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Private network and grid connection earthing

Mark Swinn

Hi All 

I'm currently working on a project where a site is supplied via a private wire from a nearby power station unfortunately this connection has no spare capacity for the project as such we have approached the DNO for a a second connection to site one mandatory requirement they have made is that the earthing systems should be segregated, I struggle to understand how this can be achieved has anyone else been in this situation and how was it demonstrated that the earthing systems are segregated?

I have worked on sites that have two separate supplies (one from a docks ring and one from the DNO one at 11kV and one at 33kV) however we did have to  demonstrate any segregation of earthing .

Mark 

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    I agree with the sentiment above that you really need to speak to the DNO. Before you can consider the "How" you need to get clarity on precisely "What" and indeed "Why". Not meaning to be flippant but if it's boilerplate text (intended to be) saying your LV needs to be separated from their HV, that's a different kettle of fish to separating the HV earths, and if the latter understanding why will help determine how to go about achieving it. It could be something bespoke to your site relating to the existing supply.

    I wonder if the issue is transfer of ROEP from 33kV faults, or indeed 11kV faults if the earthing arrangements don't match, onto their network extending the hot zone to other customers who might otherwise have been cold, in which case I would guess the solution would look like an HV version of separating HV and LV earths, as others have said, though I don't know how you'd deal with the 11kV motor.

    It's certainly one for an earthing consultant though.

  • 0 in reply to Jam
    Jam said:
    I wonder if the issue is transfer of ROEP from 33kV faults, or indeed 11kV faults if the earthing arrangements don't match, onto their network extending the hot zone to other customers who might otherwise have been cold, in which case I would guess the solution would look like an HV version of separating HV and LV earths, as others have said, though I don't know how you'd deal with the 11kV motor.

    A further consideration (associated with that) may be that the design of the HV earthing systems is to different standards ... new one almost certainly latest guidance and BS EN 50522 in conjunction with BS EN 61936-1, whereas the existing could be to older guidance.

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  • 0 in reply to Jam
    Jam said:
    I wonder if the issue is transfer of ROEP from 33kV faults, or indeed 11kV faults if the earthing arrangements don't match, onto their network extending the hot zone to other customers who might otherwise have been cold, in which case I would guess the solution would look like an HV version of separating HV and LV earths, as others have said, though I don't know how you'd deal with the 11kV motor.

    A further consideration (associated with that) may be that the design of the HV earthing systems is to different standards ... new one almost certainly latest guidance and BS EN 50522 in conjunction with BS EN 61936-1, whereas the existing could be to older guidance.

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