For two identically constructed transmission lines, Line A (150 miles) produces more reactive power than Line B (15 miles). What can be inferred about their loading conditions?

The correct inference is that Line A producing more reactive power than Line B is indicative of their loading conditions, specifically reflecting that Line A is likely heavily loaded compared to Line B.

Reactive power is influenced by the amount of current flowing through the transmission lines; more reactive power typically indicates higher current flow associated with heavier loading. Since Line A is significantly longer than Line B, under equivalent construction, it can be expected to have greater reactance. Therefore, if Line A is producing more reactive power, it suggests that it is under a heavier load compared to the shorter Line B, which might not require as much reactive power generation.

In other words, the loading condition is best understood with the realization that the longer line (Line A) experiences more losses and hence needs to carry more reactive power to maintain voltage levels. Meanwhile, Line B, being shorter, would not typically need to produce the same level of reactive power because the current (and thus loading) is lower.

Thus, the appropriate association is that Line A is experiencing heavier loading circumstances than Line B, leading to the conclusion regarding their individual reactive power productions.