Electromagnetic levitation represents a contemporary line of technology with a wide spectrum of applications in several areas of engineering. Regarding the increased demands for this technology in-depth research into its dynamics and the influence of different material characteristics used in these systems is needed. This paper presents simulation results of electrodynamic levitation system regarding different types of materials used for levitating disc. The main intention is to provide a comparison of electrodynamic levitation systems with different materials used for levitating disc in order to improve the system itself. Therefore, the impact of different materials used for the levitating disc of the electrodynamic levitation system would be investigated through some parameters of interest such as an analysis of the electromagnetic force, disk displacement, and the time required to achieve a stable disk position.

This paper presents assessment of selected concept of medium voltage (MV) and low voltage (LV) power supply system of motorway energy consumers/systems on the Pan-European motorway corridor, branch Vc, in Bosnia and Herzegovina (BiH) through methods of reliability analyses. Assessment of selected concept is performed through comparison with different, enhanced and reduced, possible MV network and MV/LV transformer substation configurations. Comparison and analysis of different configurations have been made using of serial, parallel, serial-parallel and delta-star reliability model and Fault tree model. Objective was to confirm that selected concept offers optimized technical solution which provides reliable power supply, failure rate of the supply system as low as possible, together with relative simplicity of design. The results from the selected approach of reliability analyses indicate that this power supply concept entirely based on direct power supply from the primary transformer stations 110/x kV, which ensures two-sided MV power supply of MV/LV transformer substations and their redundant configuration provides reliable power supply of motorway consumers.

Nearby lightning strokes are often considered as a prime source of transient overvoltages in the substations. Lightning overvoltages can cause unreliable operation of power system and power supply interruptions. Calculation of expected lightning overvoltages is necessary to design appropriate protection system. This paper presents the analysis of the lightning overvoltage performance of real 400 kV overhead transmission line and gas insulated substation (GIS), considering various factors, such as lightning stroke locations, peak currents, front rise times, etc. EMTP-RV software was used to model transmission line and substation elements and conduct simulations, while transmission line lightning performance was determined using Sigma Slp software. The expected overvoltages and surge arrester currents are calculated and used to design lightning protection system of the considered substation. Obtained results also indicate the importance of proper modelling of power system elements and lightning strokes.

A building-integrated microgrid (BIM) has been a widely utilized concept in low-carbon smart cities. The key advantages of microgrids are using locally available renewable energy sources (RES) and reducing dependency on fossil fuels. Solar photovoltaic (PV) systems and battery storage systems play a crucial role in BIM to achieve desired goals. Due to legal/regulatory and technical restrictions, the distribution system operator (DSO) often imposes zero energy export (ZEE) for these microgrids. Therefore, the sizing of solar-battery systems in BIM, which will be technically feasible and economically optimized, is a challenge for designers, owners and DSO. The objective of this paper is to show the practical approach for design and sizing a microgrid for public buildings using the real data sets of a power consumption and solar energy production. As an example, the BIM for the Faculty of Electrical Engineering, University of Sarajevo is presented.

Direct current (DC) power systems are gaining interest in the last decade due to increased utilization of DC outputted power sources, DC based energy storage (ES) elements and DC inputted loads. Microgrids are also becoming widely researched as the main foundation of smart grid. It is therefore logical to try to utilize DC microgrid (DCMG) concepts in organization of power systems in wide range of applications. DC microgrids have several important advantages compared to alternating current (AC) microgrids. The control system is essential in order to keep DCMG operating properly, reliable and efficient. Their control structures, with special interest in hierarchical control are explored and compared in this paper in terms of architecture and techniques. This paper presents real world applications using DCMG concept. Future research propositions given in the final chapter can be used as a foundation for researchers exploring the area.

Energy consumed by trams is studied in many papers, with a wide diversity of approaches regarding how to model and solve this problem. A novel approach to modeling the power consumption of trams is presented in this paper. To identify the unknown parameters influencing the rolling resistance force acting on the tram, it is necessary to measure the power consumption and speed of a single tram (or multiple trams if there are different car types in operation). The developed model of the tram is calibrated with data from the Sarajevo tram system. Simulation results are compared with measurements and a good correlation was obtained. The power consumption model of the tram with identified parameters can be further used to develop a framework for the power consumption estimation of the traction substation.

The method of power transformer neutral point grounding is very important for power distribution network operation because it strongly affect the shapes and values of overvoltages and fault currents. Many methods of grounding are used in medium voltage (MV) power distribution networks. The selection of grounding method largely depends on the characteristics of power network connected to the substation. It is also necessary to consider the advantages and disadvantages of various neutral grounding methods during selection process to find the best solution from a technical and economical point of view. The effects of grounding methods on the characteristics of single-phase short circuit fault are discussed in this paper on the example of 110/20 kV substation ′′Bugojno′′. Modeling and simulation of the considered substation, power transmission and distribution lines are implemented in EMTP-RV software.

Overvoltages are unpredictable and extremely dangerous for the electric power system. The causes of overvoltages are different, but lightning is considered as one of the most serious causes of overvoltages. High voltage substations are one of the main parts of the power system whose faults caused by overvoltages can lead to outage of large part of power system. Therefore, overvoltage protection of a high voltage substation is very important. In order to protect the substation as much as possible from the effects of the overvoltages, it is necessary to implement elements that can help reduce these effects, for example surge arresters. This paper presents the effects of the use of surge arresters in high voltage, gas SF6 insulated substation, modeled in the EMTP-RV (Electromagnetic Transient Program-Restructured Version) software. An accurate representation of lightning surge incoming in the substation is very important because it strongly affects the design of overvoltage protection system. In this paper parameters of lightning strikes are determined using Sigma Slp software.

Transient events, especially those related to the short circuit faults, are the main causes of power distribution lines outages. This paper is dedicated to the analysis of three-phase short circuit fault and its impact to the real 20 kV power distribution lines. One of the most important parts of Bosnia and Herzegovina's power system was monitored and analyzed. Short circuit currents and voltages were obtained by using the power distribution lines numerical protection system measurements from the moment of fault occurrence to the moment when the faulty line was switched off. Part of the power system of interest was modeled in EMTP-RV (Electromagnetic Transient Program - Restructured Version) software which is standardized software for transient analyses. Several simulations were conducted to perform fault analysis. Measured data and simulation results were compared.

Short circuit faults are one of the most common disturbances in power systems that occur because of insulation failure due to a sudden overvoltage condition caused by lightning, switching operations, insulation contamination, etc. Medium voltage power distribution networks use different methods for grounding the neutral point. Influences of these grounding methods on the characteristics of single-phase short circuit fault are discussed in this paper on the example of substation “Bugojno”. Modeling and simulation are implemented in EMTP-RV (Electromagnetic Transient Program-Restructured Version) software. Data recorded by protection system during normal operation and three-phase short circuit fault in the substation are analyzed and used for comparison with simulation results to validate developed model of the observed part of power system. This validated model was then used to analyze the effects of neutral point grounding methods on the characteristics of single-phase short circuit fault.

Climate problems, the increasingly robust European emissions policy and falling prices of solar and wind have led to the shutdown of many thermal power plants and increased installation of renewable energy power plants. The installed capacity of wind and solar power plants in our country is not yet significant, but small hydropower plants are often considered as a good solution for the power supply to remote areas despite the problems that sometimes arise after the installation of these power plants. This paper describes a power quality problem of high voltages occurs after the installation of a small hydropower plant of 800 kVA in an area with predominantly industrial consumers. Many industries use high technology for manufacturing and require high power quality and reliability of power supply. Even modest power quality problems can have significant technical and economic effects on these consumers. Therefore, it was necessary to precisely monitor power quality to adequately address all related problem recorded during the plant performance test phase. Also, the observed problem has led to power plant outage on several occasions in a short period of time which resulted in a reduction in power generation. Techniques for mitigation the observed power quality issue are also considered in this paper. The implemented solution of the problem is verified by power quality monitoring and SCADA system measurements.

Connecting a photovoltaic solar power plant (PVSP) to a radial low-voltage network can significantly influence the power quality. According to grid rules in our country, the PVSP with rated power of up to 150 kW can be connected to the low-voltage power distribution network. Common case is that the PVSP with rated power of approximately 100 kW is installed at the rooftop of a residential or commercial building and connected to one connection point. Usually, the owner tends to regulate PVSP to operate at unity power factor to maximize profit. However, when the power plant operates with unity power factor, voltages at the connection point and at the nearby buses are often increased. Also, a significant increase of power losses can occur. This paper describes the procedure for determining the maximum power of the PVSP operating with unity power factor while simultaneously meeting the following criteria: (1) the range of slow voltage variations must be within the limits defined by the EN 50160 standard; (2) after connecting the PVSP, the active power losses should be less or equal to active power losses calculated with the disconnected PVSP.

This paper presents a new approach to the optimal placement of power quality monitors (PQMs) for voltage sag detection. Determining the optimal number and arrangement of PQMs is necessary since the installation of monitors at all buses in a network is an uneconomical option. The optimization problem is defined by the concept of topological monitor reach area. A new cost function is defined in order to simultaneously determine the required number of PQMs and their arrangement. Four optimization methods are implemented to solve the problem: Genetic Algorithm, Binary Particle Swarm Optimization, Binary Dragonfly Algorithm and Binary Bat Algorithm. The presented approach is tested on one part of the power distribution network in the capital city of our country. Simulations proved that the Binary Bat Algorithm has the best performance in terms of computational time, convergence and the probability rate of finding the global optimum.

This paper presents a new approach to determine the optimal number and arrangement of power quality monitors (PQMs) for voltage sag detection. It is necessary to determine the optimal number and arrangement of PQMs since their installation at all buses in a network is an uneconomical option due to relatively high price of PQMs. The appropriate mathematical model, that describes the considered optimization problem, is created by using the concept of topological monitor reach area. A new definition of the cost function is presented in the paper in order to simultaneously determine the required number of PQMs and their best arrangement. Also, the effect of setting different values of monitor's coverage control parameter on the obtained results is analyzed. Four optimization methods are implemented to solve the considered problem: Binary Bat Algorithm, Binary Dragonfly Algorithm, Binary Particle Swarm Optimization and Genetic Algorithm. The presented approach is tested on the IEEE 34-node test system. Simulations proved that the Binary Bat Algorithm has the best performance in terms of computational time, convergence and the probability rate of finding the global optimum.

The power system (PS) evolves with the introduction of new technologies in the sectors of production, transmission, distribution and control of electricity consumption. The philosophy of PS control, operation and management is changing. The public low-voltage network (LVN) faces the major changes due to integration of new smart grid technologies. The integration of photovoltaic power plants (PVPPs) and Energy Storage System (ESS) in LVN is a focus of this paper. Three scenarios are considered: (1) analysis of LVN without PVPPs and ESS, (2) analysis of LVN with PVPPs, where LVN is treated as energy storage (ES), (3) analysis of LVN with PVPPs and ESS. The novel algorithm for ESS control aiming to peak load reduction is presented in the paper. Losses and voltage conditions are analyzed on all LVN buses. The slow voltage variations analysis is carried out according to the EN50160 standard. It was shown that the connection of the ESS has negligible impact on losses in LVN. Slow voltage variations are within limits defined by standard EN50160 for all considered scenarios.