On January 24, 2017, FERC issued an order accepting simultaneous transmission import limit (“SIL”) values for the Southwest United States from a group of transmission owners operating in the region. In the Order, FERC noted its intent to use these SIL values in evaluating updated market power analyses for the Southwest region, and also provided guidance for future filers on how the Commission expects SIL studies to be performed and reported.

SIL studies are used for determining the simultaneous import level of available uncommitted capacity for a particular balancing authority area under normal and various contingency operating conditions. As noted by FERC in Order No. 697, a SIL study is “intended to provide a reasonable simulation of historical conditions” and is not “a theoretical maximum import capability or best import case scenario.” The SIL values resulting from these studies are then used by FERC to examine market analyses for the studied balancing authority areas and the broader regions surrounding them.

In December 2015 and January 2016, a group of primarily Southwest-based transmission owners collaborated to submit updated market power analyses, and associated SIL studies and values, for the December 2013-November 2014 study period in compliance with FERC’s regional reporting deadlines. The transmission owners group included Southwest utilities such as Public Service Company of New Mexico, Tucson Electric Power Company, and Arizona Public Service Company, as well as some non-Southwest companies like Public Service Company of Colorado and Northern States Power Company of Minnesota.

In its January 24, 2017 Order, FERC accepted the SIL values proposed by the transmission owners group and commended the filers for their coordination and information sharing, stating that such a collaborative approach “leads to more accurate and consistent SIL study results.” FERC then relisted the accepted SIL-values in an appendix for future Southwest transmission-owning and non-owning entities seeking to file updated market power analyses during the current study period.

Additionally, FERC also took the opportunity to provide guidance to future filers on how to perform and report SIL studies. In particular, FERC discussed the types of contingencies that should be listed and used in SIL studies, emphasized the need for accuracy to protect against system overload events, and noted that any changes in SIL values from previous study periods should be identified and explained.

Click here to find FERC’s Order and the appendix providing the accepted SIL values for the Southwest Region.