I. Introduction
The electric power production and supply is of significant importance for ensuring the wellbeing and safety of any country, and its value is crucial for the development of human activities and life quality. The development of social and economic activities of mankind requires the constant increase in the consumption of electric power. As the result of this development, the scale (increase in size) of electric power grids are growing. When there is a lack of power at times of peak loads in a big-scale grid, the probability of big-scale fluctuation increases, which turns the system from deterministic to stochastic. Unpredictable manifestations of big-scale fluctuation spread in the form of a cascade of failures through the grid, which lead to the loss of reliability of the operation of the power grid, and the occurrence of global interruptions in the power supply of big cities up to the disconnection of a big number of consumers (big-scale power outages in the USA in 2003). This state of affairs is connected with the fact that the existing system of centralized (dispatching) management of the supply of electric energy and the existing information support for decision-making cannot promptly detect trends of approaching supply problems and, accordingly, respond to them.