High Ze

[Sidewinder]

OK Plumber I know about PNB, it's just not that common as is it not normally a tn-c-s single consumer fed from a single hv source?

e.g. a dedicated hv/lv transformer normally, where as this would normally say be an out laying premises, e.g. perhaps a farm supply.

It would be almost unheard of to have this in a location serving multiple premises would it not?

I don't have my my ESQCR stuff around at the moment, though I thought the application of PNB was restricted?

 

[Chr!s]

OK Plumber I know about PNB, it's just not that common as is it not normally a tn-c-s single consumer fed from a single hv source?e.g. a dedicated hv/lv transformer normally, where as this would normally say be an out laying premises, e.g. perhaps a farm supply.

It would be almost unheard of to have this in a location serving multiple premises would it not?

I don't have my my ESQCR stuff around at the moment, though I thought the application of PNB was restricted?

Agreed

Some dnos dont use pnb at all, depends upon your area as to whether you will comes across it.

Saying that its been included in the dpc, restrictions on pnb will come down to risk, and this is what limits it use.

 

[Megaohm7]

Megaohm7,As far as you are concerned in the UK mate nothing TN-C-S = PME ESQCR says so and that is statute law.

Cheers mate. That's a relief phew!! lol I'm sure I answered a question regarding ESQCR in my 2391 exam by the way ..

---------- Post Auto-Merged at 19:41 ---------- Previous post was made at 19:35 ----------

As i understand it, and this was partly explained to me, actually by Steptoe and others here, as well as a DNO friend of mine, that a PME system should be neutral roded at every joint on that cables run from the supply TX. On overhead distribution systems roded at regular intervals. (sorry, i'm not sure of the actual spacing distances) Also remember that almost all overhead supplies, are in fact initially supplied via an underground cable...Now as far as i can make out, DNOs TNC-S hasn't been roded as per PME requirements, most of these supplies are work in progress, converting older TN-S systems to PME. So joints have been roded, but not all, as to meet PME requirements. For the DNO to guarantee a 0.35ohm Ze all or most of those joints need to be roded. Which is maybe why the DNO in this case quoted the OP, that upto 0.80 ohms is OK. I'm not saying this is an ideal situation, and that maybe other factors are also present in this particular situation.... As far as you would be concerned, if the head neutral also contains an earth tail, it's a PME system. This was basically the point i was trying to get accross above...

It's OK to say that all TNC-S is PME in the UK, but that statement doesn't always give the DNO room to complete conversion of previously other designated systems. It doesn't magically just happen, it takes time and a good deal of money to convert to PME, so conversions are completed over varying time periods and is continuously ongoing throughout the whole country, ...but it gets there in the end ...lol!!!

Cheers for that mate. I thought I was going nuts then but at least I was barking up the right tree lol. would always enquire with the DNO if the readings for Ze was high for the type of earthing arrangement concerned. Mega..