Ok, a friend of friend is importing a piece of electrical equipment from the UK and he says that in the guarantee it should be to be installed to British standards to keep the guarentee good. He phoned up and got more detail and then came to me(Its plastic injection molding machine i think).
Cables sizing not a problem same way of calculating here as it is in the UK.(current carrying capacity, grouping factors, ambient temperature factors, volt drop etc etc)
In the UK Final circuits must be designed to disconnect withing 0.4 seconds and sub mains 5 seconds (taking into consideration the impedance of the external earth fault loop(Ze) plus the impedance of the line conductor(R2) plus the CPC (R1) Zs=Ze + R1 +R2. Then its just 230/Zs to give you the expected fault current at that point to flow under fault conditions and we just compare that to the tripping characteristics of of the protective device being used to ensure the device operates within 0.4 seconds) .
I believe that in SA that minimum CPC size is calculated on
2 * Icb
(25 Volt being maximum touch voltage before protective device operation).
I can't find anywhere in SANS 10142 or do i remember it being mentioned on the wiring regs course that here is a specific disconnection time.
I know that you measure the Earth Fault loop Impedance at the main switch when doing the COC (impedance shall be such that an earth fault current double the rated current (or higher) of the main protective device automatically disconnects the supply of the installation), but what about individual circuits and sub mains. Do you just rely on the above formula to prevent a touch voltage of 25 volts being reached before protective device operation?
Just used to working cables sizes out on disconnection times rather than touch voltage. Please correct me if I'm wrong, I'm still picking up on some of the variations in the SA way and the UK way. Its pretty much the same except you guys are not as strict with certain things(no offence meant by that by the way)
If there is specific disconnection times for different circumstances, where do i find this info, Thanks