On Evaluating the State of a Hydropower System’s Hydraulic Engineering Structures under Modern Conditions

Abstract

The effect the limitations imposed on the water storage reservoir’s headrace level (HRL) variation rate have on the hydroelectric power plant (HPP) power performance indicators is studied taking the cascade of Yenisei HPPs as an example. For quantitatively determining the effect the limitations imposed on the Sayano-Shushenskaya HPP’s HRL variation rate (depending on the air temperature in the preceding period) have on the HPP power performance indicators, water energy calculations were carried out for the following Yenisei cascade operation scenarios:

• operation of the Sayano-Shushenskaya HPP with variable limitations imposed on the HRL variation rate depending on the air temperature in the previous period;
• operation of the Sayano-Shushenskaya and Krasnoyarsk HPPs with variable limitations imposed on the HRL variation rate depending on the air temperature in the previous period.

The mean energy capability (E0) and the guaranteed power output in winter (Nguar) were taken as the HPP performance indicators from which the effect of limitations was estimated.

As a result of the accomplished computations, the guaranteed winter power output in the Sayano-Shushenskaya hydropower system decreased by 17.37%, and its mean energy capability decreased by 3.29%.

Based on the accomplished water-energy calculations, a new (corrected) operating mode of the Sayano-Shushenskaya HPP was obtained, in which the regime of levels did not escape beyond the temperature-related limitations. The changes in the Sayano-Shushenskaya HPP operation mode led to a change in the HPP tail race flows. As a result, the Krashoyarsk HPP operation mode was also changed due to the new inflow regime to its site. The study results show very clearly that application of environment temperature-related limitations on the Sayano-Shushenskaya HPP hydraulic structures directly affects the power performance indicators of the Krasnoyarsk HPP. The strongest effect on the Krasnoyarsk HPP parameters takes place at the average temperature in the Karlov site from –17 °С to –11.8 °С in winter and from +8.5 °С to +11 °С in summer. This is connected with the Sayano-Shushenskaya HPP HRL variation rate limitation curve pattern, which in its turn entails a decrease in the HPP tail race flow and, as a consequence, a decrease in the total inflow to the Krasnoyarsk HPP site. As regards the temperature range at the Krasnoyarskaya HPP site, it is from –20 °C to –11 °C for the winter period and from +5 °C to +8 °C for the summer period. The difference in the mean energy capability and guaranteed power output of the Krasnoyarsk HPP during operation under the above-mentioned conditions is 12.9% for mean energy capability and 13.7% for guaranteed winter power output.

Key words: limitation of water level variation rate in a water storage reservoir, change of power performance parameters, cascade of Yenisei HPPs.