SOFTWARE
he details of the first amendment to the 17th Edition Wiring Regulations (BS 7671) were published in July. Now, electrical designers and installers have a few months to get to grips with the detail before the amendment comes into force in January 2012.
T KEY ROLE
In parallel, it’s important to recognise the importance of software in the everyday activities of electrical engineers, and how it has come to play a key role in helping the majority of engineers comply with legislation. For instance, when the 15th Edition Wiring Regulations were published in 1980, very few electrical engineers used software at all. And if they did it was mainly for general office applications. Clearly things have changed
enormously, and I would argue there is now an onus on those of us who develop specialist electrical software to play a key role in understanding and complying with new regulations. Consequently, software developers have also had to make sure they understand the changes and that those changes are reflected in that software. This applies particularly to electrical design and certification software packages – and the training and technical support that goes with them, of course. As a result, the software companies that take their responsibilities seriously are fully up to speed and in an ideal position to offer support and advice on the regulations − over and above the software specific aspects. To put the changes to the 17th Edition in perspective, it’s worth noting that the Wiring Regulations are non-statutory, so theoretically you don’t have to comply. However, the standards laid down in BS 7671:2008 and its amendments are regarded by the Health and Safety Executive as likely to achieve conformity with the relevant parts of the statutory Electricity at Work Regulations 1989. So in practice it is essential to comply and failing to do so could lead to prosecution. In order to ensure compliance at all levels it’s important to be aware of changes affecting both design and certification, both of which are outlined below.
NUMBERING STRUCTURE
CENELEC (Committee European Normalisation Electro-technique) is responsible for the European standardisation in the area of electrical engineering. Any changes to these standards that affect Great Britain must be reflected in our regulations. These changes are usually in the form of Harmonised Documents (HD). The requirements of BS 7671 are founded on the requirements of a set of documents identified as HD 60364.
The joint committee for low voltage installations is identified as JPEL/64 (Joint committee for Power Electrical.) The 64 denotes the International Electro- Technical Commissions committee for low voltages designation. In the amended 17th Edition,
regulations that are specific to Great Britain will be identified by a new ‘100’ numbering system. For instance regulation 522.6.5, which deals with
cables installed under floors or above a ceiling etc. will now become Regulation 522.6.100.
This new numbering system is used
throughout the Standard and identifies regulations that only apply to Great Britain. Clearly, then, electrical software will need to reflect these changes. The scope of the regulations has also changed with the introduction of two new special locations, namely medical locations and operating or maintenance gangways. This has also resulted in an increase in the number of definitions.
DESIGN CHANGES
Under the amendments it is now necessary to take account of new cable de-rating factors and minimum cable sizes, as well as new installation methods that have been introduced for certain circumstances.
For example, as well as de-rating cables for third harmonics, higher order harmonics have to be taken into account. A further complication is that there are different de-rating methods for both small and large cables − and there is a requirement for protection of the neutral conductor in circuits with harmonic content. In addition, there are changes to the
requirements for installation of surge protection devices to limit transient over-voltages and divert damaging surge current away from sensitive equipment. As noted above, medical installations will also have special requirements, including stronger measures against electromagnetic disturbance.
PROTECTION FOR SAFETY
Protection for safety is perhaps one of the most important parts of the regulations, as it covers the requirements for protection against electrical shock, thermal effects, overcurrents, voltage disturbances and electromagnetic interference as a result of magnetic disturbances. In terms of protection against electrical shock, two apparently new types of protective device have appeared in Amendment 1. As of March 2010 BS 88-2-2 and BS 88-2-6 devices have been replaced by BS 88-2 devices. BS 1361 has been withdrawn as a British Standard and the protective devices previously known as BS 1361 will now be re-designated as BS 88-3. As a direct result, new protective device ratings (16A and 32A etc.) and maximum earth fault loop impedances have been introduced with protective devices, with ratings such as 15A and 30A being deleted.
In addition, a new section 444 has been introduced. This states that the designer of the installation must be aware of, and consider, the requirements for the reduction of electromagnetic interference on electrical equipment. Section 444 is a very comprehensive section and will play a significant part in the design of all new installations. In recent years there has been a significant increase in the use of electronic equipment that is susceptible to damage by electromagnetic interference. The new regulations, therefore, include detailed information to help designers avoid electromagnetic
disturbances and provide recommendations to reduce the effects of these disturbances where necessary. The whole section is new and
comprehensive and it is the designer’s signature on the certificate which specifically states that the installation is in compliance with the requirements of BS 7671:2008 Amendment 1. There are also changes to Parts 5, 6 and 7 that impact on compliance. For example, in Part 5 the new Section
534 introduces ‘Devices for protection against overvoltage’. These are designed to protect against potentially damaging transient over voltages so it is essential to select the correct surge protective devices. Here, coordination software can play a key role in helping to ensure the appropriate choices are made, especially when it is closely integrated with electrical design software.
CERTIFICATE CHANGES
In part 6, the familiar Periodic Inspection Report is replaced by the Electrical Installation Condition Report. This new report is designed to be
more meaningful to the client, so the classification codes for each recorded observation have been made clearer and more direct. Code 1 is designated when danger is identified as being present, Code 2 is when a potential danger is identified and Code 3 is where an improvement is recommended. Code 1 requires immediate action to be taken; in other words the reason for the danger being present should be made safe on discovery. Where this is not practical the owner, duty holder or the responsible
SPECIAL FEATURE
person should be given written notification of the identified problem as a matter of urgency. An additional column is provided for comments where further investigation may be required. Different types of inspection schedule
are now recommended to be produced dependent upon the type of installation, such as: • Condition report inspection schedule for domestic and similar premises.
• Recommended inspections for multiple distribution board installation.
In Part 7 there are two new sections – Section 710 for medical locations and Section 729 for operating or maintenance gangways. In the case of medical locations the nature of the risk to the patient or medical staff within the location has to be decided and the installation safety requirements must be appropriate. The level of risk is defined in Groups - Group 0, Group 1 and Group 2. Group 2 is where a loss of supply could result in a danger to life. Disconnection times for areas defined as Group 1 or 2 have been reduced to 0.3 seconds on TN systems and 0.05s on TT systems.
THE RIGHT SOFTWARE
Earlier in this article I noted that software plays an important role in assisting with compliance and clearly electrical design and coordination software should highlight any potential problems in the early design stages and helping to ensure compliance.
This means that design and
coordination software written before the changes in 17th Edition Amendment
To ensure compliance at all levels it’s important to be aware of changes affecting both design and certification.
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