In-Situ Measurement Campaign at the “Perućica” Hydropower Plant in Montenegro - Part 2: Pressurized System

 Danica Starinac1, Dragiša Žugić1, Zvonimir Predić2, Aleksandar Gajić3, Dušan Džopalić2 and Predrag Vojt1

 

 

1 Jaroslav Černi Institute for the Development of Water Resources, Jaroslava Černog 80, 11226 Pinosava, Belgrade, Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 A.P. Company, Koste Taušanovića 2, 11120 Belgrade; Serbia, E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

3 University of Belgrade - Faculty of Mechanical Engineering, Kraljice Marije 16, 11120 Belgrade, Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

 

Abstract

The Hydraulic Department of the Jaroslav Černi Institute for the Development of Water Resources undertook an important measurement campaign under the Perućica HPP Modernization and Revitalization Project. The campaign included in-situ measurements (water levels, discharges, pressures, displacements, stresses and vibrations) at different locations throughout the HPP system. Numerous steady-state and unsteady-state scenarios were tested, through continuous and simultaneous measurements at all measurement points. This paper presents the measurements carried out in the pressurized system, starting from the power intake structure and ending with the tailrace system. The applied measurement and data acquisition methodology is explained, followed by results and conclusions. The measurement campaign provided valuable data for the calibration of a mathematical model, as well as insight into the operation of particular parts of the system.

Keywords: hydropower plant, in-situ measurements, measurement campaign, Perućica, pressurized system

 

Introduction

 

In June 2010, the Hydraulic Department of the Jaroslav Černi Institute for the Development of Water Resources undertook an important measurement campaign under the Modernization and Revitalization Project of the ''Perućica'' hydropower plant (HPP) (Starinac et al., 2011).

During the entire period of service, the HPP has never been operated at the maximum power of 307 MW (total installed capacity), but only to 285 MW. The average annual output (1960 to 1999) was 823 million KWh, or about 63% of the potential annual capacity.

Many studies and analyses, such as in-situ measurements, mathematical simulations, observations, etc. (Djonin et al. 1984; Petrović and Djonin, 1986) have been undertaken with the objective to determine the origins of the problems and to identify the measures best suited to the elimination, or at least alleviation, of the problems. Based on the outcomes, the operating power level was increased to 285 MW. The main reasons for this limitation were inadmissible mechanical vibrations of the turbine housing and load fluctuations, especially in the tailrace system and particularly during load change, load rejection and shut down operations (Gajić et al. 1998).

The Perućica HPP Modernization and Revitalization Project is aimed at increasing the operating capacity up to the installed power level as a first step and, after analyzing the possibilities for installing a new, eighth generating unit, increasing the capacity even further. For that purpose, it was necessary to carry out detailed analyses of the entire system, including mathematical modeling. For model calibration, parameter values based on in-situ measurements were required.

The measurement campaign included in-situ recording of water levels, discharges, pressures, displacements, stresses and vibrations, at different locations throughout the Perućica HPP system, in order to identify the origin of the existing problems and to define the basis for rehabilitation. All measurements were continuous and simultaneous, due to the requirement to obtain real information on system behavior under different conditions and to provide adequate data for mathematical model calibration.

Considering different hydraulic characteristics, the system could be divided into two parts – an open channel system (upstream of the power intake ''Marin Krst") and a pressurized system (downstream of the power intake). In this paper, the measurements carried out in the pressurized system are presented through an explanation of the applied methodology, followed by results and conclusions.

 

 

Description of the System

The Perućica HPP is located on the Zeta River, in the central part of Montenegro, near the Town of Nikšić. The HPP has been designed for eight generating units, but only seven were constructed in the first phase, with a total installed capacity of 307 MW. The system makes use of the energy potential of the Zeta River (catchment area 850 km², gross head 550 m), between its upper course (the Upper Zeta River) at Nikšić Polje and its lower course (the Lower Zeta River) close to Glava Zete.

Hydropower plant configuration

The HPP has been planned and designed as a high-head run-of-the-river hydropower plant, in combination with three water storage reservoirs.

According to this configuration, the Zeta River (at Nikšić Polje) was planned as the main supply source for the Perućica HPP. The initial design called for the impounding of the Zeta River by the Vrtac Dam, for controlled release and use for power generation in line with the power demand. In addition to the Zeta River, plans called for the utilization of the Moštanica River and the Opačica River, through impoundment by the Krupac Dam and the Slano Dam, respectively. 

This concept meant that both reservoirs, Krupac and Slano, would contribute to the power generation by releasing water into the Vrtac Reservoir, as a regulating structure for the Perućica HPP headwater. From the Vrtac Dam, water is conveyed by a feeder canal, Zeta I, to a compensation basin and the power intake at Marin Krst. The compensation basin has sufficient capacity to provide water during the startup of the power plant or when additional units are initiated. Similarly, the compensation basin preserves water when the units are shut down.

Pressurized system

The pressurized system includes structures located downstream of the power intake ''Marin Krst'': headrace pressurized system, powerhouse and tailrace system (which is analyzed in this paper even though it has the characteristics of an open channel flow).

From the power intake, the headwater is conveyed to the powerhouse and to each turbine through a pressurized system (Figure 1). After passing the power intake, the water enters a headrace tunnel (length 3,323 m, diameter 4.8 m), which branches into three penstocks at a trifurcation, at some distance downstream from a surge tank. Each penstock is provided with a butterfly-type emergency valve. The valves are housed in a valve chamber "Povija" (Figures 2 and 3). The penstock data are summarized in Table 1.