APPLICATION OF A NOVEL COST-EFFECTIVE EARTHING DESIGN SOLUTION FOR SWITCHING STATIONS WITH HIGH SHORT-CIRCUIT POWER, USING AN INTEGRATED METHODOLOGY

During the last years, EDP Labelec's integrated methodology for designing earthing systems has faced some important challenges, namely regarding the design of earthing grids for smaller outdoor facilities, especially switching stations. Their small footprint area, which limits the earthing grid area, high short-circuit design power, high resistivity soils, and poor current splitting factor, may ultimately lead to almost unfeasible and expensive earthing system designs, comprising dozens of long vertical electrodes. The key goal of this paper is to present the motivation and results of the application of EDP Labelec's integrated methodology to one of these cases, developed in partnership with GENERG and E-REDES, while exploring the use of a novel cost-effective design solution, to reduce the use of copper electrodes by a very large margin. This design solution comprises the use of steel mesh reinforced concrete pavements and plastic insulated fences. For this case-study switching station, this solution results in very significant savings in the number and length of copper electrodes, totalling a net saving of 32.8 k€, while maintaining the same, or even higher level of safety of people, regarding touch and step voltages. After the construction, touch and step voltages were measured on-site, confirming and validating the design solution.