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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?

  • 0

    Before that, I'd ask, are the lamp posts class 1, and if so are they earthed to the same thing as the EV charger ? If all they do is introduce a potential similar to that of the soil beneath the car, then the risk is more or less unchanged.
    Mike.

  • 0 in reply to mapj1

    Hi Mike, so this is where we are hhaving great difficulty - the DNOs and local authorities are proving very difficult in terms of confirming the earthing arrangements. 

    Its about a 10-15 % success rate in repects to answers from them. 

  • 0
    Dom said:
    Open‑PEN fault detection

    Some work simply by detecting Line-to-Neutral (L-N) voltage range of 207 V to 253 V.  Outside of that range they state as a fault and disconnect.  It is worth remembering the UK's Distribution Network Operators (DNOs) have proposed to adjust the statutory lower mains voltage limit from 216 V to 207 V.  Thus leaving very little room for error or fluctuation

  • 0

    where customers have lamp posts located within their driveways.

    Are we talking about customer's own private lighting columns (presumably fed from their own installation) or public street lighting that happens to be within reach of the driveway?

       - Andy.

  • 0 in reply to AJJewsbury

    Hi Andy, in the scenario I am speaking about these sim contacts would be primarily street furniture supplied by the DNO remote from the customers supply. I will try and get some images to help here 

  • 0

    I would love to know what others in industry are doing around this problem. I havve exhausted every avenue and I am in contact with some of our governing bodies. I suppose the main question for me is the validity of the layered protection model?

  • 0 in reply to Dom

    Hmm, the lamp posts being out of your control is tricky.  Even if you could stab the lamp post with a wander lead and verify a very low resistance to the house earth, thats only probably verifying the same substation and street main, its all a bit impractical to rely on. 

    I'm intrigued by your proposed  bi‑directional earth leakage monitoring - what are you proposing to clamp around what exactly to do that, and then what would you disconnect if it was detected ? I'm envisaging problems with false alarms from diverted neutral current between CPCs and terra-firma earth.

    The rest (O-PEN and RCD) are probably already there most of the time .

    Mike.

  • 0 in reply to mapj1

    I'm intrigued by your proposed  bi‑directional earth leakage monitoring - what are you proposing to clamp around what exactly to do that, and then what would you disconnect if it was detected ? I'm envisaging problems with false alarms from diverted neutral current between CPCs and terra-firma earth.

    I think that a feature found in some open-PEN EVSEs - triggers when the c.p.c. is found to carry 21mA or more (possibly method M3 in IET 01) - it's a bit of a mitigation to try and fill in some of the holes in the voltage measuring approach when used on supplies derived from 3-phase distribution systems). Given the vehicle is normally on rubber tyres and hopefully hasn't been crashed into steel barriers diverted currents hopefully shouldn't be too much of an issue. (Open PEN devices aren't permitted to have bonds to extraneous-conductive-parts downstream of the device).

       - Andy.

  • 0 in reply to AJJewsbury

    If its that, and it operates the same all poles (include CPC) as the O-PEN then that's pretty good. If it really is looking at the current into the car in free space I'd argue you could make it a lot friskier than 21mA without ill effect, parking into the fence or very muddy tyres notwithstanding.

    M.

  • 0 in reply to mapj1

    The clamp proposal has now been put on hold due to sizing restrictions sadly. 

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