Transcript Greatly Simplified

TRANSMISSION CONSTRAINTS
KENNETH A. DONOHOO, P.E.
Manager of System Planning,
Technical Operations
[email protected]
TERMS
•
•
•
•
•
VOLTAGE
CURRENT
POWER
FREQUENCY
CONTINGENCY
volts
amps
watts
hertz
outage
pressure
flow
volts x amps
cycles/sec
out of service
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ELECTRICITY
CHARACTERISTICS
Travels at the speed of light
Cannot be easily stored
Cannot be fully “routed”
Line flows not easily
changed
• Network must be
continuously connected to
function correctly
• Supplied immediately upon
demand by customer
•
•
•
•
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BUT IT’S NOT LIKE...
• The natural gas pipeline
system
• The telephone system
• The water system
• The transportation system
IT CAN’T BE EASILY ROUTED!
Power flow is based upon
Physical Laws not Contracts
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ORIGINAL PURPOSE OF
TRANSMISSION
• Connect generators to each other and to the
distribution system
• Contingencies (outages) and economic
dispatch
• Connect utilities to each other
• Security
• Interchange
• Built to serve known customers (loads)
within utilities’ own territory, with relatively
weak inter-utility links.
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TRANSMISSION
CONSTRAINTS
• Function of the Impedance And Voltage Of Network
• Thermal Limits
• Heating of Conductor, Transformer or Facility
• Dependent on weather
• Longer Term - 10 to 40 minutes
• Voltage Limits/Stability
• Reactive Problems
• Very Short Time Frame
• Voltage Collapse
• Unit Stability Limits
• Angular & Generation Unit Stability
• Very Short Time Frame
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DYNAMIC
UNIT
STABILITY
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PARALLEL PATH
Ckt 3
Ckt 2
A
PRIMARY PATH
Ckt 1
B
Ckt 4
Ckt 8
PARALLEL PATH
Ckt 6
Ckt 9
Ckt 5
C
PARALLEL PATH
D
Ckt 7
Transaction From A to B
A is Exporting, B is Importing
Power Flows on Primary Paths as
well as ALL the Parallel Paths
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PARALLEL PATH
Ckt 3
Ckt 2
A
PRIMARY PATH
Ckt 1
B
Ckt 4
Ckt 8
PARALLEL PATH
Ckt 6
Ckt 9
Ckt 5
AS THE POWER FLOW INCREASES, FLOWS ON PRIMARY PATHS AS WELL AS THE
PARALLEL PATHS INCREASE.
PARALLEL PATH
D
C
THE TRANSFER LIMIT (CONSTRAINT) IS REACHED WHEN ANY ONE OF THE
Ckt 7
FOLLOWING CONDITIONS IS REACHED:
•FLOW ON CIRCUIT WOULD BE AT THE LIMIT FOR POST-CONTINGENCY LOADING
•VOLTAGE ON A BUS WOULD BE AT MINIMUM POST-CONTINGENCY VALUE
•SYSTEM REACHES A STATE OF VOLTAGE INSTABILITY LEADING TO COLLAPSE
•SYSTEM IS NOT VOLTAGE STABLE IF A CONTINGENCY WERE TO OCCUR
•SYSTEM IS NOT DYNAMICALLY STABLE IF A DISTURBANCE WERE TO OCCUR
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CALCULATION EXAMPLE
Greatly Simplified
PARALLEL PATH
CONTINGENCY (OUTAGE)
Ckt 3
Ckt 2
X
A
PRIMARY PATH
Ckt 1
B
Ckt 4
Ckt 8
LIMITING EQUIPMENT
PARALLEL PATH
Ckt 6
Ckt 9
Ckt 5
PARALLEL PATH
Power Flow From A to B
C
A is Exporting, B is Importing
Contingency on Circuit 2
Increase Generation in A
Decrease Generation in B
Until Limit Reached on Circuit 9
Net Change in Generation is Transfer Limit
D
Ckt 7
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CALCULATION EXAMPLE
Greatly Simplified
PARALLEL PATH
CONTINGENCY (OUTAGE)
Ckt 3
Ckt 2
X
A
PRIMARY PATH
Ckt 1
B
Ckt 4
Ckt 8
LIMITING EQUIPMENT
PARALLEL PATH
Ckt 6
Ckt 9
Rating on Circuit 9
May Also Limit Transfers
From A to C
and A to D
Ckt 5
C
PARALLEL PATH
D
Ckt 7
Simultaneous Flows From Any Area
May Contribute to Flow on Circuit 9
ACTUAL CALCULATIONS INCLUDE MANY
MORE CIRCUITS & EQUIPMENT
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CONSIDERATIONS
• TRANSMISSION CONSTRAINTS
• Complicates System Security Management
• Leads to Economic Inefficiencies
• Creates Captive Markets
• Reduces Liquidity of the Market
• Creates “Must Run” Generation
• Increased Utilization of Inefficient Units
• Reduced Utilization of Efficient Units
• Confers Market Power to Dominant Supplier in a
Constrained Area
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CONSIDERATIONS
• NEW TRANSMISSION
• Maintains Reliable Service to Load
• Allows New Generation to be Fully Integrated
into the Grid
• Provides for Additional Competition
• Promotes Lower Energy Prices
• Supports a Liquid Competitive Market
• Allows Greater Access to Renewable Generation
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MONTICELLO-FARMERSVILLE
345 kV CIRCUIT
LIMESTONE-WATERMILL
345 kV DCKT
AUSTROP-LOST
PINES-FPP 345
kV CIRCUIT
LYTTON-HOLMANFPP 345 kV
CIRCUIT
NEW MAJOR TRANSMISSION
FOR 2001 SUMMER
MILITARY HIGHWAY
STATCOM +/- 150 MVAR
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MAJOR TRANSMISSION
PROJECTS UNDERWAY
GRAHAM – JACKSBORO 345 kV LINE
CCN FILED BY JUNE 2001
IN SERVICE DEC 2002
MORGAN CREEK–SAN ANGELO–
COMANCHE SWITCH 345 kV LINE
CCN JUNE 2001
IN SERVICE DEC 2002
PARIS-ANNA 345 kV
IN SERVICE DEC 2005
FARMERSVILLE
-ANNA 345 kV
CCN JANUARY 2001
IN SERVICE DEC 2002
VENUS LIGGETT 345 kV
IN SERVICE DEC 2004
SAN MIGUEL–PAWNEE 345 kV LINE
CCN NOVEMBER 2000
IN SERVICE MAY 2002
RIO GRANDE VALLEY SERIES
CAPACITOR COMPENSATION
IN SERVICE SEPTEMBER 2001
HOUSTON AREA
UPGRADES
COLETO CREEK–PAWNEE
345 kV LINE
CCN DECEMBER 2000
IN SERVICE MAY 2002
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PEAK DEMAND
Year
ERCOT Coincident Hourly
Peak Demand MW
Annual
Growth
1994
43,588
--
1995
46,668
7.07%
1996
47,683
2.17%
1997
50,150
5.17%
1998
53,689
7.06%
1999
54,849*
2.16%
2000
57,606
5.03%
Average Six Year Compound
Growth
4.85%
*This value would have been greater if there had been no interruptible load curtailments at the time.
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FUTURE GENERATION
CAPACITY RESERVES
OFFICIAL MARGINS
Based on System Planning Technical Operations forecast.
Assumes all generation capacity is available during peak conditions.
Only includes future generation plants that have an
executed/completed interconnect agreement with an ERCOT TSP.
Does not include DC Tie Capacity or generation plants that can switch
between regions.
Does not include wind generation capacity.
Includes Serving Interruptible Loads
SUMMER Percent Reserve Margin
Year 2002
2003
2004
2005
2006
22.5% 21.7% 18.5% 14.9% 11.4%
WINTER Percent Reserve Margin
Year 2002/03 2003/04 2004/05 2005/06 2006/07
58.3%
64.9%
65.5%
61.5%
57.5%
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ERCOT
TEAMWORK
&
ATTITUDE
GOES A
LONG WAY
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QUESTIONS
FOR MORE DETAILS AND ADDITIONAL SYSTEM DATA
VISIT THE SYSTEM PLANNING TECHNICAL OPERATIONS
WEBSITE AT:
ftp://ftp.ercot.com/systemplanning/system_planning_department.htm
9/13/2001