Impulse impedance of rectangular grounding grids

In an earlier work B.R. Gupta and B. Thapar (1980) presented the results of investigations and empirical formulae to evaluate the impulse impedance of square grounding grids. In the present work, the authors extend those investigations to the rectangular grounding grids. Empirical formulae for the effective area and impulse coefficient for center-fed and corner-fed rectangular grids are presented. The validity of the analytical method has been verified experimentally with model tests. Comparison of square and rectangular grids is presented. The effect of length-to-breadth ratio of the grid on the impulse impedance is discussed