The Planning Committee approved two alternatives to protect wind generators from being assigned artificially depressed capacity values due to curtailments ordered by PJM.

Under current policy, when wind generators are curtailed by PJM for any portion of a peak summer hour, the hour is excluded from the generator’s capacity credit calculation. (See Alternative Wind Capacity Calculations Yield Murky Results.)

Under Alternative 2, state estimator data would be used to interpolate output for each five-minute period with curtailments.

Under Alternative 3, forecast data from PJM operations — which is currently used for lost opportunity cost calculations — would be used for hours with curtailments.

Metered data would be used for all hours without curtailments under both options. Units with no curtailments over peak summer hours would not be affected by either option.

Alternative 2 was approved by a 101-23 margin and will be the primary option considered by the Markets and Reliability Committee. The MRC also can select Alternative 3, which was approved by a narrower 68-40 margin.

Assuming MRC approval, the new procedure would be applied to summer 2013 when capacity credit calculations are finalized in December 2013.