Network congestion (loadability) depends on the maximum amount of electric power that can be sent through a transmission system while maintaining its normal operating conditions. This indicator can vary to the point of being critical. A case of this are the scenarios with the presence of wind non-conventional renewable energy sources (RESs) included within the transmission system networks. By presenting fluctuations that come from the nature of the wind speed, threats and technical repercussions are generated within the stability of the network, creating uncertainty about tension control, and affecting loadability. This paper proposes a probabilistic analysis of the loadability of a transmission system with high participation of RESs using the point estimate method (PEM) which allows to implement a complete and agile evaluation in computational terms of the different scenarios with different proportions of RES in the transmission network. In the development of the study of the affectation of the loadability in a power system due to the uncertainty generated by the inclusion of RES, the IEEE system 24 buses is taken as a case of study, where two-buses of thermal generators were exchanged for wind RES to analyze indicators such as the total load margin and the minimum voltage load margin for different power injection scenarios.