Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h21 CHNG I BO V CHNG ST NH TRC TIP VO TRM BIN P 220/110 kV 1)KHI NIM CHUNG Tronghthngintrmbinplmtphnthtscquantrngtrongh thng in truyntiv phn phiinnng.i vi trmbin p 220 kVv 110 kV th cc thit b t ngoi tri. Do , khi cc thit b ca trm b st nh trctipthsdnnnhnghuqurtnghimtrng,khngnhnglmh hng cc thit b trong trm m cn c th dn n ngng cung cp in ton b trong thi gian di nh hng ti vic sn xut in nng v cc nghnh kinh t quc dn khc. Do vy, vic tnh ton bo v chng st nh trc tip vo trm bin p t ngoi tri l rt quan trng . Ta c th a ra nhng phng n bo v trm mt cch an ton v kinh t, nhm m bo ton b cc thit b trong trm c bo v an ton khng b st nh trc tip. Ngoi vic chng st nh trc tip vo cc thit b trong trm ta cng phich n vic bo v cho cc on ng dy gn trm v on dy dn ni t x cui cng ca trm n ct u ra ct u tin ca ng dy. bo v chng st nh trc tip vo trm bin p ngi ta dng h thng ct thu li, dy thu li. Cc ct thu li c th t c lp hoc trong nhng iu kin cho php c th t trn cc kt cu ca trm v nh my, cc ct n chiu sng bo v cho on y dn ni t x cui cng ca trm n ct ra u tin ca ng dy ta dng dy chng st. Tc dng ca h thng ny l tp trung in tch hng cho cc phng in st tp trung vo to ra vng an ton pha di h thng ny. Chiu cao ca ct thu li v cch btr ct thu li ph thucvotngmtbngtrm,cchbtrccthitb,caobovtheoyu cu. H thng ni t phi c cc dy tip a dn dng in st t kim thu n h thng ni t. nng cao tc dng ca h thng ny th tr s in tr ca b phn thu st phi nh tn dng in mt cch nhanh nht, m bo sao cho khi Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h22 cdnginstiquathinptrnbphnthustkhnglngy phng in ngc n cc phn t khc gn . in tr ni t ca h thng thu st ca cc trm bin p c cp in p khc nhau l khng ging nhau. Vi trm bin p c cp in p t 110 kV tr ln th h thng ni t chng st v h thng ni t an ton c th ghp chung. Ngoi ra khi thit k bo v chng st nh trc tip vo trm, bn cnh cc tiu chun v m bo v yu cu k thut ta cng cn quan tm n cc ch tiu v kinh t v m thut ca h thng. Thng thng gim vn u t v cng tn dng cao ca nhng trm binpvccnhmyintacgngtccctthulitrnccnchiu sng, trn cc kt cu ca trm, trn mi nh Ct thu li c lp t hn nn ch s dng khi khng tn dng c cc cao khc. 2)CC YU CU K THUT KHI TNH TON BO V CHNG ST NH TRC TIP VO TRM BIN P. Tt c cc thit b bo v cn phi c nm trn trong phm vi an ton ca h thng bo v. Tu thuc vo mt bng trm v cc cp in p m h thng ccct thu stc tht trn cc cao snccacng trnh nhx,ctn chiu sng hoc t c lp. Khi t h thng thu st trn bn thn cng trnh, s tn dng c cao sn c ca cng trnh , do s gim c cao ca h thng thu st. Nhng khi c phnginst,dnginstsgynninpgingtrnintrnitv trn phn in cm thn ct, tr s in p ny kh ln v c th gy phng in ngc t h thng thu st ti cc b mang in nu cch in gia chng khng chuni.Doiukinththngthusttrncngtrnhmanginl phi m bo mc cch in cao v tr s in tr tn ca b phn ni t b. i vi trm bin p ngoi tri t 110 kV tr ln do c cch in cao (khong cch cc thit b ln v di chui s ln) nn c th t ct thu st trn cc kt cu ca trm. Tuy nhin cc tr ca kt cu trn c t ct thu st th phi ni t vo h thng ni t ca trm phn phi. Theo ng ngn nht sao cho Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h23 dng in st khuych tn vo t theo 3 - 4 cc ni t. Ngoi ra mi tr ca kt cu y phi c ni t b xung ci thin tr s ca in tr ni t m bo in tr khng qu 4 . Ni yu nht ca trm bin p ngoi tri l cun dy my bin p. V vy khi dng chng st van bo v my bin p th yu cu khong cch gia hai im ni vo h thng ni t ca h thng thu st v v my bin p theo ng in phi ln hn 15m. Khi t cch ly gia h thng thu st v cng trnh phi c khong cch nht nh,nukhongcchnyqu bthvnckhnngphng introngkhng kh cng nh trong t t h thng thu st ti cng trnh v nh vy cng khng km nguy him so vi khi st nh thng vo cng trnh. Tit din cc dy dn dng in st phi ln m bo tnh n nh nhitkhi c dng in st chy qua. Khi s dng ct chiu sng lm ga cho ct thu li th cc dy dn in phi c cho vo ng ch v chn trong t. 3)PHM VI BO V CA H THNG THU ST. 3.1) Phm vi bo v ca mt ct thu st c lp. Phm vi bo v ca mt ct thu st l min gii hn bi mt ngoi ca hnh chp trn xoay c ng sinh xc nh bi phng trnh: ( )x xx1,6r = h - hh1 +h Trong : h cao ct thu st. rx bn knh ca phm vi bo v mc hx. hx cao ca vt cn c bo v. ( h hx) cao hiu dng ca ct thu st. d dng thun tin trong tnh ton thit k, thng dng phm vi s dng dng n gin ho (hnh v). ng sinh ca hnh chp c dng ng gy khc a,b,c , mt trong cc on ca n on ab l phn ng thng ni nh ct Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h24 thusttiimtrnmttcchchnct0,75h,cnonkiaonbcl phn ng thng ni gia im cao 0,8h trn thn ct ti im cch xa chn ct 1,5h. T hnh v c th thy, im b c cao 2h3. Bn knh bo v cc mc cao khc nhau c tnh ton theo cng thc sau y: xx xh 2Khih h r = 1,5h 1-3 0,8h| |s |\ . xx xh 2Khih h r = 0, 75h 1-3 h| |> |\ . Cccng thc trnch ngkhict thustcao di 30m.Hiu qucact thu st cao trn 30mgim i do cao nh hng ca st gi hng s. C th dng cc cng thc trn tnh ton phm vi bo v nhng phi nhn thm h s hiu chnh 5,5p =h v trn honh ly cc gi tr 0,75hp v 1,5hp. OOabcrx0,75h1,5hhx23h0,8hhBi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h25 3.2) Phm vi bo v ca hai v nhiu ct thu st a)Phm vi bo v ca hai ct thu st c cng cao. Phmvibovcahaictthustckchthclnhnnhiusovitng phmvibovcahaictn.Nhtrnthykhuvccxcxut100% phng in vo ct thu st c bn knh R = 3,5h. Nh vy khi hai ct thu st t cch nhau a = 2R = 7h th bt k im no trn mt t trong khong gia hai ct s khng b st.T suy ra nu hai ct thu st t cch nhau khong cch a < 7h th s bo v c cao h0 xc nh bi: 0ah = h -7 RO1 O3 O2O1 O3O2hx23h0,8hh0,75ho1,5ho0,75h1,5h1 2horx1rOxrx2Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h26 Cc phn bn ngoi ging nh ca trng hp mt ct cn phn bn trong c gii hn bi vng cung i qua ba im: Hai nh ct v im gia c cao h0. Mt ct thng ng ct theo mt phng vung gc t gia hai ct ca phm vi bo v c v ging nh ca mt ct c cao h0 cho hx. Bn knh bo v ca tng ct : rx1 = rx2 = rx Bn knh bo v gia hai ct: xx 0 0x 00h 2Khih h r = 1,5h 1-3 0,8h| |s |\ . xx 0 0x 00h 2Khih h r = 0,75h 1-3 h| |> |\ . b)Phm vi bo v ca hai ct thu st khng cng cao. Phm vi bo v ca hai ct thu li c cao khc nhau c xc nh nh sau: Gi s c hai ct thu li :Ct 1 c cao h1 Ct 2 c cao h2 Khong cch gia hai ct l a v h1 > h2 Trctintavphmvibovcacth1,sautnhct2vng thng ngang gp ng sinh ca phm vi bo v ca ct 1 ti im 3. im ny c xem l nh mt ct thu st gi nh, n s hp vi ct 2 thnh i ct thu st c cao bng nhau (h2) vi khong cch a Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h27 '0 2a h = h -7 D dng nhn thy khong cch t ct 1 n ct gi tng 3 chnh l bn knh bo v ca ct cao h1 i vi chiu cao cn bo v l h2. Do tnh khong cch x gia ct 1 v ct 3 l: 22 1 11h 2Khih h x = 1,5h 1-3 0,8h| |s |\ .

22 1 11h 2Khih h x = 0,75h 1-3 h| |> |\ .

T ta tnh c a = a xvBi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h28 T ta tnh c bn knh bo v r0x xx 0 0x 00h 2Khih h r = 1,5h 1-3 0,8h| |s |\ . xx 0 0x 00h 2Khih h r = 0,75h 1-3 h| |> |\ . c)Phm vi bo v ca nhiu ct thu st. Khicngtrnhcncbo vchimkhuvcrngln,nuch dngmtvi ct thu th ct phi rt cao gy nhiu kh khn cho thi cng lp gip. Trong cc trng hp ny s dng nhiu ct phi hp bo v. Phn ngoi ca phm vi bo v c xc nh nh ca tng i ct. Khng cn v phm vi bo v bn trong a gic hnh thnh bi cc ct thu st m ch kim tra iu kin bo v an ton. Vt c cao hx nm trong a gic s c bo v nu tho mn iu kin: D 8 ( h hx ) = 8ha Trong :D:Lngknhngtrn ngoitipcaagicc hnh thnh bi cc ct thu st. hx: Chiu cao cn bo v. h: Chiu cao ct thu st. ha: Chiu cao hiu dng ca ct thu st. Phm vi bo v ca 3 ct thu st Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h29 Phm vi bo v ca 4 c thu st 4)CC PHNG N CM CT THU ST. Davosphttrinchngcatiatinost,ngitadngcch thng thu st l cc ct thu st c cao ln v in tr b thu ht cc phng in st to khu vc an ton xung quanh n. H thng thu st c b thu st l kim thu st v b phn tn dng in l h thng ni t. Theo d liu ca trm th mi ch bit din tch mt bng m cha bit c th v tr t cc thit b trong trm. Vi thng tin ny ta ch cn b tr ct chng st sao cho cc ct c th bo v c phn din tch mt bng ca trm vi cao hx l c. Yu cu: Chn cao ca ct thu st sao cho bo v c st nh trc tip ton trm.Ctthustc ni vi h thngnitcatrmtheongngn nhtsaochodnginst(Is)khuychtnvottheo3-4thanhcicah thng ni t. Vi trm bin p c hai cp in p U = 220/110 kV. Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h210 Kch thc trm: 12l = 64+132 = 196 ml = 79 m Din tch trm: S = l1.l2 = 196 . 79 = 15484m2 Vi kt cu trm ta a ra hai phng n cm ct thu st nh sau: 4.1) Phng n 1. S mt bng trm v cch b tr cc ct thu li nh hnh v. Phng n ny ta s dng 18 ct thu st. Do pha cao p (220 kV) c cao hx ln hn pha h p (110 kV) do ta cc ct thu st c b tr dy hn. Ta tin hnh tnh ton chiu cao ca cc ct v phm vi bo v ca h thng: 4.1.1) cao hiu dng ca cc ct thu li. tnh c cao hiu dng ha ca cc ct thu li, trc ht cn xc nh ng knh ng trn ngoi tip D ca cc tam gic (hoc t gic) c nh l v tr cm cc ct thu li. cho ton b phn din tch gii hn bi tam gic hoc t gic c bo v th phi tho mn iu kin: a aDD 8h hay h8s > Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h211 -Trm 220 kV: ng knh ng trn ngoi tip ca cc nhm ct (1, 2, 11, 12), (2, 3, 10, 11), (10, 11, 14, 15), (11, 12, 13, 14) l: 2 2D = 32 +39,5 50,836 (m) ~ Dotonbdintchgiihnbiccnhmtgicnycbovth chiu cao hiu dng ti thiu ca cc ct thu st ny l: aD 50,836h = = = 6,355 (m)8 8 -Trm 110 kV: ng knh ng trn ngoi tip ca cc nhm ct (3, 4, 9, 10), (4, 5, 8, 9), (5, 6, 7, 8), (7, 8, 17, 18), (8, 9, 16, 17), (9, 10, 15, 16) l: 2 2D = 44 +39,5 59,129 (m) ~ Dotonbdintchgiihnbiccnhmtgicnycbovth chiu cao hiu dng ti thiu ca cc ct thu st ny l: aD 59,129h = = = 7,391 (m)8 8 4.1.2) Chiu cao ca cc ct thu li. cao ct thu li h dng bo v chng st nh trc tip vo trm bin p c xc nh bi: h = hx + ha Trong :+ h: Chiu cao ct thu li. + hx: Chiu cao cn bo v. + ha: Chiu cao hiu dng ca ct thu li. -Trm 220 kV: i vi trm 220 kV th hx = 16,5m , do cao ti thiu ca ct thu li l: h = hx + ha = 16,5 + 6,355 = 22,855 (m) -Trm 110 kV: i vi trm 110 kV th hx = 11,5m , do cao ti thiu ca ct thu li l: h = hx + ha = 11,5 + 7,391 = 18,891 (m) Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h212 m bo cho tnh ton vng bo v c n gin v chnh xc v m bo d tr ct trong kho l t chng loi ta chn c 18 ct thu st cng cao l h = 23 (m). 4.1.3) Tnh ton v v phm vi bo v ca cc ct thu st. a) Trm cp in p 220 kV. -Bn knh ca khu vc bo v ca ct chng st c cao h = 23(m) cho cao cn bo v hx = 16,5 (m) l: xxh 16,5r = 0,75h.(1 - ) = 0,75.23.(1 - ) = 4,875 (m)h 23 ( V hx = 16,5 (m) > 2/3h = 2/3 . 23 = 15,333 (m) ) - cao ln nht ca khu vc bo v gia cc cp thu li (1, 2), (2, 3), (10, 11), (11, 12), (13, 14), (14, 15) l: 0a 32h = h - = 23 - = 18,429 (m)7 7 Do,bnknhcakhuvcbovgiahaictthust(1,2),(2,3),(10,11), (11, 12), (13, 14), (14,15) cao hx = 16,5 (m) l: x0x 00h 16,5r = 0,75h .(1 - ) = 0,75.18, 429.(1 - ) = 1, 447 (m)h 18, 429 ( V hx = 16,5 (m) > 2/3h0 = 2/3 . 18,429 = 12,286 (m) ) - cao ln nht ca khu vc bo v gia cc cp thu li (1, 12), (2, 11), (3, 10), (12, 13), (11, 14), (10, 15) l: 0a 39,5h = h - = 23 - = 17,357 (m)7 7 Do , bn knh ca khu vc bo v gia hai ct thu st (1, 12), (2, 11), (3, 10), (12, 13), (11, 14), (10, 15) l: x0x 00h 16,5r = 0,75h .(1 - ) = 0,75.17, 357.(1 - ) = 0, 643 (m)h 17, 357 ( V hx = 16,5 (m) > 2/3h0 = 2/3 . 17,357 = 11,571 (m) ) b) Trm cp in p 110 kV. Bi tp di mn k thut cao p Nguyn Trng Tun _ Lp D2-h213 -Bn knh ca khu vc bo v ca ct chng st c cao h = 23(m) cho cao cn bo v hx = 11,5 (m) l: xxh 11,5r = 1,5h.(1 - ) = 1,5.23.(1 - ) = 12, 938 (m)0,8h 0,8.23 ( V hx = 11,5 (m) < 2/3h = 2/3 . 23 = 15,333 (m) ) - cao ln nht ca khu vc bo v gia cc cp thu li (3, 4), (4, 5), (5, 6), (7, 8), (8, 9), (9, 10), (15, 16), (16, 17), (17, 18) l: 0a 44h = h - = 23 - = 16,714 (m)7 7 Do , bn knh ca khu vc bo v gia hai ct thu st (3, 4), (4, 5), (5,6), (7, 8), (8, 9), (9, 10), (15, 16), (16, 17), (17, 18) cao hx = 11,5 (m) l: x0x 00h 11,5r = 0, 75h .(1 - ) = 0, 75.16, 714.(1 - ) = 3, 911 (m)h 16, 714 ( V hx = 11,5 (m) > 2/3h0 = 2/3 . 16,714 = 11,143 (m) ) - cao ln nht ca khu vc bo v gia cc cp thu li (3, 10), (4, 9), (5, 8), (6, 7), (7, 18), (8, 17), (9, 16), (10, 15) l: 0a 39, 5h = h - = 23 - = 17,357 (m)7 7 Do , bn knh ca khu vc bo v gia hai ct thu st (3, 10), (4, 9), (5,8), (6, 7), (7, 18), (8, 17), (9, 16), (10, 15), cao hx = 11,5 (m) l: x0x 00h 11,5r = 1, 5h .(1 - ) = 1, 5.17, 357.(1 - ) = 4, 473 (m)0,8h 0,8.17, 357 ( V hx = 11,5 (m) < 2/3h0 = 2/3 . 18,429 = 12,286 (m) ) T kt qu tnh ton v phm vi bo v ca cc ct trn ta c bn v phm vi bo v nh sau: