Residual Current Devices

One of the most significant advances to safety in the electrical industry in the past 30 years has been the adaptation of residual current devices to installations. Residual current devices, otherwise known as RCD’s or safety switches, are devices that detect the flow of current through an active terminal within a circuit and compare that to the current returning through the neutral conductor. If there is a difference in these two values, the switch trips to stop the flow of electricity.

This all might sound a bit technical so to make it easier to understand try to imagine the flow of electricity through a cable like water flowing through a pipe. As the water flows through the inlet valve it is measured to record the volume that is flowing through that valve. From here it makes its way around a circuit of pipes and eventually goes through an outlet valve. At this point the volume is then also recorded. If there is a difference in the two volumes recorded there is obviously a leak in the pipes somewhere down the line.

The same goes for electricity. If the recorded current that returns through the neutral conductor of the circuit differs to what has been drawn through the active conductor we can conclude that there is a fault at some point in the circuit that is leaking current. A good example of this is an old appliance like a toaster. If there has been a breakdown in the insulation of the conductors at some point in the circuit, this can cause a live conductor to be touching the body of the appliance. If this body happens to be a conductor itself (such as metal) it too will become live. If somebody was to touch the frame of the appliance, then that persons body can also become a conductor for the flow of electricity back down to earth. In other words this can quite easily cause and electric shock and in some cases fatal electrocution.

Luckily with the introduction of RCD’s the number of electric shocks and fatalities has dramatically decreased. In Victoria the use of safety switches for any power circuit became mandatory in 1991. This was also changed to include lighting circuits in 2000.

Like anything, RCD’s do have a life span and will not last forever. One of the conditions of a properly functioning safety switch is that depending on what type, it will have a time limit on how long it takes to trip under fault conditions, and also an allowance on how much current leakage it will allow before tripping. Because of this there are tests that can be performed by a licensed electrician to ensure that RCD’s are working efficiently and effectively.

If you need RCD’s installed or tested in your house or business, or if your switchboard needs a full upgrade, don't hesitate to call Ben on 0421 863 309 for an obligation free quote. You might be pleasantly surprised at how affordable it is to make safety a priority.