Hello Patelcab,
I am sure there are standards for the sector shapes in your county in so far as the maximum and minimum sector dimensions are concerned. They are, as you already know, stranded together after insulating in low voltage cables. The thickness and insulation materials are also to a standard specification. The conductors are rolled shapes and each company as best as I can tell, develops the precise shape of their particular stranding forming rollers by trial and error. Thus it is intellectual property belonging to each company and not likely to be divulged.
If anyone has more information, I would certainly appreciate your assistance.
The trapezoidal shape on a casting wheel seems to be an optimum for that particular process. The trapezoidal shape isn't really a problem because the rod changes it's shape a number of times in the rolling mills before becoming a round cross section.
Kindest Regards,
Peter Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com