There is Type-W power cable. It is very heavy duty and usually is rated for 2000V intead of 600V like SO.
This is the stuff the Military uses for their portable power distrubution in the field, so it must be able to stand up to considerable abuse. Here is a link to inw manufacture http://www.acewireco.com/pdfs/6401.pdf
[This message has been edited by IanR (edited 02-21-2007).]