middletown-norwalk project

Middletown-Norwalk ProjectMiddletown-Norwalk Project

December 15, 2005

I.3.9 Application PresentationI.3.9 Application Presentationto theto theNEPOOL Reliability CommitteeNEPOOL Reliability Committee

2

The Middletown–Norwalk Project

Background:

Alternatives

Technical Analyses and Results

Overview of Proposed Plan Applications

Project Need345-kV LoopLoadGeneration

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

East DevonPlumtree(Bethel)

Scovill Rock

Manchester

SouthingtonFrost Bridge

Montville

Card

Lake Road

Haddam Neck

Beseck

Millstone

East Devon

Singer

Norwalk

Long Mountain

East Shore

398

321

329

395

362

348

364

371387

347

352376

353310

383

368North Bloomfield 330

Project Need Satisfied with 345-kV Loop

(January 2002 ISO-NE Report)

5


Scovill Rock

Manchester


Montville

Card

Lake Road

Haddam Neck

Beseck

Millstone

East Devon

Singer

Norwalk

Long Mountain

East Shore

398

321

329

395

362

348

364

371387

347

352376

353310

383




Strong source created with integration of Beseck Switching Station

6


Scovill Rock

Manchester


Montville

Card

Lake Road

Haddam Neck

Beseck

Millstone

East Devon

Singer

Norwalk

Long Mountain

East Shore

398

321

329

395

362

348

364

371387

347

352376

353310

383




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


Scovill Rock

Manchester


Montville

Card

Lake Road

Haddam Neck

Beseck

Millstone

East Devon

Singer

Norwalk

Long Mountain

East Shore

398

321

329

395

362

348

364

371387

347

352376

353310

383



Loop closed through major system hub at Norwalk


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

East Devon

Plumtree(Bethel)

Scovill Rock

Manchester


Montville

Card

Lake Road

Haddam Neck

Beseck

Millstone

East Devon

Singer

Norwalk

Long Mountain

East Shore

398

321

329

395

362

348

364

371387

347

352376

353310

383


Load Growth has Outpaced Transmission Capability

Norwalk

SWCT

N-S

Available Generation

SWCT 2350 MW

N-S 450 MW

Available Generation

SWCT 2350 MW

N-S 450 MW

2575 MW

1300 MW

Area LoadSWCT N-S

1990 2544 8972005 3477 1210

Growth% 37% 35%

Year

9


Background:

Alternatives




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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

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

Limitations of other AC Configurations

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


Background:

Alternatives




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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 casesPre-project and post-project systems48 peak load cases4 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

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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 ReportNine 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

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Recommendations from Transient Stability Testing

Install direct transfer trip scheme on 1389 line

BPS Testing identified 9 substations requiring reclassificationElmwest 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

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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 modelingTested load levels at 30, 40, 50, and 70% of peak

Tested multiple load composition models

Minimum generator dispatchBridgeport RESCO on in SWCT (~60 MW)

Millstone 3 on in CT

Tested with reduced “outside world” system strength

20


Background:

Alternatives




21

The Project: 345-kV Elements

New StationsBeseck, East Devon, and Singer

Reconfigured StationsScovill 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 SouthingtonCreate 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 BeseckCreate the 348 Line from Beseck to Millstone

Loop the 362 Line into BeseckCreate 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 autotransformersModify 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 Line1570 Line1575 Line1610 Line1640 Line1655 Line1685 Line1780 & 1790 Lines1975 Line

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Other Elements of Project

Replace the 138/115-kV autotransformer at Norwalk Harbor Substation

Reclassify nine existing substations as NPCC BPS facilitiesBaird, 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

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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.

middletown-norwalk project

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