  This work is devoted to the construction and study of a mathematical model of
hydropower unit, consisting of synchronous generator, hydraulic turbine, and
speed governor. It is motivated by the accident happened on the
Sayano-Shushenskaya hydropower plant in 2009 year. Parameters of the
Sayano-Shushenskaya hydropower plant were used for modeling the system.
Oscillations in zones, which were not recommended for operation, were found.
The obtained results are consistent with the full-scale test results carried
out for hydropower units of the Sayano-Shushenskaya hydropower plant in 1988.
