Abstract
This article presents the results of experimental studies on a coal mine. According to the results, the current of single phase-to-earth fault in the network under 1000 V has a value less than the current of the residual current device set point. This article presents a method aimed to improving the efficiency of the residual current device used on excavators and drill-rings at mining enterprises. Indeed, the method developed to improve the efficiency of residual current devices under 1000 V is based on setting up a direct current into three-phase mains with a fixed set-point of protection against any phase-to-ground insulation damage, where electric equipment is switched off due to increases of capacitance between a conductor and earth when live-line bare-hand touching of electric equipment occurs.