Wind speed varies continuously throughout a day resulting in fluctuating wind farm output power. When such a farm is connected to the grid through a line, the transmitted power and the relay end voltage (with respect to grid voltage)fluctuate continuously. In this paper, the protection of such a line with distance relay is investigated. The ideal trip characteristic for distance relay is studied with change in conditions of the wind farm. A method is proposed to set the boundary adaptively using local information only.