High Voltage Research Articles

Characterisation of surface morphology of high voltage DC relay contacts under arc erosion

Abstract High voltage DC relays are a crucial component in new energy vehicles. Due to the high failure rate caused by contact sticking (fusion welding), existing technologies can only analyze contact morphology after failure. There is an urgent need to determine the quantitative characterization value of contact surface morphology and the correlation between morphology, failure mechanisms, and working conditions. In this study, an Olympus DSX1000 microscope is used to extract surface topography data, and a quantitative topography characterization method based on a machine vision system is proposed to quantitatively analyze contact surface changes after arc erosion. Grey correlation analysis was applied to explore the relationship between electrical parameters such as voltage, current, and capacitance, and the contact morphology features. The results show that current and capacitance have the greatest influence on contact surface features after arc erosion, while voltage has a relatively smaller influence. This conclusion is consistent with the experimentally observed arc erosion features. Finally, an arc ion sputtering deposition model was developed to analyze the material transfer mode and its influence on the contact failure mechanism. The results provide a scientific basis for the analysis and design improvement of high voltage DC relays.

Fabrication of Electrospun Porous TiO2 Dielectric Film in a Ti–TiO2–Si Heterostructure for Metal–Insulator–Semiconductor Capacitors

The development of metal–insulator–semiconductor (MIS) capacitors requires device miniaturization and excellent electrical properties. Traditional SiO2 gate dielectrics have reached their physical limits. In this context, high-k materials such as TiO2 are emerging as promising alternatives to SiO2. However, the deposition of dielectric layers in MIS capacitors typically requires high-vacuum equipment and challenging processing conditions. Therefore, in this study, we present a new method to effectively fabricate a poly(vinylidene fluoride) (PVDF)-based TiO2 dielectric layer via electrospinning. Nano-microscale layers were formed via electrospinning by applying a high voltage to a polymer solution, and electrical properties were analyzed as a function of the TiO2 crystalline phase and residual amount of PVDF at different annealing temperatures. Improved electrical properties were observed with increasing TiO2 anatase content, and the residual amount of PVDF decreased with increasing annealing temperature. The sample annealed at 600 °C showed a lower leakage current than those annealed at 300 and 450 °C, with a leakage current density of 7.5 × 10−13 A/cm2 when Vg = 0 V. Thus, electrospinning-based coating is a cost-effective method to fabricate dielectric thin films. Further studies will show that it is flexible and dielectric tunable, thus contributing to improve the performance of next-generation electronic devices.

Effect of Rare Earth Ion Doping on the Performance of Lithium-Rich Cathode Materials for Lithium-Ion Batteries

Lithium-rich layered oxide cathode materials have the advantages of a high voltage and a high specific capacity. Their commercial applications have however been impeded by some disadvantages such as low initial coulombic efficiency and low cycle life. To overcome these issues, rare earth ion-doped lithium-rich layered oxide cathode materials are investigated in this work. The irreversible release of O2- in Li2MnO3 is suppressed by rare earth ions doping, which enhanced the initial coulombic efficiency of the materials. Meanwhile, the rare-earth ion radius used for doping is larger than the Mn4+ radius, which enlarges the (003)-crystalline plane spacing, resulting in a significant enhancement of the rate performance of the material.

Detection of nanopores with the scanning ion conductance microscopy: A simulation study

During the dielectric breakdown process of thin solid-state nanopores, the application of high voltages may cause the formation of multi-nanopores on one chip, which number and sizes are important for their applications. Here, simulations were conducted to mimic the investigation of in situ nanopore detection with scanning ion conductance microscopy (SICM). Results show that SICM can provide accurate nanopore location and relative pore size. Detection resolution is influenced by the dimensions of the applied probe and separation between the probe and membranes, which can be enhanced under large voltages or a concentration gradient.

State Estimation of Radial Distribution Systems Based on Multiple Legendre Neural Networks

The conventional weighted least square (WLS) method is the most effective technique used in the state estimation of high voltage transmission system. Unfortunately, the application of WLS in radial distribution network encounter difficulties due to the inherent characteristics of these systems, such as the low measurement redundancy and high r/x ratio of the distribution systems. Given the structure of bulky systems that require a bulky number of measurements, the use of artificial neural networks is considered an effective alternative to estimate these values using a lesser number of measurements than conventional techniques. Due to state estimation based on ANN technique, the time-consuming gain matrix manipulation and pseudo measurements required in the conventional WLS method are no longer necessary. The efficiency of deep learning neural networks such as multi-layer perceptron (MLP) and Legendre neural network (LeNN) depends on the position of the measurements and the number of neural networks applied. Determining the applicable number of neural networks to ensure high estimation accuracy plays an important role in the estimation process. This aspect is addressed in this study, where multiple neural networks are used to improve performance compared to a single neural network. The results obtained indicate that determining the applicable number of neural networks depends on several factors such as the position of the measurements and the diversity of the data. The application of LeNN on state estimation of a 69-bus radial distribution network is used as an illustrative example to explain the distinctive feature of the proposed technique.

A differential low frequency eddy current test method for detecting moisture content of high voltage cable water-blocking tape

ABSTRACT The excessive moisture content in the water-blocking tape has been one of the main causes of high voltage cable erosion failures in recent years. However, the 2–4 mm thick aluminium sheath wrapped around the water-blocking tape makes it challenging to detect the moisture content. This study introduces a method for detecting the moisture content of high voltage cable water-blocking tapes based on low-frequency eddy currents. Initially, longitudinal and transverse impedance measurement experiments of the water-blocking tape were conducted to establish the relationship between impedance and moisture content. Since the impedance of the water-blocking tape is significantly higher compared to the aluminium sheath, the eddy current signal was obtained using a differential detection method. An excitation frequency of 10 Hz was chosen to achieve a deeper skin depth. Additionally, an eddy current finite element analysis model was developed, showing that moisture content has an almost linear relationship with the amplitude and phase of the eddy current signal. Finally, an experiment was conducted on an equivalent high voltage cable structure, and the experimental results aligned well with the simulation results.

A Novel Isolation Approach for GaN-Based Power Integrated Devices

This paper introduces a novel technology for the monolithic integration of GaN-based vertical and lateral devices. This approach is groundbreaking as it facilitates the drive of high-power GaN vertical switching devices through lateral GaN HEMTs with minimal losses and enhanced stability. A significant challenge in this technology is ensuring electrical isolation between the two types of devices. We propose a new isolation method designed to prevent any degradation of the lateral transistor’s performance. Specifically, high voltage applied to the drain of the vertical GaN power FinFET can adversely affect the lateral GaN HEMT’s performance, leading to a shift in the threshold voltage and potentially compromising device stability and driver performance. To address this issue, we introduce a highly doped n+ GaN layer positioned between the epitaxial layers of the two devices. This approach is validated using the TCAD-Sentaurus simulator, demonstrating that the n+ GaN layer effectively blocks the vertical electric field and prevents any depletion or enhancement of the 2D electron gas (2DEG) in the lateral GaN HEMT. To our knowledge, this represents the first publication of such an innovative isolation strategy between vertical and lateral GaN devices.

Revisiting ether electrolytes for high-voltage sodium-ion batteries

While ether electrolytes show great potential for anode materials of sodium-ion batteries (SIBs), they are perceived to be intolerant to high voltage (4.0 V and above) and are rarely employed in cathode materials. Herein, four typical ether electrolytes are examined and the oxidative stability is demonstrated to be closely related to their solvation structures. The anion-involved solvation structure lowers the tolerance of weakly solvated electrolyte to high voltage, and the resulting inorganics-rich cathode electrolyte interphase is equipped with high resistance and friability, leading to undesired rate and cycle performance. In contras, strongly solvated electrolytes can cycle stably at a high voltage of 4.3 V with high rate performance. As a proof-of-concept, the Graphite//Na3(VOPO4)2F full cell based on G2 electrolyte (1 M NaPF6 in glyme) can deliver a high energy density of 126.3 Wh kg−1 at 61.2 W kg−1 and a desirable power density of 5424.3 W kg−1 at 65.1 Wh kg−1, providing a demonstration for the potential application of ether electrolytes in high-voltage SIBs.

Degradation Mechanism and Online Electrical Monitoring Techniques of Stator Winding Insulation in Inverter-Fed Machines: A Review

Inverter-fed machines are widely used in electric vehicle drive systems and have shown a trend toward high voltage and frequency in recent years. They are subjected to multiple types of stress during operation, causing potential short-circuit fault damage to the stator winding insulation. Online condition monitoring of the insulation before or in the early stage of the short circuit fault can effectively reduce maintenance costs and ensure its health. This paper reviews and summarizes the deterioration mechanism and the recent online electrical monitoring techniques. First, four types of failure stress and each type’s failure factors and mechanisms are analyzed. The coupling effect and overall process of multi-physical fields on stator insulation failure are considered. Secondly, the latest online electrical monitoring technologies are summarized. Each technique’s principles, methods, advantages, and disadvantages are analyzed. Finally, existing problems and possible directions for improvement in current research are discussed, focusing on their feasibility and accuracy in practical applications.

Nickel‐Manganese‐Based Layered Oxide for Sodium Ion Battery Cathode Materials

Sodium‐ion batteries (SIBs) have demonstrated significant potential as alternatives to conventional lithium‐ion batteries (LIBs) for modern grid and mobile energy storage applications, due to the abundant natural resources and low cost of sodium. Layered transition metal oxides (LTMOs) have attracted focused research attentions due to their high specific capacities, energy densities as well as the compatible preparation processes with those of LIBs cathode materials. Among these, Ni/Mn‐based LTMOs (NMLOs) are particularly noteworthy for their cost‐effectiveness and superior electrochemical performance, such as excellent capacity retention, voltage stability, high operating voltage and rate capability. In this review, we briefly introduce the synthesis methods of NMLOs, discuss the challenges, and summarize the solutions. The insights presented may contribute to the development of NMLOs based SIBs.

Measurement of pulse current during high voltage tests using Rogowski coil with non-inverting integrator

The work is devoted to the development and modelling of the system of pulse current measurement during high-voltage tests and experiments. The proposed measurement system is based on the application of Rogowski coil with non-inverting integrator. The results of numerical modelling of the developed current measurement system are compared with the results of application of a low-inductance shunt resistor, Rogowski coil with passive RC-integrator and Rogowski coil with inverting active integrator in similar measurement systems. Various standard pulse currents including steep edge pulse (1/20 µs), large amplitude current pulse (4/10 µs), lightning pulse current (8/20 µs), switching pulse current (30/80 µs), and 1-3 ms pulse currents are modelled for the comparative test. From the simulation results, it follows that the developed Rogowski coil with the proposed non-inverting integrator has sufficiently high accuracy in a wide frequency band overlapping the frequency band of standard pulse currents in high-voltage tests.

An ultra-high gain boost converter with low switching stress for integrated multi-energy storage systems

In this paper, a high-gain low-switching-stress coupled-inductor with high voltage step-up voltage multiplier cells quadratic boost converter (VMC-QBC) is proposed. The turn ratio of the coupled inductors and the switch duty cycle increase the dynamic gain, and the two degrees of freedom adjustment and modularity of the voltage multiplier cells (VMC) make the structure more flexible. The use of the same drive signal for both switches makes control easier. While achieving multi-stage boosting and multiplication boosting from low to medium duty cycle, the passive clamping circuit absorbs the energy leaked by the coupled inductor, thus reducing the stress on the switching tube and alleviating the diode reverse recovery problem. A non-ideal model with parasitic parameters is developed to analyse the real voltage gain and the converter losses to give design guidelines. A 300 W prototype is designed and tested. The state space model of the converter is established and the working principle is analysed. Compared to other high-gain quadratic boost converters, the proposed converter has continuous input current, common ground characteristics, and high voltage gain at low to medium duty cycles to accommodate integrated multi-energy storage systems.

Economic Load Dispatch on a 132 kV Line with Service Potential Transformer Substations: A Case Study of Juja-Rabai Line.

Power outages have created significant challenges for power system networks, particularly in developing countries where the electricity demand continues to rise without a corresponding increase in power generation or the expansion of transmission and distribution networks. In Kenya, while there is a well-established transmission line network, the distribution infrastructure remains inadequate for supplying electricity to end consumers. This paper examines the economic load dispatch (ELD) of power system networks utilizing Service Potential Transformer (SPT) substations to provide electricity to villages located near high voltage (HV) lines. The ELD analysis was conducted to identify the optimal economic power output from the Kipevu, Rabai, and Thika thermal power plants, addressing the demand for both conventional and non-conventional substations. A gradient method was employed to calculate the ELD for these three generating units, and the results were validated using the PowerWorld simulator. Findings indicated that the three generators supplied 20 MW, 37.5 MW, and 12.5 MW, respectively. The results obtained from the gradient method are consistent with those obtained from PowerWorld software. Additionally, this study projected an annual fuel cost savings of USD 17,695.20 when ELD was implemented, compared to a scenario of equal load distribution among generating units. Over a ten-year period, these savings would be sufficient to establish a conventional distribution substation to meet the power demands of villages located further away from high voltage lines.

Controllable Synthesis of Hollow Dodecahedral Si@C Core-Shell Structures for Ultrastable Lithium-Ion Batteries.

Silicon (Si) has attracted considerable attention as a promising alternative to graphite in lithium-ion batteries (LIBs) because of its high theoretical capacity and voltage. However, the durability and cycling stability of Si-based composites have emerged as major obstacles to their widespread adoption as LIBs anode materials. To tackle these challenges, a hollow core-shell dodecahedra structure of a Si-based composite (HD-Si@C) is developed through a novel double-layer in situ growth approach. This innovative design ensures that the nano-sized Si particles are evenly distributed within a hollow carbon shell, effectively addressing issues like Si fragmentation, volume expansion, and detachment from the carbon layer during cycles. The HD-Si@C composite demonstrates remarkable structural integrity as a LIBs anode, resulting in exceptional electrochemical performance and promising practical applications, as evidenced by tests in pouch-type full cells. Notably, the composite shows outstanding cycling stability, retaining 85% of its initial capacity (713 mAh g-1) even after 3000 cycles at a high current rate of 5000mA g-1. Additionally, the material achieves a gravimetric energy density of 369Wh kg-1, showcasing its potential for efficient energy storage solutions. This research signifies a significant step toward realizing the practical utilization of Si-based materials in the next generation of LIBs.

Optimal Placement of HVDC-VSC in AC System Using Self-Adaptive Bonobo Optimizer to Solve Optimal Power Flows: A Case Study of the Algerian Electrical Network

Modern electrical power networks make extensive use of high voltage direct current transmission systems based on voltage source converters due to their advantages in terms of both cost and flexibility. Moreover, incorporating a direct current link adds more complexity to the optimal power flow computation. This paper presents a new meta-heuristic technique, named self-adaptive bonobo optimizer, which is an improved version of bonobo optimizer. It aims to solve the optimal power flow for alternating current power systems and hybrid systems AC/DC, to find the optimal location of the high voltage direct current line in the network, with a view to minimize the total generation costs and the total active power transmission losses. The self-adaptive bonobo optimizer was tested on the IEEE 30-bus system, and the large-scale Algerian 114-bus electric network. The obtained results were assessed and contrasted with those previously published in the literature in order to demonstrate the effectiveness and potential of the suggested strategy.

Alamethicin channel inactivation caused by voltage-driven flux of alamethicin

We show that voltage alone can inactivate alamethicin channels, which has been previously observed for monazomycin and suzukacillin channels. The voltage required to trigger inactivation is above the potential to form channels, and, like with channel activation, this threshold reduces with increasing peptide concentration and membrane fluidity. Since similar monazomycin channels inactivate via channel break up and translocation, we hypothesized that inactivation of alamethicin channels occurs via the same mechanism. Our data prove this hypothesis to be true through two experiments. First, we show that inactivation of channels at positive voltages when peptides are supplied to only the cis side correlates to new channel activity on the trans side at negative potentials. This result indicates translocation of alamethicin peptides occurs only during voltage-induced inactivation. Second, we measured the ratio of steady-state (with inactivation) to ideal (without inactivation) conductance versus voltage for membranes with equal amounts of alamethicin on both sides and used these values to quantify alamethicin flux. Plotting flux versus steady-state conductance across multiple alamethicin concentrations shows a single linear dependence, signifying that translocated peptides originate from active channels that break up under prolonged voltage. Given the frequent use of alamethicin as model ion channels, these results add important understanding of their kinetic responses when subjected to prolonged, high voltages.

Exploiting Spatial Ionic Dynamics in Solid-State Organic Electrochemical Transistors for Multi-Tactile Sensing and Processing.

The human nervous system inspires the next generation of sensory and communication systems for robotics, human-machine interfaces (HMIs), biomedical applications, and artificial intelligence. Neuromorphic approaches address processing challenges; however, the vast number of sensors and their large-scale distribution complicate analog data manipulation. Conventional digital multiplexers are limited by complex circuit architecture and high supply voltage. Large sensory arrays further complicate wiring. An 'in-electrolyte computing' platform is presented by integrating organic electrochemical transistors (OECTs) with a solid-state polymer electrolyte. These devices use synapse-like signal transport and spatially dependent bulk ionic doping, achieving over 400 times modulation in channel conductance, allowing discrimination of locally random-access events without peripheral circuitry or address assignment. It demonstrates information processing from 12 tactile sensors with a single OECT output, showing clear advantages in circuit simplicity over existing all-electronic, all-digital implementations. This self-multiplexer platform offers exciting prospects for circuit-free integration with sensory arrays for high-quality, large-volume analog signal processing.

Comprehensive analysis of soil electrical conductivity: an experimental and machine learning approach

Experimental test is conducted to find a relation between soil electrical conductivity with some soil properties. Five input parameters namely water content (w), dry density of soil (γd), degree of saturation (Sr), porosity (η) and voltage (V) are considered to compute electrical conductivity of soil (SEC). The effect of w, γd, Sr and η on SEC are analyzed. These datasets are used in soft computing technique to predict SEC. Five hybrid models namely ANN-GA, ANN-PSO, ANN-FA, ANN-GWO and ANN-MFO are used to predict SEC. To check the performance of these hybrid model, numerous statistical performance parameters (R2, a-10 index, VAF, LMI, RMSE, MAE, MAD and U95) are used. On the basis of these performance parameters, ANN-GA performs better (Due to higher value of R2, VAF, a-10 index and LMI and lower value of RMSE, MAE, MAD and U95) as compare to the other proposed model. The model's performance is also examined using rank analysis, regression curve, Williams plot, error matrix, objective function (OBJ) criterion, and Akaike information criterion (AIC). By applying all the above criteria, it has been observed that ANN-GA model outperforms than the other model to predict SEC. This was recognized to its maximum R2 = 0.9998 and the lowest RMSE = 0.0041 during the training phase, as well as R2 = 0.9975 and RMSE = 0.0112 during the testing phase. The model's reliability index (β) is calculated using the first-order second moment (FOSM) approach, and the result is compared to its actual condition. Additionally, a sensitivity analysis is carried out to ascertain the impact of each input parameter on the output (SEC).Based on the results, the hybrid model of ANN i.e., ANN-GA is potential to assist engineers to predict SEC in the design phase of high voltage buried power cables, ground modification techniques or in the field of agriculture.

Pilot-scale capacitive deionization for water softening: Performance, energy consumption, and ion selectivity

Capacitive deionization (CDI) has emerged as an efficient process for hardness control than traditional water-softening technologies. However, few systematic studies have been conducted on water softening using pilot-scale CDI systems. For industrial applications, it is essential to investigate deionization performance, energy consumption, and selectivity for divalent cations through pilot-scale studies. In this study, we examined the deionization performance and energy consumption of a pilot-scale CDI process for effective water softening. The key operational variables analyzed were the applied voltage (200–300 V (i.e., 1.0–1.5 V per pair)), feed concentration (550–1250 mg/L), recovery ratio (50–80 %), flow rate (3–5 L/min), and adsorption/desorption time (80–180 s). Within this range, a high voltage, low feed concentration, low recovery ratio, high flow rate, and long adsorption/desorption times are advantageous for the total dissolved solids (TDS) removal ratio. In terms of energy efficiency, expressed as TDS removal per unit energy consumption, a low voltage, low feed concentration, low recovery ratio, fast flow rate, and long adsorption/desorption time are beneficial. Additionally, we investigated the selective removal of Ca2+ over Na+ under various operating conditions, as well as its impact on enhancing energy efficiency. The pilot CDI system achieved a Ca/Na selectivity coefficient of approximately 2.4 and it was analyzed to achieve up to 45 % energy-saving efficiency compared to nonselective systems (i.e., selectivity coefficient = 1). The results of this study are expected to provide valuable data for the application of CDI to water softening and hardness control processes.

In-situ observation of defects evolution of graphene nanoflakes in Pt/C catalyst for boosting ORR performance

The structural stability of supported metal nanoparticles determines the activity and longevity of heterogeneous catalysts. Unfortunately, the chemical/thermal working environment inevitably accelerates metal sintering to larger crystallites that leads to the degradation of catalytic performance. Here, we demonstrate that the distribution of defects in carbon support as an inherent parameter plays a crucial role in catalyst sintering. Based on in-situ transmission electron microscopy studies, the strong metal-support interaction between platinum (Pt) nanoparticles and defect-rich graphene nanoflakes largely suppresses metal sintering up to 700 °C. Particularly, the optimal carbon support can be achieved in the annealing process, in which the mass transfer and charge transport can be enhanced by accurately manipulating the distribution of defects in carbon matrix and graphitization degree. It is worth noting that the screened Pt/GNs-300 exhibits impressive oxygen reduction reaction performance with high half-wave potential (0.91 V), mass activity (108.1 A g–1Pt) and excellent stability. By its ascendancy in ORR, the Pt/GNs-300 exhibits a high open-circuit voltage of 1.41 V and a maximum power density of 198.6 mW cm−2 in Zn-air battery, implying its brilliant practicability. This work paves a pathway for achieving sinter-resistant metal-loaded catalysts in energy electrocatalysis.