Topology Measurement Of Substation's Grounding Grid By Using Electromagnetic Field And Derivative Method

Grounding grid is the main element of grounding system that provides low resistance path for short circuit and lightning currents into the earth and prevents surface potential out of bounds. This grounding grid is buried inside earth and is made up of metal or metal alloys. With the passage of time the metallic material of grounding grid is corroded due to the presence of water and porous nature of soil(soil corrosion). The corroded grounding grid is resistive to the flow of current, inefficient and dangerous for the electrical equipment and personnel working in a substation.The topology of grounding grid is important to diagnose its status, which plays a critical role in the safety of personnel and stable operation of power system. Without knowing the topology of grounding grid it's difficult to diagnose its status. In some cases due to human error the drawing of the grid is either lost or so much spoiled that it becomes hard to identify the topology. Since excavation is costly and time-consuming methods are to be developed to identify the topology of the grid.The electromagnetic field and derivative of surface magnetic flux density on the line has been used to measure the branch position in case the grid is parallel to the plane of earth surface that in practice is unknown while the node points and connections between parallel adjacent nodes were not discussed.This thesis uses the same electromagnetic field and derivative method that is taking derivative of surface magnetic flux density on circles and lines in a systematic order to measure the location of the grid in the plane of earth surface and connecting the nodes to measure the full topology. Derivative of surface magnetic flux density on circle contributes to measure the location of the grid and to verify connection between two parallel adjacent nodes while derivative on line contributes to measure branches locations, which are then arranged in ordered pairs to find node points. This method even identifies any angled branch present in a mesh of the grid by taking derivative of surface magnetic flux density on circle. Software simulations and experimental test verify that the method is feasible and can be applied to identify the topology of a grounding grid.