How are people electrocuted?
Figures vary from year to year for each country, but global statistics reveal that electrocution is one of the top five causes of death at work.There are many electrical shock accidents in the home, and electrical accidents cause several hundred deaths and several thousand injuries each year in a single country.
How and why do people get an electric shock?
Essentially, as leakage current equipment is accidentally touched or when an electrical appliance fails in such a way that its exposed metal parts temporarily become conductive and dangerous. Many appliances have fuses to protect against excessive currents, but it does not help in the leakage current situation. Some appliances also have “ground” or “ground” wires to protect us when the wires touch things they shouldn’t.
The “ground” or “ground” is not part of the normal power circuit, it is just a replacement wire connected to the exposed metal parts of an appliance. It eventually connects to the ground through your home wiring, then through a metal spike or water pipe that enters the ground outside your home.
The basic idea is that if the live wire fails and touches something like the metal outer casing of a toaster, then the metal distribution box, the ground wire carries the current safely. But what if the ground / ground wire fails the same way? The circuit will pass through your body, how to protect yourself against electric shock? That is where RCD, GFCI, ELCB come to our rescue.
The RCD consists of five parts, there is a Magnetic Relay (1), Mechanism (2), Input Line Terminals (3), Load Terminals (4), and Sense Coil (5).
The active wire connects the incoming line terminal (1) and connects to your electrical appliances from the load terminals (4), to turn on the mechanism handle (2), to make the connection of copper contact parts of the incoming line terminals (3) and the sense coil (5).
The sense coil is a residual current transformer that surrounds (but is not electrically connected) the active and neutral conductors. In normal operation, all current downstream of the live conductor returns to the neutral conductor. The currents in the two conductors are therefore equal and opposite and cancel each other out.
Any fault in the ground (for example, caused by a person touching a live component in the connected device) causes some of the current to take a different return path.
This means that there is an imbalance (difference) in the current in the two conductors (single-phase case), or more generally, a non-zero sum of currents between several conductors (for example, three phase conductors and a neutral conductor). This difference causes a current in the detection coil (5), which is picked up by the magnetic relay (1).
The sensing circuitry then removes power from the mechanism (2) and the input line terminal contacts (3) are forced apart by a spring, cutting off the supply of electricity to the apparatus.
The RCD is designed so that current is interrupted within milliseconds, greatly reducing the chances of a dangerous electrical shock being received.