A new, accurate and efficient model for long range transmission planning is developed in this paper. The model applies a constrained Genetic Algorithm using Matlab where the system stability constraints, in item of upper and lower limits on the system bus voltage and swing angles, are easily included. The accurate AC load flow equations are also included in the Algorithm. An accurate cost function for the transmission system is formulated where both fixed and variable costs for all planned facilities are included, in addition to the cost of energy loss. the cost function is then minimized, subject to system constraints, using a constrained genetic algorithm. the model is capable of handling ONLY the static mode of planning. the IEEE-6 bus system is used to test and justify the applicability of the new developed model.