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TRANSMISSION CONSTRAINTS. KENNETH A. DONOHOO, P.E. Manager of System Planning, Technical Operations [email protected]. TERMS. VOLTAGEvoltspressure CURRENTampsflow POWERwattsvolts x amps FREQUENCYhertzcycles/sec CONTINGENCYoutageout of service. - PowerPoint PPT Presentation
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TRANSMISSION CONSTRAINTS
KENNETH A. DONOHOO, P.E.
Manager of System Planning, Technical
9/13/2001
TERMS
• VOLTAGE volts pressure• CURRENT amps flow• POWER watts volts x amps• FREQUENCY hertz cycles/sec• CONTINGENCY outage out of service
9/13/2001
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
9/13/2001
BUT IT’S NOT LIKE...
• The natural gas pipeline system
• The telephone system• The water system• The transportation
systemIT CAN’T BE EASILY ROUTED!
Power flow is based uponPhysical Laws not Contracts
9/13/2001
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.
9/13/2001
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
9/13/2001
DYNAMIC UNIT
STABILITY
9/13/2001
Greatly Simplified
AB
Transaction From A to BA is Exporting, B is ImportingPower Flows on Primary Paths as well as ALL the Parallel Paths
C D
Ckt 1
Ckt 2
Ckt 3
Ckt 4
Ckt 5
Ckt 6
Ckt 7
Ckt 9
Ckt 8
PRIMARY PATH
PARALLEL PATH
PARALLEL PATH
PARALLEL PATH
9/13/2001
Greatly Simplified
AB
C D
Ckt 1
Ckt 2
Ckt 3
Ckt 4
Ckt 5
Ckt 6
Ckt 7
Ckt 9
Ckt 8
PRIMARY PATH
PARALLEL PATH
PARALLEL PATH
PARALLEL PATH
AS THE POWER FLOW INCREASES, FLOWS ON PRIMARY PATHS AS WELL AS THE PARALLEL PATHS INCREASE.
THE TRANSFER LIMIT (CONSTRAINT) IS REACHED WHEN ANY ONE OF THE 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
9/13/2001
Power Flow From A to BA is Exporting, B is ImportingContingency on Circuit 2Increase Generation in ADecrease Generation in BUntil Limit Reached on Circuit 9Net Change in Generation is Transfer Limit
CALCULATION EXAMPLEGreatly Simplified
AB
C D
Ckt 1
Ckt 2
Ckt 3
Ckt 4
Ckt 5
Ckt 6
Ckt 7
Ckt 9
Ckt 8
PRIMARY PATH
PARALLEL PATH
PARALLEL PATH
PARALLEL PATH
CONTINGENCY (OUTAGE)
X
LIMITING EQUIPMENT
9/13/2001
CALCULATION EXAMPLEGreatly Simplified
AB
C D
Ckt 1
Ckt 2
Ckt 3
Ckt 4
Ckt 5
Ckt 6
Ckt 7
Ckt 9
Ckt 8
PRIMARY PATH
PARALLEL PATH
PARALLEL PATH
PARALLEL PATH
CONTINGENCY (OUTAGE)
X
LIMITING EQUIPMENT
Rating on Circuit 9May Also Limit TransfersFrom A to Cand A to D
Simultaneous Flows From Any AreaMay Contribute to Flow on Circuit 9
ACTUAL CALCULATIONS INCLUDE MANY MORE CIRCUITS & EQUIPMENT
9/13/2001
• 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
CONSIDERATIONS
9/13/2001
• 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
CONSIDERATIONS
9/13/2001
MONTICELLO-FARMERSVILLE 345 kV
CIRCUIT
AUSTROP-LOST PINES-FPP 345 kV
CIRCUIT
LYTTON-HOLMAN-FPP
345 kV CIRCUIT
LIMESTONE-WATERMILL 345 kV
DCKT
MILITARY HIGHWAY STATCOM +/- 150
MVAR
NEW MAJOR TRANSMISSIONFOR 2001 SUMMER
9/13/2001
COLETO CREEK–PAWNEE 345 kV LINECCN DECEMBER 2000IN SERVICE MAY 2002
SAN MIGUEL–PAWNEE 345 kV LINE
CCN NOVEMBER 2000IN SERVICE MAY 2002
FARMERSVILLE-ANNA 345 kV
CCN JANUARY 2001IN SERVICE DEC
2002
MORGAN CREEK–SAN ANGELO–COMANCHE SWITCH 345 kV
LINECCN JUNE 2001
IN SERVICE DEC 2002
GRAHAM – JACKSBORO 345 kV LINECCN FILED BY JUNE 2001
IN SERVICE DEC 2002
RIO GRANDE VALLEY SERIES CAPACITOR COMPENSATIONIN SERVICE SEPTEMBER 2001
MAJOR TRANSMISSIONPROJECTS UNDERWAY
HOUSTON AREA
UPGRADES
PARIS-ANNA 345 kVIN SERVICE DEC 2005
VENUS LIGGETT 345 kV
IN SERVICE DEC 2004
9/13/2001
PEAK DEMAND
YearERCOT Coincident Hourly
Peak Demand MWAnnual 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.
9/13/2001
FUTURE GENERATION
CAPACITY RESERVESOFFICIAL 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%
9/13/2001
ERCOT TEAMWORK
&
ATTITUDE GOES A
LONG WAY
9/13/2001
QUESTIONSFOR MORE DETAILS AND ADDITIONAL SYSTEM DATA
VISIT THE SYSTEM PLANNING TECHNICAL OPERATIONSWEBSITE AT:
ftp://ftp.ercot.com/systemplanning/system_planning_department.htm