The traditional thermal and nuclear power plants are concentrated geographically. If such new power plants are planned, suitable routes which reach to nearest substations are suggested. The wind turbines in wind power plants, however, are scattered in a vast region. It's challenging to connect them and gather energy. However, there has been a few research of the method connecting wind turbines in a wind plant. In this paper, a planning method which optimizes the installation cost of power lines is developed. The target is an optimal design of power lines 'in' large wind power plants. Specifically, we speculated a situation that installs roughly 50 wind generators (single unit at 3MW) in a vast region. Also, we have taken a consideration to establish an optimal network to reduce the transmission overload when power reaches to the aggregating point. Optimal placement of towers and/or link of wind farms are out of our scope.