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.

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

Line Conductor:
Material Copper Copper (tin soldered) Aluminium	Insulation 70 deg.Thermoplastic 90 deg.Thermoplastic 60 deg.Thermosetting 90 deg.Thermosetting Mineral Insulated (thermoplastic sheath) Mineral Insulated (unsheathed)	Initial Temperture: 70 oC Final Temerature: 160 oC

Protective Conductor:

insulated conductor not incorporated in a cable and not bunched with cables separate bare protective conductor in contact with cable but not bunched with cables conductor incorporated in cable or bunched with cables sheath or armour of cable as protective conductor steel conduit, ducting and trunking as protective conductor bare conductor, no temperature risk to neighbouring material
Material Copper Aluminium Steel	Insulation 70 deg.C Thermoplastic 90 deg.C Thermoplastic 90 deg.C Thermosetting	Initial Temperture: 30 oC Final Temerature: 160 oC

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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

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