Importance of Vertical Earth Electrodes in Earthing Design

Vertical earth rods are provided in an earth grid at several locations. One purpose of vertical rod electrodes is to meet the statutory requirement of “two separate and distinct connections with a minimum of two different earth electrodes” in Section 61 of Indian Electricity Rules. The other purpose is to reach the deeper layer of earth which is more likely to have greater percentage of moisture than surface layer of earth. In this paper results of analysis of grid earth electrode of a station, where soil is modeled as two-layer with the bottom layer of lower resistivity, are presented. It is shown that use of vertical rods together with horizontal grid is a very sound economic choice.