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Self‐inductance calculations are presented for coils of modular construction. Individual modules have a fixed winding density, so that a complete multi‐module coil will be characterized by larger inter‐turn spacing at its extremities to provide suitable insulation strength under impulse voltage conditions. Gives inductance computations using finite‐element analysis, so that empirical correction factors to take account of end‐effects and inter‐turn spacing are unnecessary. Comparison where possible with established empirical methods shows consistency. Gives an example of oscillatory high‐voltage tests.

The purpose of this paper is to investigate the simultaneous effects of ionization and dispersion of soil on the impulse behavior of grounding electrodes under first and subsequent stroke currents.

A recently introduced technique called improved multi-conductor transmission line (MTL) is simplified for grounding electrodes buried in both-affected soils.

The simulation results show that including the two effects simultaneously in highly resistive soils under high-valued subsequent stroke current is recommended. Otherwise, simultaneous effects can be disregard.

To the best of the authors’ knowledge, there is no research on sensitivity analyses for the simultaneous inclusion of the two effects on the effective length and the induced voltage on the soil surface. To this end, the simplified MTL is applied to the grounding electrodes. The simulation results show that the computational efficiency in comparison with previous methods is, first, considerably increased. Second, the simultaneous effects result in decreasing the soil surface voltage with respect to situations where either ionization or dispersion is taken into account (single-affected soils). In other words, the performance of grounding systems is improved. Third, the effective length in both-affected soil is has a middle value with respect to the single-affected soil. Such findings practically and financially are of importance.

The purpose of this paper is to investigate the ionization and dispersion effects in combination with the inhomogeneity of soil simultaneously on the effective lengths of counterpoise wires.

Improved multi-conductor transmission line model is used for computing effective length of counterpoise wires considering all aspects of soils.

The simulation results show that the ionization and dispersion effects simultaneously results in placing the effective length between situations where only one effect is considered. Also, predicting formulae for effective length of counterpoise wires considering all effects are proposed.

A sensitivity analysis on the effective lengths of counterpoise wires considering all aspects of soils is carried out.