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Use of PME not allowed, special locations

Alan M Walton

   Some Special locations won't allow PME to be used.which I understand.  However with  EV charging points. We can overcome the PEN fault by automatic disconnection of supply is described in 722.411.4.1(iii).

    So why can't we use the same logic in other locations. Where lost of supply doesn't  in danager life or property.

   

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  • Alan M Walton said:
    So why can't we use the same logic in other locations.

    Which ones in particular?

    There are some problems with PME in some special locations, that differ from the general "electric vehicle" approach.

    Caravan sites - Section 708 - and Marinas and shore connections for inland navigation vessels - sections 709 and 730 - issue here is ESQCR prohibits distributor's PME earthing terminal being used (legal issue).

    Caravans and Mobile & Transportable Units ... EV (usually on tarmac) different to caravans and mobile & transportable units on muddy fields.

    Diverted neutral currents in water can be problematic at lower levels than those which would lead to touch voltages at 50 V AC or more on PEN conductors (as sometimes noted in swimming pools) being another reason why open-PEN (as set up for EV) may not be suitable there even if legislation permitted.

  • in reply to gkenyon

    I'm just opening a debate and getting my head around the subject of automatic PEN disconnections.

    Most of these the potential difference measured from an artificial/ calculated base voltage.why can't we make them measure the difference between the actual supply earth potential and the true earth potential. Once there is a harmful difference the supply could be disconnected including separating the different earth's. If there no supply or PME there's no path for the high true earth voltage to leak back In to the installation. 

    All I'm thinking is that we rely on a TT earning arrangement and hope the RCD protect us. Whilst still there could still be a high true voltage present. Which  isn't been addressed.  If there wasn't any power it would be looked into.

    Sorry If I used the wrong terms. I'm just trying  to get my head around it and looking for the future.  Except places where supply is always needed.ie. Hospital's.  Surely identifying the problem and solving it is better than copping with it.

    Hope I'm making some sense in my maddness.looking forward to more educated thoughts.

  • in reply to Alan M Walton

    Healthy engineering debate is always good.  It is how we make things better

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