2909148-GAS-TURBINE-13
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Description
Gas Turbine Control Philosophy
Gas Turbine Rotating Blow Torch Designed to Run at the Ragged Edge of Self Destruction
C
T
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Gas Turbine Rotating Blow Torch Designed to Run at the Ragged Edge of Self Destruction
C
T
G
Speedtronic Control System
Control System for Gas Turbine
Gas turbine is controlled Speedtronic control system
Control loops includes
Start-up
Acceleration
Speed
Temperature
Shutdown and
Manual Control functions
Speedtronic Control loops
Major Control loops
Secondary control loops
Start-up Start-up Acceleration Acceleration
Speed and
Temp Temper era ature ture Shut hutdow down
Manual FSR and
Output of these control loops is fed to a minimum value gate Display circuit Fuel Temperature Display
Speed
Acceleration Rate Display Start Up Shut Down
M I N
FSR
To Turbine
Speedtronic Control loops
Fuel Stroke Reference (FSR)
Command signal for fuel flow
Controlling FSR
Lowest of the six control loops
Establishes the fuel input to turbine @ rate required by system which is in control
Only ONE control loop will be in control at anytime.
The control loop which controls FSR is displayed in operator friendly CRT.
Startup/Shutdown Sequence and Control
Startup control brings the gas turbine
Allows proper fuel to establish
Command signals to Turbine Accessories, Starting device and Fuel control system
Safe and successful start-up
Flame & Accelerate the turbine in such a manner as to minimize the Low cycle Fatigue of the hot gas path parts during the sequence
Software Sequencing involves
Zero speed up to Operating speed.
depends on proper functioning of GT equipment.
Software Sequencing ensures safe operation of Turbine
Startup/Shutdown Sequence and Control
Control logic circuitry is associated not only with actuating control devices, but enables protective circuits and obtains permissive conditions before proceeding.
Control settings play a vital role in determining the proper sequencing.
Actual site specific control settings are generated by M/s GEICS,USA.
Speed detection - by magnetic pickups
L14HR Zero-Speed (Approx. 0% TNH) L14HM Min Speed (Approx.. 16% TNH) L14HA Accelerating Speed (Approx. 50% TNH) L14HS Operating speed (Approx..95% TNH)
Startup/Shutdown Sequence and Control
Actual settings of speed relays are listed in Control specification.
The control constants are programmed in processors EEPROM.
Always ensure correct site specific, machine specific control specification.
Consult your system designer for any queries.
Start-up Control - FSRSU
Open loop control
Uses preset levels of fuel command
Various Fuel levels
Zero, Fire, Warm-up, Accelerate and Max.
Typical values for Frame-6
Fire
15.62%
Warm-up
11.62%
Accelerate
19.82%
Maximum
100%
Open Loop Control
Start-up Control - FSRSU
Startup control FSR (FSRSU) signal operates through the MIN value gate to ensure other control functions can limit FSR as required.
FSRSU FSRACC FSRN FSRT
FSR MIN
FSRSYN FSRMAN
FSR = FSRSU
Start-up Control - FSRSU
Speedtronic Control Start-up software generates Fuel command signal (FSR).
Speedtronic Control Software also sets the MAX and MIN limits for FSR for Manual Control FSR [ FSRMIN < FSRMAN < FSRMAX ]
When Turbine Breaks away (starts to rotate)
L14HR pick-up
Starting clutch solenoid 20CS de-energizes
Shuts down the hydraulic ratchet motor (88HR)
Acceleration Control - FSRACC
Acceleration control software
compares the present value of Speed signal with the value at the last sample time. Difference between these two numbers is a measure of acceleration.
When actual acceleration is greater acceleration reference, FSRACC is reduced, which reduces FSR, thus reduction in fuel supply to turbine.
During startup-acceleration reference is a function of turbine speed.
Acceleration control takes over after Warm-up state.
Acceleration Control - FSRACC
Acceleration reference is a Control constant programmed in EEPROMS Typical
0.35 %/sec
0.10 %/sec 0%
40% 50% 75% 95% 100%
TNH
Acceleration Control - FSRACC FSRSU FSRACC FSRN FSRT
FSR MIN
FSRSYN FSRMAN
FSR = FSRACC
Speed Control - FSRN
Speed Control System software
controls the speed and load of the gas turbine generator in response to the actual turbine s peed signal (TNH) and the called-for speed reference(TNR)
TNH
TNR
FSRN
Speed/Load Control
Speed/Load Reference:
Speed control software will change FSR in proportion to the difference the actual turbine generator speed (TNH) and the called-for reference (TNR)
Reference Speed (TNR) range
Start-up speed reference is 100.3%.
95% (min) to 107% (max) for a generator drive turbine
This is preset when START signal is initiated.
Turbine follows 100.3% TNH for synchronization
Speed/Load Control
Turbine Speed is held constant when Generator Breaker is closed onto Power grid
Fuel flow in excess of the necessary to maintain FSNL will result in increased power produced by the generator.
Thereby Speed control becomes Load control loop
Speed Control:
Isochronous Speed control
Droop Speed Control
Isochronous Speed Control
TNH
FSRNI
TNR FSRSU FSRACC FSRN (or FSRNI) FSRT
MIN
FSR
FSRSYN FSRMAN
FSR = FSRN
Droop Speed Control
Droop Control is a proportional control.
Any change in actual speed (grid frequency) will cause a proportional change in unit load.
This proportionality is adjustable to the desired regulation or ‘Droop’ 104 % R N
d e e p S
T e c n er ef e R
D r oo p 10 4% s e tt i ng FSNL
100 %
95% ll
R S F d a o L o N d e e p S u
1 0 0 % S e tp o in t
Low Speed Stop
R S F d e t a R
Speed/Load Control loop Raise
Lower
Rate
LOG SETPOIINT
Speed Ref. Command
Rate
Speed Target MANUAL SETPOINT
Power
Primary Os
Speed Error
Preset Ememrgency Os
Mechanical Os Load Raise
Rate
Load Lower
LOG SET POIINT
Load Rate
Speed
Load Ref. Cmd MANUAL SET POINT
Preset
Load Setpoint
SPEED CONTROL
Speed Control Schematic SPEED CONTROL
FSNL TNR SPEED REF.
+
+
ERROR +
-
FSRN
SIGNAL
TNH SPEED DROOP
RST>
SPEED CHANGER LOAD SET POINT MAX. LIMIT L83SD RATE L70R RAISE
L83PRES PRESET LOGIC
L70L LOWER
MEDIAN SELECT
PRESET OPERATING
START-UP
L83TNROP MIN. SELECT LOGIC
or SHUT DOWN
MIN.
TNR SPEED REF.
Synchronising - FSRSYN
Automatic synchronization software
Bus and Generator voltage are input signals to Protective core .
Isolation transformers are built into core
software drives the synch check and system permissive relays.
Algorithms programmed into controller and software.
Sequencing and algorithms are programmed into EEPROM
hardware and software sends voted command to actual breaker closure.
Auto Synchronisation Speed
stem
Raise Speed Speed Matching Lower Speed
requency Speed Raise Volts Generator Volts
System Volts
Voltage Matching Lower Volts
Synchronising Scheme AUTO SYNCH PERMISSIVE Gen Volts
A A>B
REF
B AND
Line Volts
L83AS Auto Synch Permissive
AUTO SYNCH
A A>B
REF
B
Calculated Phase within Limits Calculated slip within Limits Calculated Acceleration Calculated Breaker Lead Time
AND
L25 Breaker Close
Temperature Control - FSRT
Temp.Control software/algorithms
limit fuel flow to the turbine to maintain internal operating temperatures within design parameters of turbine hot gas path parts.
Highest temperature is in the flame zone of combustion chambers.
TTXM TTREF
FSRT
Firing Temperature
Firing temperature - temperature of gas as it exits the first stage nozzle.
Speedtronic limits this firing temperature.
Firing temperature is calculated by
thermodynamic relation ships GT performance calculations, and site conditions as a function of Exhaust Temp(Tx) and CPD fuel
air
C
T
ISO FIRING TEMP T
) x T( er u t ar e p m e t t s u a h x
C Isothermal o n s t F i r in g T e m p ( Li ne a r i ze d )
Firing Temperature
Firing temperature can also be approximated as
a function of Tx and Fuel flow (FSR) and
as a function of Tx and Generator MW output
Line of constant firing temperature are used in control software to limit the gas turbine operating temp
whereas the constant exhaust temperature limit protects the exhaust system during start-up.
TA TB TC
TA > TB > TC
) x T( er ut ar e p m e t t s u a h x E
C Isothermal o n s t F i ri ng T e m p ( Li ne a r i ze d ) Fuel Stroke Reference (FSR)
Exhaust Temp control software
Series of application programs written to
perform critical exhaust temperature control and monitoring.
Major function is –
Exhaust temperature control.
Software is Programmed for
Temperature control command
Temperature control bias calculations
Temperature reference selection.
Temperature Control Schematic
If ONE Controller should fail, this ogram ignore the readings from the
TTXDR TTXDS TTXDT
iled Controller. TTXM is based on
To Comb. Monitor
TTXD2 SORT HIGHEST TO LOWEST
maining controllers thermocouples. Alarm will be generated Temp Control Ref
QUANTITY of TC’s Used
CORNER
REJECT HIGH AND LOW
AVERAGE REMAINING
TTXM
Temperature Control -
CPD
REJECT LOW TC’s
+
-
FSRMIN FSRMAX
+
SLOPE
TTRXB
SLOPE
-
+
FSR
MIN. SELECT
CORNER
TTXM
+
+ -
MEDIAN MEDIAN SELECT
+
FSRT
+
GAIN
FSR ISOTHERMAL
The temp-control-command program in compares the exhaust temp control setpoint (calculated in the temp-control-bias program and stored in computer memory) TTRXB to the
Temperature Control Bias program DIGITAL INPUT DATA
SELECTED TEMPERATURE REFERANCE TABLE
T T K n _B
COMPUTER MEMORY
TEMPERATURE CONTROL BIAS PROGRAM
COMPUTER MEMORY
x E
CONSTANT STORAGE
TTKn_K Isothermal TTKn_C
F
S C R P B D I AS B I A S
CPD FSR
Temperature Control Bias Temp control Bias program calculates the Exhaust
er ut ar TTKn_I e p m e T t s a u h
T T K n _M
Exhaust Temp Control Setpoints
TTKn_C (CPD bias corner) and TTKn_S (CPD bias slope)
temp control setpoint TTRXB based on CPD data
are used with the CPD data to determine the CPD
stored in computer memory and constants from the
bias exhaust temperature setpoint. TTKn_K (FSR bias corner) and TTKn_M (FSR bias slope)
selected temp-reference table.
This Program also calculates another setpoint based
are used with the FSR data to determine the FSR
on FSR and constants from another temperature-
bias exhaust temperature setpoint.
Temperature Control Bias Program
This Program selects the minimum of the three set points, CPD bias, FSR bias, or isothermal setpoint for the final exhaust temperature control reference.
During normal operation with Gas or light Distillate fuels, t his selection results in a CPD bias control with an isothermal limit.
CPD bias setpoint is compared with the FSR bias setpoint by the program and an alarm occurs when the CPD setpoint exceeds the FSR bias setpoint.
During normal operation with Heavy fuels, FSR bias setpoint will be selected to minimize the turbine nozzle plugging on firing temperature.
FSR bias setpoint is compared with CPD bias setpoint and an alarm occurs when the FSR bias setpoint exceeds the CPD bias setpoint.
A ramp function is provided in the program to limit the rate of setpoint change. Both Max (TTKRXR1) and Min (TTKRXR2) change in ramp rates (slopes) are programmed.Typical rate change limit is 1.5deg F.
The output of this ramp function is the Exhaust temp.control setpoint which is stored i n the computer memory.
Temperature Reference Select Program
Exhaust temperature control function selects control set points to allow GT operation at firing temperatures.
Temperature-control-select program determines the operational level for control set points based on Digital input information representing temperature control requirements.
Three digital input signals are decoded to select one set of constants which defines the control set points necessary to meet the demand. Typical digital signals are BASE SELECT, PEAK SELECT and HEAVY FUEL SELECT
Digital Input Data
• When appropriate set of constants are selected they are stored in the selected-temperature-reference memory.
Temperature Reference Select
Constant Storage
Selected Temperature Reference Table
Temperature Reference Select Program
Fuel Control system
Turbine fuel control system will change fuel flow to the combustors in response to the fuel stroke reference signal(FSR).
FSR actually consists of two separate signals added together. FSR = FSR1 + FSR2 FSR1 = Called-for liquid fuel flow FSR2 = Called-for gas fuel flow
Standard fuel systems are designed for operation with Liquid fuel and/or gas fuel.
Servo Drive System
Servo drive System
The heart of Fuel Control System
3 coil Electro Hydraulic Servo Valve
Servo valve is the interface between the electrical and mechanical systems Servo valve controls the direction and rate of motion of a hydraulic actuator based on the input current to the servo. Servo valve contains three electrically isolated coils on the torque motor. Each coil is connected to one of the three controllers , thereby redundancy is ensured if one of the controller fails. A null-bias spring positions the servo so that actuator goes to the fail safe position when ALL power and/or control signal is lost.
Liquid Fuel System
Liquid Fuel system consists of
Fuel handling components –
Primary fuel oil filter (low pressure)
–
Fuel oil stop valve
- Fuel pump
–
Fuel bypass valve
- Fuel oil pressure relief valve
–
Secondary fuel oil filter (High pressure)
–
Flow dividers
- Combined Selector valve
–
False start drain valve
- Fuel lines & fuel nozzles
Electrical Control components –
Liquid fuel press sw (upstream) 63FL-2
–
Fuel oil stop valve limit sw 33FL
–
Fuel pump clutch solenoid 20CF
–
Liquid fuel pump bypass valve Servo valve 65FP
–
Flow divider magnetic pickups 77FD-1,2,3 and
–
Speedtronic Control cards TCQC and TCQA
Liquid Fuel System P&ID FQ1
FSR1
FQROUT
TCQA TCQA TCQC
TNH L4 L20FLX
PR/A Flow Divider
By-pass Valve Asm
77FD-1
65FP
Typical Fuel Nozzles Combustion Chamber
Diff Press Guage
63FL-2
Fuel Stop Valve
Conn.For Purge When Required OFV
AD
VR4
OF Main Fuel Pump Accessory Gear Drive
33FL OLT-
Atomizing Air 77FD-2 77FD-3
To Drain
False Start Drain Valve Chamber OFD
Fuel oil Control - Software
Control system checks the permissive L4 and L20FLX to allow FSR1 (closing bypass valve sends fuel for closing the Bypass valve to the combustors)
These signals control the opening and closing of the fuel oil stop valve. Fuel pump clutch solenoid (20CF) is energised to drive the pump when the Stop valve opens. Fuel splitter algorithm ensures requisite FSR when FSR1 is active FSR1 is multiplied by TNH - to make it a function of speed (an important parameter of Turbine)
to ensure better resolution at the lower, more critical speeds where air flow will be low. Net result is FQROUT- a digital liquid fuel flow command At Full speed, TNH does not change
Therefore FQROUT ~~ FSR
Fuel oil Control - Software
Analog signal is converted to digital counts and is used in the controllers’ software to compare to certain limits as well as for display in CRT.
The checks performed by software program
L60FFLH - Excessive fuel flow on start-up
L3LFLT - Loss of LVDT position feedback
L3LFBSQ - Bypass valve is not fully open when the stop is closed
L3LFBSC - Servo Current is detected when stop valve is
L3LFT - Loss of flow divider feedback
(L60FFLH persists for 2 sec and this fault initiates trip, L3LFT also initiates trip during start-up)
clos
Fuel Gas System
Fuel gas is controlled by
Gas Speed ratio/stop valve (SRV) Gas Control Valve (GCV)
(Both are servo controlled by signals from Speedtronic control panel and actuated by spring acting hydraulic cylinders moving against springloaded valve plugs)
GCV controls the desired gas fuel flow in response to the FSR command signal. SRV is designed to maintain a predetermined pressure (P2) at the inlet of the GCV as a function of turbine speed
P 2
P1
Fuel Supply
SRV
P3
GCV
To Turbine
Fuel Gas System
Gas Fuel System consists of
Fuel handling components –
Gas Strainer - Speed Ratio/Stop Vlv assembly
–
Control valve assembly
- Dump valves
–
Three pressure gauges
-
–
Gas manifold with ’pigtails’ to respective fuel nozzles
Electrical control components –
Gas supply press sw 63FG
- Fuel gas press xducer(s) 96FG
–
Gas fuel vent sol valve 20VG -LVDTs 96GC-1,2 & 96SR-1,2
–
Electro hydraulic servo vlv 90SR & 65GC
–
Speedtronic control cards TBQB and TCQC
Fuel Gas System P&ID TCQC
FPRG POS2 FPG
FSR2
SPEED RATIO VALVE CONTROL
TBQB
TCQC
TCQC
GAS CONTROL VALVE SERVO
GAS CONTROL VALVE POSITION FEEDBACK
POS1
96FG-2A 96FG-2B 96FG-2C TRANSDUCERS
63FG-3
20 VG
COMBUSTION CHAMBER
Gas Control Valve
Stop Ratio Valve
GAS
VENT
P2 LVDT’S 96SR-1.2 TRIP
LVDT’S 96GC-1.2
Vh5-1 Dump Relay 90SR SERVO
90GC SERVO
GAS MANIFOLD
Gas Control Valve
Gas Control Valve
GCV position is proportional to FSR2
(Actuation of spring-loaded GCV is by a hydraulic cylinder controlled by an Electrohydraulic servo valve)
GCV will open only when permissive L4, L20FGX and L2TVX (purge complete) are true. –
Stroke of the valve is proportional to FSR OFFSET
GAIN
FSR2
L4
HI SEL
L3GCV
GCV stem position is sensed by LVDTs and
Analog I/O
FSROUT
FSR2 goes through Fuel splitter algorithm. TCQC converts FSROUT to an analog signal.
TBQC
GCV GAS P2 GCV Position Loop Calibration
fed back to an op-amp on TCQC card to compare with FSROUT input signal at summing junction. Op-amp on TCQC converts error signal and sends
LVDT’S 96GC -1,-2
Servo
T D V L
n oi t i s o P
Speed Ratio/Stop Valve
TNH
It is dual function valve
OFFSET
As a Stop Valve - integral part of protection system
FPRG
+
D
-
FPG
L4 L3GCV
During a trip or no-run condition, a posive voltage bias is placed on servo coils holding them in the “valve closed” position
SRV GAS
Op Cyl Posn Trip Oil
Servo Valve
A HI SEL
Speed Ratio/Stop Vlv has Two control loops Position loop similar to GCV Pressure control loop • Fuel gas pressure P2 at the inlet of GCV is controlled by the pressure loop as a function of turbine speed (in proportion to the turbine speed TNH) to become Gas fuel press Ref FPRG • TCQC card converts FPRG to analog signalP2 (FPG) is compared to the FPRG and the error signal is in turn compared with the 96SR LVDT feedback to reposition the valve as in GCV loop
–
GAIN
(It serves as a pressure regulating valve to hold a desired fuel gas pressure ahead of GCV)
POS2
96FG-2A 96FG-2B 96FG-2C
96SR-1,2 LVDTs
Analog I/O Module
TBQB
Dump Relay
Hydraulic Oil
SRV Pres Calibration
P2
GCV & SRV schematic GAS FUEL CONTROL VALVE
GAS CONTROL FQROUT SERVO GAS CONTROL VALVE VALVE OUTPUT COMMAND OUTPUT
GAS FUEL REFERENCE
GAS CONTROL VALVE POSITION
GAS RATIO VALVE CONTROL
SPEED
GAS CONTROL VALVE` OUTPUT
REQUIRED PRESSURE
MIDVALVE GAS FUEL PRESSURE
SPEED RATIO VALVE POSITION
SERVO OUTPUT
SPEED RATIO VALVE COMMAND
Duel Fuel Control
Turbines designed to operate on both liquid and gaseous fuel systems are equipped with Control software accordingly.
Control software performs the following: – – – –
Transfer of one fuel to other on command Allow time for filling lines with the type of fuel to which turbine operation is being transferred. Mixed fuel operation Operation of liquid fuel nozzle purge when operating totally on gas fuel.
Software programming involves:
Fuel splitter Fuel transfer- Liquid to Gas Liquid fuel purge Fuel transfer-Gas to Liquid Mixed fuel operation logics and algorithms
Fuel splitter - software
FSR is splitter into two signals FSR1 & FSR2 to provide dual fuel operation. FUEL SPLITTER
A=B
L84TG Total Gas
A=B
L84TL Total LIQ
FSR is multiplied by the liquid fuel fraction FX1 to produce FSR1signal
MAX.LIMIT MIN.LIMIT
FSR1 is then subtracted from the
L83FZ Permissives
FSR signal to generate FSR2 signal
MEDIAN SELECT
RAMP
Rate
L83FG Gas Select
FSR = FSR1 + FSR2
L83FL Liquid Select FSR
LIQ Ref FSR1 FSR2 GAS Ref
Fuel Transfer - Liquid to Gas, Gas to Liquid Fuel transfer from Liquid to Gas
Transfer from Full Gas to Full Liquid FSR2
GT running on Liquid (FSR1) and GAS transfer selected. FSR1 will remain at its initial value, FSR2 will step-up to slightly greater than
U N IT S
FSR1 PURGE
Zero value (0.5%). This opens the GCV
Transfer from Full Liquid to Full Gas.
slightly to bleed down the inter valve volume.
FSR1
The presence of a high pressure than that required by the SRV would cause slow response in initiating gas flow. fter delay of 30 sec to bleed down the P2
U N IT S
FSR2 PURGE SELECT GAS
pressure and fill the gas supply line, the
Transfer from Full Liquid to Mixture.
software program ramps the fuel commands
FSR1
FSR2 to increase and FSR1 to decrease at a programmed rate through median select gate. Fuel transfer completes in 30 sec.
TIME
SELECT DISTILLATE
U N IT S
FSR2 PURGE
TIME
Fuel Control System
Liquid fuel Purge
To prevent the coking of the liquid fuel nozzles
Mixed fuel Operation
Gas Turbine can be operated on both GAS & LIQ in any proportion when operator choses to be on MIX mode.
Limits of fuel mixture are required to ensure proper combustion, gas fuel distribution and gas nozzle flow velocities.
% of gas flow must be increased as load is decreased to maintain the minimum pressure ratio across the fuel nozzle.
Modulated Inlet Guide Vane System
IGV system
Bang-Bang type (2 position)
Modulated
IGV modulates during
acceleration of turbine at rated speed.,
loading and unloading of the generator
deceleration of gas turbine
IGV modulation maintains
proper flows and pressures, and thus the stresses in the compressor. Maintains minimum pressure drop across fuel nozzles in Combined cycle operations maintains high exhaust temperatures at low loads.
Modulated Inlet Guide Vane Control IGV Operation:
CSRGV CSRGV
IGV REF
During start-up IGV is fully closed (34º)
CSRGVOUT
D/A HIGH SELECT
from 0% to 83% of corrected speed.
Analog I/O
Turbine speed is corrected to reflect the air conditions at 80ºF, this compensates for changes in air density as ambient conditions change.
HM 3-1
CLOSE
HYD. SUPPLY
t Amb.Temp >80ºF TNHCOR < TNH
I FH6 O N -1 U T
R P OPEN
t Amb.Temp TNH 90TV-1 2 1 A OLT-1
bove 83% IGV open at 6.7º per % increase in
C
TNHCOR. VH3-1
IGV open to minimum full speed angle 57º and
D
TRIP OIL
Inlet Guide Vane Operation By not allowing the guide vanes to close to an angle less than than the min full speed angle at 100%TNH, a min press drop is maintained across the fuel nozzles, thereby lessening combustion system resonance. For Simple Cycle operation
Fuel Open Max. Angle ) V G R S C ( G E D E L G N A V G I
IGV move to full open position at pre-selected exhaust temperature, usually 700ºF. For Combined Cycle operation, IGV begins to move to full open pos. as exh.temp approaches Temp. Control ref. temperature
Simple Cycle (CSKGVSSR)
Combined Cycle (TTRX)
MIN Full Speed Angle Startup Program
(Normally IGVs begin open when Tx is within
Region Of Negative 5th Stage Extraction Pressure
30ºF of temp control Ref.) 0
100
Corrected Speed -% 0 (TNCHOR) FSNL
100 BASE LOAD
IGV Control Schematic
Temp. Control Feedback
Temp. Control Reference
Compressor Inlet Temp.
Speed
Manual Command
IGV Part IGV Part Speed Ref. Speed Ref.
IGV Position
Inlet Guide Vane Ref.
Servo IGV Output Command IGV Reference
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