Improve Earthing Resistance:
- Use longer ground rods
- Chemically treat the soil
- Use multiple ground rods
Effects of multiple ground rods:
Two well-spaced rods driven into the earth provide parallel paths. They are, in effect, two resistances in parallel. The rule for two resistances in parallel does not apply exactly; that is, the resultant resistance is not one-half the individual rod resistance. Actually the reduction for two equal resistance rods is about 40 percent. If three rods are used the resistance is 60 percent; if four 66 percent.
Treatment of the soil:
Chemical treatment of the soil is a good way to improve earth electrode resistance. Chemicals which are non-corrosive should be used for the treatment. It should be noted that soluble sulphates attack concrete and should be kept away from building foundations. Another popular approach is to backfill around the electrode with a specialized conductive concrete.
Chemical treatment is not a permanent way to improve earth electrode resistance. The chemicals are gradually washed away by rainfall and natural drainage through the soil. Depending upon the porosity of the soil and amount of rainfall, the period of replacement varies.