and if you're wondering if these voltage ranges correspond to PE-Earth actually being below 70V in any way ... try this discussion:  Open PEN detection for 722.411.4.1 (iv)

   - Andy,

AJJewsbury said:

and if you're wondering if these voltage ranges correspond to PE-Earth actually being below 70V in any way ... try this discussion:  Open PEN detection for 722.411.4.1 (iv)

Agreed ... but to be clear, Regulation 722.411.4.1 (iv) does not mention a '70 V touch-voltage' condition, and therefore it is strictly not necessary to correlate the two, except for, perhaps:

• a manufacturer or designer risk assessing one approach vs another, although one of the reasons 722.411.4.1(iv) and (v) exist is that there are numerous instances where 722.411.4.1(ii) and 722.411.4.1(iii) are not practicable;
• theoretical discussion;
• technical interest;
• etc.

Thank you gkenyon and Jewsbury,  are all single-phase electrical systems in the UK derived from three phase electrical systems?

Normal grid voltage fluctuations may cause the voltage to exceed 253V or below 207V, when the load is too light or too heavy; I still don't understand how I can tell if the PEN is likely to break when the voltage is above 253V or below 207V. Or will the voltage be higher than 253V or lower than 207V when the PEN is open?

Thank you gkenyon and Jewsbury,  are all single-phase electrical systems in the UK derived from three phase electrical systems?

Normal grid voltage fluctuations may cause the voltage to exceed 253V or below 207V, when the load is too light or too heavy; I still don't understand how I can tell if the PEN is likely to break when the voltage is above 253V or below 207V. Or will the voltage be higher than 253V or lower than 207V when the PEN is open?

Young said:

Thank you gkenyon and Jewsbury,  are all single-phase electrical systems in the UK derived from three phase electrical systems?

No. In the public supply, the following are also used:

• Single-phase transformer (230 V supply, one live conductor is earthed to form what we still term 'neutral').
• Two-phase transformer (230/400 V supply, 120 degree phase shift, common line earthed to form neutral)
• Split-phase transformer (230-0-230, mid-point earthed to form neutral).

Note that whilst I've used 230 and 400 V being the usual stated nominal voltage, we often use higher voltage rating of transformers in the network because of voltage drop in the distribution lines, or to enable auto-voltage control via tap-changing.

Young said:

Normal grid voltage fluctuations may cause the voltage to exceed 253V or below 207V, when the load is too light or too heavy;

Voltage fluctuations can (and does) cause unwanted operation of the OPDD.

In the UK, we have legislative requirements that mean the voltage at the consumer's terminals (unless otherwise agreed with the DNO) ought to maintain these limits [for the majority of the time].

Young said:

I still don't understand how I can tell if the PEN is likely to break when the voltage is above 253V or below 207V. Or will the voltage be higher than 253V or lower than 207V when the PEN is open?

This link might help:  Open PEN detection for 722.411.4.1 (iv)

It was also explained in the Draft for Public Comment of IET Standard IET01 for the OPDD product ... that standard is currently planned to be available in Q3 of 2024.

Thanks Graham, In the UK,240V is a typical power grid voltage. According to the description in Appendix 2.15 of BS7671, the upper limit of 240V voltage is 6%, that is, 254.4V. In the case that the input voltage of charging pile is 240V, can the upper limit of PME fault detection be 254.4V?

Young said:

Thanks Graham, In the UK,240V is a typical power grid voltage. According to the description in Appendix 2.15 of BS7671, the upper limit of 240V voltage is 6%, that is, 254.4V. In the case that the input voltage of charging pile is 240V, can the upper limit of PME fault detection be 254.4V?

We are now after 1 January 1995, so we now use 230 V + 10 % / - 6 % at the origin. This is the supply voltage at the origin, 216.2 V to 253 V.

Regulation 722.411.4.1(iv) concerns the utilization voltage (i.e. the voltage, including volt-drop in the installation, being therefore the voltage range at the equipment) being 207-253 V.