Serbia: Rehabilitation of the pumped storage HPP “Bajina Bašta”

, News Serbia Energy

In the pumped storage HPP “Bajina Bašta” the final preparation phase of the Feasibility Study and Conceptual Design on recovery and adaptation of the power units and equimpent is in progress.- the replacement of the electric circuits is envisaged by the Conceptual Design and Feasibility Study, i.e. one unit per year.

PE “Drimsko-Limske HPPs“ in its five-year plan has two major projects in the pumped storage HPP “Bajina Bašta” rehabilitaion of the pumped storage HPP and construction of the frequency converter for starting its units. For the rehabilitation of the both projects funds must be provided in the next period.- Mijodrag Čitaković, director of the PE poinetd out.
In order to perform a new, major overhaul, very extensive and detailed preparations ,which last several years, are necessary. During 2012 certain tests were already done on the equipment of the pumped storage units. In the past three years numerous negotiations were conducted with the representatives of the “Toshiba”, as well as with the equipment suppliers and the preliminary scope of the technical specifications for the upcoming rehabilitation was agreed. The final phase of the preparation of the Feasibility Study and Conceptual Design on the recovery and adaptation of the units and equimpent in the pumped storage HPP “Bajina Bašta” is in progress. When this is defined entirely, the preconditions for PE “Drimsko-Limske HPPs“ to start the realization of that important project together with PE “Electric Power Industry of Serbia”, will be created.
– It is envisaged by the Conceptual Design and Feasibility Study the replacement of the electric circuits, i.e. one unit per year. The electric circuits would have new design, with higher level of beneficial effects. Type of the electric circuit, that will be mounted, depends on the Feasibility Study result and the analysis done by the chief designer of “ Energoprojekt Hidroinženjering“, and the results of the analysis preformed so far are positive- points out Dušan Trišić, manager of the Electrical Maintenance Department in HPP “Bajina Bašta”.
A huge step was also envisaged-a complete replacement of the motor- generator (еnergy part, energizing transformers and АВР) and turbine regulation system, because they are all part of the operation since the beginnig of HPP. јер су сви у погону од почетка рада електране. There will be a new system for the managment of the HPP. A modern computer distributive system of management will be applied, which means that the units will be managed through the operating stations in the central command of HPP. The connection with the newly installed video-wall on the central command will also be established. Within the major overhaul the replacement of the remaining equipment of the power unit is also envisaged,i.e. the replacement of current, voltage measurement transformers, power cabinets of certain consumers of power units and common equipment, as well as the replacement of consumable material and parts of the turbine and generator equipment.
In the last major overhaul the replacement of the stator and rotor winding, so this time only necessary reparations will be done. The existing way of putting the power unit in the pumped storage HPP into the pumping regime is performed according to the synchronous start method (back to back). For this purpose, one of the two power units of HPP “Bajina Bašta“ are used. They are connected to the transmission line 211 (H3 or H4). Precondition for the beginning of the synchronous start process is to stop both power units, and then to use one of them for the synchronous start, through the separate transmission line of 220 kV (so called transverse networks). Durning that process which lasts 10 to 15 minutes, there is a loss of energy produced by the power units H3 and H4, and the operation mode of the start power unit during the synchronous start is very unfavorable ( operations at low frequencies, increased levels of vibration and wear of equipment), which affects the shortening of the lifetime of those power units.
For this reason, during 2013 the Feasibility Study with the Conceptual Design on the mounting of the static frequency converter for putting in operation the power unit in the pumped storage HPP in the pumping regime was made, which demonstrated the feasibility of the project. The preparation of tender documentation for procurement of static frequency converter (SFC) and auxillary equipment (new 220 kV substation field and transformer 220/35 kV / kV, 31.5 MVA). the construction and some preparatory work and preparation of the documentation for the construction of construction for the placing SFC and the expansion of 220 kV in pumped storage HPP for devices of the transformer field. Preliminary Design of the installation of static frequent transformer is manufactured based on the preliminary offers and calculations of the four European manufacturers and the Company Toshiba, as the original supplier of the equipment for pumped-storag HPP. SFT is going to be of the powerr of about 20 megawatts, it is going to be supplied with the power from the grid of 220 kV, trough the special trafo field and substation of 220/35 kV, аnd it is also going to be capable to start the Power Unit in the pump operational regimen for about four minuttes. One device is envisaged for both Power Units in the pump-storage HPP , аnd they are going to be placed in the special building that is going to be placed near the upstream annex of the mechanical building of the pump stored HPP.
During the previous three decades of the operation, the pumped-stored HPP „Bajina Bašta” has proved the feasibility of being built. That was especially proved during the lack of electricity, when this PP, with the reserve of electricity stored in the accumulation in Zaovine , „jumped in” the system and in that way contributed to the removing of the difficulties in consumers’ supply. Pumped-storage HPP “Bajina Bašta” has one of the biggest accumulations of the capacity of about 150 million cubic meters of water (190 million kWh) and one of the largest net falls of water in the world (of 610 meters).

Ј. Petković


Sign for overhaul
The capital overhaul of both units and equipment of the pumped storage HPP “Bajina Bašta” was carried out during 2003 and 2004, and the value of the works amounted to 11 million dollars for parts and materials, which was financed by the donations of the Japanese Government. This type of overhaul, according to experience of “Toshiba” on similar projects in Japan, it is done after eight to ten years of plant operation. Although the units of the pumped storage HPP, after a major overhaul, worked reliably and without any major problems, during the last year more serious problems occured in some parts of the turbine equipment. It was a sure sign that it was time to perform a similar, major overhaul soon and revitalize the plant.

Unique in the world

The pumped storage HPP “Bajina Bašta” was built in 1982. The equipment was delivered by the Japanese “Toshiba“, and the assembly was performed by national companies, with the supervision of the Japanese experts. Today, after 32 years of countinuous work , this plant is still unique in the world. The merit for good and reliable operations so far belongs to quality construction and materials , but also to detailed maintenance and nurturing of this power pearl.

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