|Earth Leakage Circuit Breakers (ELCB’s)
also known as Residual Current Detectors (RCD’s), are
compulsory in all new homes and most industrial sites in Australia,
their function is to detect spurious or accidental current flow
returning to the Earth conductor and to rapidly isolate the
power in that circuit. The prime purpose of the protection is
to prevent and protect against accidental electrocution to protect
human life, where connected equipment may be faulty, cords frayed
or wiring insulation compromised. (Or if we believe the advertising,
the spectacularly stupid event where a hair dryer is used under
the shower, or an electric bar heater is rested on the side
of a bath).
The ELCB protects by monitoring the Active to Earth and Neutral
to Earth of the protected power circuit, by returning spurious
voltage and current through a pair of protection solenoids.
If sufficient current flows through either solenoid, the solenoid
activates and a switch opens to isolate the circuit, which
latches and remains isolated until manually reset (and fault
Most electrical devices leak some level of residual current
(rules apply to govern the acceptable level), therefore ELCB’s
should be installed with consideration for the ambient level
of residual current in the protected power circuit. Incorrectly
set ELCB’s can sometimes activate if there is insufficient
ambient allowance when new appliances are added to an installation.
For effective protection against Spikes and Transient Noise,
reaction times of less than 5NanoSeconds are required, slower
reaction times are not effective. Due to the mechanical nature
of the switching of ELCB’s these required very fast
reaction times are not readily achievable by the technology
Further, consider that as ELCB’s are designed to monitor
and protect only on the Common Mode (Active/Earth and Neutral/
Earth) they are not designed to monitor the Differential Mode
(Active/Neutral, otherwise if monitoring across the supply
(Active/Neutral) when you switched an appliance on, the ELCB
would switch the power off).
Professional Series Filters and PowerGuard protect on all
three conductors, are purpose built appliance protection and
operate a minimum of 300,000 times faster than ELCB’s.