rockman7892
Electrical
- Apr 7, 2008
- 1,162
Looking for feedback from experience with applying Hi Impedance bus diff on switchgear bus where station service CPT's are fed from bus within the differential zone.
Application under consideration is a 34.5kV 1200A SWGR lineup with high impedance bus diff wrapped around incoming, feeders and tie of M-T-M lineup. CT's on Main, Feeder, and Tie breaker are C200 1200:5 MR CT's tapped at 600:5 Tap. Buss diff relay is SEL 487Z.
Switchgear has a 50kV CPT fed from bus with primary fuse. CPT primary rating at full load is 1.44A. I'm guessing that with inrush of CPT it can have momentary inrush of 15-20A.
With 1200:5 CT's tapped at 600:5 they provide an effective C100 ratio.
Concern is weather CT ratings will be able to produce enough voltage and cause mis-operation or nuisance tripping of buss diff during CPT normal operation or inrush.
Looking to hear practical experience from others and weather Low Imp buss diff is more practical for this application. Or is high impedance diff with higher CT class preferred option?
Application under consideration is a 34.5kV 1200A SWGR lineup with high impedance bus diff wrapped around incoming, feeders and tie of M-T-M lineup. CT's on Main, Feeder, and Tie breaker are C200 1200:5 MR CT's tapped at 600:5 Tap. Buss diff relay is SEL 487Z.
Switchgear has a 50kV CPT fed from bus with primary fuse. CPT primary rating at full load is 1.44A. I'm guessing that with inrush of CPT it can have momentary inrush of 15-20A.
With 1200:5 CT's tapped at 600:5 they provide an effective C100 ratio.
Concern is weather CT ratings will be able to produce enough voltage and cause mis-operation or nuisance tripping of buss diff during CPT normal operation or inrush.
Looking to hear practical experience from others and weather Low Imp buss diff is more practical for this application. Or is high impedance diff with higher CT class preferred option?