ISTEP Update Transmission Planning Summit August 11, 2009 Crown Plaza Hotel New Orleans, LA

ISTEP 2009 Projects

4 1.South Central Arkansas/Northeast Louisiana constraint – to address North to South flows 2.Central Arkansas constraint – to address South to North flows 3.Lake Charles 230 kV Loop (relieve 138 kV Flowgate NELLC_NELLCB) 4.Baton Rouge/South MS constraint – to address Central to South flows 5.Jackson Area Today’s presentation focuses on preliminary results for projects 1 and 2 ISTEP 2009

ISTEP Projects 1 & 2 – ISSUES

6 Project 1 & 2 Issues 2008 Monitored Flowgate Curtailments FGDescriptionNon-Firm MWhFirm MWh 1Sheridan – Mabelvale 500 kV FTLO White Bluff – Keo 500 kV (SHRMAB_KEO) 18,7294,324 2Sheridan – El Dorado 500 kV FTLO Etta – McNeil 500 kV (SHRELD_HSPET) 73,01025,199 3White Bluff – Sheridan 500 kV FTLO Mabelvale – Sheridan 500kV (WHBSHE_MABEL) 32,0840 4Mabelvale – Sheridan 500 kV FTLO White Bluff – Sheridan 500kV (MABSH_WBSH) 14,0960 5White Bluff – Keo 500 kV FTLO Sheridan – Mabelvale 500 FTLO (WBKEO_SHMAB) 4430

7 Project 1 & 2 Issues 2008 Monitored Flowgates - Locations

8 Replicate the flowgate issues that have occurred in 2008 and determine solutions to mitigate them Issue not apparent in long-term models Determine system operation during a known TLR event Model the system as shown during the event using a day-ahead operational model Should replicate the flowgate overload issues Determine system changes to eliminate flowgate issues Projects 1 & 2 Method of Preliminary Study

Project 1 South Central AR / Northeast LA Constraint

10 North – South generation bias observed Affected Flowgates Sheridan – Eldorado FTLO Etta – McNeil (Flowgate 2) WhiteBluff-Sheridan FTLO Mabelvale-Sheridan (Flowgate 3) Mabelvale-Sheridan FTLO White Bluff-Sheridan (Flowgate 4) Flowgate issues occur during daily off-peak periods of the peak loading season Project 1: Southcentral AR / Northeast LA Constraint Background

11 Used July 6, 2008 Operational day-ahead model TLR curtailment called July 6, 2am WhiteBluff-Sheridan FTLO Mabelvale-Sheridan (Flowgate 3) Actual Generation / Load / Transactions used in the model simulation Project 1: South Central AR / Northeast LA Constraint Modeling and Assumptions

12 South Central AR / Northeast LA Constraint Base Flows Base flows for 500kV are North to South

13 South Central AR / Northeast LA Constraint SHRMAB_KEO (Flowgate 1)

14 Southcentral AR / Northeast LA Constraint SHRELD_HSPET (Flowgate 2)

15 South Central AR / Northeast LA Constraint WHBSHE_MABEL (FG3), WBKEO_SHMAB (FG5)

16 South Central AR / Northeast LA Constraint MABSH_WBSH (Flowgate 4)

17 Southcentral AR / Northeast LA Constraint Upgrades in the Change Case Terminal Limiting Equipment Upgrades: Sheridan-Eldorado 500kV from 1732 to 2546 MVA (FG2) White Bluff – Sheridan 500 kV from 1732 to 2546 MVA (FG3) Mabelvale – Sheridan500 kV from 1732 to 2546 MVA (FG4)

18 South Central AR / Northeast LA Constraint Change Case Base Flows

19 South Central AR / Northeast LA Constraint Change Case SHRMAB_KEO (Flowgate 1)

20 Southcentral AR / Northeast LA Constraint Change Case SHRELD_HSPET (Flowgate 2)

21 South Central AR / Northeast LA Constraint Change Case WHBSHE_MABEL (FG3), WBKEO_SHMAB (FG5)

22 South Central AR / Northeast LA Constraint Change Case MABSH_WBSH (Flowgate 4)

Project 2 Central Arkansas Constraint

24 Generation Outlet Issue South to North Flows Observed Affected Flowgates Sheridan – Mabelvale FTLO White Bluff – Keo (FG1) Flowgate issue occurs during daily on-peak periods of off-peak load season Project 2. Central AR Constraint Background 4

25 Used Dec 21, 2008 Operational day-ahead model TLR curtailment called Dec 21, 6pm Sheridan – Mabelvale FTLO White Bluff – Keo (Flowgate 1) Actual Generation / Load / Transactions used in the model simulation Project 2. Central AR Constraint Modeling and Assumptions

26 Central AR Constraint Base Flows Base flows for 500kV are South to North

27 Central AR Constraint SHRMAB_WBKEO (Flowgate 1)

28 Central AR Constraint SHRELD_HSPET (Flowgate 2)

29 Central AR Constraint WHBSHE_MABEL (FG3), WBKEO_SHMAB (FG5)

30 Central AR Constraint MABSH_WBSH (Flowgate 4)

31 Central AR Constraint Upgrades in the Change Case Terminal Limiting Equipment Upgrades: Mabelvale – Sheridan 500 kV from 1732 to 2546 MVA (FG1)

32 Central AR Constraint Change Case Base Flows

33 Central AR Constraint Change Case SHRMAB_WBKEO (Flowgate 1)

34 Central Ar Constraint Change Case SHRELD_HSPET(Flowgate 2)

35 Central AR Constraint Change Case WHBSHE_MABEL (FG3), WBKEO_SHMAB (FG5)

36 Central Ar Constraint Change Case MABSH_WBSH (Flowgate 4)

Results Summary

38 Results Summary: ISTEP solution FGDescriptionISTEP Project no. MVA Added New MVA Rating 1Sheridan – Mabelvale 500 kV FTLO White Bluff – Keo 500 kV (SHRMAB_KEO) Sheridan – El Dorado 500 kV FTLO Etta – McNeil 500 kV (SHRELD_HSPET) White Bluff – Sheridan 500 kV FTLO Mabelvale – Sheridan 500kV (WHBSHE_MABEL) Mabelvale – Sheridan 500 kV FTLO White Bluff – Sheridan 500kV (MABSH_WBSH) White Bluff – Keo 500 kV FTLO Sheridan – Mabelvale 500 FTLO (WBKEO_SHMAB) NoneN/A

39 Preliminary Cost Estimate Limiting Element Listing Project 1: Southcentral AR / Northeast LA Constraint DescriptionLine Rating 1st Limiting ElementICT Cost Estimate* Sheridan – El Dorado 500 FTLO Hot Springs – Etta 500 SHRELD_HSPET(FG2) 1732MVA (2000A) Sheridan CT ratio ~2000A El Dorado switch & line trap all ~2000A Replace CT $225,000 Replace Switch & Line Trap $700,000 ($925,000) (+433MVA) 2nd Limiting Element ICT Cost Estimate* Sheridan 4 switches ~2500A Sheridan line trap ~2500A Replace 4 Switches and Line Trap ($1,300,000) (+381MVA) DescriptionLine Rating 1st Limiting ElementICT Cost Estimate* White Bluff – Sheridan 500 FTLO Sheridan – Mabelvale 500 WHBSHE_MABEL (FG3) 1732MVA (2000A) Sheridan ~2000AUpgrade CT $225,000 (+433MVA) 2nd Limiting Element ICT Cost Estimate* 5 White Bluff ~2500A Replace 5 Switches $1,000,000 (+381MVA) DescriptionLine Rating 1st Limiting ElementICT Cost Estimate* Mabelvale – Sheridan 500 FTLO White Bluff – Sheridan 500 MABSHE_WBSH (FG4) 1732MVA (2000A) Mabevale 4 Switches & Line Trap--2000A Replace 4 Switches and Line Trap $500,000 ($1,300,000) (+433MVA) 2nd Limiting Element ICT Cost Estimate* Sheridan Line trap ~2500A Sheridan 4 Switches ~2500A Replace 4 Switches and Line Trap ($1,300,000) (+381MVA) * costs for upgrades to substation bus, and/or breaker relaying, and/or line relaying are not included in the above estimates. If required, additional costs will apply.

40 Preliminary Cost Estimate Limiting Element Listing Project 2: Central Arkansas Constraint DescriptionLine Rating1st Limiting ElementICT Cost Estimate* Sheridan – Mabelvale 500 FTLO White Bluff – Keo 500 SHRMAB_KEO (FG1) 1732MVA (2000A)Mabelvale 5 Switches & Line Trap—2000A Replace 5 Switches & Line Trap $1,500,000 (+433MVA) 2nd Limiting ElementICT Cost Estimate* Sheridan 4 Switches & Line Trap ~2500A Replace 4 Switches & Line Trap $1,300,000 (+381MVA) * costs for upgrades to substation bus, and/or breaker relaying, and/or line relaying are not included in the above estimates. If required, additional costs will apply.

Next Steps

42 Further Analysis for Projects 1 and 2 Begin Work on Projects 3, 4, and 5 Status Report at October LTTIWG Meeting Next Steps

Douglas Bowman, PE, PMP Lead Engineer, ICT Planning Questions?