RE: Residual current circuit breaker
||Residual Current Circuit Breaker
Introduction – Residual Current Circuit Breaker / ELCB
The Fault current overloads and short circuits
can be detected by circuit breakers like MCB’s
MCCB’s & HRC Fuses etc. But, Circuit
breakers don’t detect leakage currents, which
are dangerous for humans and livestock and if
not detected can lead to fire hazards. We need
a solution that detects such leakages currents
and disconnects the circuits from the power
supply. Here comes the solution in the form of
RCCB (Residual Current Circuit Breaker) also
known as ELCB (Earth Leakage Circuit
Breaker) which provides protection against
direct and indirect contact of personnel or
livestock and against probable fires.
• Use of special magnetic materials for the toroidal core balance transformer and a specially
developed highly sensitive miniature relay ensure positive detection of earth leakage currents
as low as 30mA in less than 40 milli seconds thereby acting as a life saver. All the RCCB's are
protected from nuisance tripping against transit voltages (lighting, line disturbances...) and
transient currents (from high capacitive circuits).
• STOP SHOCK RCCB's are housed in high quality thermoplastic insulating material. The
materials used are fire retardant, anti tracking, non-hygroscopic, impact resistant and can
withstand high temperatures.
• The moving contacts of the phases are put on a moving arm, actuated by a rugged toggle
mechanism. Hence the closing and opening of all the phases occur simultaneously. This also
ensures simultaneous opening of all the contact under automatic tripping conditions.
• STOP SHOCK RCCB's incorporate advanced neutral i.e. neutral makes ahead of phases and
breaks after phases, which ensures complete discharge of line inductance and capacitance. (It
also has safe interrupting clearances as per IS: 13947-1. These two provisions make STOP
SHOCK RCCB an ideal selection as main switch.)
• ON & OFF Positions is clearly visible with the help of window provided at the top of housing.
The green colour indicates the OFF position and red colour indicates the ON Position.
• Mechanism components are made of plastic which are of high-quality, high-strength, low
inertia and self lubricating properties. This results in a very fast opening action of the device
under fault conditions. Though the moving components of the mechanism are made of plastic
for friction free and smooth operation, load bearing parts of mechanism are made of highstrength
steel thus the combination resulting in making the mechanism more sturdy.
• RCCB’s relay draws the energy from the residual current which it needs to trip the RCCB
that’s why it can still operate normally if the mains voltage drops or if the neutral wire is
interrupted, even a relatively long period of over voltage resulting from a fault current in the
mains can’t destroy RCCB or interfere with its normal operations.
• The ever increasing use of rectifies, particularly in the mining industry, requires safety
measures against fault current which will also safety detect and respond to AC residual
currents with a frequency of 50Hz to smooth DC residual currents. This so-called universal
sensitivity which can only be achieved with auxiliary voltage-dependents circuit breakers, i.e
Equipments likely to emit smooth DC residual currents may only be used outside house
instillations and it may not be operated downstream of ‘normal’ RCCB’s to which other circuits
are connected. In the events of a residual DC current arising, the RCCB’s operation could be
impaired and it might not even trip if a residual current occurs simultaneously at another
electrical equipments. In order to be able to ensure selective protection against direct and
indirect contact, professional bodies are increasingly demanding that AC-DC sensitive devices
be employed. Our devices are designed and constructed to IEC 1008 / IS: 12640 – 2000.
They will respond to residual currents from smooth DC currents to 400Hz AC and pulsating
currents and provide extremely high operational reliability. These RCCB’s are available in
selected rating only.
Additional Protection Against Pulsating Fault Currents.
While the tripping of residual current circuit breakers with pure alternating fault currents was usual and
adequate in the past, these can only be used conditionally in modern electrical installations. With light
controls, speed controls etc. pulsating forms of current increasingly occur also as fault currents as a result of
the use of electronic components. In order to tackle such pulsating direct fault currents which tend to zero or
almost zero within every period of the mains frequency at least for half a period, 'A' type of RCCB's are
suitable. Type A is more sensitive than AC type. It covers all requirements of AC type plus it is pulse current