Indent (i) was about 3-phase installations that had extremely well balanced loads, so that even if the supply PEN conductor became severed, the consumer's end of it would remain at a safe voltage (pretty impossible to guarantee in practice),  so that one's deletion probably isn't relevant.

The other change, the removal of the single phase condition from intent (iv) however, does open the door to using L-N voltage sensing open-PEN devices on installations with 3-phase supplies.

Just be aware that there are disadvantages to the L-N voltage sensing approach to open-PEN detection - specifically that where a 3-phase distribution system is involved it is possible, under certain conditions, for c.p.c to be at a hazardous voltage but the L-N voltage still to be within normal range. So as a designer you might like to consider whether alternatives might be better choices. 3-phase open-PEN detectors that compare the PE or N voltage with an artificial N point created from the 3 lines, don't suffer that particular blindness for instance. Or where tbe EV and EVSE would be well away from anything on the PME system, TT might be an option.

   - Andy.

AJJewsbury said:

it is possible, under certain conditions, for c.p.c to be at a hazardous voltage but the L-N voltage still to be within normal range.

Whilst what Andy said here is true, it's not a statement  that can easily be demonstrated to be low or high probability of serious electric shock in given circumstances, and is certainly not the whole picture.

This seemingly simple statement ignores the fact that rarely in three-phase systems is the phase balance maintained for long periods. In a real broken neutral situation, the line to neutral voltages on all phases constantly change. So if the broken PEN conductor is initially undetected, that situation will not persist continuously. If you have EV charging loads with the single-phase voltage monitoring open-PEN devices on all 3 phases, it is highly improbable that devices on all 3 phases will be "blinded" at the same time; in fact, the conditions are such that it's highly likely devices on two other phases will operate. This will change the phase balance very quickly, making it extremely likely that the remaining phase, on which OPDDs were originally "blinded" now see an "out of range" voltage in a relatively short time after the event.

In a similar way, the operating characteristic of 30 mA RCDs is not guaranteed to protect children ... that doesn't mean we can't use them and they are useless - they offer more protection than not having the RCD., but they wont' protect 100 % of people 100 % of the time.

Thanks for reply, 

Thanks

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