Variation Of Electrical Parameters Research Articles

Response of variation of electrical control parameters to coatings prepared in organo-silicon electrolyte by plasma electrolytic oxidation

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 μm, 83.2 μm and 193.3 μm increased the surface hardness of 6061 aluminium alloy by 6–8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L−1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.

Adaptive passive fault tolerant control of DFIG-based wind turbine using a self-tuning fractional integral sliding mode control

Controlling variable wind speed turbine (VWT) system based on a doubly-fed induction generator (DFIG) is a challenging task. It requires a control law that is both adaptable and robust enough to handle the complex dynamics of the closed control loop system. Sliding mode control (SMC) is a robust control technology that has shown good performance when employed as a passive fault-tolerant control for wind energy systems. To improve the closed control loop of VWT based on DFIG with the aim of improving energy efficiency, even in presence of nonlinearities and a certain range of bounded parametric uncertainties, whether electrically or mechanically, an adaptive passive fault tolerant control (AP-FTC) based on a self-tuning fractional integral sliding mode control law (ST-FISMC) developed from a novel hyperbolic fractional surface is proposed in this paper. ST-FISMC introduces a nonlinear hyperbolic function into the sliding manifold for self-tuning adaptation of control law, while fractional integral of the control law smooths discontinuous sign function to reduce chattering. Additionally, this work introduces an adaptive observer, developed and proved based on a chosen Lyapunov function. This observer is designed to estimate variations in electrical parameters and stator flux, ensuring sensorless decoupling in indirect field- oriented control (SI-FOC) of DFIG. Lyapunov theory is also used to prove stability of states vectors in closed control loop with presence of bounded parameters uncertainties or external disturbances. Simulation results show that the proposed approach offers better performance in capturing optimal wind energy, as well as the ability to regulate active/reactive power and high resilience in presence of occurring parameter uncertainties or external disturbances.

Physical properties of Pr3+ substituted zinc spinel (ZnPrxFe2−xO4) nanoferrites synthesized via sol–gel auto-combustion route

Spinel ferrites, a group of metal oxides, have garnered significant attention in the recent decade due to their high demand for numerous applications, including data storage and microwave device applications. In this context, we studied the effect of different doping concentrations of large Pr ions on the physicochemical properties of spinel lattice, such as dielectric and magnetic properties. In this research, we successfully fabricated a series of praseodymium ion-doped zinc spinel ferrites ZnPrxFe2-xO4 nanoparticles 0.00≤x≤0.20 via a simple and economical sol–gel auto-combustion approach. XRD (X-ray Diffraction Analysis) and FTIR investigations validate the presence of a cubical phase, with the crystallite size varying between 11 nm to 19 nm depending on the amount of Pr present. The Scherrer method, Williamson-Hall analysis (WH), and size-strain plot method (SSP) were investigated the correlation of crystalize size. The SSP approach has a better correlation coefficient than the WH method. Transmission electron microscopy TEM shows that the prepared material possessed the cubic and spherical symmetry. The significant variation in electrical parameters was discussed at an applied frequency ranging from 1 MHz to 3 GHz. The dielectric constant is approximately constant in low-frequency regions then relaxation peaks were observed at nearly 1.4 GHz and 2.2 GHz. The dielectric constant and complex dielectric constant of these samples dropped as the praseodymium content increased. Investigations regarding the magnetic properties were carried out using a vibrating sample magnetometer (VSM) at −23 k Oe to +23 k Oe. Low coercivity and relaxation peaks at high frequencies suggest that this material may be suitable for core materials, microwave technologies and recording media.

A high sensitivity temperature coefficient of the Au/n-Si with (CdTe-PVA) structure based on capacitance/conductance-voltage (C/G-V) measurements in a wide range of temperature

This study focused on revealing the temperature-sensing performance and rudimental electrical-properties of the Au/(CdTe-PVA)/n-Si depending on the temperature via impedance-measurements. The temperature-sensitivity (S) for constant-capacitance drive mode shows two-distinct linear-regions corresponding to low/moderate temperatures. The highest S value was achieved as 15.5 mV/K at 0.60 nF value. Nicollian-Brews and Hill-Coleman methods were applied to determine series-resistance (RS) and density of surface-states (NSS) values. The low RS values and the proper magnitude of NSS demonstrate the high quality and performance of the Au/(CdTe-PVA)/n-Si. Additionally, the electrical parameters obtained from C-2-V plots show almost temperature-independent behavior at moderate temperature regions. The low activation-energy values (Ea) determined via Arrhenius-plot indicate hopping of the trapped electron from trap to trap or conduction band dominates the ac conduction. In conclusion, the variations of electrical-parameters and the high S value consolidate the usability of Au/(CdTe-PVA)/n-Si as a thermal sensor in the low-temperature regions.

Control Strategy of Flywheel Energy Storage System for Improved Model Reference Adaptive System Based on Tent-Sparrow Search Algorithm

This study addresses speed sensor aging and electrical parameter variations caused by prolonged operation and environmental factors in flywheel energy storage systems (FESSs). A model reference adaptive system (MRAS) flywheel speed observer with parameter identification capabilities is proposed to replace traditional speed sensors. The proposed method uses reference and adjustable models to identify the stator resistance and permanent magnet flux (PM Flux) to mitigate the adverse effects of electrical parameter changes on control performance. The Tent chaotic mapping-improved Sparrow Search Algorithm (SSA) optimizes the Proportional-Integral (PI) controller parameters for the dual closed-loop and MRAS speed adaptation laws of the flywheel motor. Moreover, a self-switching parameter identification (SSPI) scheme, which constructs a cost function based on the current, parameter identification, and speed errors, is proposed to prevent inaccuracies in parameter identification. The MRAS observer selects the appropriate PI adaptive mechanism based on the error values, thereby enhancing identification accuracy. Simulink simulations show significant improvements in the rapidity and accuracy of the Tent-SSA optimized MRAS flywheel speed observer, enhancing the stability and robustness of the flywheel rotor. Experimental validation on a constructed FESS platform confirms the feasibility of this method.

Characterizing spatial distribution of ice and methane hydrates in sediments using cross-hole electrical resistivity tomography

Electrical resistivity is an essential parameter for assessing the abundance of gas hydrates and predicting their location. However, imaging techniques are poorly developed for detecting the electrical resistivity distribution of hydrate-bearing sediments. In this study, a cross-hole electrical resistivity tomography (CHERT) array was established in the large-scale simulator for characterizing the spatial distribution of the sedimentary system. Ice- and methane hydrate-bearing sediments were investigated respectively using CHERT. The results show that CHERT effectively observed the significant influence of methane hydrate/ice formation and salt drainage on the variations in electrical parameters. Their formation leads to a sustained increase in average resistivity, while salt ion exclusion leads to an increase in pore water salinity, resulting in a decrease in local resistivity. Moreover, CHERT observed a range of resistivities from a few Ω·m to several thousand Ω·m for ice- and methane hydrate-bearing sediments, which is consistent with the resistivity response of hydrate reservoirs in the field. It is suggested that CHERT can be used for hydrate reservoir detection and combined with acoustic imaging to more accurately characterize the spatial distribution of hydrates. These results contribute to advancing the potential application of CHERT technology in multi-method and multi-scale gas hydrate monitoring initiatives.

Stability Analysis in a Direct-Current Shipboard Power System with Parallel Permanent Magnet Synchronous Generators and Supercapacitor Integration

This paper investigates the small-signal stability of a DC shipboard power system (SPS) with the integration of a supercapacitor. As an efficient energy storage solution, supercapacitors can not only provide rapid energy response to sudden power demand spikes, effectively mitigating load fluctuations, but also enhance the system’s resilience to disturbances. In the context of the parallel operation of two Permanent Magnet Synchronous Generators (PMSGs), the inclusion of supercapacitors may alter the system’s dynamic behaviors, thereby affecting its small-signal stability. This paper develops the small-signal model of SPS and explores the small-signal model under various power distribution strategies in the parallel operation of diesel generator sets. Through the calculation of eigenvalues and influence factors, the system’s oscillation modes are analyzed, and key parameters affecting the stability of the DC distribution system are identified. Furthermore, this paper meticulously examines the specific impacts of electrical and control parameter variations on the system’s small-signal stability. Simulation experiments validate the accuracy of the small-signal stability analysis after supercapacitor integration into SPS.

Evaluation of Saturation Interpretation Methods for Ultra-Low Permeability Argillaceous Sandstone Gas Reservoirs: A Case Study of the Huangliu Formation in the Dongfang Area

Ultra-low permeability argillaceous sandstone reservoirs have become a significant focus for exploration and development. Saturation is a crucial parameter in evaluating such reservoirs. Due to the low porosity, low permeability, complex pore structure, and strong heterogeneity in ultra-low permeability argillaceous sandstone reservoirs, traditional evaluation methods are unable to achieve the required level of interpretation accuracy. To improve the accuracy of gas saturation calculations in ultra-low permeability argillaceous sandstone gas reservoirs, the conductivity characteristics of the ultra-low permeability argillaceous sandstone gas reservoirs in the Huangliu Formation in the Dongfang area, China, were analyzed through rock physics experimental data and geological information. The results revealed the clay content in the study area to range from 6% to 33.4%. Influenced by burial depth and temperature, kaolinite and montmorillonite transform into illite and chlorite, and the cation exchange capacity is not correlated with the clay content. This suggests that the effects of cation-attached conductivity can be ignored. The regional variation in rock electrical parameters is significant. When the lithology coefficient is a = 1, the consolidation index m varies between 1.25 and 1.75. When the lithology coefficient is b = 1, the saturation index n varies between 1.6 and 1.96. Under the influence of high temperature and pressure, the reservoirs in the study area exhibit two distinct characteristics on the capillary pressure curve, fractal dimension, and effective porosity index intersection diagram, (1) In Class I reservoirs, there is a strong correlation between the formation factor and natural gamma, as well as porosity, and a logarithmic relationship between the saturation exponent and the formation factor; and (2) in Class II reservoirs, there is a strong power-law relationship between the formation factor and porosity, as well as a logarithmic relationship between the saturation exponent and formation factor. Based on experimental and logging data, reservoir classification was conducted using core-scale logging and principal component analysis. Additionally, a saturation interpretation model was developed using multivariate regression, based on rock electrical parameters. The actual application results demonstrate that compared to the fixed rock resistivity saturation model, this model has reduced the average absolute error by 5.9%. The calculated values are consistent with the gas saturation analysis of the core at the pure gas section as determined by cable testing sampling. This model meets the requirements of practical production. The study of this interpretation method is of great significance for the formulation of development plans for ultra-low permeability offshore argillaceous sandstone gas reservoirs.

Adaptive Dynamic Surface Control With Disturbance Observers for Battery/Supercapacitor-Based Hybrid Energy Sources in Electric Vehicles

The underlying control in the hybrid energy source system (HESS) of an electric vehicle plays a pivotal role. Uncertainty is unavoidable in system modeling owing to variations in electrical parameters and unknown external disturbances, which inevitably deteriorate the control performance of the HESS. In this study, an innovative adaptive dynamic surface control with disturbance observers (ADSCDOB) is adopted as a control scheme for underlying tracking in the HESS to counteract the adverse effects and improve control accuracy. First, disturbance observers are designed by employing a nonlinear disturbance observer and an extreme learning machine approximator to estimate the mismatched and matched uncertainties. Subsequently, the proposed ADSCDOB scheme integrates the adaptive dynamic surface technique and second-order differentiators to achieve robust control, in which voltage/current references are obtained through the rule-based energy management strategy. The established ADSCDOB obviates the “differential explosion” problem and ensures that the closed-loop system is semi-globally and uniformly bounded. Comprehensive simulations and prototype experiments prove the effectiveness of the ADSCDOB, confirming its satisfactory performance in terms of a fast response, reduced error, and robust stability under hybrid driving conditions.

High sensitivity of semimetal photodetection via Bose–Einstein condensation

AbstractThe discovery of semiconductor has witnessed remarkable strides toward high performance of photodetectors attributed to its excellent carrier properties. However, semimetal, owning to the high carrier concentration and low carrier mobility compared to those of semiconductor, is generally considered unsuitable for photodetection. Herein, we demonstrate an outstanding photodetection in a layered semimetal titanium diselenide (TiSe2) in Bose–Einstein condensation (BEC) state. High sensitivity of semimetal photodetector is realized in the range of visible, infrared and terahertz bands. The noise equivalent power (NEP) has threefold improvement at the visible and infrared wavebands, and significant decrease by one order of magnitude in the terahertz frequencies via BEC phenomenon, attributed to the electrical parameter variation after condensation. The best NEP value in the terahertz frequency is comparable to that of commercial Si photodetector. Our results show another recipe to fabricate high performance of photodetection via semimetal except for semiconductor and pave the way to exploit macroscopic quantum phenomena for optoelectronics.image

Nonlinear state feedback-synergetic control for low frequency oscillation suppression in grid-connected pumped storage-wind power interconnection system

Aiming at enhancing the performance of suppressing low frequency oscillation in grid-connected pumped storage-wind power interconnection system (PS-WPIS), the nonlinear state feedback-synergetic control (NSF-SGC) governor is studied. Firstly, the nonlinear mathematical models of grid-connected pumped storage power system (PSPS) and PS-WPIS are established. Then, the NSF-SGC strategy and macro variable determination method are proposed, and the NSF-SGC governor equation is derived. Furthermore, the action mechanism, regulation and damping characteristics of NSF-SGC governor in grid-connected PSPS and PS-WPIS are explored. Finally, the sensitivity and robustness of NSF-SGC governor are illuminated. The results show that, the proposed NSF-SGC strategy is superior to the proportional-integral, NSF and SGC strategies in regulation quality, and can significantly suppress low-frequency oscillation. The stability of grid-connected PSPS can be prominently improved by selecting smaller linear and time parameters, and a larger absolute value of nonlinear parameter of NSF-SGC governor. The NSF-SGC governor with dual macro variables enhances the damping characteristics of grid-connected PS-WPIS. Appropriate parameters of NSF-SGC governor can enhance the regulation performance of grid-connected PS-WPIS. Noise and parameter sensitivity analysis provide a guidance for improving system stability. The NSF-SGC governor has strong robustness under the variations of hydraulic, mechanical and electrical parameters.

Analysis of degradation of Sb2Se3 thin film solar cells deploying a time-dependent approach linked with 1D-AMPS simulation

In this paper, we have developed a time-dependent model to study defect growth in the absorber layer of Sb2Se3 thin film solar cells. This model has been integrated with the AMPS-1D simulation platform to investigate the impact of increasing defect density at different positions within the Sb2Se3 layer on the electrical parameters of the solar cell. We adopted the Gloeckler standard model for thin films in AMPS to represent Sb2Se3 materials. The study focuses on tracking the degradation of device performance parameters as donor-like mid-gap states accumulate in the Sb2Se3 layer over time. We monitored the variation of key electrical parameters, including efficiency (η), fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Jsc), at three different positions: the interface with CdS, the bulk of the Sb2Se3 layer, and the interface with the top contact. These positions are susceptible to increasing defect density during prolonged operation and irradiation. To pinpoint the most sensitive part of the Sb2Se3 layer to defect accumulation, we divided the layer into three sub-layers. Our simulation results highlight that the CdS/Sb2Se3 interface is the most vulnerable position in the cell when it comes to defect accumulation. The practical implication of this study is that special attention should be given to the CdS/Sb2Se3 interface during material deposition and the development of high-stability Sb2Se3 thin film solar cells.“

OPERATING MODES OF MICRO-HYDROELECTRIC POWER PLANT WITH OUTPUT VOLTAGE STABILIZATION USING INVERTER CONTROL

Link for citation: Lukutin B.B., Shandarova E.B., Popov M. M. Operating modes of micro-hydroelectric power plant with output voltage stabilization using inverter control. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 51-58. In Rus. The relevance. The use of Russia's hydroelectric potential for electricity generation is one of the cleanest and environmentally friendly methods as it does not result in the emission of harmful substances and carbon dioxide into the atmosphere. Moreover, it is a reliable and efficient source of energy as water is a constant source of energy. Hydro turbines are used to convert the energy of water flow into electrical energy, which effectively ensures more reliable and stable production capacity for hydroelectric installations. However, micro-hydroelectric power plants have some drawbacks related to difficulties in ensuring the high quality of produced electricity of autonomous power supply systems. This is due to the fact that the load on the autonomous power supply system can vary not only in magnitude but also in nature, which makes it difficult to maintain a stable level of electricity production. The main goal of the research is to determine the ranges of variation of the output electrical parameters of a non-regulated hydrogenerator operating as part of an inverter-based micro-hydroelectric power station for rural domestic consumers. Additionally, the task is to formulate requirements for the hydrogenerator and power conversion devices in static and dynamic operating modes of the autonomous power supply system. Object: inverter-based micro-hydroelectric power station. Methods: simulation modeling, and programming in Matlab Simulink. Results. A simulation model of an electric power supply system with an inverter microelectric power station was developed. The structure of microelectric power station is proposed, as well as the ranges of voltage changes of the microelectric power station generator are obtained.

Effective Channel Mobility Extraction and Modeling of 10-nm Bulk CMOS FinFETs in Cryogenic Temperature Operation for Quantum Computing Applications

This article presents an extensive experimental investigation of transport properties in 10-nm CMOS Bulk FinFETs at cryogenic temperatures. The split-CV technique is employed to analyze the effective electron and hole mobilities from 300 to 10 K. Temperature and length dependence of effective mobilities is explored taking into account different scattering mechanisms. Hole mobilities were found to be dominated by temperature-independent neutral defects and surface scattering events for short-channel devices at low temperatures; while for electron mobilities, degeneracy effects at the cryo-temperature result in mobility enhancement at high fields. The short-channel devices show significant mobility degradation and weaker temperature dependence which could limit their utility for high-speed cryogenic-CMOS-based circuits. Variation of electrical parameters, such as subthreshold swing (SS), equivalent oxide thickness (EOT), threshold voltage, and effective length with temperature is also discussed. For accurately capturing the effective mobility trends in the specified temperature range along with the threshold voltage and SS trends, the existing BSIM-CMG 110.0.0 compact model equations are modified. The proposed model is validated across different device geometries of the short-channel bulk FinFETs fabricated with industry-standard 10-nm layout rules.

Spectral diagnosis of atmospheric pressure AC argon plasma jet at constant power

In the application of atmospheric pressure plasma jet, because the frequency of AC power supply is limited in the kHz range, the research on the influence of power supply electrical parameters on discharge is basically aimed at the variation of plasma jet characteristics with a single driving electrical parameter ( such as voltage and frequency). However, the discharge power usually changes with a single electrical parameter changing, which can undoubtedly affect the discharge performances including the plasma physical parameters and generated reactive species, resulting in the failure to reflect the influence of the single driving parameter on the discharge. In this study, an atmospheric pressure argon plasma jet is driven by a home-made AC power supply with adjustable pulse modulated duty cycle. And combining the diagnosis of the optical emission spectrum and the optical absorption spectrum, the influences of the voltage, frequency and pulse modulated duty cycle parameters on the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, electron density <i>n</i><sub>e</sub>, and OH radical particle number density of the plasma jet are studied under a constant discharge power of 2 W. The results show that at the constant power, the electron density n<sub>e</sub> does not change with the variation of electrical parameters as the linkage change of electrical parameters will offset the influence of a single parameter on the electron density, while the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle density are most affected by the pulse modulated duty cycle, followed by driving voltage, and the frequency effect is the smallest. Under the constant power, as the frequency decreases, the voltage will increase, and also the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle number density will increase. On the contrary, although the voltage also increases as the pulse modulated duty cycle decreases, the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle number density are all reduced. In addition, the results indicate that reducing the duty cycle of AC power can make the atmospheric pressure plasma jet produce more OH radicals at lower gas temperature. This study provides a new insight into the influence of electrical parameters on the characteristics of atmospheric pressure plasma jets under constant power, and also presents a guidance for choosing power parameters of plasma jets with low gas temperature and high density of reactive species, which is conducive to the development of atmospheric pressure plasma jets in biomedicine and other fields.

Analysis of PV Module Power Loss and Cell Crack Effects Due to Accelerated Aging Tests and Field Exposure

This study compared module power loss for 36 modules that endured various accelerated aging test sequences before installation outdoors on a 10-kWp array in Birmingham, AL, USA for 1.72 to 2.72 years. Twelve modules endured standard IEC 61215 aging tests and 24 endured Qualification Plus (Qual Plus). Modules in each group were further split into two test sequences with different exposures. Electrical parameter variations were analyzed as a function of aging test and field exposure history. Fill factor loss was determined to be the cause of observed decreases in power output during accelerated aging tests, while decreases in both open circuit voltage and fill factor dominated the power loss during subsequent on-sun testing. Quantified cell crack features were extracted via computer vision tools from electroluminescence images and correlated with power loss. Results illustrate that standard aging tests led to negligible cracks, while Qual Plus test sequences yielded more severe cracks. While correlating results from qualification tests with in-field performance degradation parameters remains a challenge, this study provides new insights on specific environmental stressors and crack features that may play a role in power loss. Insights on accelerated aging protocols are discussed.

An effective Hilbert-Huang transform-based approach for dynamic eccentricity fault diagnosis in double-rotor double-sided stator structure axial flux permanent magnet generator under various load and speed conditions

Eccentricity fault in double-sided axial flux permanent magnet generator is very difficult to be detected as the fault generated variations in terminal electrical parameters are very weak and chaotic, especially at the initial stages of the fault occurrence. In addition, one of the most important problems in any fault diagnosis approach is the investigation of load and speed variation on the proposed indices. To overcome the aforementioned difficulty and problems, this paper adopts a novelty detection algorithm based on Hilbert-Huang transform (HHT) which is a time-frequency signal analysis approach based on empirical mode decomposition and the Hilbert transform. It is well suited for reliable fault diagnosis since it is unaffected by transient conditions which make the diagnosis process incur into false alarms. The HHT-based methods has been demonstrated in recent years for rotor and bearing faults detection of induction machine and also for stator faults identification in PM synchronous machines with radial flux structure. This study explores the possibility of applying the technique to the detection of dynamic eccentricity faults in double-rotor double-sided stator structure axial flux permanent magnet generator under variable load and speed conditions. This approach relies on two steps: estimating the intrinsic mode functions (IMFs) by the empirical mode decomposition (EMD) and computing the instantaneous amplitude (IA) and instantaneous frequency (IF) of IMFs using the Hilbert transform. The more significant IMFs are determined by means of Hilbert spectrum, which is applied for accurate eccentricity fault diagnosis. The eccentricity severity can be evaluated based on the IMFs energy value. The theoretical basis of the proposed method is presented. The effectiveness of the proposed method is verified by a series of simulation and experimental tests under different conditions. The results show that the presented approach in this paper is robust against load and speed variations.

Modelling the Effect of Thermal Aging on Transformer Oil Electrical Characteristics Using a Regression Approach

The effect of thermal aging on the electrical properties of the insulating oil used for transformers has been explored in this experimental work. In particular the dielectric dissipation factor, the resistivity and the breakdown voltage have been measured and correlated. The numerical results predicted by mathematical model and those measured in the laboratory have been compared by using a regression analysis. Experiments on thermal aging were performed on insulating oil (Borak 22, Nynas, Austria) during a period of time of 5000-h at three different temperatures. First, the transformer oil’s dielectric dissipation factor, the resistivity and the breakdown voltage are measured after every 500 h of aging. Then, polynomial and exponential regression expressions are proposed for modelling the oil’s electrical parameters variations with thermal ageing at different aging temperatures and periods. The results show that after thermal aging, the resistivity and the breakdown voltage decrease with thermal aging, however, the dielectric dissipation factor which increases. This trend is similar for all different aging temperatures. The numerical results show close agreement with the measured results for all the samples and all studied properties. The regression model presents strong correlation with high coefficients (>94%).

Compact tunable terahertz self-diplexing antenna with high isolation

A tunable terahertz (THz) slotted monopole antenna is implemented with self-diplexing capability. The radiating arms of antenna are filled with the graphene strips. The variation in electrical parameters of graphene alters the surface current distribution in the radiating arms which results in tuning the antenna response through individual input ports. Antenna operates in frequency range 4.75–5.34 THz and 5.57–6.76THz with the application of input at port-1 and 2, respectively which can further be tuned with the reported biasing schemes. The antenna structure utilizes the orthogonal radiating slots which provides high isolation more than 150 dB between the ports in compact antenna geometry. An electrical equivalent circuit is prepared to verify the antenna operation. In addition, antenna offers the peak gain 3.83 dBi at port-1 and 6.06 dBi at port-2 in the operating passband along with the efficiency of more than 80%. Antenna provides the compact geometry with tunable self-diplexing capability and can be suitable for future wireless applications requiring the simultaneous transmit and receive systems.

A Retrofit Strategy for Real-Time Monitoring of Building Electrical Circuits Based on the SmartLVGrid Metamodel

The Internet of things (IoT) paradigm promotes the emergence of solutions to enable energy-management strategies. However, these solutions may favor the disposal or replacement of outdated but still necessary systems. Thus, a proposal that advocates the retrofit of pre-existing systems would be an alternative to implement energy monitoring. In this sense, this work presents a strategy for monitoring electrical parameters in real time by using IoT solutions, cloud-resident applications, and retrofitting of legacy building electrical systems. In this implementation, we adapted the SmartLVGrid metamodel to systematize the insertion of remote monitoring resources in low-voltage circuits. For this, we developed embedded platforms for monitoring the circuits of a building electrical panel and application for visualization and data storage in the cloud. With this, remote monitoring of the consumer unit was carried out in relation to energy demand, power factor, and events of variations of electrical parameters in the circuits of the legacy distribution board. We also carried out a case study with the proposed system, identifying events of excess demand in the consumer unit, mitigating the individual contribution of the installation circuits in this process. Therefore, our proposal presents an alternative to enable energy management and maximum use of existing resources.