I don't know; I always got the sense that the use of the word "quadrant" varied from writer to writer, and what makes up a "quadrant" changes not only show to show but episode to episode. Voyager spent 7 years in the Delta quadrant, while in Star Trek 6 Sulu's Excelsior was inconveniently far away from the Enterprise because "We're now in...(pause to check console) Alpha quadrant." and had to "fly her apart then!" to get to Enterprise in a matter of minutes or hours.