Limit values

The human hazard of electric current depends on the intensity and duration of current flow in a specific current path through the body. The technical specification IEC TS 60479-1 comprises the permissible touch currents and the required data to calculate the permissible touch voltages under several conditions (e.g., body resistance, current path, skin moisture (see Parameters for effects of electric current) for alternating current and direct current.

A touch voltage of 50 V AC (1-1000 Hz) or 120 V DC for long shock duration (> 3 s) should not be exceeded in healthy adults otherwise a life-threatening condition may occur. For children and livestock the touch voltage is limited to 25 V AC or 60 V DC.

In workplaces, higher short-term touch voltages above 50 V AC or 120 V DC are permissible for tasks at energized parts under certain conditions. Only specially trained employees are allowed to carry out the tasks using personal protective equipment and specific safety protection measurements.

Following specifications are valid for example:
  • IEC 60364-4-41:2005. Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock
  • EN 50110-1 ed. 3: 2013. Operation of electrical installations - Part 1: General requirements
  • EN 50122-1 ed. 2: 2015. Railway applications - Fixed installations - Electrical safety, earthing and the return circuit - Part 1: Protective provisions against electric shock