Touch voltage analysis in low-voltage power systems studies

The touch voltage analysis in low-voltage installation, i.e. the calculation of magnitudes and durations of touch potentials, is not normally included in standard power systems studies. And this analysis is of paramount importance for the protection of persons against electric shock in the event of failure of basic insulation of equipment or of direct contact with live parts. Even in correctly designed and erected installations the risk of electric shock is present and its amount can only be quantified through the determination of the exposure to touch voltages. This paper will provide equivalent fault-loop circuits and application formulae for the determination of touch voltages, in light of permissible safe values as calculated per IEEE and IEC standards. These authors support the importance and necessity of the touch voltage analysis as a fundamental component of the “Designing for Safety” approach, and propose their inclusion in system studies as a routine procedure, as it is similarly done for arc flash incident energies calculations.