Discuss Automatic disconnection of supply in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
..Only any good with 230-250V AC. to earthWell I would like to know the science behind how it saves your life if it doesn't limit the current your body receives
A current limited power supply and not really much else...But it states you can achieve it by reducing the current to a non hazardous level I would like to know how, and if an RCD can't do it what can
Rcds are advertised to operate at 30ma but they are actually manufactured to function at 27 to 28ma. Manufacturers hedging their bets on that one30mA RCDs are designed to trip when they detect earth leakage greater than 30mA.
Most will trip below this figure.
So if an RCD detects an earth fault current of 4600A, it will trip, and it will trip within 40ms.
An MCB will also trip if it detects a fault current of 4600A, though it is more likely to trip instantaneously or within 10ms.
Where RCDs are good, is that they will trip at lower currents which an MCB might not trip at, or may take seconds, minutes, hours or even days to trip.
So no, RCDs do not limit fault current, just as fuses and MCBs don’t limit fault current.
Never ever assume an rcd will save your life from being killed.Well I would like to know the science behind how it saves your life if it doesn't limit the current your body receives
An RCD functions to disconnect before most fatal events occur in accordance with the below graph, the disconnection time is such that the human body should be able to withstand the expected fault current flowing through the body for that duration without death, but not without pain and reaction, in most cases.
- Preventing a current passing through the body of any person or any livestock
- Limiting the current which can pass through a body to a non-hazardous value
Wise because I'm a fireman
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