I've read in a newspaper aerial electrical lines (conductors) have less diameter than subterranean lines. Also, the typical weight of subterranean lines is 30Kg/m, while aerial ones is 2Kg/m. Why do they have such differences of diameter and weight? Must the subterranean lines be more isolated than aerial ones? Another question: do you think subterranean lines causes less electromagnetic intensity field in the surface road than aerial ones?. Why? Thanks in advance.