This document discusses ground grid systems used in substations. Ground grids are used to carry and dissipate currents from events like lightning strikes and faults. They help ensure human and animal safety and allow protective relays to operate properly. Designing an effective ground grid involves analyzing soil resistivity, sizing the grid area, determining fault currents, and ensuring touch and step voltages meet safety limits. Common design methods include the IEEE empirical method and finite element analysis to model grid performance.