Cable sheath surface discharges and electric shock

ELECTRIC SHOCK HAZARD from the surface of an energized cable is of great importance due to the increasing use of semiconductive jackets. Data were obtained showing the amount of current flowing to ground over a range of “body contact” resistances for nonshielded, metallic-shielded, and “semiconductive” jacketed rubber-insulated cables operating at various voltage levels. The range of currents then was related to known shock sensation levels to assess the amount of hazard involved. A theoretical approach to the voltage rise, surface current, and shock current of cables having different outer surfaces materials helps considerably in understanding the phenomena involved. Calculation of surface voltage rise and current flow can be carried out properly by considering the distributive nature of the cable constants.