| This thesis addresses the problem of electric power transmission line modeling. Presently, several power transmission line models exist. However, each one is accurate for a specific range of frequencies. None of the existing models represents the effects of power line tower grounding, which are substantial over a wide range of frequencies.;A unified model of electric power transmission lines is presented which is accurate for the frequency range of interest. Specifically, the advantages of the new model are: (1) accurate frequency dependent parameter representation from DC to 1 MHz, (2) explicit representation of transmission line grounding systems, (3) explicit modeling of line asymmetries, and (4) numerical efficiency.;The model implementation is based on the solution of the transmission line partial differential equations. These equations are solved analytically in the frequency domain, and then transformed into the time domain numerically utilizing the Fast Fourier Transform technique. Tower and substation grounding systems are represented with step response functions either computed by finite element analysis or obtained by field measurement. The responses of both grounding system and transmission line are combined resulting in a multiple input-multiple output system characterized by a set of step response functions. These functions are utilized in a time domain computer simulation of electric power networks. The problem of computational efficiency is effectively addressed using a linear convolution scheme.;Three application examples of the model are presented: (1) switching surge overvoltage computation, (2) distribution system impedance frequency response computation, and (3) lightning surge overvoltage computation. The simulation results of the first two applications are compared to field measurements. Agreement between model prediction and field measurements is excellent. |
