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NLO Systems > NA/NB/NG/NH/NK/NN/NQ- Non class electrical > Flashcards

NA/NB/NG/NH/NK/NN/NQ- Non class electrical Flashcards

1
Q

What happens when (125 VDC) NK system is lost?

A

-13.8kV breakers lose control power and breakers fail as is.

NKN-M45:

  • main turbine trip coils lose power and turbine trips
  • RCPs fast bus transfer unavailable
  • SBCVs cant operate
  • S/G safety valves will lift until ADVs are opened
  • locally trip MFWPs
  • locally stop Aux. building AHUs
  • locally align back-up power to NKN-U45
  • locally monitor condenser hotwell level

NKN-M46:

loss of emergency oil pumps

NKN-D19:

loss of cooling tower fans from control room

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2
Q

What do the lights indicate on 480 vac MCC’s?

A

Energization state of load, not position of breaker.

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3
Q

At what temperature do most transformer cooling fans and/or oil pumps turn on? Which one is different?

A

70* C/75*C

Site power transformer (90/95 C)

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4
Q

How many cooling fan power supplies do 4160 vac transformers have?

A

Two.

Normal and Alternate.

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5
Q

Are transformer cooling fans power seeking?

A

Yes

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6
Q

What are the conditions for fast bus transfer for the NA system?

A

Initiating:
Main generator trip
Aux transformer fault

Conditions:

  • CR B01 handswitch in auto
  • NAN-S01/S02 supply breaker opens and early B contact closes and closes tie breaker (no 86 lockout on any breaker)
  • Sync check for S01 and S03/S02 and S04
  • S03/S04 checked for voltage and freq.
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7
Q

What is special about the site power (OSF) transformer?

A

Buchholz relay (oil filled bushings) has upper & lower mechanical mercury switch

Cooling fans and oil pumps turn on at 90C/95C

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8
Q

What is the design and purpose of the NN (non-class 120 VAC instrument power) system?

A

Supplies single phase, 60 Hz, regulated and filtered power to four non class instrumentation and controls subsystems

each subsystem consists of:

normal supply voltage regular, backup supply regulator, static transfer switch between voltage regulators, and a distribution panel-NNN-D11,12,15,16

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9
Q

Describe the flow path of the NN (non class 120 VAC instrument power) system.

A

480vac mcc stepped down to 120vac through voltage regulators, then through static transfer switch which selects the power source (power seeking), then to one of four Distribution panels.

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10
Q

What is the purpose and operation of the static transfer switch in the NN system?

A

to switch supply power from normal to emergency (non class, class bus or SIAS shed load panel, breaker and unit dependent)

  • has push buttons (transfer to Emerg. and transfer to norm.),
  • indicating lights (green is norm, red is emerg.),
  • three position manual bypass switch.

When the selected power source is lost or there Is under-voltage, auto transfers to other power source as long as manual bypass switch in is auto

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11
Q

Purpose and operation of the NN manual bypass switch.

A

to transfer and lock the selected power supply to the NNN bus.

  • Auto- aligns the Distribution panels to the output of the static switch.
  • Manual transfer to normal- aligns the D-panel directly to the normal source.
  • Manual transfer to emergency- aligns D-panel directly to the emergency source.

If switch not in auto, no auto transfer will happen on a power loss

Rotating switch to auto will result in temp loss of power to NNN.

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12
Q

What is the purpose and operation of voltage regulators in the NN system?

A

normal and emergency source step down transformer that steps down voltage from 480vac to 120vac

accepts varying ac input and produces well regulated, filtered ac output

Back up regulators can be supplied by the diesel generators.

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13
Q

What is the purpose, operation and location of the NN Distribution panels?

A

NNN-D11,12 provide power to reactor control instrumentation and other service loads

NNN-D15,16 provide power for Balance of Plant and misc. service loads

manually operated at local D-panels

D11,12 are ungrounded with ground detection, red ground light and reset button

D15,16 are grounded

Locations:

  • D11,12-control building 120’
  • D15-turbine building 100’
  • D16-aux building 120’
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14
Q

Where do the NN distribution panels get their power from in units 1,2 and 3?

A

In all units, normal power is from non class MCC’s.

In units 1 and 2, back up power for D11,12 is from class MCC’s. D15,16 back up power is from SIAS load shed MCC’s

In unit 3, D11,12,16 back up power is from class MCC’s and D15 back up power is from a SIAS load shed MCC.

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15
Q

Purpose and design of the NQ (uninterruptible power) system.

A

Provides 120VAC uninterruptible power supply to the plant monitoring system (plant computer)

Static transfer switch consisting of inverter and two transformers, two isolation transformers, and two Distribution panels NQN-D01,2

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16
Q

Describe the flow path of the NQ (uninterruptible power) system

A

NQN-D01:

Normal power is from NKN-M45, through DC/AC inverter, to static transfer switch, through normally lined up manual bypass switch, to isolation transformer NQN-X01, to NQN-D01.

Alternate power is from one of two MCC’s, one normal and one SIAS load shed MCC, through a manual transfer switch, to a step-down transformer, to a voltage regulating transformer, then to either an alternate side of static transfer switch or the manual side of the manual bypass switch, to isolation transformer, to NQN-D01.

NQN-D02:

From MCC to step down transformer, NQN-D02.

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17
Q

What system does NQ designate?

A

Uninterruptible power for Plant monitoring system

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18
Q

What system does RJ designate?

A

Plant monitoring system

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19
Q

What powers the plant monitoring system?

A

120VAC from NQ

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20
Q

What are the NQ system interfaces?

A 
NH
NK
HJ (control building HVAC)
RJ
ERFDADS
MA
NA
QK
SC
LO
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21
Q

What is the purpose, operation and location of the NQ system inverter?

A

provide 120VAC power to PMS

Changes the NKN-M45 125VDC power to 120VAC

NQN-N01C1 panel, control building 120’ inverter room.

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22
Q

What is the purpose, operation and location of the static transfer switch in the NQ (uninterruptible power) system?

A

auto transfers from normal DC power supply to AC power supply

In the loss of normal power, the switch will transfer power to the alternate source without interrupting power feed.

Push buttons for manual switching.
Indicating lights show which source is supplying NQN-D01

control building 120’ inverter room

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23
Q

What is the purpose, operation and location of the manual bypass switch in the NQ system?

A

Bypasses the operation of the static transfer switch and locks the power in the alternate power source line up.

Switch is either in “normal operation” or “alternate source to load”. Alternate source to load bypasses the static transfer switch and provides AC power.

control building 120’ inverter room

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24
Q

What is the purpose, operation and location of the step down transformer in the NQ system?

A

Provides alternate 120VAC power to NQ

Primary 480VAC source from non class MCC, alternate source is non class SIAS load shed MCC NHN-M72, steps down the 480vAC to 120VAC to the voltage regulator.

Transformer is located in the control building 120’ inverter room

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25
Q

What is the purpose, operation and location of the voltage regulator in the NQ system?

A

Produces regulated, filtered 120vac output.

control building 120’ inverter room

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26
Q

What is the purpose, operation and location of the isolation transformer in the NQ system?

A

Eliminates electrical noise due to switching and leakage currents.

control building 120’ inverter room

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27
Q

What is the purpose, operation and location of the distribution panel NQN-D01 in the NQ system?

A

Provides non class 120VAC uninterruptible power to the PMS loads

control building 120’

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28
Q

What is the purpose, operation and location of the NQN-D02 in the NQ system?

A

Provides 120VAC

480VAC from non class mcc stepped down to 120VAC to loads in subsynchronous Resonance Room (SSR Room)

Turbine building 100’ SSR Room

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29
Q

What is the purpose, operation and location of the turbine subsyncronous Resonance (SSR room) system transformer, NQN-X17, in the NQ system?

A

Provides 120VAC stepped down from 480VAC

Turbine building 100’ SSR Room

30
Q

What are plant impacts when the NQ system is lost completely?

A

static transfer switch will swap to alternate power source

if NNN-D01 is lost completely, Plant computer and core monitoring system is lost, no reactor trip.

if there is a LOOP, manual transfer to NHN-M72 for DG power supply

31
Q

Describe the purpose, operation and location of the start up transformers, AE-NAN-X01/02/03.

A

Connect the switchyard to the units providing 525kV off-site power

Provides normal and alternate power sources for the NAN-S05/06 switch gear at each unit. (Each transformer has four outputs.)

Start up yard, true north side of the SRP switch yard.

32
Q

Describe the open phase protection modification for the start up transformers

A

Two independent/redundant cabinets for each transformer. Each cabinet has an active and a passive open phase detection system.

Active system injects a current into a neutral of the transformer and if the signal changes, there is an open phase.

passive system detects faults that are of low impedance.

Any of the open phase faults would trip two lock out relays at the cabinet

33
Q

Describe the purpose, operation, and location of the OSF (site) transformer, AE-ZYN-X05.

A

Reduces the 525kV from switchyard to 12.47kV and sends that power to the OSF

Start up yard

34
Q

Describe the purpose, operation and location of the NA (non-class 13.8kV ) switchgear

A

Takes 525kV off-site power and 24kV main generator power and supplies it to both class and non-class 4160v, 480v and large pumps

All units have NAN-S01 through -S06. They deliver power from off-site or the main generator to all house loads

Large breakers with local controls, protective relays, lights and are operated from the control room

NAN-S05/06 are in the start up yard
NAN-S01/02 are in the non-class switchgear room, turbine building 100’
NAN-S03/04 are outside, south side of the turbine building

35
Q

Describe the normal operation of the NA (non-class 13.8kV) system.

A

Start up transformers supply power to the NAN-S05/06 buses, supplying power to NAN-S03/04, supplying power to the ESF transformers, NBN-X03/04, then to the class 4160V buses, PBA-S03/PBB-S04

Main generator provides power to the unit Aux. transformer, then to NAN-S01/02

When power is down or coming up, NAN-S01/02 will be powered through NAN-S03/04 via tie-breakers.

Unit one only also supplies 13.8kV to Water Resources, TSC, and the 480V Load centers in the switchyard.

36
Q

Describe how the loss of the NA (non-class 13.8kV) system impacts the plant

A

Losing NAN-S01/02 would cause a reactor trip due to losing the RCP’s and would also lose the associated buses’ load centers, MCC’s, and normal service transformer going to the NB system.

Losing NAN-S05/06 would cause the loss of power to NAN-S03/04 (ESF transformers), which is the normal power source to the PB system. Unit 1, normal power to WR, TSC and switch yard loads are lost, too.

37
Q

Describe how the NA (non-class 13.8 kV) system responds to the loss of its associated support systems.

A

If NK is lost, 13.8kV breakers lose control power

If the associated MCC’s are lost, transformer and bus cooling fans are lost and the transformer or bus would overheat and fail.

38
Q

What equipment in the NA (non-class 13.8kV) system is tech spec related while operating?

A

Two start up transformers, NAN-X01/02/03, providing power to intermediate busses and both trains of the units intermediate busses NAN-S05/03 and NAN-S06/04

39
Q

What equipment in the NA (non-class 13.8kV) system is tech spec related while shut down?

A

One start up transformer for the shutdown unit, NAN-X01/02/03
And one train of intermediate busses for the shutdown unit, NAN-S05/03 or NAN-S06/04

40
Q

What is the purpose of the NB (non-class 4160v) system?

A

Receives power from the 13.8kV busses through the normal service transformers, NBN-X01/X02, and sent to all non-class 4160 loads

Each unit’s Non-Class 4.16 KV power system is divided into two parts arranged so that the possibility of a forced shutdown due to loss of one part will be minimized. Each of the two parts supplies a load group including approximately half of the unit auxiliaries.

41
Q

What is the flow path of the NB (non-class 4160v) system?

A

13.8kV stepped down by NBN-X01/02 and sent to NBN-S01/02, then to non-class (non-safety related) loads. Tie-breaker between NBN-S01//02 to provide alternate power.

42
Q

Describe how the loss of NN (non-class 120VAC instrument power) system impacts plant operation.

A

Losing NNN-D11,12 causes a loss of:

  • RCS equipment,
  • loss of letdown,
  • make up to VCT is lost and charging pump suctions transfer to RWT,
  • reactor power cutback,
  • steam bypass control valves,
  • plant should stabilize.

Losing NNN-D15,16 causes main feed pumps rpm to drop to 300 and plant should stabilize

43
Q

What is the purpose of the NK (non-class 125VDC) system?

A

To provide control power to the NA, NB, NG systems and is the normal power source for NQN-D01

NK consists of three independent subsystems, E, F and G.

44
Q

Describe the flow path of the NK (non-class 125 VDC power) system.

A

480VAC from NH system feeds power to the battery chargers, E, F, E/F, and E1.

Then to the NKN-M45/46 busses, supplying power to the E and F batteries. M45/46 also supply various D-panels, trip circuits, the NQN inverter, control power to NAN-S05/06 busses and emergency oil pumps.

45
Q

Describe the purpose and operation of the NK (non-class 125VDC) battery chargers.

A

Converts 480VAC to 135VDC to supply non-class batteries and DC loads.

Toggle switch on the battery chargers controls whether it is in Float or Equalize mode. Float maintains 135VDC and Equalize maintains 139.8 VDC to recharge batteries.

There is an adjustable 24 hour internal equalizing timer is provided for
setting termination of the Equalizing charge.

46
Q

What is the purpose and operation of the NK (non-class 125VDC) batteries?

A

Batteries Supply voltage to DC loads for 2 hours following loss of NH to battery chargers.

When the batteries are being charged they naturally produce hydrogen. To prevent hydrogen concentrations from existing in explosive mixtures, Battery Room ventilation must be operating at all times.

Individual battery cell water level should be maintained within the two lines

47
Q

Describe the purpose and operation of the NK (non-class 125VDC) control centers

A

NKN-M45/46 provide control power for non-class equipment, transfer switches for NAN-S05/06, normal power source for the plant computer, trip circuits for the main generator, and emergency oil pumps.

Ground detection, hard ground= <2k ohms and soft ground is 2k ohms-35k ohms.

48
Q

Which transformers have forced oil pumps?

A

start up transformers, aux transformers and main transformers

49
Q

How many alarm annunciators are on each large transformer?

A

Start up xfmr: 12
ESF xfmr: 12
unit aux xfmr: 12
Normal Serv. xfmr: 12

50
Q

What is the purpose of the Buchholz relay on the OSF transformer?

A

If gas is developed in the transformer the oil in the top of the relay is displaced
actuating an alarm. If a large amount of gas is present the rising gas displaces the oil from the bottom causing a trip of the transformer.

51
Q

What is the output voltage of the OSF (site) transformer?

A

12.47 kV

52
Q

What are the indicating lights for on the large switchgear?

A

red-closed and trip coil energized
green-open
white-lockout relay energized
clear-closing spring charged

53
Q

At what reactor power is the main generator paralleled with the grid? When is the main turbine paralleled onto the NAN-S01/-S02 buses? When is the reactor and main generator tripped?

A

12%

16-20%

20%

54
Q

What is the purpose of the normal service transformers? How are they cooled? Where are they located?

A

step down transformers that convert non-class 13.8 kV power from NAN-S01/-S02 to 4.16 kV power for use by NBN-S01/-S02.

natural circ oil, forced air @ 70 degrees = all fans on

south side of the turbine building outside

55
Q

What are the fuses in the large switchgear breakers for?

A

UC-closing
UT-tripping
UA/UE-control room
UL-lifting

56
Q

What are the repercussions of losing NBN-S01/-S02 at 100% power?

A

S01-reactor trip due to loss of two CD pumps and a heater drain pump

S02-reactor power cutback due to loss of one CD pump and one heater drain pump

57
Q

Where do the NAN-S01/-S02 and NBN-S01/-S02 buses fast bus transfer to?

A

NA to S03/S04

NB to the opposite bus via cross tie

58
Q

What system supplies power to the NG/NH system?

A

NAN-S01/-S02 to NG

NG to NH

59
Q

What is the horse power ratings for NG and NH breakers?

A

NH is less than 50HP

NG is more than 50HP

60
Q

How many load centers can a NA breaker supply? How many MCCs can each load center feed?

A

three

three

61
Q

How does the 480 VAC non-class system interface with the PG system?

A

powers the non-class SIAS load shed MCCs

62
Q

On all load centers, what is the main feeder breaker?

A

B2

63
Q

How are all the 13.8kV to 480V transformers within the Protected area cooled? At the cooling towers?

A

fan-less air cooled

natural circ. oil

64
Q

What is the purpose of the Kirk Key Interlock?

A

This interlock requires the 480V Main Feeder Breaker must be ‘Tripped’
and ‘locked open’ before the 13.8kV Load Interrupter (Disconnect) Switch can be opened. This is a safety feature that prevents opening the Interrupter Switch while it is under load. This also allows for one bus to be taken out of service at a time.

65
Q

What is the purpose of the blue light on the CW load center breakers?

A

indicate a fan tripped on high vibration

66
Q

If an MCC were to lose power, all the indicating lights will be out. Why is this?

A

the control power comes from the same source as the power input

67
Q

What is the difference between the three NK subsystems, E, F and G?

A

G doesn’t have a control center, just a distribution panel

68
Q

Can an NK swing charger be connected to both buses at the same time? When is the only time you can momentarily parallel the chargers to a bus?

A

No, a mechanical interlock on the output breakers of the swing chargers prevent simultaneous closing of both breakers, thus paralleling the buses together

while putting a new charger in-service to a bus (make before break), unless the in-service charger is indicating problems

69
Q

What is the purpose of the Air Circuit Breakers for the NK batteries?

A

they connect/disconnect the batteries to the NK buses

70
Q

Where are the D-panels located in the NK system?

A 
D41-turbine building 100'
D42-Aux. building 100'
D43-Turbine building 100'
D44-on the back of NKN-M46
D45-SSR room turbine building 100'
D19- Chlorinator building, cooling tower #1
71
Q

What indications are on the NK batteries chargers?

A

AC pilot lamp illuminates when 480V AC voltage is applied to the Charger

A DC Voltmeter and DC Ammeter are provided to give a visual indication of
the DC output.

72
Q

What does the NN static transfer switch indication tell you?

A

position of the static transfer switch, not the power source

NLO Systems (66 decks)

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