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Latest developments in international standards for supplies for electric vehicle (EV) charging revisited

In this article, we revisit some of the international standards for electric vehicle (EV) charging and look at some of the latest developments.

The UK is actively involved in the development of international standards. It is worth noting at this stage, the relationship between, for example, the British standard (BS 7671) and the European and international standards for electrical installations. The IET Wiring Regulations (BS 7671) are based on European standards, which in turn are generally based on international standards. The International Electrotechnical Commission (IEC) is the oldest of the international standardization organisations. It was founded back in 1906 with the support of seven countries. The IEC is an international non-governmental organisation whose members are the National Electrotechnical Committees or standards bodies (like the British Standards Institution (BSI) in the UK).

Work on the first edition of IEC 60364-7-722 - Supplies for electric vehicles, was initiated back in 2009 (14 years ago) and the first edition was published in February 2015. This was developed to answer the needs of the EV market in terms of safety of supply of EV installations, reliability, and proper functioning of the supply. 

Work on a second edition started in 2015 and was published in September 2018. This second edition is still current but under review to keep pace with the progress of EV charging.

The second edition includes a number of significant points worth noting.

Wireless power transfer

Most people involved in electrical installations for EV charging are familiar with conductive charging systems, where the EV is plugged into a charging point to charge the vehicle battery. However, IEC 60364-7-722 Edition 2 recognizes wireless power transfer (WPT) systems for EVs and requires compliance with the appropriate parts of the IEC 61980 series. These are new and emerging technologies.

(It is important to note that inductive charging is currently outside of the scope of Section 722 of the IET Wiring Regulations, BS 7671:2018+A2:2022).

BS EN IEC 61980 series is published in several parts. BS EN IEC 61980-1:2021 Electric vehicle wireless power transfer (WPT) systems was published on 31 January 2021.

Part 1 covers general requirements for electric road vehicle (EV) WPT systems, including general background and definitions (e.g., efficiency, electrical safety, EMC, EMF).  Part 1 applies to the supply device for charging electric road vehicles using wireless methods at standard supply voltages up to 1,000 V AC and up to 1,500 V DC.

In addition, Part 1 also applies to WPT equipment supplied from on-site storage systems.

Aspects covered include the characteristics and operating conditions of a supply device, communication between the EV device and the vehicle, and specific EMC requirements for a supply device.

Part 2 of BS EN IEC 61980 was published on 30 June 2023. This part of BS EN IEC 61980 addresses communication and activities of magnetic field wireless power transfer (MF-WPT) systems.

The requirements in this document are intended to be applied for MF-WPT systems according to IEC 61980‑3 and ISO 19363 - Electrically propelled road vehicles.

Aspects covered include operational and functional characteristics of the MF-WPT communication system and related activities, and operational and functional characteristics of the positioning system.

Part 3 of BS EN IEC 61980 was published on the 28 February 2023 and covers specific requirements for magnetic field wireless power transfer systems.

This part of IEC 61980 applies to the off-board supply equipment for wireless power transfer via magnetic field (MF-WPT) to electric road vehicles for purposes of supplying electric energy to the rechargeable energy storage system (RESS) and/or other on-board electrical systems. The power transfer takes place while the EV is stationary.

Aspects covered include:

  • electrical safety;
  • characteristics and operating conditions;
  • basic communication;
  • requirements for positioning for power transfer; and
  • specific EMC requirements.

EV operating as a source in parallel with other sources

The current standard (IEC 60364-7-722 Edition 2) recognizes the case where the EV may operate as a source in parallel with other sources and states that where EVs are intended to feedback energy to the electrical installations, the requirements of IEC 60364-8-2 Prosumers low-voltage Electrical Installations apply. However, the standard does state that additional requirements for circuits intended for feeding back electricity from EVs are under consideration. Therefore, this is expected to be a future development.

(In the UK, Section 722 of the IET Wiring Regulations (BS 7671:2018+A2:2022) makes it clear that requirements for precautions on supply of the fixed installation by the EV are under consideration. Section 551 covers low-voltage generating sets. It is important to note that in the UK there are mandatory requirements concerning the parallel connection of generators with the supply network, and the Energy Networks Association (ENA) publishes Engineering Recommendations G98 and G99 concerning connection of generators.

Charging modes

IEC 60364-7-722 Edition 2 makes reference to IEC 61851 Electric vehicle conductive charging system. IEC 61851 describes the charging modes.

(Charging modes are described in Part 2 (definitions) of the IET Wiring Regulations BS 7671:2018+A2:2022).

Mode 1 charging: connection of the EV to the AC supply network utilizing standardized socket-outlets not exceeding 16 A and not exceeding 250 V AC single-phase or 480 V AC three-phase, at the supply side, and utilizing the power and protective earth conductors. IEC 61851 highlights restrictions at national level on the use of Mode 1.

Mode 2 charging: connection of the EV to the AC supply network utilizing standardized socket-outlets not exceeding 32 A and not exceeding 250 V AC single-phase or 480 V AC three-phase, at the supply side, and utilizing the power and protective earth conductors together with a control pilot function and system of personnel protection against electric shock (RCD) between the EV and the plug or as part of the in-cable control box.

IEC 61851 highlights the need for household and similar sockets and plugs for EV charging to be suitable.

Generally, Mode 2 is the minimal charging solution for single phase domestic socket-outlets. It usually provides charging currents of 10 A or less.

Mode 3 charging: connection of the EV to the AC supply network utilizing dedicated EV supply equipment where the control pilot function extends to control equipment in the electric vehicle supply equipment, permanently connected to the AC supply network.

IEC 62196-2 gives details of vehicle inlet and vehicle connector Type 1 and Type 2 and Type 3 for Mode 3 charging. A mechanical or electromechanical means must be provided to prevent intentional and unintentional disconnection under load of the vehicle connector and/or plug according to IEC 62196-1.

Mode 3 recognizes various levels of charging currents. A typical Type 2 Mode 3 charging point could be 32 A (7.2 kW).

Mode 4 charging: connection of the EV to the AC supply network utilizing an off-board charger where the control pilot function extends to equipment permanently connected to the AC supply.

A mechanical or electromechanical means must be provided to prevent intentional and unintentional disconnection under load of the vehicle connector and/or plug according to IEC 62196-1.                                       

One of the advantages with Mode 4 charging is that it can provide fast high-power charging. When charging a vehicle from an AC output charge point, the charging power is often limited by the on-board battery charger of the EV. With (Mode 4) DC charging, DC power is provided directly to the battery system and is not limited by the on-board battery charger of the EV.

Therefore, Mode 4 charging appears to be suited for use at motorway services, shopping centres, and busy urban areas where a fast charge is required to minimize charging time.

Conclusion

This is only a brief overview and highlights some of the significant points in the current IEC standard. For more information, refer to IEC 60364-7-722 Edition 2.

Important: please note these are requirements at international level (world standards) which may or may not be incorporated in BS 7671 in the future.

Finally, it is worth noting that in the UK, the Building Regulations in England, Wales, Scotland or Northern Ireland have requirements for EV charging infrastructure depending on the location. For example, in England the government has introduced Approved Document S (Infrastructure for charging electric vehicles).