middletown-norwalk project
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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
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)
Strong source created with integration of Beseck Switching Station
6
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)
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.
Strong source created with integration of Beseck Switching Station
7
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
Loop closed through major system hub at Norwalk
(January 2002 ISO-NE Report)
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.
Strong source created with integration of Beseck Switching Station
8
East Devon
Plumtree(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
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
The Middletown–Norwalk Project
Background:
Alternatives
Technical Analyses and Results
Overview of Proposed Plan Applications
Project Need345-kV LoopLoadGeneration
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
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
The Middletown–Norwalk Project
Background:
Alternatives
Technical Analyses and Results
Overview of Proposed Plan Applications
Project Need345-kV LoopLoadGeneration
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 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
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 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
17
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
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 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
The Middletown–Norwalk Project
Background:
Alternatives
Technical Analyses and Results
Overview of Proposed Plan Applications
Project Need345-kV LoopLoadGeneration
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
29
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
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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