Factors that influence variable transfers

Increasing installations of large amounts of renewable generation are contributing to a transition of the Electric Power industry operating model away from base loaded generating resources and power transfers between Balancing Authorities (“BAs”) that are generally fixed for an hour. In contrast, Variable Energy Resources can change generation many times within an hour. In addition, when wind generation has large changes and when utilities generation reserves are low, utilities cannot provide enough balancing resources for the wind, necessitating the acquisition of balancing resources from other BAs, which in turn varies power transfers and also varies in opposition to the wind generation. Utilities are challenged to manage unanticipated flow variations (Variable Transfer/Dynamic Transfer) that result from the variation in generation output. This paper will show that one MW of Variable Transfer is not equivalent to one MW of static transfer and that Variable Transfer has a high impact on static transfer. More Variable Transfer on a path will reduce the static transfer at a faster rate and reduce path utilization factor. Also this paper presents the major factors that influence the Variable Transfer Limits. A thorough understanding of the impact of Variable Transfer on grid operations is critical to ensuring reliable operation and quantifying the true cost to transmission users (i.e., wind) as more dynamic transfer capability is added to support regional initiatives.