Please find attached the maximum earth loop impedance Zs values for SFAL & SFHL MCCBs
In order to comply with BS7671 Amendment 3: 2015 the figures in the chart should be multiplied by Cmin .95
In order to comply with BS7671 Amendment 3: 2015 the figures in the chart should be multiplied by Cmin .95
Zs - is the maximum earth fault loop impedance.
Uo - is the nominal voltage to earth (for a 400V 3 phase system this is 230V).
la - is the current causing the operation of the circuit breaker in less than 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. (Cmin= 0.95)
in order to comply with BS7671 Amendment 3: 2015 the figure in the table should be multiplied by Cmin .95
Released for:Schneider Electric UK
