According to ANSI/TIA/EIA-568-A standard, "horizontal wiring" from a wiring closet to the outlet should be 90 meters or less, plus another 3 meters for a patch cord to the workstation. In round numbers, that's about 300 feet.
If you plan to connect between buildings with different power sources, or go beyond 300 feet, you should consider using fiberoptic line with a media converter at each end. -- by DTVtech
