4. Designing and sizing an earth network

Figure 37 shows an example of a grounding system for a commercial building. The underground grid is completed by star conductors connected to the lightning conductor's down conductors, which can be up to ten meters long at the four corners of the building. An equipotential bonding grid is used to connect sensitive data processing equipment. The ground equipotential bonding is more finely meshed to provide better protection against higher-frequency EMC disturbances, while the trench bottom is primarily designed to evacuate lightning currents while maintaining equipotential bonding between the various points of the building.