BS EN 50306-4:2020 - Page 2

Railway applications. Railway rolling stock cables having special fire performance. Thin wall. Multicore and multipair screened or not screened sheathed cables | Status: Current

1 Scope This document specifies requirements for, and constructions and dimensions of, multicore and multipair cables rated voltage U0/U: 300/500 V, of the following types:

• — unscreened, sheathed for either exposed or protected wiring (0,5 mm2 to 2,5 mm2, number of cores from 2 to 48);
• — screened, sheathed for either exposed or protected wiring (0,5 mm2 to 2,5 mm2, number of cores from 2 to 8);
• — unscreened, sheathed for either exposed or protected wiring (0,5 mm2 to 1,5 mm2, number of screened pairs of cores from 2 to 7).
• — screened, sheathed for either exposed or protected wiring (0,5 mm2 to 1,5 mm2, number of unscreened pairs of cores from 2 to 7).

All cables have stranded tinned copper conductors, halogen-free, thin wall thickness insulation and standard wall thickness sheath. Cable types are specified for use in exposed situations (Class E), and for protected situations (Class P). They are for use in railway rolling stock as fixed wiring or wiring where limited flexing in operation is encountered. These cables are rated for occasional thermal stresses causing ageing equivalent to continuous operational life at a temperature of 90 °C. For standard cables this is determined by the acceptance test defined in EN 50305, using accelerated long-term (5 000 h) thermal ageing indicating a 110 °C/20 000 h temperature index. If the customer were to require lifetime predictions this would be demonstrated based on the temperature index of the product as supplied by the manufacturer. The maximum temperature for short circuit conditions is 160 °C based on duration of 5 s. Under fire conditions the cables exhibit special performance characteristics in respect of maximum permissible flame propagation (flame spread) and maximum permissible emission of smoke and toxic gases. These requirements are specified to permit the cables to satisfy Hazard Level 3 of EN 45545‑1 and EN 45545‑2. EN 50306‑4:2020 is expected to be used in conjunction with EN 50306‑1:2020, General requirements, EN 50306‑2:2020, Single core cables, and EN 50306‑3:2020, Single core and multicore cables.