Abstract: The study considers the construction of a battery system within the existing wind farm connected to the transmission grid, which will enable the provision of a balancing service to HOPS in the form of offering aFRR power reserve in the amount of a minimum of 1 MW with the activation of balancing energy at their request. Through the developed optimization model, it is necessary to find the optimal combination of electricity sales on the day-ahead market and the regulated balancing energy market. Also, with regard to the estimated overall costs of the battery system and the optimal combined performance on the balancing energy market and the day-ahead market, it is necessary to find the optimal size of the battery that needs to be installed with the mentioned wind farm, which will ensure the fastest return on investment.
Abstract: In this study, a proposal for the development of the distribution network is provided based on the current state and projected growth of consumption in the considered area. The development plan is based on a detailed model of the HV (High Voltage) power grid and includes detailed development guidelines for five-year periods. A forecast for the increase in consumption based on historical trends and plans for the implementation of new major consumer facilities has been prepared for the distribution network. As part of the distribution network development plans, approximate costs for the implementation of various development options are provided. An analysis of the dynamics of transitioning certain distribution units (distribution substations and offices) to a 20 kV operating voltage has been conducted using the Analytic Hierarchy Process.
Abstract: As part of the study, different variants of electrolyzer plant construction with standard fixed typical nominal powers and electrolyzer plant powers that were optimized using a developed optimization model were considered, which simultaneously takes into account the increase in investment costs and the increase in income from the provision of mFRR auxiliary services, i.e. the reduction of operating costs in the part of electricity procurement of energy in the event of an increase in the rated power of the plant. Based on the results of the optimization model, an analysis of the profitability of the investment in the electrolysis plant was performed, and the levelized cost of green hydrogen production was calculated, taking into account the detailed investment and operating costs.
Abstract: Testing the electrical conductivity of clay from a site near Tomislavgrad for the purpose of implementing a grounding system
Abstract: The paper deals in detail with the selection of optimal technical characteristics of new block transformers for the Kraljevac HPP that should have on-load voltage regulation. The requirements of the transmission network (specific local conditions) are considered, as well as the limitations of the existing (very old) generators. Namely, the optimal choice of, among other things, the transmission ratio, short-circuit voltage and the scope (and method) of on-load voltage regulation of the block transformer must reconcile the requirements of the network with the available generator capabilities (which are partly contradictory). The requirements of the transmission network are considered in detail, from the aspect of voltage conditions (including expected temporary overvoltages), power flows, short-circuit currents, etc. The existing generator limitations are also analyzed, from the aspect of the operating map, voltage regulation, excitation limiter settings, etc. All three different types of transformer voltage regulation (CVFF, VFVV and CbVV) are analyzed through various unfavorable expected operating scenarios. The selection of the following technical characteristics of the block transformer is examined in detail, among other things: rated power, short-circuit voltage, rated voltages and rated winding currents, rated transmission ratio, voltage regulation range (step and number of tap positions), type of voltage regulation, allowed overexcitation, cooling requirements, allowed losses, etc. Finally, the paper also calculates and selects the technical parameters of the current transformer in the star point of the HV winding of the observed block transformer.
Abstract: The paper deals with the problem of calculating and selecting the parameters for setting the protection functions of the electrical protection system of the generator D - transformer block =TD in the Zakučac HPP. The backbone of the generator and transformer block relay protection system consists of two numerical relay devices type REG670 (ABB), together with two additional numerical relay devices type 7UT613 (Siemens), which serve to protect the transformer on the generator branch. The following protection functions, among others, have been analyzed in detail: differential protection of the generator and the generator-transformer block: ground fault protection of the stator and rotor: underimpedance protection: overcurrent and overcurrent-undervoltage protection: protection of the stationary aggregate: protection when connecting turns of the same stator phase: protection against stator overload, excessive magnetic induction, asymmetrical load and reverse power: protection against loss of excitation and loss of synchronism: overvoltage and undervoltage protection: frequency protection.
Abstract: The paper deals with the problem of calculating and selecting the parameters for setting the protection functions of the electrical protection system generator - block transformer in the Krčić SHPP. The following protection functions, among others, were analyzed in detail: overcurrent protection in two stages of operation: overvoltage and undervoltage protection in two stages of operation: overfrequency and underfrequency protection in two stages of operation: protection against reverse power, overload, asymmetric load and generator runaway. Several different monitoring functions of the generator were also analyzed. The calculation of the expected generator short circuit, the calculation of temporary overvoltages on the generator (sudden load loss) and other related analyses were made.
Abstract: The paper presents a detailed calculation and selection of parameters for metal oxide surge arresters in a distribution network grounded using a Petersen choke. The selection of surge arresters was carried out for arresters connected between phase and ground (grounding conductors) and for a surge arrester connected in the star point of the power transformer (zero point of the network) TS 110/20(10) kV Imotski (parallel to the Petersen choke). The expected voltage stresses were considered, of which the following types of temporary overvoltages can be mentioned: 1. overvoltages caused by sudden load failure, 2. overvoltages caused by switching on unloaded cable lines, 3. overvoltages caused by the occurrence of short circuits with the ground, 4. overvoltages caused by resonant effects, 5. overvoltages caused by saturation of the power transformer, 6. overvoltages transmitted by capacitive coupling through the power transformer: In addition, since the incident network of 20(10) kV is grounded using a compensating (Petersen) choke, the following (over)voltage conditions were considered: 7. increase in the voltage of the zero-point network due to the asymmetry of the domicile distribution network, 8. increase in the voltage of the zero-point network due to the disconnection or interruption of one phase on one of the cable lines of the domicile distribution network, 9. increase in the voltage of the zero-point network due to the design of the power transformer, when ground faults occur in the incident transmission network. The following maximum expected (switching and atmospheric) overvoltages were also analyzed: overvoltages that occur when switching on the incident cable lines, overvoltages that occur when a short circuit occurs and is disconnected, overvoltages that are transmitted through the power transformer from the incident transmission network. The energy stress of the aforementioned metal oxide surge arresters was also considered.
Abstract: As part of this study, a software package was developed and an appropriate procedure for evaluating the energy potential of hydropower projects was defined, which determines the basic energy-technical characteristics of an individual project. An appropriate budget and calculation model was elaborated in order to analyze the potential of hydropower projects. The purpose is to develop a method for calculating the installed power and possible electricity production of hydroelectric power plants at a particular location, which can thus serve as a support in investment decision-making for hydroelectric power plant construction projects, regardless of whether it was a preliminary analysis of the potential of a potential location or a check of an already designed project solution .
Abstract: In this study, a proposal for the development of the distribution network is given based on the current situation and the forecasted growth of consumption in the considered area. The development plan is based on a detailed model of the MV power network and contains detailed development guidelines for five-year periods. For the distribution network, a forecast of the increase in consumption was made based on historical trends and plans for the realization of new larger consumer facilities. As part of the development plans for the distribution network, the approximate costs of the realization of certain variants of development are also given. Based on the analytical-hierarchical method, an analysis of the dynamics of the transition to 20 kV operating voltage of certain distribution units (distribution plants and offices) was performed.
Abstract: The paper presents theoretical foundations and calculations on which the selection of parameters of the relay protection system of the 220 kV plant and the 220 kV incident transmission lines in the Zakučac HPP is based. The concept of the relay protection system is based on the application of two numerical relay devices on each of the incident lines, with the implementation of the following protection functions: longitudinal differential protection, distance protection with polygonal operating characteristic and communication scheme of operation, directional earth fault protection with communication scheme of operation, backup overcurrent protection, protection against switching on to a fault. Automatic reconnection of the lines is envisaged. The relay protection of the 220 kV plant’s busbars is based on the differential principle and also includes the function of protection against circuit breaker failure. Additional backup overcurrent protection is located in the connection field of the 220 kV plant in the Zakučac HPP. The paper presents the necessary analyses and the calculation and selection of parameters of all the mentioned protection functions of all the numerical relay devices that make up the described relay protection system.
Abstract: The paper deals in detail with the calculation and selection of settings for the numerical relay device type 7UM6225 from Siemens for the relay protection of the synchronous generator and its associated block transformer at the Prančevići SHPP. The following protection functions of the numerical relay device were activated and set: (1) differential protection of the generator and block transformer, (2) overcurrent protection with undervoltage hold, (3) underimpedance protection, (4) overvoltage protection, (5) undervoltage protection, (6) instantaneous overcurrent protection, (7) 90% stator earth fault protection in two variants: (a) overvoltage earth fault protection connected to the open delta of the voltage measuring transformer winding at the generator terminals and (b) overcurrent earth fault protection connected to the current transformer on the secondary of the earthing transformer, (8) 100% stator earth fault protection (overvoltage protection with third harmonic measurement), (9) rotor earth fault protection, (10) protection against unsymmetrical load, (11) thermal protection, (12) reverse power protection, (13) protection against loss of excitation, (14) protection against excessive magnetic induction, (15) frequency protection (overfrequency and underfrequency), (16) protection of the stationary generator and (17) protection against circuit breaker failure. When calculating the settings of the protection functions, care was taken to optimally satisfy the following basic criteria: the fastest possible fault tripping, selective action, the highest possible sensitivity and reserve protection to the greatest extent possible.
Abstract: The paper presents a detailed analysis and accompanying calculation based on which the equipment for grounding the star point of the synchronous generator at the Prančevići SHPP was dimensioned. It is a (single-phase) transformer for grounding the star point of the generator stator winding (which has a block transformer) with an associated resistor on its secondary. A current transformer in the secondary winding of the transformer for grounding intended for the connection of the 90% ground fault protection of the generator stator was also dimensioned. When selecting the equipment for grounding the generator, care was taken to optimally satisfy the following criteria: (i) the ground fault current at the generator voltage level must be limited to the value prescribed by the generator manufacturer (amount and duration), (ii) internal overvoltages at the generator voltage level must be lower than the withstand voltages of the insulation, (iii) the sensitivity of the 90% ground fault protection of the generator should be as high as possible.
Abstract: The paper deals in detail with the issue of optimal overvoltage protection of new 110 kV cables in the Senj HPP, which connect the block transformer to the external switchgear. The expected: (a) temporary overvoltages (due to the occurrence of ground faults and their elimination, due to sudden generator load shedding and sudden load shedding in the plant) were analyzed: (b) switching overvoltages and (c) atmospheric overvoltages. The selection procedure for metal-oxide surge arresters was carried out, as well as numerical simulation of their operation due to the occurrence of expected unfavorable overvoltage situations. All numerical simulations were carried out in the EMTP-ATP software package with detailed models of all components of the observed system. Insulation coordination with the selected surge arresters was also carried out. Finally, a recommendation was given for the optimal treatment of the screen of the new 110 kV cable line, especially considering that it is a cable located in the tunnel through which the block transformer is connected to the external switchgear.
Abstract: The paper deals with the problem of calculating and selecting the parameters for setting the protection functions of the electrical protection system generator C - block transformer =TC in the Zakučac HPP. The backbone of the relay protection system of the generator and block transformer consists of two numerical relay devices type REG670 (ABB), together with two additional numerical relay devices type 7UT613 (Siemens), which serve to protect the transformer on the generator branch. The following protection functions, among others, have been analyzed in detail: differential protection of the generator and the block generator - transformer: ground fault protection of the stator and rotor: underimpedance protection: overcurrent and overcurrent-undervoltage protection: protection of the stationary aggregate: protection when connecting turns of the same stator phase: protection against stator overload, excessive magnetic induction, asymmetrical load and reverse power: protection against loss of excitation and loss of synchronism: overvoltage and undervoltage protection: frequency protection.
Abstract: The paper deals with the problem of calculating and selecting the parameters for setting the protection functions of the electrical protection system generator B - transformer block =TB in the Zakučac HPP. The backbone of the generator and transformer block relay protection system consists of two numerical relay devices type REG670 (ABB), together with two additional numerical relay devices type 7UT613 (Siemens), which serve to protect the transformer on the generator branch. The following protection functions, among others, have been analyzed in detail: differential protection of the generator and the generator-transformer block: ground fault protection of the stator and rotor: underimpedance protection: overcurrent and overcurrent-undervoltage protection: protection of the stationary aggregate: protection when connecting turns of the same stator phase: protection against stator overload, excessive magnetic induction, asymmetrical load and reverse power: protection against loss of excitation and loss of synchronism: overvoltage and undervoltage protection: frequency protection.
Abstract: Report on the energy inspection of the residential building for the purpose of creating an energy certificate
Abstract: Elaborate on the energy inspection of a residential building for the purpose of creating an energy certificate
Abstract: As part of the technical-environmental in-depth survey, in addition to the analysis of the previous ones, a new wind study and a long-term production assessment were made using the provided measurement data for configurations with five different types of wind turbines. Next, the technical aspects of possible variants of wind turbines were analyzed, as well as project solutions, studies, contracts, permits and other documentation submitted by the project owner, which were prepared and implemented in the development of the Lukovac HPP project so far. In accordance with the project task, an assessment of all future costs of the preparation, construction and operation of the wind power plant was made, as well as a recommendation for the assessment of future income as a technical basis for assessing the value of the project. Identification and assessment of key risks was also made, presented at the end in tabular form according to the structure defined by the Client.
Abstract: As part of this study, the energy-economic analysis of the construction of the Peruca HPP was updated, where as part of it: a) The change in the operation regime of the Peruca HPP and the way of using the Peruca reservoir is analyzed with regard to work with new aggregates. b) The expected annual production of MHE Peruca is calculated with the revised engagement regime in such a way that the water from the reservoirs is used in the most efficient way. c) The costs of investment and operation of MHP Peruca are updated, taking into account the available documentation of the main project, the expected obligations of MHP Peruca based on valid regulations and the current conditions of procurement of equipment and works. d) The economic value of the electricity produced at the Peruca HPP is determined with regard to the existing incentive system.
Abstract: The study examines and selects the method of connecting the Tovarnik wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The paper presents the calculation and, based on it, the choice of technical parameters of current and voltage (combined) measuring transformers in the HV fields of block transformers =E3, =E5, =D8 and =D10 in HE Zakučac.
Abstract: In this study, a proposal for the development of the distribution network is given based on the current situation and the forecasted growth of consumption in the considered area. The development plan is based on a detailed model of the MV power network and contains detailed development guidelines for five-year periods. For the distribution network, a forecast of the increase in consumption was made based on historical trends and plans for the realization of new larger consumer facilities. As part of the development plans for the distribution network, the approximate costs of the realization of certain variants of development are also given. Based on the analytical-hierarchical method, an analysis of the dynamics of the transition to 20 kV operating voltage of certain distribution units (distribution plants and offices) was performed.
Abstract: Report on the energy audit of the HEP OPS PrP Split administrative building
Abstract: Energy audit report for the aparthotel Tamaris
Abstract: The paper presents the theoretical foundations and calculations on which the selection of the parameters of the relay protection system of the 110 kV plant and the 110 kV incident transmission lines in the Zakučac HPP is based. The relay protection system is implemented using numerical relay devices type 7SD522 (longitudinal differential and distance protection of incident lines) and 7SS52 (differential protection of busbars) from Siemens. The following basic concept of the relay protection system is applied: longitudinal differential protection, distance protection, APU line function, directional earth fault protection, backup overcurrent protection, circuit breaker failure. Distance and directional earth fault protection also use appropriate communication schemes of operation. The plant buses are protected by dedicated busbar differential protection. The paper presents the necessary analyses and the calculation and selection of parameters of all the mentioned protection functions of the numerical relay devices that make up the mentioned relay protection system.
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: In this study, a proposal for the development of the distribution network is given based on the current situation and the forecasted growth of consumption in the considered area. The development plan is based on a detailed model of the MV power network and contains detailed development guidelines for five-year periods. For the distribution network, a forecast of the increase in consumption was made based on historical trends and plans for the realization of new larger consumer facilities. As part of the development plans for the distribution network, the approximate costs of the realization of certain variants of development are also given. Based on the analytical-hierarchical method, an analysis of the dynamics of the transition to 20 kV operating voltage of certain distribution units (distribution plants and offices) was performed.
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: Report on the energy audit of the Brodomerkur administrative building
Abstract: The study examines and selects the method of connecting the Otrić wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The study examines and selects the method of connecting the Čućin wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The study deals with and selects the method of connecting the wind power plant ST3-1/2 Visoka Zelovo to the 110 kV transmission network or the 30 kV distribution network, and examines power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: This study deals with the issue of entering into operation TS 220/110/35/20(10) kV Plat and the associated connection lines 220, 110, 35 and 20(10) kV, which connect the TS in question to the transmission and distribution network. TS Plat is a complex building where the process of transforming electricity into four voltage levels takes place. For this reason, it is necessary to plan the entry into operation of TS Plat in an optimal way, with as little unavailability as possible in the first line of the transmission network, the building in question assumed the position of the most significant power facility in the wider Dubrovnik area.
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: The study deals with and selects the method of connecting the Boraja II wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: Based on the existing Grid Codes of the Electricity System and the practice of other countries, the paper presents a proposal for the structure of the new Grid Codes of the Transmission System. It also presents the basic requirements of the Grid Codes of the Transmission System and the accompanying regulations according to the draft proposal of the new Electricity Market Act, with a special emphasis on the part related to the adoption, monitoring, interpretation and amendment of the same.
Abstract: The paper deals in detail with the problem of calculating and selecting the parameters for setting the protection functions of the electrical protection system of the generator-transformer block in the Zakučac HPP. The backbone of the generator and transformer block relay protection system consists of two numerical relay devices type REG670, together with two additional numerical relay devices type 7UT613, which serve to protect the transformer on the generator branch. The following protection functions, among others, have been analyzed in detail: differential protection of the generator and the generator-transformer block: ground fault protection of the stator and rotor: underimpedance protection: overcurrent and overcurrent-undervoltage protection: protection of the stationary aggregate: protection when connecting turns of the same stator phase: protection against stator overload, excessive magnetic induction, asymmetrical load and reverse power: protection against loss of excitation and loss of synchronism: overvoltage and undervoltage protection: frequency protection.
Abstract: The paper deals in detail with the problem of calculating and selecting the settings of the electrical (relay) protection system of 0.4 kV self-consumption in the Zakučac HPP, under the conditions of different possible operating modes. This is a relatively complex multi-level system, consisting of a large number of asynchronous motors of different powers, which can be powered from a 35/0.4 kV domestic transformer, from domestic generators (KG1, KG2) as well as from the tap of each of the four main generators. The paper shows that an electrical protection system has been created that will be selective during different operating modes and will also be sufficiently sensitive with respect to the expected short-circuit currents.
Abstract: The study examines and selects the method of connecting the Orljak wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: As part of this study, the following was given: - basic analysis of the application of a series choke on DV 110 kV Meterize-Vrboran in order to equalize the power flows of the mentioned transmission line and eliminate its overloading. - Analysis of power flows in characteristic situations in the network and selection of the basic technical parameters of the series ballast. - Review of alternative solutions. - Analysis of transient phenomena during connection/disconnection of DV 110 kV on which the ballast will be installed.
Abstract: The study deals with and selects the method of connecting the Crno Brdo wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The paper presents the calculations and selection of parameters of current and voltage transformers of the generator voltage level of the new generators for HE Zakučac. When selecting the protective cores of the associated current transformers, due to the proximity of the generator itself, analyzes of their dynamic behavior in the event of a three-pole short circuit were performed. In this sense, the necessary data on the oversizing coefficient, the resistance of the secondary winding and the saturation voltage of the current transformers were defined, among other things.
Abstract: The purpose of this report is to review the basic variants of the construction and connection of the new TS 110/x Zamošće. The construction of TS 110/x kV Zamošće was initiated by a request for the connection of a new customer (Bili dvori Tourist Village, 2.2 MW). The additional burden of the transformation in TS 35/10 kV Zamošće leads to the limit load of the same and endangering the already bad voltage conditions.
Abstract: The paper develops a mathematical model for the analysis of electromagnetic effects of close triples of generator shielded lines. The model in question takes into account the complex electromagnetic coupling between triples of single-pole insulated shielded generator lines (of circular cross-section). The influence of proximity and skin effect are also taken into account. The influence of mutual short-circuiting of the shields of each triple of shielded lines and their grounding (at only one or both ends) on the distribution of the associated currents (eddy and/or circular currents) in the shields as well as the occurrence of shield voltages towards the ground/earthing conductor was analyzed. The associated power losses of the shielded lines were also calculated, as well as the accompanying current and voltage states that occur in a short circuit. The most favorable method of treating the shield (grounding and short-circuiting) was defined with respect to power losses and expected shield voltages towards the ground/earthing conductor.
Abstract: Due to the accessibility of bentonite and its relatively good properties, bentonite grounding mat is most often used in our region to improve the characteristics of grounding conductors in poorly conductive environments, especially dynamic characteristics (atmospheric discharges, etc.). Bentonite is a volcanic clay, containing minerals (Al2O3, Fe2O3, MgO, CaO, Na2O, K2O) that form electrolytic conductors with water. Bentonite does not leach out of the soil, so the mat does not need to be renewed. However, bentonite is also an electrolytic conductor, so it requires a certain level of moisture. Completely dry bentonite clay has a very high electrical resistance (significantly higher than 1000 Ωm). Since bentonite clay is very hygroscopic, in normal climatic conditions it is possible to expect good conductivity of the mat without special maintenance. However, it is important to know that the salt conglomerate in bentonite and their relative share is not firmly determined, so the conductivity of bentonite from different deposits can vary. Therefore, it is good to determine the characteristics of the specific material by measuring. By adding water in a ratio of 1:1, the resistance of bentonite decreases by about three orders of magnitude. With further addition of water, its resistance increases insignificantly. Unlike metal conductors, the temperature coefficient of wet bentonite is negative, but the change in resistance in the range of 4°C to 40°C is not radical (it changes in the range of 3.6 m – 2.2 m). It was further observed that by drying bentonite mud, its density increases significantly, its plasticity decreases, but its electrical resistance does not increase radically as a result. It is also observed that the dried sample retains its hygroscopic properties. Based on all of the above, it can be concluded that wet bentonite is a suitable material for the bedding of grounding conductors.
Abstract: The paper presents a computer analysis based on which the specific overvoltage protection of new generators in the Zakučac HPP was then selected. This involves the selection of parameters for metal-oxide surge arresters (without spark gaps) at the generator voltage level in the Zakučac HPP. The selection was made based on the analysis and calculation of expected overvoltage conditions at the generator voltage level (expected temporary, switching and atmospheric overvoltages), after which a computer check of the operation of the selected surge arresters was carried out.
Abstract: In the paper, the calculation and selection of technical data of current transformers on the tertiary of the network transformer 150 MVA (autotransformer 220/110 kV with stabilizing tertiary winding connected in a closed triangle) in HE Zakučac was carried out. We are talking about two current transformers for protection, one of which is installed in the tertiary winding itself (outside the boiler), while the other current transformer is installed in the short-circuit connection of the tertiary winding with the ground / grounding. Namely, for the purpose of fixing the potential of the tertiary winding (in a triangle connection), it is (directly) grounded at one of its points.
Abstract: The paper presents a computer analysis based on which the appropriate value of the high-voltage high-ohmic active resistor for grounding new generators in the Zakučac HPP was selected. The resistor in question is installed between the star point of the generator stator winding and the earth / grounding conductor. The following three basic criteria are met: a) limiting the generator ground fault current to a value that is not dangerous for its stator winding, b) limiting internal overvoltages at the generator voltage level to values that are not dangerous for the generator itself and associated equipment, c) ensuring the highest possible sensitivity of the 95% ground fault protection of the generator stator winding.
Abstract: The paper describes the calculation and selection of parameters of the relay protection system of the network transformer 220/110 kV, 150 MVA in HE Zakučac. It is an autotransformer with a stabilizing tertiary winding. The protection functions used include: three-point differential protection, REF protection, overcurrent protection, overvoltage protection, thermal protection and protection against excessive magnetic induction of the transformer. They are implemented using sophisticated numerical relay devices from ABB and Siemens.
Abstract: The study examines and selects the method of connecting the Kozjak wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: In this paper, a large number of issues are analyzed and concrete proposals are given related to the definition of technical conditions, the regulatory basis, the method of determining the costs and prices of auxiliary services, the technical capabilities of network users in terms of the possibility of delivering auxiliary services (including measurement and quality control), the possibility of forming markets for certain auxiliary services, and the contracting model for them. In addition, the necessary changes to the by-laws necessary for the implementation of the aforementioned proposals are proposed, whereby the primary consideration is the combined model of binding auxiliary services (which are not paid for) and auxiliary services that will be paid for at a regulated price, but clearly stated so that in the provision of auxiliary services can also include new producers.
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: The study deals with and selects the method of connecting the Opor wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The subject of this study is the calculation of the short circuit of the Jelinak wind power plant for the planned condition of the connection and the surrounding power grid. The short-circuit calculation was performed primarily for the purposes of dimensioning the primary equipment of the connecting TS 12/110 kV Jelinak and for the purposes of adjusting the relay protection system of the Jelinak wind power plant.
Abstract: As part of this study, the technical and energy requirements that the wind power plant must fulfill in order to obtain approval for connection to the grid are given. As part of the study, an analysis of the existing/planned state of the transmission/distribution network was performed, and proposals were made for connection to the network, as well as requirements related to the creation of conditions in the network necessary for the realization of the connection according to the proposed variant. The technical solution for connecting to the network is based on the application of standard solutions and equipment in accordance with the applicable legal and technical regulations. For the proposed connection solution that technically meets the conditions in the network, an estimate of the costs of connecting to the network and creating technical conditions in the network is given.
Abstract: The study deals with and selects the method of connecting the Čemernica wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The paper presents an analysis of the overvoltage protection of the Jelinak wind farm, including the associated 12 kV cable network, and the associated Jelinak substation. Appropriate metal oxide surge arresters are selected, and their operation is numerically verified in the event of the occurrence of unfavorable expected overvoltage conditions. The insulation coordination of the observed wind farm system and Jelinak substation is also carried out.
Abstract: The paper presents the calculation and selection of parameters for current and voltage measuring transformers for the 110 kV plant at TS Jelinak. It also presents a proposal for the selection of numerical relay devices, including the associated relay protection functions, for the protection of TS Jelinak and the incident transmission network.
Abstract: By elaborating on the optimal technical solution for increasing the connected HE Zakučac on the existing connection, we want to determine the technical conditions that will enable the acceptance of the increase in the connected power of HE Zakučac: -
Abstract: The study deals with and selects the method of connecting the Visoka wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: In this study, a proposal for the development of the distribution network is given based on the current situation and the forecasted growth of consumption in the considered area. The development plan is based on a detailed model of the MV power network and contains detailed development guidelines for five-year periods. For the distribution network, a forecast of the increase in consumption was made based on historical trends and plans for the realization of new larger consumer facilities. As part of the development plans for the distribution network, the approximate costs of the realization of certain variants of development are also given. Based on the analytical-hierarchical method, an analysis of the dynamics of the transition to 20 kV operating voltage of certain distribution units (distribution plants and offices) was performed.
Abstract: The paper presents analyses and numerical calculations of overvoltage conditions of the Crno Brdo wind farm system. This study also selects specific metal oxide surge arresters for effective overvoltage protection of the Crno Brdo wind farm system (wind turbine with associated transformer and cable network), and then numerically analyzes their operation in situations of expected adverse overvoltage conditions, with special emphasis on the so-called back-surge overvoltage, which is the result of a direct lightning strike to the wind turbine.
Abstract: All essential characteristics of the earthing conductor (distribution resistance, potential gradients, applied potential, etc.) directly depend on the specific resistance (resistivity) of the soil. Unlike technical conductors that can be considered essentially homogeneous and their resistance can be read quite precisely from technical manuals, geological environments are electrically much more complex and mostly, microscopically and macroscopically, inhomogeneous, and thus their resistance cannot be estimated even within an order of magnitude (tables and graphs in manuals). It is necessary to determine the soil resistance by direct measurements at the very place where the earthing conductor is installed. The transmission capacity and lifespan of power cables, and thus the quality and reliability of the power supply to consumers, directly depend on the ability of the environment to dissipate the heat that develops due to Joule and dielectric losses in the cable. The excess temperature of an underground power cable is proportional to the specific thermal resistance of the environment in which the cable is laid. For common geological environments, thermal resistance ranges from 40 Kcm/W to 400 Kcm/W, and cannot be estimated accurately enough for cable sizing without direct on-site measurements.
Abstract: For the design of large wind farms, high-quality design data is necessary. The electrical resistance of the soil is used to calculate the grounding of individual poles and the entire wind farm together with the substation. The thermal resistance of the soil is necessary to calculate the load capacity of the cables in the cable trench, of which there can be many in the vicinity of the substation. Therefore, special attention is paid to measuring the thermal resistance of the soil at the location and in the vicinity of the future substation.
Abstract: In the study, a preliminary analysis of the justification of the construction of the Mikanovci wind farm and the connection to the power grid was carried out with techno-economic data and spatial planning data in order to obtain a preliminary approval for the construction of the production facility.
Abstract: In the study, a preliminary analysis of the justification for the construction of a hydropower plant owned by the company EHN d.o.o. was carried out with a proposal for connection to the electric power network and defined techno-economic data and spatial planning data with the aim of obtaining prior approval for the construction of a production facility.
Abstract: Grid connection options and risks for WF Bradarica kosa and WF Kocinje brdo
Abstract: The study examines and selects the method of connecting the Ljubač wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The paper presents the analysis and calculation of relay protection parameter settings in the 110/10(20) kV Srđ substation.
Abstract: The study conducted a detailed analysis of the electromagnetic compatibility of the 110/20(10) kV Srđ substation. A numerical simulation of the occurrence of internal and external VFTO overvoltages in the GIS plant of the aforementioned substation was also conducted. Among other things, recommendations were given for the correct / favorable implementation of (mutual) connection and grounding of the armor of the GIS plant parts. The electromagnetic impact of the associated 110 kV cable lines (in the cable tunnel of the substation) on the associated telecommunication lines was also analyzed.
Abstract: The subject of the elaboration is the assessment of the possibility of connection to the power grid of the Stankovci solar power plant planned in the area of the economic zone in the settlement of Stankovci (Zadar County), and the proposal of a phased connection solution.
Abstract: The study provides detailed analyses and appropriate calculations on which the proposal for selecting the grounding method for the MV network star point and 10(20) kV distribution board supplied from the 110/10(20) kV Srđ substation is based. The aforementioned proposal for selecting the grounding method is given for the so-called transitional and final operating regime of the associated 10(20) kV network supplied from the 110/10(20) kV Srđ substation.
Abstract: The study deals with and selects the method of connecting the Krš Pađene wind power plant to the transmission grid, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission grid and variants N-1
Abstract: In this study, the influence of the 60 MVA electric arc furnace, which is planned to be installed in the CMC Sisak steel plant, on the voltage quality on the 110 kV busbars of TS Željezara was analyzed based on two standard quality indicators, harmonic distortion and voltage flicker. In order to compare the results of the analysis with the limitations defined by the corresponding international norms, the study first provides an overview of these norms. This is followed by a presentation and analysis of the results of measurements carried out on the primary side of the transformer in TS Željezara, through which it is planned to power a new electric arc furnace, and today a 12.5 MVA furnace is powered through it. In the fourth chapter, an analysis of the impact of the new electric arc furnace on voltage quality is given, considering harmonic distortion and flickering of the voltage at the connection point. This analysis, in addition to the already mentioned measurements of the current values of the electric arc furnace in the Split ironworks, is based on data on the substitute reactance of the network at the connection point for characteristic operating conditions. The values of these reactances are determined from data on short-circuit currents obtained from the Transmission System Operator. The analysis was carried out using the Matlab software package, whether existing program routines were used or new programs were developed for some specific processing, such as the determination of time-varying harmonics or flicker calculation.
Abstract: The paper presents an analysis and associated numerical calculations of the electromagnetic impact of the 110 kV cable connection TS 110/20(10) kV Dugopolje on nearby telecommunications lines.
Abstract: The subject of the elaboration is the assessment of the possibility of connection to the power grid of the Stankovci solar power plant planned in the area of the economic zone in the settlement of Stankovci (Zadar County), and the proposal of a phased connection solution.
Abstract: An important prerequisite for the correct and economical dimensioning of the earth electrode is knowledge of the geoelectric properties of the soil in which the earth electrode is installed. Unlike technical conductors, which can be considered essentially homogeneous, their resistance can be read quite precisely from technical manuals, so it is necessary to determine the soil resistance by direct measurements at the very location of the earth electrode installation. However, due to the inhomogeneity of the soil, one measurement is never enough. On the ‘Pehlin-Turnjić’ cable route, 6 pairs of sounding curves (a total of 12 curves) were recorded, approximately evenly distributed along the route. The measurements were performed using the vertical electrical sounding (VES) method with the Schlumberger probe arrangement, with overlapping. The interpretation of the sounding curves was performed using the least squares method with the use of a computer, using the Hook-Jewees numerical method.
Abstract: As part of the study, the basic variants of the introduction of DV 2x110 kV Trogir - Podi into TS Trogir were processed, for the foreseeable year of entry into operation of the DV 2x110 kV in question (2013) and the nominal year 2020. In doing so, the existing plans for the development of the surrounding influential transmission network and the currently foreseeable scope of construction of potential new facilities were taken into account. Also, an analysis was performed and a proposal was made for a possible option for the reconstruction of the 110 kV network from TS Podi to TS Bilica, and the fitting of a new DV 110 kV (south route) Trogir-Marina-Rogoznica-Podi/Ražine/Bilice.
Abstract: The aim of this study is to assess the existing portfolio of wind power projects developed by companies on the domestic market from the perspective of: •
Abstract: The main goal of the study is to define a proposal for the long-term development of the transmission network in the Zadar area with a special emphasis on the preferred solution of a reliable 400/110 kV transformation that will enable the safe supply of the surrounding TS 110/x kV. The accepted version of the solution for the long-term development of the transmission network in the Zadar area will be the basis for supplementing the spatial planning documentation, detailed design work and defining the plan for the construction of the proposed facilities, reconstruction of existing and construction of new TS 110/x kV, and reconstruction of existing and construction of new DV 110 kV .
Abstract: The study examines and selects the method of connecting the Ponikva wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The study deals with and selects the method of connecting the Čemernica, Visoka, Opor and Perun wind farms to the 110 kV transmission network or the 30 kV distribution network.
Abstract: The aim of this study is to assess the existing portfolio of wind power projects developed by companies on the domestic market from the perspective of: •
Abstract: Considering the complexity of the Zakučac HPP revitalization process and its importance in the EES of Croatia, adjustments and upgrades of the surrounding transmission network must be coordinated in stages, and all necessary operations prepared and carried out in a timely manner. For this reason, this report investigated and proposed a plan for the construction of the surrounding transmission network, and defined the priorities and phasing of the construction, taking into account the variant of connecting all four aggregates of HPP Zakučac to the 220 kV busbars.
Abstract: In the study, a preliminary analysis of the justification of the construction of the Orlovac 1 plant and the connection to the electric power network was carried out with techno-economic and spatial planning data in order to obtain a preliminary approval for the construction of the production facility.
Abstract: The goal of this study is to define a proposal for the configuration of the network of the city of Dubrovnik, which would meet the needs for electricity, and in the long term ensure the security of power supply to existing and new consumers with reliable placement of electricity from existing and planned production facilities. Namely, with the adoption and construction of the first stage of the Dubrovnik Program, in addition to TS 110/35 kV Komolac, the main power supply facility of the city is TS 110/20(10) kV Srđ, and the main nodal point of the Dubrovnik area is TS 220/110/35/20(10). kV Plat. Further considerations indicate the need for the construction of an additional 110/20(10) kV transformer station, which would be located on the site of the existing TS 35/20(10) kV Lapad and take over the power supply of the western and central parts of the city of Dubrovnik.
Abstract: In the study, a preliminary analysis of the justification of the construction of the Bračevići VE plant and the connection to the electric power network was carried out with techno-economic and spatial planning data in order to obtain a preliminary approval for the construction of the production facility.
Abstract: The aim of this study is to assess the existing portfolio of wind power projects developed by companies on the domestic market from the perspective of: •
Abstract: This study elaborates on the conceptual level the possible directions and stages of the development of the transmission network of southern Dalmatia, in such a way as to primarily define the proposal: -
Abstract: The study deals with and selects the method of connecting the Jelinak wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: In the study, a preliminary analysis of the justification of the construction of the Melina power plant and the connection to the electric power network was carried out with techno-economic and spatial planning data in order to obtain a preliminary approval for the construction of the production facility.
Abstract: In the study, a preliminary analysis of the justification of the construction of the Pliš power plant and the connection to the electric power network was carried out with techno-economic data and spatial planning data in order to obtain a preliminary approval for the construction of the production facility.
Abstract: In the study, a preliminary analysis of the justification of the construction of 6 different wind farms and their connection to the power grid was carried out with techno-economic data and spatial planning data in order to obtain a preliminary approval for the construction of a production facility.
Abstract: In the paper, an analysis of the possibility of the operation of the protection of the transformer TR2 in TS 110/35/10 kV Makarska was carried out, due to the occurrence of a single-pole short circuit on the transmission line in the incident transmission network 110 kV.
Abstract: The paper presents a numerical analysis of the electromagnetic impact of the 110 kV Pehlin – Turnić two-system cable connection on nearby metal masses and installations. This is a two-system cable connection in which, on parts of the route, there are as many as four cable systems in a common cable duct, which, during the occurrence of a single-pole short circuit in the associated 110 kV network, electromagnetically influence each other, and also exert an electromagnetic impact on nearby metal masses and installations (e.g. metal water and gas pipes, etc.).
Abstract: In the paper, a numerical analysis of the electromagnetic influence of the two-system cable connection 110 kV Pehlin – Turnić on nearby telecommunication lines was carried out. It is a two-system cable connection where on parts of the route there are as many as four cable systems in a common cable channel, which during the occurrence of a single-pole short circuit in the associated 110 kV network electromagnetically influence each other and exert an electromagnetic influence on nearby telecommunication lines as well .
Abstract: The paper presents a numerical calculation of the existing grounding system of the 110 kV switchgear at the Buško Blato substation, and - considering the increase in the associated single-pole short-circuit current - the associated safety conditions are numerically verified.
Abstract: This study includes measurements and analysis of the characteristics of the grounding system in the area of the dam, sluice chamber, pressure pipeline, engine room and switchgear. The following measurements were carried out: Measurement of the resistance of the earthing conductor: Measurement of the potential of the ground points in the appropriate directions as well as measurement of the potential of metal masses: Measurement of the contact voltage in the area of the power plant, administration building, dam and sluice chamber: In addition to the measurements themselves, the study includes an overview of the basic protective characteristics of the grounding systems, with reference to the regulations: principles of measuring the resistance of the spread and step voltages: the procedure for determining the current relevant for determining the potential image of the earthing conductor and analysis of the measurement results.
Abstract: The paper analyzes the cause of the failure of wind turbines VE 7 and VE 8 in the Trtar – Krtolin wind farm. After the most likely cause of the transformer failure in the mentioned wind turbines was established, specific measures to improve the overvoltage protection of the Trtar – Krtolin wind farm system were proposed. In this regard, the selection of appropriate surge arresters for wind turbine protection was carried out, and instructions for their installation were provided.
Abstract: The paper presents analyses and calculations of overvoltage protection of the cable connection 35 kV plant - house transformer in HPP Senj. The expected overvoltage stresses of the observed cable connection were analyzed, and appropriate surge arresters were selected. They were then numerically tested by analyzing their operation in situations of unfavorable expected overvoltages.
Abstract: The paper presents analyses and calculations of the relay protection system settings for 110 kV incident transmission lines at the Buško Blato substation.
Abstract: The paper analyzed and proposed a solution to the problem of meeting safety conditions at temporary work sites for the rehabilitation of the supply tunnels of RHE Velebit, HPP Orlovac, HPP Zakučac and HPP Kraljevac. For each individual hydroelectric power plant, the most favorable (safe and economical) solution to the mentioned problem of meeting the safety conditions during operation in the very unfavorable (difficult to access and wet area) conditions of the supply tunnels of the mentioned hydroelectric power plants was offered.
Abstract: In the study, a preliminary analysis of the justification of the construction of the Stražbenica plant and the connection to the electric power network was carried out with techno-economic and spatial planning data in order to obtain a preliminary approval for the construction of the production facility.
Abstract: The Zakučac HPP is the largest hydropower plant in the Cetina River basin, located at the mouth of the Cetina River near Omiš. It uses water from two distant reservoirs: Peruća and Buško Blato, which perform seasonal (Peruća) and annual (Buško Blato) equalization of watercourses. With these two reservoirs, the Zakučac HPP has the possibility of peak operation throughout the year. With a total installed capacity of nearly 500 MW, it is a key facility in the Croatian power system. The grounding of the switchgear, production facilities and facilities along the Gata basin are galvanically connected and form a single grounding system. Due to the possibility that the Zakučac HPP grounding system is galvanically connected to the grounding system of the wider consumer area of Omiš and Dugi Rat through known and unknown installations (water supply network, low-voltage network and similar installations), the RP 110 kV grounding system next to the Kraljevac HPP was selected as an auxiliary grounding system (current probe). This grounding system is far enough away to safely avoid overlapping potential funnels. Measurements on the grounding conductor of the HPP “Zakučac” were carried out by simulating a condition similar to a single-pole short circuit. The determination of the potential distribution was carried out along six directions. The measurement of the touch and step voltages at all locations, except for the gate chamber, did not record any significant values. Measurements on the grounding conductor of the Prančevići dam were carried out as if it were a medium voltage facility. The analysis of the measured data allows us to conclude that the HPP Zakučac, as well as the Prančevići dam, meets the technical regulations on grounding of power plants.
Abstract: In this study, a proposal for the development of the distribution network is given based on the current situation and the forecasted growth of consumption in the considered area. The development plan is based on a detailed model of the MV power network and contains detailed development guidelines for five-year periods. For the distribution network, a forecast of the increase in consumption was made based on historical trends and plans for the realization of new larger consumer facilities.
Abstract: The study deals with and selects the method of connecting the Oton wind power plant to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: This study provides an elaboration of the hydroelectric power management system owned by EP HZHB Mostar with the aim of optimal management of production, taking into account the previously stated general and special conditions within which the system will be observed. Within this study, the following components of the production management system of EP HZHB Mostar were elaborated
Abstract: The study examines and selects the method of connecting the Glunča wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The study deals with and selects the method of connecting the Orlice wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The study examines and selects the method of connecting the Svilaja wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The study deals with and selects the method of connecting the Crno Brdo wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants N-1
Abstract: The subject of this study is the calculation of the short circuit of CS Buško Blato for the existing and planned state of the power grid in Croatia and Bosnia and Herzegovina. The short-circuit calculation was performed primarily for the purposes of dimensioning the primary equipment RP 110 kV CS Buško Blato, and it was also performed for other voltage levels.
Abstract: The study elaborates and proposes a comprehensive concept of a model for managing and optimizing the operation of the hydropower system (HES) of the Lika and Gacka river basins. The basic principles of water management, the system for planning the operation of the Lika and Gacka HES, forecasting models, basic principles of water regulation, operational planning and optimization of the basin’s operation, and the concept of an appropriate process database and knowledge base are presented.
Abstract: This study deals with the energy-economic contributions of the construction of the Peruć HPP, in such a way as to determine the possible annual production of the Peruć HPP, taking into account the operating regime of the Peruć HPP and the way the Peruć reservoir is used, as well as the expected average monthly elevation of the Peruć reservoir, as two basic parameters that determine the possible production of MHE Peruć. Next, the real economic value of the electricity produced at MHE Peruća is determined, and the costs of investment and operation of MHE Peruća are updated. Based on the previous input assumptions, in the second part of the study, an economic-financial analysis (liquidity analysis) of the Peruć HPP construction project was performed, as well as an analysis of the project’s effectiveness and a corresponding risk analysis, i.e. sensitivity to changes in input parameters/assumptions.
Abstract: The study examines and selects the method of connecting the Ponikve wind farm to the 110 kV transmission network, and examines power flows in characteristic stationary operating modes, in variants of full transmission network availability and N-1 variants.
Abstract: The study analyzes the measurement results at the point of connection of the TLM to the power grid, i.e. at those locations that are relevant for assessing the impact of the facility on the quality of electricity with respect to two indicators: harmonic voltage distortion and flicker.
Abstract: This study is intended as one of the possible bases (and that is its purpose) for all future work related to the further construction of the automation system of individual facilities and the Senj HPP as a whole. Accordingly, the collection and analysis of all possible experiences regarding the automation of hydroelectric power plants (HP) in general, and the HPP of the Senj hydropower system in particular, imposed itself as the main goal of the study. When preparing the study, already completed studies and conceptual designs were used in which issues concerning individual facilities of the Senj hydropower system were analyzed from various bases, and for the structuring of the material itself, a similar study was used that was conducted in 2005 for hydroelectric power plants in the Cetina River basin. The study is focused on the area of automation in the function of the monitoring and control system of hydroelectric power plants and other facilities of the Senj hydropower system, either individually or from a future center. Based on the author’s personal experiences and knowledge, as well as the transmitted experiences and knowledge of others in Croatia and the world, the study indicates some basic elements that should be taken into account during the reconstruction and further construction of the HE automation system and its raising to a higher level by introducing new technologies. The material is divided into two parts. In the first part, topics related to identification and are usually specific to a specific hydroelectric power plant are covered, and in the second part, those topics that are common to all hydroelectric power plants. The first part of the book, which includes the first five chapters, deals with the identification of objects, plants and processes, as well as automation systems at the level of individual power plants and connection systems at the level of HES Senj. The term hydroelectric power plant automation means the unity of two systems. First, it is a management, signalling, protection, measurement and regulation system (USZMR) and, secondly, it is a process information system (PROCIS). The USZMR and PROCIS systems include secondary equipment for monitoring and controlling hydromechanical and primary equipment. Primary equipment includes: production units, switchgear, own consumption and auxiliary plants. The equipment in the USZMR system is directly connected to the primary equipment, and consists of measuring elements, protective devices, measuring and signaling devices, executive elements, local control units and regulation units. USZMR enables local monitoring and manual control, local automatic control and regulation and an interface to the superior level. PROCIS is an upgrade of USZMR at a higher hierarchical level that enables: individual control of functional groups, group control and remote control from a superior center. Identification was carried out in three ways: (1) by reviewing and analyzing available technical documentation, which was done in cooperation with operating personnel, (2) by interviewing operating personnel in cases where documentation was insufficient and (3) by visiting and inspecting the plant. In this way, a huge amount of data was collected, which is presented in special tables. Although the identification was done for the needs of the study, i.e. with less detail than is necessary when it comes to the actual implementation of the HPP automation system, it required enormous effort and time because most of the data and information required verification on the ground. In the second, common part of the study, an analysis of the automation system is given in function of the operating mode of individual HPPs (Chapter 6), and an assessment of the state of the art and technology in the field of HPP automation (Chapter 7). In this second part of the book, according to its scope and content, Chapter 6 is dominant, where a detailed analysis of the control and regulation functions that are already appearing or will increasingly appear in HPP Senj is given. Among other things, secondary frequency and exchange power regulation, secondary voltage and reactive power regulation, and group control of the hydropower plant are analyzed. Some elementary theoretical issues were also addressed, which seemed necessary given the fact that there is almost no experience in the field of group control and secondary voltage and reactive power regulation in our country. Some attention was also paid to the relationship between the operation of a hydroelectric power plant and the control functions that need to be automated, and a brief analysis of the approach to the reconstruction of the HPP automation system was also given.
Abstract: The Kraljevac hydroelectric power plant was built on the Cetina River at the beginning of the 20th century and is one of the oldest hydroelectric power plants in this area. The Kraljevac substation in the immediate vicinity of the Kraljevac hydroelectric power plant is an important 110 kV node in the network. It is energetically connected to the Kraljevac hydroelectric power plant with the two aforementioned 110 kV transmission lines and one 35 kV line. The grounding systems of the Kraljevac substation and the Kraljevac hydroelectric power plant are connected, but they are not (or do not have to be) equipotential. The known connection between the grounding conductors is, in addition to the protective cables of the 110 kV transmission line and two Cu cables with a cross-section of 50 mm2 in the cable duct connecting the two plants. Unknown connections are also possible via insulated or grounded metal masses such as the water supply network. Therefore, it is impossible to calculate the longitudinal impedance of the connection between the grounding conductors with sufficient accuracy, but it should be determined by measurement. Knowing the longitudinal impedance is important in order to be able to assess the danger of carrying high potential from the TS facility to the hydroelectric power plant.
Abstract: The study investigates the existing solution and defines a new concept of a comprehensive solution for the power supply of facilities on the Dugopolje-Zagvozd motorway route at voltage levels 10(20)-35-110 kV, including power flow analysis, N-1 analysis and basic cost analysis.
Abstract: The paper deals with the foundations and the development of a preliminary design for the Podkom wind farm. It describes the available wind potential, recommends a possible class of wind turbines for installation and connection to the electricity grid.
Abstract: As part of the revitalization of the ZAKUČAC HPP, among other things, the construction of 110 kV and 220 kV cable systems is planned on the stretch from the block transformer in the power plant’s engine room to the external facilities. Modern dry cables with cross-linked polyethylene insulation are planned to be placed on cable shelves in the tunnel connecting the engine room with the external 110/220 kV facility. Due to the importance of the Zakučac HPP in the power system of the Republic of Croatia, it is understandable that attention is paid to the correct dimensioning of these cable systems for long-term and reliable operation. The key factor for achieving this goal is the correct calculation of the cable overtemperature in operating conditions, since it is an accepted empirical fact that a permanent increase in temperature of only 7°C above the nominal can reduce the life of the facility by half. On the other hand, those involved in thermal calculations are aware of the difficulties of calculating thermal fields in complex convective conditions. Namely, the aforementioned cable systems pass through a tunnel with forced ventilation and humidification, and in the same tunnel there are other dissipative and non-dissipative installation systems. In such conditions, due to the pronounced nonlinearity of the problem, it is practically impossible to carry out a sufficiently accurate calculation of the thermal field in the static and especially in the dynamic (transient) operating mode. Therefore, research is resorted to on a physical model that is placed in a real environment. Measuring the temperature response in the dynamic mode will provide information about the behavior of the system in extreme situations and help the personnel managing the plant in assessing operational safety in such situations.
Abstract: The study examines and proposes variants for connecting the Pometo Brdo wind farm to the 110 kV transmission network or the 35(10) kV distribution network, including the techno-economic feasibility of individual variants.
Abstract: The subject of the study is the examination/analysis of the possible effects of the plant for the production of concrete reinforcements of the investor Montaling d.o.o. to the distribution network. The report was prepared based on the request of HEP Distribucija d.o.o. to check the impact of the planned operation on the distribution network. The planned facility will be connected to the distribution network via its own TS 10(20)/0.4 kV and two cable lines 10(20) kV at TS 35/10 kV Ploče (Vranjak), as a temporary solution until construction and connection to the new TS 110/10(20) kV Ploče after it is built.
Abstract: The subject of the elaboration of this document is a preliminary overview of the possible directions of development of the distribution network in the Dubrovnik area, primarily the primary part that does not include a more detailed elaboration of the construction of the 10 kV network. The subject covers the area that is currently supplied from the transmission network via TS 110/35/10 kV Komolac, i.e. stretch from TS 35/10 kV Slano to TS 35/10 kV Plocice.
Abstract: The study explores and defines the conceptual solution for power supply to the facilities of the planned Ploče-Dubrovnik highway.
Abstract: In accordance with the knowledge about the particularities of each HPP, the overall material of the study Analysis of automation of hydroelectric power plants of the Cetina watercourse …… is divided into five books, one for each hydropower plant: HPP Peruća, HPP Orlovac, HPP Đale, HPP Zakučac and HPP Kraljevac. Each book is divided into two parts. In the first part, topics related to identification and are usually specific to a specific hydroelectric power plant are covered, and in the second part, those topics that are common to all hydroelectric power plants. The first part of each book, which includes the first five chapters, deals with the identification of facilities, plants and processes, automation systems at the level of hydroelectric power plants and connection systems at the level of the Cetina basin. The term hydroelectric power plant automation means the unity of two systems. First, it is a management, signalling, protection, measurement and regulation system (USZMR) and, secondly, it is a process information system (PROCIS). The USZMR and PROCIS systems include secondary equipment for monitoring and controlling hydromechanical and primary equipment. Primary equipment includes: production units, switchgear, own consumption and auxiliary plants. The equipment in the USZMR system is directly connected to the primary equipment, and consists of measuring elements, protective devices, measuring and signaling devices, executive elements, local control units and regulation units. USZMR enables local monitoring and manual control, local automatic control and regulation and an interface to the superior level. PROCIS is an upgrade of USZMR at a higher hierarchical level that enables: individual control of functional groups, group control and remote control from the superior The identification was carried out in three ways: (1) by reviewing and analyzing available technical documentation, which was done in cooperation with operating personnel, (2) by interviewing operating personnel in cases where documentation was insufficient, and (3) by visiting and inspecting the facility. In this way, a huge amount of data was collected and presented in separate tables. Although the identification was done for the needs of the study, i.e. with less detail than is necessary when it comes to the actual implementation of the HPP automation system, it required enormous effort and time that were almost not appropriate to the given framework of the study. Namely, it turned out that for most of the data and information, it was necessary to check on in the field itself, i.e. the available documentation was not sufficient. The second, common part of the study provides an analysis of the automation system in function of the operating mode of individual HPPs (Chapter 6), and an assessment of the state of the art and technology in the field of HPP automation (Chapter 7) . In this second part of the book, according to its scope and content, the dominant chapter is Chapter 6, which provides a detailed analysis of the management and regulation functions that are already occurring or will increasingly occur in the HPPs of the Cetina River. Among other things, secondary frequency regulation and exchange power, secondary voltage and reactive power regulation, and group control of hydroelectric power plants. Some elementary theoretical issues were also addressed, which seemed necessary given the fact that there is almost no experience in the field of group control and secondary voltage and reactive power regulation in our country.Some attention is also paid to the relationship between the operation of a hydroelectric power plant and the control functions that need to be automated, and a brief analysis of the approach to reconstructing the HPP automation system is given. The seventh chapter describes the technological features important in the selection of secondary equipment for HPPs and in the construction of new infrastructure in the power system. , today and in the near future. This refers to: the pace of change in secondary technological equipment: the process of development and integration of the USZMR and PROCIS systems: the development of the generator diagnostic monitoring system, the evolution of protection system tools and the so-called super-infrastructure for improving the operation of the electric power system.
Abstract: In the study, a complete concept of the management and optimization model of the hydropower system (HES) of the Cetina river basin was elaborated and proposed. The basic principles of water management, the system of planning the operation of the Cetina HPP, prognostic models, the basic principles of water regulation, operational planning and optimization of the watershed, as well as the conception of the appropriate process database and knowledge base are given.
Abstract: The study presents the results of testing frequent outages in the industrial power grid of the Dalmacijacement cement plant. The most common cause is short-term voltage drops caused by a short circuit in the surrounding transmission network. Possible solutions to the problem are also proposed.
Abstract: The study can be divided into two characteristic parts: study and research. The study part, which includes chapters 2 and 3, first provides an overview of the state and development of hydropower unit monitoring, which is based on available literature and the experiences of international and domestic companies in this field. Furthermore, the monitoring of individual quantities that are included in standard diagnostic monitoring, such as vibrations, partial outages, air gap and magnetic induction in the air gap, is described in detail. The research part of the study includes chapters 4 and 5. Chapter 4 describes a system called monitoring of electrical quantities of hydrogenerators. This system was installed on generator 1 in HPP Peruća, for experimental purposes, and was defined in such a way that it includes quantities that are relevant for the behavior of the generator in stationary and dynamic states. These are armature voltages and currents, excitation voltage and current, rotor position and field in the air gap. The system was built in cooperation between HEP, FESB Split and VESKI Zagreb, and represents a logical extension of the transient monitoring system previously developed by the aforementioned company. One feature of the system is the measurement of instantaneous voltage and current values, as opposed to the usual monitoring of effective values when currents and voltages are introduced into the monitoring system as process variables. Another feature is the introduction of the rotor rotation angle into the monitoring of hydropower units, which was done to determine the generator load angle. In this way, the conditions for the application of a mathematical model of the generator for the analysis and diagnostics of operating events would be met. The application of mathematical models for the purpose of diagnostic analyses is also a modern trend in the monitoring of industrial plants. For example, in electric motor drives with asynchronous motors, where voltages, currents and rotation speed are recorded for this purpose. The experimental system for monitoring electrical quantities, which was installed on generator 1 in the Peruća HPP, was conceived in the first step as a basis for research and development of a method for determining the load angle in stationary and transient operating modes of generators in real operation. The development of a system for determining the load angle was, therefore, the first goal of the research. There are two reasons for setting this goal: (1) knowledge of the load angle is a necessary condition for introducing a mathematical model into the diagnostic analysis of the generator state and (2) there are no devices for measuring the generator load angle except for laboratory purposes. The second goal that was set, which was the research and development of a procedure for identifying the parameters of the hydrogenerator during operation (on-line), directly depended on the accuracy of the procedure for determining the load angle. During the research conducted within the framework of this project, a special identification procedure was developed that was theoretically tested and compared with similar procedures from the literature. It was shown that the developed identification procedure has some advantages such as greater reliability and less sensitivity to the initial values of the parameters. After the problem of determining the load angle was successfully solved, it was possible to perform some checks in the actual operation of the generator in the Peruća HPP. In this sense, an on-line identification of the synchronous reactance in the longitudinal and transverse axis was carried out for different operating points of generator 1. A procedure for determining the stray reactance of the armature winding during generator operation was also investigated, which is also based on measurements within the framework of the electrical quantity monitoring system. Furthermore, a procedure for on-line identification of the reactance of the substitute network was developed and verified, in the laboratory and in the actual plant of HPP Peruća, i.e. short-circuit reactances on the generator terminals. In the 5th chapter of the study, the mentioned researches are described and the obtained results are presented. Once again, it should be emphasized that these results were achieved thanks to the experimental system for monitoring the electric quantities of the hydrogenerator, which, within the framework of this project, was designed, installed and tested on generator 1 at HPP Peruća. In the 6th chapter of the study, certain proposals are given for the introduction of monitoring of hydro aggregates in the hydroelectric power plants PP HE Jug. These proposals are based on analyses of the status and trends in the development of hydropower monitoring in the world and in our country, but also on the results of research carried out within the framework of this study, namely the scientific project Estimation of variables and parameters of electrical machines.
Abstract: The study examines and proposes variants for connecting the Velika Glava and Mravinjace wind farms to the 110 kV transmission network, including the techno-economic feasibility of individual variants and a basic calculation of power flows for the purpose of determining the possibility of accepting the maximum power of wind farms by the transmission network.
Abstract: The restructuring of HEP, as well as the entire reform of the energy sector, takes place under the permanent imperative of harmonizing with the relevant EU regulations. Directive 2003/54/EC, which entered into force in the middle of 2003 and replaced the previous Directive 96/92/EC, is of key importance. and the long-term interests of Croatia in the field of electric power, the author’s view of the above issue is given. Possible options with their pros and cons are also suggested, including concrete suggestions.
Abstract: The study examined the effects of introducing the MTU system in DP Elektrodalmacija, as well as the possibilities of expanding the basic tariff switching function to new applications.
Abstract: Formation of corporate relations in HEP Group
Abstract: The “Podi” business and residential zone in the Dugopolje municipality is located in the area south of the Split-Sinj expressway and mainly east of the Dugopolje-Koprivno local road. It is largely equipped with utilities, with a large number of business buildings already built (or under construction). In addition to the construction of business buildings, the plan is to also delimit the area for residential construction (see the attached geodetic map). However, the zone is intersected by two transmission lines. Every active power facility is a source of electromagnetic fields. In the vicinity of the source (at a distance much smaller than the wavelength, which for the fundamental wave is about 6000 km), it is possible and appropriate to observe the electromagnetic field as two more or less independent components: ELECTRIC FIELD and MAGNETIC FIELD. The good agreement of the results obtained by measuring in the vicinity of the transmission line and those obtained by calculation indicates, on the one hand, the reliability of the measured values, and on the other hand, the acceptability of the model for field calculation. This then enables reliable interpolation and extrapolation of field values in space and for different possible current loads of the transmission line. From this, it can be concluded that in the zone 60 m from the axis of the 400 kV transmission line and 40 m from the axis of the 110 kV transmission line, the construction of facilities intended for the population with increased sensitivity (school, hospital, kindergarten, children’s playgrounds, etc.) should be avoided.
Abstract: The study investigates and defines a comprehensive solution for the power supply of facilities on the Zagvozd-Ploče motorway route at voltage levels of 10(20)-35-110 kV, including power flow analysis, N-1 analysis and short circuit calculation.
Abstract: The study investigates and defines a comprehensive solution for the power supply of facilities on the Dugopolje-Zagvozd motorway route at voltage levels of 10(20)-35-110 kV, including power flow analysis, N-1 analysis and short circuit calculation.
Abstract: The study examines and selects the method of connecting the Orlice wind farm to the 110 kV transmission network or the 30 kV distribution network, and examines power flows in characteristic stationary operating modes, in variants of full transmission network availability and N-1 variants.
Abstract: The study deals with and selects the method of connecting the Trter-Krtolin wind power plant to the 30 kV distribution network, and examines the power flows in characteristic stationary modes of operation, in variants of complete availability of the transmission network and variants of N-1
Abstract: The study defines and examines possible variants of the construction of the 110 kV overhead line on the Trogir - Bilice route, including calculations of power flows in characteristic regimes, and N-1 analysis.
Abstract: The preparation of this study was motivated primarily by the power supply problems of TS Dobri, i.e. by analyzing the possibility of parallel operation of the 35/10 kV transformer in TS Dobra in the period of high consumption when the current switching condition causes overloading of the transformer, but also of the 35 kV cables, given their very poor technical condition. Apart from the mentioned problem, the condition of the 35 kV network of DP Elektrodalmacija is such that operational dispatching and planning analyzes of different network configurations are relatively often requested, i.e. analysis and resolution of various operational problems. The study deals with the possibilities of better power supply to TS 35/10 kV Dobri, with parallel operation of the 35/10 kV transformer, taking into account the network load and the limitation of three-pole short-circuit currents.
Abstract: The study investigates and defines a conceptual solution for the electrical power supply of facilities on the Prgomet-Dugopolje highway route.
Abstract: Planning the use of large reservoirs for electricity generation is a very demanding and complex problem. In addition to the requirements and limitations resulting from the search for an optimal operating regime for energy purposes, planning is also conditioned by the requirements of other water users and the requirements of flood protection. The subject of this study primarily includes examining the possibility of defining a new model of use and management of the Buško Blato reservoir and the Orlovac hydropower system (HES) as a whole, since data on the achieved production in the previous period of use of the reservoir show very large seepage losses, depending on the elevation.
Abstract: The study investigates the impact of fitting the new 240 MW Jetovec gas thermal power plant into the Croatian power system from the point of view of fitting into the daily production diagrams, monthly and annual power balances, and the impact on the variable and marginal costs of the operation of the EES of Croatia.
Abstract: The study investigates and defines possible options for the development of the 110-220-400 kV transmission network of JP EP HZ Herceg-Bosne, in stages for 5-10-15 years based on existing development plans and analysis of power flows and N-1.
Abstract: The study examines the possibility of indirect start-up of PHE Čapljina with a power of 460 MW on the existing 220 kV transmission network.
Abstract: This study is part of the third phase of regional energy planning in Split-Dalmatia County. The study includes analyses of the potential contribution of energy efficiency and renewable sources to the future energy supply of Split-Dalmatia County, and proposes measures and further activities needed to exploit their enormous potential and implement commercial projects.
Abstract: The study provides a calculation of short-circuit currents in the industrial power grid of the TLM Šibenik factory, at all voltage levels, depending on the characteristic switching states.
Abstract: This study presents the results of the second phase of the project Energy Development of Split-Dalmatia County. While the first phase of the research included the creation of an energy database with data collection, conducting a household survey and an audit of services, in this second phase the energy balance of the county was created and the energy needs forecast until 2020 was forecast. With this phase of the research, all the bases for the analysis of the future structure of the energy supply of the county were prepared. This primarily refers to gasification and the substitution of electricity consumption, primarily with gas but also with renewable energy sources (solar energy).
Abstract: In this study, voltage conditions, power flows and losses in the network are analyzed for different variants of the connection of the Roški Slap HPP to the existing 10 kV network with possibly necessary upgrades, and some variants of solutions for the evacuation of the generated power at a higher voltage level (20 kV) are provided.
Abstract: The study investigates the impact of fitting the new 385 MW Lukovo Šugarje coal-fired thermal power plant into the Croatian power system from the point of view of fitting into the daily production diagrams, monthly and annual power balances, and the impact on the variable and marginal operating costs of the EES of Croatia.