Parametric changes of grounding system for high voltage substations

Design of grounding system plays crucial role in the high voltage substations. It is challenging to design a safe economical grounding system as there are a number of design related parameters. The grounding system is very important for the normal operation of the power system and the safety of the equipment and personnel. Usually, the grounding grid design is carried out with the aim of meeting the safety restrictions while minimizing its cost. A well designed substation grounding grid is extremely important part of the power system. The fault conditions in a substation can produce huge damages to transformers, circuit breakers and other substation equipments if grounding system is not designed properly. It is important that the substation ground should have a low ground resistance, adequate current carrying capacity, and safety features for personnel and equipment. The design of grounding system for high voltage substations is influenced by several factors like soil resistivity, maximum fault current, conductor selection, conductor sizing and grid resistance. The effects of heat, moisture, drought and frost can introduce wide variations in normal soil resistivity. Soil resistivity usually decreases with depth, and an increase of only a few percent of moisture content in a normally dry soil will markedly decrease soil resistivity. Conversely, soil temperatures below freezing greatly increase soil resistivity, requiring earth rods to be driven to even greater depths. This study will briefly explain soil resistivity, conductor material, and ground mat, getting into earth and driving methods.