Stanislaw Czapp

Low-voltage networks are designed as solidly grounded neutral networks (TN, TT) or isolated neutral networks (IT). The latter type is used when continuity of supply and effective protection against electric shock are required despite a single ground fault. A characteristic feature of the IT network is the application of insulation monitoring systems, currently officially named Insulation Monitoring Device (IMD). The aim of this device is to signal the first ground fault, and the network can still be powered. This article shows a comprehensive overview of IMD solutions, from historical to contemporary. IMD structures and characteristic features, as well as critical evaluation, are presented, highlighting their advantages and disadvantages. The desired directions for the development of IMDs are indicated to ensure their proper functioning in modern power networks.

In the TN low-voltage network containing overhead lines with bare conductors, there may be a risk of electric shock if a line (phase) conductor breaks and falls to the ground. This risk results from the potential of the network neutral point, the level of which may exceed the permissible value of 50 V during this fault. Therefore, it is necessary to determine the resistance to earth of the bare conductor lying on the ground, which affects the aforementioned potential. This article presents a theoretical analysis related to the bare conductor lying on the ground and the results of the resistance to earth measurements for such a conductor.

The increasing number of prosumers presents a significant challenge for power grid operators at low- and medium-voltage levels. This necessitates a fresh approach to the development of planning procedures and methods. In this review, we focus on four key areas regarding distribution system development planning: (1) the application of multi-criteria analysis methods, (2) the integration of distributed energy resources, (3) the impact of prosumer inverters on the design and planning of networks and protection systems, and (4) maintaining voltage levels and local power balancing under market rules. We analyzed the major contribution of the existing literature to the field and identified key trends. We also proposed future directions for scientific research in the area.

Prior knowledge of wind energy production can significantly contribute to the enhancement of the dispatching capacity and grid management efficiency. Innately, wind speed has high unpredictable nature; this hinders the predictor from achieving good accuracy. To address this limitation, the proposed method in this paper provides the pre-processing step before deep learning-based prediction of wind speed. The pre-processing step involves thirteen nature-inspired algorithms that minimize the proposed objective function to obtain IMF combinations of atmospheric variables. The objective function ensures the selection of IMF (Intrinsic Mode Function) combinations of wind speed with a high correlation with the IMF combinations of other atmospheric variables. Each nature-inspired algorithm provides the outputs, which are further refined by the proposed OAIMF (Optimal Search IMF algorithm), which ensures the selection of fewer IMF combinations of wind speed. A case study of the Climate, Energy, and Water Research Institute (CEWRI), NARC, Islamabad, Pakistan, is considered for experimental analysis. RMSE, MAE, MAPE, and R ² performance measures are used for experimental verification. The proposed technique achieved an RMSE of 2.73 on the LSTM network and an RMSE of 3.86 on the GRU network. In the direct method, the RMSE value of 19.78 is obtained on the LSTM network, and the RMSE of 18.89 is achieved on the GRU network. Similarly, the proposed approach outperformed the other state-of-the-art pre-processing prediction techniques based on RMSE, MAE, MAPE, and R ² measures.

The maximum permissible load of underground power cables (known in U.S. engineering as “ampacity”) is a function of many parameters, in particular, the thermal resistivity of the native soil. If this resistivity is relatively high, thermal/stabilized backfill is applied, i.e., another material is placed around the cables, providing favourable conditions for heat transfer to the environment. It has a positive impact on the reliability of the power supply and favours the operational durability of the cables. In design practice, however, there is a difficult task—correct determination of the ampacity of the cable line depending on the thermal parameters and the geometry of the backfill. Therefore, this article presents the results of a numerical analysis to determine the ampacity of cable lines in which stabilized backfill is used. A new mathematical relationship is proposed that allows the correction of the ampacity of cable lines depending on their cross-section as well as the thermal and geometric parameters of the cable surroundings.

The current development of prosumer microsources and the expected spread of electric vehicles may cause the appearance of significant current and voltage unbalance in low-voltage (LV) networks. This unbalance, which is an unfavorable phenomenon, may occur when using single-phase photovoltaic (PV) microsources and single-phase home chargers for electric vehicles. This paper presents a proposal for the symmetrization of the LV network using devices for the reconfiguration of phases in the power supply. Both the different locations of these devices and the different objective functions for device implementation are analyzed. The research was carried out on an example LV network, taking into account several variants of the development of PV microsources and home chargers for electric vehicles. The analysis indicates that the appropriate location of phase reconfiguration devices and the use of an appropriate objective function leads to a significant reduction in unfavorable unbalancing in the LV network.

Ferroresonance in power networks is a dangerous phenomenon, which may result in overcurrents and overvoltages, causing damage to power equipment and the faulty operation of protection systems. For this reason, the possibility of the occurrence of ferroresonance has to be identified, and adequate methods need to be incorporated to eliminate or reduce its effects. The aim of this paper is to evaluate the effectiveness of ferroresonance damping in auxiliary power systems of high-voltage substations by selected damping devices. Laboratory experiments, the results of which created bases for the development of models of selected damping devices, are presented. These models were used to simulate the effectiveness of ferroresonance damping in an auxiliary power system of a 220/110 kV substation in the EMTP-ATP program. The analyses showed that control systems with different algorithms of operation are used in damping devices. This knowledge is important when selecting parameters and settings of the applied damping devices for a given network and the disturbances in it. The presented research results have proved the effectiveness of commercially available damping devices, provided their parameters are correctly coordinated with the settings of the power system protection.

The main requirements of national regulations and international standards regarding protection against electric shock in electric vehicle charging installations are presented. The principles of using residual current devices (RCDs) in such installations are discussed. It is pointed out that RCDs are mandatory equipment for safe charging of electric vehicles. It is noted that the standards require the use of RCDs having an appropriate type of tripping, due to the fact that in the event of an earth fault in the charging circuit, a DC component of significant value may appear in the earth fault current. A new type of residual current devices for DC installations (DC-RCD) has been indicated.

W instalacjach elektrycznych niskiego napięcia instaluje się coraz więcej przekształtników energoelektronicznych (systemy fotowoltaiczne, instalacje ładowania pojazdów elektrycznych, układy napędowe o regulowanej prędkości obrotowej silnika), a mają one wpływ na dobór typu wyzwalania wyłączników różnicowoprądowych (AC, A, F lub B). W obwodach, w których pojawia się prąd różnicowy zawierający składowe o częstotliwości innej niż 50 Hz, może być konieczne zastosowanie wyłącznika różnicowoprądowego typu F. W artykule omówiono wyniki badań progu zadziałania tego typu wyłączników różnicowoprądowych przy prądach różnicowych o częstotliwościach innych niż 50 Hz. Przedstawiono również reakcję wyłączników różnicowoprądowych typu F na pomiar impedancji pętli zwarciowej wykonany dwoma miernikami różniącymi się czasem przepływu prądu pomiarowego. Uzyskane wyniki wskazują, jaki należy dobrać miernik, aby nie następowało zbędne wyzwalanie wyłączników różnicowoprądowych typu F podczas tego pomiaru

Unmanned Aerial Vehicle (UAV) applications are extended extremely. Some applications need to use several UAVs for a general mission which can be considered a UAV fleet. One of the important characteristics for the evaluation of a UAV or UAV fleet is reliability. There are studies in which methods for analysis of their reliability are considered. Reliability analysis of UAV fleets is less frequently studied, although a single UAV cannot be performed in many applications and requires the involvement of multiple UAVs. Typically, this analysis is based on evaluating two states as operational/functioning and faulting. This paper proposes a new method to calculate the availability of a UAV fleet as one of the reliability characteristics. Unlike well-known UAV fleet analysis approaches, in this paper, the availability is studied based on a mathematical model of a Multi-State System (MSS). MSS allows us to examine more than two states (operational and faulty) of the system, so this analysis is more detailed. In this paper, based on MSS, the analysis of various topologies of UAV fleets is implemented. This mathematical model is used for the analysis and evaluation of topologies of homogeneous and heterogeneous UAV fleets, which can be irredundant or redundant hot stable systems. The interpretations of different topologies of fleets as typical structures of MSS (series, parallel, $k$ -out-of- $n$ ) are considered. New mathematical definitions of the availability of UAV fleets of different topologies based on MSS structure function are proposed. These definitions allowed us to consider the influence of the number of UAVs on the UAV fleet availability and compare the availabilities of considered topologies of fleets.