Safety Analysis of TN-S and TN-C-S Earthing System

This paper presents safety analysis of TN-S and TN-C-S earthing system considering different sizes of cable and protective earthing conductor (PEC). For this purpose, touch voltage and electric shock calculations are presented. In TN-C-S system, even with the main protective bonding (MPB) and in TN-S system in spite of local grounding at consumer end, computed touch voltages are quite high and thus unsafe for human. Therefore, to safeguard the persons against dangerous touch voltages in both the earthing systems, novel way of protection that is bonding of grounding grid to the exposed conductive part (ECP) of consumer load is proposed in this paper. Also, grid augmentation is investigated for hazardous step and touch voltages. Based on the two cases, that is with and without bonding the ECP of load to grid, touch voltage assessments are done. The results show that with bonding, touch voltages are reduced substantially. Therefore, safety and reliability of the systems are ensured.