The crescent increase of the complexity of the electric power systems generates the need of development of tools to improve the analysis conditions. The objective of this work is to improve the computational tool of voltage security (stability) conditions assessment. As regards to the buses associated to remote voltage control by reactive power generation, new models that represent more appropriately the operatives conditions at the moment of the calculations of the voltage security indexes, are proposed. As regards to the bus associated to local voltage control by reactive power generation, it is proposed a new modeling, applicable as much in the power flow problem, using the Newton-Raphson method, as in the calculation of the voltage security indexes. This model, more robust and flexible, includes the local voltage control of the bus in the general power flow problem, constituting an equations system of order (2*number of system buses + number of buses with local voltage control). As regard to the multiples swing buses, it is proposed a new model, again to represents more appropriately the operatives conditions. It is applicable as much in the basic power flow problem, as in the calculation of the voltage security indexes. The proposed model considers that just one swing bus has your voltage angle specified and the others swing buses of the power system have your voltage angles free to vary.