4. Soil Preparation
Soil resistivity is an important consideration in substation grounding system design. The lower the resistivity, the easier it is to get a good ground resistance.
Areas of high soil resistivity and those with ground frost (which inturn causes the soil resistivityto increase by orders of magnitude) need special consideration. The highest ground resistivity during the annual weather cycle should form the basis of the design since the same soil will have much higher resistivity during dry weather when percentage of moisture in the ground becomes very low.