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Middletown-Norwalk Project

Middletown-Norwalk Project. I.3.9 Application Presentation to the NEPOOL Reliability Committee. December 15, 2005. The Middletown–Norwalk Project. Background: Alternatives Technical Analyses and Results Overview of Proposed Plan Applications. Project Need 345-kV Loop Load Generation.

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Middletown-Norwalk Project

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  1. Middletown-Norwalk Project I.3.9 Application Presentation to the NEPOOL Reliability Committee December 15, 2005

  2. The Middletown–Norwalk Project • Background: • Alternatives • Technical Analyses and Results • Overview of Proposed Plan Applications • Project Need • 345-kV Loop • Load • Generation

  3. Project Need • A 345-kV loop has been planned since the 1970’s • The existing system fails to meet national and regional reliability standards • The Project must reliably serve peak demand by: • Improving voltage profiles • Eliminating thermal overloads • Increasing transfer limits • Eliminating generation interdependencies • Increasing short-circuit safety margins

  4. 347 395 North Bloomfield 368 330 Manchester Lake Road 353 Card 310 Frost Bridge Long Mountain Southington Scovill Rock 383 398 352 329 376 362 364 Beseck Haddam Neck Montville 321 348 371 East Devon 387 Plumtree (Bethel) East Devon Millstone East Shore Singer Norwalk Project Need Satisfied with 345-kV Loop (January 2002 ISO-NE Report)

  5. 347 395 North Bloomfield 368 330 Manchester Lake Road 353 Card 310 Frost Bridge Long Mountain Southington Scovill Rock 383 398 352 329 376 362 364 Beseck Haddam Neck Montville 321 348 371 East Devon 387 Plumtree (Bethel) East Devon Millstone East Shore Singer Norwalk Project Need Satisfied with 345-kV Loop (January 2002 ISO-NE Report) Strong source created with integration of Beseck Switching Station

  6. 347 395 North Bloomfield 368 330 Manchester Lake Road 353 Card 310 Frost Bridge Long Mountain Southington Scovill Rock 383 398 352 329 376 362 364 Beseck Haddam Neck Montville 321 348 371 East Devon 387 Plumtree (Bethel) East Devon Millstone East Shore Singer Norwalk Project Need Satisfied with 345-kV Loop (January 2002 ISO-NE Report) Strong source created with integration of Beseck Switching Station At East Devon and Singer additional transmission lines, new autotransformers, and generator reterminations relieve powerflows on the 115-kV system, improve voltage control, and increase short-circuit safety margins.

  7. 347 395 North Bloomfield 368 330 Manchester Lake Road 353 Card 310 Frost Bridge Long Mountain Southington Scovill Rock 383 398 352 329 376 362 364 Beseck Haddam Neck Montville 321 348 371 East Devon 387 Plumtree (Bethel) East Devon Millstone East Shore Singer Norwalk Project Need Satisfied with 345-kV Loop (January 2002 ISO-NE Report) Loop closed through major system hub at Norwalk Strong source created with integration of Beseck Switching Station At East Devon and Singer additional transmission lines, new autotransformers, and generator reterminations relieve powerflows on the 115-kV system, improve voltage control, and increase short-circuit safety margins.

  8. 2575 MW 1300 MW Year SWCT N-S 1990 2544 897 2005 3477 1210 Growth% 37% 35% Load Growth has Outpaced Transmission Capability 347 Available Generation SWCT 2350 MW N-S 450 MW 395 North Bloomfield 368 330 Manchester Lake Road 353 Card 310 Frost Bridge Long Mountain Southington Scovill Rock 383 398 352 329 376 SWCT 362 364 Beseck Haddam Neck Montville 321 Plumtree (Bethel) 348 371 N-S East Devon 387 East Devon Millstone East Shore Singer Norwalk Norwalk Area Load

  9. The Middletown–Norwalk Project • Background: • Alternatives • Technical Analyses and Results • Overview of Proposed Plan Applications • Project Need • 345-kV Loop • Load • Generation

  10. System Configurations Considered • Real-time dynamic ratings • Upgrading 115-kV lines to 161-kV • 115-kV line additions and conductor upgrades • 230-kV line additions • Flexible AC Transmission System (FACTS) devices • HVDC

  11. Limitations of other AC Configurations • Every transmission corridor in SWCT impacted • Short-circuit constraints not resolved • Requires significant replacement/rebuilding of equipment • Significant outages required to perform construction • Limited increase in transfer capability • Did not provide long-term system flexibility • Does not allow significant generation interconnections

  12. Limitations of HVDC • Studied extensively during the CSC hearings by ABB • Multiple converter designs raised control system concerns • Does not resolve short-circuit concerns in the area • New converter required when: • Expanding transmission system • Interconnecting new generation

  13. The Middletown–Norwalk Project • Background: • Alternatives • Technical Analyses and Results • Overview of Proposed Plan Applications • Project Need • 345-kV Loop • Load • Generation

  14. A Thorough Steady-State Analysis was Performed • Recommended for approval by the TTF on Sept. 19, 2005 • Forecasted 2009 summer peak load from 2004 CELT Report • Four stressed dispatch variations • 52 powerflow cases • Pre-project and post-project systems • 48 peak load cases • 4 light load cases • Three NY to NE transfer levels (+700 MW, 0 MW, and -700 MW) • Approximately 500 contingencies simulated

  15. Steady-State N-2 & Transfer Limit Analyses • Nine first-contingency cases simulating major line outages in SWCT • Post-contingent overloads relieved by source reduction • All necessary reductions were less than 1200 MW limit • Simultaneous transfer limit analysis: • N-S transfer limit increased approximately 450 MW • SWCT transfer limit increased approximately 1600 MW • No adverse impact on the existing NY-NE limits

  16. A Thorough Transient Stability Analysis was Performed • Recommended for approval by the STF on November 9, 2005 • Forecasted 2009 summer peak load from 2004 CELT Report • Nine light load cases • Three peak load cases • Three NY to NE transfer levels (+1200 MW, 0 MW, and -1200 MW) • Approximately 450 contingencies tested • Short-circuit analysis included

  17. Recommendations from Transient Stability Testing • Install direct transfer trip scheme on 1389 line • BPS Testing identified 9 substations requiring reclassification • Elmwest 115-kV Substation (UI) dependent upon NRI • Flax Hill 115-kV Substation (CL&P) independent of NRI • Eight existing CL&P circuit breakers over-dutied and will be replaced • Six 115-kV circuit breakers • Two 345-kV circuit breakers • Delta P testing produced values less than 20%

  18. Transient Network Analysis • Transient network analysis (TNA) detailed in the “ROC Report” • ROC – Reliability and Operability Committee • ROC Report Issued by NU, UI , and ISO-NE on December 20, 2004 • TNA investigated the potential for temporary overvoltages (TOVs) • Design detailed in ROC Report modeled in PPA studies • Identified need to replace some SWCT “T” and “D” surge arresters

  19. TNA – Conservative Assumptions • Applied a 0.25 pu voltage margin on results • Starting voltages targeted 1.05 pu • Shunt capacitor dispatch maximized • Shunt reactor dispatch minimized • Load modeling • Tested load levels at 30, 40, 50, and 70% of peak • Tested multiple load composition models • Minimum generator dispatch • Bridgeport RESCO on in SWCT (~60 MW) • Millstone 3 on in CT • Tested with reduced “outside world” system strength

  20. The Middletown–Norwalk Project • Background: • Alternatives • Technical Analyses and Results • Overview of Proposed Plan Applications • Project Need • 345-kV Loop • Load • Generation

  21. The Project: 345-kV Elements • New Stations • Beseck, East Devon, and Singer • Reconfigured Stations • Scovill Rock and Norwalk • Construction of new lines between: • Beseck to East Devon – overhead • East Devon to Singer – two parallel underground cables • Singer to Norwalk – two parallel underground cables • Reconfiguration/extension of two existing lines

  22. The Project: Other Elements • Various 115-kV line rebuilds/reconductors • Reclassify several substations as BPS facilities • Replace over-dutied circuit breakers • Install new 115-kV circuit breakers • SPS modification

  23. Scovill Rock • Expand the Scovill Rock 345-kV Switching Station • Reconfigure the 348 Line between Millstone and Southington • Create the 3010 Line between Scovill Rock and Southington • Terminate 353 Line in a separate bay • Install 345-kV circuit breaker to reterminate 387 Line • Modify Cross Sound Cable Line End Open SPS

  24. Beseck • Construct 345-kV Switching Station at Beseck Junction • Terminate the Existing 348 Line at Beseck • Create the 348 Line from Beseck to Millstone • Loop the 362 Line into Beseck • Create the 362 Line from Meriden Power (Southington) to Beseck • Create the 3198 Line from Haddam Neck to Beseck • Construct the 3029 Line from East Devon to Beseck • Construct Beseck as NPCC BPS Facility

  25. East Devon 345-kV & 115-kV and Devon 115-kV • East Devon: • Build a 345-kV Substation at East Devon • Build a 115-kV Substation at East Devon • Terminate the 345-kV 3029 line from Beseck • Terminate two parallel 345-kV cables to Singer • Install an 345/115-kV autotransformer • Create two 115-kV Circuits (East Devon to Devon) • Reterminate Milford Power from Devon to East Devon 115-kV • Devon 115-kV: • Install an additional 115-kV circuit breaker • Permanently open the 1480 Bus Tie

  26. Singer 345-kV and Pequonnock 115-kV • Construct Singer Substation • Terminate two 345-kV underground cables from East Devon • Terminate two 345-kV underground cables to Norwalk • Install four 345-kV variable shunt reactors switched with 345-kV circuit breakers • Install two 115-kV circuit breakers at Pequonnock 115-kV • Install two 345/115-kV autotransformers • Modify Bridgeport Energy Interconnection • Create Pequonnock Interconnection

  27. Norwalk • Expand the 345-kV substation at Norwalk • Install a second 345/115-kV autotransformer • Terminate two parallel 345-kV cables from Singer • Install two 345-kV variable shunt reactors switched with 345-kV circuit switchers • Install direct transfer trip scheme on 1389 Line (Norwalk to Flax Hill)

  28. Rebuild/Reconductor Various 115-kV “T” Lines • Rebuild/reconductor: • Remove 1690 Line between Cook Hill Junction and Devon • 1466 Line • 1570 Line • 1575 Line • 1610 Line • 1640 Line • 1655 Line • 1685 Line • 1780 & 1790 Lines • 1975 Line

  29. Other Elements of Project • Replace the 138/115-kV autotransformer at Norwalk Harbor Substation • Reclassify nine existing substations as NPCC BPS facilities • Baird, Bridgeport RESCO, Broadway, Devon Tie, Elmwest, Flax Hill, Mill River, Water Street, West River • Replace over-dutied circuit breakers • Replace six 115-kV circuit breakers • Five at Glenbrook Substation • One at Southington Substation • Replace two 345-kV circuit breakers at Millstone Substation • Install two 115-kV circuit breakers at Elmwest Substation

  30. Conclusion Based on the technical analyses conducted in support of this Project, NU and UI believe the Project will not have a significant adverse impact on the stability, reliability or operating characteristics of the transmission system.

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