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T/F: maximum wind speed for ampacity

Short answer

FALSE. For safe ampacity, a low wind speed (0.5–0.6 m/s) is assumed to avoid overestimating convective cooling; using maximum wind speed would overrate the conductor, leading to overheating on calm days. Maximum wind speed is applied in mechanical design.

State and justify whether the following statement is TRUE or FALSE: For conductor ampacity computation, maximum wind speed is taken into account.

FALSE.

Ampacity is the largest current the conductor can carry continuously without exceeding its maximum allowable temperature. It comes from the heat balance:

I2R+qsolar=qconvection+qradiationI^2R + q_{solar} = q_{convection} + q_{radiation}

Convective cooling rises strongly with wind speed. If the maximum wind speed were assumed, the cooling would be overestimated. The rating would be too high, and on calm days the conductor would overheat, anneal and sag below the safe ground clearance.

So, for a safe (conservative) rating, a low wind speed is assumed, typically 0.5–0.6 m/s (as in the given ACSR table, 0.6 m/s). It is combined with high ambient temperature and full solar radiation.

The maximum wind speed is used instead for mechanical design: tower loads, conductor tension and insulator swing.

✓ Answer checked by Claude Opus 5.5 (high effort)

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