Switchyards Flashcards
What are the three site switchyards and what are their general arrangements described?
345kV - ring bus, 138kV - line bus, 34.5kV - line bus
How does the 345kV switchyard provide power to the U2 and U3 RATs?
U2 - Through TR86 to the RAT OR (Unqualified) through 138kv Bus 1
U3 - Directly off Red Bus.
What kind of circuit breakers are present in the 345kV yard?
Most are SF6 GCBs. The 4-8 breaker is an OCB.
Where are the 345kV SF6 GCB powered from?
120/208 AC Dist via TELEMAND (Bus 25 and 36 respectively) and 345 kV 125vdc.
Which unit is tied to which ring bus?
U2 Blue; U3 Red
Where is 345kV shown in MCR? and what happens upon loss of power to panel?
923-2 - loss of DC 2A-1 will cause horn with no alarm tiles on panel.
What are the normal feeds to the Red and Blue 120vAC circuits?
Red - Bus 36 (TR 83) Backup Bus 25
Blue - Bus 25 (TR 81)
What is the normal Switchyard 480vAC power supply?
Bus 25; Backup Bus 36
How is the SY AC controlled?
Telemands auto swap on loss of normal power; manual return required.
What shows in MCR upon Breaker Operation?
Two red lights indicate breaker is shut with trip coil continuity
Which MODs may be controlled from MCR?
Which may be controlled locally?
What is power for MOD?
Line 1223, TR 81, TR 83
ALL may be controlled locally
DC Powered from Relay House Battery
When will a MOD Trip Open?
When Associated GCB trips open on low pressure.
What are the setpoints for GCB’s?
Low SF6 Pressure - 92.8 psig - CB Trips and lockout
Low Oil Pressure - 3960psig - minor prevents closing; major prevents opening
TRIP ON POLE DISAGREEMENT - cycles twice then trips open
What are the setpoints for 4-8 OCB?
Low air pressure 250psig
Lockout at 230psig (held closed by trip free latch, but will not reclose if open)
Which 138kV Breakers are normally open? Closed?
2-3 is normally open, all others normally closed.
How does the TR-22 Transfer disconnect function?
TR-22 normally powered through TR-86, but may be powered via 138kv Bus.
Only one disconnect may be closed at any time. Has mechanical linkage to prevent closing both with ASCO swap protective relaying
What is normal DC power to 138kV yard old relay house?
Was the U1 125vdc battery Bus 2; reserve from Bus 1 with Normal Seeking ABT
What normally provides 138kV 480 feed?
Unit 1 PC 4B via D7L in 138kV relay house:
to 34kV relay house.
Heaters
TR 143 for (120/208 VAC)
What provides the 138kV OCB power?
Panel 19L - 120/208V - Reserve via MANUAL transfer to LP 22L
Loss of power to Air Compresser causes MCR alarm
Where are 34kV breakers normally controlled from?
NOT MCR. Locally in Relay house or via LD from SCADA.
What provides 34kV 480 feed?
138kV relay house panel
What provides 125vdc power for 34kv SY?
has its own battery in relay house.
Where does the power for the 138kV new relay house come from?
34kv Local lines
What is Local Breaker Backup?
Upon line fault, a line breaker will open. If it does not, then the next breaker in line will attempt to open to isolate the fault. THIS DOES NOT CASCADE DOWN THE LINE.
