The Markets and Reliability Committee Thursday reviewed two alternatives to protect wind generators from being assigned artificially depressed capacity values due to curtailments ordered by PJM. The committee will be asked to approve one of the alternatives at its next meeting.

Under current policy, when wind generators are curtailed by PJM for any portion of a peak summer hour (2-6 p.m.), the entire hour is excluded from the generator’s capacity calculation.

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 curtailment periods.

Both options would use metered data for all hours without curtailments. Units with no curtailments over peak summer hours would not be affected by either option.

The Planning Committee last month approved Alternative 2 by a 101-23 margin, making it the primary option MRC will consider Sept. 26. The MRC also can select Alternative 3, which was approved more narrowly, 68-40. (See Planning Committee OKs Relief for Wind Generators.)

PJM’s Tom Falin said Alternative 2 may be more accurate for short curtailments while Alternative 3 is more accurate for long curtailments. “The most important curtailments are the long ones,” Falin said. “They’re going to impact the average more than a five-minute interruption.”

An analysis released by PJM showed that Alternative 2 would have increased ratings for 21 wind generators with 12 reduced and two unchanged. Alternative 3 increased ratings for 24 generators and reduced them for 11. (See chart)

Any new procedure approved by would be applied to summer 2013 data when capacity credit calculations are finalized in December 2013.