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Accurate modeling and simulation of electric field transients in HVDC cables is an important support to optimize insulation system design and to evaluate the influence of voltage transients and steady-state conditions on accelerated ageing mechanisms and insulation reliability. Traditionally, field models considering time-independent permittivity and conductivity are used, but this approach neglects polarization mechanisms and charge trapping-detrapping phenomena. This article includes polarization dynamics in the field model and shows that its impact on transient electric field simulations in HVDC paper-insulated cables can be significant. A method is presented to infer the model parameters from experimental polarization and depolarization current measurements.

This article explores the impact of belt looseness on electrical and mechanical quantities of a system driven by an induction motor and a belt-pulley transmission. The effects of this defect, for example the belt slipping or the apparition of spectral signatures in some measurements, are first investigated under steady state operation. Transient state tests are then performed to analyse, in the time domain, the system response to a step of the speed reference. The behaviour of different variables (slip,speed, currents, etc.) is studied for different health conditions and the increase of the belt looseness clearly impact the electric and mechanical variables’ waveforms. The experimental tests carried out in this study, under steady or transient state, show promising results for the diagnosis of belt degradations. Perspectives of this work are therefore detailed at the end of this paper.

In Robot Assisted Minimally Invasive Surgery, discriminating critical subsurface structures is essential to make the surgical procedure safer and more efficient. In this paper, a novel robot assisted electrical bio-impedance scanning (RAEIS) system is developed and validated using a series of experiments. The proposed system constructs a tri-polar sensing configuration for tissue homogeneity inspection. Specifically, two robotic forceps are used as electrodes for applying electric current and measuring reciprocal voltages relative to a ground electrode which is placed distal from the measuring site. Compared to the other existing electrical bioimpedance sensing technology, the proposed system is able to use miniaturized electrodes to measure a site flexibly with enhanced subsurfacial detection capability. In this paper, we present the concept, the modeling of the sensing method, the hardware design, and the system calibration. Subsequently, a series of experiments are conducted for system evaluation including finite element simulation, saline solution bath experiments and experiments based on ex vivo animal tissues. The experimental results demonstrate that the proposed system can measure the resistivity of the material with high accuracy, and detect a subsurface non-homogeneous object with 100% success rate. The proposed parameters estimation algorithm is able to approximate the resistivity and the depth of the subsurface object effectively with one fast scanning.

The topology of a device will determine the impact said device has on the grid and how immune that device is for disturbances in the grid. LED lamps are very commonly used devices, with different topologies available in the market, each topology showing different behavior when connected to a grid. For power quality studies, it is important to classify LED lamps, without breaking them to know the topology. Several classification methods are found in the literature with this purpose. In this paper, four methods from different papers for classifying LED lamps have been applied to a group of 21 LED lamps with active power consumption below 25 W. It has been observed that the applicability of the methods may lead to a gap of knowledge needed for classification, leaving space for personal criteria when classifying, that can be afforded using unsupervised Machine Learning. Two unsupervised Machine Learning methods were applied using the electrical parameters and statistics proposed in literature. Validerad;2023;Nivå 2;2023-07-12 (sofila)

Most of standard current probes are intended for the measurement of medium or higher currents. Usually, due to limited dynamic range, characteristic sensitivity and inner noise of the probe, it is hardly possible to measure currents lower than 100 mA. The paper deals with the possibility to extend the dynamic range of the current probe by an additional external lock-in amplifier. The paper describes the principle of the lock-in amplifier in general and design of the laboratory fixture of lock-in amplifier based on AD630 circuit as well. The designed amplifier was used to condition the output of the Agilentll46A current probe. The experiment is described in detail. The results show that thanks to the lockin amplifier the currents even lower than 1 mA can be easily detected.

In power systems, the programmable numerical differential relays are widely used for the protection of generators, bus bars, transformers, shunt reactors, and transmission lines. Retrofitting of relays is the need of the hour because lack of proper testing techniques and misunderstanding of vital procedures may result in under performance of the overall protection system. Lack of relay’s proper testing provokes an unpredictability in its behavior, that may prompt tripping of a healthy power system. Therefore, the main contribution of the paper is to prepare a step-by-step comprehensive procedural guideline for practical implementation of relay testing procedures and a detailed insight analysis of relay’s settings for the protection of an Extra High Voltage (EHV) auto transformer. The experimental results are scrutinized to document a detailed theoretical and technical analysis. Moreover, the paper also covers shortcomings of existing literature by documenting specialized literature that covers all aspects of protection relays, i.e., from basics of electromechanical domain to the technicalities of the numerical differential relay covering its detailed testing from different reputed manufacturers. A secondary injection relay test set is used for detailed testing of differential relay under test, and the S1 Agile software is used for protection relay settings, configuration modification, and detailed analysis.

Beam diagnostic and especially beam current measurements represent a key aspect in the production of a high-quality beam. Due to the known interplay between beam current and beam and plasma properties, many solutions have been addressed to solve this need. Although precise beam current measuring systems exist, they cannot provide noninvasive solutions for the measurement of very low-frequency currents in electron cyclotron resonance ion source (ECRIS) beamline, with a range from tens to hundreds of microamperes. To address the above-mentioned needs, this paper proposes an indirect measurement methodology based on the estimation of the magnetic field produced by target current exploiting a residence time difference fluxgate and a flux concentrator (a mechanical structure able to constrain produced magnetic field in a given area). The main advantage of this approach is related to the possibility to perform a noninvasive current measurement. An optimal geometry for the flux concentrator has been investigated by using a finite-element method analysis that has led to the definition of a minimum value of the magnetic field generated by the minimum value of the target current, around $5.0~\mu \text{A}$ , equal to 3.07 nT. To assess the solution, an experimental setup, miming real magnetic flux intensity inside ECRIS beamlines, has been realized. The measuring strategy has a magnetic resolution of 1 nT and a current resolution of $1.6~\mu \text{A}$ , that is, in line with requirements. Results obtained demonstrate the suitability of the measurement system for the specific application addressed in this paper, both in terms of operating range and resolution.

Geomagnetically induced currents (GICs) are referred to the quasi-DC current flows in power networks, driven by complex space weather-related phenomena. Such currents are a potential threat to the power delivery capability of electrical grids. To mitigate the detrimental impacts of GICs on critical infrastructures, the GICs should be monitored in power systems. Being inherently DC from the power frequency point of view, the components of GICs are, however, challenging and costly to monitor in AC power grids. This paper puts forward a novel methodology for the real-time estimation of GICs in power transformers. Such aim is attained by means of an extended Kalman filter (EKF)-based approach, mounted on the nonlinear state-space model of the transformer, whose parameters can be derived from standard tests. The proposed EKF-based algorithm employs the available measurements for the transformer differential protection. The proposed approach, relying on the differential current, can properly deal with the external sources of interference like harmonic excitation and loading. The EKF-based estimator presented is validated by simulation and experimental data. The results verify the ability of the proposed approach to robustly estimate the GIC level during various operating conditions.

Penetration of DC networks is rapidly increasing in modern power systems. As transient behavior of DC grids is different from that of AC ones, AC grid protection schemes might not be applicable to protect DC networks. Exact fault location is vital for protection of DC networks to reduce repair cost and achieve fast power recovery. This paper proposes a novel topology independent multi-terminal DC scheme to identify fault section and location for DC transmission systems. Voltage and current signals measured at the terminals are analyzed by the least squares error (LSE) algorithm. Then, the proposed scheme uses low frequency components of the signals to locate DC faults offline. Unlike some other methods, it does not require sophisticated sensors and hardware to capture very high frequency content of the signals. Hence, the proposed scheme can be implemented in practice without additional measuring infrastructure. The performance of the proposed scheme is evaluated under various fault conditions for different topologies of DC networks in both overhead lines and cables. Numerous simulations carried out demonstrate that the proposed scheme is quite accurate and provides excellent performance under different fault resistances, sections, and locations.

International audience; This paper considers a small embedded planar antenna in a square-shaped terminal of 25 cm2 at a frequency band near 900 MHz, intended for long-range communication. This paper aims to shows how the Q-factor bounds can be used to predict the performance of such an antenna. Both to determine the optimal bandwidth and the variations in the total efficiency but also to help to inspire the antenna design shape. The choice of shape and position impacts both bandwidth and efficiency. The latter is illustrated by a center-edge positioned folded inverted F-antenna with higher efficiency, as compared to, a more bandwidth optimal meander antenna at the corner. Fabrication and measurements show that the corner positioned antenna is close to bandwidth optimal, and also that it and the associated optimal current have a similar radiation pattern.

The following paper presents advanced methods for evaluating the reliability of ADAS module readings, based on an analysis of the transient supply current. Changes in the transient current waveform occur due to environmental conditions and damage to a module's inner circuitry. Specific deviations in the waveforms may indicate a certain event – either internal or external. This paper presents how to successfully distinguish certain anomalies using artificial neural network-based classification algorithms without having to interfere with the module's internal circuitry. DOI: http://dx.doi.org/10.5755/j01.eie.24.3.20944

Accurate switching device characterization is necessary for effectively utilizing the technological ad-vantages of Silicon Carbide (SiC) Power Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) over their Silicon (Si) Insulated-Gate Bipolar Transistor (IGBT) counterparts. With switching times of few nanoseconds, the unprecedented switching speed of SiC semiconductor devices challenges today's converter and characterization setup designs in regard to parasitic layout inductances for optimal conversion and reliable characterization data. Fur-thermore, active gate driving is a key to unlock the potential of SiC MOSFETs, but requires performance assessment prior to integration. This paper presents a low-inductive test platform for flexible and high-accuracy characterization of fast-switching SiC MOSFETs and active gate drivers evalu-ation. The test circuit delivers high quality characterization data that is comparable with a commercial dynamic power device characterizer. In addition to the conventional hard-switching double-pulse tests with a two-level voltage source gate driver, the test circuit offers soft-switching and gate driver evaluation capability in addition. This test platform is a valuable tool for obtaining reliable characterization data to develop more accurate SiC MOSFET simulation models, and evaluate the combination of gate driver and MOSFET prior to the prototyping phase of a converter.

This paper proposes a novel attack identification mechanism for internet-of-things-based (IoT-based) converter-composed DC grids, where each agent collects its own and neighbours' measurement data for output regulation to meet a preceding power-sharing consensus. Independent from model-free or average-model-based attack detection theories, this mechanism is mainly inspired by converter stitching behavior analysis. Correspondingly, when facing latent signal substitution or agent instigation attacks, through comparing estimated signals with received ones for signal source authentication, both self-sensors and neighbours will be inspected. Eventually, not only can such attacks be detected, but also will respective attack sources be identified. A simulation case of 4-agent 800V IoT-based DC grid on Simulink and a hardware case of 3-agent 90V IoT-based DC grid on dSpace testing platform were investigated. Experimental results revealed that the estimation ratio error kept lower than 3.9% and all attacks were successfully identified, verifying the effectiveness of the proposed mechanism.

Increasing the life cycle of battery packs is one of the most valuable endeavors in modern Li-ion battery technologies, especially for light electric vehicles whose material costs are often significantly determined by the costs of the battery pack. The main aim of the present study is to help manufactureres of LEV's to circumvent the type of discharge profiles that substantially degrade the LEV's battery pack. To this end, this paper describes a measurement setup in which various discharge patterns from light electric vehicles, acquired during actual use of the vehicles, are simulated in a lab environment in order to assess their influence on the degradation of the Li-ion battery packs. The results of these measurements can be used to optimize discharge profiles and improve battery management systems with the aim to extend the Li-ion battery life time.

This paper investigates the influence of external radial load applied to the shaft on bearing fault detection based on vibration or current in induction motors operating under different conditions. This paper details the results of a laboratory trial comprising different test sets on the condition monitoring and fault diagnostic of a six-poles induction motor using a design of experiment (DOE) approach. The dedicated test setup comprises a custom-made fixture that allows us to dynamically vary the radial load applied to the output shaft. The aim is to investigate the effects of radial load on the fault diagnosis of shaft bearings and the interactions between other operating parameters, such as output torque. Specific scalar parameters have been proposed for the condition monitoring of the test motor from vibration and current data. The correct choice of the significant parameters is proven by the strong dependence on the damage returned by DOE results.

Završni rad iznosi teorijski pregled triju osnovnih metoda mjerenja struje u strujnom senzoru. Tri osnove metode koje su opisane su metoda suotpornika, metoda Hallovog efekta i flux-gate metoda. Prvo poglavlje je uvod, u njemu se upoznajemo s temom i zadatkom ovog završnog rada. U drugom poglavlju govori se o strujnim senzorima i njihovom dizajnu. Treće poglavlje govori o prvoj metodi za mjerenje struje tj. metodi koja se bazira na suotporniku. Četvrto poglavlje govori o metodi baziranoj na Hallovom efektu. Peto poglavlje upoznaje nas s flux-gate metodom. The final paper presents a theoretical overview of the basic three methods of measuring current in a current sensor. The three basics of the method described are the co-resistor method, the Hall effect method, and the flux-gate method. The first chapter is an introduction, in which we are introduced to the topic and task of this final paper. The second chapter discusses the expert sensor and their design. The third chapter discusses the first methods for measuring current, that is, a method based on a co-resistor. Chapter four discusses methods based on the Hall effect. Chapter five introduces us to the flux-gate method.

Memristors are being considered as promising devices for highly dense memory systems as well as the potential basis of new computational paradigms. In this scenario, and in relation with data processing, one of the more specific and differential logic functions is the material implication logic also named as IMPLY logic. Many papers have been published in this framework but few of them are related with experimental works using real memristor devices. In the paper authors show the verification of the IMPLY function by using $\mathrm{Ni}/\mathrm{HfO}_{2}/\mathrm{Si}$ manufactured devices and laboratory measurements. The proper behavior of the IMPLY structure (2 memristors) has been shown. The paper also verifies the proper operation of a two-steps IMPLY-based NAND gate implementation, showing the electrical behavior of the circuit in a cycling operation. A new procedure to implement a NAND gate that requires only one step is experimentally shown as well.

Made available in DSpace on 2020-12-12T02:24:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 This paper presents an innovative method for fault location in distribution networks based on classical circuit analyses. Two synchronized and few nonsynchronized pre- and during-fault voltages are required at few buses along with the impedance matrix. A new impedance matrix manipulation procedure is proposed so that the distribution system is investigated in partitions across multiple subsystems. This procedure allows the fault location process to be performed by solving systems of determined equations, making the method more technically accessible. The fault is located by analyzing the voltage sag at the terminal-bus of each subsystem separately. The proposed method is validated on the IEEE 33-bus, 12.66 kV distribution system with/without distributed generation (DG). Simulation results show the robustness and accuracy of the method under several pre- and during-fault scenarios and measurements errors. Electrical Engineering, Sao Paulo State University-UNESP, Ilha Solteira, Sao Paulo Brazil (e-mail: ricardobuzo00@hotmail.com) Electrical engineering, Sao Paulo State University - UNESP, Ilha Solteira, So Paulo Brazil (e-mail: henrique1226@hotmail.com) Electrical Engineering, Sao Paulo State University-UNESP, Ilha Solteira, Sao Paulo Brazil 15385-000 (e-mail: bertequini@dee.feis.unesp.br)

In this paper, a device with swinging plate electrodes has been proposed to measure contact electrification of a liquid sample. The proposed structure is composed of two parallel metallic plates immersed in a dielectric liquid. One of the plates is swinging with a constant frequency in a range from 0.4 to 4 Hz. The paper investigates the dependence in time and frequency of electrode velocity and streaming electrification. The measured current occurs for a very low intermittent velocity of less than 10 mm/s. In this range, the electrification current is around 50 pA. For higher velocities of up to 150 mm/s, the current is at the level of 1200 pA. The time–frequency characteristic using short-time Fourier transform shows no temporal changes in the frequency spectrum. The dependence of electrification on shuttle speed was calculated and it can be approximated with a second order polynomial model with the determination coefficient higher than 0.9. The advantage of the sensor is the ability to measure electrification phenomena without the necessity of having rotating electrodes or having a large volume of flowing liquids.

Information obtained about magnetic anisotropy via neutral point voltage measurements can be used to estimate the position of synchronous and induction machines at all speeds including standstill. Due to its usually high signal-to-noise ratio, this estimation method can be an attractive alternative to approaches that acquire anisotropy information via current measurements. The position estimation method looked at in this paper relies on anisotropy information in the form of position-dependent inductance ratios. These are obtained through measurement of the voltage between the machine’s neutral point and an artificial neutral point during the application of different voltage vectors via a two-level switching inverter. We analyze the conditions placed on and the consequences of implementing necessary modifications to a standard space vector modulation. Five different modified modulation strategies are compared and investigated, including two newly proposed strategies which use only a minimal set of active and zero voltage vectors for measurement of the inductance ratios and therefore allow high utilization of available voltage and a high update rate of the estimated position. Experimental results for three low-power three-phase permanent magnet synchronous machines are presented which suggest that modulation strategies that use active measurement vectors in all three instead of only two axes of the machine are less susceptible to systematic deviations in the position estimation that presumably result from nonlinear machine properties. As part of the machine model, a normalizing inductance variation ratio is introduced, which simplifies expressions and supports the comparison of motors.

Recent advances in Internet-of-Things technology have opened the doors to new scenarios for biosensor applications. Flexibility, portability, and remote control and access are of utmost importance to move these devices to people’s homes or in a Point-of-Care context and rapidly share the results with users and their physicians. In this paper, an innovative portable device for both quantitative and semi-quantitative electrochemical analysis is presented. This device can operate autonomously without the need of relying on other devices (e.g., PC, tablets, or smartphones) thanks to built-in Wi-Fi connectivity. The developed hardware is integrated into a cloud-based platform, exploiting the cloud computational power to perform innovative algorithms for calibration (e.g., Machine Learning tools). Results and configurations can be accessed through a web page without the installation of dedicated APPs or software. The electrical input/output characteristic was measured with a dummy cell as a load, achieving excellent linearity. Furthermore, the device response to five different concentrations of potassium ferri/ferrocyanide redox probe was compared with a bench-top laboratory instrument. No difference in analytical sensitivity was found. Also, some examples of application-specific tests were set up to demonstrate the use in real-case scenarios. In addition, Support Vector Machine algorithm was applied to semi-quantitative analyses to classify the input samples into four classes, achieving an average accuracy of 98.23%. Finally, COVID-19 related tests are presented and discussed.

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The study of electric currents flowing through the airframe is important from an EMC standpoint due to the potential to cause severe aircraft failures. Nevertheless, this is a challenging task because of the complex shape, materials, joints, and apertures found in most fuselages. In this paper, we present the design, simulation, and experimental validation of a test fixture intended to emulate the discontinuity between two fuselage panels mechanically attached. This fixture allows several configurations of the mechanical joint, as well as, the insertion of current probes. The main features of the fixture are analysed, such as bandwidth and frequency performance. Subsequently, simulation and S-parameters measurements are used to investigate the performance of several screwed joint configurations.

This paper analyzes the measurement error, caused by the position of the current-carrying conductor, of a circular array of magnetic sensors for current measurement. The circular array of magnetic sensors is an effective approach for AC or DC non-contact measurement, as it is low-cost, light-weight, has a large linear range, wide bandwidth, and low noise. Especially, it has been claimed that such structure has excellent reduction ability for errors caused by the position of the current-carrying conductor, crosstalk current interference, shape of the conduction cross-section, and the Earth’s magnetic field. However, the positions of the current-carrying conductor—including un-centeredness and un-perpendicularity—have not been analyzed in detail until now. In this paper, for the purpose of having minimum measurement error, a theoretical analysis has been proposed based on vector inner and exterior product. In the presented mathematical model of relative error, the un-center offset distance, the un-perpendicular angle, the radius of the circle, and the number of magnetic sensors are expressed in one equation. The comparison of the relative error caused by the position of the current-carrying conductor between four and eight sensors is conducted. Tunnel magnetoresistance (TMR) sensors are used in the experimental prototype to verify the mathematical model. The analysis results can be the reference to design the details of the circular array of magnetic sensors for current measurement in practical situations.

This paper addresses the distributed estimation problem in a set membership framework. The agents of a network collect measurements which are affected by bounded errors, thus implying that the unknown parameters to be estimated belong to a suitable feasible set. Two distributed algorithms are considered, based on projections of the estimate of each agent onto its local feasible set. The main contribution of the paper is to show that such algorithms are asymptotic interpolatory estimators, i.e., they converge to an element of the global feasible set, under the assumption that the feasible set associated to each measurement is convex. The proposed techniques are demonstrated on a distributed linear regression estimation problem.

This paper explores the feasibility of positioning human by using a single link of multiple-input multiple-output radio channel without ultra-wide bandwidth. While the background channel is measured without the presence of person, the current channel is measured with person(s) standing at several locations in a meeting room facing either in parallel or in orthogonal to the direct line between transmit and receive antennas. The background and current channels are compared by means of the power delay profile, the power angular spectrum, and the estimated plane wave paths. It is found that both the detection and the positioning of person(s) are feasible using the variations of radio channel properties, but extra algorithm and specific deployment are needed for positioning accurately.

In this paper, we present a new switching threshold programmable transimpedance amplifier (TIA) for OLED pixel current measurement system. The TIA is composed of an inverter-based cascode amplifier that achieves DC gain of 87 dB for high linearity. To maximize the current efficiency, novel biasing scheme using series capacitor between two input transconductors is proposed so that the current efficiency of NMOS and PMOS transistors are individually maximized. In order to correct random source voltage variation, the switching threshold range is adjustable with 4-bit resolution implemented in 180 nm CMOS technology, the prototype TIA achieves 4% of current-to-voltage conversion linearity error and 23 mV of switching threshold adjustment range. The implemented differential TIA consumes 165 μW under 3.3 V when operating at 5.2 kHz.

This paper describes a method for the identification of valves’ failure, with the final aim of creating a predictive maintenance architecture. After revising the scientific literature, we selected the electric current, the acoustic emission and the vibration signals as the most promising monitoring techniques. The processes of feature extraction and data fusion have been optimized to detect early symptoms of a failure. Performances of five different machine learning algorithms have been compared. Results, obtained in a specific case study, evidenced that a data fusion process based on vibration and current data, paired with a random forest model allowed a prediction accuracy and a Jaccard index close to 99%.

One possible device authentication method is based on device fingerprints, such as software- or hardware-based unique characteristics. In this paper, we propose a fingerprinting technique based on passive externally measured information, i.e., current consumption from the electrical network. The key insight is that small hardware discrepancies naturally exist even between same-electrical-circuit devices, making it feasible to identify slight variations in the consumed current under steady-state conditions. An experimental database of current consumption signals of two similar groups containing 20 same-model computer displays was collected. The resulting signals were classified using various state-of-the-art time-series classification (TSC) methods. We successfully identified 40 similar (same-model) electrical devices with about 94% precision, while most errors were concentrated in confusion between a small number of devices. A simplified empirical wavelet transform (EWT) paired with a linear discriminant analysis (LDA) classifier was shown to be the recommended classification method.

This paper investigates the impact of current sensors on the measurement of transient currents in fast-switching power semiconductors in a double pulse test (DPT) environment. We review previous research that assesses the influence of current sensors on a DPT circuit through mathematical modeling. The developed selection aids can be used to identify suitable current sensors for transient current measurements of fast-switching power semiconductors and to estimate the error introduced by their insertion into the DPT circuit. Afterwards, this analysis is extended by including further elements from real DPT applications to increase the consistency of the error estimation with practical situations and setups. Both methods are compared and their individual advantages and drawbacks are discussed. Finally, a recommendation on when to use which method is derived.

The inevitable battery ageing is a bottleneck that hinders the advancement of battery-based energy storage systems. Developing a reliable health assessment strategy for battery pack is important but challenging when the joint requirements of computational burden, modelling cost, estimation accuracy, and battery equalisation are considered. This paper proposes a balancing current ratio (BCR)-based solution to realise satisfactory state-of-health (SoH) estimation performance of all series-connected cells within a pack, while the overall reliance on cell-level battery models is also reduced. Specifically, after employing BCR to describe the properties of the balancing process, the voltage-based active balancing is combined into the SoH estimator design for the first time, leading to a weighted fusion strategy for effectively estimating SoHs of all cells within a pack. Hardware-in-the-loop experiments show that even if a parameter-fixed open-circuit-voltage-resistance (OCV-R) model is adopted, the typical estimation error of our proposed solution can still be bounded within only 1.5%, which is 70% lower than that of the benchmarking algorithms. Due to the model-free nature of the integrated voltage-based balancing, the robustness and flexibility of the proposed pack SoH estimation solution are also improved.

This paper discusses the design of a virtual instrument for the analysis of three-phase four-wire circuits. Although the flexibility of the proposed instrument in terms of using different methodologies, this paper focuses on the evaluation of several power terms defined in STD 1459 and FDB (Fryze-Buchholz-Depenbrock) approaches. Laboratory measurements are presented and discussed in order to evaluate the developed instrument and the considered power theories CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

In this paper a new two stage equivalent circuit for corona discharges is introduced. Its aim is to fill the gap between complexity of the circuit and accurate representation of the physical properties, which underlay a corona discharge. The first stage represents the voltage distribution and the occurrence of a discharge with respect to the applied voltage. The second stage models the physical discharge behavior like ionization, number of electrons, positive and negative ions as well as their interaction. The proposed circuit is able to model the different modes of corona discharges, which is experimentally verified. The simulation results are in good agreement with the measured results but cannot compete with simulations based on solving continuity equations. Nevertheless, due to the solely basement on network theory, it provides an easy access to the occurring physical effects during a corona discharge for all electrical engineers.

Electrical low resistive impedance are widely used as resistance standards in metrology laboratories. The aim is to measure a high level of alternative and direct currents (AC and DC) with high accuracy, or to use it as resistive loads suitable for calibrating instruments (such as impedance meters). The use of a low resistive impedance as a standard requires knowledge of its magnitude deviation from DC and its phase angle as a function of frequency. In this paper, we present a design of a low impedance (current shunt) for current measurements at 2 A up to 5 kHz. The structure of the current shunt is defined in a four terminal-pair (with BNC connectors). The relative deviation from DC is less than 0.23 % in magnitude for a current of 2 A up to 5 kHz.

In this paper, we report the first experimental demonstration of the Stretched A linearisation method. The theoretical framework of the method and related simulation studies have been presented in Part I of this work. Here, we apply the method on an 850 nm multimode vertical-cavity surface-emitting laser (VCSEL) specified for operation at 10 Gb/s and demonstrate good quality optical output waveforms with little non-linear distortion at 16 Gb/s using non-return-to-zero (NRZ) modulation. An experimental sensitivity analysis on the generation of the required modulating current components demonstrates large tolerance to parameter mismatch. In addition, it is shown that an adaptive gain scheme can improve the tolerance to the timing offset between the current components. Potential hardware implementations using either analog or digital electronics are also discussed.

Electrical impedance tomography (EIT) has the potential to be an alternative technique to microscopy for many biological applications. It is a novel approach to monitor cell viability, proliferation, or drug response with high temporal resolution in a label-free, non-toxic, and non-destructive way. To limit measurement errors, only time-difference EIT is currently used for biological imaging. Still, the need for constant background reference limits its uses in long-term imaging. A novel equivalent circuit model was developed to analyze the errors in frequency-difference EIT (FDEIT) measurements. Based on the circuit model, the calibrated FDEIT (CFDEIT) method has been derived to compensate the measurement errors. The simulation results show that the voltage variations introduced by the leakage current are correctly modeled by the equivalent circuit. Significant improvements in the image quality are observed in both simulation and experimental results after the application of CFDEIT. It indicates that this paper improves the accuracy of FDEIT and makes it feasible for 3D tissue culture monitoring.

Current transformers for ac power systems applications are usually calibrated by applying sinusoidal currents at different frequencies. The main limitation of this approach is that it does not take into account nonlinearities that may have a significant impact on harmonic current measurement. A more accurate characterization should be based on test currents that are similar to those found in normal working conditions. However, this demands a proper current generator able to generate multitone waveforms with proper accuracy, which is seldom available in laboratories. This paper proposes a simple approach to implement a current generator, based on a waveform generator, a power amplifier, and a transformer which allows boosting the output current capability. Its uneven input–output response can be compensated through linear prefiltering of the desired current waveform. When the generator is employed to reproduce a specific class of current waveforms, such as those typically found in ac distribution grids, an optimal compensation filter can be easily designed. This approach allows canceling systematic nonlinearities introduced by the transformer and the power amplifier, thus significantly increasing accuracy with respect to a conventional frequency response compensation, as confirmed by experimental results.

Pulse width modulation (PWM) of inverter output voltage causes the waveforms of motor phase currents to consist of distinctive ripples. In order to provide suitable feedback for the motor current controllers, the mean value must be extracted from the currents’ waveforms in every PWM cycle. A common solution to derive the mean phase currents is to sample their value at the midpoint of a symmetrical PWM cycle. Using an assumption of linear current changes in steady PWM subintervals, this midpoint sample corresponds to the mean current in the PWM cycle. This way no hardware filtering or high-rate current sampling is required. Nevertheless, the assumption of linear current changes has been recently reported as over simplistic in permanent magnet synchronous motor (PMSM) drives operating with low switching-to-fundamental frequency ratio (SFFR). This, in turn, causes substantial errors in the representation of the mean phase currents by the midpoint sample. This paper proposes a solution for deriving mean phase currents in low SFFR PMSM drives, which does not rely on the linear current change assumption. The method is based on sampling the currents at the start point of a PWM cycle and correcting the sampled value using a model-based formula that reproduces the current waveforms. Effectiveness of the method is verified by simulation for an exemplary setup of high-speed PMSM drive. The results show that the proposed method decreases the error of determining the mean phase currents approximately 10 times when compared to the classical midpoint sampling technique.

This paper reports on the electrical quality of liquid phase crystallized silicon (LPC-Si) on glass for thin-film solar cell applications. Spatially resolved methods such as light beam induced current (LBIC), microwave photoconductance decay (MWPCD) mapping, and electron backscatter diffraction were used to access the overall material quality, intra-grain quality, surface passivation, and grain boundary (GB) properties. LBIC line scans across GBs were fitted with a model to characterize the recombination behavior of GBs. According to MWPCD measurement, intra-grain bulk carrier lifetimes were estimated to be larger than 4.5 µs for n-type LPC-Si with a doping concentration in the order of 10$^{16}$ cm$^{−3}$. Low-angle GBs were found to be strongly recombination active and identified as highly defect-rich regions which spatially extend over a range of 40–60 µm and show a diffusion length of 0.4 µm. Based on absorber quality characterization, the influence of intra-grain quality, heterojunction interface, and GBs/dislocations on the cell performance were separately clarified based on two-dimensional (2-D)-device simulation and a diode model. High back surface recombination velocities of several 10$^5$ cm/s are needed to get the best match between simulated and measured open circuit voltage (V$_{o c}$), indicating back surface passivation problem. The results showed that V$_{o c}$ losses are not only because of poor back surface passivation but also because of crystal defects such as GBs and dislocation.

This paper describes the new single-phase harmonic power standard developed at VTT MIKES. The standard is based on a custom digitizer, which is designed for both laboratory and on-site power metrology. Test signals are generated using a dual-channel arbitrary function generator, a voltage amplifier, and a transconductance amplifier. The reference voltage and current measurements are, respectively, based on a capacitive-resistive voltage divider and two different types of resistive shunt designs. Thorough characterization of the components is presented. Finally, a tentative uncertainty budget is drawn up for frequencies 53 Hz, 1 kHz, 10 kHz on power factors 1.0 and 0.0. The standard has an expanded uncertainty of 32 and 157 μW/VA at 10 kHz for power factors of 1.0 and 0.0, respectively.

The observation of the air gap discharge process is the basis of revealing the physical mechanism of gas discharge and establishing the accurate numerical simulation model. In order to obtain the variation characteristics at different development stages during the air gap discharge processes under positive and negative lightning impulses in this paper, repetitive discharge tests of 1 m rod-plate air gap under standard lightning impulse were carried out in the National Engineering Laboratory (Kunming) for Ultrahigh-voltage Engineering Technology. An improved discharge observation method, using electron-multiplying intensified charge-coupled device (EMICCD) camera, was adopted in the test. A series of discharge spatial-temporal distribution images with nanosecond exposure time and interval time were captured by changing the shooting time delay of the EMICCD in repetitive discharges. The complete discharge development process was reproduced by the image stitching. The development process and the characteristics of the air gap discharge under lightning impulse were analyzed qualitatively. The characteristics of the measured discharge current under the positive lightning impulse were discussed. The testing results and the analysis show that the shape and the development process of the ionization region of the streamer are quite different under different lightning impulses. There are spherical and fan-shaped streamer regions under the positive and negative lightning impulse, respectively. After the streamer runs through the entire gap, the leader develops from the rod electrode to the plate electrode (under the positive impulse) or from both the rod and the plate electrode to the middle area (under the negative impulse). Then the final jump occurs and the gap is broken down. If the streamer still cannot penetrate the entire gap when the applied impulse voltage exceeds the peak, the gap will not be broken down finally.

This paper is concerned with the development and the characterization of an ad hoc transducer for the contactless measurement of a high-intensity direct current (dc) for industrial applications. Specifically, the proposed transducer will be used to measure the oxidation process current in a continuous aluminum coil anodizing line (standard sulfuric acid anodizing). In this oxidation process, the current measurement is required to control the thickness of the obtained aluminum oxide, the most important parameter in determining the overall quality of the process. Starting from the features of the considered process, the transducer must measure, without contact, dc currents up to 13 kA in continuous aluminum strips, whose width and thickness can be up to 1600 and 5 mm, respectively; the mass of each coil can be greater than 4700 kg, and the length can be more than 800 m. The dc current is supplied by an ac/dc converter, but due to the features of the oxidation process, only a fraction of the supplied current flows in the aluminum strip and concurs to the oxidation process; the remaining current flows as a leakage current in the acid solution, creating undesired phenomena and energy losses. In this paper, we propose a low-cost current transducer, whose sensing element consists of an iron core equipped with two windings; the first excites the core, while the second is used to measure the variation in the magnetic saturation of the core due to the dc current to measure. The transducer output is conditioned by an electronic circuit that gives a continuous voltage proportional to the input current. A prototype of the proposed transducer has been designed and implemented; a series of characterization tests has been conducted, and the obtained results are discussed in this paper. The transducer is able to measure up to 13 kA, with an overall accuracy of 1.5% for currents over 11 kA.

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Nowadays, it is becoming essential to extract knowledge from diverse, large scale data-sources. An effective approach to make knowledge accessible and providing the necessary means for efficient reasoning to take place is through the use of knowledge graphs. The process of building knowledge graphs is usually focused on generating meaningful representations. Hence, applying structure to it, which takes into account the existence of different knowledge domains, their depth and breadth is mostly disregarded. This particular shortcoming leads to a loss of valuable information that could else be harnessed to provide various additional functionalities to an application. In other words, enhancing knowledge graphs in such a way that they can be explored similar to how Google Maps presents the world to us. By zooming in and out, different relevant aspects become visible while unnecessary noise is blended out. Granular computing by itself is more of a theorem that highlights potential benefits from the application of fuzzy and hierarchical structures. Little is said on how a potential granular knowledge graph can be built and which existing clustering algorithms can be used for this task. As such, this paper aims to provide (1) an in-depth view of which critical requirements need to be met by an algorithm to establish a granular structure, (2) the process for how different commonly used algorithms are coping with them, as well as (3) an overview that outlines the different steps in the process of establishing a granular knowledge structure. Two approaches are identified as the most promising ones: for low dimensional data, a Growing Hierarchical Self-Organizing Map (with its adaptive behaviour) and, in case of data with high dimensionality, one approach from the projective clustering family, thanks to their capability of finding strong correlation in sub-spaces of the original dimensions., + ID der Publikation: hslu_84069 + Art des Beitrages: Wissenschaftliche Medien + Jahrgang: 2021 + Sprache: Englisch + Letzte Aktualisierung: 2021-07-13 14:30:00

Distribution networks are currently subject to a huge revolution in terms of assets being installed. In particular, the massive spread of renewable energy sources has drastically changed the way of approaching the grid. For example, renewables affected (i) the production of the legacy power plants, (ii) the quality of the supplied energy, decreasing it, (iii) the fault detection and location, etc. To mitigate the significant drawbacks of the renewables’ presence, several intelligent electronic devices have been (and are being) developed and installed among the grid. The aim is to increase grid monitoring and knowledge of its status. However, considering the significant number of nodes of the distribution network, compared to the transmission one, the process of installing new equipment is not effortless and is also quite expensive. This work aims at emphasizing a new concept of distributed monitoring systems, based on the phasor measurement unit’s current measurements, and a controlling algorithm to exploit it. The idea underneath the work is to avoid the out-of-service time needed and the costs associated with the installation of voltage sensors. Therefore, this paper describes an algorithm that exploits measurements from existing equipment and current measurements from PMUs to obtain information on the load and the node voltages. The algorithm is then tested on simulated power networks of increasing complexity and verified with an uncertainty evaluation. The results obtained from the simulation confirm the applicability and effectiveness of the algorithm and the benefits of a current-based monitoring system.

The paper reports the results of the test and modelling activities carried out on large commercial supercapacitor cells at high current. Four commercials cells, with rated capacitance of 3000 F and rated voltage of 2.7 V, are considered. All cells are submitted to consecutive charge/discharge cycles at constant current. A test current in the range 80-130 A is used, which is comparable with the maximum operating current (up to 150 A) that the cells can reach in practical operations. A circuit model of the cells, able to reproduce the most relevant dynamic behavior, with a good compromise between accuracy, simplicity and robustness of the model's parameters, is also developed and validated against the experimental data. It is shown that all the investigated commercial cells are characterized by similar phenomena and comply with the same circuit model. Moreover, it is shown that the circuit parameters of the cells are in the same range and are weakly dependent on the test current. The obtained circuit parameters are accurately reported for all the cells and made fully accessible to users.

With the unprecedented growth of renewable resources, electric vehicles, and controllable loads, power system has been incorporating increasing amount of unconventional generations and loads. As a consequence, significant dynamic and stochastic power flow are introduced into distribution network, requiring high resolution monitoring technology and agile decision support techniques for system diagnosis and control. In this paper, we discuss the application of micro-synchrophasor measurement unit (µPMU) for power distribution network monitoring, and we propose a novel data-driven method, namely Ensembles of Bundle Classifier (EBC), for event detection. The main idea is: multiple classifiers are learned each with a short slot of µPMU measurement generated by a single event. Then their decisions are combined with a “winner-takes-all” scheme. This framework naturally resolves the challenging issue of heterogeneity in the high resolution µPMU data, and significantly outperforms classic data-driven event detection methods. In this paper, the proposed framework is tested on an actual distribution network with µPMUs, and is compared to other state-of-the-art methods. The result justifies the effectiveness of EBC as a promising tool to improve the security and reliability of distribution network.

this paper describes a circuit allowing accurate detection of the continuous (CCM) and discontinuous (DCM) conduction mode boundary. It is suitable namely for very low power integrated DC/DC converters such as the buck or boost. The zero power consumption of this critical block enables to greatly improve the light load power efficiency, and minimize the silicon area. Detection uses a time shift of the power-stage output voltage, which depends on the inductor current value and its polarity. Detector circuit is realized with a digital latch comparator containing only a few digital gates. The paper contains description of the method, example of circuit implementation, and post-layout simulation of integrated detector in 0.13µm CMOS technology, allowing to obtain several mA detection accuracy.

Widespread adoption of electric vehicles (EVs) requires additional safety countermeasures to prevent DC injection from EVs into the AC grid via Electric Vehicle Supply Equipment (EVSE). Moreover, for energy purchase, and even more so for vehicle-to-grid (V2G) services, the EVSE must conduct high precision bidirectional power and energy measurements. This paper introduces operating principles, structure, performance, and cost comparison of three current sensing technologies&mdash, current transformer, shunt and fluxgate&mdash, for metering and protection within an EVSE, concluding with recommendations among those sensors for the most beneficial applications concerning EV charging.

This paper describes the measurement system used to monitor the energy dissipated in the braking rheostat resistors on board a locomotive operating in a DC rail system. The aim of the activity is the accurate estimation of the energy, nowadays wasted, that could be recovered thanks to the implementation of the smart grid paradigm in the DC railway system. To provide metrological reliability to the measured wasted energy, a preliminary identification and estimation of the uncertainty is provided. The target uncertainty of the measurements is 1 %.

Steering motor is of vital importance in UAV’s health-monitoring system, to which its supply current is the most critical characteristic representing health statue of UAV. In order to conduct continuous measuring on the steering motor’s current of large dynamic range, in this paper, a current measurement method is therefore proposed on the basis of twin nonlinear shunt. The proposed method adopts the twin diode as the current sampling device, which not only realizes measurement range and relative constant resolution, but also ensures continuity of the measurement due to the eliminated operation of range switching. The associated diode is used to compensate the temperature of core temperature of the shunt diode, and to make the nonlinear-shunt more adaptive for the case of junction being heated under larger current. The working principle, real-time compensation method and circuit implementation of our method are discussed in detail. Experimental test results suggest that the measurement error of the proposed method is less than 4.5% when the measurement current varies between 10 mA to 10 A, maintaining the relative resolution at an almost constant level, while preventing the conventional method of frequent range switching from generating glitches. In addition to the ensured continuity, information-rich details of the current are sustained, contributing to the UAV’s health-monitoring system. The proposal can also be applied to other applications concerning large dynamic current detection, including, but not limited to, industrial control, motor control, etc.

Recently, the press-pack insulated gate bipolar transistor (IGBT) has usually been used in direct current (DC) transmission. The press-pack IGBT (PPI) adopts a parallel layout of boss chips, and the currents of each chip will be uneven in the process of turning on and off, which will affect the reliability of the device. To measure the currents of each chip, based on the analysis of the principle and equivalent model of the Rogowski coil, this paper puts forward the design scheme and design index of multi-layer printed circuit board (PCB) Rogowski coil with good high-frequency performance, strong anti-interference ability and sufficient sensitivity. With the simulation analysis of Altium Designer and ANSYS softwares, a 1 mm thick, 76-turn integrated four-layer PCB Rogowski coil is designed. Then, adding a composite integrator, an integrated Rogowski coil sensor for measurement of PPI chips currents is designed. The Pspice simulation and the experiment results show that the sensor is fully satisfied with the chip current measurement.