Earthing System

[alpasty]

I am doing up a cottage in Hungary. Most supplies in Hungary are in three phase, which has been brought into the house with a temporary site board attached. The underground cable coming to the house is a four wire aluminium supply cable, and does not have steel armouring or any other other means of earthing, this is a standard type of supply cable in Hungary.

The electrician we have been speaking to has said that we will need to intall an earthrod etc, as in a TT system, but then he has also said that there will have to be a link from the neutral to the MET as well.

This to me sounds strange, as it seems to be a mixture of a TN-C-S system and a TT system. From all the reading I have done, I have not seen any mention of a system like this, or come accross anything like this in the UK.

Can anyone please comment on this, firstly if they have heard of anything like this before, in any other countries, and secondly, if the earthing was to be carried out like this, are there any safety (or other) inplications in a set up like this.

Other than this earthing issue, all other wiring seems identical to the UK system, except that the in house wiring is either done in trunking with single wires, or they use a cable called MBCO which is a 3 or 5 core cable (looks more like a flex, but in grey) and is used
outside of trunking. As in other EU countries, they do not allow our 2 core and earth, as the earth has to be insulated, unfortunalely.

Any help would be greatly appreciated, many thanks.

 

[i=p/u]

maybe is tn-c-s with tt backup, intersting post and im only trainee

 

[MarkieSparkie]

Rest easy your electrician is not doing anything unusual.
In the UK local earthing of TN-C-S supplies is rarely required because the supply authority (DNO distribution network operator) is required by law to ensure that the PEN (protective earth neutral) conductor is adequately earthed (PME protective multiple earthing) at regular points along its run. Although local earthing was common in the past before it was a legal obligation and is seen occasionally in old installations. It is also sometimes required in modern installations in areas of addition risk within or outside buildings.
The difficulty for the electrician is this local earth has to be of very high quality (the actual value depends on the load and network parameters) if the touch voltage impressed on to exposed metalwork in the consumers installation is to be limited to a safe level.
I hope reassures you.