CCH CH»ŒN T»¤ B™ THEO TIU CHU¨N QU»C T¾

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1. CCH CHN T B THEO TIU CHUN QUC T (IEC)I.Ti sao cn ci thin h s cng sut:1.Gim gi thnh tin in:- Nng cao h s cng sut em li nhng u im v k thut v kinh t, nht l gim tin in.- Trong giai on s dng in c gii hn theo qui nh. Vic tiu th nng lng phn khng vt qu 40% nng lng tc dng (tg> 0,4: y l gi tr tho thun vi cng ty cung cp in) th ngi s dng nng lng phn khng phi tr tin hng thng theo gi hin hnh.- Do , tng nng lng phn khng c tnh tin cho thi gian s dng s l:kVAr ( phi tr tin ) = KWh ( tg 0,4)- Mc d c li v gim bt tin in, ngi s dng cn cn nhc n yu t ph tn do mua sm, lp t bo tr cc t in ci thin h s cng sut.2.Ti u ho kinh t - k thut - Ci thin h s cng sut cho php ngi s dng my bin p, thit b ng ct v cp nh hn V.Vng thi gim tn tht in nng v st p trong mng in. - H s cng sut cao cho php ti u ho cc phn t cung cp in. Khi y cc thit b in khng cn nh mc d tha. Tuy nhin t c kt qu tt nht, cn t t cnh cnh tng phn t ca thit b tiu th cng sut phn khng.Ci thin h s cng sut - ci thin h s cng sut ca mng in, cn mt b t in lm ngun pht cng sut phn khng. Cch gii quyt ny c gi l b cng sut phn khng. -Ti mang tnh cm c h s cng sut thp s nhn thnh phn dng in phn khng t my pht a n qua h thng truyn ti phn phi. Do ko theo tn tht cng sut v hin tng st p.- Khi mc cc t song song vi ti, dng in c tnh dung ca t s c cng ng i nh thnh phn cm khng ca dng ti. v vy hai dng in ny s trit tiu ln nhau IC= IL. Nh vy khng cn tn ti dng phn khng qua phn li pha trc v tr t t.- c bit ta nn trnh nh mc ng c qu ln cng nh ch chy khng ti ca ng c. Lc ny h s cng sut ca ng c rt nh (0,17) do lng cng sut tc dng tiu th ch khng ti rt nh.II.Cc thit b b cng sut: 1. B trn li in p Trong mng li h p, b cng sut c thc hin bng :-T in vi lng b c nh (b nn).-Thit b iu chnh b t ng hoc mt b t cho php iu chnh lin tc theo yu cu khi ti thay i.Ch : Khi cng sut phn khng cn b vt qu 800KVAr v ti c tnh lin tc v n nh, vic lp t b t pha trung p thng c hiu qu kinh t tt hn.2. T b nnB tr b gm mt hoc nhiu t to nn lng b khng i. vic iu khin c th thc hin:-Bng tay: dng CB hoc LBS ( load break switch )-Bn t ng: dng contactor-Mc trc tip vo ti ng in cho mch b ng thi khi ng ti.Cc t in c t:-Ti v tr u ni ca thit b tiu th in c tnh cm ( ng c in v my bin p ).-Ti v tr thanh gp cp ngun cho nhiu ng c nh v cc ph ti c tnh cm khng i vi chng vic b tng thit b mt t ra qu tn km.-Trong cc trng hp khi ti khng thay i.3. B t b iu khin t ng ( b ng ng )- B cng sut thng c hin bng cc phng tin iu khin ng ngt tng b phn cng sut.- Thit b ny cho php iu khin b cng sut mt cch t ng, gi h s cng sut trong mt gii hn cho php chung quanh gi tr h s cng sut c chn.- Thit b ny c lp t ti cc v tr m cng sut tc dng v cng sut phn khng thay i trong phm vi rt rng. v d: ti thanh gp ca t phn phi chnh, ti u ni ca cc cp trc chu ti ln.Cc nguyn l v l do s dng b t ng:- B t b gm nhiu phn v mi phn c iu khin bng contactor. Vic ng mt contactor s ng mt s t song song vi cc t vn hnh. V vy lng cng sut b c th tng hay gim theo tng cp bng cch thc hin ng hoc ct contactor iu khin t. Mt rley iu khin kim sot h s cng sut ca mng in s thc hin ng v m cc contactor tng ng h s cng sut c h thng thay i ( vi sai s do iu chnh tng bc ). iu khin rle my bin dng phi t ln mt pha ca dy cp dn in cung cp n mch c iu khin. Khi thc hin b chnh xc bng cc gi tr ti yu cu s trnh c hin tng qu in p khi ti gim xung thp v do kh b cc iu kin pht sinh qu in p v trnh cc thit hi xy ra cho trang thit b.- Qu in p xut hin do hin tng b d ph thuc mt phn vo gi tr tng tr ngun.Cc qui tc b chung- Nu cng sut b t ( kVar ) nh hn hoc bng 15% cng sut nh mc my bin p cp ngun, nn s dng b nn. - Nu trn mc 15%, nn s dng b kiu t ng.- V tr lp t t p trong mng in c tnh n ch b cng sut; hoc b tp trung, b nhm, b cc b, hoc b kt hp hai phng n sau cng.- V nguyn tc, b l tng c ngha l b p dng cho tng thi im tiu th v vi mc m ph ti yu cu cho mi thi im.- Trong thc tin, vic chn phng cch b da vo cc h s kinh t v k thut.V tr lp t t b:3.1B tp trung:p dng cho ti n nh v lin tc.Nguyn l: b t u vo thanh gp h p ca t phn phi chnh v c ng trong thi gian ti hot ng.u im:- Gim tin pht do vn tiu th cng sut phn khng .- Lm gim cng sut biu kin.- Lm nh ti cho my bin p v do n c kh nng pht trin thm cc ph ti cn thit.Nhn xt:- Dng in phn khng tip tc i vo tt c l ra t phn phi chnh ca mng h th.- V l do ny kch c dy dn , cng sut tn hao khng c ci thin ch b tp trung. 3.2 B nhm ( tng phn on ).B nhm nn s dng khi mng in qu ln v khi ch ti tiu th theo thi gian ca cc phn on thay i khc nhau.Nguyn l: b t c u vo t phn phi khu vc . hiu qu do b nhm mang li cho dy dn xut pht t t phn phi chnh n cc t khu vc c t t c th hin r nht.u im:- Lm gim tin pht do vn tiu th cng sut phn khng.- Lm gim cng sut biu kin yu cu.- Kch thc dy cp i n cc t phn phi khu vc s gim i hoc vi cng dy cp trn c th tng thm ph ti cho t phn phi khu vc.Nhn xt :- Dng in phn khng tip tc i vo tt c dy dn xut pht t t phn phi khu vc.- V l do ny m kch thc v cng sut tn hao trong dy dn ni trn khng c ci thin vi ch b nhm.- Khi c s thay i ng k ca ti, lun lun tn ti nguy c b d v km theo hin tng qu in p.3.3 B ring:B ring nn c xt n khi cng sut ng c ln ng k so vi mng in.Nguyn l: b t mc trc tip vo u dy ni ca thit b dng in c tnh cm ( ch yu l cc ng c ).B t nh mc ( kVAr) n khong 25% gi tr cng sut ng c. B b sung ti u ngun in cng c th mang li hiu qu tt.u im :Lm gim tin pht do tiu th cng sut phn khng (kVAr)Gim cng sut biu kin yu cu.Gim kch thc v tn hao dy dn i vi tt c dy dn.Nhn xt :Cc dng in phn khng c gi tr ln s khng cn tn ti trong mng in.3.4 Mc b ti uPhng php chungBng s liu tnh ton cng sut phn khng cn thit trong giai on thit k. qua c th xc nh cng sut phn khng v cng sut tc dng cho mc b khc nhau.Vn ti u ho kinh t k thut cho mt mng in ang hot ng.Vic tnh ton nh mc b ti u cho mt mng tn ti c th thc hin theo nhng lu sau:+ Tin in trc khi t b+ Tin in tng lai sau khi lp t b.+ Cc chi ph bao gm :-Mua t b v mch iu khin.-Lp t v bo tr-Tn tht trong t v tn tht trn dy cp, my bin p sau khi lp t b.III. Chn T B :1. Phng php tnh n gin:( chn t b cho mt ti no th ta cn bit cng sut(P) ca ti v h s cng sut (Cos ) ca ti ): Gi s ta c cng sut ca ti l P H s cng sut ca ti l Cos 1tg 1( trc khi b ) H s cng sut sau khi b l Cos 2tg 2. Cng sut phn khng cn b l QC= P (tg1 tg2).T cng sut cn b ta chn t b cho ph hp trong bng catalog ca nh cung cp t b. d hiu ta s cho v d minh ho nh sau: Gi s ta c cng sut ti l P = 270 (KW). H s cng sut trc khi b l cos1= 0.75tg1= 0.88 H s cng sut sau khi b l Cos2= 0.95tg2= 0.33 Vy cng sut phn khng cn b l Qb= P ( tg1 tg2) Qb= 270( 0.88 0.33 ) = 148.5 (KVAr) T s liu ny ta chn t b trong bng catalog ca nh sn xut gi s l ta c t 25KVAr. b cho ti th ta cn b 6 t 25 KVAr tng cng sut phn khng l 6x25=150(KVAr) vi 6 t b ny ta chn b iu khin 6 cp . 2. Phng php b ti u da vo iu kin khng ng tin pht: Xt ho n tin in lin quan n dung lng kVArh tiu th v ghi nhn s kVArh phi tr tin sau , chn ho n tin gi kVArh cao nht phi tr (khng xt n trng hp ngoi l). V d: 15965 kVArh trong thng gingTnh tng thi gian hot ng trong thng v d : 220h s gi xt tnh l nhng gi m h thng in chu ti ln nht v ti t gi tr nh cao nht. ngoi thi gian k trn vic tiu th cng sut phn khng l min ph. Gi tr cng sut cn b: [kVAr] =kVAr/T= QbkVAr : s kVAr phi tr tin.T : s gi hot ng Dung lng b thng c chn cao hn gi tr tnh ton mt cht. Mt s hng cung cp qui tc thc loga thit k t bit cho vic tnh ton ny theo cc khung gi ring. Cng c trn v cc d liu km theo gip ta chn la thit b b v s iu khin thch hp, ng thi rng buc ca cc sng hi in p trong h thng in . cc sng hi ny i hi s dng nh mc t d ( lin quan n gii nhit, nh mc p v dng in ) v cc cun khng hoc mch lc sng hi.ng26th FebruarybiHKmeNhn:TI LIU THAM KHO0Add a comment

2. FEB25

GIM ST THI CNG V NGHIM THU LP T NG DY V THIT B TRONG CNG TRNH INBi vit ny trnh by nhng iu c bn v cc kin thc phc v cho thi cng v nghim thu lp t ng dy v thit b trong cng trnh in.

CCH T DY DN INCc hng dn trong chng ny p dng lp t v nghim thu cc dy dn in ng lc v chiu sng in p 1 chiu v xoay chiu n 1000 vn trong nh v ngoi tri bng dy dn cch in v cp khng c v thp mt ct b.Cn dy dn trn phi tun theo chng VIII sau y.7.1. Yu cu chungKiu, mt ct v loi dy dn do thit k quy nh theo ph ti v c im ni t.Ch ni v phn nhnh cc dy dn v cp khng c chu cc ng sut c hc. Ch ni v phn nhnh rut cp v dy dn phi c cch in tng ng vi cch in nhng ch cn nguyn vn. Phi dng cc hp ni v hp phn nhnh ni cng nh phn nhnh cc dy dn trong cc hp bt kn, trong cc ng v trong cc ng lng mm bng kim loi khi t h cng nh khi t ngm.Cu to ca cc hp ni v hp phn nhnh phi ph hp vi cch t dy iu kin mi trng.Bn trong cc hp c np ng m c v cc mng nn ni v phn nhnh dy dn bng cc kp chuyn dng c v cch in m bo.ch dy dn chui ra khi hp, mng, ng cng v ng lng mm bng kim loi u phi c bo v trnh h hng.nhng ch dy dn giao cho vi cc mi ni co dn phi c vt b tr co dn.

Khng quy nh cao lp t cch nn nh hoc sn nh cho dy dn cch in c bo v, dy dn lun trong cc ng thp v cc ng lng mm bng kim loi, cp mm lm vic trong iu kin nng.nhng ch dy dn v cp c th b h hng do c hc th phi c bo v thm.

Cc ng cch in c v kim loi, cc ng giy bo v dy dn in, cc cp v ng lng mm bng kim loi cn phi c nh vo cc mt . Vi khong cch c nh l: 0,8 - 1 m vi ng 0,5 - 0,7m vi dy dn, cp v ng lng mm bng kim loi.Khi t song song vi cc ng ng th khong cch t dy dn v cp n ng ng t nht l 100 mm v phi ch cc ng ng nhin liu lng v kh t nht l 250 mm.Khi t gn cc ng c nhit cao th dy dn v cp phi c bo v chng tc hi do nng hoc phi dng doi dy dn v cp thch hp.Trong cc hp v mng, dy dn v dy cp phi t cch nhau mt khong l 5mm thnh tng dy. Cho php t dy dn ni trn thnh tng b khng qu 12 giy v cc b phi cch nhau t nht l 20 mm. Khi cc b dy dn phi c c nh cht bng cc vng kp, vng ai v.v).Khi cc hp t dy b tr thng ng hay t quay np xung di th bt buc phi c nh cht cc dy dn.Trong cc gian i hi phi ni t th cc hp v cc mng t dy dn ni vi nhau phi to nn mt mch in lin tc trn ton b chiu di ca chng.Cc dy dn t h phi phi hp vi cc ng nt kin trc ca nh v cng trnh m bo m thut.Chiu di ca cc dy dn t trong cc gian m t (git, tm.v.v.v) cng ngn cng tt. Cc dy dn nn t bn ngoi cc gian ny v n chiu sng nn t gn dy dn trn tng.Dy dn t theo b mt kt cu b h thng xuyn nung nng (ng dn khi, ng dn