DC power distribution Flashcards
What are float and equalize values?
float 130VDC
Equalize 135VDC
Battery charger output limited to…..
output current is limited to 125% of full load. full load =400 amps
125VDC battery charger trouble alarm causes
- charger output volts<120VDC
- Charger output volts>140VDC
- Charger near 0 amps
- Loss of AC input to charger
- Blown fuses inside charger
- Charger DC O/P breaker open due to high current
- Loose or faulty charger failure alarm card inside cabinet
Battery charger AC input breaker trips on high DC output voltage value of…..
> 138VDC
Safety design basis of 125VDC system
Provide two physically and electrically independent, redundant systems:
- Meets single failure criteria
- Loss of either bus will not prevent safe shutdown during simultaneous design basis LOCA with a LOOP
- Safety Category 1
UV alarm, If alarm comes in but control board V indication ….
..;Normal bus voltage=loss of non esf bus
…No bus voltage= loss of both esf and non esf bus
Bus crosstie limitations
Verify <100VDC grounds on both busses
Voltages within 20VDC
Once crossties, <400 amps on running charger
Ground Levels I, II, and III
> =75 <100VDC—–Level I—–Implement BOPDC15, notify EMS to initiate ground testing on C priority
=100 <=115VDC—Level II—-Implement BOPDC15, notify EMS to initiate ground testing on a B2 priority
115VDC————–Level III—-Implement BOPDC15, notify EMS to initiate ground testing on a B1 priority. Notify unit planning supervisor, system engineer and repair grounds 24 days
*100VDC ground actuates an alarm on _PM01J
How does Loss of bus 111 or 112 affect IA to containment and PZR porvs?
Isolates IA to containment (IA66 or 65 closes) but PORVs have accumulators so opposite train of failure will still function.
125VDC ESF is fed to RTB and RT bypass breakers to….
…..energize shunt trip when RX trip is called for.
111 Batt charger supplied from….
….USS 131X
CB-1 trips on ….
High DC output voltage >138VDC
CB-2 (DC output) trips on….
Overcurrent
If AF-2 is opened…
….the bus is deenergized because it isolates both the battery charger and the battery from the bus.
3 sources of DC power
Battery charger (normal)
Battery (Emergency Backup)
X-tie to opposite unit (Backup power supply)
Loss of 111 or 112, What is lost or affected?
- Feed reg valves fail as is
- Instrument air isolates to containment
- PZR PORVs 455/456 fail closed (accumulators might keep them operating)???????
- DG 1A/B (respectively) fail to start
- Lose letdown 1CV8152/8160 respectively fail closed
Loss of bus 113, what is affected?
- MF 1a/1c and startup feed pump recircs fail open
2. Lose 1C TDMFWP trip capability from control room
Loss of bus 114, what is affected?
- Loss of letdown, 1CV459/460 and all three LD orifices fail closed.
- Lose DC to trip 1B TWMFWP
- Main feed pump 1B recirc fails open
- Can not start 1A MFP from MCR
- Lose 1B TDMFWP trip capability from MCR
Purpose of 125 VDC system(supplies power to which systems).
Supply 125VDC for each of 2 ESF divisions:
- Rx trip switchgear
- MCB ESF section
- ESF switchgear control systems
- Other safety related systems requiring DC power
Indications of loss of DC
ESF: 125VDC low alarm and MCB meter reading 0 Volts
Non-ESF: 125VDC low alarm and MCB meter reading normal Volts
LCO 3.8.4
3.8 ELECTRICAL POWER SYSTEMS
3.8.4 DC Sources-Operating
LCO 3.8.4 Division 11(21) and Division 12(22) DC electrical power
subsystems shall be OPERABLE and not crosstied to the
opposite unit.
APPLICABILITY: MODES 1, 2, 3, and 4.
LCO 3.8.4 action times one battery charger out
A. One battery charger inoperable. A.1 Crosstie opposite-unit bus with associated OPERABLE battery charger to the affected division. AND A.2 Restore battery terminal voltage to greater than or equal to the minimum established float voltage. AND A.3 Verify battery float current < 3 amps. AND A.4 Restore battery charger to OPERABLE status. 2 hours 2 hours Once per 12 hours 7 days OR In accordance with the Risk Informed Completion Time program
LCO 3.8.4 action times, loss of one dc elec system for any reason not listed in conditions A, B, C
D. One DC electrical power subsystem inoperable for reasons other than Condition A, B, or C. D.1 Restore DC electrical power subsystem to OPERABLE status. 2 hours OR In accordance with the Risk Informed Completion time program
LCO 3.8.5 Shutdown distribution systems
3.8 ELECTRICAL POWER SYSTEMS
3.8.5 DC Sources-Shutdown
LCO 3.8.5 One DC electrical power subsystem shall be OPERABLE.
—————————-NOTE—————————-
The required DC electrical power subsystem may be crosstied
to the opposite unit, when the opposite unit is in MODE 1,
2, 3, or 4 with an inoperable battery charger.
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APPLICABILITY: MODES 5 and 6,
During movement of irradiated fuel assemblies.
ACTIONS
————————————-NOTE————————————-
LCO 3.0.3 is not applicable.
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