An aluminum transmission line with a diameter of20 mm has

Chapter 7, Problem 7.66

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An aluminum transmission line with a diameter of20 mm has an electrical resistance of and carries a current of 700 A. The line issubjected to frequent and severe cross winds, increas-ing the probability of contact between adjacent lines,thereby causing sparks and creating a potential fire haz-ard for nearby vegetation. The remedy is to insulate theline, but with the adverse effect of increasing the con- ductor operating temperature.(a) Calculate the conductor temperature when the airtemperature is 20?C and the line is subjected tocross flow with a velocity of 10 m/s.(b) Calculate the conductor temperature for the sameconditions, but with a 2-mm-thick insulation havinga thermal conductivity of 0.15 W/m?K. (c) Calculate and plot the temperatures of the bare andinsulated conductors for wind velocities in therange from 2 to 20 m/s. Comment on features ofthe curves and the effect of the wind velocity on theconductor temperatures