A sensitivity study of HV and EHV lightning performance shows that surge response characteristics of towers and lines are as important as the footing response. Tower travel time has a very large sensitivity for taller double-circuit lines. Existing methods for analysis of tower and line response have considerable uncertainty. This uncertainty is resolved by extensions to travelling- wave analysis combined with experimental verification. New equations for tower surge impedance and tower travel time are proposed to deal with the most common situation of a midspan stroke to the skywire.

Lightning Surge Response Of Transmission Towers

A new method has been developed to study the transient behavior of nonuniform transmission lines whose parameters can have any arbitrary space variation. Using the exponential line as a building block, s-domain expressions are obtained for the voltage and current at any point along the nonuniform line. An efficient numerical Laplace-transform inversion technique is then used to compute the time-domain solution. Computer simulations and comparisons with other solution methods are included. >

Transient analysis of lossless single-phase nonuniform transmission lines

The conventional traveling-wave technique is extended to nonuniform lines by attributing distributed reflection and refraction coefficients to each point on the line. Analytical expressions are derived giving the variations in voltage and current wave fronts as they travel along a nonuniform line as well as variations in the voltage and current and their respective ratio Z(t) = E/I at a fixed position of the line caused by the continuous generation of reflections along the line. It is shown that the ratio Z(t), representing the so-called transient surge impedance of a given position of a nonuniform line, depends not only on time and the function expressing the conventional surge impedance of the line but also on the shape of the current wave, a fact which considerably reduces the usefulness of Z(t) in solving nonuniform line problems.

Wave Propagation on Nonuniform Lines

Field Studies of the Surge Response of a 345-Kv Transmission Tower and Ground Wire

The analysis of electromagnetic transients on nonuniform lines is addressed with special attention paid to those transients relevant to power networks. Traveling-wave and time-domain solutions are discussed, and the applicability of a proposed s-domain, distributed parameter direct-simulation technique is demonstrated. It is shown that this approach yields exact solutions in cases where the characteristic impedance at any line point can be represented by some analytic function of the coordinate of that point. Two examples of this are discussed. Comparisons between the other techniques and the advantages and limitations of the suggested technique are given. >

L. O. Barthold

Papers

An Approximate Transient Solution of the Tapered Transmission Line