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Texas Nodal

Texas Nodal EMS & MMS

AREVA & ERCOT Comments on

Generation to be dispatched by SCED

January 24, 2007

Sai Moorty

MMS Project Engineer

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Texas Nodal

AREVA (EMS Vendor ) Comments

Option 1GTBD =  ∑Genactual AREVA believes this does not do enough to help the system recover frequency deviations. The

concern is that the system would always be 'behind' where it needs to be.

Option 2 GTBD =  ∑Genactual + ∑NCLactual - ∑NCL30 min average  + PSCED * LRR High complexity. The problem is not the NCL values, but the LRR value. Many other systems have struggled to get a reliable calculation for LRR. For example, if this is

just the average load rate over an hour, does that mean that recognition of the peak (load turn-around point) will be delayed by as much as half an hour? Then there is the issue of what to do with the near-term load swings.

Also, it is easier to implement to compare the current NCL with a filtered NCL.

Option3 (Alternative proposal by AREVA) GTBD =  ∑Genactual + Frequency Recovery MW - (∑NCLactual - ∑NCLfiltered) Frequency Recovery MW is load damping (Df) component. Addresses the points of concern and be much easier to implement/maintain. This approach will provided the MW boost to address frequency deviation while not causing the

system to swing to the other extreme when the nonconforming load swings.

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Texas Nodal

ERCOT Comments

Nodal EMS Project does not have Short Term Load Forecast. LRR calculation will be based on actuals.

Assumption that LMPs calculated by SCED is effective from the time SCED is executed till the time of next SCED execution.