Practical Considerations for Design, Operation, and Maintenance of Grounding Systems in Electrical Substations: Impact of Surface Layer Contamination in Crushed Stone

This article addresses the significance of maintaining the efficiency of the surface layer made of crushed stone in electrical substations. It emphasizes that this layer effectively increases the contact resistance between the ground and a person's feet due to its higher resistivity compared to most soils. This characteristic allows for a greater spacing between the conductors of the grounding mesh, resulting in reduced copper usage without compromising safety standards for step and touch voltages. However, it raises a cautionary note about the potential degradation of the surface layer over time, caused by contamination from dust, sand, and the accumulation of soil within the rock crevices. Such deterioration would lead to a decrease in the effective resistivity of the surface layer, potentially resulting in lower tolerable step and touch voltages. Consequently, this poses safety risks for personnel in the event of a ground fault. The article proposes methodologies for inspecting and assessing the current condition of substations concerning the degradation of the surface layer's effectiveness. Moreover, it suggests additional design considerations beyond the guidelines provided by Std. IEEE 80[1] to account for this particular issue.