Amendment 1 to BS7671

For those of you in the UK, or where the electricity regulations are modelled on the UK’s, the IET informs me that:

“We worked with BSI to release Amendment 1 to BS 7671:2018 (18th Edition IET Wiring Regulations) at the beginning of February. This guidance provides a more practical solution for Electric Vehicle Charging Installations to help support the rollout of the electric vehicle charging infrastructure across the UK. Amendment 1 is now available as a free-to-view PDF.”

It’s good having things where we can see them.

Thanks for sharing Robert.

1 Like

Thanks for sharing, it’s great they are making updates like this free and easy to read.

As far as I can see there is nothing new with regard to EV charging protection, they have just been a bit more descriptive of the types of automatic disconnection devices in the event of an O-PEN fault.

I’ve always worked on the basis that Zs for TT earth electrodes must be ≤120 ohm since this is the highest value a Renault Zoe will accept (the most picky EV for earth loop impedance since the Zoe uses the motor windings as part of the onboard charger so not much isolation between AC and HV DC). Interesting Amendment 1 includes a formula to calculate earth electrode resistance:

However, I can’t seem to find any reference to what U0 or Cmax is, do you have any insight?

Uo is the nominal supply voltage.
Cmax & Cmin are the voltage factors to take account of voltage variations depending on time and place, changing of transformer taps and other considerations.

You probably need to have a copy of BS7671 itself - 18th Edition resources - Electrical

1 Like