Symmetrical Components‐Transmission Lines and Cables

Transmission lines are modeled with respect to their lengths. Partial differential equations are used and the power transmission occurs like a wave motion. This shows dependence on frequency as well as on soil resistivity. The zero sequence current flowing in one phase also encounters the currents arising out of that conductor self‐inductance, from mutual inductance to other two phase conductors, from the mutual inductance to the ground and sheath return paths, and the self‐inductance of the return paths. A three‐phase transmission line has couplings between phase‐to‐phase conductors and also between phase‐to‐ground conductors. The Carson's formula is of importance even today in calculations of line constants. The capacitance of three‐phase lines with ground wires and with bundle conductors can be addressed as in the calculations of inductances. This chapter also talks about capacitance of lines, cable constants, Electromagnetic Transient Program (EMTP) models, bundle conductors and effect of harmonics on line models.