201.41 ESF Load Sequencers Flashcards

1
Q
  • 201.41 ESF Load Sequencers*
    • *

Function of ESF Sequencer

A

Sequentially start ESF loads during emergency conditions

Prevent overloading of the emergency bus and associated Standby Diesel Generator (high starting currents)

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2
Q
  • 201.41 ESF Load Sequencers*
    • *

Location and power supplies of Sequencers

A

EAB 10’, separate rooms south of elevator

Respective Class 1E 125 VDC Switchboard:

E1A11 - A train

E1B11 - B train

E1C11 - C train

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3
Q
  • 201.41 ESF Load Sequencers*
    • *

What are the diferent sequencer modes?

A

Mode I - Safety Injection Signal

Mode II - Loss of Off-Site Power (LOOP)

(Undervoltage on the associated ESF Bus)

Mode III - Safety Injection with LOOP

(Mode I plus Mode II)

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4
Q
  • 201.41 ESF Load Sequencers*
    • *

Mode I initiation by:

A

Initiated by the simultaneous receipt of any four or more of six Safety Injection signals generated by the Engineered Safety Features Actuation System.

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5
Q
  • 201.41 ESF Load Sequencers*
    • *

Mode II initiation by:

A

Initiated by the simultaneous receipt of any two out of four 4.16kV ESF Bus:

Undervoltage

Sustained degraded voltage

Degraded voltage with Safety Injection

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6
Q
  • 201.41 ESF Load Sequencers*
    • *

Mode III initiation

A

Initiated by the existence of both Mode I and Mode II conditions.

Both simultaneously,

Either Mode I or II followed by the other

Mode I with the DG output breaker closed for > 1 sec.

If the DG is running in parallel with off-site power the SI signal will trip the DG output breaker, unless the DG is in local control

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7
Q
  • 201.41 ESF Load Sequencers*
    • *

Controls for ESF Sequencer in Control Room

A

Mode II Manual Actuation

(simulates all 4 bus UV signals)

Sequencer Reset

(resets sequencer if all conditions satisfied)

(CP-003)

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8
Q
  • 201.41 ESF Load Sequencers*
    • *

Function of Load Sequencer Key Switches

A

Mode I Logic key switch allows operator to reset Mode I Logic Present signal.

(if not reset, a subsequent Mode II signal would cause Mode III)

D/G Emergency Trip and D/G Breaker Closure key switches

allow simulation of those conditions

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9
Q
  • 201.41 ESF Load Sequencers*
    • *

Actions (or conditions) required to reset sequencer

A

Reset all SI signals

Reset all UV signals

Verify automatic loading sequence completed or aborted

Depress sequencer reset button

Must use Mode I Logic Reset keyswitch to clear Mode I logic

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10
Q
  • 201.41 ESF Load Sequencers*
    • *

If DG is operating in parallel, what will a SI signal result in?

A

Trip the DG output breaker w/in 1 sec, resulting in Mode I actuation not a Mode III

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11
Q
  • 201.41 ESF Load Sequencers*
    • *

After a LOOP, the DG output breaker will not close until:

A

Proper voltage / frequency

6 sec time delay from LOOP signal removed

Breakers open for equipment that recieves a bus strip signal

(fails to open, or open signal to seq fails, sequencer locks up)

(DG breaker closed is Mode I and II permissive)

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12
Q

Equipment that starts on Mode I actuation

A

HHSI - 6 sec

LHSI - 10 sec

CS - 15 sec (if RCB > 9.5 psig) momentary 2 sec signal

RCFCs - 15 sec

CCW - 20 sec

ECW - 25 sec

AFW - 30 sec

CR Emerg. HVAC / Makeup - 35 sec

Ess Chilled Water - 35 sec

STDBY Ess Chiller - 35 sec

CS - 40 sec (if RCB > 9.5 psig / not yet running) latched

Ess Chiller - 240 sec

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13
Q
  • 201.41 ESF Load Sequencers*
    • *

Equipment that starts on Mode II actuation

A

480 VAC Buses - 1 sec

RCFCs - 15 sec

CCW - 20 sec

ECW - 25 sec

AFW - 30 sec

CR Emer HVAC - 35 sec

Ess Chilled Water - 35 sec

STDBY Ess Chiller - 35 sec

Ess Chiller - 240 sec

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14
Q
  • 201.41 ESF Load Sequencers*
    • *

Equipment that starts on a Mode III actuation

A

480 VAC buses - 1 sec

HHSI - 6 sec

LHSI - 10 sec

CS - 15 sec (if RCB > 9.5 psig) momentary 2 sec signal

RCFCs - 15 sec

CCW - 20 sec

ECW - 25 sec

AFW - 30 sec

CR Emerg. HVAC / Makeup - 35 sec

Ess Chilled Water - 35 sec

STDBY Ess Chiller - 35 sec

CS - 40 sec (if RCB > 9.5 psig / not yet running) latched

Ess Chiller - 240 sec

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