To evaluate the maximum loading point of a power system, steady state computational tools can be used, such as the continuation power flow. In order to obtain the maximum loading point in a realistic and reliable way, is essential detailed representation of power system elements and the reactive power limits of the slow action voltage control equipments. The individual generators representation, including their capacity curves, leads to adequate reactive power limits in PV buses and the correct step-up transformer impedance when a other machine unit is added to meet the global active power dispatch of a power plant that follows the loading rise in continuous power flow method. The main goal of this paper is to assess the impact of the detailed generation representation on the power system loading margins, in comparison to equivalent generation model that uses fixed reactive power limits and no changing the step-up transformer impedance.