Tag Archives: IET

Wiring Matters – Issue 87 – September 2021

It’s that time again, here is what you can find in Issue 87 (September 2021) of the IET’s Wiring Matters magazine.

Evaluation and metrics

The design framework of IEC 60364-8-1 provides guidance on a more energy-efficient electrical installation through careful placement of electrical supplies, considered infrastructure design, controls and energy management. All of this is designed to minimise energy loss in the distribution of electricity and reduce energy consumption at the point of use in the electrical installation, whilst still maintaining a suitable and comfortable environment for the end-users.

Electrical Safety Standards in the Private Rented Sector

The IET’s Technical Helpline continues to be inundated with queries relating to the practicalities of implementing the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020 (ESSPRS). These place legal requirements on landlords to ensure that every electrical installation in a privately rented residential premise is inspected and tested at intervals of no more than 5 years, by an electrically qualified and competent person.

Myth Busters #7 – Out with the old, in with the new?

The introduction of the 18th Edition of the IET Wiring Regulations (BS 7671:2018) saw a new regulation buried in Section 536 Co-ordination of electrical equipment for protection, isolation, switching and control.

Back to the Forum – Current-carrying capacity of cables buried in the ground

A question that arises periodically on the IET Engineering Communities forum concerns the current-carrying capacity of cables buried in the ground, in particular, the data used to select the appropriate cross-sectional area (CSA) of live conductors.

TT earthing considerations

TT earthing facilities are installed when the distributor does not provide a TN earthing system or when circumstances dictate that a TN earthing system cannot be used. A look at the considerations and what you need to know.

You can take a look at the full edition via the link below –

https://electrical.theiet.org/wiring-matters/years/2021/87-september-2021/

How to spot the fake IET books

According to the IET website they are aware of several counterfeit versions of its books in circulation.

BS 7671, the On-Site Guide, Guidance Note 3 and the Code of Practice for In-Service Inspection and Testing of Electrical Equipment are all known to have counterfeit versions in circulation, with varying numbers of mistakes in each.

Adhering to text in counterfeit electrical books can lead to non-compliant installations, which could be potentially very dangerous. BS 7671 exists to ensure that electrical installations are safe and to reduce the risk of fire or electric shock. Using corrupted information undermines the safety of your work.

To help combat this issue, current and future copies of BS 7671, the On-Site Guide and Guidance Note 3 all contain a hologram. This currently contains the IET logo in two sizes and the word ‘GENUINE’ as well as a number of additional features.

Although this can help you to identify a fake, it is not foolproof, as counterfeiters can produce similar versions of the hologram. The only way to be certain of buying a genuine copy of our books is to buy directly from the IET, or from one of the approved suppliers (Amazon been one example)

The IET is a charity, and the dissemination of information is part of our charitable remit. Any surplus from the sale of the books is re-invested into producing guidance for industry, through our publications programme and Wiring Matters magazine. The proceeds from the sale of fake books do not support the industry in any way and harm the IET’s ability to fulfil its remit.

If you think you might have mistakenly purchased a fake copy of an IET book, please get in touch with the IET with as much information as possible about the book and where you bought it.

Unfortunately, the IET cannot reimburse purchases bought from suppliers of counterfeit books, nor assist with the resolution of disputes, but they are working to shut down any counterfeiters that they find and take legal action against them to reduce the risk to the industry.

Links to the books listed above (via Amazon)

Amazon – Code of Practice for In-service Inspection and Testing of Electrical Equipment (Electrical Regulations) – https://amzn.to/3x64f1t

Amazon – On-Site Guide (BS 7671:2018) (Electrical Regulations) – https://amzn.to/3jtKNaP

Amazon – Requirements for Electrical Installations, IET Wiring Regulations, Eighteenth Edition, BS 7671:2018 (Electrical Regulations) – https://amzn.to/3x6PeMC

Amazon – Guidance Note 3: Inspection & Testing (Electrical Regulations) – https://amzn.to/3qwlkyU

What’s in Wiring Matters Issue 83 [November 2020]

Let’s take a look at what you can find in Issue 83 of Wiring Matters (November 2020)

The impact of Amendment 2 of the 18th edition (BS 7671:2018+A2:2022)

In this article, we look at the impact that some of the proposed changes in the draft for public comment (DPC) will have on electrical installations. We focus on Chapter 42, Chapter 44 and the new Chapter 82.

COVID-19 and how it has changed the way we work

Steven Devine talks about some of the effects that COVID-19 has had on the industry.

Current-carrying capacity of cables installed in concrete cable troughs

A discussion regarding the maximum number of cables that can be installed in a pre-formed concrete cable trough?

How I became a Chartered Engineer

Michael Peace shares his experience of becoming a Chartered Engineer.

Section 514 identification and notices in the Amendment No. 2 Draft for Public Comment

The draft for public comment (DPC) of Amendment No. 2 to BS 7671:2018 contains proposed changes to Section 514 Identification and notices. This article provides an overview of those proposed changes, and the reasons behind them.

Sponsored: Surge Protection – what you need to know

Surge protection devices (SPD) are a requirement under the 18th Edition of the Wiring Regulations and essential in protecting equipment from damage. Here, Dominick Sandford, Director and Head of Merchandising & Marketing at ElectricalDirect explains the requirements.

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