Parameters Effecting Substation Grounding Grid Resistance

One of the key parameters in substation grounding design is to calculate accurately the grounding resistance of the system. The substation grounding grid resistance to be used to design a safe grounding system has been receiving a lot of attention in recent years. It is important that the substation ground has a low ground resistance, adequate current carrying capacity, and safety features for personnel and equipment. A good grounding system provides a low resistance to remote earth in order to minimize the GPR. For most transmission and other large substations, the ground resistance is usually about 1 Ω or less. In smaller distribution substations, the usually acceptable range is from 1 Ω to 5 Ω, depending on the local conditions. In this paper the various parameters affecting the calculation of substation grounding grid resistance is briefly explained.