CENELEC, the European Committee for Electrotechnical Standardization, publishes two kinds of standards, the European Standard (EN) and the Harmonised Document (HD). The HD and EN differ slightly.
The EN must be literally transposed as it is, word for word, in all CENELEC member countries, where as, for the HD it is only the technical content that must be transposed into national standards. BS 7671, Requirements for Electrical Installations, takes account of the technical intent of CENELEC Harmonization Documents.
Currently there are three main areas of development which it is expected will be included within a future amendment to BS 7671:2008; these are:
- Section 710 - Medical locations
- Section 444 - Measures against Electromagnetic Influences, and
- Section 534 - Devices for Protection against Overvoltage (Surge Protection Devices
Section 710 applies to electrical installations in medical locations so as to ensure safety of patients and medical staff. These requirements, in the main, refer to hospitals, private
clinics, medical and dental practices, healthcare centres and dedicated medical rooms
in the work place. This Section also applies to electrical installations in locations designed for medical research. The requirements of this Section do not apply to medical electrical equipment.
Section 444 deals with measures against electromagnetic disturbances. Electromagnetic Interference (EMI) may disturb or damage information technology equipment/systems as well as equipment with electronic components or circuits. Currents due to lightning, switching operations, shortcircuits and other electromagnetic phenomena may cause overvoltages and electromagnetic interference. Section 444 provides basic requirements and recommendations to enable the avoidance and reduction of electromagnetic disturbances.
Section 534 deals with the installation of surge protective devices (SPD). The requirements of Section 534 are for the selection and erection of SPDs for electrical
installations of buildings in order to limit transient overvoltages of atmospheric origin transmitted via the supply distribution system and against switching overvoltages. The requirements are also intended to protect against transient overvoltages caused by direct lightning strikes or lightning strikes in the vicinity of buildings, protected by a lightning protection system.
The requirements do not take into account surge protective components, which may be incorporated in the appliances connected to the installation...
To view the full article for the IET's Wiring Matters Spring 2009, click on the attcahment below.