.AR Elect. SBOGs (Welch's Highlighted Notes)

Question 1

Purpose/Function/Limitations:

• SBOGS are backup for what station event?.
• SBO assumed on how many units?
• Required by which CFR?
• FSAR – how many hours coping time?
  
  • How long/time assumed to start SBOGs?.
• When is the second SBOG used?…
• LOOP: energize which NAN bus within howmuch time? why?
• SBOGs operation coordinated through which Unit?
• SBOGs cannot supply which two Units simultaneously?
• If a unit’s NBN-X03 XFMR is faulted, can SBOG still supply that unit?
• LOOP: SBOG used to energize the SWYD loads within how many hours hours
  
  • Maintains what?
• • SBOGs (2)
• fuel type?
• MW? Design bases?
• Max loading based on whatSBOG temp < °F?
• RMP? Type of gears used?
• RPM? (generator speed)

Answer 1

Purpose/Function/Limitations:

• Backup source of power during station blackout.
• SBO only assumed on one unit. (LOOP and both DGs fail – loss of all AC)
• Required by 10CFR50.63 (cope with SBO, core cooling and CTMT integrity)
• FSAR – 16 hour SBO coping time.
  
  • Assumes one SBOG is started within 1 hour.
• Second SBOG is used if the first one fails or if MDAFW pump is required.
• LOOP: energize NAN-S07 within 1 hour to maintain the SBOG batteries.
  
  • Maintains SBOG availability for a SBO
• SBOGs operation coordinated through Unit 1
• SBOGs cannot supply U2/U3 simultaneously
• If a unit’s NBN-_X03 XFMR is faulted, SBOG cannot supply that unit_.
• LOOP: SBOG used to energize the SWYD loads within 2 hours
  
  • Maintains PCB control power and PCB availability

SBOGs (2)

• Liquid fueled gas turbines
• 4.27 MW (Design Basis is 3698 KW)
• Max loading based on maintaining SBOG temp < 1330°F
• 14,951 rpm turbine speed. Reduction gears used.
• 1800 rpm generator speed

Question 2

Gas turbine operations:

• what are the 3 main sub-components of SBOGs?
• what are the 3 main sub-components of SBOGs?
• Compressor blades…
• Air is forced into…
• Where is the Air/Fuel mixture ignited?…
• Turbine gases rapidly…
• … blades spin.

Answer 2

Gas turbine operations:

• Compressor
• Combustor
• Turbine
• Compressor has blades that turn like a fan to pull air into the gas turbine.
• Air is forced into the combustor, where fuel mixes with the compressed air.
• Air/fuel mixture is ignited in the combuster
• Burning gases rapidly expand out of combustor into the turbine. Gases transfer energy to the turbine blades.
• Causes the blades to spin.

Question 3

Acceleration (…Startup Sequence…)

• At what % speed is the energy of the hot gases from the combustor enough to maintain turbine speed. “Self-Sustaining Speed.”?
• ?°F = what at the turbine 3rd stage?
• At what % speed do the Bleed Air Valve close, and the Variable Vane Controller actuates open?

Answer 3

Acceleration (…Startup Sequence…)

• 66% speed - energy of the hot gases from the combustor is enough to maintain turbine speed. “Self-Sustaining Speed.” Turbine starting system disengages. Pre/Post Lube Oil Pump stops. Atomizing air is now supplied from the compressor.
• 400°F (turbine 3rd stage) - ignition system switches off.
• 90% speed - Bleed Air Valve closes, Variable Vane Controller actuates open.

Question 4

{[…Not highlighted in Welch’s Notes…]}

Engine support systems

• Explain…

Lube Oil System

• Explain…

Answer 4

{[…Not highlighted in Welch’s Notes…]}

Engine support systems

• 480Vac power normally fed from NHN-M56 (NAN-S06).
• If power lost, power is fed from a step down XMFR from the SBOG 13.8 kV bus and an automatic transfer switch.

Lube Oil System

• Two lube oil cooler packages. Cooled by electric fans.
• 24 Vdc pre/post lube pumps
• Engine driven MLO pump
• PCVs/TCVs/Oil reservoir
• Turbine Shutdowns: (Low oil level or pressure)

Question 5

{[…Not highlighted in Welch’s Notes…]}

Battery Charger and Battery Rack Assembly (2 per generator & 1 for switchgear)

• Explain…

Engine Air System

• Explain…

Answer 5

{[…Not highlighted in Welch’s Notes…]}

Battery Charger and Battery Rack Assembly (2 per generator & 1 for switchgear)

• 24 Vdc for control voltage (Generator #1 NEN-H01A)
• 24 Vdc for diesel start (Generator #1 NEN-H02A)
• 125 Vdc for switchgear control power (NKN H22)

Engine Air System

• Pressurize oil seals.
• Cool turbine rotor disks and first stage nozzles.
• Supply Control Air for operation of the fuel control system.
• Assist in obtaining smooth engine operation by preventing surge conditions at critical speeds.

Question 6

{[…Not highlighted in Welch’s Notes…]}

Start System

• Explain…

Answer 6

{[…Not highlighted in Welch’s Notes…]}

Start System

• Capable of a black start.
• Battery DC power source is independent from the unit’s PK and NK power.
• Diesel-hydraulic start system provide the rotational force start the SBOG up to 66% speed.
• At 66% speed, the turbine engine provides its own power to accelerate to 100% speed.
• Diesel engine supplies compressed air and hydraulic pressure to the turbine.

Question 7

{[…Not highlighted in Welch’s Notes…]}

Fuel system

• Explain…

Combined Generator Control Module

• Explain…

Answer 7

{[…Not highlighted in Welch’s Notes…]}

Fuel system

• Controls the fuel pressure and regulates the fuel flow according to operating requirements
• Use fuel pumps (1 is shaft driven)

Combined Generator Control Module

• Controls Speed/load and Voltage/KVAR

Vibration Monitoring System

Question 8

{[…Not highlighted in Welch’s Notes…]}

Turbotronic Control System (Controls the turbine functions, 24 Vdc power)

• Explain…

Answer 8

{[…Not highlighted in Welch’s Notes…]}

Turbotronic Control System (Controls the turbine functions, 24 Vdc power)

• Sequences operating systems during starting, running, and shutdown, to provide necessary protection during all phases of operations; and to monitor package system parameters during operation
• Power factor (pf) must be manually maintained (raise load, raise voltage / lower load, lower voltage)

Question 9

{[…Not highlighted in Welch’s Notes…]}

Fire Detection and Suppression System

• Explain…

Answer 9

{[…Not highlighted in Welch’s Notes…]}

Fire Detection and Suppression System

• Uses light sensors or “Fire Eyes” to detect the presence of fire.
• Lock out before the SBOG enclosure doors are opened to prevent inadvertent CO2 discharge.
• Fire System Control is located on each SBOG control panel and consists of a Lockout switch.
• FP system lockout prevents actuation of the CO2.
• The fire eyes have protective covers that can be installed if the engine needs to run with the doors opened (one door at a time for vibe data and for < 10 minutes), but the thermal and hazardous gas level detectors will still force a shutdown if they are tripped by temperature or Lower Explosive Limit that exceeds the threshold. 10 min limit for open doors prevents high summer temp from causing SBOG shutdown.
• Alarm: FP system not in Auto or fire eyes are covered.

Question 10

{[…Not highlighted in Welch’s Notes…Except Acceleration 66% & Self-Sustaining Speed]}

Start-up sequence

Time sensitive step (< 2 min):

• Explain…

Press “Start” button.

• Explain…

Diesel Starting Engine Start

• Explain…

Ignition

• Explain…

Acceleration

• Explain… (highlighted in Welch’s notes!!!)

Generation

• Explain…

Answer 10

{[…Not highlighted in Welch’s Notes…Except Acceleration 66% & Self-Sustaining Speed]}

Start-up sequence

Time sensitive step (< 2 min):

• Once the SBOG reaches “Ready to Load” a 2 minute timer starts on 24VDC battery charger failed alarm.
• If charger failed alarm not clear within 2 minutes, the SBOG will automatically shut down.
• AO has to energize NHN-M73 upon receiving the “Ready to Load” light. Has to close SBOG output breaker (energizing NAN-S07) and ensure ABT transfers.
• Also applies during testing. Will need to re-close the battery charger supply breakers within 2 minutes vice the SBOG output breaker.

Press “Start” button.

• Starts the Pre/Post Lube Oil Pump (runs for 30 seconds)
• Enclosure purge fan will run for two minutes if not in a SBO.

Diesel Starting Engine Start

• After 2 minute enclosure purge or 30 seconds pre-lube, the diesel starts.
• Diesel will pressurize the air assist tank to 120 psig.
• Diesel-driven hydraulic pump provides pressure to engine starting motor. Compressor and turbine begin to rotate.

Ignition

• Starting circuit opens Fuel Purge Valve (drains old fuel)
• Fuel Boost Pump starts
• 15% speed - Fuel Purge Valve closes.
• 21% speed - Fuel Control Valve sends fuel to the Igniter Torch and Fuel Injector Nozzles.
• Atomizing air mixed into the Fuel Injector Nozzles and the Ignition Circuit is energized. Lights the Igniter Torch.
• Open Bleed Air Valve enables compressed air to bypass the turbine to make starting easier and prevent turbine surge.
• Variable Vanes in the compressor are at minimum position to prevent compressor stall during the turbine acceleration.
• As the temperature of the air leaving the combustor begins to rise the turbine begins to take over the load of turning the shaft.

Acceleration

• 66% speed - energy of the hot gases from the combustor is enough to maintain turbine speed. “Self-Sustaining Speed.” Turbine starting system disengages. Pre/Post Lube Oil Pump stops. Atomizing air is now supplied from the compressor.
• 400°F (turbine 3rd stage) - ignition system switches off.
• 90% speed - Bleed Air Valve closes, Variable Vane Controller actuates open.

Generation

• 85% speed - voltage regulator flashes the generator field.
• 90% speed - Generator Voltage and Start Time are verified and the “Ready to Load” timer is activated.
• 10 seconds after the Turbine speed reaches 90% the “Ready to Load” lite comes on.
• 100% speed the Governor Control system assumes control of the turbine.
• Total time elapsed is ~ 1 min 35 seconds.

Question 11

{[…Not highlighted in Welch’s Notes…]}

SBOG Shutdown Sequence:

• Explain…

Answer 11

{[…Not highlighted in Welch’s Notes…]}

SBOG Shutdown Sequence:

• < 300kW before shutting down the SBOG
• Reduce SBOG load (communicate with MCR)
• Open SBOG Output Breaker on NAN-S07
• Press “Stop” push button.
• Goes into a 3 minute cool down mode indicated by the “cool down” light on the SBOG Control Panel. During this time the turbine is running at 100% speed with no load.
• At the end of the cool down period the SBOG will begin to slow down. When it reaches 90% speed the SBOG “Running” light goes out.
• In an “Emergency,” SBOG can be stopped using the “Fast Stop” push button:
  
  • Immediately closes the Fuel Cutoff valve and the trips open the SBOG Output Breaker.
  • Cool down period is also eliminated and the SBOG slows to a stop.