MV Cable Short Circuit Rating

This site has information put out by ICEA regarding your question. Wire size is in Cirmills so you will have to convert to mm .http://www.bussmann.com/library/techspec/TechSpec19_sup.pdf

Quote "Do I just take the fault level as given by cable manufacturers (AS, IEC etc.) and spec. it accordingly or should I consider time in the fault by the breaker limiting the fault level, i.e. best time is eg. 0.1 sec hence the "let through energy" is I*I*t (fault current squared multiplied by time) compared to the equivalent of the energy the cable can handle? If so do I use RMS fault current or Peak fault current?"

The 40 ka for 1 sec is the fault available from the utility. You should consider the fault level at you main switch and the time that it will exist. You over current device may interrupt the fault in 0.10 seconds and therefore the cable could be sized smaller. What do you mean by fault level given by mfg? How is it listed?

How is the breaker limiting the fault current level? The breaker limits the time the fault exists. Some approved series rated devices do limit the fault but they must have been tested and approved for this use. What type of over current protection do you have?