Discuss Electrical Supply in Rural Area. Trying to understand supply arrangements in the DIY Electrical Advice area at ElectriciansForums.net

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J

jacksongroup

Hi All,

I have recently moved to the wilds of Scotland and to a house in a rural area. Now I have worked on electrics for a number of years in the SE but have been pursuing a teaching career for the last few years. Intend to take on a little domestic electrics to supplement incomes. Now most of my work has been in cities and not given much thought to overhead powerlines. As the supply to the property I am currently in needs a little work this is where I am going to start.

Now the power supply comes in on top of poles before being taken to a transformer on the top of the pole before going underground to our property. Once at the property the supply is very definitely TNCS and not TT as I would at first have expected. At the henley block on the pole I can see the neutral is connected to an earth cable that then runs into the ground and is repeated at other poles with transformers consistent with PME

I am having an issue with identifying what is on top of the pole. There are 3 overhead cables . The two outer cables are tapped off and go into the transformer ( the middle continues on its way). I am thinking that one of these two cables must be the live and the other a neutral. However the farm next door reckons on having a three phase supply.

So my confusion is this... are the three cables all live(different phases) and if so, how do I have a neutral? Is my neutral path actually provided by the earth? OR if one of these cables is actually a neutral and the other two are lives can the neighbouring farm actually have a three phase supply and is it normal to have two lives and one neutral as I would have thought this could easily be somewhat unbalanced.


Any help in improving my understanding gratefully appreciated. Have spent a long time trying to find the answer and many hours looking at the poles to try and understand!
 
Can you not speak to the DNO and ascertain what type of supply they have supplied.
 
Thanks Pete. I know the supply arrangement is TN CS I can see the N and earth connected at the head . Also a big label by head confirms PME and thus is confirmed by observation at all the posts along our road where I can see an earth bonded to the neutral at top of post and ran into the ground below. My confusion is what is happening at top. Do I have 3 phases running past the house or 2 and a neutral.

Thanks again and hope that clarifies.
 
i'd say that you have 3 phases and all 3 should go into the transformer where the N will be created from the star point.
 
i'd say that you have 3 phases and all 3 should go into the transformer where the N will be created from the star point.

Three phase would be my bet, but you only need to use 2 phases for the tx
 
Thanks for all the feedback. So if I can summarise would you kindly confirm my understanding is correct or otherwise. The three lines at the top of the pole are all lives. No neutral! EVEN THOUGH only two of the phases are fed into the transformer they can (and this is where my knowledge is scant) at the "star point" form a neutral to which the neutral supply is taken for our property. I will do some more research now but now I know what iM looking for! I hope. Thanks all once again.
 
It sounds like you are talking about three 11kv oh lines with a single phase (or split phase) TX being connected. If the farm next door has three phase they must be off a different TX as you cannot get three phase LV from two HV phases well not without an inverter anyhow.

The 11KV OH lines are all phases with LV neutral being taken from the star point of the secondary windings. You will have 11KV phase to phase and 6.3KV phase to earth.
 
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Correct if it's a three phase supply the transformer would use 3 11kv phases with the primary of the tx in a delta configuration the secondary side of the tx would be in star configuration, with the star point being earthed creating a neutral.

Single phase the secondary would have one side of the winding earthed, creating a neutral.
 
Guys . You have all been brilliant. Of course it now seems obvious.... the farm is on its own transformer. Thanks again.
 
i can't see it either. always thought you needed 3 phases to create a star point.
 
Electrical Supply in Rural Area. Trying to understand supply arrangements {filename} | ElectriciansForums.net
 
I'm rushing, I think we may have got wires crossed with my explanation.

You cant produce a three phase output with only 2 phases. (Well you can, but I don't have time right now to explain it).

A single phase rural supply will only use 2 phases on the primary side of the tx.
 
Rob, Thanks for the drawing - it is as I imagined. One further question if I may be so bold! on the 11kv winding is one phase the inbound and the other ( of the two phases feeding the transformer) the outbound? Thanks again.
 
I put up some pictures of our transformer here ... #168 and here #172

Ours is TNC, but the SSE guy had to dismantle the head to confirm.

Tony S
 

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