Electrical Elements Research Articles

Strengthening Resilience of Electricity Critical Infrastructure in the Context of Railway Transport

The energy sector is crucial in the critical infrastructure system, since other critical infrastructure sectors are dependent on energy supplies. Electricity infrastructure is one of the key sectors of critical infrastructure and, moreover, this sector has been recognized as uniquely critical. This makes it necessary to ensure a high level of protection of energy sector elements, especially by strengthening their resilience. A power outage would have a negative effect on dependent subsystems of critical infrastructure (e.g. transport). The electricity sector is constantly exposed to negative threats; therefore, it is important that the electricity elements achieve a high level of resilience, which in the critical infrastructure system is defined as the ability to reduce the extent and/or duration of disruptive events, absorb negative phenomena, and adapt or quickly recover from potentially dangerous events. The key output of this paper is the proposal of a procedure for strengthening the resilience of electricity critical infrastructure. By applying tools to strengthen resilience, the element becomes more resilient to internal and external negative phenomena, thereby reducing its vulnerability. This results in the strengthening of the resilience of dependent elements of the railway critical infrastructure.

Influence of CO2 Curing on the Alkali-Activated Compound Mineral Admixtures’ Corrosion Resistance to NaCl Dry–Wet Alternations

In this study, the influence of CO2 curing on the corrosion resistance of reinforced alkali-activated compounds is investigated. Fly ash (FA) and blast furnace slag powder (BFS) are used as mineral admixtures. The specimens were subjected to dry–wet alternations with 3% NaCl, used to simulate a concrete structure under a corrosion environment. The ultrasonic velocity, mass loss rate, and electrical characteristics (such as electrical resistance, AC impedance spectra, and corrosion area rates determined by Tafel curves) are utilized to determine the degree of corrosion. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to analyze the corrosion mechanism. Results show that the corrosion resistance is decreased by the addition of FA but improved by CO2 curing. When CO2 curing is provided, the addition of BFS shows a higher enhancing effect on the corrosion resistance than that of FA. The equivalent circuit diagram of reinforced alkali-activated compound mineral admixtures obtained by AC impedance spectra is composed of three electrical elements (electrical resistance and capacitance in parallel) in series. The X-ray diffraction results show that adding BFS and CO2 curing can decrease the rust’s iron oxides on the steel bars’ surface. Finally, as found in the SEM photos, BFS and CO2 curing can effectively improve the compactness of specimens. Meanwhile, the roughness of hydration is increased by CO2 curing.

Investigation of the Characteristic Thermal Retention Behaviour of Sandwich Glass-Fibre-Reinforced Composite Panels in Electric Oven Designs

The focus of this paper is to experimentally investigate the characteristic heating and cooling behaviours of a sandwich glass fibre reinforced composite panel electric ovens. A portable conventional electric oven with two stack trays for product placement was designed and fabricated for the evaluation. The oven box consists of sidewalls and a ceiling made of glass-reinforced plastic (GRP) with sandwich glass wool insulation. The oven floor has, in addition to the sandwich panel, a ceramic tile plate placed on the chamber floor to separate the electric heating element. The oven characteristic thermal behaviour was obtained as different product load conditions were being simulated. The heat retention ability of the oven is quite impressive making it possible for the water simulated product to remain warm for up to 13 hours with the testing stockpot open and more than 27 hours with the pot covered. Energy is therefore conserved as the oven can be switched off while the product continues to process. The oven cooking efficiency of approximately 39% was obtained under standard stockpot water test. The oven is therefore suitable for both culinary activities and laboratory experiments requiring moderate temperatures.

Расчет температурного поля, создаваемого системой ТЭНов внутри металлического пресса

Работа посвящена численному моделированию системы трубчатых электронагревателей (ТЭНов), внедренных в стальную плиту (пресс), которая покоится на слое инородного материала - дерева или древесноволокнистой плиты МДФ. Целью расчетов является определение количества и мощности ТЭНов, обеспечивающих заданный прогрев пресса. Средняя температура на поверхности соприкосновения стали с МДФ задана, а перепад температур в различных точках этой поверхности не превышает определенного значения, диктуемого особенностями обрабатываемого материала. Результаты расчета внедрены на производстве. The paper is devoted to numerical simulation of a system of turbular electric heating elements that are embedded in a steel plate (a press) basing on a slice of some other material, i.e. wood or MDF. Calculation purpose is to find the number and the power of heating elements that guarantee preselected heating regime of the press. In more detail, average temperature on the contact surface of the press and MDF is given, and temperature drop on this surface must not exceed some value determined by the properties of material under treatment. The simulation results are adopted by a certain company producing wood-fibre boards.

Алгоритм работы устройства минимизации потерь электроэнергии и токовой загрузки электросетевых элементов энергосистемы

Now there is a continuous increase in loads in electric networks that are undergoing aging of electric grid equipment. These factors lead to a large increase in electricity losses in electrical networks, as well as to a decrease in the current-carrying capacity of electrical network elements. Therefore, the issue of the need to minimize the loss of electrical energy, as well as reduce the current load of network elements, in order to increase its throughput, is becoming more and more acute. One of the most effective ways to reduce power losses and reduce the current load of power grid elements is to regulate the voltage at the nodes of the electrical network by means of power-factor correction unit. However, in order to solve the problems of reducing power losses and current loading of network elements using power-factor correction unit, it is necessary to develop and implement new effective means and algorithms for voltage control, which will allow real-time monitoring of the state of the network and voltage control in the network to achieve the goals.

Оценка условий незамерзания жидкости в больших емкостях с локальной схемой обогрева с помощью программы Ansys Fluent

A computer simulation of an operating water storage tank, RGSn-100, with mortise electric heating elements, for specified conditions was carried out using Finite Element Analysis software ANSYS 2021 R1. The ANSYS Fluent software package was used to solve a three-dimensional numerical simulation of natural convective flows of a viscous incompressible fluid and heat exchange processes with local heating and cooling in a large volume. Several approaches were used to select optimal methods describing convective flows in a large volume most accurately with limited resources. The influence of the heating scheme and cold bridges on the heating efficiency and the risk of freezing is considered. The article provides examples of calculations and gives specific instructions for solving problems of natural convection in large volumes using software tools - models, functions, acceptable simplifications.

Model Development of a Hybrid Battery-Piezoelectric Fiber System Based on a New Control Method.

By increasing the application of smart wearables, their electrical energy supply has drawn great attention in the past decade. Sources such as the human body and its motion can produce electrical power as renewable energy using piezoelectric yarns. During the last decade, the development of the piezoelectric fibers used in smart clothes has increased for energy-harvesting applications. Therefore, the energy harvesting from piezoelectric yarns and saving process is an important subject. For this purpose, a new control system was developed based on the combination of the sliding mode and particle swarm optimization (PSO). Using this method, due to the piezoelectric yarn cyclic deformation process, electrical power is produced. This power is considered the input voltage to the controlling system modeled in this article. This system supplies constant voltage to be saved in a battery. The battery supplies power for the electrical elements of smart fabric structure for different applications, such as health care. It is shown that the presence of PSO led to the improvement of system response and error reduction by more than 30%.

Positive/Negative Temperature Coefficient Behaviors of Electron Beam-Irradiated Carbon Blacks-Loaded Polyethylene Nanocomposites.

Polymer-based materials with positive temperature coefficients (PTC) are regarded as potential candidates for electrical heating elements in a wide range of applications, such as wearable electronics, soft robots, and smart skin. They offer many advantages over ceramic or metal oxide-based composites, including low resistance at room temperature, excellent flexibility and processability, and low cost. However, the electrical resistance instability and poor reproducibility have limited their use in practical applications. In this work, we prepared carbon blacks-reinforced high-density polyethylene nanocomposites (CBs-HDPE) loaded with polar additives (polyols or ionomers), which were subsequently subjected to electron beam (EB) irradiation to explore their PTC behaviors. We found that the EB-treated nanocomposites exhibited PTC behaviors, while the untreated samples showed negative temperature coefficients. Further, EB-ionomer-CBs-HDPE showed the highest PTC intensity of 3.01 Ω·cm, which was ∼35% higher than that of EB-CBs-HDPE. These results suggested that the EB irradiation enabled a specific volume expansion behavior via enhanced crosslinking among CBs, polar additives, and HDPE, inhibiting the formation of conductive networks in the nanocomposites. Thus, it can be concluded that polar additives and further EB irradiation played an important role in enhancing the PTC performances. We believe the findings provide crucial insight for designing carbon-polymer nanocomposites with PTC behaviors in various self-regulating heating devices.

Investigation of capacitors and electrical circuit elements performance of magnetic biocomposites prepared by using the hemp biomass

Hemp biomass (HB) was brought into activated hemp biomass (AHB) by chemical technique and all samples were obtained by doping different nanoparticles. Structural, dielectric and magnetic characterizations for all samples were performed by using the XRD, FTIR, SEM, EDX, LCR Meter and PPMS at room temperature. The characteristics of both hemp biomass and nanoparticles in the structures of these samples were examined in detail. In addition to HB and AHB samples, the contribution of lignin and pectin characteristic bands to conductivity was investigated in AHB samples doped with Fe3O4, MgFe2O4 and SrFe2O4 nanoparticles. It has been determined that homogeneously dispersed nanoparticles contribute to surface area, crystallization and conductivity and these samples are technological products. It was determined that the samples could be used as batteries, and two electrical circuits simultaneously connected to the lignin and pectin structures of the activated hemp biomass (AHB) doped with different types of nanoparticles were obtained from the Smith-Chart diagram.

Microplasma-sprayed multilayer coatings for electric heating elements

Abstract The paper presents new results on the application of microplasma spraying (MPS) for manufacturing electric heating elements (EHEs) consisting of a St3 steel plate (the substrate) with a sprayed electrically insulating Al2O3 sublayer (400±50 μm thick) and TiO2 electric heating tracks (4 mm width; 150±50 μm thickness). Measurements of the temperature of the multilayer coating with a thermal imager enabled determination of the temperature distribution over the surface of the EHE. The electric strength and conductivity tests showed the efficiency of the sprayed EHEs up to a temperature of 200°C. The results of analysis of the causes of material losses during MPS of electric heating tracks (TiO2) are presented, and the optimal parameters for efficient MPS of coatings in the form of narrow tracks on steel substrates are determined. Using regression analyses, the equation for the influence of MPS parameters on the coating transfer efficiency (CTE) is obtained. Process parameters such as the electric current and the plasma-forming gas flow rate have been found to have the greatest influence on the CTE. In the experiment, a high efficiency of the sprayed material during MPS of electric heating tracks of TiO2 powder was established (the maximum CTE reached 89%), which indicates the prospects for using MPS technology in the production of EHEs for DC electric heating and for maintaining the temperature of product surfaces up to 200°C.

Electromagnetic Interference from Heated Gloves May Compromise Avalanche Transceiver Function.

Rapid location of avalanche victims by companions using avalanche transceivers is of utmost importance to prevent asphyxiation. The objective was to determine whether electromagnetic interference from heating elements in gloves worn by rescuers or victims can impair the receiving or transmitting function of avalanche beacons. Commercially available heated gloves from 3 different manufacturers were examined during a simulated search with 3 common brands of avalanche transceivers. Distance to target beacon at first signal detection and accuracy of direction to target, as indicated by the arrow from the direction indicator, were evaluated. Preliminary tests showed that transmitting and receiving signals are degraded by electromagnetic interference caused by rectangular pulses emitted by activated heating elements. Field tests revealed significantly reduced distances of first signal detection when heated gloves were turned on near receiving avalanche transceivers (P<0.001; Wilcoxon signed-rank test). Decreased distance to target beacon ranged between 1.9 m (5%) and 41.5 m (94%) at first detection, depending on the avalanche transceiver used. Avalanche transceivers are susceptible to electromagnetic interference from gloves with electric heating elements. We do not recommend using heated gloves when performing a transceiver search for avalanche victims because it can lead to a delay in rescue.

Investigation on temperature uniformity control of titanium extrusion in hot stretch bending process

Regarding to the impact of temperature on springback in hot stretch bending (HSB) process, this work proposed an investigation on temperature uniformity control of titanium extrusion in HSB process based on the mould which can be elevated by resistance heating. Prior to the HSB test, mould structure was designed to fit for resistance heating. Coupled thermal electrical structural finite element model of HSB process was created in ABAQUS. Resistance heating and HSB tests were performed using displacement control electrically assisted stretch bending machine. The results of simulation indicate that the temperature uniformity of titanium extrusion and the forming accuracy of curved part can be effectively improved by increasing the initial temperature of mould. At last, the curved part of titanium extrusion with L-section was achieved, and the forming accuracy of which was measured and evaluated.

Performance Enhancement of Vehicle Mechatronic Inertial Suspension, Employing a Bridge Electrical Network

Inerters, a new type of mass element, have been successfully applied in various fields, such as in automotive and civil engineering. The development of a new element, named a mechatronic inerter, which consists of a ball-screw inerter and permanent magnet electric machinery, proves the feasibility of adopting electrical element impedances to simulate corresponding mechanical elements. In this paper, the structures of the bridge electrical network and series-parallel electrical network and their impedance characteristics are first introduced. Then, a seven-degree-of-freedom vehicle model is established. In addition, by comparison with passive suspension, a bridge network and a series-parallel network with various basic topologies are used to improve the vibration isolation performance of mechatronic inertial suspension, and the advantages of the bridge network (a) are demonstrated. Finally, a bridge electrical network (a) was designed and a real vehicle test was carried out. The test results showed that the mechatronic inertial suspension based on the bridge network (a) was superior to the passive suspension; the RMS (root-mean-square) values of the suspension working space and dynamic tire load of the left rear wheel suspension were reduced by 21.1% and 6.3%, respectively; and the RMS value of the centroid acceleration was improved by 1.8%.

Memristor synapse-coupled piecewise-linear simplified Hopfield neural network: Dynamics analysis and circuit implementation

Electromagnetic induction current is generated between the adjacent neurons in neural network caused by the existence of membrane potential difference. Memristor is the fourth fundamental electric element, which can mimic the behavior of neural synapses and simulate the electromagnetic induction effect. In this paper, in order to simplify practical implementation, the commonly used hyperbolic tangent activation function of Hopfield neural network (HNN) is replaced by a piecewise-linear function, and a simple bi-neuron-based memristor synapse-coupled HNN is proposed. Theoretical analysis and numerical simulation results illustrate that the memsirstive HNN possesses five equilibria including one unstable saddle-focus, two unstable saddle points, and two stable node points (or node-foci). Local attraction basins and phase plane plots show that the memristive HNN model behaves multistability of coexisting chaos, periodic limit cycles, and stable point attractors. Various system dynamical behaviors affected by parameters of the piecewise-linear activation function, memristor coupling strength, and initial conditions of the neurons are investigated by numerical simulations. Furthermore, an analog circuit of the memristive HNN model is simply designed, which is easier for hardware implementation as the piecewise-linear activation function can be implemented by simple op-amp-based module. Finally, the experimental results verify the correctness of the design and analyses.

Favorable Start-Up behavior of polymer electrolyte membrane water electrolyzers

Dynamically-operated water electrolyzers enable the production of green hydrogen for cross-sector applications while simultaneously stabilizing power grids. In this study, the start-up phase of polymer electrolyte membrane (PEM) water electrolyzers is investigated in the context of intermittent renewable energy sources. During the start-up of the electrolysis system, the temperature increases, which directly influences hydrogen production efficiency. Experiments on a 100kWel electrolyzer, combined with simulations of electrolyzers with up to 1MWel, were used to analyze the start-up phase and assess its implications for operators and system designers. It is shown that part-load start-up at intermediate cell voltages of 1.80 V yields the highest efficiencies of 74.0 %LHV compared to heat-up using resistive electrical heating elements, which reaches maximum efficiencies of 60.9 %LHV. The results further indicate that large-scale electrolyzers with electrical heaters may serve as flexible sinks in electrical grids for durations of up to 15 min.

Physical Interpretation of Mixed Ionic‐electronic Conductive Polymer‐coated Electrodes by a Simple Universal Impedance Model

AbstractA simple equivalent electrical circuit is used to obtain the physical parameters of electrical circuit elements from measured electrochemical impedance spectra. This model consists of four circuit elements with a clear physical meaning for each of the elements. Compared to complex models with multiple constant phase elements or Warburg impedances, our model is suitable for extracting physical values for important electrode parameters with low errors. The feasibility of the model was shown by investigating pure metal or polymer‐coated electrodes. Here, gold electrodes were coated either with Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT : PSS), Polypyrrole:poly(styrenesulfonate) (PPy : PSS), or (PEDOT/PPy) : PSS by means of electropolymerization. The model could demonstrate the ionic‐electronic differences such as the ion accessibility of the differently coated electrodes. To prove the correctness of the model, the obtained results were compared to the literature.

Research on structural type of two-way connection fittings based on valve hall

Based on the research on the structural type of valve hall two-way connection fittings, with the sustained and rapid economic growth, the power demand of various industries increases. While accelerating the construction of UHV backbone power grid, improving the transmission capacity and transmission quality of the existing power grid has become a top priority. In ± 800kV UHV DC transmission project, the rated current is up to 6250A, and the current carrying capacity of valve hall fittings in converter station increases accordingly, which puts forward higher requirements for heat resistance and reliability of fittings. Therefore, it is very necessary to study the operation reliability of valve hall fittings in converter station. In this paper, two structural types of two-way connection fittings are analyzed. The temperature field of two-way connection fittings is simulated by using the electric thermal coupling finite element analysis method. At the same time, the high current temperature rise test is carried out, and the temperature at the key position of two-way fittings is measured by thermocouple. The high current temperature rise test and simulation results show that when 6250A current is applied, there is uneven shunting between the two specimens. Under the condition of meeting the temperature rise limit, the flow through of aluminum strand connection mode is more uniform than that of aluminum row connection mode. The test results are consistent with the simulation results, which provides a reference for the subsequent design of valve hall fittings.

Low-frequency rotating and alternating magnetic field generators for biological applications: Design details of home-made setups

We describe a setup able to generate a rotating or alternating low-frequency (up to 10 Hz) magnetic field (up to 120 mT) for biological applications inside a 6 cm in diameter and 5 cm in height cylindrical space. It is suitable to insert several Petri dishes for cell death experiments and mice for in vivo ones. Since a particular attention was given to the field homogeneity, it is based on a six-pole electromagnet. The characteristics of the field are changed by varying the phase, amplitude or frequency of the electrical currents going through the coils, using a micro-controller-based human–machine interface and a RL chopper, which is described. The results of the magnetic simulations run to optimize the global design are provided. The cooling of the electromagnet is done using a chiller, and the sample temperature regulation using an air blower. All details on the mechanical, electrical and electronic elements, on the mounting, and on the programing are provided, so the setup can be reproduced. Suggestions for a further improvement of the electrical efficiency are given. This setup has already been used to demonstrate the possibility to kill cells using targeted magnetic nanoparticles and low-frequency magnetic fields.

FEM simulation‐based development of a new tunable non‐magnetic RF high voltage capacitor for the new generation of MRI

Using Radio Frequency (RF) waves, magnetic resonance imaging (MRI) systems can make detailed images of human organs for accurate diagnostic processes and disease detection. The overhaul of certain electronic components has become necessary to keep up with the progress of MRI systems. Among the components responsible for image quality, the adjustable non-magnetic capacitors, also called trimmers, are of great importance. The purpose of this paper is to suggest a new design of a trimmer using non-magnetic materials, able to hold a high voltage ( >3 kV) and reach a resonance frequency above 100 MHz. Constructional analysis performed on existing commercial trimmers, combined with the electrical Finite Element Method, were carried out to propose a prototype matching the desired specifications. A dielectric shield surrounding the electrodes was sized to ensure voltage withstand. Moreover, the rotor and the worm-and-gear set were joined together to combat the vibrations generated by the MRI system. The present study includes the modelling step of the component by numerical simulation, the manufacturing, the electrical performance characterization, and the mechanical solution for tuning capacitance. The final prototype combines electrical performance corresponding to the required specifications in particular a high breakdown voltage (39.7 kV) and a resonance frequency (130 MHz).

Detecting mechanical indentation from the time constants of Li-ion batteries

Lithium-ion batteries pose severe hazards if their safety is compromised. Previous work has shown that mechanical damage to the battery may not affect its voltage, capacity, or other primary specifications. Therefore, currently, there is no method to check the integrity of battery cells inside an electric vehicle battery pack once it has been subjected to a shock or impact. Here, we report a method to detect mechanical damage to Li-ion cells from their electrical response. We formulate the distribution function of relaxation times (DRT) by a series of passive electrical elements consisting of inductors, resistors, and capacitors. Using our DRT formulation and criteria, we show that the indented cells have substantially different high-frequency time constant characteristics than the control group. This non-invasive method has the potential for detecting hazardous mechanical damage to the batteries of electric vehicles after a road crash or impact landings of drones.