Would you say what is RCD, so a layman could understand

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jraju

Joined Jul 23, 2017
67
Hi, Recentlly i came upon a news item that to provide protection to human lives in homes, RDC, is to be provided to all households
Residual Current Device is the name of the device.
But I want to know, in layman terms what it is and how you will get protection.
A descriptive reply would be helpful to many.
How it is used to protect from electric shock
 

Yaakov

Joined Jan 27, 2019
3,769
Hi, Recentlly i came upon a news item that to provide protection to human lives in homes, RDC, is to be provided to all households
Residual Current Device is the name of the device.
But I want to know, in layman terms what it is and how you will get protection.
A descriptive reply would be helpful to many.
How it is used to protect from electric shock
An RCD (Residual Current Device) is a special circuit breaker that trips when it detects a difference in the current flow on the live and neutral lines. In normal operation, the two should be equal. If they aren't, it means some current is flowing elsewhere (for example to the ground) and that might be a person conducting the missing current, so it quickly breaks the circuit.

In the US, it is called a GFCI (Ground Fault Circuit Interrupter).

There is a lot of information, with pictures, and even videos easily found on the web.
 

Dodgydave

Joined Jun 22, 2012
10,095
An RCD is used in the UK and European countries to detect Earth leakage currents , it measures the current in the Live and Neutral wires at the same time, if there's an imbalance upto 30mA the breaker will trip and disconnect the power.
 

Thread Starter

jraju

Joined Jul 23, 2017
67
Thanks. But where will it be fixed.I have the earthing and also drip switches.
is rcd is must for single and 3 phase?
were there not safety with existing provision of earthing and drip switches ?
Why it was not in practice while thechnician provide wire and switches?
is it a latest invention,the rcd?
is it a fact that phase current should be equal to neutral always and the difference should be zero?
 

Yaakov

Joined Jan 27, 2019
3,769
Thanks. But where will it be fixed.I have the earthing and also drip switches.
is rcd is must for single and 3 phase?
were there not safety with existing provision of earthing and drip switches ?
Why it was not in practice while thechnician provide wire and switches?
is it a latest invention,the rcd?
is it a fact that phase current should be equal to neutral always and the difference should be zero?
RCD/GFCI is not new, it's been around a long time. The RCD protects a person who has made a circuit between live and ground, so the ground itself is actually part of the problem being solved. It is for single phase circuits. I have no idea where you are, but in the US, UK, and Europe it has been in the code for a long time and is always fitted on circuits in wet locations.

Yes, the current should only flow between L and N, so if there is a difference between the two, current is flowing somewhere else and that is never good and sometimes deadly.
 

Thread Starter

jraju

Joined Jul 23, 2017
67
So, is a. Kindof earthing. Is it not?
if proper earthing is given, you need not need rcd. Is it correct?
 

Ramussons

Joined May 3, 2013
1,100
So, is a. Kindof earthing. Is it not?
if proper earthing is given, you need not need rcd. Is it correct?
No. Earthing is a protection from leakage currents.
In the first place, there should be NO leakage currents.
The purpose of the RCD is to detect the presence of a Leakage current and shut off the supply.
 

crutschow

Joined Mar 14, 2008
28,227
Normal current flows between hot and neutral.
If you touch the hot, the current will between hot and ground.
This is not normal, causing an imbalance between hot and neutral currents, which the RCD will detect and open the circuit to prevent electrocution.

Understand now?
 

Ian0

Joined Aug 7, 2020
3,785
Is that anything different from drip switch working
Yes - the amount of current required to trip it.
An MCB for an ordinary domestic circuit is generally rated at 16A. It will trip when there is a fault current that exceeds 16A.
An RCD for domestic use trips when there is a fault current to earth of 30mA.

There was a time when they were called RCCBs - Residual Current Circuit Breaker - why did we have to change it to RCD? Doesn't "circuit breaker" give you a better idea than "device" of what it actually does?
They used to be called ELCB (Earth Leakage Circuit Breaker) and they actually measured the current in the earth wiring. Not such a great idea as the fault current can find many other ways to get to earth than through the earth wiring!
GFI (Gound Fault Interruptor) is also a nice descriptive name.

(The worst one of the lot is "consumer unit" - it could mean anything.)
 

MaxHeadRoom

Joined Jul 18, 2013
23,951
A RCD at the main breaker is not seen so much in N.A. Some years ago Just after I left the UK, it became mandatory there to install a RCD main breaker where Properties supplied by a TT earthing arrangement (one with a local earth terminal, as opposed to an earth being provided by the distributor).
In N.A. they are more commonly used in individual outlets, as needed.
If one want a in depth explanation of earth grounding, I suggest the book Grounding by Eustace Soares, it is used by NEC,CEC code requirements and is published by the IAEI International Association of Electrical Inspectors.
 

Ian0

Joined Aug 7, 2020
3,785
A RCD at the main breaker is not seen so much in N.A. Some years ago Just after I left the UK, it became mandatory there to install a RCD main breaker where Properties supplied by a TT earthing arrangement (one with a local earth terminal, as opposed to an earth being provided by the distributor).
In N.A. they are more commonly used in individual outlets, as needed.
If one want a in depth explanation of earth grounding, I suggest the book Grounding by Eustace Soares, it is used by NEC,CEC code requirements and is published by the IAEI International Association of Electrical Inspectors.
RCD have spread - first it was just the TT systems, then it was all sockets that could be used for equipment outdoors, then it was all the sockets. Now, it's everything, with TWO RCDs - the second one for the lighting circuit. You've mentioned Eustace Soares before - I might give it a read as I can get a 2005 copy for <£10. It might even give a better insight on how to earth an off grid power system which switches between generator and inverter and is mounted in a separate building from the premises supplied!
 

MaxHeadRoom

Joined Jul 18, 2013
23,951
Have things changed in the UK as to bonding the neutral to the earth conductor in the panel as it is in NA.?
I know when I carried out electrical work back in time in the UK, it definitely was not, also you could not use or bond to any service supplied ground conductor, you had to find a means of ground yourself.
 

Ian0

Joined Aug 7, 2020
3,785
It's mainly TN-C-S (aka PME - Protective multiple earthing), with earth and neutral bonding where the supply enters the building, and earth bonded to any extraneous metalwork, plumbing, gas pipes (and aluminium window frames for the really pedantic electrician). Rural properties are sometimes TT, with an earthing rod. There seems to be more emphasis on "equipotential" than on "earth".
 

Yaakov

Joined Jan 27, 2019
3,769
It's mainly TN-C-S (aka PME - Protective multiple earthing), with earth and neutral bonding where the supply enters the building, and earth bonded to any extraneous metalwork, plumbing, gas pipes (and aluminium window frames for the really pedantic electrician). Rural properties are sometimes TT, with an earthing rod. There seems to be more emphasis on "equipotential" than on "earth".
I have heard a lot of talk by various UK electricians on YouTube about the focus on equipotential bonding. It does seem to be a thing of late.
 

Ian0

Joined Aug 7, 2020
3,785
I have heard a lot of talk by various UK electricians on YouTube about the focus on equipotential bonding. It does seem to be a thing of late.
It's like the bird on the electric wire - if everything it can touch is the same potential, it's safe, even though it's all 6.6kV!
 

Deleted member 115935

Joined Dec 31, 1969
0
An RCD (Residual Current Device) is a special circuit breaker that trips when it detects a difference in the current flow on the live and neutral lines. In normal operation, the two should be equal. If they aren't, it means some current is flowing elsewhere (for example to the ground) and that might be a person conducting the missing current, so it quickly breaks the circuit.

In the US, it is called a GFCI (Ground Fault Circuit Interrupter).

There is a lot of information, with pictures, and even videos easily found on the web.
Thank you, now I know what my US friends are talking about with a GFCI..
separated by a common language ..
 

MaxHeadRoom

Joined Jul 18, 2013
23,951
The practice of Equi-potential bonding is now also used in Industrial enclosures & machinery etc, in order to eliminate ground loops.
 
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