Electric shock

When a current exceeding 30 mA passes through a part of a human body, the person concerned is in serious danger if the current is not interrupted in a very short time.

The protection of persons against electric shock in LV installations must be provided in conformity with appropriate national standards statutory regulations, codes of practice, official guides and circulars etc.

Relevant IEC standards include: IEC 60364, IEC 60479 series, IEC 61008, IEC 61009 and IEC 60947-2.

An electric shock is the pathophysiological effect of an electric current through the human body.

Its passage affects essentially the muscular, circulatory and respiratory functions and sometimes results in serious burns. The degree of danger for the victim is a function of the magnitude of the current, the parts of the body through which the current passes, and the duration of current flow.

IEC publication 60479-1 updated in 2005 defines four zones of current-magnitude/time-duration, in each of which the pathophysiological effects are described (see Fig. F1). Any person coming into contact with live metal risks an electric shock.

Curve C1 shows that when a current greater than 30 mA passes through a human being from one hand to feet, the person concerned is likely to be killed, unless the current is interrupted in a relatively short time.

The point 500 ms/100 mA close to the curve C1 corresponds to a probability of heart fibrillation of the order of 0.14%.

The protection of persons against electric shock in LV installations must be provided in conformity with appropriate national standards and statutory regulations, codes of practice, official guides and circulars, etc. Relevant IEC standards include: IEC 60364 series, IEC 60479 series, IEC 60755, IEC 61008 series, IEC 61009 series and IEC 60947-2.

AC-1 zone: Imperceptible
AC-2 zone: Perceptible
AC-3 zone: Reversible effects: muscular contraction
AC-4 zone: Possibility of irreversible effects
AC-4-1 zone: Up to 5% probability of heart fibrillation
AC-4-2 zone: Up to 50% probability of heart fibrillation
AC-4-3 zone: More than 50% probability of heart fibrillation
A curve: Threshold of perception of current
B curve: Threshold of muscular reactions
C₁ curve: Threshold of 0% probability of ventricular fibrillation
C₂ curve: Threshold of 5% probability of ventricular fibrillation
C₃ curve: Threshold of 50% probability of ventricular fibrillation

Fig. F1 – Zones time/current of effects of AC current on human body when passing from left hand to feet