh trc i xng ca n
trong t trng u. T Trc quay vung gc vi t trng ).
- Mt b gp in gm hai vnh bn khuyn v hai chi qut ly in ra
mch ngoi.
b. Hot ng : Da trn hin tng cm ng in t. Khi t thng qua khung
dy bin thin iu ho lm pht sinh khung dy mt sc in ng cm ng
cng bin thin iu ho. Dng in trong khung l dng in xoay chiu,
nhng b tr hai vnh bn khuyn nn khi dng in trong khung dy i chiu
th vnh bn khuyn i chi qut, nn chi a lun lun c dng in i qua
mch ngoi v chi qut b lun lun c dng in t mch ngoi i vo. Vy
chi a chnh l cc dng v chi b chnh l cc m ca my pht in mt
chiu ny. Dng in pht ra l dng in mt chiu .
29. Nguyn l to ra dng in xoay chiu ?
Cho mt khung dy kim loi c din tch gii hn bi khung l S, c N
vng dy, quay quanh trc i xng xx' ca n trong mt t trng u B c
phng vung gc vi xx' . Khung quay vi vn tc . Gi s lc t = 0, php
-
30
tuyn n ca khung trng vi phng, chiu ca t trng B. Ti thi im t, n
quay c mt gc , lc ny t thng qua khung dy l :
= NBSCost
V t thng qua khung dy bin thin nn trong khung dy xut hin mt
sc in cm ng :
d
e = ------ = NBSCost
Dt
Hay : e = E0sint
Vi E0 = NBS : s in ng cc i.
Nh vy, sc in ng trong khung dy bin thin iu ho.
Nu ni hai u ca khung vi mch ngoi th trong mch c dng in
bin thin iu ho, gi l dng in xoay chiu .
30. Quan h dng , p trong mch xoay chiu thun tr, thun cm, thun
dung R, L, C ni tip, song song v hin tng cng hng ?
Mng in xoay chiu c u = Uosint.
1. thun tr :
u Uo
i = ---- = ---- sint
R R
2. Thun cm :
u Uo
i = ----- = ------ Sin(t +/2)
XL L
3. Thun dung :
u
i = ------ = UoCSin(t - /2)
XC
4. Mch R, L, C mc ni tip :
-
31
Uo
i = ------ sin(t + )
Z
Uo
i = --------------------- Sin(t + )
1
R2 + ( L - ----- )2
C
L - 1/C L - 1/C
Vi tg = ------------ hay = arctg -------------
R R
5. Mng R, L, C mch song song :
u 1 1 1 1
i = ------ m ---- = ----+ ----- + -----
Z Z R L 1/C
u = Uosin(t + )
1 1 1
i = Uo ( ---- + ----- + ------ ).sin(t + )
R L 1/C
6. Hin tng cng hng khi XL = XC :
Lc ny Z = R2 +(XL - XC)2 = R
XL - XC
tg = ---------- = 0 = 0
Uo U
i = ----- sint hay : I = Imax = -----
R R
31. Cch to ra h thng in xoay chiu 3 pha, xoay chiu 3 pha 4 dy ?
Ba cun dy ging nhau ( phn ng ) gi l stato ( phn ng yn ) , t lch
nhau 120 nm trong t trng do nam chm in ng trc bn trong ( phn
quay ) hay cn gi l rto ( phn cm ). Khi rto quay t trng do nam chm
-
32
in sinh ra s qut qua cc cun dy stato, theo nh lut cm ng in t,
trong 3 cun dy sinh ra sc in ng cm ng bng nhau v ln v lch
nhau 120 ( v pha ).
Su u dy ca 3 cun cm u li vi nhau theo kiu hnh sao th ta c
mng xoay chiu 3 pha 4 dy kiu hnh sao.
Su u dy ca 3 cun cm nu u vi nhau theo kiu hnh tam gic th
ta c mng xoay chiu 3 pha 3 dy kiu tam gic .
( hnh v )
Mng xoay chiu 3 pha 4 dy l mng trong 3 dy pha v 1 dy trung
tnh. in p dy ( U dy ) l in p c ly ra t hai dy pha. Ta c UdyAC
,U dyBC , UdyAB . in p pha ( U pha ) l in p c ly ra t 1 dy pha v
dy trung tnh. Ta c : UAN, UBN, UCN .
( hnh v )
32. Quan h gia in p pha, in p dy, dng in pha, dng in dy
trong mch u sao, tam gic, cng sut mng xoay chiu 1 pha, 3 pha ?
1. Mng in hnh sao :
Ud = 3Up
Id = Ip
P = 3UpIp = 3 UdIp = 3UdId
2. Mng in hnh tam gic .
Ud = Up
Id = 3Ip
P = 3UpUp = 3UdId
33. Phn tch mng 3 pha trung tnh cch in ( khng ni t ) ?
a) Tnh trng lm vic bnh thng.
Trn hnh 33-1 l s mng in n
gin gm my pht, ng dy v ph ti.
A
B
C
ICC ICB ICA
Hnh 33-1
-
33
Mi pha ca mng in i vi t c mt in dung phn b ri dc theo
chiu di ca ng dy. n gin coi mng in 3 pha l i xng v cc
in dung C c t tp trung gia ng dy.
in dung gia cc pha vi nhau v dng in dung do chng to nn
khng tnh n v chng khng nh hng n tnh trng lm vic ca im
trung tnh.
- th vc t ca in p v dng in trng
thi lm vic bnh thng (hnh 33-2):
Trong ch lm vic bnh thng in p gia
cc pha i vi t i xng v c tr s bng in
p pha. Tng hnh hc cc dng in in dung ca
3 pha bng khng v khng c dng in chy
trong t:
CA CB CCI I I= =& & & ; 0C CA CB CCI I I I
& & & &
A B C fU U U U & & & & ;
0' 0A B CU U U U= + + =& & & &
b) Khi c mt pha chm t.
S mng in ba pha trung tnh cch in i vi t c pha C chm t trc
tip (hnh 33-3).
- Gi s khi pha C chm t trc tip,
in p ca pha C i vi t bng khng
U'C = 0, in p hai pha cn li dch chuyn
i mt vct (-U'C) tc l coi ti ch chm
t t thm mt in p (-U'C):
'A A C ACU U U U= - =& & & &
'B B C BCU U U U & & & &
' 0C C CU U U= - =& & &
' ' 'AB A B ABU U U U & & & &
Du , pha trn biu th cho ch
chm t.
UA
UB UC
ICA
ICB
ICC
Hnh 33-2
A
B
C
ICB ICA
Hnh 33-3
UA
UB UC
ICA
ICC
Hnh 33-4
0
0
UAB
UB
UA
ICB
-IC
-
34
th vc t ca in p v dng in khi pha C chm t (hnh 33-4).
T th vc t ta thy:
+ in p hai pha khng s c tng ln 3 ln:
' ' 3A B AU U U= =
+ Nn gi tr dng in dung ca hai pha khng s c tng ln 3 ln so
vi khi cha chm t:
' 3 ;CB CBI I ' 3 ;CA CAI I=
Dng in dung ca pha chm t bng khng: I'CC = 0.
- Dng in dung ti ch chm t:
+ ng dy trn khng: .
'350
dC
U LI (A)
+ ng dy cp: .
'10
dC
U LI = (A)
Trong :
+ Ud: in p dy, (kV).
+ L: chiu di tng cc ng dy c ni in vi nhau, km.
* Nhn xt:
- Khi mt pha chm t trong h thng c trung tnh cch in vi t:
+ in p dy khng thay i v tr s v lch nhau mt gc 1200, vic
cung cp in cho cc h tiu th u vo in p dy khng b nh hng v
vn lm vic bnh thng.
+ in p ca pha chm t bng khng, in p ca hai pha cn li tng
ln 3 ln v bng in p dy.
+ in p ca im trung tnh tng t khng n in p pha.
+ Dng in in dung ca cc pha chm t tng 3 ln, cn dng in
dung ti ch chm t tng ln 3 ln so vi dng in dung mt pha trc khi
chm t.
- V in p dy khng thay i v dng in dung chm t rt nh so vi
dng in ph ti nn mng in vn lm vic bnh thng khi chm t mt
pha. Tuy vy, i vi cc mng in ny khng cho php lm vic lu di khi
mt pha chm t v l do sau:
+ Khi chm t mt pha, in p hai pha cn li tng 3 ln, nhng ch
cch in yu c th b chc thng v dn n ngn mch gia cc pha.
-
35
Khc phc nhc im: cch in pha ca mng in v cc thit b in
trong mng phi thit k theo in p dy, nhng gi thnh ca thit b tng ln.
+ Dng in dung s sinh h quang, c th t chy cch in ti ch chm
t v dn n ngn mch gia cc pha.
+ Vi mt tr s dng in in dung nht nh, h quang c th chy chp
chn. V mng in l mt mch vng dao ng (R-L-C), hin tng chy chp
chn s dn n qu in p, c th ti (2,53) ln in p nh mc. Do ,
cch in cc pha khng chm t d b chc thng, dn n ngn mch gia
cc pha, mc d cch in c ch to theo in p dy.
34. Phn tch mng 3 pha trung tnh ni t qua cun dp h quang ?
Nh trn phn tch, trong
mng 3 pha trung tnh cch in vi
t, khi xy ra chm t mt pha dng
in dung s sinh h quang c th t
chy cch in ti ch chm t v
dn n ngn mch gia cc pha. Bin
php khc phc l gim cng bc
dng in chm t ti tr s m h quang khng th t duy tr c bng cch
ni trung tnh ca mng qua cun dp h quang (hnh 34-1).
Cun dp h quang l cun cm c li thp, t trong mt thng cha du
my bin p. in khng ca cun dp h quang c iu chnh bng cch
thay i s vng dy hoc khe h ca li thp.
- Trong ch lm vic bnh thng ging trng hp trung tnh cch in
i vi t: in p t ln cun dp h quang v dng in in dung chy
trong cun dp h quang bng khng.
- Khi chm t mt pha (pha C): in p trn cun
dp h quang tng ln bng in p pha, trong cun dp
h quang xut hin dng in in cm IL (chm sau
in p im trung tnh 900).
Kt qu ti ch chm t c dng in in dung
A
B
C
ICC ICB ICA
Hnh 34-1
IL IL IC
UC
IL IC
Hnh 34-2
-
36
IC v dng in in cm IL ngc pha nhau (Hnh 4-2) hay IL lm gim dng
IC. Nu iu chnh in khng ca cun dp h quang thch hp, dng in ti
ch chm t bng khng.
* Nhn xt:
- Trong thc t vn hnh phi ng ct ng dy lm dng in in dung
IC thay i, nn kh thc hin c IL = IC.
Mt khc, phi iu chnh sao cho: I = IL- IC, cung cp cho rle tc
ng bo tn hiu chm t cho nhn vin trc vn hnh bit kp thi s l v sa
cha.
- Nu mng in lm vic vi ton b ng dy m hiu chnh cun dp h
quang sao cho IC > IL, tc l b thiu. Khi c mt s ng dy b ct i th
I gim i, khng m bo cho rle tc ng nn c th khng nhn bit
c tnh trng chm t mt pha trong mng.
- Nu chn xL ca cun dp h quang sao cho khi tt c ng dy lm vic c
IL > IC, tc l b tha. Khi c mt s ng dy b ct s lm tng gi tr I,
cng lm cho r le d tc ng, d dng pht hin c chm t mt pha.
Tm li, trong li in ba pha c trung tnh ni t qua cun dp h
quang, cn phi b tha IL > IC
35. Phn tch mng 3 pha trung tnh trc tip ni t ?
- Cc mng c in p t 110kV tr
ln u c trung tnh trc tip ni t v:
+ Dng in dung ca mng rt ln
do in p cao v chiu di ng dy
ln.
+ Mng trung tnh trc tip ni t, cch
in ch cn thit k theo in p pha: v
bt k ch bnh thng hay chm t, in p cc dy dn u khng vt
qu in p pha. Nh vy chi ph u t cho cch in s gim i rt nhiu.
- Nhc im ca mng in 3 pha trung tnh trc tip ni t:
+ Khi c chm t mt pha (ngn mch 1 pha): dng in ngn mch rt
ln, rle s tc ng ct nhanh ng dy b s c, nh hng ti tnh lin tc
cung cp in.
A
B
C
Hnh 35-1
IN
in cc ni t
-
37
nng cao hiu qu lm vic ca mng in, nn dng thit b t ng
ng lp li t ng ng li cc ng dy b ct khi s c, v phn ln
cc s c chm t 1 pha c tnh cht thong qua.
+ Dng in chm t mt pha ln, nn thit b ni t phc tp v t
tin.
+ Dng chm t mt pha c th ln hn dng ngn mch ba pha. hn
ch n phi tng in khng th t khng bng cch khng ni t trung im
mt vi my bin p ca h thng hay ni t trung tnh qua in khng nh.
- Mng in ba pha in p > 1000V trung tnh ni t trc tip hay qua
khng in nh gi l mng in c dng in chm t ln.
- Mng in ba pha in p < 500V (380/220V hay 220/127V): lm vic
vi trung tnh trc tip ni t khng phi v nguyn nhn tit kim cch in
(cch in ca mng ny rt r), m xut pht t an ton cho ngi.
y l mng in sinh hot, xc sut ngi chm phi in tng i ln.
Nu trung tnh ca mng cch in vi t, khi mt pha chm t tnh trng ny
ko di, ngi chm phi dy dn pha khc, s phi chu in p dy rt nguy
him. Mt khc, cn phi c dy trung tnh s dng c in p pha.
36. Ti sao trong h thng in p t trung p tr ln ngi ta ch truyn ti
3 dy pha ( khng c dy trung tnh ) ?
Xung quanh dy dn in s to ra mt in trng ln, in trng ny
s mc vng trn dy trung tnh xy ra hin tng cm ng in t v to ra
mt dng in trn dy trung tnh. Vi cp in p ny s lm tn tht in nng
ln .
Trn ng dy truyn ti s mt cn i gia cc pha rt nh, nn dng
trong dy trung tnh ( nu c ) s rt nh .
my pht in v trm bin p ngi ta thit k trung tnh c ni t c
th hiu rng t l dy trung tnh cho h thng truyn ti .
37. Khi nim v sn xut in nng, truyn ti v phn phi ?
Sn xut in nng l qu trnh chuyn ho t nng lng s cp ( gm
nhit, sc nc, gi, nng lng nguyn t ) thnh in nng.
-
38
Truyn ti in l truyn nng lng in t cc nh my in n h
thng phn phi thng qua ng dy truyn ti in v trm bin p , vi in
p cao 500kV, 220kV, 110kV.
H thng phn phi l cung cp trc tip in nng n h tiu th vi
in p : 35kV,22kV,10kV, 6kV ( min Bc )
( V mt s t nh my qua h thng truyn ti n h tiu th ).
38. Tn tht cng sut , tn tht in nng, ngha ? Tn tht in nng kinh
doanh, tn tht in nng k thut l g ? cc bin php khc phc ?
vn chuyn in nng n cc h tiu th ta phi dng h thng ng
dy v cc trm bin p. Khi c dng in chy qua dy dn v cc thit b ca
trm bin p v chng c tng tr ( in tr, in khng ) nn bao gi cng c
tn tht nht nh v cng sut tc dng P v cng sut phn khng Q.
Mt khi xy ra tn tht cng sut th ng ngha vi vic tn tht in
nng. S nng lng mt mt A bin thnh nhit lm nng dy dn v my
bin p, cui cng to ra ngoi khng kh, khng c mt tc dng g .
Lng in b tn tht, mt i do cc nh my in cung cp. Kt qu
vn u t cao, tn thm nhin liu .
Tn tht in nng bao gm : Tn tht in nng k thut v tn tht in
nng kinh doanh .
Tn tht in nng k thut l tn tht in nng do thit b mang in
gy ra khi c dng in chy qua in tr thun ca thit b .
V d : Tn tht trong my bin p : tn tht ng, tn tht st .
Tn tht trn ng dy : do in tr dy dn , in tr mi ni .
Tn tht in nng kinh doanh l tn tht in nng do qun l v kinh
doanh in nng.
V d : Tn tht do sai s ca ng h o in nng .
Tn tht do n cp in .
Tn tht do sai st ca nhn vin ghi in
39. Cch tnh tn tht in nng trong my bin p, trong mt ng dy cp
cho ph ti ?
-
39
1. Tn tht cng sut trong my bin p:
S2
P = P0 + Pb = P0 + Pn (------ )2
Sdd
I0%Sdd Uo%S22
Q = Q0 + Qb = --------- + ----------
100 100Sdd
2. Tn tht in p trn ng dy :
P12.R + Q12.X
U = Ud = -------------------
U2
Trong :
P12 : Cng sut tc dung truyn t 1 n 2
Q12 : Cng sut phn khng truyn t 1 n 2
R : in tr tng ng ca on dy dn.
X : in khng tng ng ca on dy dn.
3. Tn tht in nng trong my bin p :
Spt
An = P0 .t + Pn . ( ------------- ) 2 .
Sm
40.Tn tht in p l g ? Cch tnh tn tht in p ?
Tn tht in p l s st p trn ng dy. Khi dng in chy trn dy
dn v c in p ri trn R, X nn in p tng im khc nhau dc theo dy
dn khng ging nhau v c xu hng cng xa ngun tn tht in p cng ln .
Cch tnh tn tht in p cn c vo :
-
40
- Dng in ph ti ( trng hp ng dy c mt ph ti , ng dy c nhiu
ph ti t cch xa nhau ).
- Cng sut ph ti ( ( trng hp ng dy c mt ph ti , ng dy c
nhiu ph ti t cch xa nhau )
C th tnh ton c th tham kho cc ti liu cc trng k thut ca
cc tc gi : Bi Ngc Th, Nguyn Vn m .
Tn tht in p l hiu s in p gia im u v im cui m ta
mun xc nh tn tht ca mng in c cng cp in p.
41. Tnh tn tht in p trong my bin p v trn ng dy truyn ti in
? Quy nh v thay i in p trong h thng in ?
( c trong phn vn hnh HT )
42. Tai sao phi nng cao in p truyn ti in nng i xa ?
Khong cch ti in cng xa, cng sut truyn ti cng ln th phi nng
in p truyn ti ln cao.
Ta c cng thc tnh tn tht in nng truyn ti :
A = R.I2.t
Trong : - R l in tr ca dy dn truyn ti .
- I l dng in trn dy truyn ti.
- t l thi gian truyn ti in .
Mun gim tn tht in nng ta phi gim R v I.
Gim R tc l tng tit din dy dn hoc phi s dng vt liu c in
tr rt nh t c li v mt kinh t .
Trong khi tn tht in nng A t l vi bnh phng dng in
truyn ti .
Vi cng cng sut truyn ti, in p truyn ti cng cao th dng in
truyn ti cng nh . ( S = U.I )
V vy vic la chn phng n nng in p ln cao gim tn tht
in nng c x dng hin nay.
Tuy vy vic la chn tr s in p cao tr s bao nhiu cn tu thuc
vo cc yu t sau :
- Tnh ton kinh t k thut gia vn u t v hiu qu gim tn tht in nng.
-
41
- Chiu di ng dy truyn ti .
- Cng sut truyn ti .
- Cp in p tiu chun ca thit b in trn th gii , khng nn chn cp in
p m hin nay ngi ta khng s dng na.
43. Phn bit mt s khi nim : Khng in, khng ti, ti nh mc, non ti,
y ti v qu ti ?
Khng in: khng c in p v khng c dng in ( U=0, I=0)
Khng ti : khng c dng in ch c in p ( I=0, U= Umax )
Ti nh mc : L dng in lm vic ch lu di lin tc, c vy
thit b in mi m bo vn hnh ng tui th theo thit k It=Idm
Khng ti : It = 0
Non ti : It < Idm
Qu ti : It > Idm
44. Chnh lu dng in xoay chiu l gi? V v gii thch mch chnh lu
dng in xoay chiu ?
Chnh lu l phng php to ra dng in mt chiu t dng in xoay
chiu bng cch chnh lu dng in xoay chiu .
Hot ng : Trong na chu k u A l cc dng, B l cc m, dng
in truyn t A ti M qua D1 ti N qua R ti P qua D3 ti Q ri v B.
Trong na chu k sau: B l cc dng, A l cc m, dng in truyn t
B ti Q qua D2 ti N, qu ti P, qua D4 ti M ri v A.
Dng in qua R l dng in 1 chiu vn cn nhp nhy, ngi ta dng
mch lc ( t in C hoc L, C ) gim bt s nhp nhy .
Ta c hnh v sau :
-
42
45. Th no l in p bc, in p tip xc, cch di chuyn ra khi vng c
in p bc? V hnh minh ha ?
a. in p bc :
Xy ra khi dy dn in b t ri xung t, s cch in, v bc cch
in ca dy dn b nt, v, h hng, in truyn t vt dn in ra ct, ra v
my v xung t.
Khi xy ra chm t, ti im chm t in p bng in p vt mang in
(in p chm).
Dng in chm t tn u vo trong t v cc pha theo hnh bn cu. Theo
chiu dng in tn vo t, ti mi im xc nh c gi tr in th theo
cng thc =I x R. Cng ra xa im chm t, mt dng in gim dn
v in th cng gim i, n khong 15 - 20m th in th = 0.
Trong phm vi khu vc b chm t, nu c ngi i li trong , ng vi mi
bc chn (t 0,5 - 0,8m) c mt hiu in th l Ub = a - b. (Ub l in p
bc) t vo c th. Di tc dng ca in p bc s c dng in i qua c
th ngi (t chn n sang chn kia) lm cho ngi b in git. Cng gn
im chm t in p bc cng ln, cng nguy him; cng xa im chm
t in p bc cng nh dn n = 0.
-
43
,U
a
Ub
b
R
l 20m 20m
Hnh1:Phn b in th trn t v in p bc(Ub).
Nhng ng-i dng in nh c, khi -a in xung n-c nh c,
hin t-ng v tai nn xy ra t-ng t nh- hin t-ng in chm t nu trn;
b. in p tip xc .
Khi ngi chm vo vt mang in s c in p tip xc Utx t vo c
th. Di tc dng ca Utx s sinh ra dng in Ing chy qua.
T thc nghim v qua phn tch tai nn in, ngi ta xc nh c
rng vi loi dng in khc nhau v gi tr ca chng khc nhau gy ra nhng
phn ng khc nhau trn c th ngi.
Bng 2
Dng in
(mA)
Dng in xoay chiu
(50-60 Hz)
Dng in mt chiu
0,6 - 1,5 Ngn tay b run nh, cm gic t. Khng c cm gic.
2 - 3 Cm gic t, ngn tay run mnh. Khng c cm gic.
5 - 7 C bp b co git, bn tay rung. Cm gic au, tay t v nng
8 - 10 Bn tay, ngn tay au, t, co c
nhng vn c th t bt tay ra khi
vt mang in
Cm gic b t nng tng ln
mnh
20 - 25 Cm thy au v kh th,tay co
khng th bt ra khi vt c in
C tay bt u b co, cm gic
nng tng ln.
50 - 80 Nght th, tim p mnh, ko di
qu 5 giy c th b t lit tim
Co git c bp, tay co qup,
kh th.
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44
90 - 100 H hp b t lit, ko di qu 3 giy
tim s ngng p
H hp b t lit, ko di s lit
tim.
Dng in qua ngi gy ra nhng hin tng: Lm co tht c bp, t lit
thn kinh, gy bng, phn hu mu, hu hoi c quan ni tng; dng in ln
s lm cho tim ngng p v tt th.
1. Cc yu t gy nguy him cho ngi khi b in git:
a) Loi v gi tri ca dng in i qua c th ngi (Ing):
Qua thc nghim v nhng phn tch nu trn ta xc nh c rng
cng dng in nguy him i vi c th ngi l:
in mt chiu: Ing nguy him = 100 mA ( 0,1 A ).
in xoay chiu: Ing nguy him = 50 mA ( 0,05 A ).
Vi nhng gi tr nu trn nguy c gy t vong cho ngi l rt ln.
Dng in c coi l an ton cho ngi ly tr s bng 1/2 Ing nguy
him
in 1 chiu: I at = 50 mA (0,05 A).
in xoay chiu: I at = 25 mA ( 0,025 A).
b) Thi gian dng in i qua ngi cng lu cng nguy him. Vi gi
tr dng in 0,1 A qua ngi trong thi gian 2 giy c th gy cht ngi.
Dng in nh nhng thi gian di vn rt nguy him.
c) Tn s ca dng in qua ngi nguy him khong t 25 n 100
Hz.
Tn s cng nghip (50 - 60 Hz) rt nguy him. Tn s cao t nguy him hn v
lc dng in ch i ngoi da, c th gy bng b mt da. Tn s 1000 Hz
tr ln t nguy him hn.
d) ng i ca dng in qua c th ngi nguy him nht l khi dng
in i qua tim v no. Xem bng thng k di y:
Bng 3
-
45
ng i ca dng in qua ngi T l dng in i qua tim
T tay qua tay 3,3
T tay phi qua chn 3,7
T tay tri qua chn 6,7
T chn qua chn 0,4
T u qua chn 6,8
T u qua tay 7,0
Cc trng hp thng hay xy ra l tip xc bng tay vo vt mang in, trong
trng hp nguy him nht l t tay tri qua chn.
2. Cc yu t lm thay i ln ca dng in qua ngi:
Ta c cng thc nh lut m tnh dng in i qua ngi:
Utx
Ing =
Rng
Rng Utx Trong Utx l in p tip xc;
Rng l in tr ca c th ngi.
Hnh 2: Tip xc trc tip vo vt mang in,
Nu Rng khng thay i, khi Utx cng ln th Ing cng ln;
Nu Utx khng thay i, Rng cng nh th Ing cng ln;
a) in tr ngi c tr s t 600, 700 n 100.000 . Trong k thut an
ton ngi ta ly tr s trung bnh Rng = 1000 .
in tr ngi ph thuc nhiu yu t: Tnh trng b mt ca da kh hay
m t, dy ca lp sng ( lp trai trn mt da), tnh trng c th, tui tc,
sc kho... Da b tn thng, in tr gim rt nhiu; ngi ung ru cng lm
in tr gim.
Khi ngi lm vic trong mi trng nng, m, c nhiu bi, ho cht
cng lm cho in tr ngi gim nhiu.
-
46
Khi ngi tip xc vi vt mang in, c dng in qua ngi, in tr
ngi s gim i nhanh chng do dng in t chy lp sng cch in trn
b mt ca da v lm cho kh nng dn in ca c th tng ln.
b) in p Utx t vo ngi ph thuc vo ngun in, tnh trng tip
xc vi vt mang in, gia ngi vi t v cc vt dn in xung quanh..
T cng thc trn ta c th xc nh gii hn in p tip xc nguy him
cho ngi: Utx = Ing x Rng
in 1 chiu: Uat = 0,05 x 1000 = 50 V
in xoay chiu: Uat = 0,025 x 1000 = 25 V
Utx thc t cao hn gi tr trn y th nguy him, nh hn gi tr th t
nguy him.
Yu t c bn nht gy tai nn l dng in qua ngi, dng in cng
ln cng nguy him.
Khi tip xc vi vt mang in, mun m bo an ton, cn tm mi cch
lm cho dng in qua ngi gim cng nh cng tt.
Bin php l dng ngun in p thp; tng cng in tr cch in gia
ngi vi t v cc vt dn xung quanh bng cch i ng, eo gng, dng
thm, so cch in.
46. Cc khi nim chung ni t trong h thng in ?
Tc dng ca ni t l nhm tn cc dng in s c trong h thng in
vo t v gi cho in p cc phn t b s c thp . Dng in s c c th
hiu l : phng in cch in, r r in ra v thit b, phng in do st nh .
Khi c trang b ni t, dng in ngn mch do cch in ca thit b vi
v b h hng, dng in st s theo dy ni t xung cc in cc v chy
tn vo trong t. Khi thit b v ti cc im ca t ln cn s xut hin
in p phn b nh hnh v :
,U
-
47
a
Ub
b
R
l
20m 20m
Hnh1:Phn b in th trn t v in p bc(Ub).
T hnh v trn, c th thy cng xa b phn ni t in p cng gim v
c th xem in p c th hon ton bng khng im xa b phn ni t.(
thng thng l ngoi 20m ) . gc ca ng cong phn b in p ph
thuc vo in dn ca t.in dn ca t cng ln ( c ngha l in tr sut
ca t cng nh ) th ng cong cng thoi v im c in p bng khng
cng xa .
in tr sut ca t ph thuc vo c tnh ca n, vo nhit , m
v cht lng in phn cha trong t. in tr sut s c gi tr ln nht
vo ma ng khi t lnh v ma h khi t kh . Trc khi thit k ni t
phi o in tr sut ca t. Thng thng o in tr sut ca t vo ma t
m, cn vic tng in tr khi t b qu kh s c tnh bng h s hiu chnh.
in tr ni t ( hay gi in tr tn ) c xc nh l t s gia in
p ca b phn ni t so vi im c in p bng khng, vi tr s dng in
qua b phn ni t .
Gi tr ca in tr ni t ph thuc vo kt cu, quy m ca h thng
ni t v in tr sut ca t .
i vi in cc n, ti thi im c dng in tn trong t nu tay
ngi hoc b phn no ca c th ngi chm vo v ca thit b th in p
tip xc UTX l in p gia ch chm ca c th ngi vi chn ngi c
xc nh :
UTX = d -
Trong : d l in th ln nht ti im 0.
: l in th ti im trn mt t ch chn ngi ng.
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48
Khi c ngi i n gn im s c th xut hin in p bc gia hai
chn Ub :
Ub = 1 _ 2
Trong : 1 l in th ti im 1.
2 l in th ti im 2
tng tnh an ton , trnh UTX,, Ub cn kh ln ngi ta dng hai hay
nhiu in cc, b tr thch hp trong din tch t thit b . Thng thng l ni
t hnh vng xung quanh thit b.
Lu khi nhiu in cc u song song, gia chng s xut hin hin
tng mn chn hiu qu ni t khng cao v s khng kinh t .
47. Nu cc quy nh v ni t trong h thng in ?
Tu theo chc nng ngi ta chia ni t lm ba loi :
1. Ni t lm vic : Nhm m bo ch lm vic bnh thng cho h thng
in v thit b in nh : ni t trung tnh MBA, my pht, my b, ni t
dy trung tnh trong h thng pha - t , ni t cc my bin dng, my bin
in p ni t ny c thc hin tu theo ch lm vic ca h thng
in.
2. Ni t an ton hay ni t bo v : Ni t v my v cc kt cu kim loi
bn ngoi ca cc thit b nhm m bo an ton cho ngi vn hnh khi cch
in ca thit b b h hng , r r in . Ni t ny phi m bo trong mi ch
( bnh thng hay s c ) v cc thit b khng b c in hoc ch c mt
in p thp khng nh hng n tnh mng ca ngi khi tit xc vi n .
3. Ni t chng st : tn dng in st mt cch thun li v gi cho in
p ca cc b phn thu st khng qu cao trnh b phng in ngc t n
n thit b .
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49
PHN II : THIT B IN .
a. c quy .
1. Cu to ca c quy axit, c quy kim ?
c quy l thit b bin i nng lng in nng thnh ho nng ( khi
np in vo c quy ) v bin i ho nng thnh in nng ( khi cho c quy
phng in ). c quy cung cp in mt chiu cho ph ti .
1. Cu to ca c quy : Gm ba phn chnh :
* V bnh : thng lm bng thu tinh, nha, cht tng hp chu c
Act, kim .
* in cc :
+ in cc dng :
- Vi c quy Axit : lm bng PbO2 p cht trong khung hnh t ong lm
bng ch .
- Vi c quy Kim : lm bng Ni(OH)2 nn cht trong cc khung c
khoan nhiu l nh lm bng thp m kn .
+ in cc m :
- i vi c quy Axit lm bng Pb p nh trong khung in cc dng .
- i vi c quy Kim lm bng Fe(OH)2 nn nh trong khung in cc
dng .
* Dung dch in phn :
+ c quy Axit l dung dch H2SO4.
+ c quy Kim l dung dch KOH.
2. ng dng ca c quy trong trm bin p v u im ca n ?
* Trong trm bin p , c quy c dng lm ngun thao tc mt chiu ,
gi nhim v cung cp in cho cc thit b nh th nh : iu khin, tn hiu, r
le t ng ho, nh sng s c, cc c cu t dng quan trng
* u im :
- Tin cy v h thng c quy c lp vi li in trong trm .
- Kh nng cho php qu ti ngn hn rt ln .
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50
3. Cc thng s k thut ca c quy axt v c quy kim ?
c quy c cc thng s chnh sau :
- in p nh mc : Udm l in p cho php nh nht cc cc ca c quy
trong gi phng in u tin ch phng in 10 gi, vi c quy Axit l
2V v c quy Kim l 1,25V.
- Dng in phng Ip: tu thuc vo ch phng nhng khng c
vt qu 5 ln dng in phng trong 10 gi khi lm vic lu di (nh khi
phng trong 1 gi ). V khng qu 12 ln dng in phng 10 gi khi lm vic
ngn hn ( nh khi phng trong 5 giy ).
- Dung lng phng Qp : l nng lng c quy cung cp c khi phng
in ( y hiu l vi in p nh mc ), ph thuc vo dng in phng v
thi gian phng. Dung lng nh mc l dung lng ng vi ch phng
nht nh trong 10 gi.
Thng trn mt c quy nh ch to ghi cc thng s vi dng nh sau :
Udm _ Qp .
V d : 12V _ 100Ah ; 24V _ 150Ah
4. Phn loi c quy, so snh u khuyt im ca chng ?
Da theo cu to c hai loi chnh l c quy Axit v c quy Kim, u
im ca loi ny l nhc im ca loi kia nh sau :
* Vi c quy Axit c cc u im sau ( so vi c quy Kim ):
- in p phng ban u cao 2,1 - 2,2V ( so vi 1,2 - 1,3V ca c quy
Kim ).
- c tnh phng in phng hn.
- Hiu sut cao hn .
- Gii han thay i in p cho php phng ln ( 2,2 - 1,75V)
- Bi s cho php qu ti ngn hn ln .
- Gi r .
* i vi c quy Kim :
- Tui th di hn.
- Khng c v nguy him i vi mi trng .
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51
Ngoi ra hin nay cn phn loi c quy kh v c quy nc. c quy kh
hin ang s dng rng ri v qun l vn hnh n gin, d bo qun .
5. Vn hnh v s dng c quy ?
Khi vn hnh s dng ngun mt chiu cung cp bng h thng c quy
phi tun th cc quy nh sau :
1. Ac quy phi c trong phng mt, kh ro. c thng gi thng
xuyn trnh gn ngn la.
2. c quy phi c gi sch s mt ngoi v np, l thot kh trn cc
np khng c tc, cc thanh dn ni bnh v cc bnh phi sch s, c bi
Vaseline trnh Oxy ho.
3. Phi kim tra mc dung dch hng ngy ( c quy nc ), mc dung
dch phi cao hn vch " LOW" ca nh ch to trnh cc b Sulfat ho, nu
dung dch cn phi b xung.
4. Kim tra dng np ca my np v np y dn bnh.
5. Hng nm cn kim tra v sc sch cc cht xc tc ri xung y bnh
trnh ngn mch cc tm cc .
6. Cch np hnh thnh mt c quy mi ?
* Np hnh thnh c quy mi :
1. c quy mi sau khi rt dung dch Axit i t 3-6 gi mi bt u np
ln u.
2. Dng in np ln u thng ly bng 1/10 dng in phng lin tc
trong 10 gi ca c quy Axit vi thi gian np t 8 _ 60 gi ( tu theo nh ch
to quy nh ).
3. Trong qu trng np nhit ca cht dung dch s tng dn nhng phi
duy tr sao cho khng qu 400C, t trng dung dch s tng dn.
4. Giai on cui ca c quy np y khi :
- in th mi bnh ( hay mi hc ) t 2,4 _ 2,5V v t trng cht in dch l
1,25 150C.
- Cht in dch phi si tm mnh.
- Thi gian np khong 8 _ 60 gi tu theo nh ch to.
* Cc ch np ca c quy :
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52
- Ch np ban u thng : Inap = Iphng trong 10 gi v thi gian np
khong 8 _ 60 gi.
- Ch np thng : Inp = Iphng trong 10 gi v thi gian np t 12 _ 16
gi .
- Ch np nhanh : Dng trong ch np ban u gm :
+ Giai on 1 : Inp = 3/2 Iphng trong 10 gi cho n khi in th mi bnh( hay
mi hc ) l 2,4V
+ Giai on 2 : Inp = Iphng trong 10 gi cho ti khi dung dch si tm mnh .
Lu : Quy trnh phng np cho mi loi c quy phi tun theo quy nh ca
nh ch to c nu trong ti liu k thut .
7. Cc h hng c quy v cch sa cha ?
Cc h hng thng gp v cch sa cha :
H hng Sa cha
Bnh r, thng, vch ngn b nt Thay v bnh mi hoc hn li
Cc tm cc b chp mch do cht
r nhiu
Sc ra sch cc cht r, thay dung
dch mi
c quy t phng in do cch in
hng, c tp cht trong dung dch
hoc dung dch y ni tt np bnh
Thay th cch in, dung dch hoc
v sinh
Cc u cc, u ct b Oxy ho nh sch bng giy nhp ri bi
Vaselline vo.
Cc bn cc b Sulfat ho, cong,
phnh to.
Sa thay lc hoc thay Axit mi
8. My np l g ? nguyn l lm vic ca my np ?
My np l mt thit b dng bin i dng in xoay chiu u vo
thnh dng mt chiu u ra np in cho h thng c quy v cung cp
cho cc ph ti.
Nguyn l lm vic chung ca cc my np l dng mt my bin p cch
ly c tc dng phi hp gia in p ngun xoay chiu vi in p ra mt chiu
cung cp cho cc ph ti , ng thi c nhim v cch ly mch xoay chiu vi
mch mt chiu, u ra ca bin p ny c a qua b chnh lu na chu k,
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53
chnh lu cu, hay chnh lu 3 pha hai na chu k ( chnh lu cu ) bin
thnh dng in mt chiu a ra np cho h thng c quy .
Hnh v s khi.
Hnh v mch chnh lu cu 1 pha.
Hnh v chnh lu cu 3 pha.
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54
9. Quy trnh vn hnh h thng c quy ca trm anh , ch ang lm vic
( Theo ti liu h thng c quy v h thng mt chiu ti trm )
b. My bin p .
1. My bin p l g ? Phn loi my bin p ?
My bin p l thit b in t tnh lm vic theo nguyn l cm ng in t,
bin i mt h thng dng in xoay chiu in p ny thnh h thng dng
in xoay chiu in p khc vi tn s khng i .
Theo cng dng, my bin p c phn loi nh sau :
1. My bin p lc : Dng truyn ti v phn phi cng sut trong h
thng in.
2. My bin p chuyn dng : Dng cho l luyn kim, cho cc thit b
chnh lu, my bin p hn
3. My bin p t ngu : bin i in p trong mt phm v khng ln
lm dng m my cc ng c in xoay chiu
4. My bin p o lng : Dng gim in p v dng in ln a
vo cc ng h o .
5. My bin p th nghim : Dng th nghim cc in p cao.
Phn loi theo cu to :
+ My bin p 2 dy cun , my bin p 3 dy cun .
+ My bin p t ngu : Gia cun s v th cp khng nhng lin h vi nhau
v t m cn lin h vi nhau v in .
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55
2. Nguyn l lm vic ca my bin p ?
My bin p gm mch t v cc cun dy nh hnh v :
y l my bin p mt pha hai dy cun . Dy cun 1 c w1 vng dy v
day cun 2 c w2 vng dy c cun trn li thp . Khi t mt in p xoay
chiu u1 vo dy cun 1, trong s sinh ra t thng mc vng vi c hai dy
cun 1 v 2 cm ng tra cc sc in ng e1 v e2 . Dy cun 2 c s s sinh
ra dng in i2 a ra ti vi in p l u2 ( nu khng ti i2 = 0 ). Nh vy
nng lng ca dng in xoay chiu c truyn t dy cun 1 sang dy
cun 2.
Gi s in p xoay chiu t vo l mt hm s hnh sin, th t thng do
n sinh ra cng l hm s hnh sin .
= msin t .
Do theo nh lut cm ng in t, s cm ng tronmg cc dy cun
1 v 2 s l :
e1 = 2E1sin (t-/2 )
e2 = 2E2sin (t-/2 )
Trong :
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56
E1 = 4,44w1m
E2 = 4,44w2 m
L tr hiu dng ca cc s cm ng trong dy cun w1 v dy cun w2 . Sc
in ng cm ng ny chm pha vi t thng sinh ra n mt gc /2
Nu chia E1 cho E2 ta c t s bin i ca my bin p nh sau :
E1 w1
K = ------- = --------
E2 w2
Nu khng k in p ri trn dy cun coi U1 = E1 , U2 = E2 do k l t s
bin p gia cun dy w1 v cun dy w2 .
3. Cc t u dy ca my bin p 3 pha ?
T ni dy ca my bin p, c hnh thnh do s phi hp kiu u dy
s cp v kiu u dy th cp. N biu th gc lch pha gia s dy s cp v
s dy th cp ca my bin p. Gc lch pha ny ph thuc vo cc yu t
sau :
- Chiu cun dy .
- Cch k hiu cc u dy.
- Kiu u dy cun s cp v th cp .
Tu theo cc yu t trn ta c cc dng t u dy : Y/ (m) v Y/Y (n),
/ (n ) Vi :
m : ch cc s l 1,3,5,7,9,11
n : Ch s chn 2,4,6,8,10,12
K hiu A,B,C : ch cc u u ca cun dy s cp.
K hiu X,Y,Z : ch cc u cui ca cun dy s cp.
K hiu a, b, c : ch cc u u ca cun dy th cp
K hiu x, y, z : ch cc u cui ca cun dy th cp.
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57
4. Trnh by v tn tht in p v tn tht in nng trong my bin p ?.
Tn tht in p trn MBA ph thuc nhiu yu t .
P.Rn + Q.Xn
U% = ---------------- 100%
U2 m
Vi : - P,Q : Cng sut tc dng v phn khng do MBA truyn ti ( kW,KVAR
) b qua tn tht cng sut trong MBA .
- Rn , Xn : in tr v in khng ca MBA ( )
- Um : in p nh mc ca MBA , mun quy i tn tht in p v
cp in p no th ly Um cp in p .
Trong :
Pn.U2 m
Rn = ---------------- 103
S2 m
Un % . U2 m
Xn = ------------------- 103
Sm
Vi : Pn l tn tht ngn mch ca MBA ( KW )
Un % tr s tng i ca in p ngn mch ca MBA
Sm l dung lng nh mc ca MBA ( KVA )
Tn tht in nng ca MBA :
Tn tht in nng ca my bin p bao gm tn tht khng ti ( tn tht
st ) v tn tht c ti ( tn tht ng ) thng tnh trong thi gian mt nm .
Ta c :
Spt
An = P0 .t + Pn . ( ------------- ) 2 .
Sm
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58
Vi : : Thi gian chu tn tht cng sut ln nht ( gi ) c tnh bi hm s
ph thuc vo : f ( Tmax, costb ) . Trong thc t c th xc inh theo cng
thc sau : = ( 0,124 + Tln .10-4
) . 8760, gi . Trong :
Tln : Thi gian s dng ph ti ln nht .
t : Thi gian vn hnh thc t ca MBA ( gi ) nu vn hnh lin tc t
= 8760 gi .
P0 , Pn : Tn tht khng ti v ngn mch ca MBA trong l lch my (
KW )
Spt , Sm : Ph ti ton phn ( thng ly bng ph ti tnh ton ), dung
lng nh mc ca MBA ( KVA ).
5. ngha cc thng s k thut c bn ca my bin p ?
i vi MBA cn lu cc thng s k thut c ban sau y :
- Um : in p lm vic nh mc ca cc cun dy ca MBA.
+ U1m : in p lm vic nh mc ca cun s cp.
+ U2m : in p lm vic nh mc ca cun dy th cp .
- Im : Dng in nh mc ca cc cun dy MBA .
- fm : Tn s lm vic nh mc ca MBA .
- Sm : Cng sut nh mc ca MBA trong iu kin lm vic nh mc.
- Y/Y(m), / (m) hoc Y/ (n) : T u dy ca MBA.
- Un% : Tr s tng i ca tr s ngn mch ca MBA.
- Ikt ( hoc Pkt ) : dng in khng ti hoc tn tht khng ti ca MBA.
Ngoi ra, trn nhn my cn ghi mt s thng s khc nh : trng lng
tng cng , trng lng du, ch lm mt, s nc iu chnh di ti
6. B iu chnh di ti l g? Cng dng v nguyn l lm vic ?
B iu p di ti l mt c cu cho php chuyn i iu chnh in p
ra khi my ang vn hnh, trong mt phm v nht nh no ng vi mt gi
tr dng ti ti a no .
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59
Nguyn l lm vic : Da trn c cu chuyn mch trn vi kt cu ngoi
tip im chnh cn c tip im ph chu h quang, v in tr ni tt khi b
iu chnh ang v tr chuyn i gia hai v tr k nhau .
Thng b iu chnh ch ch to cho php iu chnh thay i in p
gia hai v tr k nhau b ( 1,5-3% Um )
Hnh v minh ho .
7. B iu chnh khng in l g ? Cng dng v nguyn l lm vic ?
B iu p khng in l mt c cu cho php chuyn i iu chnh in
p ra trong phm vi no khi my bin p khng mang in .
Nguyn l lm vic : Da trn c cu chuyn mch trn, hoc chuyn ni,
kt cu ch mang cc u tip im chnh. Thng b iu p khng in cho
php iu chnh thay i in p gia hai v tr k nhau kh ln .( 7-15%)
8. Cu to cc thit b chnh ca my bin p ?
Cc b phn chnh ca my bin p gm :
+ Mch t ( gng t ) : c ch to t cc tm tole silic dy 0,35mm c
sn ph ct cch in, c ghp li vi nhau lm nhim v dn truyn t thng
trong my bin p .
+Cun dy : c ch to bng dy ng hoc dy nhm c bc
cch in, c cun ng tm, cun in p cao thng c cun bn ngoi
cun dy mang in p thp, lm nhim v dn truyn dng in trong my bin
p.
+ V my : dng c nh mch t, cha ton b mch t; cun dy v
du cch in .
+ S xuyn : c nh v a cc u dy ra ngoi v my .
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60
+ Du cch in : va lm nhim v tng cng cch in phn mang
in vi phn khng mang in trong my, va lm nhim v truyn nhit gia
phn cun dy , mch t ra ngoi v my .
9. Cu to v nguyn l lm vic cc thit b ph ca bin p ? Vai tr ca n
trong my bin p ?
Cc thit b ph ca my bin p bao gm :
1. H thng lm mt my bin p : c lm bng cch ghp cc ng trn hoc
dt, ni vo thn my bin p bng cc mt bch ni ( c gi l cch tn nhit
). Nhim v lm tng tit din tip xc ca lng du cch in trong thn my
bin p vi khng kh tn nhanh nhit cho my bin p .
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61
2. Qut gi : c lp t trn cnh tn nhit, c b tr thi hoc ht hi nng
trong h thng cnh tn nhit v thi ra ngoi nhm tng kh nng tn nhit cho
my bin p .
3. Bm du tun hon : c b tr ht du nng trong thn my bin p,
bm qua h thng cnh tn nhit nng cao kh nng tn nhit ca my bin
p, khi nhit my bin p tng n gii hn no ( loi ny thng dng
cho cc my bin p cng sut ln ).
4. B i nc my bin p :
+ B i nc khng ti : dng iu chnh in p ra trong phm vi no
khi my bin p c ct in .
+ B i nc di ti : dng iu chnh in p ra trong phm v no
khi my bin p vn ang mang in vi gi tr dng ti no .
5. B phn phng n : l mt mt bch c bt kn bng mt ming nhm hay
php mng, gii thot nhanh p sut sinh ra trong my bin p khi c s c
xy ra bn trong my bin p . Hin nay ngi ta thay knh phng n bng mt
van p lc . Khi s c bn trong my bin p, p sut trong my bin p tng
cao n mt gi tr no c chnh sn , van p lc s tc ng lm gim
nhanh p sut trong my v du c pht ra ngoi qua van p lc.
6. Rle gaz : l mt bu cha c mt knh, c ni tip trong h thng ng t
bnh du ph xung thn my chnh, bn trong t hai b phao hai cao
khc nhau. Trn mi phao c gn mt tip im thu ngn hot ng theo s
ln xung ca phao. Khi c hin tng sinh kh nhiu trong my bin p, hoc
mc du trong thng du ph gim ht do r r hoc cn du, rle gaz s hot
ng. Ban u lm h phao trn s tc ng ng tip im i bo tn hiu gaz
nh , nng hn phao di s hot ng ng tip im i ct my ct tch my
bin p ra khi li .
7. H thng th , gin n theo nhit ca du trong my bin p : gm mt
bnh du ph chnh ni xung thn my bin p v cc b phn cch ly gin tip
( loi thng du ph c ba ngn hc c thng ni ) hay cch ly trc tip ( thng
du ph c mng ni ) vi khng kh bn ngoi. Khi my bin p lm vic ng
vi nhit du no , lng du trong thn my chnh gin n ( hoc co li )
ra s c dn ln ( hoc h thp ) trong bnh du ph, nh b phn cch ly nn
du v cun dy my bin p khng b nhim m t mi trng bn ngoi .
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62
8. B lc xi phng nhit : l mt bnh rng c cha cht lc sch du thng l
ht silicagen to , ( c gi li trong bnh bng cc tm li ) , nh i lu
nhit, du trong thn my bin p trong qu trnh lm vic s c dn tun
hon qua b lc v s c b lc gi li cc cht bn ( sinh ra trong qu trnh
my bin o lm vic ).
10. Cng dng du trong my bin p ?
Du trong my bin p l loi du cch in, n c tc dng sau :
- C nhim v cch in cc b phn mang in v phn khng mang in bn
trong my bin p .
- Tn nhit cho cun dy v mch t ra mi trng bn ngoi .
11. H thng lm mt my bin p, cng dng, phn loi ?
H thng lm mt my bin p c nhim v gii nhit nhanh cho phn
mch t v cun dy my bin p, khng ch nhit ca my bin p trnh
ph hu cch in trong thn my bin p .
Phn loi :
+ Lm mt my bin p bng du t nhin : nh c s i lu bng du bn
trong my v khng kh bn ngoi v my. V my c th trn, c gn hoc
cnh tn nhit , thng ch dng cho my bin p c cng sut b .
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+ Lm mt my bin p bng du t nhin c qut gi : trn cc b cnh tn
nhit ca my bin p, c t cc h thng qut gi tng cng tn nhit
trn b mt lm mt.
+ Lm mt my bin p bng tun hon cng bc du v khng kh : My bin
p c t thm cc bm du bm tun hon lun chuyn du gia thn my
v cc cnh tn nhit c qut gi .
Ngoi ra cn c loi lm mt my bin p bng du v nc, nhng t s
dng .
12. Cc h hng ca my bin p v cch x l ?
Hin tng v cch pht
hin h hng
Nguyn nhn Bin php sa cha
1/ Mch t:
- Tn tht khng ti tng,
chp chy v in p
nh thng ca du gim,
axit trong du tng.
- Pht sinh kh mu sm
trong rle gaz, chy c,
chp chy ca du
gim.
- C ting ku to bt
thng.
- C ting lch cch bn
trong my khi in p
tng.
- Cch in cc l thp gi
ci, h hng cc b.
- Li thp b ngn mch
cc b hoc b chy.
- Cc chi tit p mcht
gng yu, lng ra, p
khng cht ch ni hoc
in p s cp cao qu
nh mc.
- t dy ni t .
- a my v xng i tu
li.
- a my v xng i
tu.
- Kim tra xit li hoc
kim tra gim bt in p
s cp .
- Kim tra ni li.
2/ Cun dy :
- Pht nng mnh, dng
in s cp tng khng
ln, rle gaz tc ng ct
my ngt ; kh trong rle
- B chp vng dy do h
hng cch in; cun dy
b h khi du do mc du
gim thp.
- Qun li cun dy.
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gaz hng c mu trng
sm , chy c.
- Rle gaz cng vi rle
qu dng hoc so lch lm
vic; du tro ra ng
phng n.
- Ngn mch gia cc pha
hoc ra v do cch in
hoc du b m.
- Qun li cun dy .
3/ S :
- Rle qu dng v so lch
lm vic cng vi cc s
b phng in hoc nh
thng ra v.
- Do vt l ri vo s, s
b nt hoc du s b gim
qu thp.
- Thay s mi.
4/ Du :
- Mc du thp, rle hi
bo tn hiu.
- Rle gaz bo tn hiu,
mc du bnh thng, kh
hng c trong rle gaz
khng mu, khng mi,
khng chy.
- Du i mu sm
hoc en hoc c cht ln
cn , cch in gim nhiu
- R r du nhiu lm ht
du trong bnh du ph.
- Du c ln khng kh do
qu trnh np du kh kh
khng tt.
- Do MBA thng xuyn
b qu nhit hoc vavhs
ngn b i nc di ti b
r, b thng vi thn
my, hoc do h thng th
ca MBA khng cn m
bo khin MBA th trc
tip ra khng kh bn
ngoi .
- B sung thm du theo
c tnh ca nh ch to
- Rt chn khng MBA
kh kh trit trong my.
- i tu my bin p, sa
cha cc phn h hng v
thay du mi.
c. My ct in .
1. My ct in l g ?
My ct in l thit b in dng ng ct mch in mi ch
vn hnh: ch khng ti, ch ti nh mc, ch s c, trong ch
ng ct dng ngn mch l ch nng n nht.
2. Phn loi my ct in, u khuyt im ca tng loi ?
Da vo cu tao ca MC ngi ta chia thnh cc loi MC sau:
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1. MC nhiu du: Du lm nhim v cch in v dp h quang
u im: Nguyn l cu to n gin, d ch to v r tin.
Nhc im: - Thi gian ct ln c 0,15 0,2s
- Kch thc v khi lng ln
- Bo dng v sa cha phc tp, du cn lm sch sau mt
s ln ct dng in ln nht nh (nh), d gy chy n, ngy nay MC du t
c ch to.
2. MC t du: Du ch lm nhim v dp h quang.
u im: Nguyn l cu to n gin, d ch to v r tin.
- V kch thc v khi lng, thi gian ng ct nh hn MC
du.
Nhc im:
- Cng sut ct ngn mch nh hn MC du. Mt khc v t du
nn du mau b bn, cht lng du gim nhanh. Do khng c
thit b hm nng du nn khng th t ni c nhit thp.
Hin nay s lng MC ny ang t dn do khng cnh tranh
c vi cc MC tin tin khc.
3. MC khng kh nn: Khng kh c nn li p sut cao thi h quang.
u im: Kh nng ct ln c th t ti 100kA, thi gian ct b nn tip
im c tui th cao. Loi MC ny khng d chy n nh MC du.
Nhc im: Loi MC ny c thit b nn kh i km nn thng ch s
dng ti cc trm c s lng MC ln.
4. MC kh SF6 : Kh SF6 trong my ngt lm nhim v cch in v dp h
quang .
u im: - kh SF6 c bn in cao
- H s dn nhit ca kh SF6 cao gp 4 ln khng kh v vy c th tng
mt dng in trong mch dn in ca MC, gim khi lng ng.
- Kh nng dp h quang ca bung dp kiu thi dc kh SF6 cao gp 6
ln MC khng kh v vy gim c thi gian chy ca h quang tng tui th
ca tip im.
- Kh SF6 l loi kh tr, kh chy, khng mi, khng c hi nn kh b
thay i tnh cht.
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- c ch to mi cp in p t 3kV 800kV, kh nng ct ln, kch
thc nh gn, an ton v tin cy cao, tui th cao v chi ph bo dng
thp.
Nhc im:
- Kh SF6 c nhit ho lng thp v vy loi kh ny ch dung p
sut khng cao trnh phi dng thit b hm nng. Mt khc kh ch c th
m bo cht lng khi khng c tp cht.
5. MC chn khng:
My ngt chn khng l h quang c dp tt trong mi trng chn
khng .
u im: Kch thc nh gn, khng gy ra chy n, tui th cao khi
ng ct dng in nh mc, gn nh khng cn bo dng nh k, thi gian
ng ct nh. Dng rng ri li in trung p vi dng nh mc ti 5000A.
Nhc im: Gi thnh cao
3. Cu to v nguyn l lm vic ca my ct in dp h quang bng kh
SF6 ?
My ngt SF6 l dng kh SF6 dp h quang v cch in.
Cu to:
Trong MC SF6 h quang s nhanh chng dp tt nu c thi h quang, trn c
s c hai bin php thi c p dng l: Thi t v t thi kiu kh nn (
dng pittng, xi lanh) trong nguyn l t thi dng pittng xi lanh c
dng rng ri hn v hiu qu hn. Vi MC kiu pittng t thi ch i hi
khong 20% nng lng ca b truyn ng khi c cng tnh nng k thut do
ch cn b truyn ng nh gn, lm vic chc chn, n v tin cy cao.
Hnh 1: S nguyn l lm vic ca MC SF6 kiu t thi
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Qu trnh ct din ra nh sau: Khi c tn hiu ct, trc truyn ng 4 quay
ko theo h thng ng ca bung ct (gm tip im ng h quang 2, tip
im ng lm vic xilanh 6, ming thi cch in 9 ) chuyn ng tnh tin
xung di, ng thi kh SF6 c nn trong xilanh 6, h tip im lm vic
ct trc ri n h tip im h quang. Sau khi h quang pht sinh, ming thi
9 c gii phng khi tip im h quang 8, kh nn SF6 c thot ra thi tt
h quang. Thng mi bnh ct, c ng h ch p sut SF6 v c van np kh
b sung.
4. . Cu to v nguyn l lm vic ca my ct in dp h quang bng du
cch in ?
Cu to, nguyn l hat ng:
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Thng cha du 1, thng cha du MBA 2, y c 75 n 80% th
tch my. Thng lm bng thp, c lp lt cch in 9 bn trong ngn h
quang khng lan ra v thng. Hai s xuyn 4 t nghing tng khong cch
cch in trong khng kh. Vi in p di 15kV s xuyn c cu to n
gin, s 35kV trong lng s c thm cch in baklit, s 110kV c cu to
kiu in dung in p phn b u. Phn tip im 7 ca MC c gn trn