What effect does thermal conditions have on transmission lines?

Thermal conditions play a crucial role in determining the capacity of transmission lines. As temperature increases, the resistance of the conductors also rises, which can lead to higher energy losses in the form of heat. This means that the amount of electrical current that can safely flow through a transmission line without overheating is limited by the thermal conditions. If the temperature exceeds certain thresholds, the risk of damage or failure increases, which effectively reduces the operational capacity of the line. Hence, thermal conditions directly impact how much power can be transmitted without compromising safety and efficiency.

In contrast, the other options are related to aspects of transmission line performance but do not accurately reflect the primary effect of thermal conditions. While voltage can be affected by various factors, it is not solely dependent on thermal conditions. Insulation properties, while important for preventing electrical failures, are influenced by other factors such as materials and environmental conditions rather than thermal dynamics alone. Therefore, the correct answer highlights the limiting factor that thermal conditions impose on the capacity of transmission lines.