In presented paper the model for economical and reliability based maintenance system of electric power distribution system is considered. This model considers the age based reliability of every distribution component of the power system. In our research the restricted test network is analyzed and the optimum reinvestment point of the whole network is found. The investment period of the single component is compared to the investment period of the whole network. In our research neither linear nor nonlinear optimization algorithm is used. The reason is that our test network is so small that it doesn’t take to much computing time to go through all valid investment alternatives.