Articles: Earthing Design

Summary The performance of buried electrical earthing systems is highly connected with the resistivity of the soil and these resistivity values vary with the environmental

Table of Contents Overview Solar farms can cover large areas (up to tens of square kilometres) which presents both safety and economical challenges for design

Introduction Fences around substations are essential to keep people safe and most often, these fences are metallic, due to economics, which poses some earthing safety

Concrete is hygroscopic which means it absorbs water and when concrete is buried, depending on the moisture levels at the time of the surrounding soil,

Direct lightning strikes to substations causes physical damage and poses hazards for people.

Using bentonite to reduce resistance Sometimes it is not possible to achieve the desired reduction in ground resistance by adding more grid conductors or ground rods. An alternate solution is to effectively increase the diameter of the electrode by modifying the soil surrounding.

The Annex H in IEEE Standard 80-2013 contains benchmark case results for comparing and evaluating software tools and methodologies used for the analysis of substation earthing.

The results compare the simple equations from IEEE Std 80 with the results given by some of the commercially available software such as CDEGS, ETAP, SGW, SDWorkstation and WinIGS.

Testing of earthing systems enables confirmation of the design values and safe operation in the case of a fault condition according to the applicable safety standards and criteria.

This tutorial introduces key concepts used in the design of substation earthing/grounding systems. Important terminology is discussed including Grid Potential Rise, touch and step voltages and current distribution.