2007 South DC-Tie Emergency OperationTPTF

November 27, 2007

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Agenda

• Current Operations of the DC-Ties• Summary of the Schedules flows in the last 12 Months

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ERCOT DC-Ties

• ERCOT-CFE Operational DC-Ties– Eagle Pass (DC_S, 36 MW) – Laredo Variable Frequency Transformer (DC_L, 100 MW)– Sharyland Railroad (DC_R, 150MW)

• ERCOT-SPP Operational DC-Ties– North DC_Tie (DC_N, 220 MW)– East DC_Tie (DC_E 600 MW)

DC_N220 MW DC_E

600 MW

DC_S36 MW

DC_L100 MW

DC_R150 MW

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ERCOT DC-Ties -- Operations

• ERCOT/SPP DC-Ties– Open for commercial transactions and operation

• ERCOT/CFE DC-Ties– Interim agreement in place with CFE. Addresses

emergency assistance through the DC-Tie and BLT• Transmission Outages, Supply shortages, voltage

deficiencies and other– Currently only utilized under emergency conditions

• Transmission Emergency Condition• EECP

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• ERCOT received DC-Tie flows 32 times through the South DC-Ties from October 2006 to August 2007.

– Each DC-Tie flow corresponds with a declaration of an Emergency Condition.

South DC Tie Requests

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Eagle Pass DC-Tie Emergency Assistance Schedules

• Request for Emergency Assistance:– 25 Times due to Transmission Emergency Conditions

Month Days

October 06 6 (Outage)

November 06 5 (Outage)

December 06 2 (Outage)

January 07 5 (Winter Storm)

February 07 7 (Outage)

• 2 Times due to EECP, June 18th, 2007 & August 1st, 2007

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Other South DC-Tie Emergency Assistance Schedules

Laredo VFT DC-Tie Schedules• Request for Emergency Energy:

– 3 Times due to Transmission Emergency Conditions• July 16, 17, 18 of 2007• Due to a planned outage of a local RMR unit in the Laredo

area.

– 2 Times due to EECP, June 18th, 2007 & August 1st, 2007

Railroad DC-Tie Schedules• No emergency schedules in the Tie