Good day. Does the NEC only apply to voltages up to 2000V. And what about cable separations in cable trays? If you have a 13.8kV, 4160V, 480V and 110V cables, all MC cables, in one cable tray, should the different voltages be separated by a cable barrier from each other?

If the NEC doesn't spec on voltage separations I wouldn't think it would be an issue... or were you asking if it WAS in the NEC? The hockey arena we just wired had some interesting communications questions too, as far as separation is concerned. There was only one divider down the tray but we were running network, voice, control, broadcast and mic cables that, at some point, all seemed to ride with each other.

It's funny, in a test situation a lot of that stuff seems to interfere with each other, but in real world applications it almost never comes up as an issue.

From the 2008 edition of the NEC:

Section 392.6

(F) Cables Rated over 600 Volts.
Cables rated over 600 volts and those rated 600 volts or less installed in the same cable tray shall comply with either of the following:
(1) The cables rated over 600 volts are Type MC.
(2) The cables rated over 600 volts are separated from the cables rated 600 volts or less by a solid fixed barrier of a material compatible with the cable tray.