Optimal ground grid design for large EHV substations with auto-transformer

Abstract

This paper describes hands-on solid modeling experience of the safe optimal ground grid design (less copper) for a large Extra High Voltage (EHV) substation. The optimized ground grid meets the IEEE-80 standards for safety without compromising on step or touch potential thresholds. The ground grid has been designed in CDEGS using fault current flow concepts, and multiple injection points simulate the actual conditions and fault currents at the substation. The method primarily focuses on substation specific data to perform substation grounding studies rather than utilizing the IEEE-80 curves and assuming fault current values. The method is not only conceptually correct and meets safety requirements, but also leads to significant savings of copper. Thus optimizing the ground grid design for the EHV substation.