.AR Elect. PK PN NK NN (Welch's Highlighted Notes)

Question 1

PK:

• How many independent subsystems?
• Normal Operating Voltage?
• What is the required capacity/time and the minimum temperature required for PK? (on a loss of charger)…

Answer 1

• Four independent subsystems (PKA, PKB, PKC and PKD).
  
  • Subsystem consists of battery, charger, control center and distribution panel
• Normally operates at ~ 135 VDC.
  
  • Bus voltage limits are 129.0 - 139.8 VDC
  • Battery float voltage is normally 130.2 - 135.0 VDC
  • Equalizing mode max voltage 139.8 VDC
• Capacity: supply required loads for 2 hours (loss of charger) at a minimum temperature of 60°F in the battery room.

Question 2

PK:

• Battery rooms have what type of Q-Class of exhaust fans for Temp/H2 control?
  
  • What is its suction and discharge path to?
  • What ESFAS signal(s) start the Essential fans?
• What normally cools DC Equipment Rooms?
• Control Bldg Normal AHU normally takes suction from where?
• What cools the DC Equipment and Battery rooms in a SIAS or LOP?

Answer 2

Control Building HVAC (Support System)

• Battery rooms have normal and essential exhaust fans (Temp / H2 control).
  
  • Suction from battery room / discharge directly to atmosphere.
  • Essential fans start on SIAS/LOP
• DC Equipment Rooms normally cooled by ESF Switchgear Room Normal AHU (WC).
• Control Building Normal AHU normally takes suction on each DC equipment room.
• SIAS or LOP: DC Equipment Room Essential AHUs (EC) cool DC Equipment and Battery rooms.

Question 3

PK:

Battery Chargers:

• How many normal & backup chargers per train
• list the Interlock(s)…What does it prevent?
• PK chargers are powered from?…
• Can the chargers be operated in parallel? why?
• Are chargers Load Shed? If yes, how fast (seconds) do they reclose?
  
  • What happens to the MCC contactor supplying the charger? can it be operated locally?

Answer 3

Class 1E 125 VDC Battery Chargers

• 1 normal charger per load center and 1 back-up charger per train.
• Mechanical interlock prevents aligning back-up charger to both control centers
• Powered from PHA/PHB
• Chargers cannot be operated in parallel (may cause damage).
• Chargers load shed by BOP-ESFAS, reclose in 5 seconds.
  
  • Opens MCC contactor supplying the charger, can be operated locally

Question 4

[PK system Ground Detection & MCR Indications]:

Ground Detection:

• Does PK alarm in MCR?
• Color of light at control center? Resets locally?
• Is PK grounded or ungrounded? Why?

MCR Indications:

• List MCR PK meters…
• The Battery Amps (gauge needle) goes To the right of zero… when it’s charging or discharging?
• What do the volts indicate about the output breaker?
• What are the 2 colors of the Back-up charger MCR indication lights? Which color shows which bus the spare charger is aligned to.

Answer 4

Ground Detection

• MCR alarm.
• White light lit at control center. Reset locally.
• Ungrounded system (Increased reliability. Need negative and positive ground to degrade the system.)

MCR Indications

• 125Vdc bus voltage
• Battery Amps (To the right of zero when discharging)
• Charger Amps/volts (volts will indicate if output bkr is tripped)
• Back-up charger lights (Red/Green). Red light will show which bus the spare charger is aligned to.

Question 5

PK:

State the PK MCR Alarms and its SESS Alarms (if any)…

Answer 5

125V IE CC M41 CHGR A/AC PNL D21 TRBL Alarm (each board has this alarm)

• Control center under voltage, ground or breaker trip
• Battery Charger problems (over or under voltage, AC supply voltage low, charger failure or reverse current)
• Distribution Panel overload

125V DC 1E CC M41 BAT BKR SESS Alarm (each board has this alarm)

• WHITE section (SEIS) LIT if Breaker Not Closed or inoperable (No SEAS alarm)

Question 6

PK:

Transfer Switches (App. R)

• What do they isolate for the Battery Chargers (Train A or B?) (Where is the switch located?)
• What do they isolate for the Batteries (Train A or B?) (Where is the switch located?)
• It also isolates the A Battery from which circuit breaker? (Where is the switch located?)

Answer 6

Transfer Switches (App. R)

• Isolates load shedding and sequence permissive relays, B01 voltmeters and ammeters for B train Battery Chargers (B, D, BD) (Switch is located at the MCC that supplies the charger)
• Isolates MCR breaker controls, voltmeters and ammeters for B train batteries (B, D). (Switch located at 125VDC Control Center)
• Isolates A Battery from the MCR circuit breaker switch (Switch is located on control center PKA-M41)

Question 7

PK:

• PK is control power to what equipment? ( and what happens if power is lost?…)
• PK provides DG control power and field flashing…
  
  • What happens to DG on loss of power?
  • If DG was running prior to loss of power, what happens to the DG engine and the output breaker? why?
• What happens to the Turbine Driven Aux Feedwater (TDAFW) MOVs and controls if PK is lost with AFA-P01 running?
• PK chargers power (thru inverters) SI-SDC isolation valves… Can the charger alone power these valves?(SIC-UV-653 & SID-UV-654)
• How does PK support the class inverters? If PK is lost, does the inverter Auto Transfer? (…where to?)

Answer 7

(PK) Supported Systems

• Control power to class switchgear and load center breakers and relays (non-functional if power lost)
• DG Control power and field flashing.
  
  • Loss of power: DG is not capable of starting.
  • If running prior to the loss, the engine would trip but the output breaker would remain closed (no control power).
• TDAFW MOVs and controls
  
  • If DC power is lost with AFA-P01 running, it may trip on over speed.
• SI: Supplies (thru inverters) SDC suction isolation valves.
  
  • Charger alone cannot provide sufficient power to operate SDC suction MOVs. Battery must be aligned (UV-653/654).
• DC source to the class inverters. If lost, inverter auto transfers to the AC supply.

Question 8

(PK) LCO 3.8.4 DC Sources – Operating (Modes 1-4)

• List the DC trains and its sub-channels…
  
  • What does each channel (normal or backup) include?
  • What makes a DC Bus operable?
• If 1 Charger INOP…
• LCO time in hours if 1 DC electrical subsystem INOP (reasons other than condition A)?
• LCO time if both DC power systems INOP? (can it be entered voluntarily?)
• SR 3.8.4.1: Terminal voltage ≥ ?
  
  • Based on what? Min float voltage per cell?
• LCO 3.8.5 (shutdown) requires what type of source (DC or AC?) to support which LCO #? (Same actions as 3.8.2?)

Answer 8

(PK) LCO 3.8.4 DC Sources – Operating (Modes 1-4)

• Train A and Train B DC electrical power subsystems
  
  • Train A (Channel A and C) / Train B (Channel B and D)
  • Each channel includes 125 Vdc bus, battery bank, and charger (normal or back-up)
  • Operable: all batteries and respective chargers operating and connected to the associated DC bus(es).
• One Charger inoperable:
  
  • Restore terminal voltage within 2 hours
  • Verify float current ≤ 2 amps every 12 hours (battery is re-charged, battery declared inoperable if not met)
  • Restore the charger within 72 hours or RICT
• 2 hours or RICT: One DC electrical power subsystem inoperable for reasons other than Condition A (one charger inoperable).
  
  • Example: two chargers inoperable on same train or battery inoperable
• Both DC power subsystems inoperable: restore one within 1 hour OR RICT (cannot voluntarily enter)
• SR 3.8.4.1: Terminal voltage ≥ 130.2 Vdc
  
  • Based on the nominal design voltage of the battery. Consistent with the minimum float voltage (2.17 Vdc per cell) times the number of connected cells or 130.2 V for a 60 cell battery at the battery terminals.
• LCO 3.8.5 (shutdown) requires DC source to support LCO 3.8.10 (same actions as 3.8.2)

Question 9

(PK) ​LCO 3.8.6 Battery Parameters:

• Battery limits to be Operable?
• Float current is ≤ ? amps (…not required to be met if terminal voltage is low)
• Cell float voltage is > ? Volts.
• Electrolyte level ≥ ? mark on battery cell jar.
• Pilot cell temperature is ≥ ?°F.
• Battery capacity is ≥ ?% (test discharge)
• Immediately declare Battery inoperable (& enter LCO 3.8.4 condition B):
  
  • Cell float voltage ≤ ? Volts and float current > ? amps.
  • Or if what conditions/parameters not met?

Answer 9

(PK) ​LCO 3.8.6 Battery Parameters:

• Batteries shall be within limits when required to be operable.
• Float current is ≤ 2 amps (not required to be met if terminal voltage is low)
• Cell float voltage is > 2.07 V.
• Electrolyte level ≥ level indication mark on battery cell jar.
• Pilot cell temperature is ≥ 60°F.
• Battery capacity is ≥ 80% (test discharge)
• Immediately declare Battery inoperable (enter LCO 3.8.4 condition B):
  
  • Cell float voltage ≤ 2.07 V and float current > 2 amps.
  • Or other conditions not met (parameters not restored in time)

Question 10

(PK) ​​LCO 3.8.9 Distribution Systems – Operating (Modes 1-4):

• List the trains that shall be operable…
• Can a DC subsystem be considered OPERABLE if it’s energized (@ proper voltage) from its battery or charger?
• How long to restore (time in hours)?

Answer 10

(PK) ​​LCO 3.8.9 Distribution Systems – Operating (Modes 1-4)

• Train A and Train B AC, DC, and AC vital instrument bus electrical power distribution subsystems shall be operable
• Operable DC electrical power distribution subsystems require the associated buses to be energized to their proper voltage from either the associated battery or charger.
• All 125Vdc Control Centers and Distribution Panels are required.
• Restore in 2 hours or RICT

Question 11

(PN) Class 1E Inverters:

• Includes which transfer switches?
• List control centers?…
• Bus voltage limits?…
• Frequency range?…

Answer 11

(PN) Class 1E Inverters:

• Includes both static and manual transfer switches
• Inverters powered by associated 125 Vdc PK Control Center (PKA-M41/PKB-M42/PKC-M43/PKD-M44)
• Converts (inverts) 125 Vdc to 120 Vac
• Bus voltage limit: 118 - 126 Vac
• Frequency: 59.5 - 60.5 Hz

Question 12

(PN) Static Switch:

• Electronic, solid state assembly.
• On loss of normal power (inverter), does it auto transfer?….
• Does it Auto transfer back?…
  
  • ​which 2 buttons pressed to transfer manually?…
• • Auto transfers to the voltage regulator:
    
    • ?…
    • ?…
    • ?…
• Green light – means…?…
• Amber light – means…?…

Answer 12

(PN) Static Switch:

• Electronic, solid state assembly.
• On loss of normal power (inverter), automatically transfers the distribution panel to the voltage regulator.
• Does NOT transfer back automatically.
• Distribution panel can be manually transferred by pushing one of the two pushbuttons:
  
  • INVERTER TO LOAD (Aligns to the inverter)
  • BYPASS SOURCE TO LOAD (Aligns to the voltage regulator)
• Auto transfers to the voltage regulator:
  
  • Loss of the square wave to the harmonic filter.
  • Low inverter voltage to the static switch (~50% voltage)
  • Inverter output overload (120% inverter load ~200 Amps)
• Green light – INVERTER SUPPLYING LOAD
• Amber light – BYPASS SOURCE SUPPLYING LOAD

Question 13

(PN) Voltage Regulator (480/120Vac regulating XFMRs):

• Are they backup or normal?
• Power: ? (MCCs…)
• MCC contactor is load shed on what?… recloses?…

Answer 13

(PN) Voltage Regulator (480/120Vac regulating XFMRs):

• Backup power supply for each channel
• Power: PHA/PHB
• MCC contactor is load shed on a LOP, contactor recloses 5 seconds after power restored

Question 14

(PN) LCO 3.8.7 Inverters – Operating (Modes 1 – 4)

• Train A and Train B inverters shall be operable in which modes?…
• ?…

Answer 14

(PN) LCO 3.8.7 Inverters – Operating (Modes 1 – 4)

• Train A and Train B inverters shall be operable in Modes 1-4
  
  • One inoperable - 7 days or RICT
  • If PN is de-energized, immediately enter LCO 3.8.9 (3.0.6 exception)
  • > 1 inverter inoperable – restore in 1 hour or RICT (cannot voluntarily enter)
• Operable inverter: AC vital instrument bus to be powered by the inverter with output voltage and frequency within tolerances, and power input to the inverters from a 125 Vdc battery.
• One inverter may be disconnected from its associated DC bus for ≤ 24 hours to perform an equalizing charge if:
  
  • Bus is energized from its Class 1E constant voltage source regulator; and
  • All other buses are energized from their associated operable inverters.
• LCO 3.8.8 (shutdown) requires inverters to support LCO 3.8.10 (same actions as 3.8.2)
• If inverter is inoperable (Cond A entered):
  
  • Do not perform planned maintenance on associated train DG
  • Do not perform planned maintenance on another RPS/ESFAS channel that puts that channel in trip

Question 15

(PN) LCO 3.8.9 Distribution Systems – Operating (Modes 1 – 4):

• ?…

Answer 15

(PN) LCO 3.8.9 Distribution Systems – Operating (Modes 1 – 4):

• All four boards required.
• Operable 120Vac board: energized to proper voltage from the inverter OR voltage regulator.
• One 120V bus inoperable – Restore in 2 hours or RICT

Question 16

(NK) NK Batteries:

• Normal operating voltage?…
• How long do they supply power?…
• MCR indications for NK?…

Answer 16

(NK) NK Batteries:

• Normal operating voltage _~ 135 Vd_c
• Supply power for 2 hours following a loss of charger
• Ratings: E - 2380 Amp-Hours / F - 3460 Amp-Hours
• Battery breakers have MCR and local controls / indications

Question 17

(NK) NK Battery Chargers (E, E-1, EF, F, G):

• Interlocks?…
• Preferred method to swap chargers?… If chargers are having problems, then use which method?…
• ?…

Answer 17

(NK) NK Battery Chargers (E, E-1, EF, F, G):

• Backup charger (EF) output breakers have a mechanical interlock
• EF Charger output breakers have MCR lights
• Preferred method for swapping chargers is to place them in parallel before removing one. In the case where the in-service charger is having problems the preferred method is to remove the in-service charger first and then place the new charger in service.
• Battery breakers must be closed prior to swapping chargers, reduces voltage transient.

Question 18

(NK) Control Centers (NKN-M45, NKN-M46) (& Ground Detection):

• Normal bus voltage: #? Vdc
• Bus voltage limit (range) ? Vdc
• Motor and feeder breakers:
  
  • ?…

Ground Detection

• Soft ground – MRC Alarms?
• Hard ground – MCR Alarms?
• How to reset ground relay?

Answer 18

(NK) Control Centers (NKN-M45, NKN-M46):

• Normal bus voltage: 130 – 135 Vdc
• Bus voltage limit 105 - 139.8 Vdc
• Motor and feeder breakers:
  
  • Manually operated
  • Inverse time thermal overload protection (higher the current the shorter the time delay)
  • Instantaneous magnetic short-circuit protection

Ground Detection

• Soft ground – NO MCR alarm. Yellow light on the ground detection assembly and white light at the Control Center.
• Hard ground – MCR alarm. Yellow light on the ground detection assembly and a white light at the Control Center.
• Ground relay must be RESET locally. RESET pushbutton is provided that is used to reset this relay when the condition clears.
• Ground relay TEST push button on NKN-M45. NOT provided on NKN-M46.

Question 19

(NK) NK Panels, Locations, Loads:

• Panel
  
  • (Location?)
  • Loads?
• D41
  
  • ?
• D42
  
  • ?
• D43
  
  • ?
• D44
  
  • ?
• D45
  
  • ?
• D19
  
  • ?

Answer 19

(NK) NK Panels, Locations, Loads:

• Panel
  
  • (Location)
  • Loads
• D41
  
  • (Turb Bldg 100’)
  • Switchgear control power
  • Main Generator auxiliaries
  • Turbine Building HVAC control
• D42
  
  • (Aux Bldg 100’)
  • Switchgear control power
  • Radwaste annunciators
  • Motor Operated Disconnects
  • Plant annunciators
• D43
  
  • (Turb Bldg 100’)
  • Oscillograph
  • Turbine Protection
  • Transformer annunciators
  • Plant annunciators
• D44
  
  • (In NKN-M46)
  • RCP Breaker control
• D45
  
  • (In SSR Room)
  • SSO Cabinet
• D19
  
  • (Chlorinator Building)
  • Control Power to Cooling Tower area load centers

Question 20

(NN) Ground Detection (& Alarms):

• D11 and D12 are ungrounded or grounded?…

120VAC PNL D11/D12/D15/D16 TRBL alarm

• ?

Ground detection on NNN-D15/D16?

Answer 20

(NN) Ground Detection:

• D11 and D12 are ungrounded and contain a ground fault detection system
  
  • Ground fault relays actuates a local RED light and MCR alarm.
  • Reset push button on the distribution panel.
  • RED light will stay illuminated until the ground is cleared and reset button pressed.
• Powered from non-class 125Vdc (NKN-D42)

120VAC PNL D11/D12/D15/D16 TRBL alarm

• Ground (NNN-D11 and D12 ONLY)
• Undervoltage (100 Vac)
• Breaker overload trip (main feed or load breakers)

No ground detection on NNN-D15/D16

Question 21

(NN) Static Transfer Switch:

• Auto transfers to emergency at what voltage drop level?…
• Auto transfers to normal if emergency source is?…
• Explain Manual Bypass Switch?…
• Preferred transfer method?…

Answer 21

(NN) Static Transfer Switch:

• < 90 Vac: Auto transfers to emergency
• Auto transfers to normal if emergency source is lost and normal is available.
• Manual transfer back to normal.
• Break before make transfer (~ 4 cycles).
• Can be bypassed with a Manual Bypass Switch
  
  • Break before make
  • Requires SM permission to operate
  • Used to remove the static XFR switch from service
  • Normally in AUTO
• Transfer to Emergency pushbutton is the preferred transfer method. (manually shifts the static XFR switch)

Question 22

(NN) Panel, Location, Normal Power Supply, Emergency Power Supply:

Panel

1. (Location)
2. Normal power supply
3. Emergency power supply

D11

1. ?

D12

1. ?

D15

1. ?

D16

1. ?

Answer 22

(NN) Panel, Location, Normal Power Supply, Emergency Power Supply:

Panel

1. (Location)
2. Normal power supply
3. Emergency power supply

D11

1. (Cont Bldg 120’)
2. NHN
3. PHA-M31

D12

1. (Cont Bldg 120’)
2. NHN
3. PHB-M32

D15

1. (Turb Bldg 100’)
2. NHN
3. NHN-M19 (load shed)

D16

1. (Aux Bldg 120’)
2. NHN
3. NHN-M20 (load shed, U1/U2 ONLY)

• [PHB-M38 (U3 ONLY)]

Question 23

Purpose / design:

• ?…

Voltage Regulators (VRs)

• ?…

Answer 23

Purpose / design:

• 120 Vac, single phase, 60 Hz regulated/filtered Non-essential reactor/auxiliary control/instrumentation (ungrounded supply) [D11/D12]
• BOP loads (grounded supply) [D15/D16]

Voltage Regulators (VRs)

• Single phase regulator XFMRs (480 to 120 Vac)
• Produces regulated / filtered 120Vac
• NNN-D15/D16 VRs are grounded