Prysmian CableApp

CALCULATIONS


The Cable App uses the correction factors defined in the tables of Appendix 4 of BS7671. This allows the user to tailor a circuit rating for their given prescribed installation. These correction factors cover the following parameters: ambient temperature (air, and ground where appropriate); soil resistivity; depth; proximity of multiple circuits for ladder, tray, direct in ground and in ducts in the ground.


Rating Factor Type Correction Table Reference in BS7671 Applicable Reference Method & Ratings Table(s)
Rating factors (Ca) for ambient air temperatures other than 30°CAmbient Table 4B1 Ref Method C, E & F
Tables: All
Rating factors (Ca) for ambient ground temperatures other than 20°CAmbient Table 4B2 Ref Method D,
Table 4E4A
Rating factors (Cs) for cable buried direct in the ground or in an underground conduit system for soil resistivitites (for Ref Method D) Table 4B3 Ref Method D,
Table 4E4A
Rating Factors (Cd) for depths of laying other than 0.7m for direct buried cables and cables In buried ducts Table 4B4 Ref Method D,
Table 4E4A
Rating factors for one circuit or one multicore cable or for a group of circuits of multicore cables, to be used with current-carrying capacities of Tables 4D1A to 4J4A Table 4C1 Ref Method A, B, C, E or F (appropriately)
Tables 4D1A, 4D2A, 4D5; 4E1A, 4E3A & 4E4A
Rating factors for more than one circuit, cables buried directly in the ground (for Ref Method D, Table 4E4A) Table 4C2 Ref Method D,
Table 4E4A
Rating factors for more than one circuit, cables in ducts buried directly in the ground (for Ref Method D, Table 4E4A) Table 4C3 Ref Method D,
Table 4E4A
Rating Factors for groups of more than one multicore cable, to be applied to reference current-carrying capacities for multicore cables in free air (Ref Method E, for Tables 4D2A, 4D5 & 4E4A) Table 4C4 Ref Method E,
Tables 4D2A, 4D5 & 4E4
Rating Factors for groups of more than one single-core cable, to be applied to reference current-carrying capacities of single-core cables in free air (Ref Method F, for Tables 4D1A, 4E1A & 4E3A) Table 4C5 Ref Method F,
Tables 4D1A, 4E1A & 4E3A


The base conditions for the published current ratings in BS7671 are as follows:

Base Cable Installation Conditions for Cable Ratings


Parameter Condition
Ambient Air temperature 30°C
Ambient Ground temperature 20°C
Base installation depth (for cables installed in the ground) 0.7m
Base soil resistivity (for cables installed in the ground) 2.5 K.m/W


This Cable App executes voltage drop calculations using the pre-defined values for voltage drop, published in Appendix 4 of BS7671 for the appropriate Cable Type Table.


Cable Type Current Rating Table Reference Volt Drop Table Reference
Single-core 70°C thermoplastic insulated cables, non-armoured, with or without sheath 4D1A 4D1B
Multicore 70°C thermoplastic insulated and thermoplastic sheathed cables, non-armoured 4D2A 4D2B
70°C thermoplastic insulated and sheath flat cable with protective conductor 4D5 4D5
Single-core 90°C thermoplastic insulated cables, non-armoured, with or without sheath 4E1A 4E1B
Single-core armoured 90°C thermosetting insulated cables (non-magnetic armour) 4E3A 4E4B
Multi-core armoured 90°C thermosetting insulated cables 4E4A 4E4B






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