Emergency ratings have been introduced for operating transmission lines safely and supplying current capacity efficiently, as well as controlling load flow when occurring line faults. In this paper, short-term emergency ratings are calculated by using thermal equilibrium equation for bared conductors in double-circuit transmission lines. Overhead transmission lines installed in double-circuit have been extensively utilized worldwide to enhance power transmission. Such lines show various advantages in increasing transmission capacity and decreasing power loss as well as being operated flexibly during a contingency. Even when a fault occurs in one circuit, the healthy circuit can supply power continuously during emergency without outage. The utilization of such double-circuit transmission lines during normal and/or emergency operations is described. Maximum normal operating current based on fault duration, maximum allowable temperature of conductor, and thermal line ratings are evaluated. Several performances of dip/clearance affecting short-term emergency rating are also presented.
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