Abstract-- An important component to be considered in electric power system expansion planning is the security of service that the system is able to provide. In restructured power systems, variables such as agents’ profit or Locational Marginal Price (LMP) variances are considered in transmission expansion planning. Finally to have a secure network this plan would be refined for simulated contingencies. This paper proposes a new method for transmission expansion planning in which the Grid Owner (GO) is responsible for expansion while benefiting a fair benefit percentage. The objective function of transmission expansion tries to reduce weighted standard deviation of LMPs and the construction cost as well as the cost of security enhancement. For different scenarios of expansion; at first, the cost of security enhancement is calculated and then it is considered in the objective function of expansion. To investigate the validity of the method, we have applied it to the modified “Garver 6-bus test system for expansion”.

Keywords