TN-Island Grounding System and the House of the Future

Low voltage, single-phase residential loads are usually supplied by the local utility, through a common distribution system (CDS) in a radial layout. In US and UE typical distribution systems, a faulted dwelling unit can affect a healthy one by transferring ground rise potentials, sometime dangerous. The authors propose a novel system defined as TN-island grounding system with the adoption for each customer of a local transformer (LT) with taps, grounded at the mid-point of the secondary winding, supplied by a common distribution system with the neutral grounded but not distributed. This solution allows to reach several goals: - to elevate the immunity of dwelling units, - to stop potential rises, due to ground faults, and of circulation of stray currents - to balance the distributed capacitance-to-ground - to limit the triplen current harmonics naturally caused by the LT - to supply more customers and locally high power common loads HPCL of buildings - to organize common emergency system (UPS and generator sets), common power system management, loads shedding, etc. Moreover, for special conditions (i.e. swimming pool, medical rooms, damp houses), the use of local transformers LTs allows to adopt proper reduced voltage system recommendable owing to the lower value of touch voltage and to adopt further local ungrounded system (IEC IT-system)