I presume the house is TT,and the brick 'garage' with the vented door hides a substation or street switchgear and some LV fuses - it does not look like a sewage pump or a gas regulator though round here the transformers are open and the pumps are enclosed..
Is there an 11kV pole behind it ?
If it is a substation, there may be combined HV and LV earth or they may be separate. There is perhaps a chance of putting a rod in the garden of the house near the boundary and getting an impedance near that of TN-S .
I'd be asking How far does the house extend the other way - any electrode to be placed nearer the other neighbour may be prudent.
Yes it's the substation and the house is TT, but I cannot find a rod.
Assuming the cables 11k cables run straight out into the street, in front of the house are buried gas and water supply pipes plus a lead sheathed electric supply cable, so I think I had better go around the back of the house!
PSC is only 0.913 kA (0.25 ohms), which surprised me as I assumed it was TT due to its close proximity to the substation.
At 1/4 ohm sounds like TN-S - I presume you looked and found no clip or soldered tail on the lead cable though, so it is acting as underground TT.
Mind you, acting as an electrode the gas and water pipes or the metal jacket of the cable coming in will all leave you pretty well coupled to the substation earthing, what ever you try to do with a short bit of metal in the garden in parallel. That may be what you are measuring really, if there is no formal electrode.
If the house has an underground metal sheathed supply cable would the DNO not be willing to clamp the earth tail to it? That seems like the best option the earth loop will be very low impedance I can't think 8f a better earth in those conditions. I do wonder why that hasn't been done anyway for all the houses unless its been converted from OH lines at some time
There’s apparently two main earth conductors with unknown destinations, a 6 mm and a 10 mm with a RA of around 30 ohms on each, but Zdb is 1.43 omms with everything connected due the steel gas pipe, which is probably under the hedge.
It’s not dangerous, but there is not a identifiable means of earthing probably due to the rods being under block paving.
It needs a new rod to satisfy the requirements of having an identifiable means of earthing. The easiest place to put it would be between the house and the substation, avoiding underground services and the rain water drain, but that’s a bit close to the substation.
If the house has an underground metal sheathed supply cable would the DNO not be willing to clamp the earth tail to it? That seems like the best option the earth loop will be very low impedance I can't think 8f a better earth in those conditions. I do wonder why that hasn't been done anyway for all the houses unless its been converted from OH lines at some time
They might, but it is DNO dependant, and the history of cables varies. Not all lead cables, especially early ones, are actually connected at the transformer end and at every buried joint in the way that would carry the full prospective fault without failures.. In such cases, the armour may be at earth potential more or less, but still not safe to be used as the earth electrode.
You do see odd water pipe earthing clamps on lead mains, and sometimes the DNO do put them there themselves, sometimes they appear by magic, though more common now is a spiral 'constant force' spring, thingy, like the mutant offspring of the clockwork spring and the dangerous bit from a corned beef can - think cut fingers and a lot of spring force.
however, sometimes the DNO will say it cannot carry fault currents and declare it to be underground TT, When combined with cast iron incomers, and the lead mains can be that era, then you have a metal cased company fuse with no reliable earth. At that point a few phone calls are needed to get a new cut out.
