The purpose of a transmission network is to transfer electric energy from generating units at various locations to the distributions system which ultimately supplies the load. Transmission lines also interconnect neighbouring utilities which permits not only economic dispatch of power within regions during normal conditions, but also transfer of power between regions during emergencies.

All transmission lines in a power system exhibit the electrical properties of resistance, inductance, capacitance and conductance. The inductance and capacitance are due to the effects of magnetic and electric fields around the conductor. These parameters are essential for the development of the transmission line models used in power system analysis. The shunt conductance accounts for leakage currents flowing across insulators and ionized pathways in the air. The leakage currents are negligible compared to the current flowing in the transmission lines and may be neglected. 

The first part of this course deals with the determination of inductance and capacitance of overhead lines. The concept of geometric mean radius, GMR and geometric mean distance GMD are discussed and the functions [ GMD, GMRL, GMRC]= gmd is developed for the evaluation of GMR and GMD. This function is very useful for computing the inductance and capacitance of single-circuit or double circuit transmission lines with bundled conductor. 

Alternatively, the function [ L, C]= gmd2LC returns the line inductance in mH per km and the shunt capacitance in microFarad per km. Finally, the effects of electromagnetic and electrostatic induction are discussed.