Changing gear
Released in February, the first amendment to BS 7671:2018 saw changes to the section that covers electric vehicle charging installations. Here, we outline the revisions and how they impact the fitting of this rapidly-developing technology
The Scottish Government’s plans for de-carbonisation of the environment are intended to help cut the levels of carbon in the atmosphere and reduce air pollution in our cities. However, these measures are also providing opportunities for enterprising electrical contracting businesses who may be looking to diversify into new areas of work.
The announcement to end sales of new petrol and diesel cars and vans by 2032 is one particular area which may interest these businesses. Such a move will require significant investment to provide a charging infrastructure throughout Scotland to power the electric vehicle (EV) revolution currently gathering pace as we move forward into the decade ahead.
Those who possess the necessary knowledge and skills should be well placed and much in demand to become involved with this – however, appropriate training will be necessary. This will also help such businesses to satisfy current industry competence requirements and enable installers to become ‘approved installers’ which is a requirement to access government incentives on behalf of customers, e.g. the Office for Low Emission Vehicles (OLEV) home charge scheme, which provides up to £500 of grant funding for such installations.
As a minimum, the starting point to satisfying competence requirements should be qualification as an electrician with up-to-date knowledge of requirements in BS 7671:2018 but also with specific knowledge of the requirements given in Section 722 Electric Vehicle Charging Installations.
This type of installation is one of the special installations or locations given in Part 7 of BS 7671:2018. However, section 722 requirements have recently been amended with the publication of Amendment 1:2020 to BS 7671:2018.
When does A1:2020 come into effect?
A brief overview of some of the amended requirements is provided below for guidance.
New symbols
New symbols are included in the list of symbols given in Part 2 of BS 7671:2018 including a symbol for Cmax.
Cmax is defined as the maximum voltage factor to take account of voltage variations depending on time and place, changing of transformer taps and other considerations and for a low voltage supply given in accordance with the ESQCR is given the value of 1.1.
This is used in the calculation of load balance and earth electrode resistance and makes an adjustment for the worst conditions of fault current that may exist during a fault which would be
253 V for a supply given with a nominal voltage of 230 V.
Load curtailment
When determining the maximum demand of an installation, load curtailment, including load reduction or disconnection, either automatically or manually, may now be taken into account.
Load curtailment is similar to load shedding, where electrical loads are switched off for variable periods of time to optimise demand.
PME earthing facility
Regulation 722.411.4.1 now requires that a PME earthing facility shall not be used when charging outdoors unless one of the five methods given is used. These are basically as follows:
A balanced three-phase installation
The main earthing terminal of the installation is connected to an additional earth electrode
A device which electrically disconnects line, neutral and protective earth connections, when the supply voltage is greater than 70 V between the protective conductor and earth
A device which electrically disconnects line, neutral and protective earth connections, when the supply voltage is greater than 253 V or less than 207 V rms
An alternative device to options iii or iv above which does not result in a lesser degree of safety.
Previously only options i, ii and iii were given but these were not likely to be used as the requirements are difficult to satisfy. However, manufacturers of EV charging equipment are now developing products which incorporate safety devices in the EV charging equipment and the two new options reflect this.
Please note that with regard to using these options, the designer of the EV charging installation retains overall responsibility for establishing the safety of the installation.
It is also highlighted that it may not always be possible to achieve adequate separation distances between different earthing systems when using one of the five options, therefore connection to a TT earthing system may be an alternative option.
RCD protection
Requirements for RCD protection of the charging point socket–outlets or vehicle connector and specific protection against DC fault current have also now been clarified.
The requirements for RCD protection refer to the EV charging point itself as opposed to the final circuit supplying the equipment.
However, there may be other requirements for RCD protection such as for fault protection, if the circuit were connected to a TT earthing arrangement. If this is the case, it is important to select the correct type of RCD and to ensure selectivity upstream from the charging equipment RCD.
Regulation 722.531.2.101 requires the charging point to be protected by its own RCD having a residual operating current not exceeding 30mA, unless electrical separation is used.
This should also protect against DC currents, except where this protection is provided by the charging point, and be either Type B or Type A or F in conjunction with a residual current detecting device (RDC-DD).
Annex A722
Guidance given in Annex A722 for TN systems where PME conditions apply has been updated and includes sample calculations if adopting methods i, ii or iii for connection to a PME earthing system given in Regulation 722.411.4.1.
Toolbox Talks
Electric vehicle charging was one of the subjects due to be discussed at our Toolbox Talks. With the events now cancelled due to coronavirus, keep an eye out for the alternative methods in which we will deliver this information.
Businesses who want to become involved in this area of work may be interested in SELECT’s Electric Vehicle Charging Equipment Installation training course (City & Guilds 2919-01-02).
However, it should be noted that those who are seeking to become an Approved Installer with OLEV may also need to undertake additional manufacturer product-specific training.
For further information, please contact SELECT Training on 0131 445 5577 or email training@select.org.uk
