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TT earthing at kiosk and Barn Stable with large distance between both

Duncan G

I have an install on a field to do where the supply comes in from a power networks overhead pole transformer to a kiosk roughly 8 meters away, in the kiosk there will be the DNO cut out / supplier meter / 100A switch fuse.

From here there will then be a 70mm 4 core swa running underground 250 meters to the barn where it will terminate using 2 cores for phase and 2 cores for neutral to comply with voltage drop allowance.

My question is do I earth stake the Kiosk end for earthing at that end so as to protect the armouring of the swa and housings of the switch fuse then earth stake at the barn with earth separation of the SWA to prevent 2 earth paths and what precautions do i need to consider as there will be horses at the barn. Your comments will be greatly appreciated. 

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  • 0

    “70mm 4 core swa running underground 250 meters” have you got a quote for the price of the cable?

    Why would stables need a 100 amp supply?

  • 0 in reply to Sparkingchip

    I assume its about £35 to 40 per metre, over that distance aluminium may be worth considering, it will be 1/3 the price for the same cross-sectional area.

    There is a good reason for the rule of thumb that much more than 1 volt per metre is not an economic cable run - so 11kv lines don't run much more than 11km, long vehicles use 24V batteries and not 12V etc. Oh, and like this, by the time mains has to go more than a couple of hundred metres, for all but very small loads it gets very expensive very quickly. This is also why pop festivals and fairgrounds have so many gensets dotted about, rather than one big one. (or temporary transformers and HV distro, but in the UK that is tricky.)

    Mike.

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  • 0 in reply to Sparkingchip

    I assume its about £35 to 40 per metre, over that distance aluminium may be worth considering, it will be 1/3 the price for the same cross-sectional area.

    There is a good reason for the rule of thumb that much more than 1 volt per metre is not an economic cable run - so 11kv lines don't run much more than 11km, long vehicles use 24V batteries and not 12V etc. Oh, and like this, by the time mains has to go more than a couple of hundred metres, for all but very small loads it gets very expensive very quickly. This is also why pop festivals and fairgrounds have so many gensets dotted about, rather than one big one. (or temporary transformers and HV distro, but in the UK that is tricky.)

    Mike.

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  • 0 in reply to mapj1
    mapj1 said:
    There is a good reason for the rule of thumb that much more than 1 volt per metre is not an economic cable run

    So would it be cheaper to get a new transformer installed?

  • 0 in reply to Chris Pearson

    would it be cheaper to get a new transformer installed?
    Probably not in the UK, because of the controls over private site HV work and ongoing cost of ownership, but if the only cost was buying and installing a transformer and a thinner cable, probably. It's only an approximate  rule of thumb !! This example is borderline, the economics at twice the distance would become far more clear cut.

    Note that 3 phase (or split phase) goes further, as you have drop in the phase wires, but a large chunk of the voltage drop in the neutral is removed from the  equation. Its also why lights on a larger sports stadia are often 400V units wired between 2 phases, rather than 230V phase to neutral.

    Mike

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