Computer system for evaluation of shock hazard in circuits with non-sinusoidal earth currents

Effects of current on people are mainly considered for 50/60 Hz sinusoidal current and smooth direct current. However, modern low voltage circuits are very often equipped with power electronics converters - rectifiers, frequency converters, therefore non-sinusoidal earth currents (touch currents) occur. For non-sinusoidal currents safety criteria should be modified. This paper presents a computer system, based on LabVIEW environment, for evaluation of shock hazard in case of non-sinusoidal currents. Waveforms of rectified current, current with phase control and current with mixed frequencies are analyzed. Implementation of the safety system enables the disconnection of supply exclusively when real hazard of the ventricular fibrillation occurs. It can be very useful in electric circuits with high demand for continuity of supply.