Tuesday, September 2, 2008


Residual Current
Circuit Breakers
The fault current during 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 leakage currents and disconnects the
circuit 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.
Stop Shock RCCB's.
Domestic and industrial use Residual Current Circuit Breaker.
Available in 2 Pole and 4 Pole .
Prevents shocks caused by earth leakage which could be fatal.
As per the Rule 61A of the Indian Electricity Rules 1956, the supply of energy to following
installations shall be controlled by the earth leakage protective devices so as to
disconnect the supply instantly on the occurrence of earth fault or leakage current.
Installations having load above 5 kW.
Luminous Tube Installations.
X-Ray machines .
Used for Single phase electrical connections, mostly for domestic purposes.
Used for three phase electrical connections, for industrial and commercial purposes.
As per Government of India Gudget notice, the RCCB's must have ISI mark in India.
Selling of non ISI RCCB's in India is prohibited.
2 Pole
4 Pole
Salient Features
l 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).
l 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
l 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
l 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.)
l ON & OFF position 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.
l Mechanism components are made of plastics 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 plastics for friction free and smooth
operation, load bearing parts of mechanism are made
of high-strength steel thus the combination resulting in
making the mechanism more sturdy.
l 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 form a fault current in
the mains can't destroy RCCB or interfere with its
normal operation.
l The ever increasing use of rectifiers, particularly in the
mining industry, requires safety measures against
fault currents which will also safely detect and
respond to AC residual currents with a frequency of 50
Hz to smooth DC residual currents. This so-called
universal sensitivity which can only be achieved with
auxiliary voltage-dependent circuit breakers, i.e.
'DI' devices.
Equipment likely to emit smooth DC residual currents
may only be used outside house installations and it
may not be operated downstream of 'normal' RCCB's
to which other circuits are connected. In the event 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 equipment. 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 residual currents to
400 Hz AC and pulsating currents and provide
extremely high operational reliability. These RCCB's
are available in selected ratings only.
l RCCB's are provided with an ARC chamber
consisting of arc-chute. The arc chute quenches the
arc faster, which further increases electrical contacts
l STOP SHOCK RCCB's are life saving devices and
hence, incorporate a test button 'T' for periodic
checking of the mechanism and functions of the
l Apart from suitability to copper cables the terminals
are suitable for aluminum cables from 1 to 25 sq mm.
l STOP SHOCK RCCB can be easily mounted on a
standard DIN Rail of 35 mm. Furthermore, operation
of the RCCB is independent of mounting position.
Supply connections can be terminated either from top
or bottom.
l STOP SHOCK RCCB's have been completely type
tested at CPRI/ERDA in accordance with IS : 12640-
1-2000 and is ISI marked.
Principal of Operation
Residual current protection in the event of indirect contact
RCCB works on the principle that in an electrical circuit the
incoming current is the same as out going current as shown in the
diagram. RCCB incorporates a core balance transformer having
primary and secondary windings and a sensitive relay for
instantaneous detection of fault signal. The primary winding lies
in series with the supply mains and load. Secondary winding is
connected to a very sensitive relay. In a faultless situation, the
magnetizing effects of the current carrying conductors cancel
each other out. There is no residual magnetic field that could
induce a voltage in the secondary. During flow of leakage current
in the circuit an imbalance is created in the circuit which gives
rise to leakage flux in the core. This leakage flux generates an
electrical signal that is sensed by the relay and it trips the
mechanism thereby disconnecting the supply.
When pressing the TEST button 'T', a fault is simulated via the
test resistance & RCCB trips.
To ensure that the RCCB switches off the protected circuit
immediately. If there is an insulation fault causing a short-circuit
to an exposed part (frame etc.) of machinery and equipment
(protection against indirect contact), the maximum permissible
touch voltage U must occur at a residual current greater than or T
equal to the rated residual operating current I that triggers the ?n
RCCB. This condition is met by earthing the exposed part with a
sufficiently low resistance to earth R . E
Earth Resistance R < Touch Voltage U E T
Rated Residual operating current - I?n
The maximum values of R for touch voltages of 25V, 50V & 65V E
are given in the specification tables.
I +
Residual current
I? I
Residual current circuit
with correct protection
by residual current device
a b c1 c2 c3
1 2 3 4
0.1 0.3
0.2 0.5
50 200
100 300
mA 100
Extra protection In the event of direct contact
Zone physiological effects
Fire Protection
To provide extra protection in the event of direct contact with an (unearthed)
live part, extremely sensitive RCCB's with a rated residual operating current
of 30 mA or less (I = 30 mA) are used instead of more conventional RCCB's ?n
with higher residual operating fault currents.
This extra protection is necessary if:
l The insulation of totally insulated devices or their loads are damaged.
l The earth wire is interrupted
l The earth wire and live wire are transposed (accidentally thus rendering line
the body of a protection class I device).
l A component which is live in normal operation is touched during repair
In view of this increased range of protection, an RCCB or RCCB/MCB with
I = 30 mA is must - by law in some European countries - to be used when ?n
installing machinery of equipment in areas with particularly high accident
l Socket-outlet power circuits in rooms with bath or shower.
l Caravans, boats and yachts and their power supply on camping or berthing
l Electrical appliances in rooms used for medical purposes.
The drawn-in switch-off characteristics of residual current devices with a rated
fault current of 10 and 30 mA make it clear that these residual current devices
are able to prevent the occurrence of the dangerous heart chamber fibrillation.
For this reason, residual current circuit breakers with rated fault currents of 10
mA are used for the protection of particularly exposed individual equipment.
Residual current circuit breakers with 30 mA rated fault current are already
specified today for many areas (bath, medically utilized rooms, outside areas,
agriculture, etc.) in order to ensure the protection of persons.
1 Usually no reaction effects.
2 Usually no harmful physiological effects.
3 Usually no organic damage to be expected. Likelihood of muscular
contraction and difficulty of breathing reversible disturbance of formation
and conduction of impulses in the heart and transient cardiac arrest without
ventricular fibrillation increase with current magnitude and time.
4 In addition to the effects of zone 3, increasing with magnitude and time
pathy physiological effects such as cardiac arrest, breathing arrest and
heavy burns may occur.
Even relatively insensitive RCCB's (I = 300 mA) can be used to provide ?n
effective protection against fire caused by earth-Ieakage faults. With a residual
current = 300 mA, the electrical energy released at the location of the earth
fault is not sufficient to ignite normal building materials. With larger residual
currents, the RCCB switches off the circuit in less than 200 milliseconds, thus
limiting the amount of energy released to a harmless level.
R Residual
R e s i d u a l
I current ?
Additional Protection Against Pulsating Fault Currents
Precautions for installations
Fault finding when RCCB trips
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 sensitive.
l Wiring should be done by a trained & qualified electrician as per the wiring diagram.
l All wiring necessary for operation shall be passed through the RCCB.
l The neutral conductor must be insulated against earth to the same extent as the live conductors.
l All equipments used must be properly earthed.
l To ensure correct functioning care must be taken that the neutral conductor on the load side of the RCCB must not be
connected to earth, otherwise nuisance tripping may occur or tripping may be impaired.
l Suitable device either MCB or HRC fuses shall be used for short circuit and overload protection of the circuit under
l Don't expose the circuit breaker to direct sunlight, rough weather and keep it away from the influence of magnetic field.
Switch OFF all the switches/MCB's connected in the circuit downstream the RCCB. Switch ON RCCB and switch ON the
switches one by one. You will find that during switching ON of a particular appliance/switch RCCB trips again and again
which shows that this is the faulty circuit/appliance. Isolate the faulty circuit, rectify the fault and switch ON the RCCB.
Permissible Earth Resistance (R ) With Max. Permissible Touch Voltage (U ) E T
Therefore the following earth resistance must be guaranteed with 300mA rated fault current of the selective switches :
U = 25V R = 83 Ohm U = 50V R = 166 Ohm U = 65V R = 216 Ohm T E T E T E
Voltage (U ) (V) T
Earth Resistance R ( ) E
I (mA) ?n
30 100 300
Sensitivity Selection Criteria
Sensitivity Application
30mA Tripping current designed for additional protection against direct contact, or where specially required b y
the Indian wiring regulations, the 30 mA RCCB protects against leakage currents and indirect
contact with earth loop impedance up to 1667 Ohms; for use as additional protection against direct
contact, residual tripping current must not exceed 30 mA.
100mA Tripping current is suitable for protection against indirect contact and leakage currents for larger
installations; the 100 mA RCCB's operate within 30 ms, but do not provide the same level of
personal protection as the 30 mA units; the 100 mA RCCB protects against leakage currents and
indirect contact with earth loop impedance up to 500 ohms.
300mA A less sensitive protection suitable for large installations having high levels of leakage current;
300 mA RCCB's protect against leakage current and indirect contact up to 167 ohms earth loop

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