Abstract: For the first time a Real Time Thermal Rating System has been developed for overhead transmission lines using actual meteorological data and real-time conductor temperatures and line loadings. This System provides, on a probability basis, much higher ampacity ratings than those derived from conventional methods. As a portion of this System, a steady state thermal rating procedure is presented in the companion paper, which includes forced convection heat transfer equations taking into account the effect of wind turbulence or gustiness, conductor yaw (wind direction), conductor height above ground, smooth versus rough (stranded) conductor surfaces, the proximity of conductors in a bundle, and conductor pitch. A natural convective heat equation is developed for stranded conductors. The conductor temperature is solved directly without resorting to an iterative solution.