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The maximum earth loop Impedance figures can be found on the attached pdf files.
63A to 250A
The MCCB's used for ratings of 63A to 250A are identical to the NSX with thermal magnetic trip units.
400A & 630A
The MCCB's used for ratings of 400A & 630A are identical to the NSX with Micrologic 2.3 trip units.
The Figures for Earth Loop Impedance quoted are for the the UK based on the British Standard BS 7671:2008+A3:2015.
A revision of the British Standard BS 7671:2008+A3:2015 introduces an additional factor in to the calculation of Earth Loop Impedance (Zs). This factor takes account of the ‘minimum voltage factor’
For a TN system, section 411.4.5 of BS7671:2008+A3:2015 defines the maximum earth fault loop impedance based on the following condition being met:
Zs - is the maximum earth fault loop impedance.
Uo is the minimum voltage factor to take account of voltage variations depending on time and place, changing of transformer taps and other considerations.e.g. For a 400V 3 phase system this is 230V).
la - Ia is the current causing operation of the protective device within the specified time. E.g. For motor starters this is 0.4 seconds.
Cmin is the minimum voltage factor to take account of voltage variations depending on time and place, changing of transformer taps and other considerations.
NOTE : For a low voltage supply given in accordance with ESQCR, Cmin is given the value 0.95.