The electric supply systems of the non-ferrous metallurgy plants use a great number of a synchronic powerful engines (6 kv voltage) being the main reactive power consumer to provide the normal technological equipment operation (pumps, ventilators, gas blowers, crusher etc). AE working in the block “AE – BSK” are used as an electric drive. That is why the development of complex methods for optimality criterion calculation as the quantitative estimation of the block reliable operation at the industrial enterprises is the actual task.