Basics of Power System Control and Protection
A. P. Sakis Meliopoulos
Georgia Power Distinguished Professor
School of Electrical & Computer Engineering
Georgia Institute of Technology
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.1
School of Electrical and Computer
Engineering
Chairman
Chairman (interim)
(interim)
Dr.
Dr. Douglas
Douglas B.
B. Williams
Williams
Associate
Associate Director
Director
Graduate
Graduate Affairs
Affairs
Associate
Associate Director
Director
Undergraduate
Undergraduate Affairs
Affairs
Computer
Computer Engineering
Engineering
Microelectronics
Microelectronics
Digital
Digital Signal
Signal Processing
Processing
Modern
Modern Optics
Optics
Electric
Electric Power
Power
Systems
Systems and
and Controls
Controls
Electromagnetics
Electromagnetics
Telecommunications
Telecommunications
Electronic
Electronic Design
Design
and
and Applications
Applications
Bioengineering
Bioengineering
Associate
Associate Director
Director
Associate
Associate Director
Director
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.2
Undergraduate Curriculum
ECE3070
ECE3070
Electromechanical Energy Conversion
ECE4320
ECE4320
Power System Analysis
ECE4321
ECE4321
Power System Engineering
ECE4330
ECE4330
Power Electronics
ECE4325
ECE4325
Electric Power Quality
NSF/ECEDHA Education Workshop
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1.3
Graduate Courses in Power Systems
ECE6320
ECE6320
Control and Operation of Power Systems
ECE6321
ECE6321
Power System Stability
ECE6322
ECE6322
Power System Planning
ECE6323
ECE6323
Power System Relaying
ECE8843
ECE8843
Topics in Electric Power
Computational Intelligence in Power Systems
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.4
Graduate Courses in Power Electronics
ECE6330
ECE6330
Power Electronic Devices & Subsystems
ECE6331
ECE6331
Power Electronic Circuits
ECE6335
ECE6335
Electric Machinery Analysis and Design
ECE6336
ECE6336
Dynamics & Control of Electric Machine Drives
NSF/ECEDHA Education Workshop
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1.5
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.6
Continuing Education
Power Systems Certificate Program
Core
Core Courses
Courses
•Power
•Power System
System Relaying:
Relaying: Theory
Theory and
and Application
Application
•Modern
•Modern Energy
Energy Management
Management Systems
Systems
•Integrated
•Integrated Grounding
Grounding System
System Design
Design and
and Testing
Testing
•Grounding,
•Grounding, Harmonics,
Harmonics, &
& Electromagnetic
Electromagnetic Influence
Influence Design
Design Practices
Practices
•Power
•Power Distribution
Distribution System
System Grounding
Grounding and
and Transients
Transients
•Power
•Power Electronic
Electronic Devices,
Devices, Circuits,
Circuits, and
and Systems
Systems
Elective
Elective Courses/Conferences
Courses/Conferences
•Fault
•Fault and
and Disturbance
Disturbance Analysis
Analysis Conference
Conference
•Georgia
•Georgia Tech
Tech Protective
Protective Relaying
Relaying Conference
Conference
-
All Courses are Coordinated by the Department of
Professional Education
-
All Courses are Offered Annually
-
Academic Administrator: A. P. Meliopoulos
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1.7
Present State of the Art: C&O and P&C
Model Based Control and Operation
Control & Operation
Real Time Model
State Estimation
Applications
Load Forecasting
Optimization (ED, OPF)
VAR Control
Available Transfer capability
Security Assessment
Congestion management
Dynamic Line Rating
Transient Stability
EM Transients, etc.
Visualizations
Markets:
Day Ahead, Power Balance,
Spot Pricing, Transmission
Pricing (FTR, FGR), Ancillary
Services
Protection & Control
Component
Protection
generators, transformers,
lines, motors, capacitors,
reactors
System
Protection
Special Protection
Schemes, Load Shedding,
Out of Step Protection, etc.
Communications
Substation Automation,
Enterprize, InterControl
Center
The Infrastructure for Both Functions is Based on Similar
Technologies: Thus the Opportunity to Merge, Cut Costs,
Improve Reliability Integration of New Technologies
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1.8
Power Systems Operation
Main Objectives
Tools
REGULATION
Frequency
Voltage
Net Interchange
Pollutants
DATA AQUISITION SYSTEM
SUPERVISORY CONTROL
STATE ESTIMATION
ANALYSIS
OPTIMIZATION
CONTROL
SECURITY
ECONOMICS
Net Interchange
Pollutants
Power Transactions
IPPs
Energy Balance Market
Ancillary Services
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
Restructuring
POWER MARKET (SMD)
TRANSMISSION TARRIFS (FTR,FGR)
CONGESTION MANAGEMENT
ERO (Electric Reliability Organization)
1.9
Component (Zone) Protection
G+GSU Backup
Bus
Line
20 kV
230 kV
Xfmr
•
•
•
•
•
•
•
Generators
Transformers
Buses
Transmission Lines
Motors
Capacitor Banks
Reactors, etc.
12kV
FDR
Zone
R
Radial
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1.10
System Protection
Out of Step (Transient Stability)
Transient Voltage Collapse
Reactance Grounded Gen
Reactance Grounded Gen
800 MVA-15 kV
800 MVA-15 kV
X1=15.5%,X2=18%,X0=9%
X1=15.5%,X2=18%,X0=9%
Va = 8.400 kV
1
G
2
Va = 61.99 kV
Va = 63.01 kV
BUS10
Illustration of Two Power System Swings:
(a)Stable – Out of Step Relay Should not Operate
(b)Unstable – Out of Step Relay Should Operate
Va = 42.02 kV
BUS-MID
Generator Angle
52 Degrees
Special Protection Schemes
Special Protection Schemes are Protective
Relaying Functions Concerned with the
Protection Against Special System Conditions
that May Lead to Catastrophic Results.
These System Conditions are Determined
with Extensive Studies of Specific System
Behavior. Using this Information a SPS is
designed that monitors the System and When
the Special System Conditions Occur
(Recognition Triggers) the System Operates
(Automatically or with Operator Review and
Action)
SOURCE-A
BUS20
1
2
Va = 8.238 kV
BUS30
G
2x47.4 mile 115 kV Transmission Line
Generator Angle
-49 Degrees
Illustration of Voltage Collapse Near the Center of
a Stable System Swing
Voltage Transitions Are Slow – Undervoltage
Protection Should not Operate
Load Shedding – Frequency / Voltage
NSF/ECEDHA Education Workshop
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A System Disturbance May Create Generation-Load Imbalance
Leading to Sustained Frequency Decline. This Condition, if not
Corrected, May Lead to Equipment Damage. The Condition Can be
Temporarily Corrected by Load Shedding Until Additional Generation
can be Dispatched.
Similarly, a Disturbance May Create Sustained Voltage Problems.
These problems Can be Also Corrected by Load Shedding
1.11
Control & Operation
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1.12
Modern Energy Management System Functional Diagram
DATA AQUISITION AND
PROCESSING SUBSYSTEM
ENERGY/ECONOMY
FUNCTIONS SUBSYSTEM
Load Forecast
Load Forecast
Unit Commitment
Power Bids
Ancillary
Services
State
Estimation
Automatic
Generation
Control
Displays
External
Equivalents
Congestion
Management
Transmission
Valuation
GPS Synchronized
Measurements
Network
Topology
Economic
Dispatch
Power
Balance
Market
SCADA
Measurements
Parameter
Estimation
Economic
Interchange
Evaluation
SECURITY MONITORING
AND CONTROL SUBSYSTEM
Optimal
Power Flow
Security
Dispatch
Environmental
Dispatch
Emergency
State
Emergency
Controls
Security
Monitoring
Normal
State
Contingency
Analysis
VAR
Dispatch
Extremis
State
Restorative
Controls
Insecure
State
Preventive
Controls
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.13
OVERVIEW OF ENERGY MANAGEMENT SYSTEMS
Data Acquisition and Processing Subsystem
G1
G2
MW Flow Measurement
MVAR Flow Measurement
kV Measurement
Disconnect Switch Status
Breaker Status
RTU
Contact Inputs
Analog Inputs
Contact Outputs
Analog Outputs
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
New Technology
GPS Synchronized
Measurements
(Phasors)
Communication
Link with Control
Center
Data
RTU
Commands
Master
Station
1.14
Network Configurator Example
Breaker
Oriented
Model
AutoBank
500kV/230kV
G1
SG1
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
AutoBank
500kV/230kV
G2
SG2
Bus
Oriented
Model
1.15
State Estimator
G1
• MEASUREMENTS:
G2
1
• STATE:
3
T1
2
• FORMULATION:
T2
• SOLUTION:
4
L1
Interconnection
Interconnection
Traditional
State
Estimation
L3
L2
5
T1
MW Flow Measurement
MVAR Flow Measurement
kV Measurement
Transformer Tap Measurement
Centralized
Procedure
6
Observability
Bad Data Detection/ID/Rejection
Parameter Estimation
NSF/ECEDHA Education Workshop
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1.16
Technological Developments
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1.17
The OLD and the NEW
Circuit
Breaker
CT
CCVT
Relays
P
Circuit
Breaker
CT
CCVT
Q
I
V
IED-Relay
Comm Link
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.18
SCADA Evolution
Indicator
Control
SCADA circa 1923
Independent of Protection
To Data Base
Remote Access
Control Center
User
Interface
Communication
Standards
Encoder
Decoder
GPS
Communications
Terminal
RTU
IED
Disturbance
Recorders
Relays
SCADA circa 2003
SCADA
NSF/ECEDHA Education Workshop
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Communications
Terminal
Local
Computer
1.19
Project Background: Substation Architectures: SmartGrid
Protection, Control,
Communications
Physical System
GE
Hardfiber System
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Industry Direction: Single Data Acquisition
System for Protection, Control, and Operations
1.20
Important New Technology
GPS-Synchronization
History of GPS-Synchronized
Measurements
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1.21
History of GPS-Synchronized
Measurements
GPS Satellite System
Initiated 1989, Completed 1994
The Antikythera Mechanism
87 BC
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1.22
Important Milestones
1970: First Computer Relay (PRODAR, Westinghouse,
Gilcrest, Rockefeller, Udren)
1984: First Commercial µProcessor Based Relay (SEL)
1989: GPS Signal Becomes Commercially Available
1990-91: Phasor Measurement System (Arun Phadke)
1992: Phasor Measurement Unit (PMU) (Jay Murphy,
Macrodyne)
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.23
Arun Phadke’s
Arun
Phasor
Phadke’s
Measurement
PMS
System
Block
BlockDiagram
DiagramPublished
Publishedby
byArun
ArunPhadke
Phadke
Vintage 1990-92
Vintage
1990-91
several units
were
soldUnits
to
Several
AEP,
WereNYPA,
Sold to
others
AEP, NYPA,
others
CHARACTERISTICS
Time
TimeAccuracy
AccuracyWas
WasNever
NeverMeasured
Measuredor
orReported.
Reported.
Multiplexing
and
Design
Suggest
Very
High
Multiplexing and Design Suggest Very HighTiming
TimingError
Error
Estimated
Time
Precision:
100
us,
2
degrees
at
60
Hz
Estimated Time Precision: 100 us, 2 degrees at 60 Hz
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
•
Analog Filter with
Cutoff Frequency of
360Hz
•
Sample & Hold A/D
Technology with
Analog Multiplexing
•
12 bit S&H A/D 720
s/s
1.24
Macrodyne 1620 PMU
Released to Market January 1992
Jay Murphy (Macrodyne) Was First to Introduce
Term PMU: Phasor Measurement Unit
Input Protection &
Isolation Section
GPS
Antenna
A/D Converter
(Σ∆ Modulation)
Optical
Isolation
Digitized
Data
2880 s/s
CHARACTERISTICS
GPS
Receiver
Optical
Isolation
PLL
Sampling Clock
Input Protection &
Isolation Section
A/D Converter
(Σ∆ Modulation)
Optical
Isolation
Master
Workstation
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
µP
Optical
Isolation
Digitized
Data
2880 s/s
•
Individually GPS
Sync’d Channels
•
Common Mode
Rejection Filter with
Optical Isolation
•
16 bit A/D Σ∆
Modulation
IRIGB
Memory
Analog
Inputs
V : 300V
I : 2V
1PPS
Display
&
Keyboard
RS232
Data
Concentrator
(PC)
Time
TimeAccuracy
Accuracy11µs
µs
0.02
0.02Degrees
Degreesat
at60
60Hz
Hz
1.25
Distributed Dynamic State Estimation Implementation
PMU Technology Enables Distributed SE
IED Vendor D
Measurement Layer
i1(t) i2(t)
Burden
Physical Arrangement
Data
Processing
Instrumentation
Cables
Attenuator
FireWall
PMU
Vendor A
SuperCalibrator
Attenuator
v2(t)
Anti-Aliasing
Filters
PMU
Vendor C
Burden
Data Flow
LAN
v1(t)
Relay
Vendor C
LAN
Current
Transformer
v(t)
Potential
Transformer
i(t)
Encoding/Decoding
Cryptography
Phase Conductor
Data/Measurements from all PMUs, Relays, IEDs, Meters,
FDRs, etc are collected via a Local Area Network in a data
concentrator.
The data is used in a dynamic state estimator which provides
the validated and high fidelity dynamic model of the system.
Bad data detection and rejection is achieved because of high
level of redundant measurements at this level.
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1.26
Numerical Results – B-G Plant
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1.27
Transient Stability Monitoring
The dynamic state estimator is utilized to predict the transient stability or instability of a generator. The dynamic
state of the system provides the center of oscillations of the generator swing. From this information the potential
energy of the generator is computed as a generalization of the basic energy function method.
The total energy of the generator can also be trivially computed once the potential energy has been computed.
The total energy is compared to the potential energy of the generator – if the total energy is higher than the peak
(barrier) value of the potential energy this indicates that the generator will lose its synchronism (transient
instability).
It is important to note that this approach is predictive, i.e. it identifies a transient instability before it occurs.
The figures provide visualizations of generator oscillations and the trajectory of the total energy superimposed on
the system potential energy.
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.28
Energy Management Systems
Hierarchy of Scheduling Functions
Level 1: Load Forecasting
Unit Commitment
Emissions Control
Economy Purchases
Level 2: Economic Dispatch
Environmental Dispatch
Economic Interchange Evaluation
Optimal Power Flow
Transfer Capability
Day-Ahead Scheduling
Spot Market Scheduling
Level 3: Automatic Generation Control
- Frequency Control
- Interchange Control
- Transactions Control
- Inadvertent Power Flow Control
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.29
Generating Unit Control Schemes
Schematic Representation
Tramsmission
System
and Load
Prime
Mover
G
Vg
Governor
G(s)
Pg
Tie
Line
f
Exciter
fsched
f
-
+
Vref
+
Σ
+
PSS
D(s)
f
Σ
-
Pg
Σ
Bias
Bf
+
Psched
+
Pg
-
Σ
+
K(s)
Σ
+
f
L(s)
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1.30
Net Interchange Control
G
Area 1
G
Area 3
Vi e jδi
G
G
G
ACE = P
Area 4
G
Area 2
G
Area Control Error (ACE)
ACE = ∆Pint + B∆f
∆Pgi = a i ACE
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G
G
1.31
Economic Scheduling Functions Hierarchical Structure
A
Resource Scheduling
(weeks)
Mid Term Load Forecast
Units out for maintenance
Fuel Management
Weekly hydro energy usage
B
Unit Commitment
(hours/Days)
Short Term Load Forecast
List of committed units
Hourly hydro energy usage
Interchange schedule
C
Economic Dispatch
(minutes)
Security
Dispatch
Economic Base Points
Participation Factors
D
Automatic
Generation Control
(seconds)
Pdesi , i =1,2,...,n
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1.32
Economic Dispatch
G1
• MEASUREMENTS
G2
1
• COST
3
T1
• FORMULATION
T2
• SOLUTION
2
4
L1
Interconnection
Interconnection
L3
L2
5
T1
MW Flow Measurement
MVAR Flow Measurement
kV Measurement
Transformer Tap Measurement
6
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.33
Optimal Power Flow
G1
G2
• MEASUREMENTS
1
3
• STATE
T1
2
T2
• CONTROLS
• FORMULATION
4
L1
Interconnection
Interconnection
• SOLUTION
L3
L2
5
T1
MW Flow Measurement
MVAR Flow Measurement
kV Measurement
Transformer Tap Measurement
6
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.34
SYSTEM
SECURITY
NORMAL and SECURE
System Optimization
(Congestion Management)
Power System Operating
States
D,O
Preventive
Controls
Restorative
Controls
RESTORATIVE
System Security
D,O
Emergency
Controls
EXTREMIS
System Security
Restorative
Controls
NORMAL but
VULNERABLE/INSECURE
Optimization/Security
D,O
Emergency
Controls
Corrective
Controls
EMERGENCY
System Security
D,O
D,O
Transition Due to Disturbances
Transition Due to Control Action
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.35
Energy Management Systems
Hierarchical Structure
System Power
Production and
Control
(SPPC)
Operations
Coordination
Office
(OCO)
Regional
Dispatch
Center
(RDC)
Substation
Power Plant
UCE
Vexc
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Power Plant
Controls
Psched
fsched
ACE
Vsched
1.36
New Challenges: Wind/PV Farm Characteristics
Types 1 and 2
are Not Used for
Large Projects
Types 3 and 4
Limit Fault
Currents to
About 120% of
Nominal Current
Proposed
Proposed Requirements
Requirements –– NERC
NERC PRC-024,
PRC-024, >20
>20 MVA
MVA or
or >75
>75 MVA
MVA
Total
Total
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1.37
Renewables and Uncertainty
Solar is Available During High Price/Cost Hours
Small Storage can provide huge add-on value to solar projects
Better capacity factor than other renewables (70 to 80%)
Wind Availability is Highly Volatile and Patterns May be
Opposite to Grid Needs (i.e. CA)
Large Storage Schemes are needed to coordinate economic
usage of wind energy and to provide add-on value
Very small capacity factor (10 to 25%)
Large Wind Swings
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Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.38
Energy Management Systems: Evolution
Control and Operation of Power Systems
is Driven by
(a) Legislative action
(b) Economics
(c) Technical constraints
The envelop is always moving because of
technological advancements
ERO Focus: Operational Reliability
NSF/ECEDHA Education Workshop
Georgia Tech GLC, Atlanta, Georgia, July 9-12, 2011
1.39
History of Utility Regulatory Legislation
Federal Power Commission
• PUHCA – 1935 (Public Utility Holding Company Act)
Federal Energy Regulatory Commission (1977)
• PURPA – 1978 (Public Utility Regulatory Policies Act)
• Clean Air Act – 1990
• Energy Policy Act – 1992
• Orders 888 & 889 – 1996 (1 OASIS )
• CECA – 1998 (Comprehensive Electricity Competition Act)
• Order 2000
• SMD – Standard Market Design
• US Energy Policy Act, 2005 (provides authority to enforce reliability)
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1.40
Visualization & Animation
University of Illinois/Georgia Tech (PSERC Project)
G e n e ra to r A n im a tio n - U n it C a p a b ility
U n it N a m e
Qg
R o tor
H e ating
Pg
L ow
V o lta ge
S e n s itiv itie s
d P g /d P
d Q g /d P
d V g /d P
0
1
2
3
4
0
1
2
3
4
0
1
2
3
4
Large Scale Systems
Performance - Model Hierarchy
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1.41
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1.42
Energy Management Systems
Information Systems and Standards
OASIS
Open Access Same-Time Information System
UCA
Utility Communication Architecture
ICCP
Inter-Control Center Communications Protocol
CCAPI
Control Center Application Program Interface
CIM
Common Information Model
IEC61850 Evolution of the UCA
C37.118 Synchrophasor Data
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1.43
Active Future Distribution Systems (with distributed energy resources – solar, wind, PHEVs, fuel cells,…).
Smart Grid technologies: Distributed Monitoring, Control, Protection and Operations system. Target Speeds 10
times per second
Functions: (a) Optimal operation of the distribution system under normal operating conditions, (b) Emergency
management in cases of faults and assist the power grid when needed, (c) Assist Voltage recovery, (d) Assist cold
load pickup, (e) Balance Feeder, (f) etc., etc.
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1.44
Evolution, Naxos Island, Greece
June 25, 2011
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1.45