by ericmark »
Thu Jul 29, 2010 6:35 pm
When we as electricians are taught we are told we can find out items like earth loop impedance at the head by inquiry to the Electricity Distribution Network Operators (DNO) in the main we can see as electricians what the supply is but sometimes it's not plain and since all supplies from the same step down transformer should be of same type the only people who can answer the question as to supply type is the DNO.
From:-
Statutory Instrument 2002 No. 2665
The Electricity Safety, Quality and Continuity Regulations 2002
It states:-
Information to be provided on request
28. A distributor shall provide, in respect of any existing or proposed consumer's installation which is connected or is to be connected to his network, to any person who can show a reasonable cause for requiring the information, a written statement of -
(a) the maximum prospective short circuit current at the supply terminals;
(b) for low voltage connections, the maximum earth loop impedance of the earth fault path outside the installation;
(c) the type and rating of the distributor's protective device or devices nearest to the supply terminals;
(d) the type of earthing system applicable to the connection; and
(e) the information specified in regulation 27(1),
which apply, or will apply, to that installation.
Under (d) above it is clearly the responsibility of the DNO to tell you what earthing system you should have.
However you can't use this power to get a free TN-C-S connection once they have visited and up-dated their records, and it is common for us electricians to demand to be told what the earthing arrangement is in order to force a visit and persuade their man to give us a TN-C-S earth. It may pay you to get an electrician to look at your supply first. If you have a TT supply that means earth rods are required.