Ipf = U0 / Z. Use Ze for the origin and Zs for the far end. A lower impedance gives a higher fault current.
This uses the nominal voltage you enter. It does not apply the 0.95 factor used for maximum Zs, and a cold measured loop is not the same as the impedance during a hot fault. Record the instrument reading on the certificate.
These tools are quick guides for a ballpark figure. They are not certified design or test software, and a result on this page is not a design, a certificate, or a substitute for the current edition of BS 7671. Check the working and cross-reference it before you apply it to a real installation. Thanet Electrical Ltd does not accept liability for loss or cost arising from reliance on these figures, except where the law does not allow that liability to be excluded, including death or personal injury caused by negligence.
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