Operating reserves The additional uncertainty and variability caused by an increasing penetration of wind power generation raises the question of whether current requirements for operating reserves are adequate. The need for regulation services may increase due to the short-term variations in wind power generation, although the short frequency of RT dispatch (5 min) in most ISO/RTO markets reduce the magnitude of variations that must be handled through regulation services. An increase in slower starting reserves may be necessary to be able to counter large-scale wind power down-ramping events. Ongoing research is addressing the optimal determination of reserve requirements under high penetration of wind power (Ortega-Vazquez and Kirschen 2009). Since wind power forecasting models now are being able to produce probabilistic estimates for the wind power generation, one could potentially use the uncertainty information from the forecast in determining the operating reserves requirements. Consequently, the operating reserve requirement could depend on the forecasted level and uncertainty in wind power generation for the next day. This would require that operating reserve requirements are determined more frequently and closer to real-time than what is typically the case today.