The effects of lightning strikes on earthing or protection systems designed to IEC 62305 can be modelled using an equivalent single frequency from 25kHz up to 1MHz which gives similar results to a time-domain approach. This article provides the frequency and current values to be used for modelling lightning.

Should a metal fence be bonded to the substation earth grid? The metal fences around substations keep people out but they pose earthing safety challenges. These metallic fences, which are easily accessible to the public and personnel, must be adequately earthed and touch voltages on them during an electrical fault must not exceed safe limits.

During an earth fault on a substation earth grid, the flow of current to the earth will produce voltage gradients. An earth grid that is properly designed will safely dissipate current into the ground.

This article shows the effects of soil resistivity and thickness of layers on grid resistance for earthing systems in multilayer soils. Increasing the resistivity of soil layers tends to increase the grid resistance, no matter which soil layer that is. Increasing the thickness of any soil layer with high resistivity also increases grid resistance and if the soil layer thickness is increased for a low resistivity layer then the grid resistance will decrease. Software modelling is performed and the results are compared and shown to match well with those from CDEGS software.

This report shows the effects of a direct lightning strike to an air terminal installed on top of a building which is connected to a buried earthing system.