Overhead transmission lines are less expensive, in most cases, significantly less expensive, than underground cables. Underground transmission cables require insulation, cooling systems, and -the...
To provide a low impedance path for ground current. In overhead lines, the earth wire is often hung at the top of poles to help provide lightning protection for the phase wires.
High voltage transmission lines can transmit more power when the total impedance of the line is lowered. Inductive reactance is typically ten times larger than the series resistance of a conductor....