Rekonstrukcija transformatorske stanice 35/10kV u spoljašnje razvodno postrojenje 20kV 20211, XXIII

In the distribution area of Novi Sad, owned by ODS EPS Distribucija, there are 35 substations 35/10kV that are on average over 50 years old. Considering the tendency to gradually eliminate the voltage levels of 35kV and 10kV in this distribution area and the transition to the voltage level of 20kV, some of these substations are planned for reconstruction into 20kV distribution plants. Reconstruction of these substations requires large financial resources, because their construction part is in a very bad condition, electric power equipment is unreliable and difficult to maintain, and operational readiness is an increasingly important factor in presenting successful business. During the reconstruction of these transformer stations, the possibility of a backup power supply route for electricity customers, the speed of intervention and the smooth performance of preventive maintenance must be taken into account. The appearance of reclosers opened a new chapter in the world of electricity. Namely, now the above problems and requirements can be solved in a simpler and cheaper way with the use of reclosers. The paper will present a proposal for the reconstruction of the substaion 35/10 kV "Kuzmin" in the area of the Branch Distribution Sremska Mitrovica, which has been operating for more than 60 years, in an external 20 kV distribution plant formed with the help of reclosers built on steel lattice poles. The proposed solution can be used to solve the same or similar problems, primarily in the distribution area of Novi Sad.

Simulacija i odstranjivanje stick-slip efekta servosistema sprovodnog aparata hidraulične turbine

Friction is a repeatable and undesirable problem in hydraulic systems where always has to be a tendency for its removal. In this paper, the friction model is presented through which the most accurate results are achieved and the way of friction compensation, approached trough technique presented with the mathematical model of a hydraulic cylinder of a hydro turbine wicket gate controlled by a servomechanism. Mathematical modelling of a servo mechanism and hydraulic actuator, and also the simulation of hydraulic cylinder as a part of a hydro turbine wicket gate hydraulic system where the stick-slip phenomenon is present between the system components that are in contact is presented. Applied results in this paper and the theory behind them precisely demonstrate under what circumstances the stick-slip phenomenon appears in such a system. The stick-slip effect is simulated using Simulink and Hopsan software and the analysis of the results are given in this paper. Removal of the stick-slip effect is presented with the design of a cascade control implemented to control the behaviour of the system and remove the appearance of a jerking motion.

Tržište električne energije u Republici Srpskoj i Bosni i Hercegovini – pregled i analiza u 2020. godini

- Electricity markets in the Western Balkans are still not fully liberalized, so different of degrees electricity market openness can be observed from country to country and even within the country - Bosnia and Herzegovina is an obvious example. In Republika Srpska, the formal legal conditions for starting the process of opening the electricity market were met with the entry into force of the Law on Electricity in late 2007 and the Rulebook on Supplying Qualified Customers and the Procedure for Changing Suppliers, which entered into force in late 2014. However, the actual process of opening the electricity market did not begin until the Ordinance on Amendments to the Ordinance on the Supply of Qualified Customers and the Procedure for Changing Suppliers entered into force, which entered into force in March 2019. The paper first examines and analyses the activities carried out so far on the liberalization of the electricity market, and provides an assessment of achieved results. The necessary conditions and issues that arise before the further opening of the electricity market in the Republic of Srpska are further analysed. Finally, the most important activities that await all relevant actors, first the RS Government, then the line ministry and RERS, suppliers and businesses that actively participate in shaping the electricity market in order to prepare the market for further opening and meeting conditions for its successful completion were analysed in the text.

Rekonfiguracija distributivne mreže i otočna kompenzacija uz prisustvo vetro generatora

In this paper, the distribution network reconfiguration with simultaneous capacitor switching, in the presence of wind generators, by Simulated Annealing (SA) is presented. Analysed test network has 69 nodes including the slack one and 73 branches, all of which can commutate. Following assumptions are made: load in nodes is changed according to Gauss distribution and wind generator power with Weibull one, every hour, then there are two wind generators of 200 kW maximum power each (10% of total, nominal active power load) and they can be allocated to any node but the slack one. The same is valid for the capacitor banks regarding allocation. This switching logic is unrealistic. On its basis more realistic one was issued with fixed nodes for allocation of wind generators and capacitor banks (the most frequently visited nodes), by Monte Carlo graphical method. Input power factor is to be greater than 0.85 which is not fulfilled with commencing configuration (from the start) so that allocation of capacitor banks is mandatory. Another constraint is that the network should not be overcompensated. Four realistic scenarios are investigated. In the first one only network with wind generators is analysed and the rest are dedicated to all possible combinations of the regulation. The programme is automated indicating the price of configuration, generated banks, input data (active and reactive load, power and location of wind generators) and savings which change on an hourly basis. The wind generators are uniformly distributed in accordance to nodes (for the less realistic scenario) and generate only active power complying with Weibull distribution. The graphical results are presented for a 1000-hour operation (operation in one thousand hours, every hour different) and the analysis is done for a thousand-hour work. The presented method shows that considerable savings can be achieved by simultaneous application of reconfiguration method and capacitor switching with already allocated wind generators.

Analiza potencijala za uvođenje sistema pametnih mreža u Bosni i Hercegovini

The paper presents an analysis of the current situation regarding the development of an electricity distribution network and potential for a smart grid development in the selected pilot region of Bosnia and Herzegovina. Apart from the policy framework assessment, several indicator based criteria were included in the scope of analysis: share of renewable energy and renewable energy as distributed energy resource, total share of distributed energy resources, a number of installed smart meters for measuring electricity consumption, a number of charging stations for electric vehicles, energy storage capacities and technological development. The overall analysis of the assessment has been done by normalization of the calculated values of the indicators on a scale of 1-5. The indicators have showed that the smart grid sector in the Region is currently underdeveloped.

Višestepena brza regulacija frekvencije u elektroenergetskim sistemima sa neravnomernom distribucijom inercije

Integration of renewable energy sources (RES) is one of the key factors in the fight against climate change and they are becoming to take a larger share in electricity production. The systems with a high penetration of RES have small rotational inertia and are more vulnerable in terms of frequency stability. This paper proposes strategy for multistage fast frequency control (FFC) provided by converter-connected resources. They can quickly change the output active power and provide frequency support immediately after the disturbance during the period before that frequency reaches its nadir. The proposed control strategy uses only local measurements of the rate of change of frequency (RoCoF) and there is no need for complex telecommunications infrastructure. The multistage approach enables dispatched reserve to be proportional to the size of disturbance. RoCoF based FFC provides that more reserves would be dispatched in low-inertia areas that are more sensitive to disturbance and therefore enhance frequency stability. The proposed control strategy is validated on a test system of 3 coherent areas and the simulation results confirm that more reserve is dispatched in low-inertia areas that are more affected by disturbance.

Idejno rešenje regionalnog Data Centra kod Beograda napajanog iz obnovljivih izvora energije

Telecommunications and computer equipment centralisation trends for the purpose of achieving economic benefits, usage of technological innovations and new technical solutions implementation leads to the requirements for building bigger Data Centres (DCs). An increase in the size of the DC facility i.e. the number of racks inside occupied with equipment and the number of devices that enables the proper functioning of that equipment leads to necessarily power energy requirements increasing for power supply. For the DCs that require a large amount of energy, the building of their own, usually renewable energy sources (RES) is cost-effective. In such a caser, RES are primary and Power System (PS) is secondary and redundant power source. A concept of a DC primary powered from RES is presented in this paper. Generated electrical energy in RES is transmitted in PS through high voltage switch-gears (SGs) while DC is power supplied from PS through low voltage, medium voltage and high voltage SG-s. For the purpose of realisation of such facility, it is necessary to enable adequate conditions related to geographical location, physical access to the facility, possibility of connecting to the PS and possibility of connecting to the telecommunications centres. Based on carried out researches related to RESs potential, available roads, power supply infrastructure and telecommunication infrastructure, development conditions for DC on location near to Belgrade, close to power transformer station „Belgrade 20“ are analysed in this paper. From the aspect of DC power supply, proposed solution includes wind farm, solar plant and landfill gas power plant, as well as related SGs. Telecommunication connections from DC to the PS and other important telecommunication centres are provided. These connections are realised through optical cables placed next to the electrical lines and cables, and, when that is not possible, placed independently in the ground. The design of the DC interior is given and calculations of the required electrical energy for the power supply of the equipment and devices in the facility are performed. Based on calculation results, capacity calculation of the RES and calculation of SGs are performed. Design of the interior optical connections inside DC is also given. A General assessment of the investment and economics of building such DC are given at the end of the paper.

Da li nam treba više ambicije za tranziciju na obnovlјive izvore u Srbiji? Temelјi upravlјanja i planiranja energije

Renewable energy has been suggested as the primary approach for decarbonizing the energy system and decoupling energy consumption from greenhouse gas emissions, both in the energy literature and in practice. The European Union has acknowledged the challenge and put renewable energy transition high on the policy agenda with the latest ambition of being a carbon-neutral economy by 2050. On the other hand, Western Balkan countries are still dependent on fossil fuels as one of their primary energy mix sources. The pledge about the European future has mostly driven the renewable energy transition ambition in the Western Balkan countries, including Serbia. Moreover, signing the Energy Community Treaty provided institutional and legal tools to both Contracting Parties and the European Union to build the common energy market. These processes inspired many authors in the last two decades to analyse technical, economic, market and environmental aspects of renewables. However, the governance and planning, even though identified as challenging, have been side-lined from the analysis. This paper aims to overview the selected renewable energy transition literature and legislation to analyse the main legal and policy milestones reached so far, as well as ambition in Serbia. It also discusses the lessons learned from the related literature from energy governance and planning prism. To do so, it firstly provides a literature review of the main concepts of the renewable energy transition. Moreover, the historical analysis of renewable energy policy and legal developments in the European Union, the Energy Community and Serbia are in the second part's focus. Finally, the discussion part summarizes lessons learned from the literature for future energy governance and planning with the perspective of the energy planning process, policy evaluation, and education and administrative capacity. The article concludes by emphasizing the importance of taking the current literature findings as prospective steps to follow towards accelerated energy governance and planning.

Оdrеđivаnjе brzinе struјаnjа vаzduhа u prаvоugаоnоm zаtvоrеnоm cevovodu korišćenjem metoda polja brzina

In the technical practice, it is often necessary to measure or control the fluid flow rate in pipelines and channels. The velocity-area method requires a number of meters located at specified points in a suitable cross-section of closed conduits. Simultaneous measurements of local mean velocity with the meters are integrated over the gauging section to provide the discharge. In this paper, three approaches of this method are applied on a rectangular closed conduit to determine the air flow rate with integration techniques used to compute the discharge assume velocity distributions that closely approximate known laws, especially in the neighborhood of solid boundaries. For this purpose, meters for velocity were 7 Pitot tubes placed vertically in predefined measurement points covering the conduit height, and moved horizontally along the conduit width. The position of the Pitot tubes along the conduit width was monitored and controlled by a linear displacement transducer. Pressure is measured using digital sensors. The first technique for determination of air flow rate is on basis of fixed (stopping) measuring points across the conduit width as averaged values of local velocity, the second one is semi continual measurement of velocity profile by applying interpolation between the average local velocity on fixed (stopping) points and measured velocity in the movement between two positions, and the third is by continuously moving the Pitot tubes without stopping. The results of the three techniques are calculated and presented using different types of software. Considering the last technique, comparison of results is made applying different movement speeds of the Pitot tubes in order to examine their influence on the velocity profile.

Analiza vremena ispitivanja i greške očitavanja pametnih brojila električne energije u zavisnosti od njihovog podešenja

The time of checking the registers of smart meters of accuracy class 0.2 S for indirect measurement of active electricity via instrument transformers, during the first, extraordinary or periodic control and verification has been significantly increased according to the latest Rules on meters of active electrical energy of accuracy class 0.2 S from December 23, 2016. This is especially pronounced when the meter is set to show the measured value of electrical energy in kWh on the secondary side of instrument transformers with the often used meter of active electrical energy of accuracy class 0.2 S, rated phase voltage 110 / √3 V and for the rated current 1 A. In that way, the total time as well as the costs of testing such meters has increased a lot. In addition, with electricity meters set in this way with a resolution of three decimal places and a unit in kWh, there is an additional error when reading the measured value of active electrical energy and especially when calculating the energy loss of active electrical energy. A more acceptable approach to setting such meters will be considered.