40 MW Photovoltaic Power Plant’s Earthing System Design – New Challenges for an Integrated Methodology

Abstract

EDP Labelec is responsible for the safety analysis of the earthing system of every new substation in the Portuguese distribution grid, and over the past 15 years has developed and perfected an integrated methodology for designing earthing systems. The company has also 30+ years of experience in earthing field measurements, and is responsible for performing almost all earthing measurements in substations from Portugal’s electrical grid. The methodology was described and validated in previous publications.The key goal of this paper is to present the results of the application of this integrated methodology to the design of a 40 MW PV Power Plant Earthing Grid, which was a novelty both for the Portuguese generation park, and for EDP Labelec.To accomplish this, it is described the main steps and challenges of the design work including the soil model conception and validation, the workarounds needed to simulate this large grid in the CDEGS software, the results extraction and analysis and the improvement measures design. Finally, after the PV Plant was built, its earthing impedance and voltage gradients were measured on site and presented in this paper, to validate the results of the study.