tcn 68 - 174 2006-65e6bb617295

nh xut bn bu in

b bu chnh, vin thng

tcn 68 - 174: 2006

tiu chun ngnhTCN

QUY PHM CHNG ST V TIP TCHO CC CNG TRNH VIN THNG

Code of Practice for Lightning protection and Earthingfor Telecommunication Plants

(Sot xt ln 1)

TCN 68 - 174: 2006

2

mc lc

Li ni u ................................................................................................................................4

Chng I: Cc quy nh chung................................................................................................5 1.1 Phm vi p dng .......................................................................................................5

1.2 Mc ch p dng .....................................................................................................5

1.3 Thut ng, nh ngha v gii thch ..........................................................................5

Chng II: Yu cu trang thit b chng st, cu hnh u ni v tip t .......................11

2.1 H thng chng st nh trc tip ..........................................................................11

2.2 Thit b chng st (SPD).........................................................................................14

2.3 Cu hnh u ni v tip t trong nh trm vin thng .........................................15

Chng III: Kho st v o c...........................................................................................19

3.1 Quy nh chung ......................................................................................................19

3.2 Nhim v kho st ..................................................................................................19

3.3 o in tr sut ca t ..........................................................................................20 Chng IV: Thit k chng st v tip t ........................................................................21

4.1 Nguyn tc chung ...................................................................................................21

4.2 Thit k chng st bo v nh trm vin thng ......................................................21

4.3 Thit k chng st bo v ct ng ten vin thng...................................................24

4.4 Thit k chng st bo v ng dy thng tin ......................................................24

4.5 Thit k h thng tip t .......................................................................................25 Chng V: Thi cng lp t trang thit b chng st v h thng tip t .................28

5.1 Nguyn tc chung ...................................................................................................28

5.2 Thi cng lp t h thng chng st nh trc tip ................................................28

5.3 Lp t thit b chng st lan truyn .....................................................................28

5.4 Thi cng lp t chng st bo v ng dy thng tin .........................................29

5.5 Thi cng h thng tip t ......................................................................................30 Chng VI: Kim tra, nghim thu cc h thng tip t v chng st .........................31

6.1 Thnh phn nghim thu ..........................................................................................31

6.2 Nghim thu cc h thng, thit b chng st ..........................................................31

6.3 Kim tra, nghim thu h thng tip t ..................................................................32 Chng VII: Quy nh v qun l v bo dng ..............................................................32

7.1 Trong qu trnh qun l v khai thc h thng tip t v chng st, phi thc hin kim tra, bo dng cc trang, thit b theo nhng quy nh sau: ......32

TCN 68 - 174: 2006

3

7.2 Quy nh v thi gian kim tra nh k ..................................................................32

7.3 Quy nh v thi gian kim tra t xut .................................................................32

7.4 Ni dung kim tra nh k v t xut ...................................................................32

7.5 Sau khi kim tra nu pht hin ch h hng phi sa cha ngay: ..........................33

7.6 Mi ni dung kim tra sa cha nh k hoc t xut u phi ghi vo l lch k thut v lu h s. ......................................................33

Ph lc A (Quy nh): Cu hnh u ni v tip t trong nh trm vin thng ....................34

Ph lc B (Quy nh): Xc nh vng bo v ca h thng chng st nh trc tip ............35

Ph lc C (Quy nh): Tnh ton tip t cho cc cng trnh vin thng ..........................38

Ph lc D (Quy nh): Trnh t thi cng h thng tip t .................................................56

Ph lc E (Tham kho): Cc c im kh tng v a cht ca Vit Nam ....................71

Ph lc F (Tham kho): Tnh ton h s che chn ca dy chng st ngm.....................81

Bng t vit tt .............................................................................................................82

Ti liu tham kho.................................................................................................................83

TCN 68 - 174: 2006

4

LI NI U

Tiu chun Ngnh TCN 68 - 174: 2006 "Quy phm chng st v tip t cho cc cng trnh vin thng (Sot xt ln 1)" c xy dng trn c s cc quy nh, hng dn v Khuyn ngh ca Lin minh Vin thng Quc t (ITU), Vin Tiu chun Vin thng chu u (ETSI) p ng cc yu cu k thut theo cc tiu chun Ngnh v chng st v tip t cho cc cng trnh vin thng, c tham kho cc tiu chun v cng ngh chng st ca mt s quc gia trn th gii.

Tiu chun Ngnh TCN 68 - 174: 2006 do Vin Khoa hc K thut Bu in (RIPT) bin son theo ngh ca V Khoa hc - Cng ngh v c ban hnh theo Quyt nh s 28/2006/Q-BBCVT ngy 25 thng 7 nm 2006 ca B trng B Bu chnh, Vin thng.

V khoa hc - cng ngh

TCN 68 - 174: 2006

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Quy phm Chng st v tip t cho cc cng trnh vin thng

(Ban hnh km theo Quyt nh s 28/2006/Q-BBCVT ngy 25/7/2006 ca B trng B Bu chnh, Vin thng)

Chng I

Cc quy nh chung

1.1 Phm vi p dng

Quy phm ny p dng kho st, thit k, thi cng, nghim thu, qun l cc h thng chng st v tip t cng nh vic la chn cc trang thit b chng st bo v cc cng trnh vin thng, bao gm:

1) Nh trm v ct ng ten vin thng;

2) Thit b v ng dy thng tin;

3) ng in li phc v nh trm.

1.2 Mc ch p dng

Quy phm ny p dng nhm mc ch:

1) Bo v cc cng trnh vin thng, trnh nguy him cho con ngi v hn ch thit hi do st gy ra;

2) Thng nht cc nguyn tc v ni dung trong cng tc kho st, thit k, thi cng, qun l h thng chng st v tip t cho cc cng trnh vin thng.

1.3 Thut ng, nh ngha v gii thch

1.3.1 Ca bin thit b in t

A. Electronic equipment cabinet (EEC)

L mt cu trc che chn bo v thit b in t, m tt c thit b c lp t trong c th tip cn t pha ngoi v khng phi i vo bn trong.

1.3.2 Cu trc che chn bo v thit b in t

A. Electronic Equipment Enclosure (EEE)

L mt cu hnh bo m an ton v mt vt l v mi trng cho cc thit b in t.

1.3.3 Cu trc che chn bo v thit b in t t ni trn mt t

A. Above ground EEE (AG/ EEE)

L mt cu trc che chn bo v thit b in t m i b phn hoc ton b c t ni trn mt t.

1.3.4 Cu trc che chn bo v thit b in t t ngm di mt t

A. Below ground EEE (BG/ EEE)

L mt cu trc che chn bo v thit b in t nm ton b di mt t, tr cng vo, ngun cung cp xoay chiu v thit b iu ho.

TCN 68 - 174: 2006

6

1.3.5 Ca s im ni n

A. SPC Window (SPCW)

L giao din hoc l vng chuyn tip gia mt mng lin kt cch ly v mng lin kt chung. Kch thc ln nht ca chng l 2 m.

1.3.6 Cc tip t

A. Ground pole

L mt vt th bng kim loi, c t trong t hoc tip xc trc tip vi t, dng ni t cc trang, thit b.

1.3.7 Dy (cp) dn t

A. Earthing conductor

L dy (cp) ni tm tip t chnh vi cc tip t.

1.3.8 Dy dn lin kt

A. Bonding conductor

L nhng dy ni cc thnh phn kim loi khng c cch in trong nh trm v nhng thnh phn kim loi t ngoi dn vo vi cc mng lin kt m bo cho s lin kt ng th.

1.3.9 Din tch ri ro

A. Risk Area

L din tch ca min bao quanh cng trnh vin thng, khi st nh vo din tch ny c th gy nguy him cho cng trnh vin thng.

1.3.10 Dng st nh trc tip gy h hng cho cp treo (J)

A. Direct lightning current to aerial cables (J)

L dng st nh nht gy ra h hng cho cp treo khi st nh xung t.

1.3.11 t

A. Earth

L mt vt th dn in, c in th c quy c bng 0.

1.3.12 in cc tip t t nhin

A. Natural Earth Electrode

L cc b phn bng kim loi ca cc cng trnh c tip xc trc tip vi t v c s dng cho mc ch tip t.

1.3.13 in cc tip t nhn to

A. Artificial Earth Electrode

L nhng in cc c s dng ring cho mc ch tip t. N l mt vt dn in c dng bt k (ng, cc, tm, tia nm ngang...) khng bc cch in bn ngoi v c chn trc tip trong t hoc tip xc trc tip vi t.

TCN 68 - 174: 2006

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1.3.14 im ni n

A. Single Point Connection (SPC)

L v tr duy nht trong mt mng lin kt cch ly m thc hin ni vi mng lin kt chung. im ni n phi c kch thc thch hp ni cc ng dn. im ni n thng l mt thanh dn ng, mt s trng hp s dng lp v kim loi ca cp.

1.3.15 in li

A. Public power

L ngun in h th, nhn t mng in ca a phng t trm vin thng.

1.3.16 ng dn kt ni

A. Bonding - bus

L mt dy dn hoc mt nhm dy dn kt ni tm tip t chnh vi cc thnh phn kim loi trong nh trm vin thng.

1.3.17 H s phm cht ca cp c v kim loi

A. Quality factor of a metal - sheathed cable

L t s in p xung cho php ln nht i vi cht cch in gia cc si li cp v v kim loi ca n vi tr khng truyn t ca v. T s ny c biu din bng kA.km.

1.3.18 H s che chn ca v cp kim loi

A. Screen factor of a metal cable sheath

L t s gia tr khng truyn t v tr khng ca mch c to bi v cp v t. N cng c th c xc nh nh t s gia in p st trn vch trong ca v cp kim loi v st p trn mch ngoi c to bi v cp v t i vi mt dng in trn v ngoi. Bit h s che chn ca cp ta c th dng tnh in p xung thay cho tr khng truyn t.

1.3.19 H thng tip t

A. Grounding system

H thng tip t bao gm dn tip t v cp (dy) dn t.

1.3.20 Hiu qu bo v (ca h thng chng st nh trc tip)

A. Protection efficiency (of external lightning protection system)

Hiu qu bo v ca h thng chng st nh trc tip c th hin bng t l gia s ln st nh hng nm khng gy h hng cho cng trnh v tng s ln st nh vo cng trnh.

1.3.21 Khi h thng

A. System block

L ton b cc thit b m khung ca chng v cc phn dn kt hp to thnh mt mng lin kt nht nh.

1.3.22 Mng lin kt

A. Bonding Network (BN)

Mng lin kt l mt tp hp cc phn t dn in c ni vi nhau nhm che chn nh hng in t cho cc h thng thit b in t v con ngi.

TCN 68 - 174: 2006

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1.3.23 Mng lin kt chung

A. Common Bonding Network (CBN)

L mt tp hp cc phn t kim loi lin kt vi nhau mt cch ngu nhin hoc c ch nh to thnh mt mng lin kt chnh bn trong nh trm vin thng.

1.3.24 Mng lin kt dng mt li

A. Mesh Bonding Network (MBN)

L mng lin kt m tt c cc khung thit b, cc gi , cc ca bin, dy dng ca ngun mt chiu c u ni vi mng lin kt chung (CBN) ti nhiu im.

1.3.25 Mng lin kt cch ly

A. Isolated Bonding Network (IBN)

L mng lin kt c mt im ni n n mng lin kt chung hoc mt mng lin kt cch ly khc. Tt c cc mng lin kt cch ly u c 1 ng ni ti t qua im ni n.

1.3.26 Mng lin kt cch ly mt li

A. Mesh - Isolated Bonding Network (M-IBN)

L mng lin kt cch ly m trong cc thnh phn ca n c ni vi nhau to thnh mt cu trc dng mt li.

1.3.27 Mng lin kt cch ly hnh sao

A. Star - Isolated Bonding Network (S-IBN)

L mng lin kt cch ly m trong cc thnh phn ca n c ni vi nhau to thnh mt cu trc dng hnh sao.

1.3.28 Mng TN

A. Terrestrial Neutral

L mng in h p c im trung tnh trc tip ni t.

1.3.29 Mng TN-C

A. Terrestrial Neutral Combined

L mng TN c dy bo v v dy trung tnh (dy PEN) chung. Cc b phn dn in b h (v ca thit b in) c ni vi dy ca mng tip t bo v (PEN).

1.3.30 Mng TN-S

A. Terrestrial neutral separated

L mng TN c dy bo v v dy trung tnh ring bit. Cc b phn dn in b h (v ca thit b in) c ni vi dy tip t bo v (PE). Dy bo v (PE) c th l v kim loi ca cp in lc hoc mt dy dn ring.

1.3.31 Mng TN-C-S

A. Terrestrial Neutral Combined and Separated

L mng TN trong c phn u ca mng c dy bo v v dy trung tnh chung cn phn sau ca mng c dy bo v v dy trung tnh ring bit.

TCN 68 - 174: 2006

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1.3.32 Mng TT

A. Terrestriated Terrestrial

L mng in h p c im trung tnh trc tip ni t cn v thit b in c ni vi tip t bo v c lp.

1.3.33 Mng IT

A. Insulation Terrestrial

L mng in h p c im trung tnh cch ly vi t cn v thit b in c ni vi tip t bo v c lp.

1.3.34 Mng tip t

A. Earthing Network

L mt dn tip t hoc lin kt nhiu dn tip t c chc nng khc nhau trong mt khu vc a l.

1.3.35 Mt st

A. Lightning Density

L s ln st nh xung mt km vung din tch mt t trong mt nm.

1.3.36 Ngy dng

A. Thunderstorm day

L ngy c c trng kh tng m ngi quan st trc nghim nghe r ting sm.

1.3.37 Nh trm vin thng

A. Telecommunication Building

L nh trm trong vn hnh h thng thit b vin thng, nhm mc ch khai thc cc dch v vin thng.

1.3.38 Nh thu bao

A. Subscribers Building L nhng ngi nh ca cc c quan, cc hng hoc nh m ti s dng cc dch v

vin thng.

Nh thu bao c chia lm 2 loi:

a. Nh thu bao dng kinh doanh cc dch v vin thng. l nhng nh thu bao ln cha cc thit b chuyn mch, thit b truyn dn, thit b vi ba...

b. Nh thu bao s dng trc tip cc dch v vin thng:

- Nh thu bao s dng trc tip a dch v vin thng (gm thoi, fax, truyn s liu...).

- Nh thu bao s dng trc tip mt dch v vin thng, nh my fax, hoc my in thoi.

TCN 68 - 174: 2006

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1.3.39 Ngun mt chiu ng v cch ly

A. Isolated d.c return (d.c - I)

L h thng ngun mt chiu trong dy dn v c mt im ni duy nht vi mng lin kt.

1.3.40 Ngun mt chiu ng v chung

A. Common d.c return (d.c - C)

L h thng ngun mt chiu trong dy dn v c ni vi mng lin kt.

1.3.41 Tm tip t chnh

A. Main Earthing Terminal (MET)

L mt tm ng m niken c khoan l, bt vo bn baklit v bt cht vo tng u ni cc ng dn bo v, cc ng dn kt ni ng th v cc ng dn t chc nng vi mng tip t.

1.3.42 Thit b chng st

A. Surge Protective Device (SPD)

Thit b chng st l thit b hn ch qu p t bin v r dng st, bo v cc h thng vin thng. SPD cha t nht mt phn t phi tuyn.

1.3.43 Trm in t xa

A. Remote Electronic Station

L trm hoc ca bin trong cha cc thit b vin thng, bao gm thit b chuyn mch, thit b truyn dn, c t xa trung tm, ch c mt tng, tng din tch mt sn khng ln hn 100 m2, khng c ng ten trn nc v bn cnh trm, c nhu cu ngun in xoay chiu.

1.3.44 Vng kt ni

A. Ring bonding - Bus

L ng dy dn kt ni c dng vng khp kn.

1.3.45 Vng chng st

A. Lightning Protection Zone (LPZ)

L vng c phn chia trong mt khu vc trm vin thng, c c trng bi mc khc nghit ca trng in t v nh hng do st gy nn.

TCN 68 - 174: 2006

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Chng II

yu cu trang thit b chng st, cu hnh u ni v tip t

2.1 H thng chng st nh trc tip

2.1.1 H thng chng st nh trc tip dng in cc Franklin

H thng chng st nh trc tip dng in cc Franklin phi bao gm cc thnh phn sau:

- in cc thu st;

- Dy thot st (dy dn st);

- H thng in cc tip t.

2.1.1.1.in cc thu st

a) in cc thu st phi c dng thch hp (dng thanh, dng dy, dng li) c b tr sao cho to ra vng bo v che ph hon ton cng trnh cn bo v. Phng php xc nh vng bo v ca in cc thu st c trnh by trong Ph lc B.

b) Vt liu v kch thc vt liu c la chn lm in cc thu st phi m bo khng b h hng do nh hng in, in t ca dng st, nh hng ca hin tng n mn v cc lc c hc khc. in cc thu st c th bng cc vt liu: ng, nhm, thp v phi c tit din ti thiu tu theo vt liu c quy nh trong bng 2.1 nh sau:

Bng 2.1: Tit din ti thiu ca in cc thu st

Vt liu lm in cc Tit din nh nht (mm2)

ng Nhm Thp

35 70 50

Ch : C th dng cc loi vt liu khc nu chng m bo cc iu kin tng ng.

c) C th dng cc b phn bng kim loi ca cng trnh (ng mng, ro chn, cc thnh phn ca cu trc mi, ng ng...) lm in cc thu st t nhin nu chng khng b che ph bi cc vt liu cch in v tho mn iu kin v tit din ti thiu i vi in cc thu st.

d) in cc thu st phi c ni vi dy thot st theo ng thng nht, bng cch

hn hoc bt vt, m bo in tr mi ni khng ln hn 0,05 W.

e) Cc in cc thu st c th c kt cu l bn thn i tng cn bo v. Nu dng kt cu bng ct, phi lm bng vt liu m bo bn c hc, ph hp vi iu kin kh hu.

f) Dng in cc thu st c la chn tu theo cu trc ca nh trm. in cc thu st dng thanh thch hp vi cc cu trc nh v nn hn ch cao t 0,2 m n 3 m. in

TCN 68 - 174: 2006

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cc thu st dng dy thch hp vi mi cu trc, c bit vi cc cu trc thp v di. in cc thu st dng li thch hp vi mi cu trc.

Ch : in cc dng thanh khng ph hp vi cu trc c cao ln hn bn knh qu cu ln vi mc bo v tng ng (xem Ph lc B).

2.1.1.2 Dy thot st

a) Dy thot st phi c b tr theo cc ng thng v ngn nht t in cc thu st v m bo tnh dn in lin tc. Bn knh cong ca dy thot st khng c nh hn 20 cm.

b) Vt liu v kch thc vt liu c la chn lm dy thot st phi m bo khng b h hng do nh hng in, in t ca dng st, nh hng ca hin tng n mn v cc lc c hc khc. Dy thot st c th bng cc vt liu: ng, nhm, thp v phi c tit din ti thiu tu theo vt liu c quy nh trong bng 2.2 nh sau:

Bng 2.2: Tit din ti thiu ca dy thot st

Vt liu lm dy thot st Tit din nh nht (mm2)

ng Nhm Thp

16 25 50

Ch : C th dng cc loi vt liu khc nu chng m bo cc iu kin tng ng.

c) Cc dy thot st phi c b tr xung quanh chu vi ca cng trnh cn bo v sao cho khong cch trung bnh gia chng khng vt qu gi tr quy nh trong bng 2.3. Cn t nht 2 dy thot st trong mi trng hp.

Bng 2.3: Khong cch trung bnh gia cc dy thot st

Mc bo v Khong cch trung bnh (m)

I II III IV

10 15 20 25

d) Cc dy thot st phi c lin kt vi nhau bng cc vng dy dn nm ngang cch nhau 20 m, trong c mt vng dy nm gn mt t.

e) C th s dng cc b phn sau ca cng trnh lm dy thot st t nhin nu chng m bo tnh dn in lin tc v kch thc quy nh trong mc b.

- Khung kim loi ca cng trnh;

- Ct thp lin kt ca cng trnh;

- Cc b mt bng kim loi c dy t nht l 0,5 mm;

Ch : Khng cn trang b cc vng dy dn nm ngang nu dng khung kim loi hoc ct thp lin kt ca cng trnh lm dy thot st.

g) Ti v tr ni vi in cc tip t ca mi dy thot st, phi lp mt khp ni phc v o th (tr trng hp dy thot st t nhin). Khp ni ny phi c ng kn trong iu kin bnh thng v c th m ra bng dng c trong trng hp cn o th in tr tip t.

TCN 68 - 174: 2006

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h) S lng dy thot st ph thuc vo in cc thu st:

- Nu h thng in cc thu st gm cc thanh thu st, cn t nht mt dy thot st cho mi thanh thu st;

- Nu h thng in cc thu st gm cc dy thu st, cn t nht 1 dy thot st cho mi u dy thu st;

- Nu h thng in cc thu st c dng li, cn t nht 2 dy thot st phn b u xung quanh chu vi cu trc cn bo v.

2.1.1.3 H thng in cc tip t

a) H thng in cc tip t phi c ni vi cc dy thot st m bo tn nhanh nng lng st xung t v lm cn bng in th gia cc dy thot st.

b) in cc tip t phi lm bng vt liu khng b n mn in ho.

c) Tr s in tr tip t ca h thng in cc tip t phi m bo khng ln hn 10 W.

d) H thng in cc tip t gm cc in cc thng ng v nm ngang thch hp vi trng hp dng in cc thu st dng thanh hoc dy.

e) H thng in cc tip t dng vng ring thch hp vi h thng chng st dng in cc thu st dng li vi nhiu dy thot st v trong trng hp vng t rn, i trc. Vi in cc tip t dng vng, phi m bo t nht 80% chiu di vng ring c chn trong t.

f) Cc in cc tip t chn su c hiu qu trong trng hp in tr sut ca t gim theo su hoc in tr sut ca tng t pha di nh hn so vi tng t su ca cc tip t thng thng.

2.1.2 H thng chng st nh trc tip pht tin o sm

H thng chng st nh trc tip dng in cc pht tin o sm phi bao gm cc thnh phn sau:

- in cc thu st pht tin o sm;

- Dy thot st (dy dn st);

- H thng in cc tip t.

2.1.2.1 in cc thu st pht tin o sm

a) in cc thu st pht tin o sm phi bao gm mt kim thu st c u nhn, mt b phn khi to tia tin o v mt ct ni vi h thng dy thot st. H thng in cc thu st pht tin o sm phi c vng bo v che ph ton b cu trc cn bo v. Phng php xc nh vng bo v ca h thng in cc thu st pht tin o sm c trnh by trong Ph lc B.

b) Kim thu st pht tin o sm phi lm bng ng, hp kim ng hoc thp khng g v phi c tit din ngang ln hn 120 mm2.

c) Kim thu st pht tin o sm phi cao hn cu trc cn bo v t nht l 2 m.

TCN 68 - 174: 2006

14

d) in cc thu st c ni vi dy thot st bng mt h thng lin kt ti ct . H thng lin kt ny phi bo m bn c kh v tip xc in.

2.1.2.2 Dy thot st

Dy thot st ca h thng chng st pht tin o sm tun theo cc quy nh trong mc 2.1.1.2.

S lng dy thot st ph thuc vo in cc thu st:

- Cn t nht mt dy thot st cho mi in cc thu st pht tin o sm.

- Cn hai dy thot st tr ln nu cu trc cn bo v cao hn 28 m v/hoc phn nm ngang ca dy thot st ln hn phn thng ng. Cc dy thot st phi c phn b u xung quanh chu vi cu trc cn bo v.

2.1.2.3 H thng in cc tip t

H thng in cc tip t ca h thng chng st pht tin o sm tun theo cc quy nh trong mc 2.1.1.3.

2.1.3 H thng phn tn nng lng st

2.1.3.1 H thng phn tn nng lng st phi bao gm cc thnh phn sau:

- H thng in cc to ion trung ho;

- H thng dy dn in tch ln in cc;

- H thng tp trung in tch cm ng trong t.

2.1.3.2 H thng phn tn nng lng st phi m bo kh nng ngn cn s hnh thnh tia st nh xung i tng cn bo v

2.2 Thit b chng st (SPD)

2.2.1 Nguyn tc la chn

chng st lan truyn trn ng dy in lc h p v ng dy tn hiu, phi la chn thit b chng st tu theo in p yu cu bo v ca i tng cn bo v v dng xung st yu cu bo v.

- in p yu cu bo v c la chn ph thuc vo loi ng dy v thit b vin thng, theo TCN 68 - 140: 1995 Chng qu p, qu dng bo v ng dy v thit b vin thng.

- Dng xung st yu cu bo v ph thuc vo mc khc nghit ca trng in t do st ti vng chng st (LPZ) ca v tr lp t thit b bo v.

Ghi ch:

- LPZ 0: L vng cha cc i tng khng c che chn, cc trng in t do st gy ra vng ny khng b suy hao. LPZ 0 c chia thnh LPZ 0A v LPZ 0B:

LPZ 0A: Cc i tng trong vng ny chu st nh trc tip v bi vy c th phi chu hon ton dng in st.

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LPZ 0B: Cc i tng trong vng ny khng chu st nh trc tip nhng trng in t do st gy ra khng b yu i.

- LPZ 1: L vng cha cc i tng khng b st nh trc tip. Dng in trong tt c cc thnh phn kim loi trong vng ny c gim i so vi vng LPZ 0. Trng in t trong vng ny c th yu i ph thuc vo cc bin php che chn.

- LPZ 2,...: L cc vng c thit lp khi c yu cu c bit gim nh dng dn cng nh cng trng in t bo v thit b.

LPZ 0A

LPZ 1

LPZ 0B

LPZ 2

Li chn 2 cho phng my

H thngchng st

ct ng ten bn ngoi

Thanh lin kt 1ti ranh gii LPZ 1

v LPZ 0

Cp in lc,vin thng

Thanh lin kt 2ti ranh gii LPZ 1

v LPZ 2

Phng my

Lin kt cc li chn 1 v 2

Li chn 1 cho cng trnh xy dngH thng tip t

Hnh 2.1: Minh ha phn vng chng st LPZ ti trm vin thng

2.2.2 Yu cu k thut

- Thit b chng st trn ng in lc h p v ng dy tn hiu phi c hp chun theo cc yu cu k thut quy nh trong TCN 68 - 167: 1997 Thit b chng qu p, qu dng do nh hng ca st v ng dy ti in - Yu cu k thut.

- Thit b chng st phi c trang b b phn hin th hoc cnh bo trng thi lm vic.

2.3 Cu hnh u ni v tip t trong nh trm vin thng

2.3.1 Quy nh chung

Cu hnh u ni v tip t cho cc h thng thit b ti cc nh trm vin thng, cc nh thu bao, cc trm in t xa phi m bo:

- Nh trm c trang b mt mng lin kt chung (CBN). Mng CBN phi c u ni vi mng tip t ca khu vc nh trm.

- Mng tip t trong khu vc nh trm phi l mt mng tip t duy nht hoc thng nht v ng th.

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- Tng h thng thit b trong nh trm vin thng phi c u ni vi mng CBN qua mt mng lin kt M-BN, M-IBN hoc S-IBN.

2.3.2 Cu hnh u ni v tip t chun cho nh trm vin thng

2.3.2.1 Mng lin kt chung (CBN)

- Nh trm vin thng phi c trang b mt mng lin kt chung (CBN) theo hng dn trong Ph lc A.

- Mng lin kt chung phi c ni ti mng tip t ca nh trm thng qua tm tip t chnh.

- Nh trm vin thng phi c trang b mt tm tip t chnh. Tm tip t chnh phi c t gn ngun cung cp xoay chiu, cc ng vo ca cp vin thng (cng gn cng tt) v phi c cc v tr ring cho kt ni trc tip n cc b phn sau:

+ Mng tip t ca nh trm thng qua ng cp dn t;

+ ng dn bo v (PE);

+ V kim loi ca tt c cp nhp trm;

+ Mng CBN;

+ Cc dng ca ngun 1 chiu;

+ My o (khi thc hin o th).

- Thi cng tm tip t chnh c thc hin nh trong Ph lc D.

2.3.2.2 Mng lin kt BN

- Cc thit b in t trong tng h thng thit b trong nh trm vin thng phi c lin kt vi nhau bng mt mng lin kt BN. Trong mt nh trm c th c nhiu loi cu hnh mng lin kt, tu thuc vo yu cu ca tng h thng thit b. Mng lin kt BN c th l mt trong ba dng sau:

+ Mng lin kt mt li (M-BN);

+ Mng lin kt cch ly mt li (M-IBN);

+ Mng lin kt cch ly hnh sao (S-IBN).

Cc mng lin kt c thc hin theo hng dn trong Ph lc A.

- Mng lin kt mt li (M-BN) c th p dng vi hu ht cc h thng thit b, khi thit b khng c yu cu c bit v vic hn ch dng r t mng CBN chy vo khi h thng thit b v thit b dng ngun mt chiu d.c C.

- Mng lin kt cch ly mt li (M-IBN) c p dng khi c yu cu c bit v hn ch dng r t mng CBN chy vo khi h thng thit b v thit b dng ngun mt chiu d.c C.

- Mng lin kt cch ly hnh sao (S-IBN) c p dng khi c yu cu c bit v hn ch dng r t mng CBN chy vo khi h thng thit b v thit b dng ngun mt chiu d.c I.

2.3.2.3 Cu hnh h thng cung cp ngun in

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a) H thng cung cp ngun xoay chiu:

- Trong nh trm, phi dng loi TN-S (trong nh trm khng c im ni chung dy bo v PE v dy trung tnh N).

- ng cp ngun xoay chiu phi t cch cp tn hiu t nht l 100 mm, tr trng hp c bin php che chn thch hp.

b) H thng cung cp ngun mt chiu

- Dy (+) v (-) ngun mt chiu phi i gn nhau.

- in p mt chiu ri trn mi dy dn v mt chiu phi m bo nh hn 1 V. Gi tr ny c tnh ton vi dng ti ln nht trn dy cp ngun i km trong iu kin lm vic bnh thng.

- Dy (+) ngun mt chiu c ni vi CBN ti nhiu im (ngun d.c C). Trong trng hp c bit, yu cu hn ch dng r t CBN chy vo thit b (thit b nhy cm vi cc t bin trong trng hp ngn mch), dng ngun mt chiu d.c- I (dy (+) ngun mt chiu c ni vi CBN ti duy nht mt im).

2.3.3 Cu hnh tip t chun cho nh thu bao

- Cc nh thu bao ln, c quy m v chng loi thit b nh mt trm vin thng, phi p dng cc quy nh v cu hnh u ni v tip t chun nh trong 2.3.2.

- Nh thu bao c quy m nh hn (s dng trc tip cc dch v vin thng), phi thc hin cu hnh u ni v tip t theo nhng quy nh sau:

a) Trang b mt tm tip t chnh (MET). Tm tip t chnh ny t cng gn li vo ca cp ngun v cp vin thng cng tt;

b) Phi thit lp mng CBN bn trong nh thu bao bng cch lin kt tt c cc phn t kim loi trong nh thu bao vi nhau v vi tm tip t chnh (MET).

c) Phi trang b mt mng tip t (h thng tip t). Mng tip t ny phi tha mn in tr tip t m cc thit b trong nh thu bao yu cu.

d) Dy bo v PE ca h thng ngun phi c ni n tm tip t chnh;

e) Cp ngun xoay chiu v cp vin thng phi cch nhau t nht l 100 mm tr trng hp c che chn hp l;

f) V che chn ca tt c cc cp i vo nh thu bao phi c ni trc tip vi tm tip t chnh;

g) V tr lp t cc thit b chng st trn ng dy thng tin, ngun h p phi c b tr cng vo nh thu bao. di dy t t thit b bo v n MET cng ngn cng tt;

h) Trong mt s trng hp, tu theo yu cu ca thit b u cui vin thng, phi lp t nhng b bo v ph ti thit b u cui vin thng hn ch xung to ra do ghp in t bn trong nh thu bao.

i) Trng hp nhiu nh thu bao c ng cp vin thng dn t mng cng cng vo ln lt tng nh, phi thc hin tip t v bo v cho thit b vin thng t trong mi nh nh trng hp nh c lp.

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Ring trong trng hp cp i bn trong nh khng tip xc vi ng in lc cao p, khong cch gia cc ngi nh nh hn 50 m, cp gia cc nh c mn chn kim loi v cc mn chn ny c ni vi cc tip t ca mi nh th ch lp b bo v nh th nht, khng cn lp b bo v nh th hai.

2.3.4 Cu hnh u ni v tip t trong trm in t xa

- Phi thc hin cu hnh u ni v tip t trong cc trm in t xa theo dng cu trc che chn bo v thit b in t (EEE) hoc dng ca bin thit b in t (EEC).

- Cu trc che chn bo v thit b in t (EEE) hoc ca bin thit b in t (EEC) phi bao gm nhng thnh phn sau:

a) Mng lin kt chung CBN to bi s lin kt tt c nhng thnh phn cu trc kim loi sn c ca nh trm vi ng dn kt ni (vng kt ni) c xy dng b sung;

b) Tm tip t chnh;

c) Dy dn t thc hin ni mng tip t vi tm tip t chnh;

d) Dy dn t bo v v dy dn lin kt.

- Phi thc hin mng lin kt M-BN i vi cc khi h thng thit b v thc hin kt ni gia mng M-BN v CBN theo hng dn trong Ph lc A.

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Chng III

kho st v o c

3.1 Quy nh chung

- Nhim v kho st l phi nm c cc s liu cn thit cho vic thit k chng st. Kho st c tin hnh sau khi c nhim v thit k chng st.

- Ch nhim n thit k chng st phi ph trch nhm kho st v vic kho st phi c s tham gia ca i din c quan qun l cng trnh vin thng cn thit k chng st.

- Ty thuc vo tm quan trng, quy m, kch thc cng trnh cn thit k chng st t chc mt hoc vi nhm kho st.

- Tuyt i bo m an ton lao ng trong cng tc kho st chng st. Khi kho st phi tun th theo cc quy nh v an ton lao ng ca Nh nc v ca Ngnh ban hnh.

- Cng tc kho st chng st c tin hnh i vi cc cng trnh xy dng mi hoc cc cng trnh b st nh hng hoc cng trnh cn ci to nng cp chng st do c nhiu nguy c st nh.

3.2 Nhim v kho st

3.2.1 Ni dung kho st

3.2.1.1 Kho st cng trnh dng tuyn (ng dy thng tin cp kim loi, cp si quang)

Khi kho st cng trnh dng tuyn, cn quan tm:

- c im kh tng (s ngy hoc gi dng) trong nhng vng ng dy i qua;

- c im in tr sut ca t trong nhng vng m ng dy i qua;

- c im lp t (treo hay chn ngm);

- c im ca mi on ng dy i qua cc vng c c im kh tng v a cht khc nhau (chiu di, cao treo cp hoc dy trn, chn su v in tr sut ca t trong mi on...).

3.2.1.2 Cng trnh dng im (nh trm hoc ct ng ten vin thng)

Khi kho st cng trnh dng tuyn, cn quan tm:

- c im kh tng (s ngy hoc gi dng) trong nhng vng cng trnh c xy dng;

- c im in tr sut ca t trong vng;

- c im nh trm vin thng (kch thc, kt cu nh hoc cha lp h thng chng st nh trc tip bo v, cc h thng tip t trong khu vc trm vin thng...);

- c im ca cc cng trnh lin quan khc nh nh my n, trm bin th in AC (kch thc, kt cu nh);

- c im ct ng ten vin thng (kch thc ct, khong cch t ct ng ten n nh trm vin thng, c im cp ng ten phi ...);

- c im cc loi ng dy vo trm (chiu di, cch lp t ca cc ng in li, ng dy thng tin hoc cha lp thit b chng st...);

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- c im cc cng trnh bng kim loi dn vo khu vc trm (cc ng ng nc, ng kh t...);

- c im ca a hnh xung quanh cng trnh cn chng st (cc cng trnh xy dng k bn, ng bng hay trn ni, chnh lch im lp t cng trnh so vi mc trung bnh ca a hnh xung quanh...).

3.2.2 Ni dung bo co kho st

- Bn v s mt bng khu vc trm hoc mt bng tuyn ng dy;

- Cc s liu kho st, o c (c im nh trm vin thng, trm bin th, ct ng ten, my n, ng dy vin thng, ng in li, in tr sut ca t trong khu vc...);

- Cc kh khn cha c gii quyt;

- D kin cc bin php gii quyt...

3.3 o in tr sut ca t

Cc phng php trong thc t xc nh gi tr in tr sut ca t gm c: o thm d in cc tip t mu; o su thm d i xng (phng php 4 in cc).

3.3.1 Xc nh in tr sut ca t theo phng php thm d in cc tip t mu

Phng php thm d in cc tip t mu ch xc nh c gi tr in tr sut ca t n su chn in cc v s dng trong trng hp khng c loi my o 4 in cc tin hnh theo phng php o su thm d i xng. Mch o c quy nh nh trong hnh 3.1.

T kt qu o in tr R ca in cc tip t mu, tnh ra gi tr in tr sut ca t su chn cc bng cng thc:

pr =

ll

2

ln(4 / )

Rd

(3.1)

Trong :

r- in tr sut ca t, W.m;

l- chiu di phn chn su ca in cc tip t mu, m;

d - ng knh ngoi ca in cc tip t mu dng tr trn, m (nu in cc tip t c dng thp gc, vi cnh l b th d = 0,95b).

l

E P C

E P C

D = 0,62D2 1

D > 2,21 l

Hnh 3.1: o in tr sut ca t theo phng php thm d in cc mu

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3.3.2 Xc nh in tr sut ca t theo phng php o su thm d i xng (phng php o in vt l)

3.3.2.1 Phng php Wenner

Mch o theo phng php Wenner c trnh by trn hnh 3.2.

in tr sut ca t c tnh bng cng thc:

r = 2paR, (W.m) (3.2)

Trong :

R - gi tr in tr o c, W;

a - khong cch gia cc in cc, m;

C1 P1 P2 C2

C1 P1 P2 C2

l < a/20

a a a

O

Ghi ch:

- su chn in cc l phi nh hn a - Chn l a/20 v l < 1 m.

Hnh 3.2: o in tr sut ca t theo phng php Wenner

3.3.2.2 Phng php Schlumberger

Mch o theo phng php Schlumberger c trnh by trn hnh 3.3. in tr sut ca t c tnh bng cng thc:

p -r = W

l2 2( ), ( . )

2

R d md

(3.3)

Trong :

l- khong cch t cc in cc dng n tm thm d O, m;

d - khong cch t cc in cc p n tm thm d O, m;

R- gi tr in tr c c trn my o, W;

C1 P1 P2 C2

C1 P1 P2 C2

l

O

dl

d

Hnh 3.3: o in tr sut ca t theo phng php Schlumberger

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Chng IV

Thit k chng st v tip t

4.1 Nguyn tc chung

4.1.1 Vic thit k chng st v tip t c tin hnh sau khi d n kh thi c cc cp c thm quyn ph duyt (d n kh thi, d n u t).

4.1.2 Thit k ch c thc hin sau khi c y vn bn, ti liu, s liu kho st o c thc a.

4.1.3 Thit k chng st v tip t cho nh trm, ct cao ng ten v ng dy thng tin c tin hnh theo trnh t c bn sau:

- Tnh ton tn sut thit hi do st gy ra i vi cng trnh vin thng khi cha c trang b bo v, phng php c nu trong TCN 68 - 135: 2001 Chng st bo v cc cng trnh vin thng - Yu cu k thut;

- So snh vi gii hn tn sut thit hi cho php c quy nh trong TCN 68 - 135: 2001;

- Nu tn sut thit hi vt qu gii hn cho php, phi la chn cc bin php bo v thch hp sao cho tn sut thit hi do st tho mn yu cu trong TCN 68 135: 2001.

4.2 Thit k chng st bo v nh trm vin thng

4.2.1 Chng st nh trc tip cho nh trm vin thng

4.2.1.1 Chn mc bo v

Thit k h thng chng st nh trc tip cho nh trm vin thng phi m bo sao cho hiu qu bo v ca h thng p ng c yu cu bo v ca nh trm. Hiu qu bo v E ca h thng chng st c xc nh nh sau:

E 1 Fd/ Fd; (4.1)

Trong :

Fd - tn sut thit hi do st nh trc tip ln nh trm vin thng;

Fd - tn sut thit hi do st nh trc tip c th chp nhn c.

Ch : Cc gi tr Fd, Fd c xc nh theo TCN 68 135: 2001.

Bng 4.1: Mc bo v ca h thng chng st tng ng vi hiu qu bo v

Mc bo v Hiu qu bo v E

I II III IV

0,98 0,95 0,90 0,80

4.2.1.2 Thit k h thng chng st nh trc tip

H thng chng st nh trc tip phi c thit k m bo hiu qu bo v la chn theo 4.2.1.1.

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Vic thit k h thng chng st nh trc tip phi m bo cc yu cu c quy nh trong mc 2.1, tu theo loi h thng chng st c la chn.

4.2.2 Chng st lan truyn t bn ngoi nh trm

4.2.2.1 Chng st lan truyn t ng dy thng tin i vo nh trm

a) La chn loi cp c v che chn vi tr khng truyn t nh.

b) Thc hin tip t v lin kt ng th cho v cp theo quy nh trong Tiu chun Ngnh TCN 68 141: 1999 Tip t cho cc cng trnh vin thng Yu cu k thut. Cp ng trc dn t ng ten xung phi c t trong lng ct thp v tip t v tr t ct thp sang cu cp v v tr i vo nh trm.

c) Lp t thit b chng st ti v tr cp i vo nh trm. Thit b bo v phi c la chn theo quy nh trong mc 2.2.1 v phi hp tt vi kh nng chu ng ca thit b cn bo v.

4.2.2.2 Chng st lan truyn t ng dy in lc i vo nh trm

a) La chn loi cp c v che chn vi tr khng truyn t nh.

b) Thc hin tip t v lin kt ng th cho v cp theo quy nh trong Tiu chun Ngnh TCN 68 141: 1999.

c) Lp t thit b chng st ti v tr cp i vo nh trm. Thit b bo v phi c la chn theo quy nh trong mc 2.2.1 v phi hp tt vi kh nng chu ng ca thit b.

d) Dng my bin th h p ring cung cp ngun in cho nh trm. Trong trng hp ny, phi lp t thit b chng st trn ng dy trung v cao p trc khi vo trm bin th. Thit b chng st c la chn phi hp tt vi kh nng chu ng ca ng dy v chu c dng xung st xut hin ti v tr lp t.

4.2.3 Chng st lan truyn v cm ng in t bn trong nh trm

a) Thc hin lin kt ng th ti ranh gii gia cc vng chng st (LPZ) i vi cc thnh phn v h thng kim loi (cc ng ng dn kim loi, cc khung gi cp, khung gi thit b).

b) Thc hin cc bin php che chn in t:

- Lin kt cc thnh phn kim loi ca to nh vi nhau v vi h thng chng st nh trc tip, v d mi nh, b mt bng kim loi, ct thp v cc khung ca bng kim loi ca ta nh.

- Dng cc loi cp c mn chn kim loi hoc dn cp trong ng kim loi c tr khng thp. V che chn hoc ng dn bng kim loi phi c lin kt ng th hai u v ti

ranh gii gia cc vng chng st (LPZ). ng dn cp phi c chia lm hai phn bng vch ngn bng kim loi, mt phn cha cp thng tin, mt phn cha cp in lc v cc dy dn lin kt.

c) Lp t cc thit b chng st ti giao din dy - my (ti ranh gii LPZ1 v LPZ2). Thit b chng st c la chn phi hp tt vi kh nng chu ng ca thit b cn bo v v chu c dng xung st xut hin ti v tr lp t.

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d) Thc hin cu hnh u ni v tip t trong nh trm vin thng theo quy nh trong mc 2.3.

4.3 Thit k chng st bo v ct ng ten vin thng

gim nh tn sut thit hi do st gy ra i vi ct ng ten vin thng, phi trang b h thng chng st nh trc tip cho ct ng ten. Thit k chng st nh trc tip cho ct ng ten c p dng theo mc 4.2.3.

Ch :

- Vi ct cao ng ten bng kim loi, khng cn trang b dy thot st m dng thn ct thc hin chc nng ny, vi iu kin phi hn ni v mt in kh cc t ct vi nhau qua tt c cc mt bch ct.

- Cc thnh phn kim loi ca ct ng ten vin thng phi c lin kt in lin tc vi nhau v vi cc thnh phn v kim loi ca thit b k thut.

4.4 Thit k chng st bo v ng dy thng tin

4.4.1 La chn mi trng lp t

Khi thit k tuyn cp, phi ch xem xt, la chn mi trng lp t sao cho c th li dng c yu t che chn sn c ca mi trng xung quanh.

4.4.2 La chn cp c gi tr dng gy h hng ln

i vi cp nm trong vng nguy him v hay b st nh, phi la chn cp c gi tr dng gy h hng ln gim tn sut gy thit hi.

4.4.3 Thc hin tip t cho tuyn cp

- Phi thc hin tip t mn chn kim loi ca cp treo ti hai u tuyn cp v dc theo tuyn cp theo quy nh trong TCN 68-141: 1999 Tip t cho cc cng trnh vin thng.

- C th tng s ln tip t dy treo cp (gim nh khong cch gia cc im tip t) nhng vng hay b st nh.

4.4.4 Trang b dy chng st ngm cho cp chn

gim nh dng st nh vo cp chn, dng dy chng st ngm bng kim loi chn pha trn, dc theo tuyn cp thu ht mt phn dng st (xem ph lc F). Dy chng st ngm phi bng ng hay lng kim c ng knh khng nh hn 4 mm, hoc nhiu si dy thp m km c tng tit din khng nh hn 38 mm2. Dy chng st ngm phi c b tr dc theo ton b chiu di on cp cn c bo v v ko di thm mt on Y, vi Y c tnh bng cng thc:

Y 5 . (r)1/2, (m) (4.2)

Trong :

r = in tr sut ca t, W.m.

4.4.5 Lp t thit b chng st

Lp t thit b chng st ti cc im cp nhp trm lm gim tn sut thit hi cho cp do st nh trc tip vo trm. Thit b chng st phi c la chn phi hp tt vi kh

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nng chu ng ca cp. Thit b chng st phi c ni gia cc dy dn kim loi ca cp vi thanh tip t chnh ca nh trm. Ti di cp chn Lp = 5.r1/2 (vi r l in tr sut ca t, W.m) tnh t nh trm, phi lp thm cc thit b chng st gia cc dy dn kim loi ca cp v v cp (hoc ng kim loi).

4.5 Thit k h thng tip t

4.5.1 Nguyn tc thit k

- Tt nht, nn dng mt h thng tip t dng chung cho cc chc nng tip t chng st, tip t cng tc v bo v trong mt khu vc nh trm vin thng.

- Trong trng hp c sn h thng tip t chng st cho nh trm, khi thit k h thng tip t cng tc v bo v cho thit b, phi thc hin lin kt ng th hai h thng tip t trn.

- H thng tip t dng chung phi c gi tr in tr nh hn gi tr in tr tip t tiu chun thp nht.

- H thng tip t chung phi c thi cng v tr thch hp nht (trung tm) sao cho chiu di cp dn t l ngn nht.

- Phi lin kt ng th gia h thng tip t ca khu vc nh trm vi h thng tip t chng st ca ct cao ng ten k bn.

4.5.2 Xc nh in tr sut ca t

- Trc khi thit k cc h thng tip t, phi o in tr sut ca t ti khu vc d kin trang b tip t. Phng php o v s mch o c quy nh trong mc 3.3, chng III.

- in tr sut ca t dng trong tnh ton h thng tip t c xc nh bng cng thc:

rtt = k ro, (W.m) (4.3)

Trong :

rtt - in tr sut ca t dng trong thit k chng st;

ro - in tr sut ca t o c;

k - h s ma, k =1,6 1,8.

4.5.3 Chn vt liu lm in cc tip t

Vt liu lm in cc tip t s lm nh hng n tui th ca h thng tip t. V vy, vic chn vt liu lm in cc tip t ph thuc vo chc nng ca h thng tip t.

1) H thng tip t cng tc:

H thng tip t cng tc c thi hn khai thc l 15 nm. Vt liu lm in cc tip t cng tc phi bng ng hoc bng thp m km.

Phng php tnh ton c nu trong Ph lc C.

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26

2) H thng tip t bo v c thi hn khai thc l 30 nm. in cc tip t ch cn lm bng thp m km.

3) H thng tip t dng chung cho cc chc nng tip t cng tc v tip t bo v phi c xem xt nh i vi h thng tip t cng tc.

4.5.4 La chn loi h thng tip t

Vic la chn loi h thng tip t ph thuc vo 3 iu kin sau:

- iu kin mt bng ni s thi cng h thng tip t;

- in tr sut ca t ti ni thi cng;

- Gi tr in tr tip t tiu chun.

H thng tip t thng c xy dng theo cc loi sau:

1) H thng tip t dng hn hp (gm cc in cc thng ng v cc di nm ngang)

H thng tip t dng hn hp c s dng trong nhng iu kin sau:

- Gi tr in tr sut ca t ti ni thi cng h thng tip t khng ln hn 100 W.m v tng i ng nht su t 1 n 5 m;

- Mt bng thi cng khng b hn ch;

- in tr tip t tiu chun yu cu nh (thng thng l h thng tip t cng tc).

2) H thng tip t l nhng di st hoc ng nm ngang

H thng tip t l nhng di st hoc ng nm ngang c s dng trong nhng iu kin sau:


- Gi tr in tr tip t tiu chun yu cu ln t 5 n 10 W (thng thng c dng i vi cc h thng tip t bo v c lp xa trung tm);

- Mt bng thi cng khng b hn ch.

3) H thng tip t chn su

H thng tip t chn su c s dng trong nhng iu kin sau:

- Gi tr in tr sut ca t ti ni thi cng rt nh cc lp t di su;

- Gi tr in tr tip t tiu chun yu cu nh (thng thng l h thng tip t cng tc);

- Mt bng thi cng cht hp.

4) H thng tip t bao gm nhng tm thp hoc ng chn dng ng

H thng tip t bao gm nhng tm thp hoc ng chn dng ng c s dng trong nhng iu kin sau:


- Mt bng thi cng qu cht hp;

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- Gi tr in tr tip t tiu chun yu cu trong phm vi t 3 n 5 W.

4.5.5 Tnh ton h thng tip t

Cc h thng tip t phi c tnh ton, thit k m bo thi hn khai thc nh sau:

1) H thng tip t bo v: 30 nm;

2) H thng tip t cng tc: 15 nm.

Cc cng thc tnh ton h thng tip t c nu trong Ph lc C.

4.5.6 S dng ho cht ci to t

Tu theo yu cu thc t, c th s dng cc loi ha cht ci to t nh sau:

1) Dng ho cht ci to t dng ho tan nhm mc ch gim nh in tr sut ca t.

2) Dng ho cht ci to t dng ng cng nhm mc ch:

- Gim nh in tr tip t;

- Tng n nh ca in tr tip t;

- Chng n mn cho cc in cc tip t;

- Tng kh nng tip xc vi t trong trng hp dng in cc tip t chn su.

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Chng V

Thi cng lp t trang thit b chng st v h thng tip t

5.1 Nguyn tc chung

- Tt c cc trang thit b chng st v tip t, trc khi lp t phi c kim nh theo ng n thit k c ph chun.

- n v thi cng phi thc hin thi cng theo ng thit k v khng c t sa cha thit k v bn thi cng.

- Vic thi cng lp t cc h thng chng st v tip t khng c gy nh hng, lm gin on thng tin lin lc.

- Trong qu trnh thi cng, n v thi cng phi tuyt i tun th cc quy nh v an ton in v an ton lao ng ca nh nc, ca ngnh v ca n v thi cng ra. Khi c dng st, nguy him, tuyt i khng c php thi cng.

5.2 Thi cng lp t h thng chng st nh trc tip

- in cc thu st v dy thot st phi c lp t theo ng cng ngn cng tt.

- Tt c cc thnh phn trong h thng chng st nh trc tip phi c lp t m bo chc chn v mt c kh chu c cc tc ng do gi, cc iu kin thi tit v cc tc ng c hc khc.

- Dy thot st phi c gn cht vo tng v c lp t ni an ton, trnh gy nguy him cho con ngi.

- Dy thot st trong h thng chng st nh trc tip bo v ct cao ng ten phi c lp t trong lng ct thp v c c nh chc chn vo thn thp.

- Cc h thng chng st pht tin o sm v phn tn nng lng st phi c lp t theo ng quy nh ca nh sn xut.

5.3 Lp t thit b chng st lan truyn

- Nu ng dy in h p vo nh trm vin thng qua nh my n, phi lp t thit b bo v s cp ngay ti nh my n hoc trm bin th. Nh my n phi c trang b tip t ni t cho my n, bin th v thit b chng st.

- Thit b chng st c lp t ti nh trm vin thng phi t trc t phn phi in chnh AC.

- Lp t thit b chng st trn ng dy tn hiu ti v tr ng dy i vo nh trm v ti giao din gia ng dy v thit b ng theo thit k.

- Vic thc hin lp t chi tit cn tun th hng dn ca nh sn xut thit b.

- Khi ct in li thi cng lp t thit b chng st, phi c cc bin php thch hp nh s dng in my n, c quy khng lm gin on thng tin lin lc.

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5.4 Thi cng lp t chng st bo v ng dy thng tin

5.4.1 Cp quang c thnh phn kim loi

- Vi tuyn cp quang c thnh phn kim loi, phi m bo tnh lin tc ca thnh phn kim loi theo chiu di ca cp, k c cc ch ni v cc b ti to. Phi ni cc thnh phn kim loi vi thanh lin kt cn bng th (e.p.b.b) (ni trc tip hoc qua thit b chng st) ti hai u tuyn cp. Nu khng c thanh lin kt cn bng th, phi ni cc thnh phn kim loi ny vi thanh lin kt cn bng th dng ring bn trong kt cui mng quang.

e.p.b.b

Mt bch hoc hp niCp lin tc

Mng ngn mPhn t chu lc i dy ng

ng cch ly

Nh

Hnh 5.1: Ni cc phn t bng kim loi trong cp si quang

Khi thc hin tip t dy treo cp hoc dy t treo cp, dy ni t phi c t trong ng nha bo v v c buc c nh, chc chn vo thn ct. Ch thc hin tip t v bc kim loi ti cc hp cp.

- Khng thc hin tip t cho v kim loi ca cp quang ngm c lp v bc cch in.

- Khng lp t cp quang vi cp in lc trong cng mt ng.

- Khi lp t dy chng st ngm, phi bo m tnh dn in lin tc dc theo chiu di dy chng st ngm.

- Lp t thit b chng st ti cc im cp vo nh trm theo yu cu thit k v hng dn lp t chi tit ca nh sn xut thit b.

5.4.2 Cp kim loi

- Khi lp t, phi ch duy tr tnh lin tc cc thnh phn kim loi (mn chn in t, dy treo cp, cc thnh phn gia cng...) ti cc mi ni, b cp, t cp v hp cp dc tuyn. Phi ni cc thnh phn kim loi ca cp (ni trc tip hoc qua thit b chng st) vi thanh lin kt cn bng th ca nh trm ti hai u tuyn cp.

- Khi thc hin tip t dy treo cp hoc dy t treo cp, dy ni t phi c t trong ng nha bo v v c buc c nh, chc chn vo thn ct. Ch thc hin tip t v bc kim loi ti cc hp cp.

- Ch thc hin tip t v cp ngm ti cc hp cp.

- Khi lp t dy chng st ngm, phi bo m tnh dn in lin tc dc theo chiu di dy chng st ngm.

- Lp t thit b chng st ti cc im cp vo nh trm theo yu cu thit k v hng dn lp t chi tit ca nh sn xut thit b.

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5.5 Thi cng h thng tip t

5.5.1 Thi cng h thng tip t

n v thi cng h thng tip t phi thc hin thi cng theo ng thit k v theo trnh t c trnh by chi tit trong Ph lc D.

5.5.2 Thc hin lin kt cc h thng tip t

Khi c nhiu h thng tip t dng cho cc chc nng khc nhau, phi thc hin lin kt cc h thng tip t c chc nng khc nhau trong mt khu vc nh trm vi nhau m bo s cn bng in th bng cc phng php sau:

5.5.2.1 Phng php 1: Thc hin lin kt bng li san bng in th

Li san bng in th l li kim loi chn di t. Din tch mt bng thi cng li san bng in th ty thuc vo a hnh ca cc h thng tip t nhng phi m bo li san bng in th cch cc h thng tip t khng ln hn 5 m.

Ch : Nn thc hin thi cng li san bng in th cng thi im thi cng cc h thng tip t.

Li thi cng c thc hin theo trnh t sau:

- o t trn din tch mt bng cn thit vi su t 0,5 n 0,7 m;

- Trn mt bng ( c o t), t dy ng hay dy thp m km c ng knh t 3 mm n 5 mm hoc nhng di ng hay nhng di st c kch thc 15 mm x 1 mm hay 10 mm x 2 mm to thnh hnh li c kch thc 30 cm x 30 cm hoc 50 cm x 50 cm;

- Phi hn tt c cc mt li to thnh 1 li dn in lin tc;

- Thc hin lin kt (hn ni) li san bng vi cc h thng tip t ti nhng v tr thch hp (dy dn l ngn nht, khng ln hn 5 m) bng dy ng trn vi tit din ln hn hoc bng 14 mm2;

- Lp t nn cht.

5.5.2.2 Phng php 2: Lin kt bng phng php ni trc tip

Cc h thng tip t c lin kt vi nhau bng cp ng hoc thanh ng trn c tit din ln hn hoc bng 50 mm2 chn su di mt t khong t 0,5 n 0,7 m.

Trong trng hp dng cp ng nhiu si, ng knh mt si khng nh hn 1 mm.

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Chng VI

Kim tra, nghim thu cc h thng tip t v chng st

6.1 Thnh phn nghim thu

Ch u t ra quyt nh thnh lp Hi ng (Ban) nghim thu. Thnh phn tham gia nghim thu phi c i din cc bn nh sau:

1. i din ch u t;

2. i din thit k;

3. i din thi cng;

4. i din qun l khai thc cng trnh vin thng.

Hi ng (Ban) nghim thu c nhim v lp bin ban nghim thu. Bin bn phi c xc nhn ca cc i din ni trn.

6.2 Nghim thu cc h thng, thit b chng st

6.2.1 Ni dung nghim thu

Thc hin nghim thu theo cc ni dung sau:

1. Nghim thu theo thit k k thut thi cng;

2. Nghim thu v c hc. H thng phi c lp t chc chn;

3. Nghim thu v thm m. H thng lp t phi m bo m quan;

4. Nghim thu v an ton cho con ngi. H thng c lp t phi bo m an ton cho con ngi khi lm vic gn;

5. o gi tr in tr tip t ca h thng hay thit b chng st (khi dng ring h thng tip t). So snh gi tr in tr tip t o c vi tiu chun thit k yu cu;

6. Xem xt h s kim nh cc thit b chng st trc khi lp t.

6.2.2 H s nghim thu

H s nghim thu cc h thng, thit b chng st gm c:

1. Cc h s thit k;

2. Bin bn o kim c tnh k thut ca cc h thng, thit b chng st trc khi lp t;

3. Bin bn nghim thu cc h thng chng st nh trc tip, nghim thu lp t thit b chng st trn cc ng dy thng tin v trn cc ng in li;

4. Cc h s cung cp thit b;

5. L lch xc nhn ngun gc ca h thng hay thit b chng st c lp t;

6. Bin bn bn giao thit b chng st.

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6.3 Kim tra, nghim thu h thng tip t

6.3.1 Quy nh v th tc nghim thu:

1) Nghim thu lp t h thng tip t phi l hng mc c nghim thu u tin ca ton b cng trnh vin thng c xy dng.

2) Kim tra, nghim thu h thng tip t phi thc hin theo hai giai on:

a) Giai on 1: Kim tra, nghim thu cc b phn chn di t (phi nghim thu trc khi lp kn t);

b) Giai on 2: Kim tra, nghim thu ton b h thng tip t.

6.3.2 Quy nh v ni dung kim tra, nghim thu h thng tip t

Kim tra, nghim thu h thng tip t gm c:

1) Kim tra vic thi cng dn tip t (phn chn di t).

a) Kim tra chung vic lp t so vi thit k;

b) Kim tra s ph hp vic s dng vt liu, kch thc ca cc in cc tip t vi thit k;

c) Kim tra bn c hc v dn in ca cc mi hn, mi ni;

d) Kim tra vic lp t cho cc in cc tip t.

Kt qu kim tra c a vo bin bn theo mu quy nh trong ph lc D.

2) o th nghim thu ton b h thng tip t.

Sau khi kt thc bc thi cng cp dn t s tin hnh nghim thu h thng tip t. o in tr tip t ti tm tip t chnh. Phng php o v mu ghi bin bn c trnh by Ph lc D.

6.3.3 H s nghim thu lp t cc h thng tip t

1) H s v thit k;

1. Vn bn ngh thay i thit k (nu c) hoc ngh thay i vt liu xy dng dng cho h thng tip t (nu c) c cc bn ch u t, thit k tho thun;

2. Cc bin bn kt qu o lng kim tra ca h thng tip t c hai giai on;

3. Cc vn bn nh gi ca Hi ng (Ban) nghim thu cc b phn chn di t v ton b h thng tip t;

4. S hon cng h thng tip t (ghi r v tr h thng tip t v s cp dn t).

6.3.4 Kt lun, bn giao

Sau khi kim tra o th, Hi ng (Ban) nghim thu phi c kt lun nh gi trn c s so snh vi tiu chun.

Nu cha t, Hi ng (Ban) nghim thu phi xc nh trch nhim thuc v n v thi cng hay n v thit k. Ch u t yu cu n v chu trch nhim tip tc b sung hay sa cha h thng tip t v phi quy nh thi hn hon thnh. Sau khi b sung, sa cha xong phi kim tra nghim thu li.

Ton b h s nghim thu phi bn giao cho n v qun l.

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Chng VII

Quy nh v qun l v bo dng

7.1 Trong qu trnh qun l v khai thc h thng tip t v chng st, phi thc hin kim tra, bo dng cc trang, thit b theo nhng quy nh sau:

1. Kim tra nh k

2. Kim tra t xut

3. Trong 1 nm u sau khi xy dng cng trnh, cn thng xuyn theo di ni t h thng tip t sau cc trn ma ln, nu thy ln phi lp thm t ngay.

4. Vic bo dng, sa cha phi c thc hin tng phn, sao cho m bo thng tin lin lc 24/24 gi trong ngy.

7.2 Quy nh v thi gian kim tra nh k

1. Mt thng mt ln kim tra cc mi ni, lin kt. Sit cht li c vt ni dy dn ti tm tip t chnh v tm tip t ca tng tng, tm tip t ca gi my, gi phi tuyn...

2. Su thng mt ln phi o kim tra cc t tip t.

3. Su thng mt ln phi kim tra cu hnh u ni v tip t bn trong nh trm.

4. Su thng mt ln phi kim tra h thng chng st trc tip (c phn thu st v dn st).

5. Su thng mt ln phi kim tra cc thit b bo v chng st lp t trn ng dy thng tin v ng in li.

6. Kim tra nh k c thc hin vo thi im lu lng thng tin thp nht.

7. Khi thc hin kim tra nh k, khng thc hin vo thi im c ma, dng.

7.3 Quy nh v thi gian kim tra t xut

Kim tra t xut khi c nhng s kin sau y:

- Sau khi b st nh;

- Sau cc trn bo;

- Sau khi sa cha cng trnh hoc thay i thit b;

- Khi c s thay i lin quan n mt bng c h thng tip t (o bi, lp t ng ng, trng cy, trng ct, lm nh...).

7.4 Ni dung kim tra nh k v t xut

- Kim tra gi tr in tr tip t tiu chun ti tm tip t chnh.

- Kim tra cc mi hn, mi ni ca cp (dy) dn t v cc dy dn lin kt thc hin tip t.

- Kim tra ton b thit b chng st.

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- Kim tra ton b h thng chng st nh trc tip.

- Kim tra cc chi tit c nh thit b chng st, lp t ng dy thng tin v ng in li.

- Kim tra trng thi lm vic ca cc thit b bo v chng st thng qua h thng n hin th.

- Kim tra cc mi ni ca mng lin kt vi mng lin kt chung.

7.5 Sau khi kim tra nu pht hin ch h hng phi sa cha ngay:

- i vi h thng tip t: Nu tr s in tr tip t ln hn so vi tiu chun phi c bin php x l;

- Vic kim tra v sa cha nh k phi kt thc trc ma dng st ca a phng.

7.6 Mi ni dung kim tra sa cha nh k hoc t xut u phi ghi vo l lch k thut v lu h s

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Ph lc A Cu hnh u ni v tip t trong cc nh trm vin thng

A.1 Cu hnh u ni v tip t trong nh trm vin thng

Cu hnh u ni v tip t trong cc nh trm vin thng c thc hin theo trnh t sau:

1. Xy dng mng lin kt chung (CBN) cho nh trm vin thng.

2. Thc hin u ni mng lin kt chung (CBN) vi mng tip t ca khu vc nh trm.

3. Xy dng mng lin kt cho cc khi h thng thit b trong nh trm vin thng, ng thi thc hin u ni cc mng lin kt vi mng lin kt chung (CBN).

A.1.1 Xy dng mng lin kt chung cho nh trm vin thng

A.1.1.1 Trnh t xy dng mng lin kt chung (CBN)

Mng lin kt chung ca nh trm vin thng c dng tng qut nh trong s hnh A.1.

1. Trnh t xy dng mng CBN i vi nh trm vin thng xy dng mi hon ton

a) Xy dng ng dn kt ni:

- Ti mi tng ca nh trm vin thng xy dng mt vng kt ni khp kn quanh sn nh ( su t 0,5 n 0,7 m di nn nh), hoc thc hin vng kt ni khp kn xung quanh tng nh. Vng kt ni c thc hin bng cp ng hoc nhng di ng hay thp m km c tit din ti thiu khng nh hn 100 mm2.

- Thc hin lin kt cc vng kt ni ca mi tng bng cc dy lin kt thng ng ta nh mt lng Faraday, khong cch gia cc dy thng ng khng ln hn 5 m. Dy lin kt thng ng l thanh ng hoc thp m c thit din khng nh hn 100 mm2.

- Xy dng tm li trn ton b nn nh trm su t 0,5 n 0,7 m bng nhng di thp m km hoc ng tit din ln hn 14 mm2, vi kch thc mt li 30 cm x 30 cm hoc 50 cm x 50 cm (phi thc hin hn tt c cc im giao nhau ca li).

- Thc hin hn ni tm li vi vng kt ni xung quanh sn nh hoc xung quanh tng.

b) Thc hin lin kt khung b tng ct thp ca kt cu nh trm.

- Trong trng hp s dng khung b tng ct thp lm dy dn st, phi thc hin hn ton b khung b tng ct thp ca kt cu nh trm ti cc im ni v giao nhau.

c) Thc hin u ni ng dn kt ni vi cc thnh phn kim loi trong nh trm:

- Vi dy dn st ca nh trm (nu c);

- Vi ton b khung b tng ct thp ca kt cu nh trm;

- Vi khung gi cp nhp trm;

- Vi cc ng dn nc, cc ng dn cp bng kim loi.

2. Trnh t xy dng mng CBN i vi nh trm vin thng c sn

a) Xy dng ng dn kt ni:

- Ti mi tng ca nh trm vin thng xy dng mt vng kt ni khp kn xung quanh tng nh. Vng kt ni c thc hin bng cp ng hoc nhng thanh ng, hay thp m km c tit din ti thiu khng nh hn 100 mm2.

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b) Thc hin u ni vng kt ni vi cc thnh phn kim loi trong nh trm:

- Vi tt c cc dy dn st ca nh trm v tng phn khung b tng ct thp v mt s dm b tng c th thm nhp c;

- Vi khung gi cp nhp trm;

- Vi cc ng dn nc, cc ng dn cp bng kim loi.

A.1.1.2 Mt s quy nh km theo khi xy dng mng CBN

1) Tt c cc ng cp i vo trm (nhp trm) phi t gn nhau:

- ng vo cp dn in xoay chiu ca cc thit b;

- ng vo cp vin thng ca cc thit b;

- ng vo ca cp dn t.

2) Khi thc hin ko cp ngoi vi nh trm phi bao bc cp bng ng dn kim loi hoc ng nha c tui th cao 50 nm (cp c lun trong ng kim loi hoc ng nha).

3) Trong cc nh trm cao tng c khung thp phi ch nhng im sau:

- Cp ko gia cc tng phi t gn trung tm ca nh trm;

- Nu cp c bao bc bng ng dn kim loi c th t bt k v tr no.

4) Nu thit b vin thng c trang b thit b bo v qu p s cp trn cc ng dy vin thng, thit b bo v phi c ni ti v cp v vi mng CBN xung quanh.

5) Nu ti li vo ca ng in xoay chiu c t cc thit b bo v chng qu p, nhng thit b bo v ny phi c ni ti mng CBN.

6) Mng lin kt CBN phi cung cp 1 ng dn vi tr khng thp song song hoc gn vi v cp hay cc dy dn bn ngoi ca cp ng trc.

7) H thng cp trong nh trm phi b tr theo tuyn ngn nht v phi t st mng CBN v v cp c lin kt trc tip vi mng CBN.

8) Cc h thng thit b phi c c nh cht vo sn hoc tng gim in dung k sinh.

A.1.2 Thc hin u ni mng lin kt chung vi mng tip t ca nh trm vin thng.

A.1.2.1 Thc hin u ni mng CBN vi mng tip t ca nh trm thng qua tm tip t chnh. Gia mng CBN v tm tip t chnh cng nhiu ng lin kt cng tt.

Trng hp mng tip t ca nh trm vin thng ngay di sn nh hoc xung quanh nh trm, phi thc hin ni mng CBN vi mng tip t thng qua tm tip t chnh bng nhng di ng hoc thp m km c tit din t 50 mm2 n 100 mm2.

A.1.2.2 Quy nh i vi tm tip t chnh

1) Mi nh trm vin thng c trang b mt tm tip t chnh

- Tm tip t chnh phi c t gn ngun cung cp xoay chiu v cc ng vo ca cp vin thng (cng gn cng tt).

2) Tm tip t chnh c ni trc tip n cc b phn sau:

- Mng tip t ca nh trm thng qua ng cp dn t;

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- ng dn bo v (PE);

- V bo v (v kim loi) ca tt c cp nhp trm;

- Mng CBN;

- Cc dng ca ngun 1 chiu.

3) Thi cng tm tip t chnh c thc hin nh mc 2.7 trong Ph lc D.

A.1.3 Xy dng mng lin kt cho cc khi thit b trong nh trm vin thng v thc hin u ni vi mng CBN

A.1.3.1. Xy dng mng lin kt mt li (M- BN)

1) Trnh t xy dng mng M-BN

a) Xy dng tm m mt li

- Tm m mt li c tin hnh xy dng theo yu cu ca cc nh thit k v qun l khai thc thit b. Tm m mt li c kch thc ln cha ng c cc thit b v gi cp nm trong khi h thng M-BN.

Vng kt ni

Cc dy lin kt

Khung b tng ct thp

B tng mng

Tm tip t chnh

Mng tip t

Hnh A.1: Mng lin kt chung

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- Tm m c lm bng dy (di) ng trn hoc bng dy (di) thp m km c tit din ln hn 14 mm2 hn thnh li t di sn t thit b.

- Kch thc mt li thng nm trong phm vi:

20 cm x 20 cm,

30 cm x 30 cm,

40 cm x 40 cm,

50 cm x 50 cm.

b) Thc hin ni (hn) tm m mt li vi mng CBN ti nhiu im (cng nhiu im ni vi mng CBN cng tt) bng di ng trn hoc thp m km c tit din ln hn 14 mm2.

c) Thc hin ni phn dn ca khi h thng thit b vin thng vi tm m mt li.

- Thit b vin thng vi nhng mch in t c cung cp chung mt lp bc kim loi c gi l in th chun ph khp trn b mt cc bng mch in.

- Tt c cc b mt in th chun c ni vi nhau ng thi c ni vi khung gi thit b hoc vi v kim loi cp ca h thng cp ln cn (nm trong khi M-BN) bng nhng dy ng c tit din ln hn 14 mm2.

- Thc hin ni cc ca bin, cc khung gi thit b, v kim loi cp vi tm m mt li bng dy (di) ng theo ng ngn nht c kch thc nh trong bng A.1 (cng nhiu ng ni cng tt).

Bng A.1: Quy nh kch thc ca dy dn lin kt

TT Tn dy dn lin kt Tit din

ti thiu (mm2)

1 2 3

4

5 6 7 8 9 10

Dy n lin kt v kim loi ca cp thu bao (chn) Dy dn lin kt cho v kim loi ca cp thu bao (treo) Dy dn lin kt cho cc b bo v thu bao trn gi phi tuyn MDF Dy dn lin kt cho thit b bo v ngun 220V (thit b bo v s cp) Dy dn lin kt cho ngun c quy Dy dn lin kt cho phn kim loi khung gi b nn Dy dn lin kt cho phn khung gi b i in Dy dn lin kt cho cc phn kim loi khung gi tng i Dy dn lin kt cho cc phn kim loi khung gi phi tuyn Dy dn lin kt cho cc gi cp

14 14

14

100 (L> 50 m) 14

100300 14 14 14 14

TCN 68 - 174: 2006

39

Hnh A.2: Mng M-BN trong nh trm vin thng

L1 L2 L3 N PE

PE

Ct ta nh

Ct thp Vng lin kt

Khi h thng Thit b M-BN (1)

Sn

Ni

Li lin kt

Ct thp

Thit b M-BN

Phn phi in AC

iu ha

ng ng

Panel cp ngun 48V DC

Khung thit b

ngun DC

Dy dn v DC PE Cc tip t chnh

Vng lin kt

n ct thp mng/vng lin kt

n in cc tip t

Cp thng tin

Tng hm

Tng 1

Tng n

Tng n+1

Ni v cp vi khung gi

Dy +48V DC

Ct thp lin kt

Cp ni b

Cp trong h thng c che chn

Dy dn lin kt

Khi h thng thit b M-BN (2)

TCN 68 - 174: 2006

40

A.1.3.2 Xy dng mng lin kt cch ly mt li (M-IBN)

Mng lin kt cch ly mt li (M-IBN) trong nh trm vin thng c m t trong s hnh A.3.

1) iu kin thc hin mng lin kt cch ly mt li

- Cc khi h thng thit b vin thng trong nh trm vin thng c thc hin ni vi mng lin kt chung (CBN) bng mng lin kt cch ly mt li khi chng c nhng yu cu sau:

+ Yu cu che chn cao;

+ Dng r 1 chiu, xoay chiu... trong CBN khng c chy vo khi h thng thit b vin thng.

- Khng thc hin mng lin kt cch ly mt li (M-IBN) i vi khi h thng thit b khng phi l thit b vin thng nh: Thit b ngun, iu ha khng kh, nh sng...

2) Trnh t xy dng mng lin kt cch ly mt li:

Thc hin mng lin kt cch ly mt li theo trnh t sau:

a) Xy dng tm m mt li cch ly hon ton vi CBN xung quanh. Tm m c kch thc ln cha ng c cc thit b v cc gi cp nm trong khi h thng M-IBN.

- Tm li m c lm bng dy (di) ng hoc bng nhng dy (di) st m km c tit din phi ln hn 14 mm2.

- Cc mt li phi hn vi nhau.

- Kch thc mt li cng nh cng tt, trong phm vi:

- 20 cm x 20 cm ; 30 cm x 30 cm ; 40 cm x 40 cm ; 50 cm x 50 cm.

b) Thc hin ni khung gi cp, khung gi thit b vi tm m mt li.

Cc khung gi cp, cc khung v gi ca thit b nm trong khi h thng M-IBN phi c ni vi tm m mt li ti nhiu im bng dy dn lin kt c kch thc nh trong bng A.1.

c) Thc hin u ni mng lin kt cch ly mt li (M-IBN) vi mng lin kt chung (CBN).

- Thc hin u ni mng M-IBN vi mng CBN phi c thc hin trong phm vi im ni n (SPC).

- im ni n (SPC) phi t vng ln cn ca khi h thng M-IBN.

- im ni n trong trng hp ny l di ng dc theo cnh ca tm m mt li c kch thc 2000 mm x 20 mm x 2 mm. Di ng c hn vi cnh tm m mt li.

- Thc hin ni cc ng kt ni ca mng CBN ti SPC bng dy ng c tit din ln hn 14 mm2.

3) Mt s quy nh km theo khi xy dng mng lin kt cch ly mt li

a) Nu cp i t CBN vo M-IBN l cp c v bc kim loi hoc l ng dn cp bng kim loi th phi ni mi u v bc cp hoc ng dn vi khung thit b v vi im ni n (SPC).

TCN 68 - 174: 2006

41

b) V kim loi ca cp xon ti u kt cui ca mng M-IBN h mch (khng ni vi M-IBN) cn u kia ni vi mng CBN.

c) Cc phn kim loi ln cn khi h thng M-IBN phi c lin kt vi SPC trnh hin tng sc in hoc nh thng lp cch in ca v cp.

Ni gia SPC1 v ng cp

Cc khung gi ca khih thng 1 c ni

bng tm m mt li

SPC1

Sn

Tm mmt li

Khuyn ngh ni mnchn cp vi gi cp

Ct thp sn

Khi h thng 3

Cch ly gia tm m mt liv CBN ngn dng ngoi lai

Khi h thng 2

SPC Ca s kt ni mt imDy dn lin kt ng thCt thp lin ktCp nhp hoc cp ni b khng che chnCp nhp hoc cp ni b c che chn

Cp chm ( ) dc theo cnh tm m mt li biu th SPC ca nCp ni b h thng i vo khi i vo khi h thng phi i st SPC

SPC3

ng cp tr khng thp (phn t CBN)

SPC2

Mng A.3: Mng M-IBN trong nh trm vin thng

A.1.3.3 Xy dng mng lin kt cch ly hnh sao (S-IBN)

Mng lin kt cch ly hnh sao trong nh trm vin thng c m t nh trong s hnh A.4.

TCN 68 - 174: 2006

42

1) iu kin thc hin mng lin kt cch ly hnh sao

Cc khi h thng vin thng trong nh trm vin thng c thc hin ni vi CBN bng S-IBN vi nhng iu kin sau:

- Yu cu che chn in t trng cao.

- Dng r mt chiu v xoay chiu trong CBN khng c chy vo khi h thng thit b vin thng.

- Yu cu thi cng n gin, tit kim kinh ph.

2) Trnh t xy dng mng lin kt cch ly hnh sao:

a) Thc hin lin kt cc thnh phn kim loi ca khi h thng S-IBN.

- Cc gi cp trong khi h thng S-IBN c ni vi nhau v ni vi CBN ti thanh dn ni n (SPCB) bng dy dn lin kt c tit din ln hn 14 mm2 (bng cp nhiu si c v bc).

- Cc ca bin, khung gi thit b trong khi h thng S-IBN cch ly hon ton vi CBN ; v chng c ni vi nhau v ni vi CBN ti thanh dn ni n bng dy dn lin kt c tit din ln hn 14 mm2 (bng cp nhiu si c v bc).

b) Thc hin u ni mng lin kt cch ly hnh sao (S-IBN) vi mng lin kt chung (CBN) ti thanh dn ni n (SPCB).

- Thanh dn ni n l mt thanh ng c kch thc trong phm vi sau: Chiu di khng c ln hn 2000 mm, chiu rng t 50 n 100 mm; b dy khng nh hn 3 mm c gn cht vo 1 v tr thch hp chiu di ca dy lin kt l nh nht.

3) Mt s quy nh khi thc hin mng lin kt cch ly hnh sao.

a) V che chn ca cp i vo khi h thng S-IBN c ni vi mng S-IBN ti SPCB, phn bn ngoi khi h thng s c ni vi CBN.

b) H thng con l mt phn ca khi h thng chnh c t trong 1 tng vi h thng chnh v phi dng chung im ni n (SPC) vi h thng chnh ( trnh s chnh lch in p qu mc gia gii hn ca CBN v IBN ln cn).

c) Cc h thng khung thit b, cc thnh phn kt cu kim loi trong MBN t cch S-IBN nh hn 2 m phi c lin kt vi thanh dn SPCB v l do an ton con ngi.

d) Khi thc hin lin kt mng S-IBN phi thc hin kim tra bo dng thng xuyn m bo s cch ly tuyt i.

TCN 68 - 174: 2006

43

nhp c

B

B

Ct

Tng n+1

Thp xy dng(CBN)

Tng n

Thit b BN - mtli (khng v

ng +48V) dc

Tng 1 (c thcch SPCBhn 1 tng)

n in cctip t

FGB Thit b BN mt li(c th cch SPCB nhiu

hn 1 tng)

SPCBFGB

SPCW

i dy xon khng cche chn dn n chuyn mch

Gi phi tuyn(thit b BN - mt li)

i dy xon khng chndn n thit b nhp cp

Ghp st

Busbar +48V dccch ly

Khung gib ngun chnh

Ct thp lin kt v thp xy dngDy dn lin ktDy dn +48V dc (khung v dy -48V i song song)Cp nhp trm hoc cp ni b h thngThanh t tng (mt phn ca CBN)Busbar lin kt n imCa s lin kt n im

FGBSPCBSPCW

IBN (khng v dy dn v +48V)

Cch in

Hnh A.4: Mng lin kt S-IBN trong nh trm vin thng

A.2 Cu hnh u ni v tip t trong trm in t xa

A.2.1 Nguyn tc chung

Trong cc trm in t xa c thc hin cu hnh u ni v tip t dng cu trc che chn bo v thit b in t (EEE) hoc cabin thit b in t (EEC) c ch ra hnh A.5.

TCN 68 - 174: 2006

44

PE

MET

Dy lin kt ph Vng kt ni

Dy lin kt

Khung thit b

Dy dn t

V thit b cp ngun A.C

Dy dn t

Mng tip t

Hnh A.5: Cu hnh u ni v tip t trong trm in t xa

A.2.2 Cc thnh phn ca mt cu trc che chn bo v thit b in t (EEE) hoc cabin thit b in t (EEC)

Cu trc che chn bo v thit b in t hoc nhng cabin thit b in t, bao gm nhng thnh phn sau:

1) Mng lin kt chung CBN to ra bi s lin kt tt c nhng thnh phn cu trc kim loi sn c ca trm vi ng dn kt ni (vng kt ni) c xy dng b sung.

2) Tm tip t chnh.

3) Dy dn t thc hin ni mng tip t vi tm tip t chnh.

4) Dy dn bo v v dy dn lin kt.

Thc hin ni cc khung gi kim loi ca cc khi h thng thit b trong EEE hoc EEC vi mng CBN theo cu hnh mng lin kt mt li (MBN).

A.2.3 Nguyn tc thc hin

A.2.3.1 Trm in t xa phi c trang b mt tm tip t chnh bng ng. Phng php thi cng tm tip t chnh c trnh by trong Ph lc D.

1) Tm tip t chnh phi c t gn ngun cung cp xoay chiu v cc ng vo ca cp vin thng.

2) Tm tip t chnh phi c ni n:

- Dy t bo v PE;

- H thng tip t ca trm in t xa;

- Mng lin kt chung CBN.

TCN 68 - 174: 2006

45

A.2.3.2 Trm in t xa phi xy dng mt mng lin kt chung (CBN)

1) Xy dng mng CBN i vi trng hp trm in t xa c dng cu trc che chn bo v thit b in t (dng EEE).

a) Xy dng ng kt ni bn trong phi c dng vng khp kn c gi l vng kt ni. Mi EEE xy dng 2 vng kt ni: 1 vng kt ni gn trn, 1 vng kt ni gn sn.

Vng kt ni phi c gn vo tng hoc dc theo pha ngoi cc gi cp gn tng v phi cao thch hp thun li cho vic ni cc khung gi thit b.

b) Thc hin ni vng kt ni vi cc thnh phn kim loi ca trm nh: khung b tng ct thp ca trm.

c) Thc hin ni vng kt ni vi tm tip t chnh.

d) Phi c 1 thanh ni ph bc cu qua vng kt ni thc hin u ni khung gi thit b lp t cch xa cc bc tng vi CBN c thun li.

2) Xy dng mng CBN i vi trng hp trm in t xa c dng cabin thit b in t (dng EEC).

a) i vi cabin thit b in t mng CBN c to nn bi nhng thnh phn kt cu xy dng v nhng bc tng chn bng kim loi c hn ni vi nhau.

b) Mng CBN phi ni n tm tip t chnh MET.

A.2.3.3 Vic b tr cng vo ca cp ngoi vi phi bo m cc nguyn tc sau:

- Khong cch gia cng vo cp thng tin trong EEE v cng vo ca cp ngun phi cng nh cng tt v khng c ln hn 4 m.

- Khong cch gia cc cng vo cp thng tin v MET cng phi nh hn 4 m (o dc theo tng).

A.2.3.4 Khong cch gia cp thng tin chy song song vi cp in lc khng c mn chn tnh in t nht l 10 cm.

A.2.3.5 Thc hin ni cc thnh phn kim loi ca cp ngoi vi vi vng kt ni (vi mng CBN)

a) Cc mn chn bng kim loi hoc cc thnh phn cu trc bng kim loi ca cp ngoi vi phi c ni vi vng kt ni hoc ni trc tip vi tm tip t chnh. im ni cng gn cng vo cp cng tt. Vi khong cch khng ln hn 2 m.

b) Nu cc cp ngoi vi pht trin su vo bn trong EEE v t xa ch ni th mi ni th hai n vng kt ni phi u cui ca cc cp ti ni chng c ni vi cp bn trong.

c) Nu khng th b tr c cng vo cc cp ngoi vi cch tm tip t chnh (MET) nh hn 4 m (o dc theo tng) th phi c thm t nht 1 trong cc mi ni ph gia v kim loi cp ngoi vi n cc phn t sau:

- n vnh ai ngoi ca h thng tip t ca trm;

- n in cc tip t ch yu hoc cc thnh phn thp gia cng;

TCN 68 - 174: 2006

46

- n vng lin kt th hai (gn sn nh).

Mi ni thm n cp ngoi vi cng gn cng vo cng tt v khng c vt qu 2 m.

d) Cc thnh phn kim loi lin tc v in ca cc cp si quang ngoi vi khng c i vo trong EEE qu ch ni n vng kt ni. Nu cc phn t l gin on th c i vo trong EEE chng phi c ni n vng kt ni ti thit b u cui.

- Trong mt EEC, mi ni gia cc phn t kim loi ca cp ngoi vi v bus kt ni phi cng gn cng vo cng tt.

e) Trong cabin thit b in t (EEC) mi ni gia cc thnh phn kim loi ca cp ngoi vi v vng kt ni phi cng gn cng vo cng tt.

A.2.3.6 Tt c cc khung, gi, v bc bng kim loi ca thit b bn trong 1 EEE v tt c cc thnh phn kim loi khc di vo EEE (ng dn nc, ng dn kh...) phi c ni n vng kt ni bn trong (ni n mng CBN).

A.2.3.7 Nu s dng cc b bo v trn cc i dy thng tin th cc cc chung (cc tip t) ca cc b bo v phi c ni n tm tip t chnh (MET).

TCN 68 - 174: 2006

47

Ph lc B

Xc nh vng bo v ca h thng chng st nh trc tip

B.1 Vng bo v ca h thng chng st nh trc tip dng in cc Franklin

Vng bo v ca in cc thu st ca h thng chng st nh trc tip dng in cc Franklin c xc nh bng cc phng php sau:

- Phng php gc bo v;

- Phng php qu cu ln.

C th dng mt phng php hoc kt hp hai phng php trn xc nh v tr ca cc in cc thu st cho mt cng trnh, sao cho vng bo v ca cc in cc thu st giao nhau v che ph hon ton cng trnh cn bo v.

a) Phng php gc bo v

Phng php gc bo v thch hp vi cc cng trnh c cu trc n gin hoc vi mt phn nh ca cng trnh ln.

Theo phng php ny, vng bo v to bi mt in cc thu st c xc nh bng

hnh nn c nh l in cc thu st (c cao h) v gc sinh a (xem hnh B.1). Gc a c xc nh ph thuc vo mc bo v v cao ca in cc thu st so vi b mt c bo v (xem bng B.1).

Bng B.1: Xc nh vng bo v ca in cc thu st

20 30 45 60 Mc bo v h (m)

R (m) a a a a I 20 25 * * *

II 30 35 25 * *

III 45 45 35 25 *

IV 60 60 45 35 25

* Khng p dng phng php gc bo v cho cc trng hp ny (ch p dng phng php qu cu ln).

Hnh B.1: Xc nh vng bo v ca mt in cc thu st

Vng bo v

R a h

TCN 68 - 174: 2006

48

Khng p dng phng php gc bo v trong trng hp cao h ln hn bn knh qu cu ln R xc nh trong bng B.2.

Hnh B.2 v B.3 minh ha vng bo v ca mt in cc thu st thng ng v mt in cc thu st dng dy dn nm ngang.

Hnh B.2: Vng bo v ca mt in cc thu st thng ng

Hnh B.3: Vng bo v ca mt in cc thu st dng dy dn nm ngang

ht

ht

O

O

C

C

a

a

A

A

ht

a

O C B

A

A - nh ca in cc B - mt phng chun OC - bn knh ca vng c bo v ht - cao ca in cc so vi mt phng chun

a - gc bo v theo bng B.1

TCN 68 - 174: 2006

49

b) Phng php qu cu ln

Trong trng hp khng s dng c phng php gc bo v, c th dng phng php qu cu ln xc nh v tr ca ca in cc thu st. Phng php ny thch hp vi cng trnh c cu trc phc tp.

Theo phng php ny, in cc thu st s c lp t cc v tr sao cho khng c im no ca cng trnh cn bo v chm vo mt qu cu tng tng bn knh R ln trn t, xung quanh ton b b mt cng trnh v ln trn nh ca cng trnh theo tt c cc hng (xem hnh B.4). Nh vy, qu cu ln s ch chm mt t v/hoc in cc thu st. Bn knh ca cu ln c xc nh theo mc bo v ca h thng chng st (xem bng B.1).

Hnh B.4: Xc nh in cc thu st theo phng php qu cu ln

B.2 Vng bo v ca h thng chng st nh trc tip pht tin o sm

Vng bo v ca h thng chng st pht tin o sm c xc nh bng bn knh bo v tng ng vi cc cao khc nhau.

Bn knh bo v c xc nh bng cng thc sau:

= - + D + D(2 ) (2 )pR h R h L R L

Trong :

R - bn knh qu cu ln, c xc nh theo mc bo v, m (xem bng B.1);

h - cao ca kim thu st so vi mt phng i qua v tr cn bo v ang xt, m;

DL - li v chiu di tia tin o ca in cc pht tin o sm so vi in cc Franklin, m.

li DL c tnh nh sau:

DL(m) = v(m/ms). DT(ms) Trong :

DT (ms) - li v thi gian ca s hnh thnh tia tin o ca in cc pht tia tin o sm so vi in cc Franklin, c trng cho tnh hiu qu ca h thng pht tin o sm;

Ghi ch: Gi tr DT do nh sn xut cung cp.

v (m/ms) = 1 m/ms - vn tc tia tin o.

R

R

R

in cc thu st

R: Bn knh qu cu ln (theo bng B.1)

TCN 68 - 174: 2006

50

Ph lc C Tnh ton tip t cho cc cng trnh vin thng

C.1 Tnh ton in tr tip t trong t ng nht

C.1.1 in tr tip t ca mt in cc trong t ng nht

C.1.1.1 in tr tip t ca mt ng kim loi chn thng ng trong t ng nht c xc nh bng cng thc:

1. Khi nh ca ng ngay trn mt t:

r= W

pl

l4

ln , ;2d

Rd

(C.1)

Trong :

r - in tr sut ca t, W.m; l - chiu di ca ng, m; d - ng knh ngoi ca ng, m.

2. Khi nh ca ng su trong t:

r += W

p +l l

l l4 ( 2 )

ln ,2 ( 4 )d

hRd h

; (C.2)

Trong :

h - khong cch t mt t n nh ca ng, m.

Ch : Nu thanh tip t bng thp gc, thay d = 0,95a; vi a l chiu rng pha ngoi ca thanh thp gc.

C.1.1.2 Khi thit k cc h thng tip t dng cc ng kim loi chn thng ng trong t, hp l nht khi chn chiu di ca ng l = (1,5 3) m; khong cch t mt t n nh ca ng chn khng nh hn 0,7 m; ng knh d, ca ng chn theo loi t nh sau:

1. t c ln cht trung bnh d = (2,5 4) cm;

2. t rn, chn loi ng c d = (4 6) cm.

C.1.1.3 in tr tip t ca mt di kim loi dt, di, t nm ngang su h trong t ng nht, c xc nh bng cng thc:

r= W

pl

l1,5

R .ln( ),d bh (C.3)

Trong : b - chiu rng ca di, m; l - chiu di ca di, m; h - su chn di, m;

r - in tr sut ca t, W.m.

TCN 68 - 174: 2006

51

C.1.1.4 in tr tip t ca mt dy kim loi tit din trn, ng knh d, t nm ngang su, h trong t ng nht, c xc nh bng cng thc:

r= W

pl

lR ln( ),d dh

(C.4)

Trong : d - ng knh ca dy, m.

C.1.1.5 Khi thit k cc h thng tip t, dng cc dy kim loi di, hp l nht chn dy c ng knh d = (2 6) mm, su t dy hoc di tip t khng nh hn 0,7 m. Chiu di ca dy hoc di tip t chn ti u theo in tr sut ca t, nh trnh by trn hnh C.1

, m80

60

40

20

10200 400 600 1000 2000 5000 10000

Hnh C.1: Chn chiu di ca dy hoc di tip t theo in tr sut ca t

C.1.1.6 Ni c din tch t hp c th dng in cc tip t loi dy trn hoc dt, t di dng mt vng trn

1. in tr tip t ca mt dy dt, t di dng mt vng trn trong t ng nht, xem hnh C.2a, c xc nh bng cng thc:

r= W

p27

R .ln( ),dD

D bh (C.5)

Trong :

r - in tr sut ca t, W.m; D- ng knh ca vng trn tip t, m; b - chiu rng ca di dt, m; h - chn su ca tip t, m.

2. in tr tip t ca mt dy tit din trn, t di dng mt vng trn trong t ng nht, xem hnh C.2, c xc nh bng cng thc:

r= W

p25

R .ln( ),dD

D dh (C.6)

TCN 68 - 174: 2006

52

hoc bng cng thc:

r= W

pl

l1,27

R .ln( ),d dh (C.7)

Trong : d - ng knh ca dy, m;

l = p.D - chu vi ca vng trn (chiu di tip t dng vng trn), m. a) Dng dy dt

b. Dng dy trn

Hnh C.2: in cc tip t dng vng trn

C.1.1.7 in tr tip t ca in cc bng kim loi dng tm trn hoc ch nht c xc nh bng cng thc:

1. Tm kim loi dng trn t trn b mt t ng nht r

= W, ;2d

RD

(C.8)

2. Tm kim loi dng trn t su h trong t ng nht, vi h >0,5D r = + W p

2 1, ;

8dR

D h (C.9)

Trong :

h - su chn tm kim loi, m;

r - in tr sut ca t, W.m; D - ng knh ca tm trn hoc ng knh tng ng ca cc tm dng ch nht

hoc vung, cm;

b

B A

D

h

d

h

D

TCN 68 - 174: 2006

53

Ch thch: ng knh tng ng ca mt tm kim loi dng ch nht hoc vung l ng knh ca ng trn c din tch bng din tch ca tm xem xt.

C.1.1.8 Vic s dng in cc tip t dng tm phng t trong t theo phng nm ngang hoc thng ng rt kh do th tch o h tip t ln, c th dng cc di kim loi xon thnh dng l xo, to ra mt ng c chiu di l = 1,42 m vi ng knh d = 0,2 m hoc chiu di l = 0,71 m vi ng knh d = 0,4 m, khi tnh ton in tr tip t theo cng thc nh i vi in cc tip t dng ng.

C.1.2 Tnh ton in tr tip t c nhiu in cc trong t ng nht

C.1.2.1 nhn c tr s in tr tip t yu cu, ta cn ni song song mt s cc in cc tip t n vi nhau. H thng tip t ny c gi l h thng tip t c nhiu in cc. Trn hnh C.3 trnh by mt h thng tip t gm nhiu ng v trn hnh C.4 trnh by mt h thng tip t gm nhiu tia di.

Hnh C.3: H thng tip t gm nhiu ng

a) Hai tia b) Ba tia c) Bn tia

Hnh C.4: H thng tip t gm nhiu tia di

a a a a

h

l

TCN 68 - 174: 2006

54

C.1.2.2 in tr tip t ca mt h thng gm n ng kim loi ging nhau, chn thng ng trong t ng nht, khi b qua nh hng ca dy ni cc in cc (dy ni cch in vi t) do tc dng che chn ln nhau ca cc in cc, c xc nh bng cng thc:

= Wh0 , ;d

RRn

(C.10)

Trong :

R0- in tr tip t ca mt in cc n c lp, W;

n- s in cc trong h thng;

h- h s s dng in cc tip t (gi tr trung bnh t tr s o thc nghim, ly ging nhau cho tt c cc in cc trong h thng).

C.1.2.3 in tr tip t ca mt h thng gm nhiu ng kim loi ging nhau chn thng ng trong t ng nht, c xt n in tr tip t ca dy (di) ni cc in cc tip t vi nhau, c xc nh bng cng thc:

= Wh + h

1 2

2 1 1 2

, ;dR RR

n R R (C.11)

Trong :

R1- in tr tip t ca cc dy (di) ni cc in cc tip t, W;

R2- in tr tip t ca mt ng (thp gc) chn thng ng, W;

h1- h s s dng ca dy (di) ni;

h2- h s s dng ca in cc chn thng ng; n - s in cc chn thng ng.

Ghi ch: y l trng hp cho cc ng tip t chn theo mt hng.

C.1.2.4 Tr s h s s dng ph thuc vo kch thc cc in cc tip t, khong cch gia cc in cc v s b tr cc in cc

H s s dng cc di ni cc ng (hoc thp gc) t thnh hng c trnh by trong bng C.1.

H s s dng cc di ni cc ng (hoc thp gc) t thnh khung kn c trnh by trong bng C.2.

Bng C.1: H s s dng cc di ni cc ng (hoc thp gc) t thnh hng

H s s dng theo s ng trong n hng T s khong cch gia cc ng vi chiu di ca ng, a/l 4 5 8 10 20 30 50 65

2 0,89 0,86 0,79 0,75 0,56 0,46 0,36 0,34

3 0,92 0,90 0,85 0,82 0,68 0,58 0,49 0,47

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Bng C.2: H s s dng cc di ni cc ng (hoc thp gc) t thnh khung kn

H s s dng, khi s ng trong khung, n T s khong cch gia cc ng vi chiu di ca ng, a/l 4 6 8 10 20 30 50 70 100

2 0,55 0,48 0,43 0,40 0,32 0,30 0,28 0,26 0,24

3 0,70 0,64 0,60 0,56 0,45 0,42 0,37 0,35 0,33

C.1.2.5 in tr tip t ca mt h thng gm cc thanh (ng) b tr trn din tch S trong t ng nht, c th c xc nh bng cng thc:

r = - + - W p

l ll

28 2R . ln( ) 1 ( )( 1) ,2

K nn d S

(C.12)

Trong :

r - in tr sut ca t, W.m; l - chiu di ca thanh (ng), m;

d - ng knh ca thanh (ng), m;

S - din tch ca h thng tip t, m2;

n - s in cc (thanh, ng);

K - h s, c gi tr trnh by trn hnh C.5.

C.1.2.6 in tr ca mt h thng tip t c dng bt k gm cc thanh hoc ng chn thng ng trong t ng nht c th c xc nh bng cng thc:

r W p

l ll l

2 4 +7tR = . ln( ) + 0,5ln + A , ;

2 n d + t (C.13)

Trong :

d - ng knh ca ng tip t, m;

t - su chn ng tip t, m;

n - s lng cc ng tip t;

A - tr s xt n s che chn ln nhau ca cc thanh hoc ng tip t.

Cc gi tr ca A i vi mt s cc trng hp tip t c trnh by trong bng C.3.

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Hnh C.5: Gi tr h s K i vi h thng tip t gm cc thanh (ng) ph thuc vo t s chiu di v chiu rng ca din tch tip t

Bng C.3: Cc gi tr ca A cho mt s trng hp tip t gm cc ng chn thng ng

Dng h thng tip t S in cc A R.2.p.l/r

6 3,07 1,34

10 3,18 0,82

21 4,30 0,445

40 7,33 0,385

80 8,98 0,175

69 9,95 0,212

98 11,30 0,165

21 6,27 -

1 2 3 4 5 6 7 8 T s chiu di v chiu rng ca din tch tip t

1,40

K

1,35

1,30

1,25

1,20

1,15

1,10

1,05

1,00

0,95

0,90

Vi su chn ng tip t t = 0

Vi 10/St =

Vi t S / 6=

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C.1.2.7 in tr ca mt h thng tip t c dng bt k gm cc dy hoc di t nm ngang trong t ng nht c th c xc nh bng cng thc sau:

rW

p

2LR = . ln( ) + A , ;

2 L dt (C.14)

Trong :

L - tng chiu di ca tip t, m;

r - in tr sut ca t, W.m; d - ng knh ca dy lm tip t, m;

t - su chn tip t, m;

A - tr s xt n s nh hng ln nhau ca cc b phn tip t ring r, c gi tr i vi mt s dng tip t c trnh by trong bng C.4.

Bng C.4: Cc gi tr ca A cho mt s trng hp tip t nm ngang

Gi tr ca A khi t s cc cnh Dng tip t A Dng tip t

1 1,5 2 3 4

0,48

1,69 1,76 1,86 2,10 2,34

0,36

3,67 3,41 3,31 3,29 3,35

0,87

4,95 5,16 5,44 6,00 6,52

2,13

5,61 5,04 4,73 4,43 4,33

5,27

8,55 8,24 9,40 10,3 11,11

8,81

- - 9,02 - -

D

l/D=3/2

7,20

- - 22,73 - -

C.1.2.8 in tr ca h thng tip t gm n dy (di) t nm ngang trong t ng nht di dng bc x (cc di c cng mt im ni) c tnh bng cng thc:

r = - + W p

ll

4ln 1 ( ) , ;dR N nn d

(C.15)

Trong :

l - chiu di ca tia, m;

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d - ng knh ca dy, m;

n - s tia;

r - in tr sut ca t, W.m; -

=

+ p=

p1

1

sin( / )( ) ln

sin( / )

n

k

l k nN nk n

Vi n > 6; N(n) (n-1) ln(2.1,707) - ln(n)

Mt s cc gi tr ca N(n) c trnh by trong bng C.5.

Bng C.5: Mt s cc gi tr ca N(n)

n 2 3 4 6 8 12 100

N(n) 0,7 1,53 2,45 4,42 6,5 11,0 11,6

C.1.2.9 in tr tip t ca h thng gm n tm kim loi ging nhau ni song song vi nhau bng dy cch in, c xc nh bng cng thc:

= Wh

,dRRn

Trong :

n - s tm;

R - in tr tip t ca mt tm, W;

h - h s s dng tip t, ph thuc vo s tm v s b tr ca cc tm, c gi tr thay i trong phm vi t 0,25 n 0,7.

C.2 Tnh ton in tr tip t trong t khng ng nht

C.2.1 Tnh ton in tr tip t ca cc tip t n trong t khng ng nht

C.2.1.1 Trong thc t t c kt cu khng ng nht. Thng t c nhiu lp c xc nh bi kt cu a cht ca t. Gi tr in tr sut ca cc lp t pha trn thay i theo ma

Vic tnh ton in tr tip t trong trng hp ny theo dng kt cu t ng nht s c sai s ln.

tnh ton in tr tip t trong trng hp t c nhiu lp c th s dng h s ma. Nhng kt qu nghin cu thc nghim h s ma cho thy rng h s ma l khng ging nhau khng nhng ch cc ch khc nhau m cn thay i mnh trong phm vi ca mt vng khng ln lm, ph thuc vo v tr c th b tr tip t.

c kt qu tnh ton chnh xc hn cn phi xt n cc lp t c dn khc nhau. Mc d trong trng hp tng qut t c kt cu nhiu lp, nhng tuyt i a s cc trng hp chnh xc ta c th thay bng cu hnh t hai lp, trong lp trn c chiu dy h v c in tr sut r1 cn lp di dy v cng c in tr sut r2.

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C.2.1.2 in tr tip t ca mt ng chn thng ng trong t khng ng nht gm hai lp (xem hnh C.6) c xc nh bng cng thc:

W p r r

l l2 1

1 h -h 4R = + ln( ), ;

2 d (C.16)

Trong :

d - ng knh ca ng, m;

l - chiu di ca ng, m;

h - chiu dy ca lp t pha trn, m;

r1, r2 - in tr sut tng ng ca cc lp t pha trn v pha di, W.m.

1

2

ht

Hnh C.6: in cc tip t chn thng ng trong t c hai lp

C.2.1.3 in tr tip t ca mt dy (hoc di) di nm ngang trong t khng ng nht gm hai lp, c xc nh bng cng thc:

1. Khi dy (hoc di) tip t di nm trong lp t pha trn (t < h)

=

r = + + + W p + - l l l ll

21

1

0,25 0,25ln 2 ,

2 4 ( ) ( )n

nR K arsh arsh arsh

dt hn hn t hn t

(C.17)

2. Khi dy (hoc di) tip t di nm trong lp t pha di (t>h)

=

r = + + W p + - + l l ll

22

1

0,25 0,25ln ,

2 ( ) ( 2)n

nR K arsh arsh

dt hn t n h t (C.18)

Trong :

l - chiu di ca dy (hoc di), m;

K = (r2-r1)/(r2+r1) - h s khng ng nht ca t;

d - ng knh ca dy, m; (nu l di, th ng knh tng ng ca mt di c chiu rng b c ly bng d = b/2).

C.2.1.4 in tr tip t ca in cc di dng vng trn trong t c hai lp, khi mt phng ngn cch gia hai lp trng vi mt ng th, c xc nh bng cng thc:

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r r - r + = - W p p +

2 21 1 2

2 2 2 2

8 4.ln .ln , ;

D D hRd hD D h

(C.19)

Trong :

D - ng knh ca vng trn tip t, m;

d - ng knh (hoc ng knh tng ng) ca dy (hoc di), m;

r1, r2 - in tr sut tng ng ca cc lp t trn v di, W.m; h - chiu dy ca lp t pha trn, m.

C.2.1.5 in tr tip t ca in cc dng tm trong t khng ng nht, gm hai lp khi mt ngn cch trng vi mt ng th tip t, c xc nh bng cng thc:

r r r W pr 1 1 2

1

2( - ) dR = . 1- .arctg , ;

2D 2h (C.20)

Trong :

D - ng knh (hoc ng knh tng ng) ca tm, m.

C.2.1.6 in tr tip t ca in cc dng li t trong t khng ng nht gm hai lp, c xc nh bng cng thc:

br r r rW

- h1 2 1 1+( - ).eR = + , ;

2D L (C.21)

Trong :

L - tng chiu di cc dy (hoc di) di, m;

D - ng knh din tch ca li, m;

b - tham s (1/m) khi xt n s phn b khng ng nht ca r

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tcn 68 - 174 2006-65e6bb617295