PROPOSED Changes to BS7671 – 18th Edition

PROPOSED Changes to BS7671 – 18th EditionExternal presentation

Introduction

Changes to BS7671

June 18, 2018 Slide 2

BS 7671:2018 Requirements for Electrical Installations will be issued on 2nd July 2018 and is intended to come into effect on 1st January 2019.

Installations designed after January 1st 2019 will have to comply with BS 7671:2018.

The Regulations apply to the design, erection and verification of electrical installations, also additions and alterations to existing installations.

This presentation is not an exhaustive list of the changes but does highlight some of them and the solutions offered by ABB to assist with designing new or altering existing installations.

History

Changes to BS7671


First issue of wiring regulations issued in 1882

History

Changes to BS7671


1991

1994

1997

2001

20112015

2004

2008

2018

Purpose

Changes to BS7671


• They are defined as a Code of Practice, even though they are called ‘Regulations’ and are deemed a non-statutory standard published by the BSi, they are used in the UK and across the world.

• The standard relates to design, selection and erection; and inspection and testing of electrical systems regardless of whether the system is permanent or temporary.

• Even though they are non-statutory, the have been referred to in extensive HSE/HSC guidance notes and the Electricity Safety, Quality and Continuity Regulations 2002 used by the electricity supply industry.

• You can be prosecuted for failure to comply under the Health and safety at work act section 17! It is universally accepted that compliance with the document and its ‘requirements’ will enable you to comply with the Electricity at Work Regulations 1989.

Part 1: Scope, Object and Fundamental Principles

Part 1: Scope, Object and Fundamental Principles


133.1.1 Every item of equipment shall comply with the appropriate British or Harmonized Standard. In the absence of such a standard, reference shall be made to the appropriate International (IEC) standard or the appropriate standard of another country.

133.1.3 Where equipment to be used is not in accordance with Regulation 133.1.1 or is used outside the scope of its standard, the designer or other person responsible for specifying the installation shall confirm that the equipment provides at least the same degree of safety as that afforded by compliance with the Regulations. Such use is to be noted on the Electrical Installation Certificate specified in Part 6

Also referred to as a “Departure”

Part 2: Definitions

Part 2: Definitions


Departure. Deliberate decision to not comply fully with the requirements of this standard, for which thedesigner must declare that the resultant degree of safety is not less than that achievable by full compliance.


• Combined Short Circuit Current Capability: Maximum short circuit current which can be handled by two short circuit protective devices in series.

i.e. The level stated by a manufacturer as the back up protected short circuit capability

• Selectivity: Co-ordination of the operating characteristics' of two or more protective devices such that, on the incidence of overcurrents’ or residual currents within stated limits, the device intended to operate within these limits does so, while the other(s) does (do) not.

Previously stated as “Discrimination”

Part 2: Definitions

Part 4: Protection for safety

Chapter 42 Protection against thermal effects

421 Protection against fire caused by electrical equipment



421.1.7: Arc fault detection devices conforming to BS EN 62606 may be used to provide additional protection against fire caused by arc faults in AC final circuits

IEC60364 suggests that locations to consider for additional protection would be• locations built with flammable material• locations that contain flammable material• rooms that have sleeping accommodation• locations at risk of fire due to processed or stored materials, combustible construction materials, fire

propagating structures• locations that contain irreplaceable goods




Protection against:• Overcurrent (short circuits,

overload)


overload)• Earth fault currents• Earth arc fault


overload)• Serial and parallel arc faults• Earth arc faults


overload)• Earth fault currents• Serial and parallel and

Earth arc faults







Chapter 44 Protection against voltage disturbances and electromagnetic disturbances

443 Protection against transient overvoltage of atmospheric origin or due to switching



Protection against overvoltage shall be provided where the consequence caused by overvoltage results in:

• serious injury to, or loss of human life, (e.g. hospitals, care homes)• interruption of public services and/or damage to cultural heritage, (e.g. power stations, data centres,

heritage status e.g. castles, museums)• interruption of commercial or industrial activity (e.g. banks, hotels, supermarkets, industrial plants, farms)• affecting a large number of co-located individuals (e.g. offices, universities, schools, residential tower blocks)

Outside of the above, 443 uses a simplified risk assessment to determine a Calculated Risk Level CRL to assess the need for overvoltage protection

Protection for SAFETY – Protection of equipment is in 534

Chapter 46 Devices for isolation and switching




461.2 In TN-C systems and in the TN-C part of the TN-C-S systems, the PEN conductor shall not be isolated or switched

In TN-C-S and TN-S systems, isolation or switching of the neutral conductor is not required if protectiveequipotential bonding is installed and either:• the neutral conductor is reliably connected to earth by a low resistance to meet the disconnection times of

the protective devices according to the requirements of Chapter 41 or • the distribution network operator (DNO) declares that either the PEN or the N conductor of the supply is

reliably connected to earth by a low resistance to meet the disconnection times of the protective devices according to the requirements in Chapter 41




462.2 Every circuit shall be provided with isolation means for all live conductors, except as detailed inRegulation 461.2.

463.1.4 Functional switching devices ensuring the change-over of supply from alternative sources shallswitch off all live conductors and shall not be capable of putting the sources in parallel, unless the installationis specifically designed for this condition.

462.4 Where residual electrical energy is potentially present, suitable means shall be provided for its discharge. Where relevant, a warning label indicating the discharge time required before the enclosure can be safely opened, shall be provided.

Part 5 Selection and erection of equipment

Chapter 53 Protection, isolation, switching, control and monitoring

531 Devices for protection against electric shock by automatic disconnection of supply

Part 5: Selection and erection of equipment


531.3.2 Unwanted trippingResidual current protective devices shall be so selected and erected to limit the risk of unwanted tripping.The following shall be considered:

• subdivision of circuits with individual associated RCDs. RCDs shall be selected and the electrical circuits shall be subdivided in such a way that any earth-leakage current likely to occur during normal operation of the connected load, will not cause unwanted tripping of the device

• See also See also Section 314. In order to avoid unwanted tripping by protective conductor currents and/or earth leakage currents the accumulation of such currents downstream of the RCD shall be not more than 30% of the rated residual operating current.

532 Devices for protection against the risk of fire



532.5 Internal arc fault protection in a switchgear and controlgear assemblyWhere required for special applications, internal arc fault protection (e.g. optical detection systems)detecting a fault arc together with a protection system can be selected in order to extinguish the arc.

Alternatively, an assembly with arc ignition protected zone(s) can be selected to minimise the risk of anarcing fault. (Arcing class I in accordance with PD IEC/TR 61641.).

NOTE: Internal arc fault protection is typically associated with a switchboard used in special applications.


Changes to BS7671


12 kV, 40 kA

0.2 sec Steel fire

0.15 sec Copper fire

0.1 sec Cable fire




The most common reasons for arc flash accidents

Human errors

Mechanical faults

Bad connections

Pollution

Animals

When do arc flash accidents occur?

25 % without operator

10% with operator in front of a closed door

65 % with operator working in the switchgear




Flying debris:• Copper expands by a factor of 67,000:1 when turning from solid to

vapor • Molten metal and shrapnel travel as fast as 1600km/hourPressure:• The sound of an arc blast can easily surpass 160dB • Volume of air in the compartment can increase more than 50x• Arc blasts can and have caused death at distances greater than 3mExtreme heat:• Temperature of arc an blast can reach over 20,000°C (surface of the

sun is roughly 5500°C)







1. Arc is detected by the fiber optic sensor

2. Signal is sent to the TVOC-2 arc monitor

3. TVOC-2 arc monitor sends a trip signal to shunt trip of circuit breaker

4. All this occurs in under 1ms







Energy supplied to arc disconnected after 40ms







532.6 Arc fault detection devices (AFDD)Where specified, AFDD shall be installed:- at the origin of the final circuits to be protected, and- in AC single phase circuits not exceeding 230V.

The AFDD shall comply with BS EN 62606. Coordination of AFDDs with overcurrent protective devices, if necessary, shall be in accordance with the manufacturer's instructions.

534 Devices for Protection against Overvoltage



Section 534 focuses on surge protection for mains power but any metallic electrical line (data/telecom) is a path for transients – 534 recommends protection for these services




Superior SPDs tested to meet requirements of both lightning current and overvoltage SPDs:• Handle high lightning currents typically seen at service entrance

Mains combined Type SPDs e.g. 1+2, 2+3, 1+2+3 combined Type are more economic:• Less units required than individual Type SPDs• Lower (therefore better) voltage protection levels UP (let-through voltage) for a given test surge• Allow continuous operation of electronic equipment (full mode protection – protect in both common and

differential modes)• UP of <1600V for Type 1+2 and <600V for Type 2+3 SPDs (tested to IEC61643, 230/400V system)




Appendix 16:“The most important aspect in selecting an SPD is its limiting voltage performance (protection level Up) during the expected surge event, and not the energy withstand (eg Iimp which it can handle).”

UpUp

536 Coordination of electrical equipment for protection, isolation, switching and control



536.3 For selecting electrical devices as covered by the following regulations, the mutual interaction between those devices shall be considered so that they do not adversely affect the safety of the installation.

536 Coordination of electrical equipment for protection, isolation, switching and control



of today and tomorrowof today and tomorrow

Documents

PROPOSED Changes to BS7671 – 18th Edition