The full-scale experiment was made in the Siberian interconnected power system in November 2002. The cause of this exploration is a necessity to make sure that the program, being used for more than 10 years for long-term stability assessment in power systems, simulates dynamics properly. The second motive to execute the full-scale experiment is the start of processes of deregulation in the power industry and an absolute necessity to guarantee that the frequency in Russian power systems can satisfy the European standards. One of the actions to do this consists in an estimation of the frequency-control capacity of the power plants. Simulation of electromechanical transients in large-scale power systems is another side of this exploration. This paper represents the conditions of preparation, carrying-out and the results of simulation of the processes existed during the experiment