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.
————————————————————
APPLICABILITY: MODES 5 and 6,
During movement of irradiated fuel assemblies.
ACTIONS
————————————-NOTE————————————-
LCO 3.0.3 is not applicable.
————————————————————–
LCO 3.8.5 DC power source becomes unavailable
A. One required DC electrical power subsystem inoperable for reasons other than Condition B. A.1 Declare affected required feature(s) inoperable. OR Immediately (continued) DC Sources-Shutdown 3.8.5 BYRON — UNITS 1 & 2 3.8.5 — 2 Amendment 198 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. (continued) A.2.1 Suspend CORE ALTERATIONS. AND A.2.2 Suspend movement of irradiated fuel assemblies. AND A.2.3 Initiate action to suspend operations involving positive reactivity additions. AND A.2.4 Initiate action to restore required DC electrical power subsystem to OPERABLE status. AND A.2.5 Declare affected Low Temperature Overpressure Protection feature(s) inoperable. Immediately
LCO 3.8.6 Battery parameters
3.8 ELECTRICAL POWER SYSTEMS
3.8.6 Battery Parameters
LCO 3.8.6 Battery parameters for Division 11(21) and Division 12(22)
batteries shall be within limits.
APPLICABILITY: When associated DC electrical power subsystems are required
to be OPERABLE.
ACTIONS
————————————-NOTE————————————
Separate Condition entry is allowed for each battery.
————————————————————
What float V and float current values are specified in LCO 3.8.6?
<=2.07V, 2 hour action time, restore in 24 hours
>3.0 Amps, 2 hour action time, restore in 12 hours
Also concerned with proper electrolyte level and pilot cell electrolyte temperature
Main and reserve breaker scheme description
- Ensures control power available if the main feeder breaker or cable should fail.
- Available for control power to:
- Main gen relaying and metering
- MCB turbine panel
- ESF and Non-ESF (480VAC, 4160VAC, and 6900VAC)
Front and rear panel supplies
3.8.9 distribution systems
Requires 111 and 112, 2 hours if a dc system not operable (looks at the DC bus)
250VDC loads
Main turbine oil emergency oil pump Air side seal oil back up pump Turbine drive FW pump emergency oil pumps Main condenser vacuum breaker Computer inverter
Duration of power requirements for 250VDC loads
ASSO backup pump 2 hours MTO Emergency bearing oil pump 1/2 hour TDFW B and C FW Emergency oil pump 1/2 hour Computer inverter 1/2 hour Vacuum breaker valve Momentary only
Modes of operation (float equalize) for 250vdc
Float 260 VDC
Equalize 270 VDC
Power supplies to 250VDC busses 123 and 223
134Z and 234Z (Non ESF loads)
To crosstie 250VDC busses……
…..<140VDC grounds on both busses, and voltages within 30VDC
5.5.17 Battery monitoring and maintenance program
5.5.17 Battery Monitoring and Maintenance Program
This program provides for restoration and maintenance, based on the
recommendations of IEEE Standard 450, “IEEE Recommended Practice for
Maintenance, Testing, and Replacement of Vented Lead – Acid
Batteries For Stationary Applications,” or of the battery
manufacturer of the following:
A. Actions to restore battery cells with float voltage
< 2.13 V, and
B. Actions to equalize and test battery cells that had been
discovered with electrolyte level below the minimum
established design limit
Battery room temperature limit
<= 60F any connected cell electrolyte temperature
108F
Loss of control power on ABT
ABT will not function
Amp hour rating of batteries
2320 Amp hours
