I don't think the 480 line will induce enough noise into the network line to be a problem (the tightly twisted pairs in the cat 6 cable means a very good common mode noise rejection http://en.wikipedia.org/wiki/Twisted_pair).
I think the problem you are going to run into is lightening. Strikes anywhere close will produce voltage differentials large enough to fry the transceivers on either end of the run. Ethernet surge protectors on both ends will help this. As others have mentioned, fiber is the way to go on this. From: Eldridge, Dave [mailto:[email protected]] Sent: Wednesday, April 07, 2010 7:55 AM To: NT System Admin Issues Subject: OT: question on cat-6 and 480V together I am being told that one of our MRI machines is temporarily moving to a trailer out on the street and they want to pull overhead a cat-6 and 3phase 480V together. Way out of my league. Anyone see any noise issues with these tied together? Anything else I'm missing? thanks This e-mail contains the thoughts and opinions of the sender and does not represent official Parkview Medical Center policy. This communication is intended only for the recipient(s) named above, may be confidential and/or legally privileged: and, must be treated as such in accordance with state and federal laws. If you are not the intended recipient, you are hereby notified that any use of this communication, or any of its contents, is prohibited. If you have received this communication in error, please return to sender and delete the message from your computer system.{token} ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
