Circuit representation of coupled earthing grids

This paper is focused on the design concept of earthing system composed of two earthing grids in close vicinity of each other. The “vicinity” means that the distance between the investigated earthing grids of the power plant and the switching stations is comparable with the sizes of the earthing grids. As a consequence the earthing grids are in the zone of each-other earth potential rise (EPR).To represent the coupled earthing grids the elements of an equivalent delta impedance system are determined by a sophisticated earthing and soil structure analysis technique. Detailed analyses are performed on the bases multi-conductor line simulation. This results in the currents injected by the interconnections between the grids and the grid EPR. Finally the voltage distribution and the step voltages are computed by the use of the mentioned sophisticated technique again. This process is demonstrated by numerical results of a case study.