This work presents a description of the development of a model for representation of simplified grid applied in hybrid load flow for calculation of the voltage variations in steady-state provoked by wind farm on power system with two different treatments for boundary buses. At the beginning of the analysis process on system, lead for the wind producer, it has as base given technician data supplied by the concessionaire. The main aim consists to propose models of simplified networks that allow to the necessity of the knowledge only of the data referring the internal network, that is, the parcel of the network of interest for analysis. This way, it is intended to supply forms for auxiliary in the systematization of the relations between the sector agents. The model of simplified network proposed identifies the internal network, external network and the boundary buses from a vulnerability study of the grid, testing to the boundary buses active and reactive powers floating model (slack buses) and determination of powers by optimization process using Particle Swarm Optimization. It was opted to apply the cited model in a hybrid load flow, composite by Gauss Seidel Zbus and Summation Power methods. Finally, presents the results obtained for a developed computational environment of FORTRAN, with their respective analysis and conclusion.