When assessed by specified tests, these cables produce lower levels of smoke and corrosive products under exposure to fire, compared with corresponding cables conforming to BS 4553-1 and BS 4553-2.

This British Standard specifies requirements for construction and describes methods of test for XLPE-insulated single-phase split concentric cables for operation on an earthed neutral system at nominal voltages up to and including 1 000 V between phases and 600 V to earth and which, when assessed by the specified tests, produce lower levels of smoke and corrosive products under exposure to fire, compared with corresponding cables conforming to BS 4553-1 and BS 4553-2. In this standard, the level of corrosive (and acid) gases is determined by measurement of hydrochloric acid (HCl) in accordance with BS EN 50267-2-1 . The cables specified in this part of BS 4553 have a central phase conductor insulated with XLPE and a concentric layer comprising bare copper wires (earth continuity conductor) and copper wires covered with extruded polymer (neutral conductor). The cables are intended for use in fixed installations in industrial areas, buildings and similar applications. They are suitable for use in situations where the combination of ambient temperature and temperature rise due to loading current results in a conductor temperature not exceeding 90 °C and for a maximum short-circuit conductor temperature of 250 °C. NOTE 1 Limitation on the temperature of the cables may be imposed in situations where they may be touched. NOTE 2 Due to the relatively high conductor temperature, there is a risk of drying out the surrounding soil causing an increase in thermal resistivity which in turn would lead to the cable temperature rising to a higher value than anticipated. For cable laid directly in the ground, a suitable de-rating factor should be applied or a lower maximum sustained conductor operating temperature should be assumed to take into account the possible effects of soil drying out. NOTE 3 In installations which include cable joints and terminations, the performance of these accessories should be taken into account in deciding the maximum operating temperature of the cable. Guidance concerning selection, installation and usage is given in Annex A, Annex B and Annex J respectively.