Tie line planning using probabilistic load model

Interconnection planning of power systems requires the evaluation of location and capacity of tie lines that ensure optimum operating cost and optimum rate of return on the investment. Tie line planning is a complicated combinational problem to select a solution from a finite set of possible outcomes. This paper presents a tie line planning method using probabilistic load model. This method decomposes the planning problem into a number of smaller optimization problems those are solved using AC optimal power flow (OPF) technique. At first, at every load level, the OPF is used to evaluate the optimum capacity and location of a tie line. The cost function includes both the tie line cost and the energy production cost for a particular load level. The energy production cost for the whole planning period is evaluated in the next stage considering the evaluated optimum tie line obtained for a particular load level. Appropriate penalty cost is introduced if the tie capacity determined at a particular load level is over or under sized with respect to the optimum capacity obtained for other load levels. The costs associated with each load level are then compared to choose the tie line with minimum overall cost. The proposed methodology is applied on IEEE Two Area Reliability Test System (RTS) 1996 to determine the tie line capacity and location.