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Purpose The purpose of this paper is numerical calculation of total electric field in oil-paper insulation. Now, there is no effective method to consider the influence of space charges when calculating the total electric field distribution in the main insulation system of the valve-side winding of an ultra-high-voltage direct current converter transformer. Design/methodology/approach To calculate the total electric field in an oil-paper insulation system, a new simulation method in single-layer oil-paper insulation based on the transient upstream finite element method (TUFEM) is proposed, in which the time variable is considered. The TUFEM is used to calculate the total electric field in an oil-paper insulation system by considering the move law of space charges. The simulation method is verified by comparing the simulation results to the test data. The move law of space charges and distribution characteristics of the electric field under difference voltage values in single-layer oil-paper insulation were presented. Findings The results show that the TUFEM has an excellent accuracy compared with the test data. When carrier mobility is a constant, the time to reach the steady state is inversely correlated with the initial electric field intensity, and the distortion rate of the internal total electric field is positively correlated with the initial electric field intensity. Originality/value This paper provides an exploratory research on the simulation of space charge transport phenomenon in oil-paper and has guiding significance to the design of oil-paper insulation.

The papers in this special issue present a selection of high quality research papers on wearable and flexible integrated sensors for screening, diagnostics, and treatment. Emerging flexible and wearable physical sensing devices create huge potential for many vital healthcare and biomedical applications including artificial electronic skins, physiological monitoring and assessment systems, therapeutic and drug delivery platforms, etc. Monitoring of vital physiological parameters in hospital and/or home environments has been of tremendous interests to healthcare practitioners for a long time. Robust and reliable sensors with excellent flexibility and stretchability are essential in the development of pervasive health monitoring systems with the capability of continuously tracking physiological signals of human body without conspicuous discomfort and invasiveness.

This paper provides a detailed derivation of the complete solution to an electromagnetic wave propagating along a thin wire parallel to the interface between two homogeneous half-spaces, and by extension for multiple parallel wires. The final solution presented in this paper extends the existing theory to include the effects of half-spaces with different magnetic permeabilities, the effects of wire/s with finite conductance, and in the multiconductor case the cross boundary mutual impedances. The latter is of particular importance when considering the coupling between power lines and buried continuously earthed systems, such as counterpoise conductors or buried metallic pipelines. Drawing on the numerous existing methodologies used to solve this problem, the derivation herein utilizes only a partial Fourier transform in combination with continuity conditions to achieve a general solution, which is novel. The solution is shown to agree with earlier works after appropriate restrictions are applied. The approach also serves as a review of some of the more fundamental works on the subject, contributes to understanding the limitations of existing theory, and establishes an alternate process for further extensions in the field.

This brief paper examines the problem of optimizing lithium-ion battery management online, in a health-conscious manner. This is a computationally intensive problem. Previous work by the authors addresses this challenge by exploiting the differential flatness of Fick’s law of diffusion to improve computational efficiency, but is limited by the fact that the dynamics of a full battery cell are not differentially flat, even when the individual battery electrode dynamics are. The brief paper addresses this challenge by extending the application of differential flatness to a full single particle model. In particular, we use the conservation of charge to express the flat output trajectory of one electrode as an affine function of the other electrode’s flat output trajectory. In this way, we enforce differential flatness for the full battery model. This makes it possible to express the battery charge/discharge trajectory in terms of one flat output trajectory. We optimize this trajectory using a pseudospectral method. This reduces the computational cost of the optimization by about a factor of 5 compared with pseudospectral optimization alone. In addition, the robustness of the nonlinear model predictive control strategy is demonstrated in simulation by adding state-of-health parameter uncertainties.

This paper deals with those measures against overvoltage taken when protecting buildings occupied by people or animals. Such overvoltages can appear in the case of ground fault if the grounding system of the building is located within a potential funnel of a transmission tower's grounding system. This paper presents an entire concept regarding protection against any potential rise within the building. Computations of electrical potential on the grounding system having been performed using data obtained by measurements. This includes equipotential bonding, overvoltage protection of the building, and a transformer substation with metal–oxide varistors and gas-discharge arresters installed on the low-voltage line. A simulation model for the entire overvoltage protection based on known mathematical models has been merged within this paper. Adequate overvoltage protection elements were selected for protection against potential rises in the grounding systems of buildings on the basis of computation results.

This paper presents a novel two-row interdigitating-finger repulsive-torque electrostatic actuator and its application to the micromirror vector display. The actuator consists of upper and lower rotation units and an output beam. Each unit has one row of rotation fingers, i.e., the lower and upper rotation fingers, which interdigitate with each other. The lower and upper rotation fingers are subject to different electric potentials. Each rotation finger and its underneath aligned fixed finger are subject to the same electric potential. The actuator generates repulsive torques to rotate the lower and upper fingers out-of-plane with the maximum rotation not limited either by the gap between fingers and the substrate nor by the pull-in effect. The output beam is connected to the lower row of rotation fingers, and therefore, the actuator has the same rotation as the lower unit. The actuator requires only two thin films and is suitable for surface micromachining. The model is established to verify the actuator and calculate its performance. Prototypes are fabricated and tested. The experimental results show that the actuator achieved a mechanical rotation of 11.5° at the static driving voltage of 150 V and a resonant frequency of 380 Hz with a sinusoidal driving voltage varying from 20 to 70 V. This paper demonstrates the application of the actuator in micromirror vector display. Four actuators are connected to the peripheries of a micromirror plate and independently controlled to drive the mirror plate to achieve quasi-static 2-D rotation. A laser beam is reflected and steered by the mirror plate to any desired direction to realize vector display. The prototype of the vector display micromirror is fabricated and tested. A vector display module integrating the micromirror, a laser, and a concave lens is built. Based on this module, an automotive head-up display system is developed, which is able to display the navigation map, speed, turning sign, and vehicle location on a translucent screen. [2015-0098]

This paper applies a rigorous electromagnetic model to determine the transient distribution of potentials along a substation earth grounding grid subjected to lightning currents. The obtained results show that, in the initial period of the transient, equipment pieces that are earth grounded at distinct points of the grid and are electrically linked (for example, by aerial communication cables) experience impulsive loop currents. Such loop currents can cause equipment malfunctions, failures, and damage. A remarkable conclusion of this paper is that such loop currents can reach substantial values even in the case of soils of low resistivity. Some practical aspects are highlighted in order to reduce the risks due to the nonuniform distribution of potentials along earth grounding.

The groundings of the power distribution, signaling, and power systems of a railway system are individually performed to realize fail safe, and the groundings are often installed in close proximity. Thus, when a grounding electrode is invaded by a lightning current, its ground potential rises together with the potential of the adjacent grounding electrodes; hence, there is a possibility of a large overvoltage being applied to the connected devices. In this paper, we have investigated the potential spread between two rod-shaped electrodes widely used in the grounding of the power, signal, and distribution systems of a railway system using the finite-difference time-domain method. The results of this paper are organized in such a way that the extent of the potential spread to the neighboring grounding electrodes can be understood from information such as the grounding resistivity at the installation location of the ground electrode and the wavefront duration of the lightning current, and these findings will be useful for grounding design. We also investigate the effect of the insulator between two neighboring electrodes to prevent the potential spread.

The grounding system in a solar farm has unique characteristics due to its extended footprint and varying type of grounding components. The changing physical properties of the soil within the perimeter of a solar farm result in the nonuniform resistivity of the top soil layers. Measurements of the as-built grounding grid could indicate higher grounding resistance than that predicted by design. Once this difference is detected, it is the duty of the designer to modify the existing grounding grid such that the touch potential is below the limits specified by the applicable codes. This paper presents the analysis of the touch potentials in solar farms and also provides some recommendations to reduce these potentials when the grounding resistance is higher than that predicted by the design. An actual grounding grid design and field measurements are used in an example to illustrate the concepts introduced in this paper.

This paper presents an overview of the different solutions of electrospinning systems. 3D parameterized numerical models for these systems were prepared too. The 3D models allows to analyze the distribution of the electric field. In addition, examples of calculations for the analyzed systems in the form of electric field quantities distributions are also shown. In this paper the authors used COMSOL Multiphysics — multipurpose software platform for simulating physics-based problems.

This paper introduces seven-level Active Neutral-point-clamped (ANPC-7L) inverter first. Then, the paper decouples the two problems of floating capacitors voltage controlling and neutral-point potential balancing by using the concept of average state, proposes a novel neutral-point potential balancing model based on zero-sequence voltage injection. After that, two neutral-point potential balancing algorithms and their full controllable regions are derived respectively. Finally, the two neutral-point potential balancing algorithms are modified for real-time implementation for different modulation regions. The validity of the proposed neutral-point potential balancing model and algorithms are verified by experimental results from a 380 V/5 kW ANPC-7L inverter.

The paper aims at improving high-frequency drying chambers by increasing uniformity of the drying process. In this paper we demonstrate the research results of influence of the sizes of spaces and air gaps located between the vertical electrodes and a timber pile on the uniformity and the magnitude of an electric field strength in wood. It is shown that the elecrtomagnetic process in the cross sections of the timber pile may be described as a quasy-stationary. The corresponding mathematical apparatus describing the distribution of the field in a HF chamber is presented in the paper. Computational experiments were conducted with a help of the program complex “ELCUT”. The results of the experiments were processed by the methods of the experiment planning theory and statistical data analysis. The dependencies of the heterogeneity coefficient and the medium strength of the electric field in wood on the stated (given) geometrical parameters of the timber pile were defined. We came to particular conclusions about the degree of their impact on the electromagnetic field parameters.

As the first part of a two-paper series, this paper develops a three-dimensional model that describes corona discharge, turbulent flow, particle charging and tracking in electrostatic precipitators (ESP). To capture the shielding effects between discharge wires in a multi-wire ESP, the corona-discharge-induced space charge density at an arbitrary point between the discharge wire and grounded plates is specified as the sum of two components: (i) a uniform value on the wire surface which is resolved individually for each wire; and (ii) a space-dependent variation relative to the uniform part. The present model is solved with the finite element method and validated with experimental and numerical results from literature. Good agreement is obtained and illustrated in terms of distributions of electric potential, current density, electrohydrodynamic flow pattern, and particle trajectories, as well as corona current and particle collection efficiency. This validated model will be applied in Part II and integrated with the design-of-experiment approach to analyze both individual and interactive effects of design parameters on ESP performance. NRF (Natl Research Foundation, S’pore)

International audience; Dielectrophoresis is defined as the motion of an electrically polarisable particle in a non-uniform electric field. Current dielectrophoretic devices enabling sorting of cells are mostly controlled in open-loop applying a predefined voltage on micro-electrodes. Closed-loop control of these devices would enable to get advanced functionalities and also more robust behavior. Currently, the numerical models of dielectrophoretic force are too complex to be used in real-time closed-loop control. The aim of this paper is to propose a new type of models usable in this framework. We propose an analytical model of the electric field based on Fourier series to compute the dielectrophoretic force produced by parallel electrode arrays. Indeed, this method provides an analytical expression of the electric potential which decouples the geometrical factors (parameter of our system), the voltages applied on electrodes (input of our system), and the position of the cells (output of our system). Considering the Newton laws on each cell, it enables to generate easily a dynamic model of the cell positions (output) function of the voltages on electrodes (input). This dynamic model of our system is required to design the future closed-loop control law. The predicted dielectrophoretic forces are compared to a numerical simulation based on finite element model using COMSOL software. The model presented in this paper enables to compute the dielectrophoretic force applied to a cell by an electrode array in a few tenths of milliseconds. This model could be consequently used in future works for closed-loop control of dielectrophoretic devices

A 3D (three-dimensional) model of VRB (vanadium redox flow battery) with interdigitated flow channel design is proposed. Two different stack inlet designs, single-inlet and multi-inlet, are structured in the model to study the distributions of fluid pressure, electric potential, current density and overpotential during operation of VRB cell. Electrolyte flow rate and stack channel dimension are proved to be the critical factors affecting flow distribution and cell performance. The model developed in this paper can be employed to optimize both VRB stack design and system operation conditions. Further improvements of the model concerning current density and electrode properties are also suggested in the paper.

Three-level neutral-point-clamped (NPC) converters/inverters have become a popular topology for not only medium-voltage (1k–33k) but also low-voltage level industrial application because of its reduced transistor block voltage and lower output current distortion. The neutral point voltage balancing control is one of the important issues of NPC converter to ensure system operation since the voltage drift in neutral point could lead to low-frequency current distortion and increases the risk of over-voltage in power electronic semiconductor devices. This paper provides a zero-sequence voltage (ZSV) injection to charge and discharge electric potential in the upper or the lower capacitor for unipolar switching. In addition, a novel neutral point potential control by bipolar switching is presented in this paper, which has better control dynamic under pure reactive power operation. The concept of these two neutral point potential control methods will be introduced, and then the laboratory test results are presented for verification.

Vacuum Interrupters (VI's) which are the product of choice at medium voltages for interruption of fault currents are being actively considered and applied at transmission levels also. As the voltage levels increases, so do the stresses. Hence, the high voltage withstand performance of the vacuum interrupter becomes extremely significant and demands greater attention. The withstand and breakdown voltage behaviour of a vacuum gap is a strong function of the electrode's shapes and surface conditions. The shape of electrodes and other metallic objects in the vacuum gap determines the geometric enhancement factor, β g . Appropriate design of the electrode results in the lowering of β g and hence enhancement of withstand and breakdown voltages. The micro-protrusions present on the surface of the electrodes results in increase of the stress and this is accounted for by a factor called microscopic enhancement factor, β m . This influence can be reduced by removing or levelling-off these micro-protrusions. The process to remove these micro-protrusions is called seasoning or conditioning and is a standard process in the manufacturing cycle of a vacuum interrupter. Two types of seasoning are employed: current seasoning and voltage seasoning. This paper concentrates on the voltage seasoning and specifically, on the impulse voltage seasoning or conditioning. The paper first presents a theoretical treatment of the process of impulse conditioning. Next the paper present a case study of conditioning process performed on a VI with a relatively longer gap and multiple floating shields. These results are significant in the light of the fact the high voltage vacuum interrupter would be having large inter-electrode gaps, also multiple floating shields. The paper concludes with recommendations for the conditioning of contacts and shield using impulse voltages.

This paper reveals an early quasi-saturation (QS) effect attributed to the geometrical parameters in shallow trench isolation-type drain-extended MOS (STI-DeMOS) transistors in advanced CMOS technologies. The quasi-saturation effect leads to serious $g_{m}$ reduction in STI-DeMOS. This paper investigates the nonlinear resistive behavior of the drain-extended region and its impact on the particular behavior of the STI-DeMOS transistor. In difference to vertical DMOS or lateral DMOS structures, STI-DeMOS exhibits three distinct regions of the drain extension. A complete understanding of the physics in these regions and their impact on the QS behavior are developed in this paper. An optimization strategy is shown for an improved $g_{m}$ device in a state-of-the-art 28-nm CMOS technology node.

In order to equalize the electric potential distribution of the grounding grid surface, and improve the safety level of the grounding grid, method for optimal arrangement of conducts in the grounding grid is proposed in this paper. The calculation results about maximum touch voltages and mesh potentials show that the method can reduce touch voltage and equilibrium surface potential. It is shown that the design of the grounding grid is related to not only the soil environment, but also the rectangular shape. Comparing with other methods, the method proposed in the paper can reduce maximum touch voltage about 12%. This method also can be applied in a uniform and non-uniform soil, rectangular and square grounding grids. The optimize effect meets the related standards of the power industry.

This paper presents a study about temperature effect on the conducted susceptibility level of a microcontroller. Based on direct power injection, the electromagnetic susceptibility of microcontroller is measured under different temperatures. Measurement results show that different temperature conditions could result in fluctuations of conducted susceptibility level. To analyze the temperature effect on susceptibility level, several potential threats in passive part, microcontroller input/output buffer and clock signal are presented in this paper.

A new-type of SF 6 gas-insulated HVDC wall bushing has been manufactured. The double-layer electrodes are introduced to grade electric fields instead of traditional capacitor foils. Therefore, the electric-field distribution of inner insulation is quite different from traditional productions as well as structure design. This paper presents finite element analysis (FEA) of this type of bushing. The features of inner electric-field distribution with main influence factors are discussed. In order to reduce electric-field strength on the surface of inner electrodes, this paper adopts generalized regression neural network (GRNN) and fast non-dominated sorting genetic algorithm (NSGA-II) to optimize the inner electrode design. First, optimization variables and constraint conditions are determined by electrical and geometrical specification. Then, GRNN is employed to rebuild and predict the objective functions. Finally, after NSGA-II optimization, the Pareto solutions are classified using a clustering algorithm in order to acquire the ultimate solution. Comparative checking for initial and optimal inner electrode design is performed by FEA. The results show that the electric-field strength on the surface of electrode is reduced. The electric field analysis and optimization results in this paper can give some directions for the design of SF 6 gas-insulated HVDC wall bushing.

Owing to the high voltage level, complex tower and insulator string structures, short phase distance and various arrangement forms of insulator string, the potential and electric field distribution of the insulator strings in 1000kV substation are more severe than that in transmission lines, and the voltage sharing characteristics of the insulator strings need to be researched deeply. With three dimensional finite element method, considering the influence of the tower, conductors, fittings and the interaction of three phases, this paper calculate the potential and electric field distribution of the V-type suspension ceramic insulator strings in 1000kV substation. The influence of grading ring, suspension status and mounting type to the potential distribution of insulator string is researched, the parameters of the grading ring including the diameter of grading ring, the mounting height of grading ring, and the tube diameter of grading ring are optimized, finally, the proper configuration of the grading ring applied to V-type suspension ceramic insulator strings in 1000kV substation was suggested. The research achievements by this paper have been successfully applied on the ultra high voltage (UHV) AC pilot project in China with great practical value to raise the reliability of the insulators and improve the electromagnetic environment in the 1000kV substations.

Bushing used for gas insulated switch-gears is a key equipment in GIS, which mainly uses SF6 as its insulating material. The electric field strength inside the bushing and at the surface of the bushing sheath could significantly influence the safety and stable operation. Firstly, the model of a 1000kV bushing inflated with SF6 is built. Finite element analysis is adopted to calculate the distribution of electric potential and electric field strength. Additionally, the electric field strengths of several pivotal positions of the bushing are compared between single-layer shield structure and double-layer shields structure. The double-layer shields structure which UHV bushings usually adopt could lower the electric field strength inside the bushing and at the surface of the bushing sheath. Furthermore, the height of the shield, radius of the turn-up at the top of the shield, the size and location of the grading ring are optimized. Conclusions are listed. The bushing that the paper researches on has passed all type tests. The conclusions of this paper could provide theoretical guidance for the structure design of GIS bushings.

Based on the optimization idea of the electric field from the surface to the bulk, this paper summarizes the basic theory and the two types of analytical optimization methods of the super junction (SJ) device. The essential difference between the SJ and the conventional power MOS structure is: the former is the junction-type voltage sustaining layer with the periodic N/P dopings and the later is the resistance-type voltage sustaining layer with the single conductive type. The positive and negative charges satisfying the charge balance are introduced into the SJ voltage sustaining layer, which causes the two-dimensional electric field to realize the optimization from the surface to the bulk. The paper gives the concepts of the charge and potential electric fields, analyzes the non-full depletion and full depletion modes, introduces the mechanism of the transient process and forward biased safe operating area, discusses the equivalent substrate model and the optimized substrate conditions. Finally, the minimum specific on-resistance R on,min optimization methodology is proposed to give the R on,min for a given breakdown voltage V B. R on of the SJ is decreased significantly compared to that of the conventional power MOS with the same V B. The R on -V B relationship changes from the R on∝ V B2.5 to V B1.32 even V B1.03, leading to the SJ as the “milestone in high voltage power MOS device”

Plasma nitriding is a widely used technology to enhance the surface performance and extend the service life of alloy parts. The current research mainly focuses on the influences of time, temperature, gas type and pressure parameters on nitriding behavior, while fewer studies have been conducted on the electric potential. This paper mainly reports the effect of the electric potential on nitriding behavior. Test conditions were set using cathodic, anodic and floating potentials in a plasma nitriding furnace. 2Cr13 stainless steel was nitrided at 450 °C for 5 h in an NH3 atmosphere. The experimental results show that the nitriding treatment can be well performed under the different electric potentials, but differences exist in microstructures, morphologies and performance results of the modified layers. The thickness and hardness values of the nitrided layer are ranked as follows: cathodic > anodic > floating potential. The anodic nitrided surface has an obvious particle deposition layer composed of nitrides and oxides. Electrochemical and tribological experiments show that the corrosion resistance and wear resistance were significantly improved after a nitriding treatment using the three electric potentials. Moreover, the floating nitriding treatment resulted in the best tribological performance and corrosion resistance.

The paper deals with the development of manufacturing methods of improving the functionality and reliability of the electric contact made of titanic VT3-1 alloy. This alloy is used in the development of electrical contacts for acoustic beacons used on airplanes of various airline companies. Solving the problem of increasing the life of acoustic beacons (up to 90 days) is directly related to an increase in the stability of the electrochemical characteristics of the contact. To ensure the stable behavior of the electric potential (not more than 0.5V) at the contact, a method of gas-dynamic spraying of a protective coating based on nickel of increased thickness is proposed. Single-layer and two-layer coatings obtained from different grades of powder mixtures were tested. The regularities of the process of electrochemical breakdown and passivation of protective coatings during comparative short-term tests were studied. Based on the test results, a single-layer gas-dynamic coating of the composition(Ni + Al2O3) formed from the powder mixture of grade N3-00-02 was chosen. The microstructure, phase composition, microhardness, porosity and adhesive strength of Ni-based protective coating were investigated. Electrochemical tests of electrical contact with the investigated coating in the sea water environment depending on the time factor were carried out. Increased thickness of the coatings combined with low open porosity and high adhesive strength provided stable behavior of the electric potential in the process of applying it to the working surface of the titanium alloy contacts VT3-1. This ensures reliable electrochemical protection of contacts in the sea water environment for 90 days.

Due to the serious charge accumulation at gas-solid interface, the surface flashover voltage of insulator in gas insulated equipment may be significantly reduced. In order to pursue a method inhibiting surface charge accumulation, the epoxy composites modified by nano-SiC particles were coated on the insulator surface in this paper. The thickness of coating was 300 μm, and the SiC content was 5, 7 and 10 wt%. With the help of a couple of finger-shaped electrodes, the insulators with different coatings were charged at −10 kV voltage, and then the dynamic surface potential distributions were investigated. The results showed that only positive potential appeared on the surface and it mainly distributed near the high voltage electrode. With the passage of charging time, the shrinking phenomenon of high-potential region and the expansion of low-potential region can be observed. In addition, with the increase of SiC content, the average value of surface potential decreased monotonously and the shrinking speed of high-potential region seemed to be increased. Especially when the SiC content rose to 7 and 10 wt%, the magnitude and distribution area of surface potential declined sharply from 40 to 60 min. After 60 min, the surface potential distribution of the insulator with 5 wt% SiC/Epoxy coatings nearly unchanged, whereas it remained a slight fluctuation with 7 and 10 wt% fillers. Our study indicates that the coating with nano-SiC fillers has an inhibition effect on surface charge accumulation.

This paper describes the developed direct current circuit breaker with the grid method (DC CBG). The simplified DC CBG was designed and constructed. It comprises the third electrodes, as the grid of a triode, installed between the main contact electrodes. Moreover, the special-designed transformer (SDT) was designed and constructed to supply a damping high-voltage pulse to the grid electrode for suppressing the arc current. The experiment was conducted to verify the performance of the designed DC CBG. Experimental results show that the amplitude of the arc current was significantly reduced by approximately 94% after the damping high-voltage pulse generated from the SDT was applied to the third electrode. Therefore, the proposed DC CBG has the ability to be developed for practical use in the future.

International audience; Marine renewable energies (MRE) allow the diversification of the energy mix and are thus developing rapidly. The extraction of tidal energy is one of the most promising MRE and is nowadays in a preindustrial phase. The Alderney Race (Raz Blanchard in French), situated between the island of Alderney (Channel Islands) and the Cap de la Hague in France, capitalizes a resource estimated between 5 and 14 TWh/year. This great tidal resource attracts tidal energy developers. Harnessing the high potential of the Alderney Race requires deploying numerous turbines in arrays. The purpose of this paper is to investigate the influence of the wake effects on the electrical dynamics of commercial tidal farms. The proposed methodology is applied to a hypothetical tidal farm in the Alderney Race. The influence of the wake effects on the power produced by a tidal farm is assessed by comparing simulations where the effect is neglected to simulations with wake effects. Two operational conditions are analyzed: Normal operation (one-day simulation with varying tidal speed); grid disturbances (voltage dip at the tidal farm point of common coupling). Simulations show that neglecting the wake effect implies significant errors in active power estimation at the point of common coupling during normal operation. Moreover, differences in the behavior of the system during voltage dip occur if the wake effect is not taken into account.

Low-alloy steels used as structural materials in nuclear power plants are subjected to cyclic stresses during power plant operations. As a result, cracks may develop and propagate through the material. The alternating current potential drop technique is used to measure the lengths of cracks in metallic components. The depth of the penetration of the alternating current is assumed to be small compared to the crack length. This assumption allows the adoption of the unfolding technique to simplify the problem to a surface Laplacian field. The numerical modelling of the electric potential and current density distribution prediction model for a compact tension specimen and the unfolded crack model are presented in this paper. The goal of this work is to conduct numerical simulations to reduce deviations occurring in the crack length measurements. Numerical simulations were conducted on AISI 4340 low-alloy steel with different crack lengths to evaluate the electric potential distribution. From the simul...

Online condition monitoring of power transmission belts is essential to keep industrial belt-driven equipment functioning smoothly and reliably. This paper presents a smart electrostatic sensor that monitors belt motion through detection of static charge on the belt. A theoretical model is established using the method of moments for calculation of induced charge on strip-shaped electrodes placed in the vicinity of a belt moving both axially and transversely. The sensor unit converts the induced charge into proportional voltage signals using charge amplifiers and measures belt speed and vibration through cross correlation and spectral analysis, respectively. The performance of the smart electrostatic sensor is validated against a photoelectric rotary encoder and a laser displacement sensor. Comparative experimental results show that the belt speed can be measured with a relative error within ±2% over the range 1.7-15.5 m/s. The electrostatic sensor is capable of measuring the frequencies of transverse vibration accurately. Although absolute displacement cannot be measured due to the uncertain level of charge on the belt, the measurement results of relative vibration magnitudes for different modes and at different belt speeds are reasonably accurate.

Grounding resistance is an important basic index used to ensure the safety and reliability of grounding systems. In this paper, a method for grounding resistance measurement based on the fall of potential curve is proposed that can be performed using a 2–2.5D lead wire length. In this method, the potential distribution near the auxiliary current electrode is tested and is used as the main analysis and measurement parameter. Based on the relationship between the potential distribution generated by the grounding grid and the current electrode, the grounding resistance of the grounding grid can be deduced. First, the voltages between the grounding grid and the earth surface potential near the current electrode are measured; then, the ground potential rise (GPR) of the grounding grid is calculated through theoretical analysis and numerical calculation; and finally, the grounding resistance is calculated by dividing the potential by the test current. This method avoids the complex task of accurate compensation point location required for traditional measurement methods, and can be performed easily and quickly using a short lead wire. Measurement results from spot testing show that the proposed method can meet the accuracy requirements of engineering testing.

This paper presents an improved calibration setup for static bridge standards with a carrier frequency supply voltage in the frequency range between 225 Hz and 5 kHz. In the past, the small bridge differential voltage in the mV/V range was calibrated in two subsequent voltage ratio calibrations. However, this procedure is time-consuming and only works reliably if both voltages are stable over time. For this purpose, a new setup was developed that is able to measure the differential voltage of the bridge standard in one single measurement. This reduces the calibration time by approximately two thirds, thereby also reducing the uncertainty.