Experimental and theoretical methods for determining the surge impedance of towers are presented. It is demonstrated that the values so obtained adequately describe the response of the tower when a transmission line is struck by lightning. A right cone representation for conventional double-circuit steel towers is proposed, and a theoretical analysis using field theory yields the surge impedance as Z= 60 ln (2/S) where S is the sine of the half-angle of the cone.

Tower Surge Impedance

In prediction of HV and EHV lightning outage rates, the tower surge response consists of two parameters, the tower impedance and the tower travel time. Of the two, tower travel time has a larger effect on the predictions. A new model for tower travel time is developed based on the relationship between tower capacitance and tower surface area. Effects of tower crossarms and other features are modelled correctly by the new theory. When the new model is used, improved lightning outage rate prediction accuracy is obtained for 500kV single circuit lines.

Travel Time of Transmission Towers

This paper presents results of field testing on towers whose heights vary from 26 to 214 meters according to the author's new measuring method. The data of each tower were consistently in agreement. Surge characteristics of the towers were made clear by these measurements.

Studies of the Surge Response on a Transmission Line Tower

This paper describes analytical and experimental studies on tower surge response, including effects of return stroke current. Such effects have been ignored in previous lightning surge analyzes of transmission towers. A new method for calculating transmission tower surge response including the effects of return stroke current is proposed. The proposed method is based on the electromagnetic field theory, and it clearly shows that the tower surge response depends on the direction and velocity of the return stroke current. The tower surge response calculated by the proposed method agrees well with the measured tower surge response obtained from scale model tests and field tests.

Analytical and experimental study on surge response of transmission tower

This paper presents experimental and analytical studies on the lightning surge response of a 500-kV transmission tower without overhead lines. A number of experimental studies on the lightning surge response of transmission towers have been carried out. However, in these studies, the influence of the current injection angle was ignored. In this paper, an experimental investigation is conducted to assess the influences of the angle and direction of current injection. It is clearly shown that the lightning surge response of the tower depends on the angle and direction of current injection. These experimental results are compared with results calculated using numerical electromagnetic (EM)-field analysis. These calculated results agree with the experimental results. This suggests that numerical EM-field analysis can be employed for evaluating the surge response of a tower. Based on this, the surge response of a tower under a vertical lightning stroke is estimated. It is shown that the surge response under vertical current injection is approximately 30% higher than that under horizontal current injection. It is also shown that the angle and direction of the return stroke are important factors in determining the lightning surge response of a transmission tower.

/pdf/experimental-and-analytical-studies-on-lightning-surge-1n1w66k8r7.pdf

Experimental and Analytical Studies on Lightning Surge Response of 500-kV Transmission Tower

Lightning Performance of 138-Kv Twin-Circuit Transmission Lines of Commonwealth Edison Company - Operating Experience and Field Studies

An unusual number of flashovers due to lightning have occurred on the 138-kv lines of Commonwealth Edison Company on a relatively new type of 138-kv double-circuit tower designed for only one overhead ground wire. Calculations based on the most recent AIEE Committee Report1 for estimating lightning performance indicate that these towers should have tripout rates very much similar to the type of double-circuit towers that are designed for two overhead ground wires. This paper goes a step beyond the AIEE Committee Report in that it considers the voltage surge induced on the conductors at the instant of field collapse through cloud discharge. This is done on a comparative basis for the new and old towers, as well as for modifications of the new towers. In addition, all towers are compared on a direct-stroke basis, in line with the AIEE Committee Report. A curve is presented which indicates a region where a second ground wire can be added to the new towers so that the resulting induced surge voltage and direct-stroke voltage compare favorably with previous designs. Actual modifications made in tower designs are discussed. These consist of: 1. changing the tower head to provide for two ground wires in a horizontal plane, and 2. adding a second ground wire at the height of the top phase conductor through the center of the tower.

Analytical Studies of Lightning Performance of 1- and 2-Ground-Wire 138-Kv Double-Circuit Lines of the Commonwealth Edison Company

Lightning flashover trip-out rate for 138-kv double circuit towers designed for one ground wire is far in excess of rate anticipated by Commonwealth Edison Company when installed in 1954. Results of studies are presented on the cause of these trip-outs. Significant differences in performance associated with change in design are pointed up.

E. F. Koncel

Papers

Lightning Performance of 138-Kv Twin-Circuit Transmission Lines of Commonwealth Edison Company - Operating Experience and Field Studies

Analytical Studies of Lightning Performance of 1- and 2-Ground-Wire 138-Kv Double-Circuit Lines of the Commonwealth Edison Company

Lightning performance of 138-kv twin circuit transmission lines