The education of electrical power engineers requires a deep understanding of complex high-voltage infrastructure, yet physical access to these critical facilities is often restricted due to safety regulations and logistical constraints. This paper presents a methodology for developing high-fidelity virtual reality (VR) educational tools designed to bridge the gap between theoretical instruction and field practice. We propose a workflow for creating "virtualized objects"—digital visualizations of real-world environments—using interconnected 360-degree panoramic nodes. The study uses two primary data acquisition methods: consumer-grade 360-degree cameras and high-resolution DSLR photography. Our findings indicate that while consumer cameras offer rapid deployment, the DSLR-based approach provides the superior resolution and dynamic range necessary for the legible visualization of technical details, such as equipment nameplates and component conditions. The practical application of this methodology is demonstrated through two pilot modules: a 400 kV substation and a power line conductor installation. These tools integrate interactive "Education Elements" (video, audio, and datasheets) to enhance spatial literacy and safety awareness among engineering students.

This paper, developed in cooperation with Slovenska elektrizacna prenosova sustava, a.s. (SEPS), analyzes voltage stability in the eastern Slovak transmission system, focusing on the impact of the Vojany (EVO) power plant shutdown. The results show that the shutdown has no significant effect on voltage stability, as the maximum load in DS areas remains unchanged. However, the operation of tie-lines 477 and 478 has a greater impact, with their disconnection leading to lower maximum loads and steeper PV curves, indicating reduced stability. The findings suggest that a new power plant connected to the 400 kV grid with sufficient reactive power control could improve voltage stability in the region..

Three-winding transformers used in the power system typically have the third winding connected in a delta configuration, which significantly affects the impedance in the zero-sequence, the current in the zero-sequence, and influences the flow of the third harmonic in the electrical network. The paper presents an analysis of the third harmonic from the perspective of transformer winding connections based on simulations in MATLAB Simulink.

This paper analyzes the symmetrical components of three-winding transformers, emphasizing the influence of winding connections on equivalent models and zero-sequence impedance. Using MATLAB simulations, the study demonstrates how delta-connected tertiary windings modulate fault currents and zero-sequence behavior. Building on prior research on two-winding transformers [8], the findings provide actionable insights for designing power system protection schemes and fault analysis methodologies.

Public lighting networks (PLNs) play a crucial role in urban infrastructure, directly impacting safety and comfort. This paper presents a comprehensive analysis of PLN operation at reduced voltage, considering factors such as voltage drop, line parameters, and component capabilities. A case study demonstrates the feasibility of operating PLNs with a wide voltage range, offering insights into potential benefits and challenges. Overall, the study underscores the potential of innovative operational models to enhance the efficiency and reliability of public lighting networks.

The paper deals with the issue of symmetrical components in transformers, considering various winding connections in the occurrence of different types of faults. The transformer is a determining element for the connection of the equivalent model in the zero-sequence and, therefore, also determines the magnitude of the impedance in the zero-sequence and the magnitude of the zero-sequence current. The equivalent model in the zero sequence primarily affects fault currents and voltage in the electrical grid during the most common fault, the phase-to-ground fault. The theory of component systems is well-known and widely published. This paper aims to explain the properties of a two-winding transformer in symmetrical component systems based on the results of simulations implemented in MATLAB.

The contribution deals with the issue of the impact of the blocking of the automatic voltage regulator (AVR) on the TS/DS transformers located between the transmission and distribution system on the voltage stability of the transmission system (TS) in the event of a voltage decrease in the nodes of the TS. The contribution is a partial collaboration with the Slovak transmission system operator (TSO) Slovenska elektrizacna prenosova sustava, a.s. regarding to the assessment of voltage stability considering the scenario of increasing transit through TS SR.

In recent years, the emerging fear of an energy crisis in central Europe has caused an increased demand for distributed energy resources (DER), especially small photovoltaic rooftop installations up to 10 kWp. From a technical point of view, distributed PV in low-voltage networks is associated with the risk of power quality violation, overvoltage, voltage unbalance, harmonics, and violation of the thermal limit of phase conductors, neutral conductors, and transformers. Distribution system operators (DSO) are currently in a position to determine the amount of installed PV power for which reliable and safe network operation is ensured, also known as the photovoltaic hosting capacity (PVHC). The presented study describes a stochastic methodology for PVHC estimation and uses it to analyze a typical LV rural network in the Slovak Republic. Detailed and precise calculations are performed on the 4-wire LV model with accurate results. In this study, we, thus, profoundly analyze the problems with voltage violation, unbalanced voltage energy losses, and the thermal loading effect of increasing PV penetration. The results show that overvoltage events are the main factor limiting the PVHC in LV systems. This conclusion is in accordance with the experience of the DSO in the Slovak and Czech Republic. Subsequently, the study focuses on the possibilities of increasing PVHC using those tools typically available for DSO, such as changes in PV inverter power factors and no-load tap changer transformers. The results are compared with those derived from similar analyses, but we ultimately find that the proposed solution is problematic due to the high variability of approaches and boundary conditions. In conclusion, the paper discusses the issue of the acceptable risk of overvoltage violation in the context of PVHC and lowering losses in LV networks.

Calculation and measurement of the overhead power lines electrical parameters is common practice in today's electrical engineering industry; however, there is very little data to actually compare these two approaches because measured data in such detail are mostly unavailable for academic purposes. Based on the very detailed model of an overhead power line in MATLAB Simulink environment and conducted experimental measurement, this article specifically covers the exact evaluation of the impedance of the investigated overhead power line. Differences between calculation and experimental measurement are shown and discussed accordingly, where, surprisingly, the biggest deviation was observed in the positive resistance parameter. The connection between different measurement techniques (multiple single-phase and three-phase methods), as well as the power line asymmetry reflection in the impedance matrix is explained as well as compared to expected values from the computations. The complete mathematical approach for electrical parameters evaluation from different measurement methods is explained step-by-step, and the final equations are introduced for each method. Proposed methods of obtaining the electrical parameters of the power line are then concluded as the ones with great accuracy and wide usage in practical applications. It shows the great importance of correct input data for the electrical parameters' theoretical computations and the need to know the measurement methodology and apparatus perfectly to process the measured data and interpret them correctly.

The growing demand for implementing small renewable energy sources, photovoltaic or wind sources, in the distribution system is characteristic of the last decade. On the one hand, the distribution system operator (DSO) needs to meet this growing demand while being responsible for the reliable and safe operation of the network. DSO is therefore forced to analyze the risks associated with growing distributed production, such as overvoltages in the network, and determine their maximum allowed installed capacity, hosting capacity. This paper uses the stochastic methodology and probability power flow calculations to analyze the photovoltaic hosting capacity (PVHC) of an existing rural low-voltage (LV) system in the Slovak Republic. The outcomes show that overvoltages are the primary limiting factor in an analyzed network, and the PVHC depends on the permissible probability of their violation. The article further analyses the possible ways of increasing PVHC by gradual penetration of small battery energy storage systems. The results show that BESS should be considered only as a supplementary device, which will always positively affect the size of the PVHC if it is used to maximize the utilization of photovoltaic generation at the point of consumption.

The paper deals with the analysis of the current flowing through the transformer neutral, where the current is detected by the ground overcurrent protection in the normal operating state during routinely switching-off operations in the power system. The inspiration of stated issue was a real event in the operation of the power system when the overcurrent protection in the neutral of the generator transformer in the power plant operated. The reaction of the overcurrent protection was in accordance with its setting, but it responded to a normal situation in the transmission system, the disconnection of the transmission line, but not to a fault.

This article presents a comprehensive dataset comprising average 15-minute values of active and reactive energy consumption in 1000 anonymized households located in the Slovak Republic, a central European country, throughout the year 2016. The dataset provides a valuable resource for researchers and practitioners interested in analysing energy consumption patterns at the individual household level within the unique context of Central Europe. Privacy concerns are addressed through anonymization techniques, ensuring the dataset's compliance with ethical considerations and privacy regulations. However, ZIP code information is included for each household. Researchers can confidently analyze the data without compromising the households' confidentiality. The dataset offers significant opportunities for researchers to explore energy consumption patterns, develop targeted energy management strategies, and contribute to the advancement of sustainable energy practices.

The paper discusses the ongoing trends in distribution systems, such as increasing distributed energy generation combined with small battery storage systems. Distributed energy generation alone has a negative effect on power quality and can cause an increase in power losses in a situation with no consumption at a close distance. However, the situation with battery storage systems integration is far more beneficial for the consumers and the distribution system operator. The article presents a stochastic approach for analyzing such situations in low voltage networks. A real case study in a rural low voltage grid in the Slovak Republic with small photovoltaic rooftop systems combined with battery storage systems is performed. The analysis results show a significantly positive effect of battery storage systems on power quality and losses in the observed distribution grid.

The article deals with voltage stability of the power system (PS) and its assessment based on PV curves. We introduce an analysis of the influence of transformers with automatic voltage regulator (AVR) on the shape of PV curves and magnitude of voltage on the side of transmission system (TS) and distribution system (DS). The article was carried out in cooperation with the Slovak TSO – Slovenská elektrizačná prenosová sústava, a.s.

As is electromobility is still expanding, its effects on the power grid need to be expected and be prepared for. This paper is analyzing the possibilities of creating a very simple probabilistic model while keeping the outputs still accurate enough for most of the applications in power engineering. The simplicity and flexibility of this model are proposed by using the polynomial regression on the initial probability density functions and weighted random choices variables. These approximations are then defined in all the time frames during the simulation, which makes also the time step easily variable. The proper means of finding the polynomial regression functions are introduced, as well as the usage in the complete probabilistic model algorithm. Verification of the proposed model is carried out using open data. Applications and further extensions of the model are discussed.

Influence of tensile insulators on conductor tensile force is an issue that is still overlooked in detail today. The motivation of this article is to introduce the correct and analytic computational approach, which includes the bundle conductors in symmetrical spans. Bundle conductors are not mentioned in the basic mechanical tension formulas, and therefore some self-made modifications in this manner were not always correctly carried out. Our inclusion of bundled conductors into the state equation of the short span is verified through numerical computations (FEM) in PLS-CADD software. The results are applicable in the substation design, where such short spans with bundled conductors occurs the most. Furthermore, an analysis was carried out to show the line between the long and short span definition.

This paper studies the voltage stability of the Slovak Republic’s power system (PS) based on an assessment of the PV curves. The PV curve is a tool for assessing voltage stability, and based on its shape, it is possible to determine weak and strong voltage nodes with the possibility of voltage stability reserve quantification. We present an analysis of the influence of transformers with an automatic voltage regulator (AVR) on the shape of the PV curves and on the magnitude of voltage in the PS. In general, the 400 kV/110 kV transformers equipped with AVRs are critical assets for the PS as they address voltage control in the DS. However, in the case of voltage problems in the TS, the AVR function may worsen the voltage situation across the entire PS. Therefore, we closely analyze the negative effects of the AVR on the PS operation. This impact is clearly proved, and recommendations are given for the transmission system operator (TSO) in order to maintain voltage stability. In addition, the PV curves of the pilot nodes are analyzed very accurately, thereby confirming their importance in the TS in terms of a sufficient reserve of reactive power. The study was conducted in cooperation with the TSO, Slovenská elektrizačná prenosová sústava, a.s.

Distributed energy resources have become a stable and rapidly growing part of power systems. DER character and properties depend significantly on the type used technology and application. Their common feature is the probabilistic nature of their behavior and parameters. Penetration of DER into classical power systems raises the question of power quality and operational safety. This paper presents a general method to implement any DER into a custom power system and calculate the probabilities of possible impacts. The proposed method is based on the combination of deterministic, probabilistic, unknown parameters and information about investigating power system and future scenarios of DER penetration. The Paper also presents a case scenario where penetration of PV system into low voltage network is investigated. The last part shows the complex result of probabilistic power flow calculations. Presented methods have been used for practical applications to determine hosting capacity for PV systems in rural and urban areas of the Slovak republic.

This work refers to the concept of online monitoring of generators' dynamic stability based on the critical clearing time (hereinafter referred to as "CCT"). The CCT may be considered a basic criterion of the dynamic stability of a synchronous generator. The work presents an analysis of factors (operating condition of a generator, short-circuit power of the system, increase of the proportion of distributed production in the distribution system (hereinafter referred to as "DS ') influencing the CCT and analysis of possibilities to increase the value of the CCT. In this work, we present a relatively simple concept built on the calculation of the CCT using a swing equation, which may be implemented into the dispatch control of power systems (hereinafter referred to as "PS").

The current transformation of power systems is aiming towards distributed source integration and general decentralization. Renewable energy sources and support of local energy supply create conditions for widespread use of new technologies and smart grids. As the electrical grids become more electrically independent, the importance of frequency control will rise. Stability of the system in such cases is no longer only relying on rotating inertia of generators as in the centralized grid. This known scenario has already been analyzed by many with computational models for optimal safety precautions of the grid. This paper aims to update the common home appliance frequency characteristics through measurements and compare them to those currently used. These devices were divided into two groups: general categorization and light sources. Subsequently, the frequency sensitivity coefficients were evaluated and analyzed home appliances were sorted into three categories according to the size of their frequency sensitivity coefficient values: positive, negative, and no effect. The results were compared with studies aimed at evaluating the static load characteristics. A simplified simulation of the frequency control, presented in the discussion section, was carried out to determine the consequences of the newly measured characteristics and concludes the paper.