Tag Archives: IET

Wiring Matters – Issue 81 – July 2020

Wiring Matters – Issue 81 – July 2020

Here is what you will find in the July 2020 (Issue 81) of the IET Wiring Matters magazine.

History of insulation resistance testing

There has been a lot of activity on the IET Engineering Communities forum recently regarding the background of the 1 megohm minimum value for insulation resistance. Let’s take a look at how this value was arrived at in BS 7671:2018+A1:2020.

Draft for Public Comment: IET Code of Practice for Electrical Energy Storage Systems, 2nd Edition

The IET are happy to announce that the Draft for Public Comment for IET Code of Practice for Electrical Energy Storage Systems 2nd Edition is now live.

This Code of Practice looks at Electrical Energy Storage System (EESS) applications and provides information for practitioners to safely and effectively specify, design, install, commission, operate and maintain a system. This 2nd Edition has been updated to take account of developments in the industry, and progress in standardisation.

The all-new 5th Edition of the IET Code of Practice for In-Service Inspection and Testing of Electrical Equipment

In this article, James Eade, author of the 5th Edition, gives a brief insight into the changes to this important Code, due for publication later this year.

Amps per Pound

The idea of sizing a cable to reduce energy loss in distribution is nothing new and has been considered for many years, but with competitive tendering for work and the continual search for cost reductions (also known as ‘value engineering’), the modern design of an electrical installation tries to reduce the materials utilised to a minimum.

Asbestos guidance for electricians

Asbestos was widely used in building construction, both as a building material and for its useful insulation and fire protection properties, for many years during the 20th century.

Its use was progressively reduced between the 1970s and 1999 when all remaining forms were finally prohibited in the UK with the implementation of the Asbestos (Prohibitions) (Amendment) Regulations 1999. Asbestos has also been removed from various properties over the years for various reasons, for example, because of damaged material, or for refurbishment and demolition, but a substantial proportion of the original products still remain. These materials, if undetected, can present an ongoing risk to workers carrying out building repair and maintenance or improvement and refurbishment work. Workers at potential risk include electricians and other building trades. 

Amendment number 1 to BS 7671:2018+A1

Amendment 1 of BS 7671:2018 was published at the beginning of February this year and may be implemented immediately. The amendment concerns Section 722 of BS 7671:2018 (electric vehicle charging installations). In this article, we give a brief overview of some of the main changes to Section 722.

Protection against electric shock

Regulation 722.411.4.1 concerning the use of protective multiple earthing (PME) supply has been redrafted. Indent (iii) has been fully revised. In addition, Regulation 722.411.4.1 now includes an additional indent (iv) to cover single-phase installations and a further additional indent (v) has been added. Regulation 722.411.4.1 does not allow PME to be used to supply an electric vehicle (EV) charging point located outdoors (or that might be used to charge a vehicle located outdoors) unless you meet (i) or (ii) or (iii) or (iv) or (v) of 722.411.4.1.

A summary of the requirements of the indents to Regulation 722.411.4.1 is as follows.

Regulation 722.411.4.1(i) refers to a situation where a connecting point is supplied from a three-phase installation used to supply loads other than charging points and where the load is sufficiently well balanced.

Regulation 722.411.4.1(ii) requires a very low resistance earth electrode to mitigate the effects of an open-circuit (PEN) conductor fault on the supply.

Regulation 722.411.4.1 (iii) has been revised and refers to a voltage monitoring device (or functionality within the charging equipment) that detects PEN conductor failure. The informative Annex to Section 722 describes that suitable arrangements include measurement of the voltage between either:

   a. the circuit protective conductor (CPC) and a suitable measurement earth electrode, or
   b. the CPC and a reference point derived from the line conductors of a three-phase system provided that suitable precautions are also taken to disconnect the device when the supply to one or more of the line conductors is interrupted.

Regulation 722.411.4.1 now includes an additional new indent (iv) to cover protection by a device (or functionality within the charging equipment) for a single-phase installation.

Finally, Regulation 722.411.4.1 includes an additional new indent (v), which allows protection against electric shock to be provided by the use of an alternative device to those in (iii) or (iv), providing that it does not result in a lesser degree of safety than using (iii) or (iv). The indent states that equivalent means of functionality could be included within the charging equipment.

The touch voltage threshold of 70 V mentioned in Regulation 722.411.4.1 is on the basis that Table 2c (ventricular fibrillation for alternating current 50/60 Hz) of IEC 60479-5{ed1.0} gives a value of 71 V for both-hands-to-feet, in water-wet conditions with medium contact area (12.5 cm2).

Regulation 722.411.4.1 includes some important notes. Note 5 explains that BS 7671 does not deal with the safety requirements for the construction of electrical equipment. Where equipment to be used is not covered by a British or Harmonized Standard, the electrical installation designer should establish that the manufacturer of the equipment has ensured that the equipment satisfies the safety objectives of the relevant directive(s).

Note 6 states that creating a TT earthing system for charging equipment or for the whole installation, as an alternative to using a PME earthing facility with one of methods (i) to (v) above, may not be an appropriate solution, due to the inability to provide sufficient separation from buried metalwork connected to the supply PEN conductor.

What is protective multiple earthing (PME)?

The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) (as amended) permit the distributor to combine neutral and protective functions in a single conductor, provided that (in addition to the neutral to Earth connection at the supply transformer) there are one or more other connections with Earth. The supply neutral may then be used to connect the CPCs of the customer’s installation with Earth if the customer’s installation meets the requirements of BS 7671.

PME has been almost universally adopted by distributors in the UK as an effective and reliable method of providing their customers with an earth connection. Such a supply system is described in BS 7671 as TN-C-S. However, whilst a PME terminal provides an effective and reliable facility for the majority of installations, under certain supply system fault conditions (external to the installation), a potential can develop between the conductive parts connected to the PME earth terminal and the general mass of Earth.

The potential difference between true Earth and the PME earth terminal is of importance when:

   a. body contact resistance is low (little clothing, damp/wet conditions), and/or
   b. there is relatively good contact with true Earth. 

Contact with Earth is always possible outside a building and, if exposed-conductive-parts and/or extraneous-conductive-parts connected to the PME earth terminal are accessible outside the building, people may be subjected to a voltage difference appearing between these parts and Earth.

Residual current device (RCD) protection

The requirements for RCD protection have been redrafted. The Regulation now contains further requirements for Type B and Type A or Type F RCDs, to take account of DC fault current, as follows (extract below):

“Except where provided by the EV charging equipment, protection against DC fault currents shall be provided by:

(i) an RCD Type B, or

(ii) an RCD Type A or Type F in conjunction with a residual direct current detecting device (RDC-DD) complying with BS IEC 62955 as appropriate to the nature of the residual and superimposed currents and recommendation of the manufacturer of the charging equipment.”

ANNEX A722 (Informative)

Annex A722 has been redrafted. This Annex now includes guidance on the voltage monitoring device described in Regulation 722.411.4.1 (iii). In addition, the Annex now includes an example arrangement of a separated system as described in Regulation 722.413. 

Conclusion

It is important to note that this article gives only a very brief overview of some of the changes in the Amendment to BS 7671:2018. For more information, please refer to BS 7671:2018, Amendment 1:2020.

By: Geoff Cronshaw – IET Wiring Matters – Issue 79

Wiring Matters – Issue 79 – March 2020

Issue 79 (March 2020) of Wiring Matters includes articles on Amendment 1 to BS 7671, the private rented sector, the Electrotechnical Assessment Specification and the return of our Mythbusters column.

Amendment number 1 to BS 7671:2018+A1

Amendment 1 of BS 7671:2018 was published at the beginning of February this year and may be implemented immediately. The amendment concerns Section 722 of BS 7671:2018 (electric vehicle charging installations). In this article, we give a brief overview of some of the main changes to Section 722.

The Electrotechnical Assessment Specification – January 2020 Edition

The Electrotechnical Assessment Specification (EAS) Committee is made up of a wide range of experts who are passionate about the electrotechnical industry. It includes representatives from the competent person scheme providers, certification and registration bodies, industry trade associations, the Ministry of Housing, Communities and Local Government, the Health and Safety Executive, Electrical Safety First and the IET (which also provides administrative support to the committee).

Mythbuster #5 – Will any old terminal block do?

In this issue, James Eade investigates terminals and connectors.

The Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020

Between 17 February and 16 April 2018, the government invited comments on the Electrical Safety Standards Working Group’s decision to make a recommendation to introduce mandatory inspection and testing for private rented properties.

Getting important labelling right leaves a lasting impression

What you leave behind after an installation speaks volumes. While electrical labelling is most importantly about safety, it should also be convenient, professional, time-saving, making your life easier and leave a lasting impression with your customers.

You can read the full story’s here

Code of Practice for Electric Vehicle Charging Equipment Installation (3rd Edition)

This Code of Practice provides a clear overview of EV charging equipment, as well as setting out the considerations needed prior to installation and the necessary physical and electrical installation requirements. It also details what needs to be considered when installing electric vehicle charging equipment in various different locations – such as domestic dwellings, on-street locations, and commercial and industrial premises.

Key changes from the second edition include:

  • Two completely new sections
    • Vehicles as Energy Storage
    • Integration with smart metering and control, automation and monitoring systems
  • A new Annex
  • A complete update to the new requirements in BS 7671:2018
  • Bringing the Code in line with revised regulations and good practice

The risk assessments and checklists have also been reviewed and revised.

This very well established Code of Practice, supported by all the major stakeholders in the industry, is essential reading for anyone involved in the rapid expansion of EV charging points, and those involved in maintenance, extension, modification and periodic verification of electrical installations that incorporate EV charging.

New amendment to BS 7671 (IET Wiring Regulations) Amendment 1

The IET has announced a new amendment to BS 7671:2018 (IET Wiring Regulations 18th Edition). The national Wiring Regulations committee, JPEL/64, agreed the publication of Amendment 1, which will consist of a stand-alone update to Section 722: Electric Vehicle Charging Installations.

The amendment, which is due to publish in early 2020, will be free to view on the IET website, and only form part of a consolidated new Regulations following the next major amendment to BS 7671, expected in 2022.

The amendment follows advances in technology that were not available when BS 7671:2018 published, enabling a more practical solution for the installation of charging points. Functionality built directly into charging equipment uses existing technology, but employed in a new way, allowing charging points to be deployed more widely than ever before.

The updated Section 722 will make installing charging points quicker and easier, and will reduce the cost of installations for both installers and consumers.

The UK government is investing £400 million to accelerate the roll-out of charging infrastructure to help meet its target of at least 50% of new car sales to be ultra-low emission by 2030*.

Mark Coles, Head of Technical Regulations at the IET, is proud of the way that JPEL/64 has been able to respond to the changes in technology. He explains: “JPEL/64 has been able to address a new opportunity for electric vehicle charging equipment that provides a practical, cost-saving solution benefiting industry, consumers and government alike, to help the UK lead the way in the roll-out of infrastructure to support the electric vehicle revolution.

“This update to the IET Wiring Regulations puts the electrical industry at the forefront of driving technological innovation to ensure the installation of practical, safe charging points that are accessible to all.

“By producing Amendment 1 to BS 7671:2018 as a stand-alone, free-to-view document, this updated Section 722 will reach industry much quicker than a full, consolidated amendment would allow, enabling installers to take advantage of BS 7671:2018+A1:2020 as soon as possible.”

Keep an eye on theiet.org/updates to for information on the Draft for Public Comment and publication information.

Proposed timeline

  • 04 September 2019: Amendment 1 approved by JPEL/64
  • October 2019: The Draft for Public Comment for Amendment 1 will be available for 60 days to allow industry to respond to the proposed changes (see theiet.org/updates for details)
  • January 2020: Amendment 1 will publish as a free-to-view document on the IET website and come immediately into effect, eschewing the usual 6-month adjustment period to ensure industry can immediately take advantage of the changes