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O PEN Devices and Supplies

Just as a topic of discussion, O PEN devices are now required to be installed for EV chargers either inside a consumer unit or the Charger itself for TN-CS PME supplies 
when do you think it will become a requirement to fit these devices on final circuits or supplies where metallic objects are connected, for example kitchen appliances or protective bonding conductors connected to pipe work or the use of appliances outside surely the disconnection of the all conductors and CPC and bonding conductors is requirement in the event of this fault occurring. Any Thoughts ?  

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  • I’ve been thinking about this a lot recently and I’ve been asking myself why it’s taken EVs to bring in OPDDs…. In the UK there are 400 Open PEN faults recorded by the DNOs annually, 1% of these result in electric shock, 25% of which are serious resulting in hospital treatment or death (death is actually quite rare).

    The big problem with our network is the mishmash of earthing, you can go down a terrace and find properties still wired to the 15th edition right next to a recent rewire with a combination of all three earthing styles at different properties every 3 to 4 meters all the way down the street, in this situation is TT really TT if they have bonding on a gas pipe shared with TNCS gas pipe next door? Is a TT property safe next door to a PME installation where they both have outside taps and sockets only a couple of meters apart? It begs the question why so often the DNO doesn’t repair a high impedance fault on a TNCS when I report it, is it always appropriate to recommend an electrician comes to hammer in a rod? Would it be better to get onto converting the whole of suburbia to PME/TNCS? These are interesting questions and I’m sure they have different answers according to different on-site conditions where multiple factors increase and decrease the risks

    I think they’re likely to be used more and more and will follow a similar path to RCDs, AFDDs and SPDs. If we look at the career of RCDs first it was recommended in high risk situations, then slowly but surely as they were proven to safe lives and property the places where they were recommended or required was opened up to eventually include pretty much every domestic circuit excepting some distribution circuits. I foresee the same with OPDDs, starting with the next edition of the EV code of practice I suspect they will become the preferred option where an installation is PME and eventually I suspect all new TN installations will require one. 

    This emerging technology will save lives and take the pressure off the DNO.

    Ill just add that I have found that some makes of RCD will cut out when the supply neutral is lost (even without a load connected which contradicts my understanding of RCDs operation)  but others do not, would this not have been cheaper and easier to implement? 

  • I’ve been thinking about this a lot recently and I’ve been asking myself why it’s taken EVs to bring in OPDDs…. In the UK there are 400 Open PEN faults recorded by the DNOs annually, 1% of these result in electric shock, 25% of which are serious resulting in hospital treatment or death (death is actually quite rare).

    Detecting the fault is one thing ... what do you want to do when you've detected it?

    Disconnecting L and N, even at the meter, doesn't take the problem away. The only real way (because of actual or fortuitous "bonding" downstream of the protective device) is to fit the disconnector preferably immediately before the piece of current-using equipment that the person may be touching.

    Makes the "disconnecting device" approach OK for a single EV (as the EV itself is insulated by tyres from the ground, and hopefully other metal) but not for installations, or groups of circuits, and indeed certain circuits with fixed installed equipment (like boilers) on them.

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  • I’ve been thinking about this a lot recently and I’ve been asking myself why it’s taken EVs to bring in OPDDs…. In the UK there are 400 Open PEN faults recorded by the DNOs annually, 1% of these result in electric shock, 25% of which are serious resulting in hospital treatment or death (death is actually quite rare).

    Detecting the fault is one thing ... what do you want to do when you've detected it?

    Disconnecting L and N, even at the meter, doesn't take the problem away. The only real way (because of actual or fortuitous "bonding" downstream of the protective device) is to fit the disconnector preferably immediately before the piece of current-using equipment that the person may be touching.

    Makes the "disconnecting device" approach OK for a single EV (as the EV itself is insulated by tyres from the ground, and hopefully other metal) but not for installations, or groups of circuits, and indeed certain circuits with fixed installed equipment (like boilers) on them.

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