Serbia: Preparations of “HPP Djerdap” for the winter season; Overhauls in full swing

Published on 24. October 2013., News Serbia Energy

Extensive works on the six-month capital overhaul of water locks are in progress.

– Capital overhaul of the power unit A8 in HPP “Djerdap 2” completed in early September. – The “Vlasinske HPPs” in full operational readiness towards the end of 2013.

The overhaul activities performed in all four branches of the company “HPP Djerdap” have been successful and on schedule, which is very important.

The works in the largest member, “Djerdap 1 “, have been simultaneously executed on three fronts. Rehabilitation of the A4 is in the closing stage where Acceptance tests are conducted and the shaft line deviation corrected.  Simultaneously, in an impressive machine hall, “Djerdap” professionals perform overhaul of the power unit No. 2. The works performed are type of standard works that were conducted on the A1 in August and on the A3 in the first half of September. At the same time, the transformer – block No.1 is being repaired and preparation for replacement of the transformer block No. 3 is in progress.

The new 420 MVA transformer that comes preassembled is more powerful than the old one it should replace at a favorable moment. According to Mr. Ljubiša Jokić, Director of the HPP “Djerdap 1” and Mr. Milorad Gerginić, assistant Director for the maintenance, this replacement will take 35 days. This undoubtedly complex and demanding operation shall start as soon as the new A4 is attached to the network, i.e. when the dismantling of the A5 starts, thus marking the beginning of the third phase of the first Danube HPP revitalization. Another power unit that is also connected to the grid via transformer block No. 3 needs to be detached from the grid during the replacement, and it is the revitalized unit A6.

In addition, the ongoing activities include extensive works featuring the 6 month capital overhaul of water locks that started on 20th May and that according to the schedule should be finished by 20th November. The respective deadline will be met, even though the works started in unfavorable climatic conditions characterized with a high level of the Danube water.

– Some works on the lower door including most extensive and demanding works had to be delayed because of the high water – informed us Mr. Davor Maljoković, the head of this part of HPP “Djerdap 1”. – The delay was however compensated through an extraordinary commitment of workers involved, and the volume of works completed so far make us believe that the deadline for completion of water locks overhaul will be met. This is very important considering that the regulation on smooth sailing in this part of the Danube is an international obligation of the company “Djerdap”.

By now, all the works including the recovery of both gallery shutters on the upper head have been completed. The new doors have been checked that was manufactured in the company “Goša” two years ago with a warranty of 10 years. The inspection results proved positive as no unexpected cracks or major damages were found. The pump units of the medium head were replaced, worn hydraulics and wiring serviced, and a crack on the medium door remediated with the rubber gaskets being replaced there. On the bottom, downstream head works are in full swing. Here, the old timber is being dismantled and all welds and joints of massive steel structure tested, which should be followed with corrosion protection and timber installation.

Overhauls of the HPP “Iron Gate 2” are also in full swing and according to the schedule.

– The capital overhaul of the A8 was completed on schedule in early September and it included replacement of the excitation system in addition to standard maintenance activities, – explained Mr. Jovan Milovanović, the “Djerdap” unit director – A new excitation system was also installed on the A2 and fairly soon, by the beginning of December, such a system will be installed on the A7 that is currently overhauled. By this, the cycle of modernization and unification of the primary power equipment shall be completed, which is practically the first stage of the ongoing revitalization within which outdated hydro-mechanical and electrical equipment will be replaced. Further replacement of the excitation systems within the additional plant is scheduled for the next year and it refers to the A9 and A10

The remaining overhaul activities shall include a shorter repair of the first stage of water locks, with the aim to ensure that the problems identified in the operation of complex mechanical, hydraulic and electrical equipment will be remedied timely and the equipment prepared for the harsh conditions of the upcoming winter. At the same time, testing of spillway dam equipment  which is aimed at understanding the necessity and scope of the reconstruction procedure, should be finished.

So far everything goes according to the plan and it is quite likely that HPP “Djerdap 2” will achieve full operational readiness by the mid-December, which is the deadline for overhauls, so from that point on all 10 power units could be engaged on utilizing the hydropower potential of the great river.

Operational readiness of “Vlasinske HPPs” will be also ensured for the upcoming winter. The overhaul season started here in July with the overhaul of the PAP (Pump Accumulation Plant) “Lisine”. This year, planned preventive maintenance of the plant was completed ahead of the schedule along with an unexpected replacement of the block-transformer, so the plant will be timely available for pumping water from the water storage of Lisine to Vlasina Lake.

The overhaul in all four plants of “Vrla” began on August 9th as planned, and the maintenance of the first line power units was to finish on October 17th while the maintenance of the second line power units is scheduled to finish before November 1st. So far the work is carried out successfully and according to the plan. Apart from regular activities within the scope of the planned-preventive maintenance in “Vrla 1” and “Vrla 3”, replacement of static excitation and installation of new electrical braking are performed.

– The cycle of modernization and unification of equipment is being continued – said Mr. Milorad Jovanović, Assistant Director of “Vlasinske HPPs” for maintenance. – On the top of that, installation of other modern equipment is going to contribute significantly to the safety and reliability of the oldest member of the company “HPPs Djerdap”, which will mark 58 years of operation on November 6th. In addition, construction works relating to the maintenance of tunnels and delivery channels were carried out. All in all, “Vlasinske HPPs” will welcome the end of 2013 with full operational readiness, and which is very important – with the storage of “Vlasina Lake” being enough for generation of near 160 million kWh and an overfulfillment of the nine-month production plan of 3%.

Good production output of the HPP “Pirot”

The youngest and smallest member of the company “HPPs Djerdap” – HPP “Pirot” has already carried out planned preventive maintenance. The activities performed in the period from August 31th to September 24th included standard maintenance but also wedging of rotor poles on the both power units.

– In addition, an inspection of the relevant pipeline was performed by applying a nondestructive method of screening in order to find out, investigate, and timely remediate the cracks found – says Mr. Zoran Ilić, the Director of the peak HPP “Pirot”. – Also, a part of the tunnel was repaired by necessary excavation due to the leached soil. So the HPP “Pirot” welcomes the end of the third quarter fully prepared for the processing of hydroelectric potential of the water storage “Zavoj” which is currently sufficient to produce 55 million kWh. This created conditions for the peak HPP Pirot to significantly outperform and even double the liability under the plan, as it recorded a production of 61.5 million kWh at the end of August, which is 18% more than planned production of 52 million kWh for the year 2013.

Source; EPS / KWh