three pahse earth

[Dave]

If you are fed by three phase, how do you create an earth?

Dave

[The Natural Philosopher]

I think you will find d that God did that already for you.;-)

[Dave]

Groan :-)

Dave

[Fredxx]

Stake in the ground may well do!!

[Tim Watts]

On Wed, 14 Apr 2010 21:21:11 +0100, Dave wibbled:

Generally, you are either supplied with one or you stick a rod (or equiv) in the ground.

Or are you after a deeper understanding of neutral points in a 3 phase system? eg If you *only* have 3 phase (no neutral), then you could put a star wound transformer across the 3 phases which will create a neutral point.

While you're at it, get a Scott or LeBlanc transformer and create yourself a 2 phase (90 degree) system. Used to be popular in London - that'll confuse the next bloke to PIR it!

[The Wanderer]

You don't, the distribution company connects the star point of their transformer to earth. Even if you're fed at 11kv.

But I suspect that isn't what you wanted to know. Try being a bit more precise with your question, then we can give an intelligent answer.

[Dave]

Many thanks for your answer, that explains it perfectly.

Dave

[Dave]

Thanks, it was just a thought that drifted through my mind a few days ago.

Dave

[Dave]

I thought about that, but I know that electrickery is generated in 3 phases and wondered just how an neutral was made. It is quite clear now.

Many thanks to all who answered my pondering.

Dave

[Tim Watts]

On Thu, 15 Apr 2010 18:59:04 +0100, Dave wibbled:

In which case, these might be quite interesting for you :)

- and that bit I was babbling about 2 phase systems:

fun!

cheers

[Andrew Mawson]

OK this is how it works in my installation: 11Kv overhead cable comes onto the farm to a large pole mounted transformer on my land. Transformer gives out 415v three phase, with the star point connected to a large mat of copper wires buried under our goose paddock. Three co-axial cables (aluminium core (phase) insulated from copper outer sheath (neutral & earth) with overall insulation) all bundled together go overhead to my barn where the three copper sheaths are grouped and form my neutral and also my earth. The three aluminium cores go to the company fuse and onwards to my distribution system.. The three phases and neutral continues up the road where at the next pole one phase and earth/ neutral (still used as earth as only one pole away from transformer) feeds my house. Subsequent poles trot up the road feeding the neighbours about half a mile away. Their earth is locally generated at the pole (another earth mat) due to the distance from the transformer.

AWEM

[Rick Hughes]

Leccy board may well supply the earth depends on feed type .... or you may need to supply your own via earth rod.

If this is initially a temporary supply then you will have to supply earth rod.

[Dave]

Those links were very informative. many thanks for them :-)

Dave

[Andrew Gabriel]

That's a Protective Multiple Earthing (PME) system, also called TN-C-S if the consumer's installation uses the earth terminal supplied by the supplier (which is optional).

The combined Protective Earth and Neutral (PEN) conductor connects all the earth mats together - it's not that your neighbours have their own, you all share them all. The old Electricity Supply Regs (now superceded) required the PEN conductor to be grounded no more than 60 metres from the consumers' premises, and again periodically along the supply if consumers are spaced apart significantly. (I haven't had cause to check the current supply regs.) There was talk of changing the rules so that each TN-C-S consumer would also require their own earth rod.

[Dave]

That about sums up the answer to my question, which was triggered by how do houses in the sticks get their power and earth.

Many thanks

Dave