Before you slate it try the formula not gn3 part try the first formula for any type B,C,D 60898 put in the parts of the formula & check it gives you the answer

Maximum permitted Zs is calculated using the formula in the regulations (the formula you have demonstrated) and the characteristics of the OCPD.
 
you both are talking bollox, the nominal voltage hasnt changed i have bs7671:2008 inc amendment 3

2b61406a3c30758752582f4df5e895d3.jpg



check the formulae again, you should use a measured value in the formulae or your wasting your time

appendix 3 p317

for those with digital version this is the title of the section "TIME/CURRENT CHARACTERISTICS OF OVERCURRENT PROTECTIVE DEVICES AND RCDs"

The book says to use the 'nominal' voltage; this does not mean a measured value. nominal - definition of nominal in English from the Oxford dictionary - (Of a role or status) existing in name only; in this case the 'given' or named value which is 230 V.
 

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