Definition
A Transmission Line Rating defined in Attachment M (Order 881) that applies to a period of not more than one hour and reflects an up-to-date forecast of ambient air temperature — including absence of solar heating at night — updated at least hourly. Transmission Providers must use AARs (rather than static seasonal ratings) when evaluating Near-Term Transmission Service requests, posting ATC for the next 10 days, and determining whether to curtail service due to line-flow limits within a 10-day window. AARs unlock additional transfer capability in cooler weather and prevent overloads during heat waves by reflecting actual line ampacity in real time.
Topic Deck
Grid Operations
Source
FERC Pro Forma OATT / LGIP
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