ERCOT LTSA

RPG 10/17/08

2

Introduction

• Objective

• Year of study

• General procedure

– Transmission reliability

– Economic analysis

• Assumptions

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Reliability Study Model Development

• Vintage• Load

– Summer peak– 90-10 forecast (83,500MW; 9,200MW flat)– Growth rates

• Future transmission and generation projects– Planned generation with I.A. as at July 31,

2008

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Reliability Study Approach

• Sub-area/Region-based

– North East

– Houston

– South Central

– Valley

• Transmission network reliability

– Applicable generation

– Bulk power needs

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Sub-area details

• Northeast sub-area– Major load centers: DFW metro; IH-20, IH-35, IH-45

corridors, Brazos county– 31,600MW load– Generation resources (33,000MW)

• 10,400MW coal, 800MW wind, 130MW hydro, Comanche nuclear plants (2,350MW), Kiamichi, 600MW DC tie.

– Key future projects• CREZ: West Krum – Anna, Willow Creek – Hicks,

Navarro – Central C, Sam Switch – Central C, etc.• Lufkin – Nacogdoches 345kV line.• Bosque Power Expansion, Oak Grove.

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Sub-area details

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Sub-area details

• Houston sub-area– Major load centers: Houston metro, Galveston,

Freeport.– 18,450MW load– 18,750MW generation

• 2,500MW coal, 0 wind, 0 hydro– Key future projects

• Rothwood• Zenith• Kuykendahl• Cedar Bayou 4

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Sub-area details

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Sub-area details

• South-Central sub-area

– 7,200MW load

– 9,500MW generation

• 6,000MW coal, 250MW hydro

– Key future projects

• Salado – Clear Springs double ckt 345kV

• CREZ: Kendall – Gillespie - Newton

• Sandow 5

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Sub-area details

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Sub-area details

• Valley sub-area– Major load centers: Corpus Christi, Laredo,

Brownsville-McAllen– 5,350MW [6,600MW] load– 5,775MW [11,050MW] generation

• 4,200MW gas; 550MW wind, 100MW hydro, [STP nuclear]

– Key future projects• Miguel – Lobo 345kV• Nueces Bay #7 re-powering

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Sub-area details

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Sub-area details

• Western ERCOT sub-area

– Major load centers: Abilene, Odessa, Wichita Falls.

– 4,100 MW load

– 13,700MW generation

• 220MW DC tie, 4,500MW gas; 630MW coal

– Key future projects

• CREZ transmission only

• Reactive compensation

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Reliability Criteria - Voltage

Entity Normal (or pre-contingency) Emergency (or post-contingency)

AEP 0.95pu 0.90pu

AEN 0.95pu 0.90pu

CNP 0.95pu

1.01pu (STP)

0.95pu (Category B)

0.92pu (Category C)

1.01pu (STP)

CPS 0.95pu 0.93pu (probable disturbances)

0.90pu (extreme disturbances)

TNMP .95pu .90pu

TXU

0.95pu (345-kV buses)

0.94pu (138-kV and 69-kV buses)

0.99pu (Comanche Peak nuclear)

-5% ?voltage from normal (345-kV)

-5% ?voltage from normal (69 & 138)

0.98pu (Comanche Peak nuclear)

ERCOT 0.95pu 0.95pu

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Reliability Analysis

• AC contingency-based• Generation dispatches (age, size, location,

influence, DC ties, VFT)– Outages/unavailability– Age; size; location.

• Problem categories– Wide area bulk power transfer– Local area regional problems

• No assessment of adequacy (LOLE, location, type) of available generation

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Reliability Analysis

• Dispatch scenarios– Generation deficient area

• 10% unavailability to assess import sensitivity

– Generation surplus area • 10% unavailability modeled using target

gens– Hydro and wind resources not included

• Monitor interface loading and voltage sensitivity

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Reliability Findings

• Northeast sub-area

Dispatch (unavailable gen) Net area

importNotes

1. All area generation on, DC import: 600MW.

-300MW

Local area import constraints for Airport area, Denton, McKinney, Lewisville, Sherman, Waco, Tyler, Glen Rose. Elkton, Fore Grove Shambger

345kV low voltages. 345/138kV autos.

2. RW Miller (75), N. TX (75), Ray O (185), Valley (1050), Mont (580)

1700MW(1) + area bulk import constraints on Alliance-Hicks,

TriCrnr-SgvlSS, Venus-Webb, Trinidad-Richland 345kV corridors.

3. Bosq (530), Monticel. (800), Forney (900).

2200MWSimilar to findings for (2). Elm Mott and

Nacogdoches 345kV low voltages.

4. Johnsn, N. TX, (290), Wise (650), Wf Hollw, DCordva (1490), Hndly (390).

2500MW No Trinidad-Richland bulk area import constraint.

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Reliability Findings

• Houston sub-area

Dispatch (unavailable gen) Net area

importNotes

1. All area generation on

5200MW

THW auto ‘A1’, Houston import limit (Tomball/Rothwd area 138kV sys.), PHRob and

Fairmont area 138kV sys., widespread north Houston 345kV under-voltages.

2. Deer Park EC (970),

6200MW(1) + W. Houst/Richmond imp. WAP-Bellair 345kV corridor import limitation. 345kV and 138kV low

voltages across entire area.

3. THW (390), WAP (800).

6400MW(2) + Singleton-Zenith Houston import thermal constraint. 345kV post-con voltages as low as

0.91pu

4. WAP (165), Sam Bert (175), Shell (70), Cedar Byu (745) 6400MW

Similar to (3). 345kV post-con voltages as low as 0.91pu

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Reliability Findings

• South-central sub-areaDispatch (unavailable gen) Net area

importNotes

1. All area generation on, high Houston, Matag.

n/aSandow export limitation. Ferguson gen export. Brenham/ Glidden import limits. Voltages OK.

2. All area generation on, high DFW, Western

n/aSandow export. Brenham/ Glidden import. Ferguson area. STP voltage violation due to high N-S transfer.

3. Leon Ck. (95), Fayette (600), High Houston.

n/aSandow export. Brenham/ Glidden import. Ferguson

area 138kV line overloads. Voltages OK.

4. JT Deely (405), Leon Ck. (95), JKSp (560), WBTtle. (150) n/a

San Antonio import (Skyline-Marion 345kV, Skyline-Hill City 345kV). Sandow-Elgin overloads. Voltages

OK.

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Reliability Findings

• Valley sub-area

Dispatch (unavailable gen)

Net Valley import

Notes

1. All area generation on; no CFE import

1726MWCorpus Christi, Edinburg, Port Lavaca area import

limits. Voltages OK

2. Barney Davis (680MW) 2405MW

Valley import constraints: 138kV line overloads; voltage collapse from Miguel-Lobo 345kV

contingency.

3. Silas Ray (35MW), Nueces (330MW), Magic Valley (680MW).

2752MWValley import: 345kVand 138kV line overloads; voltage collapse caused by Miguel-Lobo 345kV

contingency., among others

4. Silas Ray (35MW), Magic Valley (216MW)

1900MWValley import: 138kV line loading; voltage collapse

from Miguel-Lobo 345kV conting.

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Reliability Findings

• Western ERCOT sub-area

– No analysis performed. CREZ analysis deemed adequate until further clarity is established.

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Next Steps

• Align findings with results from economic analysis

• Discuss fixes with Transmission Owners to develop solution alternatives

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•The economic viability of different projects are being evaluated using a base case and several change cases:

– High load case

– High natural gas price case ($11/MMBtu)

– Two cases for different levels of expansion/construction of new nuclear plants

– High wind case (in excess of CREZ scenario 2 wind)

– New technologies (solar, energy storage, plug-in hybrids)

– Carbon tax

Economic analysis