Protective Conductor Cross Sectional Area
(BS 7671/ IEE Wiring Regulations 17th Edition)

Use 543.1.1 or 543.1.4 for size (543.1.3 is manatory if short circuit considered in main cable size). Mimium size 2.5 mm2 if mechanically protected and 4 mm2 if not. Use most onerous fault current/operating time and largest line conductor csa.


Fault Current: A Disconnection time: S
Line Conductor: mm2

Line Conductor:
Material
Insulation
Initial Temperture: 70 oC
Final Temerature: 160 oC
 
Protective Conductor:

Material
Insulation
Initial Temperture: 30 oC
Final Temerature: 160 oC



Regulation 543.1.3 (adiabatic equation, disconnection time not exceeding 5 s )
Mimimum Protective Conductor Size: 134 mm2

Regulation 543.1.4 (relation to phase conductor, disconnection time not exceeding 5 s)
Protective conductor same material as associated line conductor
Minimum Protective Conductor Size: 16 mm2

Regulation 543.1.4 (relation to phase conductor, disconnection time not exceeding 5 s)
Protective conductor not same material as associated line conductor
Mimimum Protective Conductor Size:13 mm2

*select next larger standard cross-sectional area

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Resources

Cable Sizing

To select or size power cables to BS 7671:2008 (IEE Wiring Regulations Seventeenth Edition) and IEC 60364:2001, please use our:
 - Cable Sizing Calculator









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