PB/PG/PH/PK/PN- Class Electrical Flashcards
What are the colors associated with each channel, A, B, C, D?
A-red
B-green
C-yellow
D-blue
What are the system designators for the class 4.16kV, 480V load centers, 480V MCCs, 125VDC and the 120VAC systems?
PB-4.16kV PG-480VAC load centers PH-480v MCCs PK-125VDC PN-120VAC
What happens to the class 4160V busses when a Loss of Off-site power occurs?
the emergency diesels would start and auto load to the class busses
what is the purpose and design of the class 4.16kV power (PB) system?
purpose:
provides 4160V power to one of two redundant and independent safety related load groups, or equipment that is required to safely shut down the unit
design: has normal (off-site power) and alternate (emergency diesels) power source
detects degraded voltage and loss of voltage on normal power source and will send a LOP to ESF actuation system
Can one safety train of equipment safely shut down the unit, or are both required?
only one train is required
Where does PBA-S03 and PBB-S04 get power from?
NAN-S03/04 through the ESF(NBN-X03/04) transformers.
What purpose do the FLEX portable diesel generators serve?
In a Beyond Design Basis event, they can be tied to supply PBA-S03 or PBB-S04, downstream of the ESF transformers
How does the NA system interface with the PB system?
provides all power to the PB system via the preferred, alternate or normal shutdown configuration, including SBOGs
How does the NB system interface with the PB system?
PB receives power from the NB ESF transformers
How does the DG system interface with the PB system?
PB receives power from the Class emergency diesels during a LOOP
How does the PG system interface with the PB system?
PB supplies power to the PG load centers
How does the PH system interface with the PB system?
PB receives 120VAC from the PHD-panels for switchgear heaters
why do switchgear require space heaters?
to maintain temperature above the dew point
How does the PK system interface with the PB system?
PK provides control power to the PB switchgear
How does the BOP(ESFAS/SA) system interface with the PB system?
PB sends signals for each load group of bus under-voltage to the SA system and receives load shedding and load sequencing signals from the SA system
How does the SP system interface with the PB system?
PB supplies power to the Essential spray pond pump motors
How does the SI system interface with the PB system?
supplies power to the Safety injection pump motors (HPSI/LPSI)
How does the EC system interface with the PB system?
PB supplies power to the essential chillers
How does the WC system interface with the PB system?
PB supplies power to the A normal chiller
How does the EW system interface with the PB system?
PB provides power to the essential cooling water pump motors
How does the AF system interface with the PB system?
PB provides power to the B and N auxiliary feedwater pump motors
How does the HJ system interface with the PB system?
HJ provides normal and emergency cooling to the class switchgear rooms
what is the purpose, operation and location of the ESF transformers?
purpose/operation:
step down 13.8kV to 4160V and provide that power from the preferred off-site source or from the SBOGs
oil/ air and forced air cooling at 70 C
cooling is powered from 480VAC
can fault isolate
location:
outdoors, south side of the turbine building
what is the purpose, operation and location of the PB switchgear?
purpose/operation: distribute power to class safety related loads, start and trip loads as required and protect bus from damage due to faults and overloads
can be operated remotely from control room, remote shutdown panel (B train only) or locally
location: separate class switchgear room, 100' control building
In PB breaker cabinets, what are the fuse names and what do they supply power to?
UC-closing circuits and green light
UT-tripping circuits and red light
UE-control room connections to the tripping and closing circuits
UL- for racking motor
What D-panels do PBA-S03 and PBB-S04 receive control power from?
PKA-D21 (S03)
PKB-D22 (S04)
What breaker inside the breaker cubicle provides control power to the fuses?
RRC
For seismic concerns, when PB breakers are racked out, what must be done?
the breaker must be racked back up 1-2” off the ground or restrained
Describe the automatic features of the class 4160v power system.
under voltage relays prevent system running on low voltage and will fault the bus
8 of the 9 under-voltage relays input into the BOP ESFAS and initiate 2/4 logic and perform:
start respective diesel generator
load shed bus
close diesel generator breaker
load sequence diesel generator
What is a LOP?
Loss of Power
What is a LOOP?
Loos of Off-site Power
How many under-voltage relays are on each PB bus and what are they dedicated for?
9 total
5 for degraded voltage
4 for under voltage detection
the 5th degraded voltage relay will provide annunciation 10 seconds after voltage drops below 90%
When do the degraded voltage relays actuate?
30 seconds after voltage drops below 90% of rated capacity
When do the under voltage detection relays actuate?
immediately after voltage drops to 75%
On PB busses, what trips the normal and alternate breakers?
if electrical load shed is generated
the opposite supply breaker is closed from B01
ESF transformer faults
if the 86 lockout operates
(PB page 22)
How will a loss of the PB system impact the plant?
power must be restored within two hours due to class battery system capacity
failure of one safety train will require the redundant train to meet safety functions
may enter abnormal operating procedure or emergency operating procedure to restore power
with a diesel generator running, how long do you have to get a spray pond pump running before the diesel shuts down?
2.6 minutes
What circumstance would require cross tying PB Busses?
when one shutdown cooling loop is not available and the opposite train diesel generator is not available
What does the Degraded Electrical Power Abnormal Operating Procedure provide guidance for?
LOP to any 480V or higher bus that does NOT cause a LOOP or blackout
PB bus cross tying
What do the Emergency Operating Procedures provide guidance for?
they address the availability of the 4160V busses to ensure ONE class bus is available to support a safety equipment train.
determining a blackout if no PB busses are available
What PB system equipment is related to tech specs while operating?
PBA-S03 and PBB-S04 must be energized to their proper voltages to be OPERABLE
tie breakers between redundant safety systems must be open
8 hours to become operable if either train becomes inoperable
What PB system equipment is related to tech specs while shutdown?
All systems necessary to support OPERABILITY of required systems, equipment and components
What is the purpose of the PG/PH system?
step down power from 4160v to 480v and send that power to safety related equipment as well as essential non class equipment.
equipment is design basis
How many load centers and MCCs are on each safety train?
Three load centers
Four class MCCs
Two SIAS load shed MCCs
What is a SIAS Load shed MCC?
A non-class MCC supplying power to essential non class loads that will be tripped in the case of a SIAS
Where do PG load centers get control power from?
125VDC (PK)
Where do PH MCC breakers get control power from?
They provide their own control power
How do the PG/PH systems interface with ESFAS?
receives control signals from ESFAS
How does PG/PH interface with CVCS?
PG- provides power to the charging pumps
PH- provides power to VCT outlet valve and RWT gravity feed line suction valve to charging pumps
How does PG/PH interface with HVAC equipment?
provides power to containment normal ACU fans, CEDM normal ACU fans, and control room essential AHU fans
How does the PG/PH system interface with pressurizer pressure control system?
provides power to two banks of class back up heaters.
How does the PG/PH system interface with the Diesel Generators?
provides power to DG fuel oil pumps, air compressors, vent fans and lube oil pumps
How does the PG/PH system interface with Fuel pool cooling system?
provides power to the fuel pool cooling pump motors
What two PG load centers have forced air cooling fans?
PGA-L31 and PGB-L32
fans turn on at 190*C
rated at 1000kVA
(others rated at 750kVA natural air cooled)
What is the purpose, operation and location of the load center transformers?
Purpose/operation:
step down 4160v to 480v to supply larger 480v loads and to MCCs for smaller 480v loads
Location:
in the load centers on the 100’ control building
Which breaker on a 480VAC load center is always the feeder breaker distributing power to the loads?
B2 breaker
What three positions are there for a load center breaker to be in?
operating, test, withdrawn
or
connect, test, disconnect
What three types of circuit breakers are found on a 480VAC load center?
main feeder breaker, motor feed breaker, MCC feed breakers
What position are the main and auxiliary contacts in while a load center breaker is in the test position?
main contacts disconnected, aux contacts connected
What is the main difference between the three types of circuit breakers found on a load center?
amperage rating and protection schemes
On PG load centers, where can the main feeder breaker 86 lock out relays be reset?
locally and control room
What does the white bell alarm button indicate on load centers?
it means the breaker was tripped on overcurrent specifically and must be pushed in to be reset prior to closing the breaker again
What three positions do MCC breakers have?
on, off, tripped
Class MCCs are normally operated locally. When continuity of operation is essential, and required for hot shutdown, where else can class MCCs be operated from?
Remote shutdown panel
In MCC breakers, what do the magnetic starters do?
turning the load ON and OFF.
the starter is de-energized in an overload condition
What is the purpose and operation of the Train B disconnect switches?
They are in place to, in the case of a control room fire, separate the control room from the B train equipment electrically.
There is a REMOTE/LOCAL and LOCAL switch locally.
Describe the automatic feature associated with the PG/PH system.
In the case of a SIAS, the four essential, non class, SIAS load shed MCCs will trip.
trip can be over ridden locally
What impacts would the plant feel if there was a loss of the PG/PH system?
low level impacts, possibly lose a charging pump or back up pressurizer heaters.
What impact would the PG system feel if it lost control power?
breakers need local manipulation
What impact would the PH system feel if PG was lost?
MCC breakers would trip open
Describe the FLEX modifications that were made to the Class 480V Electrical System in order to support the PVNGS Extended Loss of All Site AC Guidelines.
two FLEX generators will be connected to the PG system via FLEX connection junction boxes on the south wall of the control building with conduit to the A train LC’s, L31, L33, L35
In regards to requiring the use of flex equipment in an emergency situation, why is the primary strategy to recover the A train LC’s? What is the alternate strategy?
these LC’s will allow the plant to repower vital battery chargers to allow infinite coping time.
Alternate strategy is to re-energize the B train LC’s via 480VAC connections via FLEX junction boxes on the east control building wall.
What must be done prior to Starting the Flex diesel generators to prevent overloading them?
opening all LC and MCC breakers
How long do you have for FLEX 480VAC diesel generators to be deployed and operational?
T+34 hours
Where do FLEX 480VAC Diesel generators get fuel from?
gravity-fed hose connected to one of two safety related diesel fuel day tanks in the diesel building.
What is the purpose of the PK system?
consists of four subsystems that provide 125VDC to four independent class loads, essential AC power inverters and ESF equipment.
provides two hours of 125VDC power
What are the two PK load groups and what channels are they representing?
Channel A: “A” / “C”
Channel B: “B” / “D”
How does the PK system interface with the HJ system?
HJ provides cooling and exhaust to the battery rooms to remove H2 build up
How does the PK system interface with the PH system?
PH sends 480VAC to the battery chargers
How does the PK system interface with the PB system?
control power
If switchgear breakers lose control power, would they trip on a fault?
No
How does the PK system interface with the PG system?
control power
How does the PK system interface with the PE system?
Control power and field flashing
What would happen to the Emergency Diesel generators if PK was lost?
Diesels would trip but output breaker would remain closed
How does the PK system interface with the AF system?
PK supplies power to MOVs and controls for the steam driven A aux. feed pump
How does the PK system interface with the SI system?
PKC + PKD supplies power to shutdown cooling suction isolation valves -653 and -654
How does the PK system interface with the PN system?
PK is the power supply to four inverters to 120VAC class instrumentation
How does the PK system interface with the SG system?
SG uses DC power to provide a permissive signal to the ADV’s to allow remote operation
PK provides power to many containment isolation valves. What is the fail state of majority of containment isolation valves?
Fail closed
What is the purpose, operation and location of the class battery chargers?
purpose:
step down and invert the 480VAC supply to 135VDC with the capacity to supply all demands and charge batteries from minimum charge within 12 hours
operation:
float and equalize modes with a 24hr equalizing timer
has transfer switches for isolating load shedding, sequence permissive relays and other equipment in the CR
The A battery can be isolated from the control room
location:
100’ control building
How long will the class batteries supply power in the case of a LOOP?
2 hours
What two shutdown cooling isolation valves does the PK system supply from the PKC-M43 and PKD-M44 busses?
SIC-UV-653 and SID-UV-654
What prevents condensation build up in the 125VDC control centers?
120VAC space heaters
What safety channels are equipped with transfer switches on the battery breakers and why?
A,B, and D have them to take local control and indication in the event of a control room fire.
How would a loss of the PK system affect the plant?
PN will transfer to alternate power
the A aux. feed pump turbine will trip
ADV’s will fail closed
containment isolation valves will fail closed
the respective Reactor Trip Switchgear (RTSG) breaker will trip open
If only one PK bus is lost, can the unit stay at 100% power?
Yes.
If a PK bus is lost, will the swing charger automatically transfer?
No, the AO will perform this in the field.
What is the purpose of the PN system?
provide 120VAC through preferred or back up sources of power to four independent channels of class vital instrumentation
control power to the reactor protection system (RPS) and ESFAS
Between the Channel load groups in the PN system, A/C and B/D, which load group has to be switched to its back up power source manually?
A/C (unit 1 only)
A/C and B/D in units 2 and 3 will all transfer automatically
How does the PN system interface with HJ?
HJ provides cooling air and ventilation to the equipment rooms
How does the PN system interface with PH?
PH supplies 480VAC to back up power source for PN
How does the PN system interface with PK?
PK provides power to PN bus and ground fault indication circuit
How does the PN system interface with EC
powers EC flow transmitter
How does the PN system interface with RPS/ESFAS?
RPS supplies 120 VAC power to class instrumentation, control, protection and indication circuits
What is the purpose, operation and location of the inverters in the PN system?
purpose/operation:
to invert 125VDC to 120VAC
location:
100’ control building
There is an input and an output breaker on the inverter. What do they do?
input provides DC to the inverter and output supplies power to the “forward transfer” switch that automatically switches to back up power source
On the PN inverters, why is the pre charge button important?
it must be pressed prior to closing the input DC breaker on the inverter
Why is the Unit 1 PN system A/C inverter manual transfer switch break-before-make?
to prevent paralleling AC sources out of phase
In which units does the PN inverters have a manual bypass switch for bypassing the static transfer switch?
Units 2 and 3
In the PN system, where do the voltage regulators receive power from?
PH
How many class 120VAC D-panels are there in each unit? Are they grounded?
four
they are ungrounded
What do the PN D-panels supply power to?
they each supply one channel in the RPS and ESFAS control systems
How are ground faults indicated on the PN D-panels?
red light will be on
What is the impact on the Plant when the PN system is lost?
losing one channel of PN will not cause a trip, but the instrumentation for that channel will be lost.
if two channels are lost, the plant will trip.
What is the tech spec for the PN inverters?
to stay operable, one inverter can be taken out of service and bypassed to the voltage regulator as long as all other inverters are in service
Why would one PN inverter need to be bypassed to the voltage regulator?
to accomplish an equalizing charge on the respective battery within 24hours
