Earth rod query

[Knobhead]

For interest here’s the arrangement for a DNO substation.

View attachment 13578

 

[Silly Sausage]

Why is there an 8m min distance on your diagram?




You don't have to answer that question of course
Way out of my instrument league.

 

[La Poste]

The reason for the 8 metres is so the LV Earth does not pick up voltage from an HV Earth fault and transfer it to the LV system.

There is a rule that if an HV Earth is 1 Ohm or lower the LV and HV Earths can be combined but don't ask me why.

An HV Earth is also known as an Earth nest (multiple Rods perhaps) but again don't ask me why but I like the expression an "Earth nest".

 

[trev]

I was thinking about our local TX.

I wonder what the resistance of the earth electrode is on this:

You need to get out a bit more, there are these things called beer, women and things to do.
Sorry mate I couldn't resist

 

[jaresquire]

I often take the kids to the local park and whilst they run around creating mayhem I'm stood there looking at the sub-station in the corner..

 

[IQ Electrical]

I often take the kids to the local park and whilst they run around creating mayhem I'm stood there looking at the sub-station in the corner..

Talk about suspense! What's it like????

 

[malcolmsanford]

I often take the kids to the local park and whilst they run around creating mayhem I'm stood there looking at the sub-station in the corner..

I'm starting to really worry about you.........................

 

[jaresquire]

Big and green with swings and a slide!

 

[malcolmsanford]

The sub station?????

 

[trev]

Big and green with swings and a slide!

Only if Carlsberg built substations

 

[jaresquire]

If the DNO thought it would pay then it might happen

 

[Knobhead]

Why is there an 8m min distance on your diagram?

As La Poste has said to prevent imported MV faults appearing on the consumers system.
The drawing does show a removeable MV / LV link. All the transformers I’ve installed have had the MV to LV solidly linked.

This makes interesting reading http://www.cablejoints.co.uk/upload/Earthing___Guidance_Notes__Central_Networks.pdf

 

[Engineer54]

As La Poste has said to prevent imported MV faults appearing on the consumers system.
The drawing does show a removeable MV / LV link. All the transformers I’ve installed have had the MV to LV solidly linked.

That's because they were all probably well under the 1 ohm mark.... lol!!!

 

[Silly Sausage]

As ......................

I might have a read later. Thanks anyway.
It just seemed a specific value rather than, say, a 'round' 5 or 10m.