Impact of Hurricane Ike on CenterPoint Energy’s Transmission System Paul Rocha Director, Transmission Planning Presented at October 2, 2008 ERCOT TAC Meeting

Hurricane Ike 9/12/2008 7 PM Energized Out Restored 0 Circuits Out

Hurricane Ike 9/12/2008 11 PM Energized Out Restored 14 Circuits Out

Hurricane Ike 9/13/2008 2 AM - Landfall Energized Out Restored 36 Circuits Out

Hurricane Ike 9/13/2008 5 AM Energized Out Restored 67 Circuits Out

Hurricane Ike 9/13/2008 8 AM Energized Out Restored 90 Circuits Out

Hurricane Ike 9/13/2008 3 PM Energized Out Restored 97 Circuits Out

Hurricane Ike 9/13/2008 Restoration – 7% Energized Out Restored 7 Circuits Restored 90 Circuits Out

Hurricane Ike 9/14/2008 Restoration – 41% Energized Out Restored 40 Circuits Restored 58 Circuits Out

Hurricane Ike 9/15/2008 Restoration – 70% Energized Out Restored 70 Circuits Restored 30 Circuits Out

Hurricane Ike 9/16/2008 Restoration – 87% Energized Out Restored 87 Circuits Restored 13 Circuits Out

Hurricane Ike 9/17/2008 Restoration – 94% Energized Out Restored 94 Circuits Restored 6 Circuits Out

Hurricane Ike 9/23/2008 Restoration – 100% Energized Out Restored 100 Circuits Restored 0 Circuits Out

Pole Damage

Pole Replacement

CenterPoint MW Load Restoration

Seawall Substation

Stewart Substation

West Bay Substation

Moody Substation

Galveston Substation

West Galveston Substation

Mobile Substation

Network Changes After reviewing damage assessments and analyzing power flow study results, CenterPoint Energy decided not to restore the 69 kV portion of damaged West Galveston substation and 69 kV Ckt. 13, Lamarque – West Galveston Removal of damaged 69 kV connections to Galveston Island could cause some increased loading on remaining three 138 kV connections to Galveston Island Timing depends on rate of load restoration and growth on Galveston Island CenterPoint Energy believes upgrades of remaining 138 kV facilities would be more practical, cost-effective, and timely than restoration of damaged 69 kV facilities CenterPoint Energy will evaluate upgrades to remaining 138 kV connections to Galveston

Galveston Island Network Changes - Temporary

Galveston Island Network Changes - Permanent

Emergency Entergy Connection Implemented emergency interconnection from CNP’s Crosby substation to Entergy’s Dayton substation 9/15/2008 From Dayton substation, CNP used new transmission line built by Entergy after Hurricane Rita to restore power to water plant on the Trinity River normally served by Entergy Disconnected Entergy emergency connection 9/19/2008

Planned Transmission Outages Deferred all planned outages during restoration process CenterPoint Energy expects to resume planned outages next week

Thank You!!! Mutual Assistance No report would be complete without noting the tremendous mutual assistance support from other utilities across North America Far too many to list here, but we want to say… Thank You!!!

Transmission Network Summary Transmission Network Was Quickly Restored Network restored to necessary functionality within 4 days However, storm surge affected Galveston Island, including CNP substations Grid stability maintained despite tie-line and other outages ERCOT actions to adjust for increased probability of line outages was effective Generators performed well 2007 completion of STP– Hillje– WAP tie-line helped Availability of mobile substations aided restoration effort New Entergy 138 kV line expedited water plant restoration Relay and Control infrastructure performed well Hurricane training and drills were effective in preparing personnel