QUY TRNH TH NGHIM MY BIN P

NI DUNG

I/ Tiu chun, khi lng th nghim my bin p

1. Cc my bin p in lc phi c th nghim xc nh cht lng thit b trong qu trnh ch to, khi xut xng, hay trong vn hnh hng nm. Cng tc th nghim nhm mc ch gim st cht lng sn xut v gim st cht lng vn hnh ca thit b nhm gim xc sut s c cng nh tin hnh cc k hoch bo dng d phng, sa cha. 2. Khi lng cc hng mc, tiu chun v thi gian th nghim my bin p tu thuc vo nhiu yu t: nh in p v dung lng nh mc ca my bin p, iu kin lm vic ca my bin p, tm quan trng ca my bin p...

II/ Cc hng mc th nghim chnh ca my bin p lc 1. Kim tra tnh trng bn ngoi 2. o in tr cch in. 3. Xc nh tang gc tn hao in mi (tg) 4. Th nghim chu in p mt chiu tng cao v xc nh dng in r. 5. Th nghim chu in p xoay chiu tng cao tn s cng nghip. 6. Th nghim chu in p xung thao tc. 7. Th nghim chu in p xung st tiu chun. 8. Th nghim phng in cc b. 9. Th nghim chu in p qu p cm ng tn s cao. 10. Th nghim xc nh cht lng du cch in : 11. Th nghim xc nh t u dy. 12. Th nghim xc nh t s bin p. 13. Th nghim khng ti.

14. Th nghim ngn mch. 15. Th nghim xc nh n nh nhit. 16. Th nghim hiu chnh th vng ca b chuyn nc phn p. 17. Th nghim xc nh kh nng chu p lc ca v my. 18. Th nghim xc nh kn ca v my. 19. Th nghim xc nh n . 20. Th nghim xc nh n nh ng (th nghim ngn mch trc tip in p nh mc) . Trong thc t vn hnh, cng tc th nghim my bin p phi b qua mt vi hng mc do thiu cc thit b th nghim cn thit. Hin nay, vi trang thit b th nghim hin c, cc hng mc th nghim s 6, 7, 8, 15 , 17, 19, 20 cha th thc hin c

III/ Trnh t v phng php th nghim:

1.Kim tra tnh trng bn ngoi:

- Quan st tng th my bin p, kim tra tnh trng v my, cnh tn nhit, s u vo, thng du ph xem c vt try xc, vt va chm mnh, s c nt v, cc vt r du ( kn cc mt bch trn v my) do chuyn ch, lp t khng ng qui nh. i vi cc my bin p c thit b kim tra rung trong qu trnh chuyn ch, cn phi xem kt qu o rung ny c t yu cu nh ch to hay khng. - Kim tra nghing mt bng t my theo thit k. - Kim tra tip a v my. - Kim tra tip a trung tnh ca cun dy c trung tnh ni t trc tip. - Kim tra tnh lp ng ca cc thit b (k c cc thit b ph lp sn ti nh my ch to) nh r le hi, van phng n (tho ngm hm van phng n trc khi a my vo vn hnh ). Trong mc ny cn c hng mc kim tra tnh lp ng ca b truyn ng vi b chuyn nc phn p iu p di ti. Phn ny c thc hin theo hng dn ca nh ch to i vi tng loi b chuyn nc phn p di ti. - Kim tra tnh lp ng v trng thi cc van du tun hon, van du ly mu, van du lin thng gia thng du ph v b iu p di ti, van du gia thng my v cc cnh tn nhit. - Kim tra mc du trong my.

2. o in tr cch in : Khi o cn tun th cc yu cu sau y: 1. Khng o in tr cch in khi my bin p ang trong trng thi m v m mi trng cao. 2. V v li ca my bin p phi c ni t. 3. Ngt ton b dy ni vi my bin p ti: - Cc cc ni cao th, h th - Cc cc ni trung tnh - Cc cc ni n bo, qut v.v... 4. Lm sch v my v cc cc ni trc khi o 5. Khng o in tr cch in ca my bin p cch in du trong trng thi du b rt ht bi v in tr cch in khi du ch bng 1/4 n 1/2 in tr cch in khi my khng c du. 6. Cc cc ni ca tng cun dy phi c ni ngn mch. 7. in tr cch in c o gia tng cun dy vi cc cun khc c ni t.

8. Sau khi kt thc php o, phi ni t tt c cc ni cho phng ht in (S o c trnh by trn cc hnh v). 9. in tr cch in ph thuc vo nhit v t l nghch vi nhit . My bin p ngui c in tr cch in cao hn in tr cch in ca my bin p trng thi nng. Dng mgmt 2500V o in tr cch in pha cao p, dng mgmt 1000V o in tr cch in pha h p: - i vi MBA 1 pha ch c 1 s cao th o h p vi v v cao p 1 u ni vi v my; - i vi MBA 1 pha c 2 s cao phi o gia cao-h, cao-v v h-v; - i vi MBA 3 pha th o cch in gia cao-h, cao-v v h-v. in tr cch in ca cc bu-lng p li thp v cc x p tn (o bng mgmt 2500V) khng c gim thp hn 50% so vi s liu xut xng ca nh ch to. Nu khng c s liu ca nh ch to th khng c thp hn 2M.

i vi my bin p 110kV v cao hn, k c i vi cc my bin th ln 35kV (cng sut 7500kVA v cao hn), in tr cch in R60 c kim tra trng thi nng khi nhit lp du trn 50-60 0C. Tr s in tr cch in R60 khng tiu chun ho m cn c vo s liu ca nh sn xut khi xut xng. Nu tr s R60 o khi th nghim nhit khc vi nhit o ca nh ch to th cn phi hiu chnh li theo qui tc: gim nhit i 10 0C th tr s in tr cch in nhn ln 1,5 ln hay theo bng sau.

Bng 1 Th nghim o in tr cch in thng c tin hnh trc hoc sau khi sa cha hoc bo dng. D liu th nghim thng c ghi li dng cho mc ch so snh v sau. Quy tc chung c s dng i vi cc gi tr nghim thu dng cho ng in an ton l tr s cch in 1 mgm trn 1kV ca gi tr nh mc trn nhn my v cng thm 1 mgm. Cc gi tr tham kho i vi h thng cch in tt c cho trong bng 2

Bng 2: Gi tr in tr cch in in hnh ca ccMBA lc v phn phi:

Dy qun cao p vi dy qun h p. S ni dy th nghim in tr cch in ca my bin p mt pha c cho trn hnh 1.1. Gi tr c mgm k phi ng vi nhit v c hiu chnh v nhit 20 0C theo bng 2.2. Nu gi tr th nghim ti ch ln hn mt na gi tr th nghim xut xng hoc 1000 M th h thng cch in ca my bin p coi l an ton i vi th nghim cao p. i vi my bin p ba dy qun trnh t th nghim nh sau:

Hnh 1.1: S ni dy th nghim in tr cch in ca my bin p ba pha K hiu u dy: L (line) - pha; E (earth) - t; G (guard) - mn chn bo v.

a. Ni dy qun cao p vi h p v t;b. Ni dy qun cao p vi t v dy qun h p vi mn bo v; c. Ni dy qun h p vi cao p v t; d. Ni dy qun h p vi t v cao p vi mn bo v; e. Ni dy qun cao p vi dy qun h p.Cao p vi h, trung p v t(H - LTG)Trung p vi cao, h p v t (T - HLG)H p vi cao, trung p v t (L - HTG)Cao, h v trung p vi t (HLG - G)Cao v trung p vi h p v t (HT - LG)H v trung p vi cao p v t (LT - HG)Cao v h p vi trung p v t (HL - TG)

Khng tin hnh th nghim dy qun my bin p khng du v tr s in tr cch in ca khng kh thp hn ca du. Do vy, khng tin hnh th nghim in tr cch in ca my bin p trong chn khng v c kh nng gy phng in xung t. Hnh 1.1 l s th nghim in tr cch in ca my bin p ba pha. S a, c, e l s thng s dng. S hnh 2.5 b v d cho kt chnh xc hn. Kt qu c theo s hnh2.5a v b thc t cho kt qu tng t theo s 2.5e. Gi tr in tr cch in i vi my bin p kh v my bin p nha phi so snh vi in tr cch in cp A ca my in quay mc d khng c gi tr in tr tiu chun cc tiu.

My bin p du v b iu chnh in p to ra vn c bit v iu kin du cch in gy nh hng ng k n in tr cch in ca dy qun. Nu khng c thng tin chc chn v in tr cch in ca my bin p c th s dng cng thc sau:

y IR l in tr cch in cc tiu o bng mgm k 500V sau 1 pht gia dy qun vi t, vi cc dy qun khc nhau. - C l hng s 20 0C cho trong bng 3 - E l in p ca dy qun th nghim. - S dung lng nh mc ca dy qun (kVA).

Cng thc trn dng cho cc my bin p mt pha. Nu my bin p cn th nghim l ba pha v th nghim ba dy qun ring r nh mt dy qun th E l in p nh mc ca dy qun mt pha (in p dy khi ni tam gic v in p pha khi ni hnh sao), cn S l dung lng nh mc ca ton b dy qun ba pha.

Bng 3:

3. o h s hp th in mi:

H s hp th l t s gia Rc o bng Mgmmt sau 60 giy k t lc t in p vo v Rc o sau 15 giy. Khth = R60 / R15. Nu cch in kh th h s hp th ln hn 1 kh nhiu, cn cch in m th h s hp th gn bng 1. H s hp th cng khng tiu chun ho. Thng thng, h s hp th trong khong nhit t 10 0C n 30 0C ca cc my bin p khng b m nm trong gii hn nh sau: i vi cc my bin p 35kV v thp hn, h s hp th kth 1,3. Cn vi my bin p 110kV v cao hn th h s hp th nm trong gii hn: kth = 1,5 - 2,0. Khi my bin p b m hay c khuyt tt, h s hp th kht 1.

4. Xc nh tang gc tn hao in mi (tg)

a) o gc tn tht in mi l mt trong nhng phng php ph bin nht nhm pht hin tnh trng xung cp chung ca cch in. S gi ho, s thm m, s xut hin nhiu bc kh trong cch in thng dn n s tng tn hao in mi tg. b) i vi my bin p, tr s tg c th cho bit nhng khuyt tt chim mt phn th tch ng k ca cch in (nh s gi ho chung, s thm m) nhng n khng th pht hin mt cch chnh xc nhng khuyt tt tp trung. c) Trong iu kin vn hnh, thng o tg in p khng qu 10kV, khng ph thuc vo in p nh mc ca thit b in, v o vi in p cao hn i hi thit b o cng knh, to ln. d) Tiu chun qui nh o tn tht in mi tg thng ch p dng i vi cc my bin p c in p t 20kV tr ln. y l mt ch tiu quan trng xc nh m ca my bin p. Gi tr tg khi tin hnh th nghim lp t nhit chnh lch vi nhit ca nh ch to cn hiu chnh li bng cch chia gi tr s cho ca nh ch to cho h s bin i K2 theo bng 4 nh sau:

Gi tr tg cun dy khi th nghim vi du ph hp vi iu kin nu nh tg ca du khng vt qu 1% nhit 20 0C25 0CBng 4: