Safety evolution of residential microsystems

Utilities typically supply low-voltage, single-phase residential units using a radial layout, which constitutes a common distribution system for the dwelling units. In typical US and EU distribution systems, a faulted unit may affect the healthy ones within the same distribution system, due to the transfer of ground potentials, sometime dangerous for magnitude or persistence. Ground potentials appear during a fault over the building grounding system (BGS), via the PE, if present, and via the common extraneous-conductive-parts (EXCP). In Europe, TT system is imposed to residential units and the PE is not permitted to be connected to the utility neutral wire at the service entrance of the building. Some of the European utilities, in fact, cannot guarantee the continuity, as well as the absence of potentials, of the neutral conductor, which serves, indeed, many users. © 2012 IEEE.