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Improving Efficiency with Dynamic Line Ratings

September 2015
U.S. Department of Energy
Smart Grid Demonstration Project, dynamic line ratings, New York Power Authority

Comparing dynamic line ratings (DLR) to static line ratings - is a bit like comparing a high-tech video to a black-and-white photograph. Where static line ratings provide seasonally dependent, conservative estimates of overhead transmission-line current capacity, DLR provides real-time, play-by-play data about the effects of air temperature, solar radiation, and wind speed and direction on the transmission line, such as conductor temperature and sag. Armed with this crucial information, along with transmission line physical characteristics, the grid operator is better equipped to target power needs precisely, while safely operating lines that are nearing their thermal limits.

Line ratings are critical to prevent excessive power-line drooping, which could cause a fault if lines contact vegetation or other objects. The static rating indicates the maximum amount of current that the line's conductors can carry (under a set of assumed weather conditions) without violating clearance safety codes or damaging the conductor. With line ratings, operators can determine how much power can