The Rukani sector was a Delta Quadrant region of space mentioned in the holodeck program Insurrection Alpha. Upon ariving in the sector, captain Kathryn Janeway left in a shuttle to meet with the the Rukani. (VOY: "Worst Case Scenario")
As the Rukani and their sector were only mentioned in the Insurrection Alpha program and did not appear on-screen, it is possible that this region did not actually exist and was merely created for the program by Lieutenant Tuvok. If it did exist, the historical context of the program would imply it to be located in the region visited by Voyager in the first months after entering the Delta Quadrant, specifically before Seska left the ship in "State of Flux".