Will an RCD offer any protection in a building with NO earth circuit?

[Rockingit]

International distribution systens are fascinating, and completely dispel the myth that Brit is best, too. For example I'm currently in Australia, in basically a Brisbane city suburb. Walking down the road and I realised when glancing at the poles that the same pole is carrying both HV and LV - Conventional delta HV on top and then intermittently it drops down via a TX onto the LV lines and appears as 3PN. Earthing (that I've seen, anyway) is TT. A simple idea that must save on costs massively whilst delivering constancy over long distances.

 

[Mike Johnson]

The power providers in France leave the earthing arrangements to the home owner so TT systems are the norm, most electricians carry large SDS drills for that purpose.

 

[ElectroChem]

International distribution systens are fascinating, and completely dispel the myth that Brit is best, too. For example I'm currently in Australia, in basically a Brisbane city suburb. Walking down the road and I realised when glancing at the poles that the same pole is carrying both HV and LV - Conventional delta HV on top and then intermittently it drops down via a TX onto the LV lines and appears as 3PN. Earthing (that I've seen, anyway) is TT. A simple idea that must save on costs massively whilst delivering constancy over long distances.

Australia's LV distribution is almost exclusively PME/TNCS, here called MEN (Multiple Earthed Neutral). You'll find very few TT systems here.

 

[pc1966]

Australia's LV distribution is almost exclusively PME/TNCS, here called MEN (Multiple Earthed Neutral). You'll find very few TT systems here.

But you do have single-wire eath return HV systems where the Earth is your return path?

That is about TT as you can get LOL!

 

[GeeGee50]

If the appliance is not connected to earth then the RCD will not have any earth leakage current to detect, until your body provides a path when you touch it. So the RCD with no earth won’t trip.

But isn't there still a leakage / loss of current if the appliance develops a ground fault (i.e. the active/live wire touches the appliance chassis/casing)? Therefore, this will create an imbalance of current between Live and Neutral and therefore the RCD will still trip?

 

[brianmoooore]

But isn't there still a leakage / loss of current if the appliance develops a ground fault (i.e. the active/live wire touches the appliance chassis/casing)? Therefore, this will create an imbalance of current between Live and Neutral and therefore the RCD will still trip?

Only if the unearthed appliance is in contact with the general mass of earth, which is by no means certain, since many appliances sit on rubber or plastic feet.

 

[westward10]

But isn't there still a leakage / loss of current if the appliance develops a ground fault (i.e. the active/live wire touches the appliance chassis/casing)? Therefore, this will create an imbalance of current between Live and Neutral and therefore the RCD will still trip?

Not if it is not connected/isolated from earth. Live will touch the casing, have no where to go and not create an imbalance.

 

[Thrubstack]

Surely when you touch a live circuit, your body provides a path to earth, that will result in an imbalance and the RCD trips.

 

[brianmoooore]

Yes, there's a good chance that your body will provide a path to earth and imbalance the currents, with the result that the RCD trips.
This will probably save your life, but it will still hurt.

 

[HappyHippyDad]

Yes, there's a good chance that your body will provide a path to earth and imbalance the currents, with the result that the RCD trips.
This will probably save your life, but it will still hurt.

Can you really say a 'good' chance? If you see post number 9 your body will only provide a pathway to earth if the neutral point of the transformer is earthed. I have absolutely no idea if this would be common practise in the OP's country.

I suppose it couldn't actually do any harm by using a plug in RCD. It would either not work, so you're no worse off, or it would work and probably safe your life. So I guess it's a good idea. However, by using an RCD you may feel a sense of security and take greater risks!