201.41 ESF Load Sequencers Flashcards
- 201.41 ESF Load Sequencers*
- *
Function of ESF Sequencer
Sequentially start ESF loads during emergency conditions
Prevent overloading of the emergency bus and associated Standby Diesel Generator (high starting currents)
- 201.41 ESF Load Sequencers*
- *
Location and power supplies of Sequencers
EAB 10’, separate rooms south of elevator
Respective Class 1E 125 VDC Switchboard:
E1A11 - A train
E1B11 - B train
E1C11 - C train
- 201.41 ESF Load Sequencers*
- *
What are the diferent sequencer modes?
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)
- 201.41 ESF Load Sequencers*
- *
Mode I initiation by:
Initiated by the simultaneous receipt of any four or more of six Safety Injection signals generated by the Engineered Safety Features Actuation System.
- 201.41 ESF Load Sequencers*
- *
Mode II initiation by:
Initiated by the simultaneous receipt of any two out of four 4.16kV ESF Bus:
Undervoltage
Sustained degraded voltage
Degraded voltage with Safety Injection
- 201.41 ESF Load Sequencers*
- *
Mode III initiation
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
- 201.41 ESF Load Sequencers*
- *
Controls for ESF Sequencer in Control Room
Mode II Manual Actuation
(simulates all 4 bus UV signals)
Sequencer Reset
(resets sequencer if all conditions satisfied)
(CP-003)
- 201.41 ESF Load Sequencers*
- *
Function of Load Sequencer Key Switches
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
- 201.41 ESF Load Sequencers*
- *
Actions (or conditions) required to reset sequencer
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
- 201.41 ESF Load Sequencers*
- *
If DG is operating in parallel, what will a SI signal result in?
Trip the DG output breaker w/in 1 sec, resulting in Mode I actuation not a Mode III
- 201.41 ESF Load Sequencers*
- *
After a LOOP, the DG output breaker will not close until:
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)
Equipment that starts on Mode I actuation
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
- 201.41 ESF Load Sequencers*
- *
Equipment that starts on Mode II actuation
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
- 201.41 ESF Load Sequencers*
- *
Equipment that starts on a Mode III actuation
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
