At its December 2021 open meeting, the Federal Energy Regulatory
Commission (FERC or the Commission) approved new rules to improve
utilization of the transmission system by redefining
“transmission line rating” to account for ambient
weather conditions. The Commission expects that the change will
permit greater transmission line utilization while also fostering
reliability and safety. Transmission providers have 120 days to
submit a compliance filing to account for the redefinition and must
implement all requirements within three years of the compliance
filing due date.
BACKGROUND
A transmission line rating represents the maximum transfer
capability of the transmission line. Ambient air temperature, among
other things, can affect transmission capability. Warmer weather
reduces transmission capability whereas colder weather increases
it.
