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Systems > Non-class 125vDC Control power (NK) > Flashcards

Non-class 125vDC Control power (NK) Flashcards

1
Q

Describe the purpose of the Non-class 125vDC control power(NK).

A

•Provides reliable 125vDC to all connected loads
•Provides 2hrs of 125vDC on a loss of AC power to (NK) to support shutdown of the secondary plant.

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2
Q

What does the Non-class 125vDC(NK) system consist of?

A

3 independent subsystems:
• ‘E’ subsystem
- Two dedicated battery chargers
-One battery
-125vDC MCC with a control panel

• ‘F’ subsystem
-One dedicated battery charger
-One battery
-125vDC MCC with a control panel

  • ‘EF’ battery charger (Swing Charger) to be aligned to M45 OR M46

• ‘G’ subsystem
-One battery charger
-One battery
-125vDC distribution panel

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3
Q

What kind of systems are the NK subsystems designed for? (Grounded or ungrounded)

A

•They are designed for UNgrounded systems .

•’Ungrounded’ systems require grounds in both the positive and negative bus simultaneously before losing the system. (More reliable)

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4
Q

What rectifies the 480v MCC power to 135vDc power in the (NK) system?

A

•The battery chargers rectify the 480v MCC power into 135vDC power.

Only the batteries supply 125vDC

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5
Q

Describe the normal power path for ‘E’ subsystem

A

•NHN to ‘E’ or ‘E1’ battery chargers rectified 135vDC
E1 may be manually connected to NKN-M45 if ‘E’ is not available

•Supplies power to NKN-M45 which powers:
- ‘E’ battery
-NQN- inverter
- NKN-D41
-NKN-D42
-NKN-D43
- Main Gen. Trip Circuit
-Main Gen. Back Up Trip Circuit
-NKN-U45 (Normal)(NAN-S05)
-NKN-U46(Alt)(NAN-S06)

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6
Q

Describe the power path of ‘E1’ battery charger.

A

The same as the ‘E’ battery charger power path.

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7
Q

Describe the ‘F’ battery charger power path.

A

•NHN powers ‘F’ battery charger
•Gets rectified into 135Vdc that powers NKN-M46 which supplies:
-‘F’ battery
-NKN-U46 (Norm)
-NKN-U45(Alt)
-NKN-D44
-NKN-D45
-FW ‘B’ pump/turbine ELOP
-FW ‘A’ pump/turbine ELOP
-Main Gen. ESOP
-Main turbine EBOP

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8
Q

Describe the power path of the Swing Charger ‘EF’ battery charger.

A

•It can either be aligned to NKN-M45 or NKN-M46 but mechanically interlocked so it cannot feed both at the same time.

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9
Q

Describe the power path for ‘G’ battery charger.

A

• ‘G’ battery charger is powered FROM NHN system.
•Rectified into 135vdc which powers NKN-D19 which supplies:
-‘G’ battery
-Cooling tower Load Centers

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10
Q

Where does the control power supplied to the Switchyard come from?

A

•NAN-S05 control power comes from NKN-U45

•NAN-S06 control power comes from NKN-U46

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11
Q

Describe the non-class battery chargers and what they do.

A

•3phase, constant voltage, fully automatic unit.

•Rectifies 3phase 480v MCC into 135vDC to supply loads and charge the associated battery.

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12
Q

What does the toggle switch do on the battery charger?

A

•Determines the mode it’s in either:

  • ‘Float’ operation which will supply loads at 135vDC and maintain the battery charged
  • ‘Equalize’ operation which supplies the loads at 139.8vDC to the loads and CHARGES the batteries following a discharge.
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13
Q

How many breakers do the regular battery chargers have?

A

•One Ac input breaker
•One DC output breaker

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14
Q

How many breakers does the Swing charger have?

A

•One input breaker
•Two output breakers
Output breakers are mechanically interlocked to prevent paralleling

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15
Q

What happens if AC power is lost to the battery chargers?

A

•The batteries supply NKN-M45 and NKN-M46 will 125vDC power for only 2hrs

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16
Q

Where are the alarms on the battery charger?

A

•They are inside the battery charger cabinet.

17
Q

When should you swap to the back-up battery chargers?

A

•If you just wanna swap for fun then parallel them first then secure one.

•If you NEED to swap because one is showing signs of faults then secure faulty one before swapping.

18
Q

Describe ‘Equalizing Charge’

A

•Equalizing charge supplies 139.8v to loads and to the battery to recharge it.

19
Q

Describe the purpose of the Non-class batteries.

A

•Supply 125vDC power to their DC MCC’s (NKN-M45 & M46) for TWO hours following a loss of AC power source.

20
Q

How many cells does a battery consist of and what’s the build like?

A

•60 cells connected in series.
•Lead-calcium type
•Explosion resistant vent plugs (Flame arrestors)

21
Q

How is a battery normally maintained?

A

•Normally maintained in a Float charge of 135vDC.

22
Q

How is a batteries charge configured after it’s been discharged?

A

•It is supplied an equalizing charge of 139.8vDC until it is recharged.

23
Q

What happens when a battery is charged and what is the by-product?

A

•Electrolysis happens and hydrogen is created. (Bad news)

24
Q

What two things prevent incidents from hydrogen?

A

•The battery room exhaust fans must always be running

•The flame arrestors must be installed

25
Q

What do the battery racks do?

A

•Have an acid resistant coating and securely hold the batteries

26
Q

What does Non-Class DC MCC NKN-M45 supply power to?

A

Supplies power to:
• ‘E’ battery
• NQ inverter
• NKN-D41
• NKN-D42
•NKN-D43
•Main Gen. Trip circuit
•Main Gen. BU trip circuit
• NKN-U45(normal)
•NKN-U46 (Alt)

27
Q

What does the Non-class DC MCC NKN-M46 supply power to?

A

NKN-M46 supplies power to:
• ‘F’ battery
• NKN-D44
• NKN-D45
•NKN-U46(normal)
•NKN-U45(Alt)
•FW ‘B’ pump/turbine ELOP
•FW ‘A’ pump/turbine ELOP
•Main Gen. ESOP
•Main turbine EBOP

28
Q

What does the Non-class DC distribution panel NKN-D19 supply?

A

NKN-D19 supplies:
• ‘G’ battery
• Cooling tower Load centers

29
Q

What’s on the ‘Control Cabinet’ for the NKN system?

A

•Indications (volts & current)
•Voltmeter selector (ground readings)
•Ground relay and reset
•Open/close pushbuttons for battery breaker
•Indicating lights:
-Breaker position
-Bus under voltage
-Bus ground detection

30
Q

Describe ‘Ground Detection’ on NKN-M45 and NKN-M46.
NKN MCC section

A

Two ground alarms:
-Soft ground~ <35kohms but >2kohms is a soft ground alarm. No control room alarm

-Hard Ground~ 2kohms or Less is a hard ground alarm and Control does get an alarm.

31
Q

What does the battery breaker compartment do?
NK MCC section

A

• What holds the breaker itself

32
Q

Describe Motor Control Center breakers.

A

•Manually operated molded case circuit breaker.
• 3 positions (ON, OFF, or Tripped)
-Protective Features
•Thermal OL
•Instant short-circuit protection.

33
Q

What prevents condensation and moisture in the NKN-MCC?

A

•Space heaters

34
Q

What do the Non-class NK battery breakers do?

A

•Connect and disconnect battery to the MCC

35
Q

Who operates the breakers for ‘E’ and ‘F’ batteries?

A

•The Control room normally
•Can be operated locally

36
Q

Who normally operates the breaker for the ‘G’ battery?

A

•Only operated locally

Systems (8 decks)

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