curent rating of conductor

http://www.houwire.com/products/technical/article310_16.html

Use the 75C rating

Following are the considerations to determine the current rating of the conductor,

1) Per phase load current

2) The fault level

3) Voltage application

4) Installation method

Once you know the above get the few cable manufacturers' catalogues. The catalogue should give you the following minimum information about the

1) kA rating for each size of the cable

2) Insulation level for the voltage

3) Resistance values/km: To calculate the volt drop

4) Size of the conductor depending on the current carrying capacity.

5) Temperature rise allowed: This depends on the installation and the load

Then you can choose proper size with the following conditions the the voltage drop will be limited to 5%, Temperature rise to be limited to 50deg C etc. Also de-rate the cable accordingly for the above conditions and choose the appropriate size.

British Standard 7671, or the current edition of the Wiring Regulatons.

Can you please provide a link to the British standard.

Thanking you...