Gas Turbine Control & Protection Systems by David Lucier PAL Engineering
Control Systems
What must be “controlled” on GE gas turbines?
9 Turbine Shaft Speed 9 Rate of Change of Speed (a.k.a. Shaft Acceleration)
9 Exhaust Temperature 9 Rate of Change of Temperature 9 Air Flow through Compressor
9 TNH units: RPM or % speed Acceleration: RPM/second or % speed/second
9 TTX units: Degrees Fahrenheit (˚F ) Exhaust Temperature Rate: ˚F per second
9 Airflow: lbs-air per hour (actual flow not measured)
What devices do the controlling?
9 Liquid Fuel Bypass Valve 9 Gas Stop Speed/Ratio Valve 9 Gas Control Valve 9 Variable Inlet Guide Vanes
Modern GE Control Systems
Mark IV Control Panel, TMR (1982 – 1989 Era)
Mark IV Operator Panel
Mark IV Screen
Mark V Control Panel, TMR (1989 – 2000 Era)
Human Machine Interface Original versus New
Human Machine Interface (Close-up of HMI Main Screen)
Typical HMI Screens (Mark V)
Control Principles
Minimum Value Select: The control sub-system “calling for” the least fuel flow will be in command.
Simplified Minimum Value Select
(18) TC’s TTXM %TNH
%TNH/sec FSR Limits
Min & Max Value Gates MIN MAX
MIN (6 inputs)
9 Liquid Fuel Bypass Valve, BPV 9 Gas Stop Speed/Ratio Valve, SRV 9 Gas Control Valve, GCV 9 Variable Inlet Guide Vanes, IGV
Triple Modular Redundant (TMR) (Speedtronic™ Mark IV thru VI) TMR
> BPV > SRV > GCV > IGV
Temperature Profile Diagram (Base Load Operation) INLET
EXHAUST
< Temperature >
3000 ˚F
solid line graph >
59˚F < 45˚F
<
20 Tf =
F 20 ˚
TTX = 1000 ˚F
< 500
˚F
Pressure Profile Diagram (Base Load Operation) INLET
EXHAUST
150 psia
14.7psia
<
e ur s es r P
dotted line graph > 14.3 psia
>
psia 9 4 <1
>
14.7 psia
Gas Turbine Start-up Curves
= 900
˚F >
%TNH
Sp ee d
Ex h. Te m
p
TTX
Speed
26% 19.5%
Fuel Stroke Ref, FSR
TTX = 550 ˚F
Fuel Stroke Reference
% FSR > >
(FSR constants for Start-up)
Constants List
Start-up FSR Algorithms
TIME, Seconds > >
Liquid Fuel Control Principles
Fuel Control Principles
Fuel Flow is proportional to: Bypass Valve Position &
Fuel Pump Speed
FFN = ƒ (%FSR) x ( %TNH)
Liquid Fuel Flow z
TNH measured 0 to 100 % speed
z
FFN measured in frequency (measure speed of flow divider)
z
FSR measured 0 to 100 percent of Bypass Valve (full open to closed) FFN = ƒ (%FSR) x ( %TNH)
Liquid Fuel Flow Principles z
Fuel Pump is driven by Turbine through Accessory Gear Box (% TNH)
z
By-pass Valve Position is controlled by Speedtronic™ Panel (% FSR)
z
Flow divider speed is proportional to fuel flow (FFN, gal/min)
Liquid Fuel Control Fundamentals FFN = ƒ (%FSR) x ( %TNH)
---> <---
- - ->
--->
- - -> - - ->
--->
70.7 cps/gpm
< FFN
%FSR >
< %TNH
Roper Liquid Fuel Pump & Bypass Valve
<
>>>
>>>
<<
< < < >>>
>>>
<< Fuel Bypass Valve
IMO Liquid Fuel Pump
Scre wP ump
Liquid Fuel Bypass Valve
Servovalve 65FP >
Bypass Valve
Flow Divider Speed Pickup (77FN-1)
77FN-1 >
Flow Divider
Flow Divider Speed Pickups (77FN-2, 3)
2, FN 7 7
> > 3
Liquid Fuel Flow Calibration (from GE Control Specifications) Flow Divider Characteristic: 60-tooth wheel 4600 cps = 65 gallons/min
Therefore, 70.7 cps per 1.0 gpm
Liquid Fuel Flow Calibration (from GE Control Specifications, ISO conditions)
Fuel Flow = .0085 (%FSR) x (%TNH) 1. Assume for “firing” fuel: %FSR = 14 %TNH = 16 Firing Fuel = .0085 (14) (19) Firing Fuel Flow Rate = 1.90 gpm
Liquid Fuel Flow Calibration (GE Control Specs, ISO conditions)
Fuel Flow = .0085 (%FSR) x (%TNH) 2. Assume for “full speed/no load” fuel: %FSR = 14 %TNH = 100 Firing Fuel = .0085 (14) (100) FSNL Flow Rate = 12.0 gpm
Liquid Fuel Flow Calibration (GE Control Specs, ISO conditions)
Fuel Flow = .0085 (%FSR) (%TNH) 3. Assume for Base Load Operation: %FSR = 66.6 %TNH = 100 Firing Fuel = .0085 (66.6) (100) Base Load Flow Rate = 57.2 gpm
Gas Fuel Control Principles
Gas Stop Speed/Ratio & Control Valve
Gas Fuel Control Fundamentals
P1
P2
P3
Gas Fuel Pressure Gages
P1
P2
P3
Gas Stop Speed/Ratio (SRV) & Gas Control Valve (GCV)
< SRV GCV >
P2 Pressure Transmitter (96FG) P1
P2, Pressure Transducer > >
Gas Stop Speed/Ratio (SRV) & Control Valve (GCV) < SRV GCV >
< 90SR
< 65GC
Servovalves
Speed/Ratio Valve Calibration (from GE Control Specifications)
P2 = Speed Ratio (% TNH) TNH – Preset P2 = .49 (%TNH) %TNH – .50
P2
P2 in DC volts
Speed/Ratio Valve Calibration
P2 = Speed Ratio (% TNH) TNH – Preset 96FG transducer calibration 0 to 5.0 DC volts = 0 to 300 psig P2 = 2.95 (%TNH) – 30 in psig
Speed/Ratio Valve Calibration (from GE Control Specifications)
P2 = 2.95 (%TNH) – 30 in psig At 100% shaft speed
P2 = 265psig, constant
P2
Inlet Guide Vane Control Principles
Variable Inlet Guide Vanes (VIGV)
Inlet
Guid e
Vane
gle > n A IGV
< IGV Actua tor >
IGV Actuator & Position Indicator
< 96 < L TV V -1 DT ,2 ,
IGV Control Fundamentals
Servovalve 90TV >
IGV Control
RV D T
(Control air flow into compressor)
20TV >
< < IGV Modulating > >
Servovalve 90TV >
Summary of Control Principles
Summary of Control Systems (System calling for “least” fuel controls FSR)
Min Fuel
FSR
MVG <6
I np ut S ign als
Protection Systems
Four Primary Protections: 9 Overspeed 9 Overtemperature 9 Loss of Flame 9 Vibration
Four Primary Protections (typical settings): 9 Electronic Overspeed: 110 % TNH 9 Mechanical Overspeed: 112% TNH 9 Overtemperature (~ 1000 ˚F) 9 Loss of Flame 9 Vibration (1 inch/second, 5 mils peak-peak)
Triple Modular Redundant (TMR) (Speedtronic™ Mark IV & V) TMR
> BPV > GCV > SRV > IGV
Logic “0” or “1”
2/3 Voting
Many Secondary Protections including: 9 9 9 9 9 9
Low Lube Oil Pressure High Lube Oil Header Temperature Low Hydraulic Pressure Generator Lockouts Customer Added Protections Other, as required
Protection Systems (High-pressure Hydraulics)
L 4 “trips” >
25 psig
1200 psig
Protection Systems (20 FG energize to run, de-energize to trip) < L 4 “trips”
Solenoid Valve Deenergizes !
1200 psig
< St op Clos Valve es ! !
Redundancy by Association (Control & Protection Systems)
If operating on Liquid Fuel: when stop valve closes, the bypass valves goes to “full recirculation.”
Protection Systems (If a trip occurs, BPV goes to 100% fuel recirculation) St o Cl p V os alv es e >
[zero flow]
10 0
%
fu
el re cir cu l
at io n
>
<<<<
<<<<
>>
>>>>
>>
Flow Divider Stops
Redundancy by Association (Control & Protection Systems)
If operating on Gas Fuel: when stop valve closes, gas control valve also closes immediately.
Protection Systems (If a trip occurs, both valves close)
Close >>>
Close >>>
Redundancy by Association (Control & Protection Systems)
Inlet Guide Vanes: When a trip occurs, IGV go toward the “closed” position immediately to prevent compressor surge.
Protection Systems (If a trip occurs, IGV Close)
DT V R
rgizes >
< < < IGV Close
20TV de-ene
Summary (Control & Protection Systems)
• Shaft Speed Control • Shaft Acceleration Control • Overspeed Protection • Exhaust Temperature • Rate of change of Temperature • Overtemperature Protection • Vibration • Loss of Flame • All Other Protective Devices
The End Thank you for your attention!
Questions ?
