Cu Hi Rle Bo V 1. Cng dng v cc yu cu ca rle? 2. Ch danh mt s chc nng rle bo v ang s dng? 3. Th no l bo v chnh, th no l bo v d phng? 4. Lit k cc rle bo v cho my bin p? 5. Lit k cc rle bo v thanh ci? 6. Lit k cc rle bo v cho ng dy? 7. Nu cu to ca rle hi? 8. Nu cu to ca rle nhit ti MBA? 9. Nu cu to ca rle mc du ti MBA? 10. Nguyn l lm vic ca rle bo v qu dng ct nhanh? Nguyn tc chnh

nh ca rle bo v ? 11. Nguyn l lm vic ca rle bo v qu dng ct c thi gian ? Nguyn tc

chnh nh ca rle bo v ? 12. Nguyn l lm vic ca rle km p? Nguyn tc chnh nh ca rle bo v ? 13. Nguyn l lm vic ca rle bo v so lch dc? Nguyn tc chnh nh ca

rle bo v ? 14. Nguyn l chn lm vic ca rle bo v so lch ngang? Nguyn tc chnh

nh ca rle bo v ? 15. Nguyn l lm vic ca bo v khong cch (bo v tng tr) ? Nguyn tc

chnh nh ca rle bo v ? 16. Nguyn l lm vic ca rle qu dng c hng ? Nguyn tc chnh nh ca

rle bo v ? 17. Nguyn l lm vic ca rle t ng ng li? Nguyn tc chnh nh ca

rle bo v ? 18. Nguyn l lm vic ca rle kha? 19. Nu cc chc nng ca cc loi rle k thut s hin c ca Nh my cho cc

loi rle bo v : a. Rle khong cch b. Rle qu dng c. Rle so lch

20. Cch khai thc thng tin trn cc loi rle k thut s ti Nh my (thao tc c s c)

21. Ti sao phi t thit b t ng li trn ng dy? 22. Quy trnh vn hnh cc rle bo v k thut s mt s hng nc ngoi ang

lp t ti trm 110kV Nhn C?

Tr Li 1. Cng dng v cc yu cu ca rle:

a- Cng dng: Trong qu trnh vn hnh h thng in c th xut hin tnh trng s c v ch

lm vic bt thng ca cc phn t. Cc s c thng km theo hin tng dng in tng kh cao v in p gim thp. Cc thit b c dng in tng cao chy qua c th b t nng qu mc cho php v b hng. Khi in p gim thp, cc h tiu th khng th lm vic bnh thng v tnh n nh ca cc my pht lm vic song song v ca ton h thng b gim. Cc ch lm vic khng bnh thng lm cho in p, dng in v tn s lch khi gii hn cho php. Nu ko di tnh trng ny, c th xut hin s c. Mun duy tr hot ng bnh thng ca h thng v cc h tiu th khi xut hin s c, cn pht hin cng nhanh cng tt ch s c v cch ly n ra khi phn t b h hng, nh vy phn cn li duy tr c hot ng bnh thng, ng thi gim mc h hi ca phn t b s c. Ch c thit b t ng bo v mi c th thc hin tt c yu cu trn, thit b ny gi l bo v rle.

Bo v rle s theo di lin tc tnh trng v ch lm vic ca tt c cc phn t trong h thng in. Khi xut hin s c, bo v rle pht hin v ct phn t h hng nh my ct in. Khi xut hin ch lm vic khng bnh thng, bo v rle s pht tn hiu v ty thuc yu cu, c th tc ng khi phc ch lm vic bnh thng hoc bo tn hiu cho nhn vin trc.

b - Cc yu cu c bn i vi bo v rle: * Tnh chn lc: Tnh chn lc l kh nng phn bit cc phn t h hng v bo v ch ct cc

phn t . V d trong s bo v nh hnh 1, khi ngn mch ti im N1, my ct MC3

l my ct gn ch s c nht phi ct. Nh vy cc ph ti khc vn c cung cp in. Khi ngn mch ti im N2, ng dy s c A2-B2 c ct ra nh cc my ct MC1 v MC2, cn ng dy A1-B1 vn lm vic, v vy ton b cc h tiu th vn c cung cp in.

Tnh chn lc l yu cu c bn nht ca bo v rle m bo cung cp in an ton lin tc. Nu bo v tc ng khng chn lc, s c c th lan rng.

* Tc ng nhanh: Bo v phi tc ng nhanh kp thi c lp cc phn t h hng thuc phm

vi bo v nhm: + m bo tnh n nh ca h thng. + Gim nh hng ca in p thp (khi ngn mch) ln cc ph ti. + Gim tc hi ca dng in ngn mch i vi thit b. Bo v tc ng

nhanh phi c thi gian tc ng nh hn 0,1 giy. * nhy: Bo v cn tc ng khng ch vi cc trng hp ngn mch trc tip m c

khi ngn mch qua in tr trung gian. Ngoi ra bo v phi tc ng khi ngn mch

xy ra trong lc h thng lm vic ch cc tiu, tc l mt s ngun c ct ra nn dng ngn mch c gi tr nh. nhy c nh gi bng h s nhy:

Knh=INmin/Ik . INmin : dng in ngn mch nh nht. . Ik: gi tr dng in nh nht m bo v c th tc ng. i vi cc bo v tc ng theo gi tr cc tiu (v d bo v thiu in p),

h s nhy c xc nh ngc li: tr s khi ng chia cho tr s cc tiu. * tin cy: Bo v phi tc ng chc chn khi xy ra s c trong vng c giao v

khng c tc ng sai i vi cc trng hp m n khng c nhim v tc ng. Mt bo v khng tc ng hoc tc ng sai c th s dn n hu qu l mt

s ln ph ti b mt in hoc s c lan rng trong h thng. 2. Cc ch danh ca rle ang s dng. - 21: rle khong cch. - 25: rle ng b. - 26: rle nhit . - 27: rle thiu p. - 32: rle cng sut ngc. - 33: rle mc du. - 50, 51: rle qu dng tc th, nh th. - 55: rle h s cng sut. - 59: rle qu p. - 62: rle thi gian. - 63: rle p sut. - 64: rle chm t. - 67: rle qu dng c hng. - 79: rle t ng li. - 81: rle tn s. - 85: rle so lch cao tn. - 86: rle kha. - 87L: rle so lch dc. - 96: rle hi. Ty theo phm vi, mc v i tng c bo v, ch danh rle c th c

phn m rng. Sau y l mt s ch danh rle c phn m rng thng dng: - 26W: rle nhit cun dy my bin p; 26O: rle nhit du. - 51P, 51S rle qu dng in pha s cp, th cp my bin p. - 50REF: rle qu dng tc th chng chm t trong thit b (thng dng cho

my bin p). - 67N: rle qu dng chm t c hng. - 87T: rle so lch dc in bo v my bin p, 87B: rle so lch dc bo v

thanh ci.

- 96-1: rle hi cp 1 dng bo tn hiu; 96-2: rle hi cp 2 tc ng ct my ct.

3. Th no l bo v chnh, bo v d phng ? Bo v chnh trang thit b: l bo v thc hin tc ng nhanh khi c s c

xy ra trong phm v gii hn i vi trang thit b c bo v. Bo v d phng i vi cng trang thit b ny l bo v thay th cho bo v

chnh trong trng hp bo v chnh khng tc ng hoc trong tnh trng sa cha nh. Bo v d phng cn phi tc ng vi thi gian ln hn thi gian tc ng ca bo v chnh, nhm cho bo v chnh loi phn t b s c ra khi h thng trc tin (khi bo v ny tc ng ng).

Bo v d phng: c th c m bo theo cc cch sau: - Bo v ca phn t bn cnh (trng hp ny c mang tn l bo v d

phng xa). - Bo v ph t trn cng phn t (trng hp ny c mang tn l bo v

d phng ti ch). - Mt rle ph a vo trong s bo v cho phn t bn cnh, rle ny s

iu khin m my ct c quan tm. C mt s trng hp bo v chnh khng m bo c ton b chiu di ca

mch cn c bo v m s c mt s on c gi l vng cht ca bo v chnh. Nu xut hin s c ti vng cht ny, bo v chnh s khng tc ng. c th bo v ti vng ny, thng phi t bo v d phng.

4. Lit k cc rle bo v my bin p ? a- Cc rle tc ng theo dng in: - Rle bo v qu dng in pha s cp: 50/51P pha, chm t. - Rle bo v qu dng in pha th cp: 50/51S pha, chm t. - Rle bo v so lch dc dng in: 87T. - Rle bo v qu dng in cc dy trung tnh: 50/51G. - Rle bo v chm t cc cun dy: 50REF. b- Cc rle khng tc ng theo dng in: - Rle hi: 96. - Rle nhit du: 26O. - Rle nhit cun dy: 26W. - Rle mc du thn my: 33. - Rle p sut thn my, b i nc di ti: 63. 5. Lit k cc rle bo v thanh ci ? - Rle so lch dc dng in: 87B. - Rle thp p: 27. - Rle qu p: 59. - Rle chng chm t: 64.

6. Lit k cc rle bo v ng dy ? - Rle qu dng tc th, nh th: 50/51L pha, chm t. - Rle so lch pha cao tn: 85. - Rle qu dng c hng (pha, chm t): 67, 67N. - Rle khong cch: 21. 7. Cu to rle hi ? Rle hi c p dng cho cc my bin p c cng sut trung bnh v ln vi

kiu my c thng gin n du. Rle hi c lp trn on ng lin thng du t thng chnh my bin p n thng gin n du ca my theo mt chiu nht nh ca u mi tn trn rle hi phi ch v pha thng gin n (cng vi chiu dng chy ca du t thng chnh qua rle hi n thng gin n du khi c s c trong my bin p). an ng lin thng du c nng cao v pha thng gin n vi gc nghing (so vi mt phng ngang) khong 1 100. on ng lin thng khng c c gc, phn cong ca ng c bn knh cng ln cng tt.

Rle hi hai phao c cu to gm :

Nguyn l cu to (a) v v tr b tr trn MBA ca rle hi (b)

- Mt phao trn (phao 1) c hnh cu rng, nh c th t nng h theo mc du, trong phao c cha mt tip im thy ngn c ni ra hp ni dy ti mt trn rle. Khi s c nh hoc qu ti, hi sinh ra tp trung pha trn, y phao 1 v v tr nm ngang lm ng tip im thy ngn. Tip im ny c ni vo mch in bo hiu s c ca my bin p (96-1).

- Mt phao di (phao 2) c cu to tng t nh phao 1 v c lin kt vi mt cnh chn. Cnh chn l mt tm kim loi mng c treo ti v tr pha l mt bch ca rle hi pha ni vo thng chnh my bin p. Do c treo b mt tm kim loi thng gc vi hng dng chy ca du nn cnh chn tc ng theo lu lng ca dng chy ca du. Cnh chn c th iu chnh theo ba tr s lu lng du l 65, 100 v 150 cm/giy (rle thng c nh ch to t sn tr s 100cm/giy). Khi my bin p vn hnh bnh thng, du chuyn ng do gin n theo nhit khng tc ng cnh chn. Khi c s c bn trong my bin p, lung du v hi sinh ra pht mnh t thng chnh qua rle hi n thng gin n.

Lu lng du ln hn tr s iu chnh sn s y cho cnh chn quay, lm cho phao 2 chm xung, ng tip im thy ngn, ct my ct (96-2).

Da vo thnh phn v khi lng hi sinh ra ngi ta c th xc nh c tnh cht v mc s c. Do trn rle hi cn c thm van ly hn hp kh sinh ra nhm phc v cho vic phn tch s c.

8. Cu to rle nhit ti my bin p ? a- Rle nhit du : Rle nhit du gm cc tip im thng ng, thng m lp bn trong

mt nhit k c kim ch th nhit . Nhit k gm c c cu ch th quay ghi s o, mt b phn cm bin nhit, mt ng mao dn ni b phn cm ng nhit vi c cu ch th. Bn trong ng mao dn l cht lng (dung dch hu c) c nn li. S co gin ca cht lng (trong ng mao dn) thay i theo nhit m b phn cm bin nhit nhn c, s tc ng c cu ch th v cc tip im. Cc tip im s i trng thi "m" thnh "ng", "ng" thnh "m" khi nhit cao hn tr s t trc. B phn cm bin nhit c lp trong mt l tr bc kn, pha trn np my bin p, bao quanh l tr l du, o nhit lp du trn cng ca my bin p. Thng dng nhit k c 2 (hoc 4) vt iu chnh nhit c th t sn 2 (hoc 4) tr s tc ng cho 2 (hoc 4) b tip im ring r lp trong nhit k. Khi nhit cao hn tr s t cp 1, rle s ng tip im cp 1 bo hiu s c "Nhit du cao" ca my bin p. Khi nhit tip tc cao hn tr s t cp 2, rle s ng thm tip im cp 2 t ng ct my ct, ct in my bin p, ng thi cng c mch in bo hiu s c "ct do nhit du cao".

b-Rle nhit cun dy:

Rle nhit cun dy gm bn b tip im (mi b c mt tip im thng m, mt tip im ng vi cc chung) lp bn trong mt nhit k c kim ch th. Nhit k gm c: c cu ch th quay ghi s o, mt b phn cm bin nhit, mt ng mao dn ni b phn cm bin nhit vi c cu ch th. Bn trong ng mao dn l cht lng c nn li. S co gin ca cht lng trong ng mao dn thay i theo nhit m b cm bin nhn c, tc ng c cu ch th v bn b tip im. Tc ng ln c cu ch th v cc tip im, cn c mt in tr nung. Cun dy th cp ca mt my bin dng in t ti chn s my bin p c ni vi in tr nung. Ni song song vi in tr nung l mt bin tr hiu chnh. Tc dng ca in tr nung (ty theo dng in qua cun dy my bin p) v tc dng ca b cm bin nhit ln c cu o cng cc b tip im s tng ng vi nhit im nng: nhit ca cun dy.

C 4 vt iu chnh nhit t tr s tc ng cho bn b tip im. Ty theo thit k, cc tip im rle nhit c th c ni vo cc mch: bo hiu s c "nhit cun dy cao", mch t ng m my ct c lp my bin p, mch t ng khi ng v ngng cc qut lm mt my bin p.

9. Cu to rle mc du ti my bin p?

Rle mc du gm hai b tip im lp bn trong thit b ch th mc du. My bin p c b di nc in p c ti th thng gin n du c chia lm hai ngn. Ngn c th tch chim phn ln thng gin n, c ni ng lin du thng qua rle hi n thng chnh my bin p ( c th tch gin n du cho my bin p). Ngn c th tch chim phn nh hn nhiu ca thng gin n, s c ni ng lin du n thng cha b i nc c ti. Thng chnh my bin p v thng b i nc c thit k ring r, khng c lin thng du vi nhau. V vy, c hai thit b ch th mc du lp ti hai u thng gin n o mc du ca hai ngn: thit b ch th mc du my bin p v thit b ch th mc du b i nc c ti.

Cu to ca thit b ch th mc du gm hai phn : b phn iu khin v b ch th.

B phn iu khin c mt phao (3), thanh quay (8), trc quay (9), c lp nam

chm vnh c (4). B phn iu khin lp trn v my (u thng gin n) c vng m. B phn ch th gm kim ch (6) lp trn trc mang mt nam chm vnh cu (5). B phn ch th c lm bng nhm trnh b nh hng t trng nam chm v chng nh hng ca nc.

Khi mc du nng h th phao (3) nng h theo. Chuyn ng nng h ca phao c chuyn thnh chuyn ng quay ca trc (9) nh thanh quay (8). Khi quay, t trng do nam chm (4) s iu khin cho nam chm (5) quay sao cho hai cc khc tn (N v S) ca hai nam chm i din nhau (hai cc cng tn c lc y, hai cc cng tn c lc ht nhau). Do vy kim ch th quay theo nam chm (5), ghi c mc du trn mt ch th.

B phn ch th cng tc ng ng m cc tip im rle mc du a tn hiu vo mch bo ng hoc mch ct ty theo tng thit k.

10. Nguyn l lm vic ca rle qu dng tc th (Bo v qu dng ct

nhanh - ngng cao)? Rle qu dng tc th l rle tc ng khi dng in qua rle vt qu tr s

nh trc v tc ng ct my ct ngay lp tc, khng c thi gian tr hon. V nguyn l rle qu dng tc th gm phn tnh l cun dy c li st, phn ng

l tm st non c mang tip im ng. Khi dng in qua cun dy ln, tm st non s b ht vo li st ca phn tnh v ko theo tip im ng ng vo tip im tnh.

iu chnh dng in tc ng theo mun, thng thng phn ng c gn vi mt l xo vi kt cu c th iu chnh c nhm thay i lc tc ng ln phn ng, c ngha l thay i dng in tc ng ca rle.

Mt s trng hp, thay i dng in tc ng trong phm v rng, ngi ta thng ch to cun dy phn tnh c nhiu on vi nhiu u dy ra chn tm t thch hp.

Nguyn tc chnh nh rle qu dng tc th ? Chnh nh rle qu dng tc thi l t tr s dng in khi ng ca rle. m bo tnh chn lc, trnh tc ng sai khi ngn mch ngoi vng c

bo v, dng in khi ng c chn theo quy tc sau: Ik = Kat . INmax

Trong : INmax: dng in ngn mch cc i cui vng bo v. Kat = 1,2 - 1,3 : h s an ton tnh n sai s trong khi tnh ton dng ngn

mch v sai s rle. Ik : dng in khi ng ca rle. Vng tc ng c xc nh bng cng thc: XCN% = Trong : XCN - Vng tc ng ca bo v, tnh bng phn trm ca ton b ng dy c bo v (%). Xl : tr khng ca ng dy c bo v (%). XH : tr khng ca h thng (%). Ik : dng khi ng ca bo v (%). 11. Nguyn l lm vic ca rle qu dng nh thi (bo v dng in cc

i)? Gm c hai loi: a) Bo v qu dng c c tuyn c lp: c tuyn c dng ng thng, khi

dng s c ln hn dng t sau thi gian tr rle a tn hiu ct my ct (thi gian ct khng i ch cn dng bv ln hn dng dt => ct)

b) Bo v qu dng c c tuyn thi gian ph thuc: - c tuyn c dng cong, khi dng s c cng ln hn dng t th thi gian

gi tn hiu ct cng ngn - C ba dng c tuyn thng c s dng:

Loi c tuyn Tiu chun H s K H s

Standard inverse IEC 0.14 0.02

Very inverse IEC 13.5 1

Extremely inverse IEC 80 2

- Cng thc tnh thi gian tc ng ca cc c tuyn r le: t= TD*(

(/0))(s) t: thi gian tc ng ca r le K: h s I: dng qua r le Is: dng khi ng ci t trong r le : h s TD: h c tuyn (ty theo tng loi r le) - Dng khi ng ca r le qu dng cc i cn m bo: + Dng in khi ng: Ik > Ilvmax + R le dng in phi tr v mt cch chc chn sau khi ngn mch xy ra

Ik= (Kat/Ktv)*Ktk*Ilvmax/nct Kat: h s an ton tnh n sai s c th c ca dng tr v ca r le: 1,1-1,2

Kat: h s tr v ca r le ( Kat

1- Dng in khi ng ca rle Ik: c xc nh t dng in lm vic cc i, thng l dng ph ti trong ch cc i:

Ik > Ilvmax v phi tha: Ik = Kmm . Kat. Ks . Ilvmax / Ktv. KBI Trong : . Ilvmax l dng in lm vic cc i. . Kmm = 2 3 l h s m my ph thuc vo ng c in. . Kat = 1,2 1,3 l h s an ton khi k n vic tnh ton sai s ca rle v

my bin dng. . Ks l h s ca s , ph thuc vo s u ni rle. . Ktv l h s tr v ca rle. . KBI l h s bin i ca my bin dng. 2- Thi gian tc ng ca bo v: m bo tnh chn lc, thi gian tc ng ca bo v c chn theo

nguyn tc bc thang, chnh lch gia thi gian tc ng ca cc bo v k nhau c gi l bc thi gian hay bc chn lc:

Dt = t1 - t2 Gi tr ca bc thi gian Dt c chn sao cho khi ngn mch thuc phm vi

ca bo v sau, bo v trc khng kp tc ng mc d khi ng. nhy ca bo v:

Knhy = INMmin / Ik Thng thng nhy phi t trong khong 1,2 1,5. Trong : INMmin l dng in ngn mch b nht khu vc cui ca li c bo v. 12. Nguyn l lm vic ca rle km p ? Rle km p l rle tc ng khi in p t vo rle thp hn gi tr nh

trc. V nguyn l, rle km p cu to gm cun dy c li thp tc ng ln phn

ng mang tip im. Khi in p cun dy ln, phn ng b ht vo phn tnh v ng tip im. Khi in p t vo cun dy h thp di mt mc nh trc, cun dy khng ht v tip im nh ra. y l trng thi tc ng ca rle.

Nh vy, khc vi cc loi rle qu ngng, trng thi bnh thng ca rle km p l trng thi lun c in p. Trng thi tc ng l trng thi in p gim thp hoc khng c in.

Thng thng rle km p c thit k vi thi gian tr hon: Rle thc t gm mt phn t km p kt hp vi mt phn t to thi gian. Khi in p t vo rle gim di ngng nh trc, phn t km p s tc ng, cp ngun cho phn t thi gian. Sau thi gian t trc, tip im thi gian s ng v i ct my ct hoc bo tn hiu.

Rle km p c th thit k lm vic vi in p xoay chiu hoc mt chiu. Nguyn tc chnh nh rle km p? Chnh nh rle km p l thit t cc gi tr in p lm vic ca rle:

in p lm vic ca rle l in p cc tiu c xc nh theo cng thc sau:

Uk = Ulvmin / (Ktc . Ktv . KU) Trong : Ulvmin: in p lm vic cc tiu ch bnh thng. Ktc: h s tin cy. KU: h s ca my bin in p Ktv: h s tr v ca rle. nhy ca bo v:

Knhy = Ulv . KU / UNMmax Trong : UNMmax l tr s ln nht c th c ca in p d v tr t bo v khi ngn

mch khu vc cui cng c bo v. 13. Nguyn l lm vic ca rle so lch dc dng in? Rle so lch dc l rle lm vic da trn s so snh trc tip dng in trn

cc nhnh ca mt i tng. Theo nh lut Kirchoff, tng vct ca tt c cc dng in i vo v ra mt

i tng bo v bng khng trong iu kin lm vic bnh thng. Vng bo v ca rle so lch dc dng in l phm v gii hn bi cc bin

dng t trn cc nhnh ca i tng c bo v. Khi c ngn mch trong vng bo v, tng dng in i qua rle s khc khng

v rle s tc ng. Khi s c bn ngoi vng bo v, tng dng in qua rle vn bng khng, rle khng tc ng.

Rle so lch dc dng in thng c dng bo v cho cc thit b nh my bin p, my pht, h thng thanh ci quan trng... Rle tc ng ct cc my ct ch khi c s c ngn mch bn trong vng bo v.

Rle so lch dc dng in lm vic tc th, khng c thi gian tr hon. Nguyn tc chnh nh rle so lch dc dng in ? V nguyn tc, rle so lch dc dng in tc ng khi c dng in sai lch i

qua rle IR > 0. Tuy nhin thc t do s khng ng nht ca cc bin dng, s sai lch t s bin dng,... nn khi lm vic bnh thng dng in i qua rle vn c mt tr s nht nh. Dng in ny gi l dng khng cn bng Ikcb.

Trong trng hp ngn mch ngoi vng bo v, hoc trong cc tnh trng qu , dng in khng cn bng Ikcb c th c gi tr ln.

trnh bo v tc ng sai, dng in khi ng ca bo v phi chn sao cho:

Ik =Kat . Ikcbttmax. Trong : - Ik: dng in khi ng ca rle. - Kat >1: h s an ton, nhm trnh tc ng sai do cc sai s ca rle v mch. - Ikcbttmax: dng in khng cn bng tnh ton cc i. 14. Nguyn l lm vic ca rle so lch ngang dng in ?

Rle so lch ngang dng in l rle tc ng da trn s so snh trc tip dng in chy trn cc nhnh song song.

Bo v c dng cho ng dy c cc nhnh vn hnh song song hoc my pht vi stator cun dy kp.

Vng bo v l hai nhnh song song ca ng dy hoc cun stator my pht. V in tr ca hai nhnh ging nhau nn khi lm vic bnh thng hoc khi

ngn mch ngoi vng bo v, dng in trn hai nhnh s bng nhau: I1=I2

Do : IR=0. Rle khng tc ng. Khi c ngn mch mt trong hai nhnh, dng in trn cc nhnh s khc nhau:

I1 # I2 Khi dng in qua rle IR # 0. Rle tc ng ct my ct. Rle so lch ngang dng in lm vic tc th, khng c thi gian tr hon. Nguyn tc chnh nh rle so lch ngang dng in ? V nguyn tc, rle so lch ngang dng in tc ng khi c dng in sai lch

i qua rle IR > 0. Tuy nhin thc t do s khng ng nht ca cc bin dng cng nh do in tr cc nhnh khng hon ton bng nhau nn khi lm vic bnh thng dng in i qua rle vn c mt gi tr nht nh. Dng in ny gi l dng khng cn bng Ikcb.

Trong trng hp ngn mch ngoi vng bo v, hoc trong cc tnh trng qu , dng in khng cn bng Ikcb c th c gi tr ln.

trnh bo v tc ng sai, dng in khi ng ca bo v phi chn sao cho:

Ik =Kat . Ikcbttmax Trong : - Ik: dng in khi ng ca rle. - Kat >1: h s an ton, nhm trnh tc ng sai do cc sai s ca rle v mch. - Ikcbttmax: dng in khng cn bng tnh ton cc i. 15. Nguyn l lm vic ca rle tng tr ? Rle tng tr l rle tc ng theo tng tr on ng dy t im ngn mch

n ch t rle (u ng dy). Z = UNM/INM

Trong : - UNM: in p gin trn on ng dy t im s c n ch t rle. - INM: Dng in ngn mch i qua ch t bo v. Vng bo v ca rle tng tr l on ng dy c tng tr khng ln hn tr

s tng tr t ca rle. Rle tc ng khi:

Z > Z trong :

- Z : Tng tr on ng dy t im s c n ch t rle. - Z: Gi tr t ca rle. Cc s u dy thng dng rle tng tr: * S in p dy v hiu s dng in pha: * S in p dy v dng in pha: Rle tng tr c ch to c nhiu vng bo v khc nhau, thch hp cho bo

v cc ng dy c nhiu on. Trong trng hp ng dy c cung cp t hai pha, m bo tc ng

chn lc, thng s dng loi rle tng tr c hng nhm ch tc ng khi dng s c i theo hng t thanh ci ra ng dy.

Nguyn tc chnh nh rle tng tr ? Xt ng dy c s nh hnh: ng dy c bo v bng rle tng tr c 3 vng bo v. - Z1, Z2, Z3: tng tr bo v vng 1, 2, 3. - t1, t2, t3: thi tc ng ca bo v vng 1, 2, 3 ca rle 21 thuc my ct MC1. Khi ngn mch trn on AB (vng 1), i hi phi ct nhanh my ct MC1.

Do thi gian tc ng ca bo v vng 1 thng c chn bng khng: t1 = 0 sec.

bo v ton b chiu di on AB, v nguyn tc phi chn tr s t vng 1 sao cho Z1 = ZAB. Tuy nhin nu t nh vy th bo v vng 1 s tc ng sai lm ct my ct MC1 khi c ngn mch u ng dy on BC v tng tr tnh t my ct MC1 n cc im ngn mch cui on AB v u on BC l gn bng nhau. Do m bo tnh chn lc, thng ch chn phm vi bo v ca mi vng chim khong 3/4 chiu di on ng dy:

Z1= 0,75 ZAB. Khi ngn mch trn on BC, rle bo v ca on BC phi tc ng ct my

ct MC2. Nu do h hng, my ct MC2 khng ct th my ct MC1 phi ct c lp s c. Lc ny vng 2 ca rle 21 phi tc ng. Vy thi gian tc ng vng 2 s l:

t2 = max(t1 , tBC) + Dt = tBC + Dt2. Trong : - tBC : thi gian tc ng ca bo v chnh on BC. - Dt2: thi gian ct ca my ct MC2. Phm vi bo v ca vng 2 l:

Z2= 0,75 ZBC + ZAB. Nh vy bo v vng 2 ca on AB l bo v d tr cho bo v chnh ca

on BC. Tng t cho im ngn mch trn on CD:

Z3= 0,75 ZCD + ZBC. t3 = max(t2 , tCD) + Dt3.

trnh bo v tc ng sai khi c dao ng trn h thng, trong mt s trng hp (ty thuc vo kh nng gi n nh ca h thng) c th t thi gian tc ng vng 1 c mt tr s nht nh t1 > 0 ).

16. Nguyn l lm vic ca rle qu dng c hng ? ch to rle cng sut (rle qu dng c hng) ngi ta dng nguyn tc

so snh trc tip gc lch pha gia hai i lng in UR v IR hoc so snh tr s tuyt i ca hai i lng l t hp ca hai tn hiu UR v IR.

Rle nh hng cng sut lm vic theo nguyn tc so snh pha: Dng in IR v in p UR a vo h thng t c s i cc chn, li thp hnh tr bn trong lm gim t tr ca mch t v phn ng l mt ng hnh trng lm bng nhm hoc ng, cc cun in p v dng in qun trn tng i cc tng ng.

Mmen quay ca rle: Mq = KURIRcos(j + a) Trong : - UR, IR l in p v dng in t vo cc cun dy tng ng ca rle. - j l gc lch pha gia UR v IR. - K, a l cc thng s ph thuc vo cu to, mch t ca r le. Rle s tc ng khi Mq > 0 ngha l: Cos(j + a ) > 0 Hay l: - (90o + a) < j < (90o - a) Biu thc trn chng t rle tc ng (Mq > 0) khi gc lch pha j gia UR v

IR nm trong mt gii hn nht nh, ngha l khi cng sut theo mt hng nht nh.

Nguyn tc chnh nh rle c hng? a. Dng khi ng ca bo v: Dng khi ng ca bo v cn chn theo 2 iu kin sau: - Bo v phi tr v sau khi ngn mch ngoi c loi tr. Mun vy dng tr

v ca bo v phi ln hn dng ph ti ngay sau lc ct s c, khi cc ng c ng lot t khi ng.

IKB = Kat . Ilvmax (1) Trong : Ilvmax l gi tr dng in lm vic cc i (xc nh i vi ch lm vic

nng n nht). tng nhy ca bo v c th khng cn xt n ph ti cc i vi hng

t ng dy vo thanh gp, v i vi n rle cng sut khng khp tip im, v do bo v khng th tc ng sai. Khi mch in b h hng, pha ca in p a vo rle cng sut b mo, rle c th khp tip im.

Khi xy ra ngn mch chm t trong mng c im trung tnh trc tip ni t, trong pha khng h hng c th c dng s c v i vi dng ny rle khng c tc ng. Mun vy cn chn dng khi ng ln hn dng trong pha khng h hng.

IKB= Kat . IKH (2) trong : IKH= IPT + KIN Kat = 1,15 - 1,3 ty thuc vo chnh xc khi nh gi i lng IKH.

Dng in khi ng c chn l gi tr ln hn trong hai gi tr xc nh theo (1) v (2).

i vi mng c dng chm dt nh (IKH = IPT) v mng c trung im ni t trc tip nhng bo v c kha khi c ngn mch chm t th dng khi ng cn c chn theo iu kin (1).

b - Thi gian tc ng ca bo v: Thi gian tc ng ca bo v c chn theo nguyn tc bc thang ngc

chiu nhau. Theo yu cu tc ng chn lc, thi gian tc ng ca cc bo v trong cng

mt hng cn tha mn: t5 < t3 < t1 v t2 < t4 < t6.

c - nhy ca bo v: Knhy = INmin/Ik

INmin l dng in ngn mch cc tiu khi ngn mch cui vng bo v. Knhy min =1,2-1,5. Khi ngn mch cui vng d tr, yu cu Knhy min = 1,2. 17. Nguyn l lm vic ca rle t ng li ? Rle t ng li l rle lm nhim v ng li my ct sau khi my ct (ng

dy) b bt ra bi cc rle bo v khc (51, 21,...) nhm nhanh chng ti lp ng dy mt cch t ng khi c s c thong qua trn ng dy. Qu trnh ng li c th c thc hin mt hay nhiu ln. Thng thng rle t ng li c thit k cho 3 hoc 4 ln ng li. Mi ln ng li u c thi gian tr hon. Thi gian cc ln sau di hn ln trc. Nu ln ng li cui cng khng thnh cng, rle s t kha khng cho ng tip.

Nguyn tc chnh nh rle t ng li ? Chnh nh rle t ng li l t cc khong thi gian tr hon trc mi ln

ng li, s ln ng li v thi gian t khi phc. - S ln ng li: n. - Thi gian tr hon trc mi ln ng li: t1, t2, ... Cc khong thi gian ny c chn sao cho khi c s c thong qua, my ct

ngt mch v cch in ti ch b s c c thi gian phc hi trc khi ng in li. i vi cc ln ng li th 2, 3, ... thi gian tr hon trc khi ng li cn ph thuc vo chu trnh ng ct ca my ct c t rle.

- Thi gian t khi phc (treset): nu ng li ln cui khng thnh cng, rle t kha. Vic kha ny ch c tc dng trong thi gian nht nh. Sau rle phi t tr v trng thi sn sng lm vic nh trc khi s c.

18. Nguyn l lm vic ca rle kha ? Rle kha l rle khi tc ng, tip im s ng (hoc m) v sau khng

t tr v trng thi ban u d rle khng cn c cung cp in. a cc tip im v trng thi ban u, phi thc hin thao tc "reset" (bng tay hoc bng in).

Rle kha c dng ph bin trong cc mch bo v my bin p nhm ct v kha my ct khng cho ng li khi c s c nng.

19. Nu cc chc nng ca cc loi rle k thut s hin c ca Nh my

cho cc loi rle bo v ? Ti trm 110kV Nhn C:

a. My ct 171/172 gm: - 01 rle loi MICOM-P443 (c cc chc nng: 21, 79, 67, 67N), - 01 rle loi MICOM-P127 (c cc chc nng: 67, 67N, 50BF).

b. My ct 112 gm: - 01 rle MICOM-P127 (c cc chc nng: 50, 51, 50N, 51N, 50BF), - 02 rle MICOM-P922 (c cc chc nng: 27, 59).

c. MBA T1/T2 20MVA 110/6,3kV gm: - 01 rle loi MICOM-P632 (c chc nng : 87T), - 01 rle loi MICOM-P127 (c cc chc nng : 50, 51P, 50NP, 51NP, 50BF,

49).

Ti trm phn phi h p 6,3kV : a. My ct 631/632 gm:

- 01 rle loi Farad FM200-2A (c cc chc nng : A, V, W, Var, F, PF). b. My ct 612/613/623 gm:

- 01 rle loi Farad FM762A (c cc chc nng: 50,51, A, V, W, Var, F, PF). c. My pht in G1/G2 15MW 6,3kV gm:

- 01 rle loi Farad FM782 (c chc nng: 87), - 01 rle loi Farad FM783 (c cc chc nng: 51V, 64G, 40, 46, 59, 27), - 01 rle loi Farad FM780 (c cc chc nng: 64R, 40), - 01 rle o m in p loi Farad FM509 (c cc chc nng: A, V, W, Var,

F, PF). d. Cc l phn phi cho PD1, 2, 3, 4, 5 gm:

- 01 rle loi Farad FM711A (c cc chc nng: 50, 51, 51N). Cc bo v t dng gm:

a. Bo v ng c FM 771 - 50, 51, 51N; - Qu dng th t nghch; - Bo ng qu ti, qu ti nhit; - 27,59; - Qu in p th t khng. b. Bo v my bin th FM705A - 50, 51, 51N; - Qu dng c kim tra in p; - Qu in p th t khng; - Bo ng qu ti; - Bo v thp p; - Bo ng PT/CT ngt kt ni dy; - Bo v khng in ca MBT, c th la chn ngt hoc bo ng. c. Bo v thanh ci FM762 - 50,51,51N; - Bo ng qu ti; - T ng ngun d phng; - t dy PT/CT; - Bo ng ngt kt ni gia cc thanh ci.

20. Cch khai thc thng tin trn cc loi rle k thut s ti Nh my (thao tc truy sut thng tin rle)

Rle bo v khong cch Micom P443: C th ghi nhn v lu li 5 s c. Cch truy xut s c va xy ra:

Nhn phm & xem s c: gm cc thng s Nhn phm C xa s c.

Cch truy xut s c xy ra (Rle c th lu li 5 s c mi nht):

T mn hnh mc nh

Op parameter Nhng thng s

View record Trang xem s c.

Select event Chn s kin.

Select fault Chn s c mun xem ( c 5 s c). 8

Active group 1 Nhm hot ng 1.

Started phase Pha khi ng.

Tripped phase Pha b ct.

Start element distance Thnh phn bo v khong khi ng.

Earth fault start Khi ng s c chng chm t.

Distance trip Bo v khong cch tc ng.

Fault date Ngy b s c.

Fault time Thi gian b s c.

Fault alarm Bo ng s c.

System frequency Tn s ca h thng.

Fault duration Thi gian duy tr s c.

Relay trip time Thi gian ct ca Rle.

Fault location V tr s c.

Ia Dng s c pha A.

Ib Dng s c pha B.

Ic Dng s c pha C.

Uan in p pha A- t .

Ubn in p pha B- t.

Ucn in p pha C- t.

Fault resistance Tng tr s c. Nhn cho n khi tr v mn hnh mc nh.

Rle qu dng Micom P127: c th ghi nhn v lu li 5 s c. Trnh t thao tc truy cp h thng menu trn rle.

Mn hnh mc nh

Op Parameters Nhng thng s.

Record Ghi nhn.

Fault Record (Ghi nhn s c)

Record number S s c (tt c c 5 s c). Chn s c

Fault time Thi gian xy ra s c

Fault date Ngy xy ra s c

Active set group 1 Nhm 1 hot ng

Fault phase Pha b s c

Threshold Ngng s c ( qu dng cp 1, cp 2

hay cp 3)

Magnitude ln dng s c.

Magnitude ln dng s c pha A IA

Magnitude ln dng s c pha B IB

Magnitude ln dng s c pha C IC

Magnitude ln dng trn trung tnh IN

Magnitude Bin in p s c ca pha A v pha B.

UAB

Magnitude Bin in p s c ca pha B v pha C.

UBC

Magnitude Bin in p s c ca pha C v pha A.

UCA

Magnitude Bin in p d thi im xy ra s c.

UN

Angle Gc gia dng IA v p UBC. IA^UBC

Angle Gc gia dng IB v p UCA. IB^UCA

Angle Gc gia dng IC v p UAB. IC^UAB

Nhn cho n khi tr v mn hnh mc nh

Rle so lch Micom P632: C th ghi nhn v lu li 8 s c. Cch truy xut s c va xy ra:

Nhn phm & xem s c: gm cc thng s nh bng bn di : Cch truy xut s c xy trong 8 ln mi nht:

Mn hnh mc nh

Op Parameters Nhng thng s

Events Nhng s kin

Events recordings

OL-RC

Ghi nhn nhng s kin qu ti.

Events recordings

FT-RC

Ghi nhn nhng s kin s c.

Fault Recording 1

( Ngy - Gi ) (S c 1).Dng phm chuyn sang

s c 2, 3, 8.

( Chn xem s c 1) Fault Recording 1

Fault Duration

( thi gian ghi nhn s c ca Rle)

( Khong thi gian xy ra s c)

Differential Current 1

x Iref

Restraining Current 1

x Iref

( Dng so lch cp 1)

( Dng hm cp 1)

Differential Current 2

x Iref

Restraining Current 2

x Iref

(Dng so lch cp 2)

( Dng hm cp 2)

Differential Current 3

x Iref

Restraining Current 3

x Iref

(Dng so lch cp 3)

( Dng hm cp 3)

Nhn cho n khi tr v mn hnh mc nh.

Rle Micom P922: C th ghi nhn v lu li 5 s c. Trnh t thao tc truy cp h thng menu trn rle

Mn hnh mc nh

Op Parameters Nhng thng s

Records Trang xem s c.

CB Monitoring Gim st CB

Fault records Ghi nhn s c.

Record number C 5 s c gn nht c ghi nhn

8

Fault time Thi gian xy ra s c.

Fault date Ngy xy ra s c.

Active set group 1 Nhm 1 hot ng

Faulted phase Pha b s c.

Trip element Loi bo v tc ng.

Magnitude Bin in p s c.

VA Magnitude Bin in p s c pha A

VB Magnitude Bin in p s c pha B.

VC Magnitude Bin in p s c pha C.

V0 Magnitude Bin in p s c th t khng. Nhn cho n khi tr v mn hnh mc nh.

Ch : Khi c s c bo v r le tc ng ct cc MC th trc ca vn hnh phi kim tra cc n led c ci t trn mt r le xem n no sng. Sau mun ng li MC phi gii tr tn hiu s c trn r le bng cch n phm C.

21. Ti sao phi t thit b t ng li trn ng dy? Nh chng ta bit, thc t thng k v cc s c ca cc ng dy trung p

tr ln, s c thong qua chim 80-90%. Cc s c thong qua ny (phng in, st nh... ) u c th c loi tr bng tc ng ct tc thi my ct,v th m bo vic cung cp in tr li trong thi gian nhanh nht ngi ta thng dng chc nng t ng ng lp li my ct.

thc hin chc nng ny, hin nay trong h thng in c trang b hai bin php:

S dng my ct Recloser (Khi chc nng t ng ng lp li i km hp b my ct).

T ng ng lp li bng cch kt hp my ct vi h thng t ng ng lp li.

22. Quy trnh vn hnh cc rle bo v k thut s mt s hng nc ngoi ang lp t ti trm 110kV Nhn C?

(Hin ang tip tc hon tt)