Why RCCB cannot give protection against Overload and Short Circuit Faults?
To better understand Why RCCB cannot give protection against Overload and Short Circuit Faults, you must know the simple working principle of RCCB. RCCB mainly used to sense the leakage current. RCCB stands for Residual Current Circuit Breaker. In this article, I have tried to explain the working of RCCB with diagrams, which will help you to understand why RCCB cannot work in overload and short circuit fault.
RCCB Internal Circuit Diagram
Here
the simple internal circuit diagram of RCCB is given below.
Here
you can see, three coils are wound on a core. The upper coil for the incoming
line, the lower coil for the return line and the middle coil is the sensing
coil which connected to the relay. So when the current in incoming and return
line is same, there will be no resultant flux produced because the flux
produced by incoming and return will oppose each other.
But
if the current in incoming and return wire is unequal, then flux also be
unequal hence a resultant flux will be produced for which an emf will be
produced in the sensing coil. As the sensing coil is connected to the relay,
the relay will trip the RCCB and disconnect the circuit.
So,
it is clear that the working of RCCB is based on Kirchoff's Current law that is
the incoming current must be equal to the outgoing current in a circuit. So the
simple concept is, when the current is unequal in both line it will trip and
disconnect the circuit.
Why RCCB cannot give protection against Overload Fault?
The
below diagram shows, there is an overload fault occurs in a circuit where RCCB
is connected.
Here,
the incoming current and return current are the equal even overload fault
occurs. A high current flowing through the RCCB due to overload fault but
the RCCB does not trip as the current in both line is equal. Now, if the
overload current exceeds the current rating of the RCCB, it will be damaged.
Why RCCB cannot give protection against Short Circuit Fault?
In
this case, the concept also same as previous. During short circuit fault, a
very high current flowing through the RCCB, but it does not trip as the current
in both line is equal.
When RCCB will Trip?
Here
you can see, the phase wire touches the earth wire for which, Current comes
from the phase wire and goes back through the earth wire, not through the
neutral wire. So, the current in incoming and return wire in RCCB become
unequal. According to the working principle, as the current in both lines is
unequal it will trip and disconnect the circuit.
- Proper RCCB connection Diagram with MCB.
- MCCB Full Form | MCB and MCCB Difference
- [Explained] Main Differences Between Relay and Contactor
- Why AC needs more Insulation than DC for same Voltage Level?
Thank
you for visiting the website. keep visiting for more updates.
Why RCCB cannot give protection against Overload and Short Circuit Faults?
Reviewed by manoranjan das
on
10:27 am
Rating:
