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klik.system | Specification guide to prefabricated wiring systems
15
“ The calculations, should take into
account minimum and maximum fault
currents ”.
Earth fault loop impedance for protection
against electric shock (fault protection)
When Steel Wire Armour is used e.g. home run cable, it is
important that a suitable multiplier is applied to its tabulated
value of resistance at 20°C. This accounts for the magnetic
effect of the steel armour.
Again, the influence of connector contact resistance must be
accounted for.
Protective conductor cross-sectional area for
protection against earth fault current
Where the assumptions of Regulation 435.1 cannot be made,
the cross-sectional area of the circuit protective conductors
have to meet the adiabatic equation by selection or
calculation.
The calculations, should take into account minimum and
maximum fault currents, so as to ensure the highest energy
let-through (I
2
t) is taken into account. This is essential, as I
2
t
is proportional to the thermal energy let through by the
protective device under fault conditions.