6 - Ground electrode system

Abstract

This chapter describes the design of grounding system, and the materials used for this purpose. The practices adopted in different countries follow the national standards/codes that are specified by the appropriate authority, and hence, can be significantly different. The chapter limits the discussion to the general principles involved in the design of earth electrode system. It gives specific examples of electrode system design. The chapter also discusses the methods of measuring the resistance of grounding systems. The details of soil resistivity and its measurement are examined by the chapter. It also reviews the methods to estimate the grounding resistance of single and multiple electrodes. It discusses the measurement of ground electrode resistance and the need for limiting the ground current flow to prevent smoking electrode phenomenon. The improvement of the soil to obtain better conductivity by using conducting salts and bentonite clay is also covered by the chapter. It also briefly covers the corrosion of ground electrode systems and the ways of preventing the same. The chapter discusses various tables that are of assistance in designing grounding systems. These along with any applicable local codes may be deployed to ensure that the grounding system will function correctly and fulfill its primary purpose of achieving human safety. Standardized ground electrode systems recommended by some national standards and procedure for measurement of electrode resistance are also explained in the chapter.