Portal? MQ? The one in the Labrynthian?
Or are you talking about the portal to Solvangarde in Skuldafn
Just make a test cell, use the GenKit and create a square room with it, or any interior kit you prefer. Place the portal in there. Then in game coc to the room and see how it animates, or whatever you need.
OR - tick the box in the CK that says "FX" and see what that does. It works for the Eye of Magus.
The one that spawns by Paarthunax is animated but it may not be sufficient. And course there is the one in Skuldafn. I can't remember any others.