EV socket

AJJewsbury:

in accordance with 722.411.4.1 (iii) but does not require an earth electrode. If the claim is correct, am I missing something? For compliance with that indent, I thought that the only way it could be done was to provide a measurement electrode unless the unit was three phase.

AMD1 (2020) introduduced indent (iv) which covers this kind of approach - basically it opens if the L-N voltage is outside the 207 to 253V range - so really they should be claiming compliance with that rather than (iii) these days (or possibly (v) which appears to cover any other approach they haven't yet thought of).


I does seem to be a slightly flawed approach though - where the single phase supply is derrived from a 3-phase distribution system it's possible in some circumstances for a broken PEN in the 3-phase part to leave the L-N within the acceptable range even though N/PEN/PE is itself at a hazardous voltage above true earth.

Whilst factually correct, the whole picture is not quite that bleak for the basic 722.411.4.1 (iv) device. In a real open-PEN situation, the Neutral displacement shifts around in phasor space as connected loads change (in some cases, this can also be because those loads have "popped" due to overvoltage, or other loads have disconnected due to undervoltage).


Any additional monitoring a particular manufacturer could add to the basic picture can only improve safety.


From an installer's perspective, though, it's worth checking that you install the product at the correct point in the installation for the monitoring voltage, and the lower voltage (207 V) is of more concern. This is the lowest voltage that should be seen at the EV charging point - it's the utilization voltage. If the device is installed upstream of this, at the origin, the lowest voltage that should be seen by the device (trip voltage) is 216.2 V - the lowest supply voltage (in accordance with the ESQCR).


 

AJJewsbury:

in accordance with 722.411.4.1 (iii) but does not require an earth electrode. If the claim is correct, am I missing something? For compliance with that indent, I thought that the only way it could be done was to provide a measurement electrode unless the unit was three phase.

AMD1 (2020) introduduced indent (iv) which covers this kind of approach - basically it opens if the L-N voltage is outside the 207 to 253V range - so really they should be claiming compliance with that rather than (iii) these days (or possibly (v) which appears to cover any other approach they haven't yet thought of).


I does seem to be a slightly flawed approach though - where the single phase supply is derrived from a 3-phase distribution system it's possible in some circumstances for a broken PEN in the 3-phase part to leave the L-N within the acceptable range even though N/PEN/PE is itself at a hazardous voltage above true earth.

Whilst factually correct, the whole picture is not quite that bleak for the basic 722.411.4.1 (iv) device. In a real open-PEN situation, the Neutral displacement shifts around in phasor space as connected loads change (in some cases, this can also be because those loads have "popped" due to overvoltage, or other loads have disconnected due to undervoltage).


Any additional monitoring a particular manufacturer could add to the basic picture can only improve safety.


From an installer's perspective, though, it's worth checking that you install the product at the correct point in the installation for the monitoring voltage, and the lower voltage (207 V) is of more concern. This is the lowest voltage that should be seen at the EV charging point - it's the utilization voltage. If the device is installed upstream of this, at the origin, the lowest voltage that should be seen by the device (trip voltage) is 216.2 V - the lowest supply voltage (in accordance with the ESQCR).