Since this - as I understand it - relates to a machine, you might want to try an engineering forum (like eng-tips.com).
Anyway, I asked Google and it answered that you should look to the national standard or the cable manufacturer. For lack of such information, HD 516 or IEC 60364-5-523 might be the place to go. Please note that I don't have these standards and am not familiar with the content.
There are other standards which are commonly referred to, e.g. IEC 60287, but I think that is mainly for voltages above 1 kV. I have no idea if this is of any help to you.
[This message has been edited by C-H (edited 10-15-2003).]