Investigation and Electromagnetic Modeling of Earth Grid Islanding and Its Effect on Touch and Step Voltage Profile Variation Using Finite Element Method

The earth grid at high voltage substations should provide safety for people and normal equipment operation, therefore design calculations should be consideredaccurately. Step and touch voltages are among the items that affect people’s safety at high voltage substations. Grounding is suitable so that in addition to having low electrical resistance to the ground, it does not increase the step and touch voltages. Among the factors that laed to an increase in the electrical resistance of the earth’s grid is the tearing of the earth’s grid due to factors such as corrosion of conductors. In this article we provide a description of the appropriate design of high voltage substations grid to simulate the overhead substation grid and its effect on step and touch voltages in ComsulMultiphysics software based on the finit element method. After performing the simulation,it is noticed  that the stepand touch voltages in the two-and three-piece earth’s grid are much higher than the healthy earth’s grid and about 48 times comparing with the normal grid.