Leakage Current Measurements Research Articles

Differentiating the Aging Mechanisms of Si Anodes

Si-based materials have been widely considered promising high capacity anode materials for high energy density lithium-ion batteries. However, the large scale adoption of Si-based anodes is hindered by their rapid performance degradation during cycling and aging. Understanding the fundamental of failure mechanisms is crucial for rational technology development, aiming at extending the cycle life and calendar life of lithium-ion batteries using Si-based anodes. in this work, both OCV aging and high precision leakage current measurement were utilized to characterize the kinetic of parasitic reactions on Si anodes with the presence of various electrolytes. Particularly, the concept of charge balance is adopted to quantitatively describe the electrochemical impact of charge consumption during aging. It was found that the composition of electrolytes pose significant impact on the electrochemical and mechanical stability of solid/electrolyte interphases. Finally, the implication and application of charge balancing for battery development will also be discussed.

Analysis of Transient Current and Heat Flow during Voltage Holds: For 70 wt% Silicon Anode Lithium-Ion Cells

Abstract This study compares the impact of conducting voltage hold measurements with Si/NCA Lithium-ion cells containing 70wt% silicon in the anode and G/NMC811 cells. Silicon is known to present significant volume changes and hysteretic behavior, which has a big impact on the electrochemical behavior of the cells. Isothermal microcalorimetry is combined with voltage hold measurements to investigate the heat flow signals in relaxed (with 30 days storage) and unrelaxed (without storage) conditions. In addition, the influence of relaxation on the voltage hold experiments was investigated in different cell formats: coins, T-cells, and multi-layer pouch cells. The calorimetry results indicate that the equalization of inhomogeneities, and relaxation hysteresis, are more pronounced electrically than thermally, showing a pronounced impact from silicon´s intrinsic material characteristics. When 720 h of storage is introduced, the transient heat flow for silicon and graphite is similar and stabilizes much earlier for coin cells. Moreover, when conducting voltage holds with positive and negative charging currents, the intrinsic hysteresis of silicon impacts the amount of the measured leakage current. For graphite, the leakage currents are very similar.

Switching dynamics in Al/InAs nanowire-based gate-controlled superconducting switch

The observation of the gate-controlled supercurrent (GCS) effect in superconducting nanostructures increased the hopes for realizing a superconducting equivalent of semiconductor field-effect transistors. However, recent works attribute this effect to various leakage-based scenarios, giving rise to a debate on its origin. A proper understanding of the microscopic process underlying the GCS effect and the relevant time scales would be beneficial to evaluate the possible applications. In this work, we observed gate-induced two-level fluctuations between the superconducting state and normal state in Al/InAs nanowires (NWs). Noise correlation measurements show a strong correlation with leakage current fluctuations. The time-domain measurements show that these fluctuations have Poissonian statistics. Our detailed analysis of the leakage current measurements reveals that it is consistent with the stress-induced leakage current (SILC), in which inelastic tunneling with phonon generation is the predominant transport mechanism. Our findings shed light on the microscopic origin of the GCS effect and give deeper insight into the switching dynamics of the superconducting NW under the influence of the strong gate voltage.

Enhanced functionalities of isovalently substituted 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) relaxor piezoceramics synthesized via air quenching

The isovalently substituted lead-free binary solid solution, 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) (BF-BT) (x ≤ 0.07), has been synthesized by solid state ceramic method via air quenching sintering. FTIR and XRD along with Rietveld structure refinement confirmed a pure perovskite phase with a pseudocubic structure (space group Pm3‾m) for developed compositions. SEM revealed a dense microstructure with fine grain size (<1.5 μm) and minimal porosity. XPS analysis reveals predominantly Bi+3 and Fe+3 states, along with oxygen vacancies (VO··). Ferroelectric studies demonstrated a maximum remanent polarization (Pr) of 12.3 μC/cm2 and coercive field EC of 30.95 kV/cm for La3+ concentration of x = 0.03. Overall decrement in Pr can be attributed to dipolar defect-induced random fields reducing the activation barrier for domain nucleation. Leakage current measurement reveals improved resistivity (∼108 Ω cm) up to an applied field of 30 kV/cm. Dielectric measurements unveiled two frequency-dependent anomalies in temperature dependence above room temperature, indicative of diffuse phase transitions. The Vogel-Fulcher model depicted an increasing freezing temperature (from 465 K for x = 0.01–551 K for x = 0.07) and decreasing activation energy (from ∼0.61 eV to 0.07 eV) with increasing La3+ concentration. The estimated diffuseness parameter around ∼2 suggested relaxor behavior. Doping with La resulted in increased dielectric permittivity at 10 kHz (from 4100 to 24066), showcasing the efficacy of site engineering in augmenting the functional properties of BF-BT for high-temperature dielectric and transducer applications.

Correlation between charge and current gain in LGADs treated with IR lasers

This study investigates the correlation between the gain, defined as the increase of measured charge generated from the absorption of incident radiation, and the gain measured as the increase of sensor leakage current in Low Gain Avalanche Detectors (LGAD) before and after neutron irradiations. LGADs exhibit high signal-to-noise ratios for minimum ionizing particles and will be used in high-energy physics experiments, mainly related to timing applications. Transient Current Technique (TCT) measurements were conducted with LGADs and PIN diodes. The electric field screening effect, caused by free and trapped carriers, is identified as the main reason for the differences measured in gain determined from the increase in leakage current and collected charge. These effects are more significant in irradiated LGAD sensors. The experimental results confirm expectations, demonstrating a growing spread between the two measured gains with fluence. The study enables the prediction of charge gain from the leakage current measurements, which are easier to conduct.

Improved Common-Mode Leakage Current Measurement Method for Insulation Condition Monitoring in Distribution Grids

Common-mode (CM) leakage current is an essential insulation indicator for condition monitoring in distribution grids. However, online measurement of CM leakage current is a difficult task in the industry due to the disturbances of far larger load currents. To address this challenge, a novel CM leakage current measurement method based on multi-layer magnetic shield has been proposed in this paper. The analytical solution for the magnetic field around the shield is firstly derived and validated by finite element analysis. Comprehensive comparison with previous single-layer shield design is then conducted for a typical industrial case, proving that an improvement of about 46 dB can be achieved for CM leakage current measurement by the novel design. A sensor prototype has also been developed with optimized parameters and validated by experiments. The effectiveness of the proposed method is proved, with minor CM leakage current accurately extracted from load currents which are 3000 times larger.

Evidence of self-biased magnetoelectric coupling in eco-friendly (Na0.41K0.09Bi0.5TiO3-Ba0.85Ca0.15Zr0.1Ti0.9O3)-(CoFe2O4) particulate composites

The magnetoelectric (ME) properties of eco-friendly 1-x(0.94Na0.41K0.09Bi0.5TiO3-0.06Ba0.85Ca0.15Zr0.1Ti0.9O3)-x (CoFe2O4) (NKBCZT-CFO) with x = 0, 0.1, 0.2, 0.3 and 0.4 particulate composites were investigated. The X-ray diffraction studies provided evidence for the simultaneous existence of constituent phases (ferroelectric and ferromagnetic) in the composite. The structural and surface morphology analysis of the composite affirmed the homogeneous and densely packed distribution of CFO grains within the NKBCZT matrix. The composite's multiferroic behavior at room temperature was confirmed through the characterization of P vs E and M vs H hysteresis loops. The observed values of remnant polarization (Pr) and coercive field (Ec) are 26.7 μC/cm2 and 35.5 kV/cm, respectively, for 10 mol% of CFO. The increase in CFO content resulted in a decrease in the ferroelectric properties, possibly due to the conductive behaviour exhibited by CFO, and correlated with leakage current measurement. For the composite containing 40 mol% of CFO, the estimated values of remanent (Mr), saturation (Ms) magnetization, coercive field (Hc), and magnetic moment (µB) are 2.35 emu/g, 21.85 emu/g, 104.2 Oe, and 0.86 µB, respectively. The non-Debye type dielectric relaxation processes have been observed in the composites, and the electron hopping mechanism resulted in a higher dielectric constant (εʹ). Enhancement in relaxor nature had been observed through Vogel-Fulcher analysis with CFO content. The evidence of ME coupling was revealed through the direct ME voltage coefficient (αME) and magnetocapacitance (MC) measurement. The observed maximum value of MC measured at 1 kHz for the 20 mol% CFO is ∼5.6 %. Self-biased ME coupling (non-zero αME at HDC = 0 Oe) was observed in 20 and 30 mol% of CFO composite. The highest measured value of αME for 20 and 30 mol% CFO is 3.63 mV/cm.Oe and 4.09 mV/cm.Oe at HDC = 0 Oe respectively. The strong ME interaction and significant value of self-biased ME αME suggest that these composites can be explored for magnetic sensor and ME memory device applications.

Breakdown performance of guard ring designs for pixel detectors in 150 nm CMOS technology

Silicon pixel sensors manufactured using commercial CMOS processes are promising instruments for high-energy particle physics experiments due to their high yield and proven radiation hardness. As one of the essential factors for the operation of detectors, the breakdown performance of pixel sensors constitutes the upper limit of the operating voltage. Six types of passive CMOS test structures were fabricated on high-resistivity wafers. Each of them features a combination of different inter-pixel designs and sets of floating guard rings, which differ from each other in the geometrical layout, implantation type, and overhang structure. A comparative study based on leakage current measurements in the sensor substrate of unirradiated samples was carried out to identify correlations between guard ring designs and breakdown voltages. TCAD simulations using the design parameters of the test structures were performed to discuss the observations and, together with the measurements, ultimately provide design features targeting higher breakdown voltages.

Multi-Stimuli Operando Transmission Electron Microscopy for Two-Terminal Oxide-Based Devices.

The integration of microelectromechanical systems (MEMS)-based chips for in situ transmission electron microscopy (TEM) has emerged as a highly promising technique in the study of nanoelectronic devices within their operational parameters. This innovative approach facilitates the comprehensive exploration of electrical properties resulting from the simultaneous exposure of these devices to a diverse range of stimuli. However, the control of each individual stimulus within the confined environment of an electron microscope is challenging. In this study, we present novel findings on the effect of a multi-stimuli application on the electrical performance of TEM lamella devices. To approximate the leakage current measurements of macroscale electronic devices in TEM lamellae, we have developed a postfocused ion beam (FIB) healing technique. This technique combines dedicated MEMS-based chips and in situ TEM gas cells, enabling biasing experiments under environmental conditions. Notably, our observations reveal a reoxidation process that leads to a decrease in leakage current for SrTiO3-based memristors and BaSrTiO3-based tunable capacitor devices following ion and electron bombardment in oxygen-rich environments. These findings represent a significant step toward the realization of multi-stimuli TEM experiments on metal-insulator-metal devices, offering the potential for further exploration and a deeper understanding of their intricate behavior.

Environmental Effects on Parameters of Leakage Current Equivalent Circuits of Outdoor Insulators

The performance of outdoor insulators in transmission lines may deteriorate due to aging and can even be enhanced by the presence of pollutants. Leakage current (LC) measurement is one of the most effective methods to diagnose the insulator condition, utilizing LC parameters such as magnitude and total harmonic distortion (THD). However, research on the interpretation of these parameters is still limited. This paper discusses the diagnostic method by simulation, employing the LC equivalent circuits of different types of insulators and examining the influence of environmental factors, such as humidity and pollutant levels. LC waveforms are first obtained through experiments on various insulator types, including traditional ceramic and glass insulators, advanced composite insulators, or the hybrid type of RTV silicone rubber-coated and conducting glazed insulators. Subsequently, simulations on the LC circuits of Suwarno’s and Kizilcay’s models are performed to obtain similar LC waveforms and properties. The values of the equivalent circuit parameters are then used to diagnose each insulator’s characteristics and environmental effects. The results indicate that composite insulators of epoxy resin or SiR have a larger intrinsic resistance of ~40 GΩ and nonlinear resistance (a few MΩ to tens of GΩ), representing high surface resistance of the insulators against water and pollutants. A comparison of these parameters is expected to indicate the severity levels of insulator condition. Doi: 10.28991/ESJ-2024-08-01-022 Full Text: PDF

Построение системы измерения параметров подвесных ОПН на базе микроконтроллера с беспроводной передачей данных

The article is aimed at analyzing the possibility of constructing a system for remote measurement of leakage currents, measuring the pulses of current flowing through the surge arrester with the registration of the time of the event with subsequent accumulation and transmission to service personnel. A system for transmitting measured parameters via the ZigBee protocol is constructed. A calculation of the required power supply for continuous operation of the device for more than 20 years is made.

Thermal Stability of Schottky Contacts and Rearrangement of Defects in β‐Ga2O3 Crystals

AbstractThe thermal stability of different Schottky contacts (Au, Pt, and Ni) on (100) β‐Ga2O3 single crystals grown by the Czochralski method is investigated. Besides the examination of the Schottky barrier parameters, contact‐dependent defect levels are investigated by deep‐level transient spectroscopy (DLTS) in a 100–650 K (ramp‐up) and 650–100 K (ramp‐down) temperature cycle. Several defect levels are detected below the conduction band minimum at 0.41, 0.60, 0.77, 0.96, and 1.17 eV. In the temperature ramp‐down DLTS, the 1.17 eV level disappears, and the 0.60 eV level appears for all Schottky contacts. DFT calculations suggest that rearrangement and dissociation of a single hydrogen from a doubly‐hydrogenated Ga─O divacancy complex occurs during the temperature sweep under bias. The trap level at 0.96 eV only appears after the thermal load for the Ni contact, in contrast to Au and Pt, where it is present without a thermal budget. Temperature‐dependent leakage current (at −4 V) measurements indicate oxidation of Ni, and further thermodynamic analysis suggests alloying of Au‐Ga atoms at the Au/β‐Ga2O3 interface. These studies provide insight into the behavior induced by these common Schottky contacts and the alteration associated with temperature cycling.

Critical Contribution of Imbalanced Charge Loss to Performance Deterioration of Si-Based Lithium-Ion Cells during Calendar Aging.

Increasing the energy density of lithium-ion batteries, and thereby reducing costs, is a major target for industry and academic research. One of the best opportunities is to replace the traditional graphite anode with a high-capacity anode material, such as silicon. However, Si-based lithium-ion batteries have been widely reported to suffer from a limited calendar life for automobile applications. Heretofore, there lacks a fundamental understanding of calendar aging for rationally developing mitigation strategies. Both open-circuit voltage and voltage-hold aging protocols were utilized to characterize the aging behavior of Si-based cells. Particularly, a high-precision leakage current measurement was applied to quantitatively measure the rate of parasitic reactions at the electrode/electrolyte interface. The rate of parasitic reactions at the Si anode was found 5 times and 15 times faster than those of LiNi0.8Mn0.1Co0.1O2 and LiFePO4 cathodes, respectively. The imbalanced charge loss from parasitic reactions plays a critical role in exacerbating performance deterioration. In addition, a linear relationship between capacity loss and charge consumption from parasitic reactions provides fundamental support to assess calendar life through voltage-hold tests. These new findings imply that longer calendar life can be achieved by suppressing parasitic reactions at the Si anode to balance charge consumption during calendar aging.

Frequency characteristics analysis of pipe-to-soil potential under metro stray current interference using continuous wavelet transform method

This study aims to investigate the impact of stray current interference from metro systems on the pipe-to-soil potentials of metallic pipelines, which is closely associated with stray current corrosion. The pipe-to-soil potentials were assessed using coupon testing, while in-situ measurement was conducted to measure the metro leakage currents. The collected field data from the pipe-to-soil potentials and metro leakage current measurements were subjected to a statistical analysis using Continuous Wavelet Transform (CWT) and linear correlation methods. The analysis revealed consistent dominant frequencies of interference at the same test point for both on-potentials and off-potentials conditions, as well as within different time periods. However, variations in dominant frequencies of interference were observed among test points along different sections of the pipeline. Notably, three primary test points exhibited frequencies of 8.3, 8.9, and 7.8 mHz, corresponding to the main interstation travel intervals of neighboring metro lines. Furthermore, the dominant period ranges of interference of metro stray current interference were found to align with the interstation travel interval ranges of the metro lines. When the OVPD acts, the leakage current of the metro station grounding system near the test point has a significant contribution to the amplitude of pipe-to-soil potential fluctuation. These findings highlight the significant role of interstation travel intervals in the periodicity of metro stray current interference. The identified dominant interference frequency ranges can be utilized to determine interference sources and evaluate the extent of metro stray current corrosion.

Effect of Oxygen Annealing Atmosphere on Structural, Electrical and Energy Storage Properties of Bi0.5Na0.5TiO3 Polycrystalline Thin Film

Bismuth sodium titanate (BNT) thin films were deposited on Pt/SiN substrates by Sol-Gel spin coating technique and annealed under O2 atmosphere. The microstructural, structural, and electrical properties of the obtained film were investigated. Electron microscopy scans and atomic force microscopy micrographs were used to analyze the microstructure of the films. Furthermore, energy-dispersive X-ray spectroscopy (EDX) analysis revealed a Na-deficient composition for the obtained film. X-ray diffraction and Raman spectroscopy allowed the identification of a pure perovskite BNT phase. Dielectric, ferroelectric, and leakage current measurements revealed good frequency stability of the dielectric constant and dielectric losses for BNT thin film. The results are discussed in terms of Na deficiency effects on the defect structure of BNT. Further, the film showed attractive electrostatic energy storage properties with energy density that exceeds 1.04 J/cm3 under E = 630 kV/cm.

Design of Light Emitting Diode-Based Fiber Optic Current Sensor and Its Application in Pollution Flash Prevention in Digitalized Substations

Prevention of pollution flash in electrical equipment in digitalized substations and transmission lines has always been a crucial part of power operation. In order to prevent pollution flash, it is essential to detect the contamination of electrical equipment. The measurement of leakage current is a fundamental aspect of preventive pollution flash work in electrical equipment. Applying fiber optic current sensors to online monitoring systems in the power system offers advantages such as resistance to harsh environments, immunity to electromagnetic interference, and resistance to chemical corrosion. This study designs a unidirectional half-wave fiber optic current sensor based on Light Emitting Diodes (LED) for selectively observing the positive and negative half-cycles of leakage current. Due to the light emission and unidirectional conduction characteristics of LED, with a well-designed circuit, LED performs photoelectric conversion on the current, allowing the sensor to selectively measure the positive and negative half-cycles of leakage current. Subsequently, a combination circuit of silicon detectors and amplifiers is used to complete the photoelectric conversion, facilitating voltage signal measurement. In experiments, the response of the unidirectional half-wave LED fiber optic current sensor reached 37.8 mV/mA, with a detection bandwidth range between [1.2 kHz, 9.8 kHz]. In leakage current tests, using the leakage current of insulators as a reference, experiments were conducted using the voltage boosting method. As the applied voltage increased, the leakage current displayed on the sampling resistor increased, and the measurement waveform indicated that the sensor could correctly select the unidirectional half-wave. In leakage current and salt density tests, the designed fiber optic sensor accurately reflected the exponential relationship between insulator leakage current and contamination, demonstrating the practical value of the designed fiber optic current sensor.

Characteristics stability assessment of silica/alumina trihydrate based silicone elastomer composites subjected to long-term weathering under bipolar direct current for industrial electrical insulation

Room temperature vulcanized silicone rubber (RTV-SiR) coatings co-filled with silica (SiO2) and alumina trihydrate (ATH) fillers were subjected to long-term accelerated weathering under bipolar direct current (DC). Experimentations were conducted on fabricated samples of RTV-SiR with 5% nano-silica and RTV-SiR with 20% ATH in a specially designed weathering chamber. An extended aging (10,000 h) was conducted on samples energized equally under both polarity voltages to evaluate the effect of positive and negative voltages on the performance of RTV coating under bipolar high voltage DC. The electrical stability of specimens was assessed using online leakage current measurement, hydrophobicity, volume, and surface resistivity analysis. For mechanical characteristics of test samples hardness shore-A, tensile strength, weight loss, and elongation-at-break were measured and analyzed. Variations in chemical, morphological, and thermal degradation of the samples with aging were assessed using characterization tools like Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Thermal Gravimetric Analyzer (TGA), respectively. Findings explicated that samples with nano SiO2, offer better hydrophobic recovery and hence better leakage current suppression while ATH-filled composites exhibited enhanced thermal stability and better resistance to mechanical alterations. Furthermore, the comparative analysis of voltage polarity elucidates that the impact of positive DC was more profound in aging.

Study of changes in leakage currents under a contaminated and moistened surface of insulators of the PS-6B, PS-120A, PSD-70E types of overhead power lines

In the process of operation, insulators are exposed to repeated pollution and atmospheric influences. This is due to the removal of pollutants from industrial metallurgical enterprises, chemical plants and their deposition on the surface of insulators near power transmission lines. In normal operation, when the insulators are dirty, but their surface is not wetted, the active component of the total leakage current can be neglected. It is another matter when the surface of the contaminated insulator is intensively moistened by atmospheric influences, for example: rain, fog, dew, respectively, and the value of the active component of the leakage current also increases in proportion to the conductivity of the formed electrolyte, the layer of contamination on the surface of the insulating surface of the insulator. The article discusses the method of measuring leakage currents on the contaminated surface of various types of glass plate insulators in laboratory conditions, with artificial and natural contamination. In the dry state, a leakage current flows through contaminated insulators, which mainly depends on the electrical capacity of the insulator. A method of calculating the active component of the leakage current is proposed, since the active component of the leakage current is the main parameter for determining energy losses due to its dissipation into the environment. The results of the change in the value of the leakage currents in the time characteristics after wetting the surface layer of pollution to the leakage current in the dry state of the insulator surface are given. The observation of drying processes of a contaminated and moistened surface due to the influence of leakage currents is given. The formation of dried zones on the surface of contaminated insulation of plate insulators of overhead power lines under the action of leakage currents was investigated. An analysis of the obtained results was carried out, conclusions were drawn.

External Leakage Current Separation to Determine Arrester Condition Due to Contamination

Leakage current measurements can be used to determine the aging condition of the ZnO arrester. The leakage current that occurs in the arrester is divided into two, namely external and internal leakage currents. The external leakage current is affected by contamination and the internal leakage current is affected by the aging of the varistor in the arrester. The external and internal leakage currents are measured separately to determine their contribution to the arrester condition. In this study, the effect of salt contamination on the arrester was studied further. The level of contamination used consisted of low, medium and heavy. The obtained leakage current is analyzed using wavelet energy. The results of this study indicate that the wavelet energy of each leakage current is different and can be used as an indicator in further analysis. The conclusion obtained is that the external leakage current is affected by contamination and has a different energy with the internal leakage current due to aging of the varistor arrester components.

Study tracking and erosion properties of modified nitrile butadiene rubber with nanoparticles by inclined plane test

Occurrence of tracking and erosion on surface of polymer insulator leads to breakdown of these materials and has negative impact on their quality. Contaminants forms surface layer on insulators and chemically interact with it. This effect reduces smoothness of surface insulator and forms conducting paths. It allow passage of higher values of leakage current and cause ionization of field around insulator and rise temperature of surfaces, this leads to formation phenomenon of tracking and erosion.it cause deterioration, ageing and collapse of insulator, which affect safety of electric system. How to significantly enhance the tracking and erosion properties of nitrile butadiene rubber (NBR) are a major topic in electric insulators. With a view to enhancing the tracking and erosion properties of NBR used in power systems, nanoparticles are usually added to pure materials to enhance their electrical and physical properties. This work deals with experimental studies on tracking and erosion properties on NBR loaded with [0, 0.5, 1, 1.5, and 3 part per hundred part of rubber (Phr.)] titanium dioxide (TiO2) nanoparticles. Composite materials have been experimentally tested by inclined plane test (IPT) according to the ASTM D2303 standard. When it is necessary to explore a new insulating material, the inclined plane test is used. This is because IPT is used to evaluate the properties of laboratory modified polymers under different voltages. The times to track during the test were recorded. Data processing, analog to digital systems, and data acquisition have been used to measure leakage current passing through samples. When comparing result of leakage current measurements, it was noted that its value was lower for modified samples compared to virgin samples. This positive effect indicates to enhancement of NBR as a result of formation of stable chemical bonds.