Protected power circuits

Where it is critical for electrical circuits to be able to continue to function during a fire, protected circuits are needed. The potential for damage to cables forming protected circuits should be limited by the use of sufficiently robust cables, careful selection of cable routes and/or by the provision of physical protection in areas where cables may be susceptable to damage. Methods of cable support should generally be non-combustible and such that circuit integrity will not be reduced below that afforded by the cable. A protected circuit for operation of equipment in the event of a fire should consist of cables meeting at least the requirements for PH 30 classification when tested in accordance with BS EN 50200 (incorporating Appendix E), or equivalent standard. It should follow a route selected to pass only through parts of the building in which the fire risk is negligible and should be separate from any circuit provided for another purpose. In large or complex buildings there may be fire protection systems that need to operate for an extended period during a fire. Further guidance on the selection of cables for such systems is given in BS 5839-1, BS 5266-1 and BS 7346-6.