Safety Analysis of Grounding Grid with Special Concern to Seasonal Factor

摘要

The safety of the grounding grid can be evaluated on the basis of maximum allowable limits of step voltage, touch voltage and ground potential rise (GPR). There is a direct dependence of grounding grid resistance, step voltage and touch voltage on the resistivity of soil. Due to the seasonal variations, resistivity of the soil changes, which alters the calculated values of grounding resistance, step voltage and touch voltage. Some times this variation in the resistivity of soil is so wide that it causes the step and touch voltage above the allowable maximum level. Normally special concern to this seasonal factor is not a general concern while designing grounding grid. This article draws an attention towards this least considered but important factor i.e. seasonal factor. Different seasonal situations in this article are analysed by using Electrical design software (EDSA).