The series impedance of an overhead transmission line is primarily a function of frequency, conductor resistance, conductor geometry, line geometry, and earth conductivity. In the fundamental work on the subject, Carson (2) developed equations for the self impedance of a conductor with earth return and the mutual impedance of two conductors with common earth return. These equations have been discussed and elaborated upon many times over the years. Wagner and Evans (4), Clarke (3), and Anderson (1) provide excellent complementary discussions of the topic. The current formulation of the problem draws from each of these sources but follows the exposition of Clarke (3) most closely.