Electric Vehicles - Impact on electrical network. Survey of vehicle uptake.

You can down-rate most car chargers to 16A 3.6kW if the supply isn't up to a 32A 7.2kW fast charger.  That should still be fast enough for most people



That is true, but the ADMD (After Diversity Maximum Demand)- that is the average power per house used to size the substations and the street mains for the 230V end of things - is not anything like as high as 16A per property, more like half that in most of the UK, so the if half of households on one substation want to charge one car at 16A,, then everything else in the street will need to be turned off to keep the substation within spec - the same point is reached when about 25% of households want to use  a 32A charger.

Substation transformers can and often do ride out overloads of more than 100% (twice the nameplate current) for the odd half hour, as the thermal mass of steel and oil allows this. A long slow change is not so helpful

I predict that some serious networks re-inforcement will needed when we get beyond the current state of  a few % of households having just one electric car - especially if there is a push to discourage gas for heating as well at the same time.


Mike

PS.


Surprise yourself with the ADMD figures in this PDF from UKPN  see  table 8-1 page 19


The data in pages 44-45  of this report on designing future proof LV networks  from northern powergrid is probably more realistic than national grid, in showing a near doubling of demand above the old ADMD curves if an electric vehicle is added.

Note how under the current LV network, (yellow curve) 100  users can be fed by a 250KVA transformer with a bit in hand. With EV in use (upper red, not so curved  curve) something nearer a 400kVA transformer is needed for the same no of households. The table below is the granular data to be used for when a very small no of houses share a transformer/ street cable, and a smooth curve is not applicable. I assume Yorkshire is not densely populated enough to warrant calculating the curve up to transformers of the 1MVA level just yet ?

You can down-rate most car chargers to 16A 3.6kW if the supply isn't up to a 32A 7.2kW fast charger.  That should still be fast enough for most people



That is true, but the ADMD (After Diversity Maximum Demand)- that is the average power per house used to size the substations and the street mains for the 230V end of things - is not anything like as high as 16A per property, more like half that in most of the UK, so the if half of households on one substation want to charge one car at 16A,, then everything else in the street will need to be turned off to keep the substation within spec - the same point is reached when about 25% of households want to use  a 32A charger.

Substation transformers can and often do ride out overloads of more than 100% (twice the nameplate current) for the odd half hour, as the thermal mass of steel and oil allows this. A long slow change is not so helpful

I predict that some serious networks re-inforcement will needed when we get beyond the current state of  a few % of households having just one electric car - especially if there is a push to discourage gas for heating as well at the same time.


Mike

PS.


Surprise yourself with the ADMD figures in this PDF from UKPN  see  table 8-1 page 19


The data in pages 44-45  of this report on designing future proof LV networks  from northern powergrid is probably more realistic than national grid, in showing a near doubling of demand above the old ADMD curves if an electric vehicle is added.

Note how under the current LV network, (yellow curve) 100  users can be fed by a 250KVA transformer with a bit in hand. With EV in use (upper red, not so curved  curve) something nearer a 400kVA transformer is needed for the same no of households. The table below is the granular data to be used for when a very small no of houses share a transformer/ street cable, and a smooth curve is not applicable. I assume Yorkshire is not densely populated enough to warrant calculating the curve up to transformers of the 1MVA level just yet ?