Switch on ‘safety’ measures
A safety switch is an electrical safety device which is specially designed to immediately switch off the electricity when electricity ‘leaks’ to earth at a level harmful to human. This device offers a high level of personal protection from shock.
Safety switch is general name for a residential current device (RCD) or earth leakage circuit breaker (ELCB). These work on the principle of ‘what goes in must come out’.
They operate by continuously comparing the current flow in both Active (supply) and Neutral (return) Conductors of Electrical Circuit.
If some of the current in the Active Conductor is not returning through the neutral conductor it is leaking to earth.
Safety switch typically operate within 10 to 50 milli-seconds and disconnects the electric supply when they sense harmful leakage current, usually 30 milliamps. The sensitivity and speed of disconnection are such that any earth leakage current will be immediately detected and automatically switched off before it can cause injury or damage. Miniature Circuit Breakers and fuses provide equipment or installation protection and operate in response to an electrical overload or short circuit when high fault currents flow.
Short circuit flow to earth via your installation’s earthing system causes either the MCB to trip or blow up the fuse, disconnecting the electricity from the fault circuit.
However, if the electrical resistance in the earth fault current path is too high to allow the MCB to trip or fuse to blow, then electricity can continue to flow to earth for an extended time, creating dangerous voltages and currents. Safety switches can detect a very low level of electricity flowing to earth and immediately switch the electricity off.
N.A. LOKESH KUMAR
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