New method for step and touch voltages verification by continuous loop impedance monitoring

This paper outlines a strategy for monitoring earth loop impedance and ensuring compliance with step and touch voltage limits in distribution networks using insulated cables with monitoring systems. These voltages, regulated by EN 50522 [1] and national laws such as Spain's Royal Decree 337/2014 [2], must be measured during commissioning tests and verified periodically. In medium-voltage (MV) networks of up to 36 kV, step and touch voltage measurements can be replaced by earth resistance measurements if a validated correlation exists. Loop impedance measurements, conducted with current injectors (frequencies < 2 kHz), allow the estimation of the earth resistance of transformer station (connected through insulated cables. Compliance with step and touch voltages strongly depends on the fault current distribution at each transformer station, influenced by the earth resistances of other interconnected stations. Using the current distribution coefficient (α), various scenarios of network topology and neutral earthing systems are analysed. The objective is to correlate the loop impedance with a fault current distribution coefficient, enabling the estimation of confident upper limits for step and touch voltages, thereby verifying compliance with safety voltage requirements in distribution networks [2], [3],[4].