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Simultaenous Contact

Dom

Good afternoon all, 

I am seeking the collective views of the group regarding the issues we are currently encountering within the EV installation environment in relation to simultaneous contact.

In simple terms, we are seeing a significant number of installations where customers have lamp posts located within their driveways. In many of these cases, it is not possible to achieve the recommended 2.5‑metre separation distance.

My position is that, where physical separation cannot be achieved, the application of layered protection at the EV charge point and associated switchgear would leave the customer in no worse position than prior to the installation. It is accepted that the proposal only outlines protection on the vehicle, but there are no other solutions for industry, are we with the protection detailed taking enough measures to carry out an install and in affect leave the install without a subsantial increase in risk?

My proposed approach to managing simultaneous contact risk would follow a structured hierarchy as set out below:

  • Can the maximum separation distance be achieved?
  • Can barriers or enclosures be installed to prevent simultaneous contact?
  • If neither of the above options are achievable, can layered protection provide an acceptable level of risk mitigation?

With layered protection, the proposed measures would include:

  • Installation of a compliant open‑PEN (O‑PEN) protective device
  • Provision of a double‑pole 30 mA Type A RCBO
  • Use of a charge point - M3 21 mA protection

Based on the above, the assumption is that, if all protective measures are correctly installed and verified, the installation would incorporate:

  • Automatic disconnection within the required times
  • Residual current protection
  • Open‑PEN fault detection

This combination of protections would significantly reduce the likelihood of a fault condition persisting for any meaningful duration.

On this basis, the key question for consideration is:

Where physical separation and barriers are not achievable, would it be considered acceptable to proceed with installation relying on this layered protection approach?

Parents
  • 0

    This is the kind of issue we are seeing folks.

  • 0 in reply to Dom

    Moved over for you   Slight smile

  • 0 in reply to Dom

    Is it possible that

    L1 property on the left

    L2 property on the right

    L3 Street light

    Extra question... is the street light protected by 30mA RCD?  Are both properties protected by RCD?

    There could be several scenarios here

    All working as intended

    Single on L1, L2 or L3 site

    Multiple faults.

    Personally I think it is prudent for all street lighting and street furniture be 30mA protected but there is a school of thought that thinks that true street lighting such as on motorways should not have RCD protection due to the fact that a fault will leave everything in darkness.  I assume the same applies when darkness is more dangerous than light, like maybe a railway platform.

  • 0 in reply to Sergio Fernandez

    Entirely possible that they're fed from different phases - in fact it's quite normal for houses down a street to be fed from different phases in turn - it helps to balance things and minimise N voltage drop. That's not normally a cause for concern though (if fact if you have multiple L-PE faults on different phases, the PE voltage tends to cancel out, making the situation if anything marginally safer!). Normally all three phases share the same PE(N).

    The main fault of concern if of course a broken PEN conductor ... for which RCDs provide no benefit.

       - Andy.

  • 0 in reply to Lisa Miles

    Thank you Lisa, you are a star :) 

  • 0 in reply to Sergio Fernandez

    At the moment - it is very hard to determine the phases for street furniture as legally we are not allowed to touch them. Thereis also the issue of isolation, etc. However the phasing issue is not as much a concern for me. The reality is the likelihood of a fault causing an issue compared to the actual volume of real life issues we see. The whole problem needs quantified. 

  • 0 in reply to AJJewsbury

    Yes agreed, in reality the street furniture has no O-pen protection and unlikely to have RCD protection as well, however the EV charge point does, as well as an RCD and M3 protection on the charge point. 

  • 0 in reply to AJJewsbury

    If the main fault issue is a PEN / Broken PEN then surely that is an issue for the DNO to implement a monitoring system not the humble Electrician or the humble home owner.  Probably a round table discussion for IET and ESQR team?

  • 0 in reply to Dom

    Another thought, what about a possible voltage offset between the CPCs of adjacent properties as I'm pretty sure not all the installers check the electrode resistances.  Maybe a simple answer could be to build a wall between the properties and maybe fork off around the street lamp.  This would then give you a physical fire proof barrier which COULD remove the Simultaenous Contact issue all together.  Not sure what the correct height for the wall would be but lets say for the sake of this discussion about let say 1m50cm

  • 0 in reply to AJJewsbury

    Very common to cycle the 3 phases for houses in turn as you go down the street but lights often are on their own radial so small groups of  street lights can be isolated for maintenance.  As such they could be on any phase, and maybe not even the same transformer.  

    That opens an even bigger can of worms.


    It might be safer to charge the car stealing a supply from the street lamp, and certainly cheaper until you are found out ! Joking aside, the sort of situation in the picture is both unavoidable with on street charging and horrid.

    The neatest solution would be some kind of a non-conducting street lamp sleeve., but I'm not aware of one.

    Mike.

  • 0 in reply to mapj1

    What about the classic UK concrete lamp post from 1930 to 1990's.  Granted they were a bit heavier and .............

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  • 0 in reply to Sergio Fernandez

    classic UK concrete lamp post  well, yes,  although  partly conducting when wet of course. Ideally when combined with the related 

    classic UK TNS earthing,  also starting from about 1930.. .   Sadly both seem to have largely gone.

    The interconnection of earths to street lamps and adjacent house supplies is the sort of thing that only the DNO can sensibly keep control or have records of, and even they may well not.
    Mike.

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