Evolving Planning Criteria for a Sustainable Power Grid

(LOLE) of 1-day-in-10-years are insufficient to account for the increased variability and uncertainty caused by the evolving resource mix, increasing demand level, and demand side management.

The North American Electric Reliability Corporation (NERC) recommends thresholds for assessing the risk of LOLE based on annual Expected Unserved Energy (EUE) and Loss of

Load Hours (LOLH). Annual EUE thresholds that are zero, or near zero, will be considered low, Normalized Expected Unserved Energy (NEUE) less than or equal to 0.002% as medium, and any NEUE greater than 0.002% as high risk. Total energy should be annualized (calculated as a percentage) over an assessment area and interconnection. Annual LOLH thresholds of less than 0.1 will be considered low, thresholds between 0.1 and 2.4 as medium, and any hours above 2.4 as high risk. Planners must incorporate the anticipated effects of extreme weather. In addition to the evaluation of the equivalent 1-day-in-10-years criterion, NERC is currently developing a new reliability process using a common tool for wide-area energy evaluation to address energy adequacy risks based on LOLH and EUE and ensure consistency across all assessment areas in North America. This approach enables more effective measurement of energy adequacy under extreme weather conditions and provides a foundation for harmonizing inter-area transfer (“tie-benefit”) assumptions across interconnected control areas. Currently, no consistent method exists to determine whether control areas (or balancing authorities) make realistic import assumptions from neighbors during low probability, wide-area weather events.

Resource and transmission adequacy studies must be coordinated to capture their interrelated impacts while considering significant impact of data center load. A white paper, practice guide, or reliability guideline for resource and transmission planners will ensure that key study elements and methods are included in adequacy planning. In addition, a pilot study will assess improvements, and the benefits achieved through these recommendations. These efforts combined with study beyond the 10-year horizon are integral to assuring resource and transmission adequacy.