Theory of Parallel Grounded Wires and Production of High Frequencies in Transmission Lines

The overhead grounded wire is used for three purposes: lightning protection, mechanical support for towers, and a test circuit. The functions of the grounded wire are subdivided into at least four categories: First, the vertical grounded wire; second, the lightning rod extending above the ground; third the electrostatic induction in the horizontally situated wires, and fourth, electromagnetic induction. The vertical wire prevents splitting of the poles. The lightning rod is of mooted desirability. The electrostatic induction for a given cloud on wires under various conditions is worked out in this paper. There is given also the protective values of overhead grounded wires in different positions and in different numbers. The effects of electromagnetic inductions have been taken into account. Theory is given to show that the grounded wire introduces into the main wave of induced lightning surge a superposed high frequency of electromagnetic induction. The several factors to be taken into account in the process of determining the protective value of a grounded wire are as follows: 1. Strength of electric field in the neighborhood of the line wires. 2. The direction of the gathering charge in the cloud, that is the path of the discharge relative to the line, parallel or perpendicular to the line before it turns vertically downward to the earth. 3. The screening effect obtained by the use of several wires, with and without grounded wires. 4. The initial momentary potential induced on a wire at the instant the cloud discharges to earth. 5.