CH¦¥NG vi: Kü thuËt an toµn vÒ ®iÖn
1 nguyªn nh©n vµ t¸c h¹i cña tai n¹n ®iÖn
I.T¸c dông cña dßng ®iÖn ®èi víi c¬ thÓ con ng−êi:
-Khi ng−êi tiÕp xóc víi ®iÖn sÏ cã 1 dßng ®iÖn ch¹y qua ng−êi vµ con ng−êi sÏ chÞu t¸c dông
cña dßng ®iÖn ®ã.
-T¸c h¹i cña dßng ®iÖn ®èi víi c¬ thÓ con ng−êi cã nhiÒu d¹ng: g©y báng, ph¸ vì c¸c m«, lµm
g·y x−¬ng, g©y tæn th−¬ng m¾t, ph¸ huû m¸u, lµm liÖt hÖ thèng thÇn kinh,...
-Tai n¹n ®iÖn giËt cã thÓ ph©n thµnh 2 møc lµ chÊn th−¬ng ®iÖn (tæn th−¬ng bªn ngoµi c¸c
m«) vµ sèc ®iÖn (tæn th−¬ng néi t¹i c¬ thÓ).
1.ChÊn th−¬ng ®iÖn:
-Lµ c¸c tæn th−¬ng côc bé ë ngoµi c¬ thÓ d−íi d¹ng: báng, dÊu vÕt ®iÖn, kim lo¹i ho¸ da.
ChÊn th−¬ng ®iÖn chØ cã thÓ g©y ra 1 dßng ®iÖn m¹nh vµ th−êng ®Ó l¹i dÊu vÕt bªn ngoµi.
a/Báng ®iÖn:
-Do c¸c tia hå quang ®iÖn g©y ra khi bÞ ®o·n m¹ch, nh×n bÒ ngoµi kh«ng kh¸c g× c¸c lo¹i
báng th«ng th−êng. Nã g©y chÕt ng−êi khi qu¸ 2/3 diÖn tÝch da cña c¬ thÓ bÞ báng. Nguy
hiÓm h¬n c¶ lµ báng néi t¹ng c¬ thÓ dÉn ®Õn chÕt ng−êi mÆc dï phÝa ngoµi ch−a qu¸ 2/3.
b/DÊu vÕt ®iÖn:
-Lµ 1 d¹ng t¸c h¹i riªng biÖt trªn da ng−êi do da bÞ Ðp chÆt víi phÇn kim lo¹i dÉn ®iÖn ®ång
thêi d−íi t¸c dông cña nhiÖt ®é cao (kho¶ng 120oC).
c/Kim lo¹i ho¸ da:
-Lµ sù x©m nhËp cña c¸c m·nh kim lo¹i rÊt nhá vµo da do t¸c ®éng cña c¸c tia hå quang cã
b·o hoµ h¬i kim lo¹i (khi lµm c¸c c«ng viÖc vÒ hµn ®iÖn).
2.Sèc ®iÖn:
-Lµ d¹ng tai n¹n nguy hiÓm nhÊt. Nã ph¸ huû c¸c qu¸ tr×nh sinh lý trong c¬ thÓ con ng−êi vµ
t¸c h¹i tíi toµn th©n. Lµ sù ph¸ huû c¸c qu¸ tr×nh ®iÖn vèn cã cña vËt chÊt sèng, c¸c qu¸ tr×nh
nµy g¾n liÒn víi kh¶ n¨ng sèng cña tÕ bµo.
-Khi bÞ sèc ®iÖn c¬ thÓ ë tr¹ng th¸i co giËt, mª man bÊt tØnh, tim phæi tª liÖt. NÕu trong vßng
4-6s, ng−êi bÞ n¹n kh«ng ®−îc t¸ch khái kÞp thêi dßng ®iÖn co thÓ dÉn ®Õn chÕt ng−êi.
-Víi dßng ®iÖn rÊt nhá tõ 25-100mA ch¹y qua c¬ thÓ còng ®ñ g©y sèc ®iÖn. BÞ sèc ®iÖn nhÑ
cã thÓ g©y ra kinh hoµng, ngãn tay tª ®au vµ co l¹i; cßn nÆng cã thÓ lµm chÕt ng−êi v× tª liÖt
h« hÊp vµ tuÇn hoµn.
-Mét ®Æc ®iÓm khi bÞ sèc ®iÖn lµ kh«ng thÊy râ chç dßng ®iÖn vµo ng−êi vµ ng−êi tai n¹n
kh«ng cã th−¬ng tÝch.
II.C¸c nh©n tè ¶nh h−ëng tíi møc ®é trÇm träng khi bÞ ®iÖn giËt:
1.C−êng ®é dßng ®iÖn ®i qua c¬ thÓ:
-Lµ nh©n tè chÝnh ¶nh h−ëng tíi ®iÖn giËt. TrÞ sè dßng ®iÖn qua ng−êi phô thuéc vµo ®iÖn ¸p
®Æt vµo ng−êi vµ ®iÖn trë cña ng−êi, ®−îc tÝnh theo c«ng thøc:
U
Rng
Trong ®ã:![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image001.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image002.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image003.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image004.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image006.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image008.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image010.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image011.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) 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§iÖn trë cña da ng−êi gi¶m kh«ng tØ lÖ víi sù t¨ng ®iÖn ¸p. Khi ®iÖn ¸p lµ 36V
th× sù huû ho¹i líp da x¶y ra chËm, cßn khi ®iÖn ¸p lµ 380V th× sù huû ho¹i da
x¶y ra ®ét ngét.
Khi líp da kh« vµ s¹ch, líp sõng kh«ng bÞ ph¸ ho¹i, ®iÖn trë vµo kho¶ng 8.104-
40.104Ω/cm2; khi da −ít cã må h«i th× gi¶m xuèng cßn 1000Ω/cm2 vµ Ýt h¬n.
· §iÖn trë c¸c tæ chøc bªn trong cña c¬ thÓ phô thuéc vµo trÞ sè ®iÖn ¸p, lÊy trung b×nh
vµo kho¶ng 1000Ω. §¹i l−îng nµy ®−îc sö dông khi ph©n tÝch c¸c tr−êng hîp tai n¹n
®iÖn ®Ó x¸c ®Þnh gÇn ®óng trÞ sè dßng ®iÖn ®i qua c¬ thÓ con ng−êi trong thêi gian tiÕp
xóc, tøc lµ trong tÝnh to¸n lÊy ®iÖn trë cña ng−êi lµ 1000Ω (kh«ng lÊy ®iÖn trë cña líp
da ngoµi ®Ó tÝnh to¸n).
6.§Æc ®iÓm riªng cña tõng ng−êi:
-Cïng ch¹m vµo 1 ®iÖn ¸p nh− nhau, ng−êi bÞ bÖnh tim, thÇn kinh, ng−êi søc khoÎ yÕu sÏ
nguy hiÓm h¬n v× hÖ thèng thÇn kinh chãng tª liÖt. Hä rÊt khã tù gi¶i phãng ra khái nguån
®iÖn.
7.M«i tr−êng xung quanh:
-M«i tr−êng xung quanh cã bôi dÉn ®iÖn, cã nhiÖt ®é cao vµ ®Æc biÖt lµ ®é Èm cao sÏ lµm ®iÖn
trë cña ng−êi vµ c¸c vËt c¸ch ®iÖn gi¶m xuèng, khi ®ã dßng ®iÖn ®i qua ng−êi sÏ t¨ng lªn.
III.Ph©n tÝch mét sè tr−êng hîp tiÕp xóc víi m¹ng ®iÖn:
-Khi ng−êi tiÕp xóc víi m¹ng ®iÖn, møc ®é nguy hiÓm phô thuéc vµo s¬ ®å nèi m¹ch gi÷a
ng−êi vµ m¹ng ®iÖn. Nãi chung cã thÓ ph©n ra 3 tr−êng hîp phæ biÕn sau ®©y:
1.Ch¹m ®ång thêi vµo hai pha kh¸c nhau cña m¹ng ®iÖn:
-Tr−êng hîp ch¹m vµo 2 pha bÊt kú trong m¹ng 3 pha hoÆc víi d©y trung hoµ vµ 1 trong c¸c
pha sÏ t¹o nªn m¹ch kÝn trong ®ã nèi tiÕp víi ®iÖn trë cña ng−êi, kh«ng cã ®iÖn trë phô thªm
nµo kh¸c.
- 66 -
qua ng−êi rÊt lín. Khi ®ã dï cã ®i giµy kh«, ñng c¸ch ®iÖn hay ®øng trªn ghÕ gç, th¶m c¸ch
®iÖn vÉn bÞ giËt m¹nh.
2.Ch¹m vµo mét pha cña dißng ®iÖn ba pha cã d©y trung tÝnh nèi ®Êt:
-§©y lµ tr−êng hîp m¹ng ®iÖn 3 pha cã ®iÖn ¸p ≤100V. Trong tr−êng hîp nµy, ®iÖn ¸p c¸c
d©y pha so víi ®Êt b»ng ®iÖn ¸p pha tøc lµ ng−êi ng−êi ®Æt trùc tiÕp d−íi ®iÖn ¸p pha Up. NÕu
bá qua ®iÖn trë nèi ®Êt Ro th× dßng ®iÖn qua ng−êi ®−îc tÝnh nh− sau:
I ng =
U p
Rng
=
U d
3.Rng
(6.3)
Trong ®ã:
+Up: ®iÖn ¸p pha (V).
3.Ch¹m vµo mét pha cña m¹ng ®iÖn víi d©y trung tÝnh c¸ch ®iÖn kh«ng nèi ®Êt:
-Ng−êi ch¹m vµo 1 pha coi nh− m¾c vµo m¹ng ®iÖn song song víi ®iÖn trë c¸ch ®iÖn cña pha
®ã vµ nèi tiÕp víi c¸c ®iÖn trë c¶u 2 pha kh¸c.
-TrÞ sè dßng ®iÖn qua ng−êi phô thuéc vµo ®iÖn ¸p pha, ®iÖn trë cña ng−êi vµ ®iÖn trë cña
c¸ch ®iÖn ®−îc tÝnh theo c«ng thøc:
I ng =
U d
3.Rng +
Rc
3
=
3 U d
3.Rng + Rc
(6.4)
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+Rc: ®iÖn trë cña c¸ch ®iÖn (Ω).
→Ta thÊy râ rµng dßng ®iÖn qua ng−êi trong tr−êng hîp nµy lµ nhá nhÊt v× thÕ Ýt nguy hiÓm
nhÊt.
IV.Nh÷ng nguyªn nh©n g©y ra tai n¹n ®iÖn:
-Tai n¹n ®iÖn cã thÓ chia lµm 3 h×nh thøc:
· Do tiÕp xóc trùc tiÕp víi d©y dÉn hoÆc bé phËn thiÕt bÞ cã dßng ®iÖn ®i qua.
· Do tiÕp xóc bé phËn kÕt cÊu kim lo¹i cña thiÕt bÞ ®iÖn hoÆc th©n cña m¸y cã chÊt c¸ch
®iÖn bÞ háng.
· Tai n¹n g©y ra do ®iÖn ¸p ë chç dßng ®iÖn rß trong ®Êt.
→Ngoµi ra, cßn1 h×nh thøc n÷a lµ do sù lµm viÖc sai lÇm cña ng−êi s÷a ch÷a nh− bÊt ngê
®ãng ®iÖn vµo thiÕt bÞ ë ®ã cã ng−êi ®ang lµm viÖc.
-Nh÷ng nguyªn nh©n lµm cho ng−êi bÞ tai n¹n ®iÖn:
· Sù h− háng cña thiÕt bÞ, d©y dÉn ®iÖn vµ c¸c thiÕt bÞ më m¸y.
· Sö dông kh«ng ®óng c¸c dông cô nèi ®iÖn thÕ trong c¸c phßng bÞ Èm −ít.
· ThiÕu c¸c thiÕt bÞ vµ cÇu ch× b¶o vÖ hoÆc cã nh−ng kh«ng ®¸p øng víi yªu cÇu.
· TiÕp xóc ph¶i c¸c vËt dÉn ®iÖn kh«ng cã tiÕp ®Êt, dÞch thÓ d·n ®iÖn, tay quay hoÆc c¸c
phÇn kh¸c cña thiÕt bÞ ®iÖn.
· Bè trÝ kh«ng ®Çy ®ñ c¸c vËt che ch¾n, rµo l−íi ng¨n ngõa viÖc tiÕp xóc bÊt ngê víi bé
phËn dÉn ®iÖn, d©y dÉn ®iÖn cña c¸c trang thiÕt bÞ.
· ThiÕu hoÆc sö dông kh«ng ®óng c¸c dông cô b¶o vÖ c¸ nh©n: ñng, g¨ng, tay c¸ch ®iÖn,
th¶m cao su, gi¸ c¸ch ®iÖn.
· ThiÕt bÞ ®iÖn sö dông kh«ng phï hîp víi ®iÒu kiÖn s¶n xuÊt.
§2 c¸c biÖn ph¸p chung an toµn vÒ ®iÖn
I.Sö dông ®iÖn thÕ an toµn:
-Tuú thuéc vµo møc ®é nguy hiÓm vÒ ®iÖn cña c¸c lo¹i phßng s¶n xuÊt mµ yªu cÇu an toµn vÒ
®iÖn cã møc ®é kh¸c nhau. Mét trong nh÷ng biÖn ph¸p ®ã lµ viÖc sö dông ®óng møc ®iÖn ¸p
®èi víi c¸c thiÕt bÞ ®iÖn. §iÖn ¸p an toµn lµ ®iÖn ¸p kh«ng g©y nguy hiÓm ®èi víi ng−êi khi
ch¹m ph¶i thiÕt bÞ mang ®iÖn.
1.Ph©n lo¹i c¸c n¬i lµm viÖc theo møc ®é nguy hiÓm vÒ ®iÖn:
-TÊt c¶ c¸c phßng s¶n xuÊt tuú theo møc ®é nguy hiÓm vÒ ®iÖn chia thµnh 3 nhãm:
a/C¸c phßng, c¸c n¬i Ýt nguy hiÓm:
-Lµ c¸c phßng kh« r¸o víi quy ®Þnh:
· §é Èm t−¬ng ®èi cña kh«ng khÝ kh«ng qu¸ 75%.
· NhiÖt ®é trong kho¶ng 5-25oC (kh«ng qu¸ 30oC).
· Sµn cã ®iÖn trë lín b»ng vËt liÖu kh«ng dÉn ®iÖn (gç kh« r¸o, r¶i nhùa).
· Kh«ng cã bôi dÉn ®iÖn.
· Con ng−êi kh«ng ph¶i ®ång thêi tiÕp xóc víi c¬ cÊu kim lo¹i cã nèi víi ®Êt vµ víi vá
kim lo¹i cña thiÕt bÞ ®iÖn.
b/C¸c phßng, c¸c n¬i nguy hiÓm nhiÒu:![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image001.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image002.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image003.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image004.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image006.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image008.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image010.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image011.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image013.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image014.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image015.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image016.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image018.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image020.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image021.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image022.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image024.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image025.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image026.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image027.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image028.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image029.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image030.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image031.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image032.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image033.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image034.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image035.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image036.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image037.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image038.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image039.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image040.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image041.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image042.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image043.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image044.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image045.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image046.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image047.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image048.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image049.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image050.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image051.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image052.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image053.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image055.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image056.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image057.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image058.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image059.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image060.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image061.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image062.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image063.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image064.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image065.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image066.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image067.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image068.gif)
- 68 -
-C¸c phßng Èm víi:
· §é Èm t−¬ng ®èi lu«n lu«n trªn 75%.
· §é Èm t−¬ng ®èi cã thÓ nhÊt thêi t¨ng ®Õn b·o hoµ.
· NhiÖt ®é trung b×nh tíi 25oC.
-C¸c phßng kh« kh«ng cã hÖ thèng lß s−ëi vµ cã tÇng m¸i.
-C¸c phßng cã bôi dÉn ®iÖn.
-C¸c phßng nãng víi nhiÖt ®é kh«ng khÝ lín h¬n 30oC, trong thêi gian dµi con ng−êi ph¶i tiÕp
xóc ®ång thêi víi vá kim lo¹i cña c¸c thiÕt bÞ ®iÖn vµ víi c¸c c¬ cÊu kim lo¹i c«ng tr×nh cña
d©y chuyÒn c«ng nghÖ cã nèi ®Êt.
-C¸c phßng cã sµn lµ vËt liÖu dÉn ®iÖn (b»ng kim lo¹i, ®Êt, bªt«ng, gç bÞ Èm, g¹ch,...)
c/C¸c phßng, c¸c n¬i ®Æc biÖt nguy hiÓm:
-RÊt Èm −ít trong ®ã ®é Èm t−¬ng ®èi cña kh«ng khÝ th−êng xÊp xÜ 100% (trÇn, t−êng, sµn vµ
c¸c ®å ®¹c trong phßng cã ®äng h¹t n−íc).
-Th−êng xuyªn cã h¬i khÝ ®éc.
-Cã Ýt nhÊt 2 trong nh÷ng dÊu hiÖu cña phßng hoÆc n¬i nguy hiÓm nhiÒu (môc B).
-Nguy hiÓm vÒ mÆt næ (kho chøa chÊt næ trªn c«ng tr−êng).
2.Mét sè quy ®Þnh an toµn:
-§èi víi c¸c phßng, c¸c n¬i kh«ng nguy hiÓm m¹ng ®iÖn dïng ®Ó th¾p s¸ng, dïng cho c¸c
dông cô cÇm tay,... ®−îc sö dông ®iÖn ¸p kh«ng qu¸ 220V. §èi víi c¸c n¬i nguy hiÓm nhiÒu
vµ ®Æc biÖt nguy hiÓm ®Ìn th¾p s¸ng t¹i chç cho phÐp sö dông ®iÖn ¸p kh«ng qu¸ 36V.
-§èi víi ®Ìn chiÕu cÇm tay vµ dông cô ®iÖn khÝ ho¸:
· Trong c¸c phßng ®Æc biÖt Èm, ®iÖn thÕ kh«ng cho phÐp qu¸ 12V.
· Trong c¸c phßng Èm kh«ng qu¸ 36V.
-Trong nh÷ng tr−êng hîp ®Æc biÖt nguy hiÓm cho ng−êi nh− khi lµm viÖc trong lß, trong
thïng b»ng kim lo¹i,...ë nh÷ng n¬i nguy hiÓm vµ ®Æc biÖt nguy hiÓm chØ ®−îc sö dông ®iÖn
¸p kh«ng qu¸ 12V.
-§èi víi c«ng t¸c hµn ®iÖn, ng−êi ta dïng ®iÖn thÕ kh«ng qu¸ 70V. Khi hµn hå quang ®iÖn
nhÊt thiÕt lµ ®iÖn thÕ kh«ng ®−îc cao qu¸ 12-24V.
II.Lµm bé phËn che ch¾n vµ c¸ch ®iÖn d©y dÉn:
1.Lµm bé phËn che ch¾n:
-§Ó b¶o vÖ dßng ®iÖn, ng−êi ta ®Æt nh÷ng bé phËn che ch¾n ë gÇn c¸c m¸y mãc vµ thiÕt bÞ
nguy hiÓm hoÆc t¸ch c¸c thiÕt bÞ ®ã ra víi kho¶ng c¸ch an toµn.
-C¸c lo¹i che ch¾n ®Æc, l−íi hay cã lç ®−îc dïng trong c¸c phßng kh« khi ®iÖn thÐ lín h¬n
65V, ë trong c¸c phßng Èm khi ®iÖn thÕ lín h¬n 36V vµ trong c¸c phßng ®Æc biÖt Èm ®iÖn thÕ
lín h¬n 12V.
-ë c¸c phßng s¶n xuÊt trong ®ã cã c¸c thiÕt bÞ lµm viÖc víi ®iÖn thÕ 1000V, ng−êi ta lµm
nh÷ng bé phËn che ch¾n ®Æc (kh«ng phô thuéc vµo chÊt c¸ch ®iÖn hay kh«ng) vµ chØ cã thÓ
lÊy che ch¾n ®ã ra khi ®· ng¾t dßng ®iÖn.
2.C¸ch ®iÖn d©y dÉn:
-D©y dÉn cã thÓ kh«ng lµm c¸ch ®iÖn nÕu d©y ®−îc treo cao trªn 3.5m so víi sµn; ë trªn c¸c
®−êng vËn chuyÓn «t«, cÇn trôc ®i qua d©y dÉn ph¶i treo cao 6m.![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image001.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image002.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image003.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image004.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image006.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image008.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image010.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image011.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image013.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image014.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image015.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image016.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image018.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image020.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image021.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image022.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image024.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image025.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image026.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image027.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image028.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image029.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image030.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image031.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image032.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image033.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image034.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image035.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image036.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image037.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image038.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image039.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image040.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image041.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image042.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image043.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image044.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image045.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image046.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image047.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image048.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image049.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image050.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image051.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image052.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image053.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image055.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image056.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image057.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image058.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image059.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image060.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image061.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image062.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image063.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image064.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image065.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image066.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image067.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image068.gif)
- 69 -
-NÕu khi lµm viÖc cã thÓ ®ông ch¹m vµo d©y dÉn th× d©y dÉn ph¶i cã cao su bao bäc, kh«ng
®−îc dïng d©y trÇn.
-D©y c¸p ®iÖn cao thÕ qua chç ng−êi qua l¹i ph¶i cã l−íi gi¨ng trªn kh«ng phßng khi d©y bÞ
®øt.
-Ph¶i rµo quanh khu vùc ®Æt m¸y ph¸t ®iÖn hoÆc m¸y biÕn thÕ.
III.Lµm tiÕp ®Êt b¶o vÖ:
-C¸c bé phËn cña vá m¸y, thiÕt bÞ b×nh th−êng kh«ng cã ®iÖn nh−ng nÕu c¸ch ®iÖn háng, bÞ
ch¹m m¸t th× trªn c¸c bé phËn nµy xuÊt hiÖn ®iÖn ¸p vµ khi ®ã ng−êi tiÕp xóc vµo cã thÓ bÞ
giËt nguy hiÓm.
-§Ó ®Ò phßng tr−êng hîp nguy hiÓm nµy, ng−êi ta cã thÓ dïng d©y dÉn nèi vá cña thiÕt bÞ
®iÖn víi ®Êt hoÆc víi d©y trung tÝnh hay dïng bé phËn c¾t ®iÖn b¶o vÖ.
1.Nèi ®Êt b¶o vÖ trôc tiÕp:
-Dïng d©y kim lo¹i nèi bé phËn trªn th©n m¸y víi cùc nèi ®Êt b»ng s¾t, thÐp ch«n d−íi ®Êt cã
®iÖn trë nhá víi dßng ®iÖn rß qua ®Êt vµ ®iÖn trë c¸ch ®iÖn ë c¸c pha kh«ng bÞ h− háng kh¸c.
-HÖ thèng tiÕp ®Êt ph¶i cã ®iÖn trë ®ñ nhá ®Ó sao cho ng−êi khi tiÕp xóc vµo vá cña thiÕt bÞ cã
®iÖn ¸p rß rØ (coi nh− ng−êi m¾c song song víi m¹ch tiÕp ®Êt) th× dßng ®iÖn ch¹y qua c¬ thÓ
kh«ng ®Õn trÞ sè cã thÓ g©y nguy hiÓm cho søc khoÎ vµ sù sèng. H×nh thøc nµy ¸p dông ë
m¹ng 3 pha cã trung hoµ c¸ch ®iÖn.
-Theo quy ®Þnh hiÖn hµnh th×:
· §èi víi thiÕt bÞ ®iÖn cã ®iÖn ¸p ®Õn 1000V trong c¸c l−íi ®iÖn cã trung tÝnh ®Æt c¸ch
®iÖn ®èi víi mÆt ®Êt, trÞ sè ®iÖn trë nèi ®Êt ph¶i kh«ng lín h¬n 4Ω.
· §èi víi thiÕt bÞ ®iÖn cã c«ng suÊt nguån nhá h¬n 100KVA cho phÐp ®iÖn trë nèi ®Êt
tíi 10Ω.
-Trong tr−êng hîp tiÕp xóc nh− trªn, ng−êi ®−îc coi lµ m¾c vµo dßng ®iÖn rß song song víi
cùu nèi ®Êt. Theo ®Þnh luËt ph©n bè dßng diÖn, ta cã:
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+Id: c−êng ®é dßng ®iÖn rß (A). Trong c¸c m¹ng víi trung hoµ c¸ch ®iÖn cã ®iÖn ¸p
d−íi 1000V→Id kh«ng lín qu¸ 10A (th−êng 4-6A).
+Rn: ®iÖn trë tÝnh to¸n cña ng−êi (Ω).
+Rnd: ®iÖn trë cùc nèi ®Êt (Ω).
⇒Khi trÞ sè dßng ®iÖn rß nhá h¬n vµ ®iÖn trë ng−êi lín h¬n, dßng ®iÖn ®i qua ng−êi sÏ cßn
nhá n÷a, b¶o ®¶m an toµn cho ng−êi.
2.Nèi ®Êt b¶o vÖ qua d©y trung hoµ:
-Dïng d©y dÉn nèi víi th©n kim lo¹i cña m¸y vµo d©y trung hoµ ®−îc ¸p dông trong m¹ng cã
®iÖn ¸p d−íi 1000V, 3 pha 4 d©y cã d©y trung tÝnh nèi ®Êt, nèi ®Êt b¶o vÖ trùc tiÕp nh− trªn sÏ
kh«ng ®¶m b¶o an toµn khi ch¹m ®Êt 1 pha. Bëi v×:
· Khi cã sù cè (c¸ch ®iÖn cña thiÕt bÞ ®iÖn háng) sÏ xuÊt hiÖn dßng ®iÖn trªn th©n m¸y
th× lËp tøc 1 trong c¸c pha sÏ g©y ra ®o¶n m¹ch vµ trÞ sè cña dßng ®iÖn m¹ch sÏ lµ:
U
Rd + Ro
Trong ®ã:
+U: ®iÖn ¸p cña m¹ng (V).
+Rd: ®iÖn trë ®Êt (Ω).
+Ro: ®iÖn trë cña nèi ®Êt (Ω).
· Do ®iÖn ¸p kh«ng lín nªn trÞ sè dßng ®iÖn Inm còng kh«ng lín vµ cÇu ch× cã thÓ kh«ng
ch¸y, t×nh tr¹ng ch¹m ®Êt sÏ kÐo dµi, trªn vá thiÕt bÞ sÏ tån t¹i l©u dµi 1 ®iÖn ¸p víi trÞ
sè:
U d = Rd .I nm =
U d
Rd + Ro
(6.7)
-Râ rµng ®iÖn ¸p nµy cã thÓ ®¹t ®Õn møc ®é nguy hiÓm. V× vËy ®Ó cÇu ch× vµ b¶o vÖ kh¸c c¾t
m¹ch th× ph¶i nèi trùc tiÕp vë thiÕt bÞ víi d©y trung tÝnh vµ ph¶i tÝnh to¸n sao cho dßng ®iÖn
ng¾n m¹ch Inm víi ®iÒu kiÖn:
· Lín h¬n 3 lÇn dßng ®iÖn ®Þnh møc cña cÇu ch× gÇn nhÊt Icc:
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· HoÆc lín h¬n 1.5 lÇn dßng ®iÖn cÇn thiÕt ®Ó c¬ cÊu tù ®éng c¾t ®iÖn gÇn nhÊt Ia:
-ViÖc nèi trùc tiÕp vá thiÕt bÞ ®iÖn víi d©y trung tÝnh lµ nh»m môc ®Ých t¨ng trÞ sè dßng ®iÖn
ng¾n m¹ch Inm ®Ó cho cÇu ch× vµ c¸c b¶o vÖ kh¸c c¾t ®−îc m¹ch ®iÖn.
3.C¾t ®iÖn b¶o vÖ tù ®éng:
-Dïng trong tr−êng hîp khi 2 ph−¬ng ¸n trªn kh«ng ®¹t yªu cÇu an toµn. C¬ cÊu nµy cã thÓ
sö dông c¶ ë m¹ng 3 pha c¸ch ®iÖn ®èi víi ®Êt, lÉn ë m¹ng cã trung tÝnh nèi ®Êt.
-§Æc ®iÓm c¬ b¶n cña nã lµ cã thÓ c¾t ®iÖn nhanh trong kho¶ng thêi gian 0.1-0.2s khi xuÊt
hiÖn ®iÖn ¸p trªn vá thiÕt bÞ ®Õn trÞ sè quy ®Þnh.
-§èi víi m¹ng 3 pha, c¬ cÊu nµy ®−îc m¾c nèi tiÕp vµo d©y nèi th©n ®éng c¬ ®iÖn víi cùc nèi
®Êt hoÆc víi d©y trung hoµ vµ sÏ ho¹t ®éng d−íi t¸c dông cña dßng ®iÖn rß hoÆc dßng ®iÖn
ng¾n m¹ch trong thêi gian ®iÖn m¸t ra th©n m¸y vµ sÏ c¾t ®iÖn khái m¸y.
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-C¸c dông cô b¶o vÖ chÝnh lµ lo¹i chÞu ®−îc ®iÖn ¸p khi tiÕp xóc víi ph©n dÉn ®iÖn trong 1
thêi gian dµi l©u.
-C¸c dông cô phô trî lµ c¸c lo¹i b¶n th©n kh«ng ®¶m b¶o an toµn khái ®iÖn ¸p tiÕp xóc nªn
ph¶i dïng kÕt hîp víi dông cô chÝnh ®Ó t¨ng c−êng an toµn h¬n.
2.Tuú theo chøc n¨ng cña ph−¬ng tiÖn b¶o vÖ:
a/C¸c dông cô kü thuËt ®iÖn:
-B¶o vÖ ng−êi khái c¸c phÇn dÉn ®iÖn cña thiÕt bÞ vµ ®Êt lµ bôc c¸ch ®iÖn, th¶m c¸ch ®iÖn,
ñng vµ g¨ng tay c¸ch ®iÖn.
-Bôc c¸ch ®iÖn dïng ®Ó phôc vô c¸c thiÕt bÞ ®iÖn cã ®iÖn ¸p bÊt kú, th−êng cã kÝch th−íc
75*75cm hoÆc 75*40cm, cã ch©n sø c¸ch ®iÖn.
-Th¶n c¸ch ®iÖn dïng ®Ó phôc vô c¸c thiÕt bÞ ®iÖn cã ®iÖn ¸p tõ 1000V trá xuèng, th−êng cã
kÝch th−íc 75*75cm, dµy 0.4-1cm.
-G¨ng tay c¸ch ®iÖn dïng cho ®Ó phôc vô c¸c thiÕt bÞ ®iÖn cã ®iÖn ¸p d−íi 1000V ®èi víi
dông cô b¶o vÖ chÝnh vµ ®iÖn ¸p trªn 1000V ®èi víi dông cô phô trî. ñng, giµy c¸ch ®iÖn lµ
lo¹i dông cô b¶o vÖ phô trî, ñng c¸ch ®iÖn dung víi ®iÖn ¸p trªn 1000V, cßn giµy c¸ch ®iÖn
dïng ®iÖn ¸p d−íi 1000V.
b/C¸c dông cô b¶o vÖ khi lµm viÖc d−íi ®iÖn thÕ:
-Ng−êi ta dïng sµo c¸ch ®iÖn, k×m c¸ch ®iÖn vµ c¸c dông cô thî ®iÖn kh¸c.
-Sµo c¸ch ®iÖn dïng ®Ó ®ãng më cÇu dao c¸ch ly vµ ®Æt thiÕt bÞ nèi ®Êt. Nã cã phÇn mãc ch¾c
ch¾n trªn ®Çu, phÇn c¸ch ®iÖn vµ c¸n ®Ó cÇm (dµi h¬n 10cm lµm b»ng vËt liÖu c¸ch ®iÖn nh−
ebonit, tectonit,...).
-K×m c¸ch ®iÖn dïng ®Ó th¸o l¾p cÇu ch× èng, ®Ó thao t¸c trªn nh÷ng thiÕt bÞ ®iÖn cã ®iÖn ¸p
trªn 35000V. K×m c¸ch ®iÖn còng ph¶i cã tay cÇm dµi h¬n 10cm vµ lµm b»ng vËt liÖu c¸ch
®iÖn.
-C¸c lo¹i dông cô thî ®iÖn kh¸c dïng ®Ó kiÓm tra xem cã ®iÖn hay kh«ng, cã thÓ sö dông c¸c
lo¹i sau:
· Víi thiÕt bÞ cã ®iÖn ¸p trªn 1000V th× sö dông ®ång hå ®o ®iÖn ¸p hoÆc k×m ®o ®iÖn.
· Víi c¸c thiÕt bÞ cã ®iÖn ¸p d−íi 500V th× sö dông bót thö ®iÖn, ®Ìn ¾c quy.
c/C¸c lo¹i dông cô b¶o vÖ kh¸c:
-C¸c lo¹i ph−¬ng tiÖn ®Ó tr¸nh t¸c h¹i cña hå quang ®iÖn nh− kÝnh b¶o vÖ m¾t, quÇn ¸o kh«ng
b¾t ch¸y, bao tay v¶i b¹t, mÆt n¹ phßng h¬i ®éc,...
-C¸c lo¹i ph−¬ng tiÖn dïng ®Ó lµm viÖc trªn cao nh− th¾t l−ng b¶o hiÓm, mãc ch©n cã quai
da, d©y ®eo, xÝch an toµn, thang xÐp, thang n©ng, thang g¸, chßi èng lång,...
3.C¸c biÓn b¸o phßng ngõa:
-Ngoµi ra ®Ó ®¶m b¶o an toµn cÇn cã c¸c biÓn b¸o phßng ngõa dïng ®Ó:
· B¸o vµ ng¨n kh«ng cho ng−êi tíi gÇn c¸c trang thiÕt bÞ cã ®iÖn.
· Ng¨n kh«ng thao t¸c c¸c kho¸, cÇu dao cã thÓ phßng ®iÖn vµo n¬i ®ang söa ch÷a hoÆc
lµm viÖc.
-Theo môc ®Ých, c¸c lo¹i biÓn b¸o cã thÓ chia lµm 4 nhãm:
· BiÓn b¸o ng¨n ngõa: “CÊm sê mã-chÕt ng−êi”, “§iÖn cao ¸p-nguy hiÓm chÕt ng−êi”,...
· BiÓn b¸o cÊm: “Kh«ng ®ãng ®iÖn-cã ng−êi lµm viÖc”, “Kh«ng ®ãng ®iÖn-lµm viÖc trªn
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· BiÓn b¸o lo¹i cho phÐp: “Lµm viÖc ë ®©y” ®Ó chØ râ chç lµm viÖc cho c«ng nh©n,...
· BiÓn b¸o lo¹i nh¾c nhë ®Ó nh¸c nhë vÒ c¸c biÖn ph¸p cÇn thiÕt: “Nèi ®Êt”,...
-C¸c lo¹i biÓn b¸o di ®éng dïng trong c¸c trang thiÕt bÞ cã ®iÖn ¸p trªn vµ d−íi 1000V cÇn
lµm b»ng vËt liÖu c¸ch ®iÖn hoÆc dÉn ®iÖn xÊu (chÊt dÎo hoÆc b×a cøng c¸ch ®iÖn). CÊm dïng
s¾t t©y lµm biÓn b¸o. PhÝa trªn biÓn b¸o ph¶i cã lç vµ mãc ®Ó treo.
§3 cÊp cøu ng−êi bÞ n¹n
-Khi ng−êi bÞ tai n¹n ®iÖn ë møc ®é nguy hiÓm th× ph¶i ®−îc cÊp cøu ngay. CÊp cøu chia lµm
2 giai ®o¹n:
· Cøu ng−êi ra khái m¹ng ®iÖn.
· Sau ®ã lµ h« hÊp nh©n t¹o hoÆc thæi ng¹t.
-CÊp cøu ng−ßi bÞ ®iÖn giËt rÊt quan träng. N¹n nh©n cã thÓ sèng hay chÕt lµ do cÊp cøu cã
®−îc nhanh chãng vµ ®óng ph−¬ng ph¸p hay kh«ng. BÊt kú lóc nµo còng ph¶i tiÕn hµnh khÈn
tr−¬ng vµ kiªn tr×. Bëi v× chØ trÓ 1 chót cã thÓ dÉn ®Õn hËu qñ kh«ng cøu ch÷a ®−îc hoÆc thiÕu
kiªn tr× h« hÊp nh©n t¹o sÏ lµm cho ng−êi bÞ n¹n kh«ng håi tØnh ®−îc mÆc dï míi ë møc ®é
cã thÓ cøu ch÷a ®−îc.
I.Cøu ng−êi bÞ n¹n khái nguån ®iÖn:
-LËp tøc c¾t c«ng t¾c, cÇu dao.
-NÕu kh«ng lµm nh− vËy ®−îc th× dïng dông cô ng¾t ®iÖn ®Ó c¾t ®øt m¹ch ®iÖn nh− dïng dao
c¾t cã c¸n gç kh«, ®øng trªn tÊm gç kh« vµ c¾t lÇn l−ît tõng d©y mét.
-Còng cã thÓ lµm ng¾n m¹ch b»ng c¸ch qu¨ng lªn trªn d©y dÉn 1 ®o¹n kim lo¹i hoÆc d©y dÉn
®Ó lµm ch¸y cÇu ch×. Khi lµm nh− vËy ph¶i chó ý ®Ò phßng ng−êi bÞ n¹n cã thÓ bÞ ng· hoÆc
chÊn th−¬ng.
-NÕu kh«ng thÓ lµm ®−îc b»ng c¸ch trªn th× ph¶i t¸ch ng−êi bÞ n¹n ra khái thiÕt bÞ b»ng søc
ng−êi thËt nhanh chãng nh−ng nh− vËy dÔ nguy hiÓm cho ng−êi cøu nªn ®ßi hái ng−êi cøu
ph¶i kh« r¸o vµ chØ cÇm vµo quÇn ¸o kh« cña ng−êi bÞ n¹n mµ giËt.
-§−a ngay ng−êi bÞ n¹n ra n¬i tho¸ng khÝ, ®¾p quÇn ¸o Êm vµ ®i gäi b¸c sÜ. NÕu kh«ng kÞp
gäi b¸c sÜ th× ph¶i tiÕn hµnh h« hÊp nh©n t¹o.
II.Ph−¬ng ph¸p h« hÊp nh©n t¹o:
-H« hÊp nh©n t¹o cÇn ph¶i ®−îc tiÕn hµnh ngay khi thÇy thuèc ch−a ®Õn. Nªn lµm ngay t¹i
chç bÞ n¹n, kh«ng mang ®i xa. Thêi gian h« hÊp cÇn ph¶i kiªn tr×, cã tr−êng hîp ph¶i h« hÊp
®Õn 24 giê. Lµm h« hÊp nh©n t¹o ph¶i liªn tôc cho ®Õn khi b¸c sÜ ®Õn.
-MÆc dï kh«ng cßn dÊu hiÖu cña sù sèng còng kh«ng ®−îc coi lµ n¹n nh©n ®· chÕt. ChØ ®−îc
xem lµ chÕt nÕu n¹n nh©n vì sä hoÆc ch¸y ®en. Tr−íc khi h« hÊp cÇn ph¶i cëi vµ níi quÇn ¸o
cña n¹n nh©n, c¹y miÖng ra khi miÖng c¾n chÆt.
-Cã 2 ph−¬ng ph¸p h« hÊp nh©n t¹o lµ h« hÊp do 1 ng−êi vµ h« hÊp do 2 ng−êi.
1.Ph−¬ng ph¸p h« hÊp do 1 ng−êi:
-§Æt n¹n nh©n n»m sÊp, mÆt nghiªng sang 1 bªn vµ kª tay ph¶i gÊp l¹i cho dÔ thë, tay tr¸i
duçi th¼ng vÒ phÝa tr−íc. Ng−êi cÊp cøu quú s¸t ®åi gèi vµo x−¬ng h«ng, ®Ó 2 tay lªn s−ên
n¹n nh©n:![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image001.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image002.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image003.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image004.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image006.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image008.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image010.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image011.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image013.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image014.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image015.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image016.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image018.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image020.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image021.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image022.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image024.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image025.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image026.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image027.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image028.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image029.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image030.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image031.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image032.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image033.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image034.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image035.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image036.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image037.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image038.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image039.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image040.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image041.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image042.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image043.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image044.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image045.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image046.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image047.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image048.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image049.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image050.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image051.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image052.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image053.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image055.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image056.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image057.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image058.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image059.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image060.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image061.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image062.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image063.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image064.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image065.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image066.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image067.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image068.gif)
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· Lóc bãp s−ên (¸n vµo phÇn d−íi cña lång ngùc 1 c¸ch nhÞp nhµng) ph¶i ng· ng−êi vÒ
phÝa tr−íc, ®øng lªn 1 tý cho cã søc ®Ì xuèng. §©y lµ ®éng t¸c thë ra, miÖng ®Õm 1, 2,
3 vµ tay vÉn ®Ó nh− cò.
· Khi lµm ®éng t¸c hÝt vµo, ph¶i tõ tõ h¹ ng−êi xuèng, th¶ tay ra vµ ®Õm 4, 5, 6.
-Ph−¬ng ph¸p nµy cã −u ®iÓm:
· §êm r¶i vµ nh÷ng chÊt trong d¹ dµy kh«ng tråi lªn häng.
· L−ìi kh«ng tôt vµo häng, do ®ã kh«ng lµm c¶n kh«ng khÝ l−ít qua.
2.Ph−¬ng ph¸p h« hÊp do 2 ng−êi:
-NÕu cã 2 ng−êi cÊp cøu th× 1 ng−êi chÝnh vµ 1 ng−êi phô:
· N¹n nh©n ®Æt n»m ng÷a, dïng gèi hoÆc quÇn ¸o kª ë l−ng, ®Çu ng÷a ra phÝa sau.
· Ng−êi phô cÇm l−ìi cña n¹n nh©n khÏ kÐo Ên xuèng d−íi c»m.
· Ng−êi chÝnh quú phÝa tr−íc kÐo 2 tay n¹n nh©n gi¬ lªn vµ ®−a vÒ phÝa tr−íc ®Õm 1, 2,
3→ ®©y lµ ®éng t¸c hÝt vµo; cßn ®éng t¸c thë ra th× tõ tõ co tay n¹n nh©n l¹i cho cïi
tay n¹n nh©n Ðp vµo lång ngùc ®ång thêi h¬i ®øng ®øng ng−êi lªn 1 chót cho cã søc ®Ì
xuèng vµ ®Õm 4, 5, 6.
-§Æc ®iÓm cña ph−¬ng ph¸p nµy lµ t¹o cho n¹n nh©n thë ra hÝt vµo ®−îc nhiÒu kh«ng khÝ h¬n
nh−ng ph¶i theo dâi cuèng häng v× ®êm r¶i vµ nh÷ng chÊt trong d¹ dµy cã thÓ lµm c¶n trë
kh«ng khÝ ®i qua.
*/Chó ý: CÊp cøu ph¶i dóng nhÞp thë b×nh th−êng tøc lµ víi tèc ®é 13-16 lÇn trong 1 phót.
III.Ph−¬ng ph¸p hµ h¬i thæi ng¹t:
-§©y lµ ph−¬ng ph¸p cã hiÖu qu¶ vµ khoa häc, tiÖn lîi vµ dÔ lµm.
-Tr×nh tù lµm nh− sau:
· Tr−íc khi thæi ng¹t cÇn mãc hÕt ®êm r¶i vµ lÊy ra c¸c dÞ vËt nh− r¨ng gi¶, thøc
¨n,...kiÓm tra xem khÝ qu¶n cã th«ng suèt kh«ng.
· Ng−êi lµm cÊp cøu kÐo ng÷a mÆt n¹n nh©n ra phÝa sau, c»m ng÷a lªn trªn.
· HÝt 1 h¬i thËt m¹nh, tay bÞt mòi n¹n nh©n, ¸p mèi vµo måm cña n¹n nh©n vµ thæi thËt
m¹nh→Lóc nµy phæi n¹n nh©n ®Çy h¬i.
· Ng−êi cÊp cøu rêi måm n¹n nh©n ®Ó hÝt thËt m¹nh råi l¹i thæi nh− cò. Lµm 10 lÇn liªn
tiÕp ®èi víi ng−êi lín, 20 lÇn ®èi víi trÎ em. Nhê d−ìng khÝ thõa trong h¬i thë cña
ng−êi cÊp cøu mµ hång cÇu cã d−ìng khÝ, c¬ quan hè hÊp vµ tuÇn hoµn cña ng−êi bÞ
n¹n cã thÓ håi phôc l¹i.
-NÕu cÊp cøu 2 ng−êi th× kÕt hîp 1 ng−êi thæi ng¹t, 1 ng−êi xoa bãp tim ngoµi lång ngùc.
§4 b¶o vÖ chèng sÐt
I.Kh¸i niÖm vÒ sÐt:
-SÐt lµ hiÖn t−îng phãng ®iÖn cña tÜnh ®iÖn khÝ quyÓn gi÷a ®¸m m©y d«ng mang ®iÖn tÝch víi
mÆt ®Êt hoÆc c¸c ®¸m m©y d«ng mang ®iÖn tÝch tr¸i dÊu nhau.
-TÜnh ®iÖn khÝ quyÓn xuÊt hiÖn lµ do sù ma s¸t cña h¬i n−íc vµ sau ®ã cña c¸c h¹t n−íc víi
kh«ng khÝ ë trong líp kh«ng khÝ Èm d−íi thÊp còng nh− ë trong ®¸m m©y trªn cao. Khi c¸c
h¹t n−íc trong ®¸m m©y chóng sÏ tÝch ®iÖn vµ ®¸m m©y sÏ trë thµnh vËt mang nh÷ng ®iÖn![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image001.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image002.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image003.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image004.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image006.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image008.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image010.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image011.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image007.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image009.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image005.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image013.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image014.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image015.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image016.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image018.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image020.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image021.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image022.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image024.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image025.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image026.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image027.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image028.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image012.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image029.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image030.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image031.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image032.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image033.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image034.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image023.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image035.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image036.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image037.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image038.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image039.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image040.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image041.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image042.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image043.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image017.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image044.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image045.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image046.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image047.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image048.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image049.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image050.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image051.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image052.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image053.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image019.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image055.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image056.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image057.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image058.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image059.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image054.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image060.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image061.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image062.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image063.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image064.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image065.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image066.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image067.gif) ![](file:///C:\DOCUME~1\Admin\LOCALS~1\Temp\msohtml1\01\clip_image068.gif)
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tÝch ®ã. Do kÕt qu¶ t¸c ®éng t−¬ng hç cña c¸c h¹t n−íc mang ®iÖn tÝch víi c¸c luång kh«ng
khÝ sÏ cã sù ph©n chia thµnh h¹t lín mang ®iÖn d−¬ng vµ h¹t nhá mang ®iÖn ©m. Theo ®Þnh
luËt khÝ ®éng häc th×:
· C¸c h¹t n−íc nhá mang ®iÖn ©m sÏ tô l¹i vµ tô thµnh ®¸m m©y mang ®iÖn ©m.
· C¸c h¹t lín sÏ l¾ng xuèng d−íi vµ sÏ t¹o thµnh ®¸m m©y mang ®iÖn d−¬ng.
→Khi ®¸m m©y mang ®iÖn d−¬ng di chuyÓn do hiÖn t−îng c¶m øng tÜnh ®iÖn trªn bÒ mÆt ®Êt
sÏ xuÊt hiÖn ®iÖn tÝch ©m. Nh− vËy sÏ t¹o thµnh 1 tô ®iÖn ®Æc biÖt víi líp kh«ng khÝ ë gi÷a,
c¸c bÒ mÆt tô ®iÖn lµ m©y vµ ®Êt. NÕu thÕ hiÖu ®¹t ®Õn trÞ sè cùc h¹n sÏ xuÊt hiÖn sù phãng tia
löa kÌm theo tia chíp s¸ng chãi vµ tiÕng næ d÷ déi.
-§iÖn ¸p gi÷a ®¸m m©y d«ng vµ mÆt ®Êt cã thÓ ®¹t tíi trÞ sè hµng chôc, thËm chÝ hµng tr¨m
triÖu volt. T¸c h¹i cña nã lµ:
· §èi víi ng−êi vµ sóc vËt, sÐt nguy hiÓm tr−íc hÕt nh− 1 nguån cã ®iÖn ¸p vµ dßng lín.
· Dßng sÐt cã nhiÖt ®é rÊt lín cã thÓ g©y nªn ®¸m ch¸y rÊt nguy hiÓm ®èi víi c¸c kho
nhiªn liÖu vµ vËt liÖu dÔ næ.
· SÐt cã thÓ ph¸ huû vÒ mÆt c¬ häc cã thÓ lµm næ tung c¸c th¸p cao, c©y cèi, ®−êng d©y
®iÖn, ®−êng ray, èng n−íc,...
-Nguy hiÓm lµ sÐt ®¸nh trùc tiÕp, khi ®ã kªnh tia chíp ®i qua nhµ vµ c«ng tr×nh:
· C−êng ®é ë kªnh tia chíp ®¹t tíi 200.000A, ®iÖn ¸p tíi 150.000.000V.
· ChiÒu dµi kªnh tia chíp cã thÓ ®¹t tíi hµng tr¨m, hµng ngh×n mÐt.
· Thêi gian phãng ®iÖn cña tia chíp tõ 0.1-1s, nhiÖt ®é ®¹t tíi 6.000-10.000oC.
-Kh¶ n¨ng c¸c c«ng tr×nh trªn mÆt ®Êt bÞ sÐt ®¸nh trùc tiÕp cµng lín nÕu c«ng tr×nh cµng cao
vµ do ®ã kho¶ng c¸ch c¸c ®iÓm gi÷a cao nhÊt cña c«ng tr×nh ®Õn ®¸m m©y mang ®iÖn cµng
gÇn.
-Chèng sÐt lµ biÖn ph¸p b¶o vÖ khái sù phãng ®iÖn cña tÜnh ®iÖn khÝ quyÓn, ®¶m b¶o an toµn
cho ng−êi, nhµ cöa, c«ng tr×nh, thiÕt bÞ vµ vËt liÖu khái bÞ ch¸y næ vµ ph¸ huû.
II.CÊu t¹o cét thu l«i:
- 76 -
-§Ó b¶o vÖ c¸c c«ng tr×nh th−êng dïng cét chèng sÐt cßn gäi lµ cét thu l«i. §©y lµ cét thÐp cã
®é cao lín h¬n ®é cao cña c«ng tr×nh cÇn ®−îc b¶o vÖ. Trªn ®Ønh cét cã g¾n mòi nhän kim
lo¹i thu sÐt. Kim nµy ®−îc nèi víi d©y dÉn sÐt xuèng ®Êt ®Ó ®i vµo vËt nèi ®Êt. D©y dÉn sÐt
®¶m b¶o cho dßng sÐt ®i theo nã xuèng nèi ®Êt vµ vËt nèi ®Êt ®¶m b¶o sù tiÕp xóc ph©n bè
trùc tiÕp víi ®Êt trªn 1 diÖn tÝch lín.
-Kh«ng gian xung quanh cét thu l«i ®−îc b¶o vÖ b»ng c¸ch thu sÐt vµo cét gäi lµ ph¹m vi
hoÆc vïng b¶o vÖ.
-Cho ®Õn nay chØ cã 1 c¸ch duy nhÊt lµ x¸c ®Þnh ph¹m vÞ b¶o vÖ b»ng thùc nghiÖm trªn m«
h×nh; tuy cßn nhiÒu nh−îc ®iÓm nh−ng ®· qua 1 thêi gian kh¸ dµi ®−îc kiÓm nghiÖm trong
thùc tÕ, kÕt qu¶ nhËn ®−îc víi ®é tin cËy lín. Mét cét thu l«i ®éc lËp th× ph¹m vi b¶o vÖ cña
nã lµ 1 h×nh nãn xo¸y víi ®−êng sinh theo c«ng thøc:
rx = 1.6h
h − hx
h + hx
p
(6.8)
Trong ®ã:
+h: ®é cao cña cét thu l«i.
+hx: ®é cao c«ng tr×nh cÇn b¶o vÖ.
+rx: b¸n kÝnh ®−îc b¶o vÖ ë ®é cao hx.
+p: hÖ sè hiÖu chØnh theo ®é cao cña cét thu l«i ®−îc tÝnh nh− sau:
⎧ p = 1 ↔ h ≤ 30m.
⎪
⎨ 5.5
⎩ h
-§Ó ®¬n gi¶n khi sö dông, ng−êi ta th−êng thay thÕ ®−êng cong bËc hai rx(hx) b»ng 1 ®−êng
g·y khóc theo h×nh vÏ sau:
Khi ®ã c¸c ®−êng g·y khóc víi c¸c ph−¬ng tr×nh ®¬n gi¶n sau:
- 77 -
-Thu l«i kÐp gåm tõ 2 thanh thu l«i cao kh«ng qu¸ 60m víi kho¶ng c¸ch a≤5h:
MÆt ®øng c¾t theo k-k MÆt b»ng c¾t theo x-x
1.Biªn giíi vïng b¶o vÖ ë ®é cao hx 2.Biªn giíi vïng b¶o vÖ ë mÆt ®Êt.
-Biªn giíi vïng b¶o vÖ cét thu l«i kÐp:
· PhÇn trªn lµ ®−êng cong ®−îc v¹ch ra bëi b¸n kÝnh R tõ ®iÓm O n»m trung ®iÓm cña
kho¶ng c¸ch gi÷a 2 cét thu l«i trªn ®é cao H=4h.
· Nh÷ng phÇn 2 bªn cña vïng b¶o vÖ sÏ thiÕt lËp nh− vïng b¶o vÖ cña cét thu l«i ®éc
lËp.
-H×nh d¸ng vïng b¶o vÖ ë tiÕt diÖn O-O còng ®−îc x¸c ®Þnh nh− thÕ nh−ng thay h b»ng ho,
tøc lµ:
-Khi ®· biÕt c¸c trÞ sè h vµ a th× chiÒu cao vïng b¶o vÖ ë gi÷a thu lèi kÐp sÏ lµ:
ho = 4h − 9h 2 + 0.25a 2
Trong ®ã:
+h: chiÒu cao cét thu l«i.
+a: kho¶ng c¸ch gi÷a 2 cét thu l«i.
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