A technology watching study based bibliometric analysis and in patent analysis, of current technologies and study of methods for preventive control to solve transient stability problems in Electrical Power Systems (EPS), is made. Likewise, current systems used for real-time operation that guarantee safe operation in Electrical power systems, are analyzed. In the study of current technologies, we look for solutions based on the application of direct methods to guarantee secure operation for different contingences scenarios of the EPS. This study allows formulate the preventive control as an optimal power flow (OPF) problem with transient stability constraints formulated through direct methods with the target to accelerate computational process. This formulation will be applied in an Electrical Power system, having a reduced number of control variables.