In the Electrical Engineering field,many cases of accident or death around the world causes by electric shocked.It very dangerous because we cannot see,smell and feel the electric current.
Current flow into our body and can make heart stop from functioning and can cause the serious injury even death.The level of danger for electric shock depends on the value of the body current and the time for which the current flows.
Human body have a different insulation value (Ohm) and also different current value can effected the heart.For the body have a low current level,it can easily attack the heart function and it so dangerous.
That why we must take a necessary action to prevent the electric shock such as wear protection equipment,Insulated hand tools (VDE) and protection device for electrical installation likes RCCB and MCCB.
For wiring installation,earthing cable is compulsory item.The main purpose is to reduce the amount of current available for passage through the human body when short circuit or electric shock happen and can save human life.
Below is graph for current value that can effected human when electric shock happen.The figure shows the time/current zones of effects of 50 Hz current on the human body.
Description of Electric shock
- Zone 1 – No sensation
- Zone 2 – Perceptibility of current, but no harmful effect (10 mA is the threshold of let-go)
- Zone 3 – Muscular contractions and difficulty in breathing. Usually no danger of ventricular fibrillation (0.5%probability)
- Zone 4 – Probability of ventricular fibrillation increases ( a : up to 5% , b : up to 50% , c : greater than 50% )
What happen when electric current flow to our heart?
Theoretically when electric current flow to heart,it can effected to Ventricular fibrillation of the heart.It can prevention of the heart to function as an effective pump system, and immediately causing a blood circulation shortage to all parts of the body.The serious effected is death in a very short time.
From the graph,we seen that a current of 30 mA never goes into zone 4, and is thus typically used in residual current devices used for safety purpose to protect human from electric shock.
The safe voltage value is 50 VAC and it cannot effected to human heart or part of body.The important key is ” SAFETY FIRST ” when perform electrical jobs.