Andy is correct, whilst BS 88-3 is seen as the replacement standard for BS 1361, the time-current characteristics do differ and it's not 100 % "like for like" - as Tables B4 and B5 in the On-Site Guide will demonstrate. There may be certain circuits out there that, when replacing the BS 1361 with a BS 88-3, no longer meet the maximum measured earth fault loop impedance requirement.


The 80 A time-current characteristic [range] is on page 28 of BS 1361:1971, which is still available from BSI. Standards are very accessible if you know where to look, e.g.:

Many local library services have the ability to view standards on-line (but not download/print), for example this is available if you are resident in Lancashire County Council area : http://www3.lancashire.gov.uk/onrl/BSI/BSiLogon.asp


Or similarly, if you visit Savoy Place, there is a facility via the IET's Library Services, see: https://www.theiet.org/publishing/library-archives/the-virtual-library/british-standards-online/

If anyone is using the standard, and has never done so before, worth noting that the curve that used to be presented in BS 7671 was the right-most (worst-case, higher current for time) of the two curves shown.