Us and them

[La Poste]

I'm only a novice but it seems to me that countries like France like to use more double pole RCBO's and MCB's than us.
Is it true that in a lot of the places in Europe they have no earth circuit and so their primary form of protection are RCD's as they have no low resistance earth fault path and hence cannot rely on MCB's working if their is a phase to earth fault, is that why they are more focused on RCBO's than us?
Is this a fair assumption or am I barking up the wrong tree?
Cheers.

 

[La Poste]

I thought it was a good question.
Doesn't anyone have an opinion?

 

[m4tty]

Good question mate. I'll be watching this thread for the answer too.

 

[Sparky Ninja]

I can't give an exact response to the question, however I believe it is likely when you consider the absence of earth potential at many places.

For example, I saw a whole hotel installed earth free as it was up in the mountains. You could assume that the supply from the distributor would come with an earth, but if it's a long way it may be a better design to consider an earth free location. As long as disconnections times can be obtained.

 

[La Poste]

it may be a better design to consider an earth free location. As long as disconnections times can be obtained.

Earth free location, what would that entail?
No metal switches or equipment of any kind.
Or maybe reliance on an earth rod.
How do they deal with a phase to earth fault?

 

[Des 56]

PME is the cost word that sums it up
Before that,this is one reason why earth protection is a good thing

The double fault dilemma

If the supply transformer was not spiked to earth,there would be no circuit to cause danger, when an appliance insulation broke down or it faulted to the metal frame

Why earth neutral of the transformer then, if the earth fault is now not a danger ?

The next earth fault or insulation breakdown will, (with the first fault still in circuit) cause a return path and danger
I see it as a boiler going live to earth,no fuse blows because there is no circuit
The washing machine fed by plastic water pipes developes another earth fault,this time neutral earth,nothing blows no circuit
Person touches washing machine and water tap,now bridging live and neutral,rcd is no use, as no imbalance caused by person bridging the supply,person dies

Earth fault protection reduces the danger,Rcds are ok as an additional protection to the primary earth protection
Double pole is required for TT systems
Tnc-s is also better with double pole,but cost is the all important factor
I know nothing of foreign systems but,I dont get re assurance with the sites I have seen of those installations.
We could do better if cost wasn't an issue,but theres not much better we could do as far as I can see
The pme supply network would provide safer installations, if they run the earth seperate
But copper costs money

 

[bomjac]

I can't comment on the French setup, but what I can say is that the Norwegians have one of two systems in their domestic sotuautions.

They either have 2 phase 220V or single phase and neutral 220V in their homes. Obviously the 2 phase 230V requires a double pole swith for safety reasons. Im pretty sure the apartment we stayed in had 2 of the "bottle" type HR fuses per circuit as protection. The rest of the intricacies escape me, as it was some years ago, although I am pretty sure that the 2ph system incorporated an earthed neutral at the transformer or distribution point.

Incidentally, the Norwegians have an interesting approach to electrical safety. Over there if you are an electrician and happen to receive an electric shock that you report as you are legally obliged to do so, then you are liable to have 2 things happen to you.

1. An overnight stay in the hospital for observation, as the shock can set up murmurs in the heart.
2. To be tried and fined at the local sherrif (or whatever they are called) for failing to folow safety procedures.