as well as measures for minimising electromagnetic disturbances.
Section 534 – Devices for protection from overvoltage Why has this new section been added? This is a new section that has been implemented by CENELEC in HD 60364-5-53. A surge protective device (SPD) is a device that is intended to limit transient overvoltages and divert damaging surge current away from sensitive equipment. Equipment is now more precise, with little tolerance on the components, and hence, less robust than it ever was, making SPDs more important than ever. SPDs must have the necessary capability to deal with the current levels and durations involved in the surges to be expected at their point of installation.
What guidance do the Wiring Regulations give around SPDs? Section 534 gives detailed requirements on the selection of SPDs, to ensure that the correct type of SPD is installed at the correct position within an installation. The section also stipulates a number of requirements for the connection of SPDs, depending on the type of supply and earthing arrangements, and for installation in circuits with RCDs. The section also sets out requirements for the connection of SPDs – one example being the requirements for the critical length of connecting conductors. To gain maximum protection, it is stipulated that the supply connecting conductors to the SPD shall be kept as short as possible, to minimise additive inductive voltage drops across conductors.
Section 710 – Medical Locations Why has this section been added? Electrical equipment based in medical locations presents particular risks to patients. Section 710 therefore sets out stringent measures that are necessary to ensure the safety of patients likely to be subjected to the application of electrical medical equipment.
What are the risks specific to medical locations? The human body’s natural protection against electric shock is considerably reduced when certain clinical procedures are being performed on it. Surgical or clinical invasive procedures bypass the skin’s resistance when applied parts are being used inside the body.
What measures does the new section introduce? One of the main measures introduced by Section 710 is in the division of medical rooms into three different groups, depending upon the type of treatment they deliver and the potential hazards of electrical shock to patients. The three different groups are: Group 0 – Medical locations where no applied parts are intended to be used, and where discontinuity (failure) of the supply cannot cause danger to life. Group 1 – Medical locations where discontinuity of the
66 ECA Today November 2011
New codes and definitions have been developed to improve clarity – if it’s recorded, it’s an issue that should be dealt with
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Where can I get further information? If you have any questions about the IET Wiring Regulations, 17th Edition, BS 7671:2008 incorporating Amendment No 1: 2011, you can call the free technical helpline to speak to an expert at the IET on 01438 765599 or email
technical@theiet.org You can purchase the new Wiring Regulations here:
www.theiet.org/amend1 As the authority on the requirements for electrical installations, the IET also offers a series of guidance notes and training courses, which you can find out more about here:
www.theiet.org/electrical You can also get more information from the ECA’s technical department by calling 020 313 4825 or emailing
giuliano.digilio@eca.co.uk.
electrical supply does not represent a threat to the safety of the patient, and applied parts are intended to be used externally. Group 2 – Medical locations where applied parts are intended to be used in applications such as intracardiac procedures, vital treatments and surgical operations where discontinuity (failure) of the supply can cause danger to life.
Are there any other measures to protect against electrical hazards? To protect patients from possible electrical hazards, Section 710 sets out other additional protective measures to be adhered to. These include: particular requirements for protection against electric shock; medical IT systems – requirements concerning supplementary equipotential bonding; additional requirements for the selection and erection of electrical equipment, including switchgear and controlgear; and safety services, including the sources and detailed requirements for safety lighting.
Section 729 – Operating and maintenance gangways Why has section 729 been introduced? Section 729 is intended to ensure a safe working environment for skilled or instructed persons working in areas such as switchrooms and controlgear assemblies where, historically, not much space has been allocated. The section has been incorporated into BS 7671:2008(2011) in order to align with the European Harmonised Document. Regulation 15 of the Electricity at Work Regulations 1989 requires that adequate working space, means of access and lighting shall be provided at all electrical equipment on which, or near which, work is being done.
What does the section cover? The section sets out minimum requirements for the provision of adequate working space, means of operational and emergency access and evacuation at, or near, electrical equipment which is being worked on. The amended regulations outline new requirements for the width of gangways and access areas, which are to be adequate for work, operational access, emergency access and egress and for the movement of equipment.
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