Double wound safety transformer for EV supply.

The transformer and housing are yet to be priced but I would think they will be cheaper than the ( insert manufacturer) cost quoted at £ 375.00 for a wall pod with Type B RCD, plus the electrode.

Since most cars seem to expect a mode 3 connection there's probably no getting away from a "wall pod" in some form or other - if you installed a simple BS EN 60309 (or BS 1363) socket then someone would have to buy a "granny lead" (i.e. a lead with all the wall pod gubbins built into it) in order to connect to most cars.  It's that gubbins that handles the communication with the vehicle - including telling it the maximum power available. It all depends on whether the charge point is for the exclusive use of one particular vehicle, or is intended for more general use.

 

But your point that manufacturers have an intelligent charger that senses the earth is important, do they send a current down the earth and monitor it back, and is this the reason for the Type B RCD's, as they give back a small DC monitoring fault ?

I don't know for sure but I would hope that they'd use a (tiny) a.c. signal to test the earth connection - just because prolonged d.c. currents are known to encourage corrosion in buried metalwork.

I wouldn't fancy being a cable jointer and finding during street mains connection alterations that several houses have EV's, and have just plugged them into wall sockets. The sum of the accumulation of potential  DC currents ( individually under 6 mA so the RCD Type B won't trip) in the PEN, when terminating, could be a major hazard. 

I doubt they would be that bothered (but wait to see if UKPN posts a reply). DNO's jointers are used to working live with tens if not hundreds of amps flowing in the PEN (they have various techniques of working that keeps the PEN continuous at all times) - a few hundred mA extra (d.c. or otherwise) wouldn't make much difference I suspect. If the PEN has to be cut then the lines are cut first, so any EVSE would loose power & disconnect so shouldn't be leaking anything (d.c. or otherwise) back to the mains. As I understand it high d.c. leakage currents are only really a problem where there are RCDs that could be disabled by it - and our DNOs don't do RCDs on the LV system.

and all the load being put onto one phase often L1.

I guess your option there, if you have more than one (single phase) charge point, is to share them around the available phases - e.g. connect the first to L1, the second to L2 and so on. If you have 3-phase charge points then rotate the phases (e.g.  connect L2,L3,L1 to the 2nd charge point and L3,L1,L2 to the 3rd and so on) so even if the vehicles only use what they see as L1, the load is better balanced from the installation's point of view.

 

but I am wondering why 722.413 has been left in ( Electrical separation). Perhaps just to allow future innovation or a separate rod just for the socket connection.

I suspect, from a regulation point of view, it's not so much that 722.413 is describing an extra option - that option is there anyway from the general body of the regulations (section 413 itself) - it's just regulating how section 413 should be applied within the context of EVSE. It might even be useful in some peculiar circumstances (e.g. a dedicated supply for a particular vehicle that didn't require an earth connection). An separate rod just for the socket (well usually the EVSE wall pod) would make it a TT system (still under 411) - actually a very commonly adopted solution.


   -  Andy.

The transformer and housing are yet to be priced but I would think they will be cheaper than the ( insert manufacturer) cost quoted at £ 375.00 for a wall pod with Type B RCD, plus the electrode.

Since most cars seem to expect a mode 3 connection there's probably no getting away from a "wall pod" in some form or other - if you installed a simple BS EN 60309 (or BS 1363) socket then someone would have to buy a "granny lead" (i.e. a lead with all the wall pod gubbins built into it) in order to connect to most cars.  It's that gubbins that handles the communication with the vehicle - including telling it the maximum power available. It all depends on whether the charge point is for the exclusive use of one particular vehicle, or is intended for more general use.

 

But your point that manufacturers have an intelligent charger that senses the earth is important, do they send a current down the earth and monitor it back, and is this the reason for the Type B RCD's, as they give back a small DC monitoring fault ?

I don't know for sure but I would hope that they'd use a (tiny) a.c. signal to test the earth connection - just because prolonged d.c. currents are known to encourage corrosion in buried metalwork.

I wouldn't fancy being a cable jointer and finding during street mains connection alterations that several houses have EV's, and have just plugged them into wall sockets. The sum of the accumulation of potential  DC currents ( individually under 6 mA so the RCD Type B won't trip) in the PEN, when terminating, could be a major hazard. 

I doubt they would be that bothered (but wait to see if UKPN posts a reply). DNO's jointers are used to working live with tens if not hundreds of amps flowing in the PEN (they have various techniques of working that keeps the PEN continuous at all times) - a few hundred mA extra (d.c. or otherwise) wouldn't make much difference I suspect. If the PEN has to be cut then the lines are cut first, so any EVSE would loose power & disconnect so shouldn't be leaking anything (d.c. or otherwise) back to the mains. As I understand it high d.c. leakage currents are only really a problem where there are RCDs that could be disabled by it - and our DNOs don't do RCDs on the LV system.

and all the load being put onto one phase often L1.

I guess your option there, if you have more than one (single phase) charge point, is to share them around the available phases - e.g. connect the first to L1, the second to L2 and so on. If you have 3-phase charge points then rotate the phases (e.g.  connect L2,L3,L1 to the 2nd charge point and L3,L1,L2 to the 3rd and so on) so even if the vehicles only use what they see as L1, the load is better balanced from the installation's point of view.

 

but I am wondering why 722.413 has been left in ( Electrical separation). Perhaps just to allow future innovation or a separate rod just for the socket connection.

I suspect, from a regulation point of view, it's not so much that 722.413 is describing an extra option - that option is there anyway from the general body of the regulations (section 413 itself) - it's just regulating how section 413 should be applied within the context of EVSE. It might even be useful in some peculiar circumstances (e.g. a dedicated supply for a particular vehicle that didn't require an earth connection). An separate rod just for the socket (well usually the EVSE wall pod) would make it a TT system (still under 411) - actually a very commonly adopted solution.


   -  Andy.