TT system

[2tag]

Hi minds my first statement is that I am not a electrician my back ground
is very much in coms, the reason for this post is I recently visited a friend,
who lives in a remote part of Southern Ireland not far from knock, on the west coast.
The cottage itself was supplied by a TT system hence the large earth rod stuck
in the ground outside the cottage and the board RCD protected. From what I
have heard that in the event of an electrical fault, that the earth fault loop path
travels down the earth rod back to the supply transformer hence tripping
Main RCD on board, I know that RCD are extremely sensitive piece of equipment
and it won’t take much to trip. My question is the earth fault loop path taken into consideration the cross sectional area of earth itself the terrain around the cottage is for the best part very boggy and heavily burden with clay surely under
fault conditions the fault is just dissipated within the earth itself and not via
the supply transformer after all what consuetude’s for earth. So I find it hard to believe that this fault path actually occurs. On my return to my job I asked the in house electrician the very same question, which for some reason he offered me no viable explanations, and in fact got pretty peed off with me asking. Please can any one explain this dilemma that I have? Thank you for taking time and reading this post.

 

[Guest123]

RCD's operate differently to MCB's and fuses.

The coil in a RCD monitors the current flowing in the Line and Neutral conductors and as long as it's the same to within a milliamp or 2 it's happy.

Now when a fault occurs between Line or Neutral to earth, the current flowing in the Line and Neutral conductors has a larger difference as some is flowing to earth, the RCD see's this imbalance and depending on it's rating or setting will operate and cut off the supply.

It matters not where to earth it goes only that it is going to earth. This is why on TT systems all circuits must have additional protection via an RCD as the earth fault loop impedance (path via general mass of earth back to transformer in this case) is too high for an MCB or fuse to operate and clear the fault.