2nd CRO Board Questions Flashcards
Where all does the EHC supply oil to?
- The trip manifold assembly in the front standard
- The turbine main stop and control valve actuators
- The CRV valves
- A small portion also goes to the transfer and acid control filtering unit system
When do we open and close Turbine drains?
Closed when prewarming
Opened before rolling the turbine
Closed again after startup
“A” class- close at tie on
“B” class- close at 15% (120MW)
“C” class- close at 30% (240MW)
Why do we have turbine drains and where are they located?
Where do they go?
Turbine drains remove condensate from various stages of turbine
“A” comes from HP turbine and goes to blowoff tank due to high pressures
“B” comes from IP turbine and goes to condenser
“C” comes from LP turbine and goes to condenser
What is the purpose of the Nozzle boxes?
Nozzle boxes minimize thermal and pressure stresses in the turbine shells in the area of the first stage.
Describe the flowpath through the nozzle boxes.
Steam leaving the nozzle boxes is directed through 7 stages of HP turbine blading, with the steam flowing toward the turbine front standard.
2 Sets of nozzle openings in the nozzle boxes balance out the steam reaction forces which reduces the stresses on the nozzle box locating keys
Name the Turbine trips
Front standard push button
Control room push buttons
Customer 1 & 2 trips
Zero speed
High accel/ decel rates
Speed deviation
High vibration
Hydraulic pressure low
Exhaust vacuum trip
Lube oil pressure low
Emergency trip header tripped
High exhaust hood temp
High high drum level
What temp and pressure is the steam at each turbine?
HP-2400 psi and 1000°
CRH-525psi and 600°
HRH-500 psi and 1000°
LP-150 psi and 700°
Permissives to roll to 1000
Rotor warmed
Chest warmed and pressure equalized
Steam to metal mismatch +200, -100
HP bore temp 305
IP bore temp 135
MTLO >90°
Open all turbine drains
Start warming first bowl mill
Roll to 1000 while watching vibration, RSI, and alarms
Permissives to roll to 3000
Rotor stress must be less than 75%
Select 3000
Fast ramp through criticals
Sit on wobbulator for any HOLDS
HOLD- LO temp must be >100° and IP bore must be >220° to roll past 3000rpm
Close Ring bus
Permissives to roll to 3600
Continue watching RSI, vibrations, and alarms
Fast roll through 3200
Watch EX2100 at 3420
Journal bearing Temp Alarms
Alarms at 225°
Max temp is 250°
Thrust bearing temp alarms
Alarms at 180°
Max metal temp 190°
What is the SPCV?
Steam packing cooling valve takes cold reheat steam from front standard end of HP shell and sends it to #2 packing to help cool the seal steam leak off
What is Rotor long?
Rotor long means the rotor is growing faster than the shell. The differential expansion is greater, and the clearances decrease faster.
What is rotor short?
Rotor short means the rotor is contracting faster than the shell usually due to a drop in load
What is all contained in the front standard?
Journal bearing #1
Turbine shaft driven oil pump
Shell expansion detector
S1600 trip manifold assembly
Eccentricity detector
Extraction relay dump valve
Turbine speed sensors
When is the turbine self sealing?
Turbine is self sealing at 40% load
Requirements for initially putting seals in service
Gland steam exhauster on
Block valve open
Slowly open regulator
10 minutes to start vacuum pumps
What is the purpose of the diverting valve?
The diverting valve relieves excess steam from seals.
<300° goes to 7A heater
>300° goes back to condenser
What is a general flowpath of the steam seals?
Steam seals leave the turbine through the gland steam exhauster to the seal leak off tank then to the condenser
Requirements for placing seals on turbine and BFPT
Turbine on gear
Condensate pump running
EHC in service
Seal leak off tank in service
Gland steam exhauster running
Diverter valve to condenser
Root valve open (ASV-16)
S1(Main steam feed admission) & S2 (Regulator bypass) closed
Warm header and slowly open stead feed admission
Diverter to 7A heater at 50% load
What MTLO pressure do we maintain at the centerline?
25psi
What MTLO pressure do we maintain on the bearing header?
32psi
What rpm does the lube oil become self supplying from the main shaft oil pump?
3450rpm or 96% rated speed
How much oil can the MTLO tank hold?
8550 Gallons
When will the MTLO Bearing oil header trip?
12# on 2 out of 3 transmitters
When will the Main shaft pump discharge header trip?
100# on two out of 3 transmitters
When will the motor suction oil pump auto start?
When the main shaft suction drops below 10#
What can we use to help maintain 25#’s at the centerline?
3 valves on top of the booster pump. Bearing relief, Booster baffler, and Booster baffler bypass
What is normal stator water conductivity?
Less than .5
When does the first alarm come in for high water conductivity on the stator cooing water?
.5
When does the 2nd high water conductivity alarm come in at?
9.9
What is the Runback rate on the stator cooling water?
Will shed load at 99MW/min
What is the Rundown rate on the stator cooling water?
Will shed load at 9MW/min
If conductivity is less than .5 when no flow occurs how long do you have to trip?
60 minutes
If conductivity is more than .5 when no flow occurs how long do you have to trip?
3 minutes
What is the max cold gas temp on the generator?
46° C
What is the minimum cold gas temperature on the generator?
30° C
When does the High cold gas temperature alarm come in?
56° C
What are the 3 functions of the Seal oil?
Prevent hydrogen from escaping the generator shaft seals
Provide lubrication for the generator shaft seals
Prevent moisture and air from entering the generator casing
Where does the oil go the exits the generator side?
It is drained to the enlargement tank
Where does the oil that exits the bearing side go?
Auxiliary detraining tank
What pressure differential is maintained between the seal oil and the hydrogen pressure to keep hydrogen in the generator?
8psi
What are the sources of seal oil?
Main and recirculating seal oil pumps
Emergency seal oil pump
Main bearing oil header
When is hydrogen purity is most explosive and what do we try to maintain.
4%-75% is most explosive and we maintain >92%
What happens before and after selecting prewarming?
Turbine must be on gear with steam conditions met and vacuum retarded, then select prewarm. MSV’s and CRV’s will close, Control valves and HSFV will go wide open. Open MSV-2 bypass and try to get 55-70 psi on the HP exhaust.
Talk about gas flow when purging the generator
CO2 goes in and out of the bottom and Hydrogen comes in and out of the top
How do we convert AC to DC power in the generator?
Exciter converts from AC to DC
What is the voltage schedule on both units?
Unit 1- 166KV +-2
Unit 2- 520KV +-5
How do we adjust VARS when needed?
Raising unit voltage will raise VARS and Lowering unit voltage will Lower VARS
What is the min and max H2 pressure on the generator?
Max-75
Min-30
What type of generators do we have?
2 pole, 3 phase, 60hz, 3600 RPM
What cooling methods do we have for the generator?
Hydrogen cooled, and cooling water on the stator
What does the PSS do?
The Power system stabilizer a feedback monitor for the generator. It looks at Current, Voltage, and Speed. It comes on at 140 MW
Where are the RTD’s located in the generator?
In the stator windings
Where are the thermocouples located in the generator?
Located on the outlet of the stator windings
When taking the unit off, when can you turn off the lube oil pumps?
First stage metal temp must be below 500° so that the bearing temp will be below 300°
What are the normal and emergency transfer switch locations for the ex2100?
Normal-1C11
Emergency-1C24
What is the flowpath of the ex2100?
From the transfer switch to the transformer which steps it down from 480 to 180, then it goes to one of two rectifier bridges which converts it to DC. The C controller is watching the health of M1 and M2.
What are the min and max voltage limits on the generator?
24.5-27.3
What are the 3 basic types of power and what do they do?
Apparent- combo of real and relative
Real- Power that performs real work
Reactive- power in distribution and transmission
What all does ATSI look at?
Eccentricity, vibration, expansions, metal temp, speed, and valve positions
What are our limits on eccentricity?
1.8-2.2
3.0 is max
What is the RSI used for?
Rotor stress indicator calculates stress in the HP and IP rotor and displays stress values.
Also used to measure and monitor cyclic life expenditure.
In the RSI is the predicted stress or the actual stress more useful?
Predicted stress is more useful because it takes a very long time for the bore stress to respond to temperature changes at the rotor surface
What are TRACS drawings?
What are MSI drawings?
Technical references and control system-
What is the Fracture appearance transition temperature (FATT)?
Zones 1 & 2 are below the FATT and indicate over stressing the bore in a cold condition
Zone 3 indicates over stressing in a hot condition.
What does Shell expansion refer to?
Shell movement towards the front standard
What does differential expansion refer to?
Rotor movement relative to the shell
What does rotor expansion refer to?
Movement between the turning gear and rotor
How does the eccentricity meter work?
It is an 8:1 ratio. Located about 1’ from the bearing centerline. It uses an 80 tooth magnetic pickup
When does vibration trip the turbine?
Bearings 1-10 will trip turbine at 10mills
Bearings 11 & 12 will trip turbine at 7 mills
What do we use to determine the position of the turbine valves?
LVDT- linear variable differential transformer is used to tell valve positions
How many stages are on each turbine section?
HP-7 stages
IP-5 stages
LP-6 stages
What’s the normal thrust bearing inlet temp?
110°-120°
Normal temp rise should not exceed 45°
When do the LP hood diaphragm’s blow out?
5#’s
What devices do we use to monitor differential expansion and where are they located?
DxD1 is located in the front standard. It measures differential expansion between HP rotor and HP shell
DxD2 is located between reheat shell and LP-A exhaust hood. It measures differential expansion between reheat rotor and shell
How many horespower is our turbine rated for?
1 million HP
What is back pressure, what are the limits, what impacts the back pressure?
The pressure at which the condesned water exits the condenser
Needs to be maintained under 5.5”. Turbine is only rated for 5”
Condenser, Cooling tower, Heaters and Dump valves
What does it mean if the lmcc is in turbine follow?
Boiler master is in manual, The turbine is going to maintain throttle pressure using the control valves
What does it mean if the lmcc is in boiler follow?
Turbine master is in manual, boiler is controlling throttle pressure using the feed rate and air flow. Boiler follow doesn’t react as fast as turbine follow
Why do we want our hood sprays to maintain temperature in the LP hood?
To prevent windage
How many brushes are on the shaft voltage monitor and what are they for?
4 total
2 for testing
2 for monitor
What is the generator D curve and how do we use it?
D curve is the Generator capability curve. It factors in the gas pressure, Gross MW, MVAR, and power factor to determine a safe operating range on the generator
How do we monitor stator cooling temp?
RTD’s and Thermocouples
What is the min and max stator inlet temp?
Min- 40°C
Max- 45°C
What can’t you discuss with EMO?
Can’t tell them anything transmission said
When do we call TCC?
Switchyard, voltage limits, voltage regulator in manual
How long can the ring bus be open for?
5 hours max
What is PCI and how do we use it?
Power cost incorporated
They are to communicate instructions for startup or outage
PCI is communication with SPO and EMO
What is the booster baffler pump for?
It provides the suction for the Main shaft pump and supply oil to the bearings
What to do if a rotor long condition comes in?
Usually only comes in while rolling up, put tilts in horizontal and lower fuel oil pressure to remove some heat until the shell can catch up
What is CEMS and what does it monitor?
Continuous Emissions monitoring system
NOX, CO, SO, Opacity, Mercury
What do the colors mean on the CEMS screen?
RED- Alarm or fault
TAN- In calibration
PINK- Invalid reading
YELLOW- In maintenance
What is the 86 relay for?
86 is a lockout relay, that will not reset until all faults are cleared and the relay must be manually reset
What is the 25 relay for?
Synchronism check relay- used when connecting a unit to the system
What is the 24 relay for?
Volts/hertz relay only operates when the ratio of voltage to frequency is above or below a preset value. Will trip 86
How often does the CRO have to conduct a routine visual check of GPS relay?
Every 24 hours and must be put in NERC log
Why do we open the hydrogen vent when the unit is down?
Because there is no pressure to circulate the gas flow
Flowpath: Generator> flowmeter> thermal analyzer(325)>dryer>solenoid> Back to GEN or to vent
What is the steam flowpath through the HP turbine?
Stop valves, control valves, 4 steam leads, 2-1st stages then meet back together at 2nd stages, then go through 7 stages
What are signs of water induction into turbine?
Drop in steam temp, water hammer, or vibration
What happens on a heater hi level?
Dump valve opens
What happens on a heater hi hi?
Extractions close, inlet and outlet closed, bypass open
What is the max steam temp change the turbine is rated for?
100° every 15 minutes
When does the PSS come on?
140 MW
How to close breakers on unit 1 when tying on?
4 breakers, two transformers. Auto synch 1 breaker, manually sync the other transformer, adjust voltage, then close the other two breakers
How to close breakers on unit 2 when tying on?
2 breakers, 1 transformer, get permission to open ring bus, close B6191, auto synch B6122, adjust voltage, then close other breaker
What is CIP?
Critical infrastructure protection
Protection for the switch yard and the TCA removable media
What is the TCA?
Transient Cyber Assets
This is in regards to removable media within plant computer systems
What is PM&D?
Performance monitoring and diagnostics
They continuously monitor the plant operations to find any abnormalities and they will call to let you know if they see anything that isn’t normal.
What is EMO?
The energy management organization is the balancing authority between us and MISO
What is PCI?
Power cost incorporated is our communication system with MISO and EMO
What is TCC?
Transmission control center monitors and controls the high voltage transmission system
What is NERC?
North American Electric Reliability Corporation. Maintains the reliability of the grid
What does POE refer to?
Plant operational excellence refers to
