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  • Transmission reliability margin
    Currently, the ISO implements certain adjustments to intertie schedules within operating hours. Using a mechanism known as Transmission Reliability Margin, the ISO will be able to anticipate these transmission constraints in advance by reflecting them in market processes before schedules are awarded in the hour-ahead scheduling process. In this initiative, the ISO will develop tariff revisions and the NERC-required transmission reliability margin implementation document. The document will provide greater clarity regarding ISO management of transmission constraints in the real-time market.
    • Outcome
      The ISO implemented its transmission reliability margin mechanism in December 2012. This change enables the ISO to make certain adjustments to intertie schedules in the pre hour-ahead market processes in anticipation of transmission constraints. This mechanism avoids the need for these adjustments within the operating hour, which can be disruptive by causing curtailment of bilateral trades. The margin values applied to each intertie are now visible through the ISO’s Open Access Same-Time Information System (OASIS). — Implemented: Dec. 11, 2012; FERC approval: June 5, 2012; Tariff amendment filing: April 10, 2012 (ER12-1468); Board of Governors approval: March 22, 2012
    • Transmission reliability margin - papers and proposals
    • Comments on draft final proposal
    • Comments on issue paper and straw proposal