Safety design considerations for alternating-current low-voltage distribution systems

Safety criteria, protective device performance, transferred potential hazard, and National Electrical Code (NEC) voltage limits and requirements on equipment grounding practices are examined. Safe step-and-touch voltage criteria are imposed, based on body weight. These criteria are considered for both industrial applications and general applications where children may be present. Although the authors have attempted a logical extrapolation of nonlethal continuous currents versus body weight, it is stated that there is insufficient test data to support the conclusions. It is pointed out the agreement was found between the few values cited in the NEC and the extrapolated values.<>