Emergency Diesel Generator Flashcards
Purpose of EDG system, including how fast to supply power and what speed
Designed to startup automatically and accelerate to 600 RPM in 10 seconds. Provides a highly reliable, self contained power source for :
1. ESF loads required for safe shutdown
2. Loads required to minimize effects of DBA
3. Backup on complete LOOP
Design basis, including how long required to be available? 4 items
Sufficient number of EDGs to ensure adequate electrical supply to operate ESF loads coincident with:
1. LOOP
2. Failure of one EDG
3. DB LOCA which imposes the highest electrical demand for a unit
4. Forced shutdown of the other unit
Each DG is housed in a Class I structure with forced oil transfer and storage capability for 7 days following DBA
Starting sequence (what happens at each RPM)
0RPM
-Air start solenoids open to accelerate engine
-Pneumatic protection system is pressurized
-Room fan starts
40 RPM
-Incomplete sequence timer relay is energized
-DG trips if it doesnt reach 280 RPM in 25 seconds
250 RPM (Fast start only)
-125VDC field flash energizes
280 RPM
-Both fuel transfer oil transfer pumps start
- Air valves close; lockout/reset air is isolated
-Crank failure circuit is disabled (incomplete sequence)
- Prelube oil pump and heater are de-energized
The following trip alarms are enabled immediately:
-bearing high temp, thrust bearing wear, jw high temp, crankcase high press, 20 seconds after 280RPM: Engine LO low press and turbo LO low press
- JW pump is turned off
-SX169 valve opens
450RPM (Slow start only)
- Run for 3 minutes then accelerates to 600 rpm and 125 VDC field flash energizes
570RPM
-Ready to load signal is actuated
-125VDC field flash is de-energized
Stopping sequence (what happens at each RPM)
600 RPM
-CS taken to TRIP
-Room fan stops <70F
-VR de-energizes
-Elec gov de-energizes, speed increases to 608RPM
-Test mode remote trip solenoid de energizes and one fuel control solenoid energizes. 2.5 minutes later emergency fuel control solenoids swap. If speed drops <570 rpm during 5 minute C/D, incomplete sequence alarm.
<280RPM
-SX169 Closes
-Pre lube and jacket pump start
-Fuel oil transfer pumps stop
-several trips disabled
DG trips when SI present K611 relay
Engine overspeed 660 rpm stops engine
Generator differential current (trips Breaker) stops engine
Emergency stop pushbutton stops engine
DG trips when UV present
Engine overspeed (all three engine and breaker trip)
Gen diff current
Emergency stop PB
DG overcurrent (B)
DG neut overcurrent (B)
Reverse power (B)
Loss of field (B)
Underfrequency (B)
1412 lockout (B)
Other DG trips
Low lube oil pressure
low turbo oil pressure
turbo thrust bearing fail
high crankcase pressure
main bearing high temp
jacket water high temp
connecting rod bearing temp
generator bearing high temp
incomplete starting sequence
Manual test mode does what to trip functions?
Enables all bypassed trip on emergency start.
Unit available for emergency light
-Adequate control air pressure and turning gear not engaged
-Loss of DC, stop switches, emerg stop PB, diff relay actuation not actuated
-local VR control not in manual
What is purpose of the DG fuel oil head tank?
Fuel as diesel comes up to speed before replenished by fuel pump.
How long can a DG run after a LOOP with only the fuel in its fuel oil storage system?
7 days
During standby, the air dryer will start at a receiver pressure of _____. _____ seconds later the compressor will start. This is also what happens on a ______start of the engine.
During a(n) ______ the dryer and the compressor both start at _____.
With CS in Auto, stops at _____. With in hand_______.
240#
180
normal
emergency start
240#
250#
runs continuously
The way that specified trips are bypassed during emergency start is by ….
….energizing the emergency fuel control solenoids. These block air supply to the trip side of the fuel control cylinder.
Loss of DC power to Diesel…
A loss of DC will always trip the diesel regardless of operating mode and prevent the diesel from starting.
Loss of Air
A loss of pneumatic protection air will prevent all trips to the DG except overspeed.
Purpose of the fuel cylinder control valve
Ports air/locks out air to the ON side of the fuel control cylinder.
Fuel control cylinder is tripped by overspeed by which component?
Overspeed fuel shutoff valve. Must be locally manually reset when activated.
Emer fuel control solenoids:
Closed in emerg mode, thus not allowing right side of fuel cylinder to be pressurized for test mode trips. Opens on Gen Diff or Emer P/B.
On an engine S/D valves cycle back and forth until both open 2.5 minutes.
Pneumatic fuel control valves…
normally closed, supply air to trip side of cylinder
Fuel control cylinder
Shuts off fuel delivery by the injection pumps.
Safety air pilot
keeps the trip header pressurized after starting air header was depressurized.
DG cranking motive force
0-140 rpm All air
140-280 rpm Air w/ fuel
>280 all fuel
Methods for manually tripping the DG
- Manual PB (if in local)
- Emerg stop PB (No cooldown cycle)
- Close combustion air intake valve
- Close diesel oil day tank isolation valve
- Pull fuel rack manual trip lever on side of EDG (also fuel rack trip at governor- same linkage)
Emer fuel control solenoids are…
energized closed, deEnergized to allow trip
To manually close the DG output breaker…
DG up to speed and voltage
1412, 1413, 1414 no lockout
sync switch
MCB C/S to close
Bus energized
1414 overcurrent does not trip 1413 because…..
because fault may be from the other units bus.
DG output breaker auto close
- UV condition on bus
- DG rated speed and voltage
- 1412, 1413, 1414 open with no ‘86’ lockout relays
- Breaker CS in A/T or auto reclose circuit arm selector switch in SURV TEST with brkr C/S in any position other than Pull out.
- 1411 open (ESF non ESF cross tie)
Sequencing order
0 seconds: CV pumps
VC WO pumps (U1 only)
5 seconds: SI pumps (SI)
10 seconds: RHR pumps (SI)
15 seconds: VC chiller (U1 only)
CS pumps (CS only)
20 seconds: CC pumps
25 seconds: SX pumps
35 seconds: AFW pump (A train only)
40 seconds backup CS pump
On an SI signal with off site power available (SARA contact)
DG will auto start, but output breaker stays open.
Safeguards actuation relay will autostart all safety related loads. No loading sequence will be used since the sequence is only used to prevent overloading the DGs by the starting currents of the various loads.
On a SI signal coincident with a LOOP
The UV relays for the bus will open the SAT feeder breakers, shed all loads from the bus except 480V, and start DGs. ESF sequences on.
On a UV condition with no SI signal (SDRA contact)
- UV relay autostarts DGs and sheds all loads except 480V
- Once DG is up to speed and V, the output breaker closes
- The safeguards shutdown relays start the loads needed for safe shutdown(all ESF equipment except RH and SI)
The safe shutdown sequencer relay will energize if…..
…….1. SAT feeder breaker open
2. Unit crosstie feeder breaker open
3. DG output breaker closed and voltage on the bus
4. No SI signal present
SARA=
SDRA=
SARA=No loading sequence
SDRA=Loading sequence
Bus must have its own SAT feeder breaker closed, or other units SAT(plus x ties closed) to pickup the SARA relay, what about if fed from other units DG?
If fed from other units DG, no SARA
DG started on UV to the bus. DG is feeding bus and SAT and reserve feeds open. Selecting MAN TEST will…..
…allow operators to parallel for the monthly surveillance yet having all DG protection available.
Three ways isochronous mode enabled
- SAT and RES feed breaker open
- Local DG control and Local CS in Isochronous
- 4EX3 energized (Emerg start, switch in auto/man test/man emerg)
4EX1 =
4EX2=
4EX3=
3IM+
4EX1=seals in the emerg start
4EX2= Blocks test mode trips
4EX3=Disables speed and voltage control, EDG in isochronous
3IM=Diesel in isochronous mode
Never return the DG emerg mode speed-voltage control to ____ from ______ until the DG is no longer operating parallel to anything.
AUTO;MAN EMERGENCY
The DG _A/B emer speed/volt control selector switch for DGs has 3 function
- In Auto mode with manual start, all trip control functions enabled. With emerg start all trip and control functions disabled except overspeed, diff current, and man Emerg PB.
- The “manual emergency mode” position permits speed and voltage control to be enabled after an emergency start, used for paralleling back to offsite power. only 3 emerg trips enabled.
- “MAN TEST MODE” position is a momentary contact with spring return to AUTO. All 16 trips are enabled along with normal speed and voltage control.
If not in AUTO, DG will still start in manual or emergency start mode. speed and voltage determined by the selector position and starting mode.
Air intake Butterfly valve will close on
660 rpm overspeed trip, locally reset
DG ratings
5500 KW at 954 amps continuous
107.9% 2000 hours max
110% 2 hours in a 24 hour period
Minimum 3000 KW to min carbon buildup
What supplies the Exciter field?
Powered from 125VDC during startup, gen output when running
At 570 RPM, the _____ swaps from _____ to self excitation.
field flash;125VDC
Fault isolation switches will____an EDG, but if an _____ condition exists, the diesel will restart.
Stop;UV
Loss of PTs
- If SAT supplying, and DG PTs lost cant sync onto bus.
- IfSAT supplying and bus PTs lost, output breaker can close in on UV but the sequencer wont work and cant close from MCR or locally unless control power turned off.
- IF DG supplying and DG PTs lost
a. If in man test or UV start mode, DG bkr trips open on loss of field.
b. May be able to go to DG panel switches and manually control speed and voltage.
Main governor is two in one. When electrical section lost…
….speed increases from 600 to 608 rpm where hydraulic takes over.
Overspeed causes….
- Overspeed governor moves fuel racks off and trips butterfly intake valve. 660 rpm.
With a loss of air, the fuel control cylinder fails…
on. Need air to trip the diesel.
Storage capacity for each unit Fuel oil storage tanks, TS credited sources
4-25000 gallon tanks U1
2-50000 gallon tanks U2
Purpose of fuel oil day tank
- NPSH for fuel oil fuel pumps
- Fuel oil for engine startup
- 500 gallon tank
Rapid start of DG ensured by:
- Circulating lube oil is kept warm
- Circulating jacket water is kept warm
- Small reservoir of fuel oil on the engine
Jacket water cools_______. Jacket water is cooled by _____.
Lube oil, fuel oil, governor oil and cools or heats combustion air; SX, supplied by a 120VAC fail open AOV
Main JCW pump is _____ driven. Main oil pump is _____ driven.
chain; shaft
LCO 3.8.1
Two EDGs operable
>= 450 gallons of fuel oil in day tank
LCO 3.8.3, time frame specified fuel oil storage
Verify each DG fuel oil storage tank(s)
contains >= 44,000 gal of fuel.
41138-44000, 48 hours
<41138 Diesel inop
Separate fuel tanks, separate fuel pumps,piping
Stored diesel fuel oil is required to have sufficient supply
for 7 days of post accident load operation.
Precaution to prevent scoring of cylinders?
While engine is running, especially unloaded, jacket water outlet temperature should be maintained 0-10F hotter than lube oil outlet temperature. This prevents cylinder scoring.
Jacket water heater cycles….
……120-130F while JW pump is running
Precaution for high diesel room temperature….
Do not start or continue to operate a diesel when diesel room temperature exceeds 132F
Electric governor controls at _____. IF fails, hydraulic will
pickup at _____. Overspeed trip will occur at _____.
600RPM
608RPM
660RPM
What provides the motive force to run all auxiliary equipment once the diesel is running?
Crankshaft
Clogged lube oil strainer will…..
Trip the EDG because lube oil will not be delivered to the engine
Components in order as air travels from room to combustion
Intake filter, butterfly valve, turbocharger, heater, intercooler, engine, turbo, exhaust silencer
Turning gear engaged prevents diesel from auto starting by…
blocking air to the air start valves
If SI occurs while SD sequencer in progress, what happens?
TSRA TDC allows timers to reset if SI occurs during UV sequencers. (0.15 seconds)
TRM 3.7.d area temp monitoring
3.7 PLANT SYSTEMS
3.7.d Area Temperature Monitoring
TLCO 3.7.d The temperature limit of each area in Table T3.7.d-1 shall
not be exceeded for > 8 hours, or by > 30° F.
APPLICABILITY: Whenever the equipment in the affected area is required to
be OPERABLE.
132F for DG rooms and diesel storage tank rooms
Caution for potential rocker arm failure:
If any cylinder exhaust temp drops by 160F or more over a 20 minute time period compared to the other cylinder exhaust temps, then a rocker arm failure should be suspected.
Min Freq and V on diesel surv
98% frequency 58.8 hz
95% V 3950
Indication from control room that the diesel local control switch is in ‘local’
White light indication only on DG start/stop switch
