ROS December 2007

Carlos Gonzalez-PerezERCOT Operations Support

CFE-ERCOT DC-Ties Commercial Operations

1 10/30-31/2007CFE/ERCOT/AEP Meeting – Mexico City

ERCOT DC-Ties

ERCOT-CFE Operational DC-TiesEagle Pass (DC_S, 36 MW) Laredo Variable Frequency Transformer

(DC_L, 100 MW)Sharyland Railroad (DC_R, 150MW)

ERCOT-SPP Operational DC-TiesNorth 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

2 ROS Meeting – December 2007

Commercial Operational Aspects

3 ROS Meeting – December 2007

Future Commercial Ops. of the DC-Ties

ERCOT management of the scheduling process in the South DC-Ties will be similar to the North DC-Ties

Minimal modifications to the ERCOT systems will be necessary

CFE to establish a NERC E-Tag operation for transactions between Mexico and ERCOT (and vice versa)

4 ROS Meeting – December 2007

ERCOT DC-Ties Scheduling Process

Schedule Checkout with Interconnected CA

Implement eTag Schedules with DC Tie Operators

QSEOATI Scheduling Agent

& Software Services

SPP/CFE DC Tie

Scheduling Function

Submit E-Tag Schedules

Arrange for DC Tie Capacity

Submit DC Tie Market Schedules

DC TieOperator

Match E-Tag Schedules to ReservationsManage DC Tie Scheduling Process

Approve eTag Schedules

Match eTag Schedules to Market SchedulesApprove eTag Schedules

Checkout Metered Flows with DC Tie OperatorERCOT DC Tie

Scheduling Schedule Checkout with Interconnected CA

5 ROS Meeting – December 2007

Proposed Day Ahead Operations – Limit Calculations

Limits are initially calculated Daily (can be changed to weekly, etc)

CFE to provide ERCOT limits by 16:00Most constrained transfer limits will be made

public and postedLimits will be recalculated in real-time based on

system conditions as needed

CFE Day Ahead Transfer Limits

ERCOT Day Ahead Transfer Limits

Tie De-Ratings

LIMIT Set to the Lower of all the

Values

6 ROS Meeting – December 2007

Schedule Curtailment Process

7 ROS Meeting – December 2007

Inadvertent AccountingScheduled Energy: Calculated from the NERC E-

TagActual Energy:

Real-time SCADA hourly integrated. For hourly monitoring

EPS meter true-up 7 days after the factDaily Check-out:

Between ERCOT Operator and Tie Operator after midnight

Define payback in kind schedules, if the Inadvertent Balance larger than X MWh

Monthly True-up Between CFE and ERCOTKeeping up with the Inadvertent Account Balance

8 ROS Meeting – December 2007

Before going into Commercial Operations

Finalize Operating procedures for the South DC-Ties

Finalize an Emergency Assistance Agreement with CFE

Finalize Inadvertent agreement with CFECFE to have an E-Tag operation in placeERCOT to finalize the testing of ERCOT

systemsTie Operator systems readyCFE declare ready for Commercial

Operations9 ROS Meeting – December 2007