Suburban filling station

Lyledunn.

Answers are simple and electrical designer, installer and inspector must ensure electrical installation for the filling station fully complies with teh 4th Edition APEA/EI "Blue Book".

So either ( preferrable) TT earthing sytem or a guaranteed TN-S earth from the DNO but ONLY if DNO says in writing that TN-S will never be changed to TNC-S.

Now regarding location of the TT earth rods, the rods and their resistance area cant be within any haz area of the site and resistance paths should no go outwith the legal curtlidge of the filling station, so if they are right on site perimeter that could be an issue.

Regarding location of the DNO Secondary Sub, the ENA issued a technical bulletin that any secondary or primary sub on or near a filling station a GDEGS earthing survey must be carried out to establish the 250V thershold of the EPR in the event of an HV fault so that the belowground filling stations earthed metalwork will not rise above 250V. So responsibility of that sits with the DNO.

Anyway there will be a few other issues, but what electrical installation cert for the local petroleum enforcement authority was issued as with a new site cant be any defects or ommissions form the Minimum requirements of the "Blue Book"

GTB

I cannot see any EV charging equipment in your photo.

I cannot see any petrol pumps either, but I imagine that they will go on the plinths between the bays.

lyledunn said:

DNO would obviously not provide a PME terminal but given the proximity of other buildings, is it prudent to consider the site as TT?

I think the answer to this is yes, TT ... but there are some bits of thinking in design of TT systems in urban settings, which are perhaps often overlooked in TT systems in general.

For example ... we are used to thinking about external earth fault loop impedance being based on the earth electrode path alone, yet with shared extraneous-conductive-parts, or extensive ground-connected metalwork, when the extraneous-conductive-parts are connected, the prospective earth fault current may be substantially higher, perhaps (if there are shared extraneous-conductive-parts with other installations on the same transformer) approaching the L-N prospective fault current.

There may, similarly, be diverted currents if there are extraneous-conductive-parts shared with other installations. This is obviously not desirable for filling station installations, regardless of whether it's TT or TN-S.

Also bear in mind this is not a UK location rather ROI.

With all this Boris stuff have I missed Northern Ireland’s departure from the U.K.?

Excuse my writing with my little finger.

Is that the layout? Is the metal fence bonded to the Tx earth as well?

Some time ago I asked a question on this forum about installing a TT earth rod for a house adjacent to the DNO sub station supplying it, but I cannot find the discussion as I cannot master the search facility on this forum.

I thought I was pretty good at using search engines, but I cannot get the search on this forum to work.

It's not just the location of the electrode itself that might be an issue for the DNO, but any buried metalwork connected to the TT system, to which potential may be transferred through the ground resulting from earth potential rise due to a fault on the HV system.

If you want to make a hard and fast rule for this, then you'd be looking at 10 m or more separation, but in reality, if there's a global earthing system, or the DNO is happy that the ground potential rise and disconnection times are suitably low, then a lower (possibly much lower) separation distance may be acceptable.