GT/NE- Station Black Out Generators (SBOG) Flashcards
(NE is the electrical side of the SBOGs)
What is the system designator for the SBOG’s?
GT/NE
What does the NRC mandate in 10CFR50.63?
That each station must provide an alternate source of AC power to ensure that the reactor core is not exposed during a station blackout if one or more of the emergency diesel generators or battery back up systems fail.
Is off site power dependable? Preferred?
Dependable, no. Preferred, yes.
What is the NUMARC 87-00?
It’s a Coping Assessment, which is a study of how a plant will ‘Cope with’ situations such as fire or tornado.
What is a black out vs a station black out?
A black out is When a single unit loses off-site power and both diesel generators fail, a station black out is when all three units lose off-site power and both diesels fail.
How long do you have to start and load the SBOG’s in an emergency?
1 hour
What is the only means of power during a black out until the SBOG’s are brought online?
Class and non-class battery systems.
What is the back up for the SBOG’s and does the NRC let us take credit for it?
Cross tying the 4160v busses between units through the switchyard. We cannot take credit for this.
What is used to reduce the turbine speed to the effective generator speed of 1800 rpms?
A reduction gear assembly.
What are the three main components of a gas turbine?
Compressor, combustor and turbine
How many fuel injectors are in the SBOG combustion chamber?
12
What two services does the compressed air of the gas turbine serve?
20% combustion air
80% cooling air for turbine blades
What physically spins the turbine of the gas turbine?
Hot exhaust gases from the combustion process
Efficiency of a typical gas turbine?
20%
At what temp are the exhaust gases when they exit the silencer stack?
1000F
What temps are the gas turbines usually exposed to?
1600-2300F
What are the four processes that comprise the Briton cycle(gas turbine cycle)?
Compression, combustion, expansion, exhaust
What components draws the air into the compressor section through the air inlet?
Compressor rotor
When does the bleed valve open and why?
At start up to vent some of the compressed air around the turbine blades
The variable guide vanes regulate air flow during start to avoid surge limits. When do they begin to open and when will they be full open?
Begin opening from minimum position at 90% engine speed and reach full open one or two seconds later
What is the purpose of the combustion process?
To increase the velocity of gases being directed to the turbine section by causing them to expand more rapidly
During the combustion process, do I expect a change in pressure?
No
How long will the SBOG’s supply AC power to the emergency loads of a blacked out unit?
16 hours
What are the three major components of the Taurus turbine-driven generator package?
Turbine engine, reduction gear assembly, generator
What is the output speed of the Taurus turbine engine?
14951 rpm
What is the reduction gear ratio?
8.3/1
How is the SBOG lube oil system cooled?
An electric fan on the bottom of the cooler package
Concerning the sbog lube oil system, what components maintain proper oil temp?
Oil reservoir, oil coolers, thermostatic oil control valves
What is the sbog lube oil piping made of?
Stainless steel
What services are provided by the sbog air system?
Pressurize oil seals, cool turbine rotor discs and first stage nozzles, supply air for proper fuel air mixture in combustion chamber, prevents surge conditions at critical speeds
What is the purpose of the turbotronic control system
Provides for automatic starting, acceleration to operating speed, engine and generator monitoring during operation, and normal and emergency shutdown sequencing, control, protection and display
How is automatic speed control accomplished?
By the combination generator control module which maintains generator frequency by controlling fuel flow to the turbine
The air intake system for each Sbog unit consists of what components?
Air filtration/cleaner unit, silencer, ductwork
How many pre-filter’s and high-efficiency filters are there in the air inlet and exhaust system?
20 prefilters and 20 high efficiency filters
Concerning the start system, what are the two functions of the diesel engine?
Supplies rotational power to drive a hydraulic pump which provides the pressure to drive a hydraulic motor which provides rotational force to start the turbine
Supplies a source of atomizing air from an External compressor attached to the diesel engine to the air assist accumulator of the turbine engine. Used to pressurize the air assist tank to 120 PSIG for Sbog start
Start command has been initiated. What are the nine steps that occur for the Sbog start up?
30 second pre-lube 24 V DC pump cycle begins,
diesel engine starts and accelerates to operating speed’s within seconds,
engine driven pre-charge pump begins operation,
loading solenoid valve is energized and pressure positions pump to maximum stroke,
hydraulic motor rotates, sprag clutch engages outer race, And gas turbine engine begins to rotate,
combustion occurs, speed increases and turbine engine begins to drive gear train,
when gear train speed exceeds start motor speed, Spraggs disengage, permitting clutch to free wheel,
turbine reaches 66% NGP, loading solenoid deenergizes, and hydraulic pump goes to minimum stroke,
as turbine accelerates to 100% speed, diesel engine continues to run in no-load condition for five minutes, then shuts down
What are used as the engine seals?
Labyrinth seals
Where does the turbine cooling air come from?
Bleeds from the compressor 11th stage of compressor section
What type of valve is the compressor bleed air valve?
Motor-driven roller screw actuated butterfly (trunion) valve
During the start cycle, the PLC commands an actuator to open the bleed air valve. When will it shut?
Approximately 90% speed
During deceleration, when will the bleed valve open?
90% engine speed
What lets the PLC know how much air is available for combustion?
PCD (pressure compressor discharge)
What is the operation sequence of the air system?
Engine begins cranking
Compressor begins building pressure
Cooling air is supplied to the turbine
Combustion occurs
PLC controls acceleration fuel schedule (1% every 2 seconds, while not exceeding programmed 3rd stage rotor inlet temp increase(T5))
Air/oil seals are pressurized
Bleed air valve closes and variable guide vanes open at 90% speed
Engine is at 100%
What is the function of the lube oil system?
Provides lubrication and cooling of engine rotating elements and provides operating medium for hydraulic-actuation of the bleed air valve, variable guide vanes and fuel valve actuator
When does the thermal bypass valve bypass the oil coolers?
When oil cooler DP >50 psig
What pressures are associated with the oil pressure transducer?
Alarm @ 42 psig
Shutdown @ 25 psig
Start permissive @ 6 psig
What is the purpose of the pre/post lube oil pump?
Supplies oil to the engine and gearbox for 30 seconds prior to engine rotation, during “crank” mode, and for 55 minutes post lube cooling cycle after engine shutdown
What temp set points are associated with the lube oil heater temp detector?
Alarms @160F
Shutdown @ 165F
What are level alarm set points associated with the lube oil tank?
Low level alarm @ 279 gal
Low level shutdown @ 182 gal
Briefly describe the sbog fire protection system
Light sensors called “fire eyes” which sense a fire by sensing wavelength within the sbog enclosure and dump the CO2 injection to stop fires. Must be disabled prior to opening enclosure doors.
Who needs to be informed prior to inhibiting fire system?
Unit 1 control room and fire protection dept
What are the basic steps in the start up sequence of the sbogs?
Press start button
Diesel starting engine starts
Ignition
Acceleration
Generation
At what speed does the fuel purge valve close?
15% speed
What is the fuel purge for?
To burn off any remaining fuel in the system prior to start up
When do the sbogs reach self-sustaining speed and why?
66% speed because the energy produced by the hot gases from the combustor is enough to maintain turbine speed
At what speed does the voltage regulator flash a generation field?
80% speed
When will the Ready to Load light come on?
10 seconds after turbine speed reaches 90%
When does the combination generator control module assume control of the turbine?
90% speed
Approximately how long is the start up sequence?
1 min 35 seconds
While the sbog is operating, what would happen if ‘fast stop’ is used?
This immediately closes the fuel cutoff valve and trips the generator output breaker
3 minute cool down period will be eliminated
How many stages are on the compressor rotor?
12 stages
How many stages on the compressor rotor have variable guide vanes?
1 on the compressor inlet and First 3 stages of the rotor
What components are in the front of the Taurus turbine engine?
Air inlet assembly, generator
Where is 480VAC power to auxiliary equipment powered from?
AE-NHN-M56
Do the SBOG’s have a stand alone DC battery system for emergency start up?
Yes
What type of fuel is used in the gas turbines?
No. 2 fuel oil
When does the SBOG ignition system switch off?
when T5 temperature reaches 400*F
