Optimized Design of Earthing System for Substations with High Soil Resistivity and Limited Plot Area

Over the past few years, the demand for electrical energy has been increasing rapidly. Consequently, to cater the load requirements, the number of substations being built has been continuously rising. For several technical and safety reasons, electrical power installations must be grounded and the uninterrupted flow of fault current to the earth can be achieved by maintaining the grounding system resistance as low as possible. For a substation with high grounding system resistance, a hazardous situation can be generated in the vicinity of the substation depending upon the level of the potential difference that exists between grounded structures and various points on earth during abnormal or fault conditions. Two of the most critical parameters that influence the design of the grounding system at an electrical substation are the soil resistivity and the area available for laying the grounding system. The main objective of this paper is to present an optimized design of earthing system for a substation located in high soil resistivity with limited plot area at Himachal Pradesh state of India using computer design program. A hybrid methodology for analyzing the performance of a grounding system with chemical ground electrolytic rods, ground enhancement materials and auxiliary wire mats has been developed. The design is based on the measured soil resistivity of the substation site and proposed methodology is found to be safe for operation.