RCCB working principle with diagram

Hi friends today I will explain RCCB ( Residual Current Circuit Breaker) How RCCB work and How it’s trip work.RCCB working principle with diagram, If you like my article please share this in your group and follow my site www.automationwale.in

rccb working principle pdf

Earth leakage circuit breaker function of RCCB is, when, current are not equal, it will sense and trip, the difference in current, is called residual current.

Now, how residual current flows? here it is opening both the connections line & neutral both, here I have shown one simple system, the secondary of the transformer, which is located in the sub-station, from there, 2 wires will come to our house, one is called line wire, one is called neutral wire, Another point is earth, the wire length may be of few Kms,

rccb circuit diagram

Now suppose we have connected 10 Amp load, so, current can flow line to neutral and neutral to line, it will be changing time wise,

when current is flowing line to neutral, current is 10A instantaneous, if you add these two currents, total current or net current, or residual current will be zero,

Now suppose, current is flowing FROM Neutral to line, then again summation of these currents, will be zero or residual current will be zero,

single phase rccb connection diagram

Now suppose between line and earth, we connect a load with earth, this current may be, because of insulation failure, or because of human body,

Now Main line wire, will have main current plus earth current both, Earth current is flowing through earth, this current is not flowing in the neutral, so the current, will be more than main current, so if we add these two currents, there will be net 0.1 Amp current, that is called the residual current, because of which, circuit breaker will trip.

Now suppose instead of resistance, there is a human body, now this person will get shock,

Current will flow From body to earth, again the current will flow through line, not through the neutral, so the current will be more and we will have a difference in current or some residual current will flow, because of which, circuit breaker will trip, and it will protect us.

3 phase rccb working principle

Now suppose, there is a fault between, neutral and ground, due to neutral insulation failure, or some other thing,

Then what happens, the long neutral wire, will have some resistance, so the current, will find 2 path, so the current will be shared by neutral and earth, so again these currents will not be equal, there will be residual current and circuit breaker will trip.

Now we will learn the concept of RCCB,

This is Circuit of RCCB, this has 4 connections, L1, Neutral, L2, neutral, this is incomer And outgoing, here L1 & N to be connected to line, L2 & N are to be connected to load,

Now what happens, when the leakage is not there, the current will be equal, the CT is inside of RCCB, so when there is no residual current and there is no earth leakage, then the current will be equal, so net primary current will be zero, no flux will flow and secondary current will be zero,

Now suppose, we connect the resistance with earth or some human body is touching line, then the current not be equal, so there will be net current in the primary, Some current will flow in secondary also, because of that, coil will operate and RCCB will trip, it will open the switch.

Here again I have shown a simple circuit,

IL is line wire, IN neutral wire, R is load, because of this load, current will flow both direction, the is CT located inside the breaker, now this current, IL line current I have shown here, in graph red color, Neutral current is shown in black color, the line current and Neutral current are equal, but in opposite directions, when we add these 2 currents, net current will be zero, Net primary current of the CT will be zero.

Now suppose, there is a fault, or there is a leakage,

Now the current, will flow in the line and line current will become, like Residual I , it will increase little, now when we add this line current and neutral current, total will give some value, it will not be zero, it will be residual current, this current will behave like net current flowing in the primary of the CT, these 2 wires(IL,IN) together act like, primary turns of the CT, because of the primary current or residual current, secondary current will flow in secondary of the CT.

The current will flow in a coil, because of the current, there will be a flux in the coil, here we have one iron piece, because of this flux, this will attract mechanically and the switch is connected mechanically, so the contact will open, but this will happen, when there is a residual current, when this is not there, both currents are equal, no primary current, no secondary current, no breaker trip operation, breaker will operate only, when net residual current flows.

Types of RCCB,

Now, Types of RCCB,

Mainly there are 3 types,

1) 1) AC

2) 2) A

3) 3)B

AC types of RCCB, is sensitive for AC currents,

A type is sensitive for AC current + pulse current, this is pulse type current, it will be there, when there is a rectifier or inverter or some thyristor is connected, A type RCCB for AC and pulse both.

B type RCCB, is sensitive for AC , as well as pure DC, In our home, generally AC types are used, But in lab or where inverter is there or converters or thyristors are there, it is possible that, output of the rectifier is getting short circuited with earth, that time we have to use B type RCCB.

rccb 30ma or 100ma

Now poles, RCCB may be available, with many types of poles, for single phase line and neutral, there will be 2 poles.

For 3 phases, there will be 4 wires, a, b, c and neutral, so we require 4 contacts, that is called the 4 pole, similarly trip current rating may be, 30mA, 100mA, 300 mA or some other value, this means, whenever residual current, becomes more than 30mA, Then RCCB will trip.

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