In-Situ Measuring Campaign at the Hydropower Plant ‘‘Perućica’’, Montenegro - Part 1: Open Channel System - page 6

The reason for providing such a scenario (including the increase and reduction of discharge) is the information that this procedure provides: steady state conditions needed for the hydraulic characteristics of the gates and resistance, as well as unsteady flow.

As an example of such a measurement type, the UP2 scenario is presented. Operating conditions that were planned for the UP2 scenario are given in Table 4.

Presently, the HPP system operation is mostly based on decades of experience, while the hydraulic characteristics of the gates are insufficient and uncertain. At the Krupac Dam, the scale of the gate (Figure 7) makes reading its position in percentage impossible (the scale finger is broken), so an experiment was done to note a number of "rounds" whilst manipulating. However, since the mechanism of the needle valve was out of order, at every manipulation, sliding occurred in the valve recess, with variable results. For example, at one trial there was a need to make 90 "rounds" in order to completely open the valve, but at the next occasion there was a need to make up to 150 "rounds". Consequently, it is quite clear that it was not possible to provide certain operation, so it would not be surprising to expect some discrepancies between the planned values (Table 4) and the measured ones (Table 5).

 

Table 4: Operating conditions during the UP2 scenario

Table4

 

Table 5: Discharges measured by ADCP during the UP2 scenario

Table5

 

Since the system is spread out on a large area, barometric pressure is not constant, so for the water level measurements it was important to provide relevant data. Figures 11 and 12 present variations of barometric pressure during scenario UP2. It could be seen that the variation is not the same at the two points, as well as that the maximal variation is around 4 cm of water column.

The variations of water levels in reservoirs (Figures 13 and 14) were relatively small. The changes were caused by a change of volume in the reservoirs due to the outflow discharges.

The water level at the upstream boundary is presented in Figure 15. It can be observed that there was no significant change in the Zeta River discharge during the UP2 scenario.

Water levels in canals downstream of the reservoirs are shown in Figures 16 and 17. The water level in the Moštanica canal was practically constant (variation was less than 1 cm) during the UP2 scenario, due to the operating conditions at the Krupac dam gate, which had not been changed.

Water level in the Opačica canal (Figure 17) shows that steady state conditions could be reached in approximately 3 hours. Discharges were measured during the steady flow periods, which is important for a valid determination of hydraulic characteristics of the gates as well as for rating curves. At the same time, these discharges present the upstream boundary conditions.