m bo tnh cung cp in lin tc, ngi ta thng dng mng vng c nhiu ngun
cung cp. i vi mng in ny th nu khng dng thit b nh hng cng sut th tnh
chn lc ca bo v s khng c m bo.6.1 Nguyn tc hot ng6.2 Phn t nh hng
cng sut6.3 Bo v c hng ca dng in 3 cp6.4 nh gi 6.5 Bi tp
*
Trong mng in c nhiu ngun cung cp, th ta cn dng thit b nh hng cng
sut. R le cng sut c nhim v nh hng truyn cng sut.*V d: Nu khng thit
b nh hng cng sutKhi NM ti N1Th BV2 ct trc BV3
*V d: Nu khng thit b nh hng cng sutKhi NM ti N2Th BV3 ct trc BV2
Nh vy ta thy nu khng t thit b nh hng cng sut th tnh m bo khng chn
lc.
Trong mng in c nhiu ngun cung cp, th ta cn dng thit b nh hng cng
sut. R le cng sut c nhim v nh hng truyn cng sut.*Lc ny ta thy gc
lch pha c gi tr dng
*Lc ny ta thy gc lch pha c gi tr m
*Trong mng in c nhiu ngun cung cp, th ta cn dng thit b nh hng
cng sut. R le cng sut c nhim v nh hng truyn cng sut.
*Mmem cc i khi, v l hng nhy nht ca rle cng sut l gc lch gia iu v
uR l gc lch gia iR v uR
*Vng tc ng ng vi iu kin.Tc ng khi thng Momen cnThng thng nnThng
thng nnNM nhiu phaNM chm t
*Thng thng nnThng thng nnNM nhiu phaNM chm t
*R le nh hng sng sut c th lm vic theo dng v p ton phn. Hay n c
th lm vic theo dng v p th tTa kho st s phn c cng sut ca cc thnh phn
th t
*S ni r le nh hng cng sutS 90S 60 loi 1S 60 loi 2S 30
*S 90
S 90R le pha URIRAUBCIABUCAIBCUABIC
*S 60 loi 1
S 60Loi 1R le pha URIRAUACIABBUBAIBCCUCBICA
*S 60 loi 2
S 60Loi 1R le pha URIRA-UCIAB-UAIBC-UBIC
*S 30
S 60Loi 1R le pha URIRAUACIABUBAIBCUCBIC
Ta bit gc ng dy vo khong 60 -80 , nn u = 65 l hp lVng cht ca rle
cng sut: khi NM ba pha xy ra gn ni t bo v th UR = 0 nn rle khng tc
ng. khc phc ta dng bo v ct nhanh khng hng*NMUR = 0
n gin, bo m tc ng chn lc i vi mng nhiu ngun cung cpCc u nhc im
tng t nh bo v khng hng (chng 5)*
Tng t nh bo bo v 3 cp khng hng (chng 5)Ta phi tin hnh tnh ton
theo 2 chiu cho cc bo v r le*
