8.1 Soil Resistivity 8.1.1 The resistance to earth of a given electrode depends upon the electrical resistivity of the soil in which it is installed. This factor is, therefore, important in deciding which of many protective systems to adopt. The type of soil largely determines its resistivity and examples are given in Table 3. Earth conductivity is, however, essentially electrolytic in nature and is affected, by the moisture content of the soil and by the chemical composition and concentration of salts dissolved in the contained water. Grain size and distribution, and closeness of packing are also contributory factors since they control the manner in which the moisture is held in the soil. Many of these factors vary locally and some seasonally so that the table should only be taken as a general guide. Local values should be verified by actual measurement, and this is especially important where the soil is stratified as, owing to the dispersion of the earth current, the effective resistivity depends not only on the surface layers but also on the underlying geological formation. It should also be noted that soil temperature has some effect (see 8.7), but is only important near and below freezing point, necessitating the installation of earth electrodes at depths to which frost will not penetrate. It is, therefore, recommended that the first metre of any earth electrode should not be regarded as being effective under frost conditions. While the fundamental nature and properties of a soil in a given area cannot be changed, use can be made of purely local conditions in choosing suitable electrode sites and methods of preparing the site selected to secure the optimum resistivity. We, at Atul Casting and Metal Works manufactures all earthing related products such as G.I Strips, G.I plates, G.I Rods, G.I Pipes, C.I covers, Cable Trays, G.I Wire, Manhole Covers and Route Markers for past 50 + Years in heart of New Delhi. Call us at +91 9873361672 for best deals.