An Expert system of Second Generation was used integrating the inverse Petri nets (RPN) and the systems based on rules (Rule-Based System) for the accomplishment of a program in Visual Basic that helps in the obtaining of an opportune and fast analysis of the systems of transmission of energy at the time of happening a fault in anyone of its components (line or bus). The program is proven in a portion of system IEEE-118 Standard bus Test System, in which two extracted cases of Literature are developed and are the obtained results. Finally tests realized with the method developed in the laboratory of machines of the National university of Colombia, Medellin campus, simulating a system of transmission with two lines and two buses.