Temperature sensor calibration in the majority of measurement laboratories is performed on the ground of measurement procedures. The procedures specify the timespan for the temperature of the tested sensor to stabilize. In practice, the fact of time constant increase above expectations can be observed. This results from the method of operation, time of use, and level of contamination of individual sensors. The paper proposes a method to optimize the calibration process of resistance temperature sensors based on the measurement of the time constant and, on this basis, to determine the sensor stabilization time during calibration.

The rapid development of prosumer renewable energy sources (RESs) observed in Poland in recent years causes problems in distribution networks such as current amplitude and voltage asymmetry increases, power and energy loss increases, and reverse power flows, and related are voltage control problems, deterioration of energy quality, etc. Moreover, in the case of planned repair/maintenance works in the network and the need to supply energy consumers in an islanded MV grid, the problem of the correct operation of such a subsystem appears. This occurs when the power production by the prosumers’ energy sources at a given moment exceed the power consumption. In such a case, reverse power flows occur in MV/LV transformers, i.e., from the LV network to the MV network. This causes reverse power flow to the diesel generator, leading to its shutdown and, in extreme cases, to damage. The solution to this problem is to use a mobile system equipped with energy storage in addition to a diesel generator and an LV/MV transformer. An additional problem in the case of using a mobile system (diesel generator) to power an MV island is the islanded MV network grounding. Grid islanding changes the earth fault current and electric shock voltages. In general, MV networks in Poland operate as compensated, i.e., grounding transformers are used, the star point of which is grounded by a compensation choke. Unfortunately, in the case of powering an MV island from a mobile system, there is no real possibility of grounding the star point of the LV/MV transformer used there. This article proposes an algorithm of a diesel generator with an energy storage selection, including electric shock protection requirements verification, for the use in suppling energy via an islanded MV network.

Ship’s low voltage power supply grids with isolated neutral point of the power source are widely used in marine engineering. They can form a potential shock hazard in some specific operational state, when grid capacitance measured against ship’s hull exceed critical value. This paper presents analysis of selected models of body impedance in the assessment of electric shock possibility in the ship’s power supply grids. Main goal of the analysis is to find a relation between ground capacitance and potential shock current in onboard electrical grids with isolated neutral point of power source, using different body impedance models. The results from the simulations in various configurations are presented and analysed. The findings highlight possibility of electrical shock in isolated neutral point networks with high ground capacitance.

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.

Nonlinear and periodically switched receivers can cause distortions in current and voltage waveforms within power systems. The growing use of renewable energy sources introduces electrical energy into the system through power converters, which often produce voltages that approximate a sinusoidal waveform rather than being perfectly sinusoidal. This trend poses increasing challenges in designing new systems and managing existing ones. A proper description and interpretation of the physical phenomena associated with non-sinusoidal waveforms have become increasingly important. This paper presents simulation models of power circuits using non-sinusoidal signals and discusses the energy transfer that occurs within them. It also outlines current computational methods based on circuit theories as they apply to these systems. The results from the calculations and simulations in various configurations are compared with data obtained from real objects. The findings highlight fundamental inaccuracies in the methods used and potential errors arising from computer simulations.

The majority of studies concerning power system analysis is based on computer software and mathematical modelling. Such possibilities are provided by a wide range of engineering and research software including MATLAB/Simulink. Presented work focuses on Simulink library usage for analysing voltage distribution and power flow along typical radial electrical grid and their validation using hardware power system simulator. During the studies four different models of grid were designed, using four tools provided by Simulink: Simulink time domain simulation, Specialized Power Systems time domain simulation, Simscape Load Flow and Specialized Power Systems Load Flow. Analytical analysis, as a sort of another verification, has also been carried out. The obtained results prove that all models in general properly depict the test grid configured on the hardware simulator. However, some discrepancies in the outcome can be observed indicating, that Simscape Load Flow tools are more reliable regarding to load flow analysis specific. The paper is a sort of report describing identified advantages and disadvantages of tools provided by MATLAB/Simulink and their potential limitations in terms of load flow analysis.