Draft for Public Comment - IET Open combined protective and neutral (PEN) conductor detection devices (OPDDs)

The IET's new Standard (IET 01) includes definitions, requirements and tests for open PEN detection devices (OPDDs) and is now open for public comment, find out more here https://electrical.theiet.org/get-involved/consultations/iet-open-combined-protective-and-neutral-pen-conductor-detection-devices-opdds

Deadline for comments: Friday 2 February 2024.

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  • fine to discuss the contents, and arguably to do  so will lead to a more complete set of review comments.

    I cant disagree with that (indeed that was behind my initial reply) - I just had it in the back of my head that the distribution process in this case was slightly different from conventional "publishing" -  even if the trust levels are more like a 'gentleman's handshake' than 'two forms of photo ID'.

    That some sort of standard is being developed for PEN fault detection is an excellent step forward

    +1 for that! I'm in two minds though whether it should be an equipment standard in its own right, or merely additional requirements that should be read as supplementing existing standards (e.g. BS EN 61851 if it's built into a charge points or BS EN 60947-4-1 if added to something like a stand-alone contactor) - at the moment it seems to be attempting to be a bit of both, which seems to be adding an awful lot of bulk, but not a great deal of clarity.

    Pulsating direct current

    That definition caught my eye too - it seemed very odd to have 6mA limits built into the very definition of a quantity - rather than as a later requirement. I also noticed that the definitions around Earth Fault Currents were quite at odds with normal conventions (or BS 7671's version of the definitions at least) - especially that in a TN system earth fault currents don't actually have to flow through the general mass of the Earth at all. I've have to re-read the main body of the text to see if they're used to mean something different in this context.

    I did wonder if, given the introduction of appendix 17 of BS 7671, some recommendation regarding power consumption might be useful - given that these devices are likely eventually o be rolled out by the million, every 1W of unnecessary consumption by these devices will add MW of load to the national grid.

       - Andy.

  • ah yes 6mA not 60 well spotted. Still an odd definition, RMS or instantaneous peak I wonder?

    I do prefer either the tens or hundreds of the nearest smaller unit  or exponential notation (so many (units or tens of) mA, or 6E-3 A rather than decimal and zeros 0,0xxx)  as  mis reading is harder - especially when there are more than one leading zero. But then I also prefer  nine-uh rather than 'nine' over the phone to avoid confusion with 'no' or 'null'.

    There is a similar reason that on diagrams and parts lists electronics chaps commonly use the multiplier letters in the decimal point position - so  1k2 is equivalent to 1.2 k ohms, or 1200 ohms, but never normally written as   0.0012 Megs  (and 4M7 is 4million 7 hundred thousand,  8n2 is 8200pF etc

    Interesting idea about the idle power - and often overlooked for things needing an  internet connection which is often assumed to be free,

    For example power draw is now biting BT with their roll-out of domestic  fibre to the premises kit, which does not have a low power state to drop back to when the mains fails, making battery back up for power cuts for more than an hour or so uneconomically awkward. (so they do not bother to mention it ) 

    I reckon half the houses in the UK have an ADSL router taking 10-15 watts all the time to connect to the exchange over copper and to radiate WiFi broadcast packets, even when everyone is in bed, just on the off chance a packet arrives. That's a lot of Mw given the no of houses in the UK.

    To be truly 'green' there needs to be both a power limit for the kit, and a network traffic limit to save power elsewhere. In many ways, 'nega-watts' the power saved by unplugging something, are hard to beat.

    Mike

  • ah yes 6mA not 60 well spotted. Still an odd definition, RMS or instantaneous peak I wonder?

    I suspect (and it's still just a suspicion) that it's linked with the 6mA DC limit for A-type RCDs (and RDC-DDs if one has been incorporated into the EVSE) - so all bets are off if it's subject to a decent DC fault current for instance. If so it still feels to me it should be a functional requirement (or limitation on a requirement) rather than part of the definition of a quantity.

       - Andy.

  • I agree entirely - the definition of the phrase just need to clarify the peak value or some sort of time-average, and that although the current is varying with time, there is no reversal of direction, and then the test spec needs to say 'shall operate with more (or less) than a level of X or Y measured in the manner defined above'  as suits the situation.

    And as you say the large DC fault case needs to be handled separately for those odd cases where it is actually a credible failure mode.

    M

Reply
  • I agree entirely - the definition of the phrase just need to clarify the peak value or some sort of time-average, and that although the current is varying with time, there is no reversal of direction, and then the test spec needs to say 'shall operate with more (or less) than a level of X or Y measured in the manner defined above'  as suits the situation.

    And as you say the large DC fault case needs to be handled separately for those odd cases where it is actually a credible failure mode.

    M

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