power from kiosk to house

[gof1]

Hi
I have a customer who has a kiosk with 100 amp cut out fuse supplied from UK power, he needs to bring the power 178 meters to his house,
He has asked the question if he puts in more kiosks with 100amp switch fuse in then out can he use 25mm SWA as long as there is no volt drop between 1st kiosk to 2nd kiosk then to 3rd kiosk, is this allowed as the size of cable would be massive for 178 meters, and yes he has already asked UK power who sai they will only supply to edge of his land? any thoughts comments will be appreciated?

 

[Yozza19]

Hi
I have a customer who has a kiosk with 100 amp cut out fuse supplied from UK power, he needs to bring the power 178 meters to his house,
He has asked the question if he puts in more kiosks with 100amp switch fuse in then out can he use 25mm SWA as long as there is no volt drop between 1st kiosk to 2nd kiosk then to 3rd kiosk, is this allowed as the size of cable would be massive for 178 meters, and yes he has already asked UK power who sai they will only supply to edge of his land? any thoughts comments will be appreciated?

No unfortunately it does not work like that large run of expensive cable

 

[westward10]

Volt drop would be considered from the point of source so the amount of kiosks is not relevant.

 

[gof1]

Volt drop would be considered from the point of source so the amount of kiosks is not relevant.

Can you explain to me when I have done farm work in past when we have taken 50mm SWA to a grain store, then we come off that grain store supply, to then add more SWA going to a workshop 40 meters away my governor said we only work out the volt drop from our new source (the grain store) not the origin of power onto the farm?

 

[westward10]

Volt drop is measured from the origin of the supply your governor is incorrect.

 

[davesparks]

my governor said we only work out the volt drop from our new source (the grain store) not the origin of power onto the farm?

Your governor is wrong, if you do that you'll end up with equipment not working at the far end due to the drastic voltage drop.
If you've allowed 5% voltage drop on the first cable, then 5% on the second cable and the supply voltage is in the lower part of the permitted tolerance you could end up with less than 200V at the load end of the arrangement!

If you need to feed a house 178m away from the supply then you need to calculate the cable size for the complete run, breaking it up into stages will do nothing more than create multiple points of potential failure.
Also bear in mind that the volt drop limits are to the end of the final circuits, not just the distribution circuit feeding the house.

 

[pc1966]

The DNO can allow higher drop as they are also in a position of knowledge/control over the supply to make sure the point of delivery is still within the ESQCR limits.

Sadly for an installation to BS7671 you are expected to deliver 5% overall drop, and so cable size is often a bit larger.

What you can allow for is the actual demands, so if you know a given installation is unlikely to pull more than 60A you can design for that even if the fuse is 100A. But you still have to achieve ADS on your supply protection (fuse, MCCB/RCD, etc) and that can also impose limits on what you design for if the cable meets supply protection CCC but is very long so VD is only mot on a partial load.

TL;DR you are looking at some expense, with ~95mm coming out of a simple calculation for the full 100A, or you are looking at designing for and getting the clients informed approval for a lower limit.

 

[pc1966]

Just to add, at 95mm the difference between 2C and 3C for 178m is quite a lot (like a few £000), so you might want to rely upon the armour for CPC. But in that case you may need a delay RCD at the supply to meet ADS and so an neutral-switching RCBO board to achieve selectivity for all final circuits.

Wrangling the damn stuff is another point, parallel 50mm might ease you pain a little.

 

[pc1966]

Another thought is to use 70mm 4C aluminium SWA with (ideally) diagonal pairs of cores paralleled to get 140mm 2C equivalent, which might be enough (not calculated for that) but it is also a major pain to deal with as sectoral, so really stiff, it will fatigue if flexed too much, and you need care with terminations to avoid galvanic corrosion.

We considered it for a project once, but in the end decided it would be better to pay the extra for copper to make our lives easier.