Earthing rods improve earthing systems when driven into low resistivity soil layers. Due to the proximity effect the rule of thumb is earth rods should be separated by at least their driven length. Rods may be encased in concrete to lower their resistance. Equations are provided for hand calculations and these have been validated with numerical software.

Key earthing design concepts covered including Grid Potential Rise, design to reduce touch and step voltages, fault current distribution, effects of soil resistivity and use of rods to improve safety along with calculation and modelling examples.

Provides test procedures based on the fall of potential method and actual touch and step voltage measurements for the purpose of validating a safe earthing design. Includes procedures for both large or small earthing systems, safety requirements (for undertaking the tests) and recommended testing equipment.

There are two reasons, according to the standards, why crushed rock or gravel is laid in substations, as explained in this article.