Investigations of 3D Meshed Earthing Systems

In a previous contribution [1], vertical earthing rods were used to show how they dissipate currents to the earth and what influence the geometrical arrangement, the installation depth, the length and the earth resistance have on the resistance to earth and partial fault voltages. Results show, depending on the geometry of the rods’ arrangement, individual earthing rods interfere with each other over the in the earth propagating electrical flow field. The difference between the measurement results of the resistance to earth of different rod arrangements in a substation in construction and the calculation results was small. This proves that for power frequency currents a steady-state calculation method is sufficiently accurate for designing earthing systems for usual power frequencies. It was also established that vertical rods are disadvantageous regarding to high partial fault voltages in their immediate area of influence and, with them only,
it is difficult to realise a modern, safe and integrated earthing system. Based on the knowledge gained from [1], in this contribution horizontal electrodes are added and their electrotechnical characteristics, which differ from those of the vertical rods, are discussed. Despite the differences, it is shown how the advantages of both types can be used through appropriate arrangement and galvanic connection.