scholarly journals Simulation and Modelling of Transient Electric Fields in HVDC Insulation Systems Based on Polarization Current Measurements

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8323
Author(s):  
Pasquale Cambareri ◽  
Carlo de Falco ◽  
Luca Di Rienzo ◽  
Paolo Seri ◽  
Gian Carlo Montanari
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Physical Models ◽  
Polarization Current ◽  
Polarization Model ◽  
Steady State Condition ◽  
Electrical Systems ◽  
Insulation Systems ◽  
Voltage Transients ◽  
The Impact

Simulating and modelling electric field dynamics in the insulation of medium- and high-voltage DC electrical systems is needed to support insulation design optimization and to evaluate the impact of voltage transients on ageing mechanisms and insulation reliability. In order to perform accurate simulations, appropriate physical models must be adopted for the insulating material properties, particularly conductivity, which drives the electric field in a steady-state condition and contributes to determining the field behavior during voltage and load transients. In order to model insulation conductivity, polarization, and conduction, mechanisms must be inferred through charging and discharging current measurements, generally performed at different values of electric field and temperatures in flat specimens of the material under study. In general, both mechanisms are present, but one of them may be predominant with respect to the other depending on type of material. In this paper, we showed that models based on predominant polarization mechanisms were suitable to describe impregnated paper, but not polymers used for HV and MV DC insulation. In the latter case, indeed, trapping–detrapping and conduction phenomena were predominant compared to polarization, thus conductivity models had to be considered, in addition to or as a replacement of the polarization model, in order to carry out proper electric field simulations.

scholarly journals Restraining Surface Charge Accumulation and Enhancing Surface Flashover Voltage through Dielectric Coating

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 750
Author(s):  
Jixing Sun ◽  
Sibo Song ◽  
Xiyu Li ◽  
Yunlong Lv ◽  
Jiayi Ren ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electric Field ◽  
Electric Fields ◽  
Transition Process ◽  
Metallic Particle ◽  
Particle Charging ◽  
Insulating Surfaces ◽  
Surface Flashover ◽  
Charging Time ◽  
The Impact

A conductive metallic particle in a gas-insulated metal-enclosed system can charge through conduction or induction and move between electrodes or on insulating surfaces, which may lead to breakdown and flashover. The charge on the metallic particle and the charging time vary depending on the spatial electric field intensity, the particle shape, and the electrode surface coating. The charged metallic particle can move between the electrodes under the influence of the spatial electric field, and it can discharge and become electrically conductive when colliding with the electrodes, thus changing its charge. This process and its factors are mainly affected by the coating condition of the colliding electrode. In addition, the interface characteristics affect the particle when it is near the insulator. The charge transition process also changes due to the electric field strength and the particle charging state. This paper explores the impact of the coating material on particle charging characteristics, movement, and discharge. Particle charging, movement, and charge transfer in DC, AC, and superimposed electric fields are summarized. Furthermore, the effects of conductive particles on discharge characteristics are compared between coated and bare electrodes. The reviewed studies demonstrate that the coating can effectively reduce particle charge and thus the probability of discharge. The presented research results can provide theoretical support and data for studying charge transfer theory and design optimization in a gas-insulated system.

scholarly journals Nonperturbative Kinetic Description of Electron-Hole Excitations in Graphene in a Time Dependent Electric Field of Arbitrary Polarization

Particles ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 208-230 ◽  
Author(s):  
Stanislav A. Smolyansky ◽  
Anatolii D. Panferov ◽  
David B. Blaschke ◽  
Narine T. Gevorgyan
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Kinetic Equations ◽  
Nonlinear Effects ◽  
Two Dimensions ◽  
Time Dependent ◽  
Polarization Current ◽  
Kinetic Description ◽  
Orthogonal Direction ◽  
Electron Hole

On the basis of the well-known kinetic description of e − e + vacuum pair creation in strong electromagnetic fields in D = 3 + 1 QED we construct a nonperturbative kinetic approach to electron-hole excitations in graphene under the action of strong, time-dependent electric fields. We start from the simplest model of low-energy excitations around the Dirac points in the Brillouin zone. The corresponding kinetic equations are analyzed by nonperturbative analytical and numerical methods that allow to avoid difficulties characteristic for the perturbation theory. We consider different models for external fields acting in both, one and two dimensions. In the latter case we discuss the nonlinear interaction of the orthogonal currents in graphene which plays the role of an active nonlinear medium. In particular, this allows to govern the current in one direction by means of the electric field acting in the orthogonal direction. Investigating the polarization current we detected the existence of high frequency damped oscillations in a constant external electric field. When the electric field is abruptly turned off residual inertial oscillations of the polarization current are obtained. Further nonlinear effects are discussed.

scholarly journals Numerical Calculation of Electric Fields in Housing Spaces Due to Electromagnetic Radiation from Antennas for Mobile Communication

10.14311/478 ◽  
2003 ◽  
Vol 43 (5) ◽  
Author(s):  
H.-P. Geromiller ◽  
A. Farschtschi
Keyword(s):  
Electromagnetic Wave ◽  
Electric Field ◽  
Electromagnetic Radiation ◽  
Electric Fields ◽  
Mobile Communication ◽  
Signal Frequency ◽  
High Signal ◽  
Maximum Value ◽  
Mobile Antennas ◽  
The Impact

The influence of electromagnetic radiation from mobile antennas on humans is under discussion in va'rious groups ofscientists, This paper deals with the impact ofelectromagnetic radiation in a housing space. The space is assumedto be bordered by 5 walls of ferroconcrete and a door-window combination on the 6th side, the latter to be electromagnetically transparent. The transparent side of the housing is exposed to an electromagnetic wave. As the source ofradiation is considered to be far away from the housing, the radiation is regarded to be from a plane wave. Due to the high signal frequency and ferroconcrete walls, 5 sides ofthe housing space are considered to be perfect conductors. The electric field inside the housing is calculated numerically by the method of finite differences for different angles of incidence of the radiated electromagnetic wave. The maximum value of the calculated electric field is outlined in a diagram.

scholarly journals Impact of disturbance electric fields in the evening on prereversal vertical drift and spread F developments in the equatorial ionosphere

2018 ◽  
Vol 36 (2) ◽  
pp. 609-620 ◽  
Author(s):  
Mangalathayil A. Abdu ◽  
Paulo A. B. Nogueira ◽  
Angela M. Santos ◽  
Jonas R. de Souza ◽  
Inez S. Batista ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Plasma Bubble ◽  
Large Variability ◽  
Plasma Drift ◽  
F Region ◽  
Vertical Drift ◽  
Spread F ◽  
The Impact ◽  
Magnetic Disturbances

Abstract. Equatorial plasma bubble/spread F irregularity occurrence can present large variability depending upon the intensity of the evening prereversal enhancement in the zonal electric field (PRE), that is, the F region vertical plasma drift, which basically drives the post-sunset irregularity development. Forcing from magnetospheric disturbances is an important source of modification and variability in the PRE vertical drift and of the associated bubble development. Although the roles of magnetospheric disturbance time penetration electric fields in the bubble irregularity development have been studied in the literature, many details regarding the nature of the interaction between the penetration electric fields and the PRE vertical drift still lack our understanding. In this paper we have analyzed data on F layer heights and vertical drifts obtained from digisondes operated in Brazil to investigate the connection between magnetic disturbances occurring during and preceding sunset and the consequent variabilities in the PRE vertical drift and associated equatorial spread F (ESF) development. The impact of the prompt penetration under-shielding eastward electric field and that of the over-shielding, and disturbance dynamo, westward electric field on the evolution of the evening PRE vertical drift and thereby on the ESF development are briefly examined. Keywords. Ionosphere (ionospheric irregularities)

Effectiveness of Pulsed Electric Fields in Controlling Microbial Growth in Milk

2008 ◽  
Vol 4 (7) ◽  
Author(s):  
Adedayo Otunola ◽  
Ayman El-Hag ◽  
Shesha Jayaram ◽  
William A Anderson
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Milk Fat ◽  
Indigenous Population ◽  
Inoculum Size ◽  
Microbial Inactivation ◽  
Log Reduction ◽  
The Impact

A study was conducted to assess the effectiveness of pulsed electric field (PEF) inactivation of a heterogeneous community of microbes. The aim was to assess the impact of process parameters on an indigenous population of microbes present in milk, rather than pure cultures used in other studies. Tests over an electric field strength range of 10 – 40 kV/cm and 10 to 120 pulses per millilitre showed that high electric field strength and pulse number inactivated microbes by up to approximately 2 log. Inoculum size affected PEF effectiveness when only a few pulses were applied. A significant log-reduction was achieved against the indigenous microbes found in milk that were apparently recalcitrant to commercial pasteurization. Microbial inactivation was more extensive when E. coli was not added to the indigenous population, indicating that the added pure culture was more resistant than the indigenous microbes. The milk fat content had a significant negative effect on the extent of log-reduction for indigenous microbes, when 2% and 18% levels were compared.

scholarly journals Comparative Analysis of the Various Generalized Ohm's Law Terms in Magnetosheath Turbulence as Observed by Magnetospheric Multiscale

2021 ◽  
Author(s):  
Julia Stawarz ◽  
Lorenzo Matteini ◽  
Tulasi Parashar ◽  
Luca Franci ◽  
Jonathan Eastwood ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Electron Mass ◽  
Turbulent Fluctuation ◽  
Electron Pressure ◽  
Ohm’S Law ◽  
Magnetospheric Multiscale ◽  
Ohm's Law ◽  
Turbulent Plasmas ◽  
The Impact

<p><span>Electric fields (<strong>E</strong>) play a fundamental role in facilitating the exchange of energy between the electromagnetic fields and the changed particles within a plasma. </span>Decomposing <strong>E</strong> into the contributions from the different terms in generalized Ohm's law, therefore, provides key insight into both the nonlinear and dissipative dynamics across the full range of scales within a plasma. Using the unique, high‐resolution, multi‐spacecraft measurements of three intervals in Earth's magnetosheath from the Magnetospheric Multiscale mission, the influence of the magnetohydrodynamic, Hall, electron pressure, and electron inertia terms from Ohm's law, as well as the impact of a finite electron mass, on the turbulent electric field<strong> </strong>spectrum are examined observationally for the first time. The magnetohydrodynamic, Hall, and electron pressure terms are the dominant contributions to <strong>E</strong> over the accessible length scales, which extend to scales smaller than the electron gyroradius at the greatest extent, with the Hall and electron pressure terms dominating at sub‐ion scales. The strength of the non‐ideal electron pressure contribution is stronger than expected from linear kinetic Alfvén waves and a partial anti‐alignment with the Hall electric field is present, linked to the relative importance of electron diamagnetic currents within the turbulence. The relative contributions of linear and nonlinear electric fields scale with the turbulent fluctuation amplitude, with nonlinear contributions playing the dominant role in shaping <strong>E</strong> for the intervals examined in this study. Overall, the sum of the Ohm's law terms and measured <strong>E</strong> agree to within ∼ 20% across the observable scales. The results both confirm a number of general expectations about the behavior of <strong>E</strong> within turbulent plasmas, as well as highlight additional features that may help to disentangle the complex dynamics of turbulent plasmas and should be explored further theoretically.</p>

scholarly journals Time-Dependent Electric Field Distribution in Layered Paper-Oil Insulation

2019 ◽  
pp. 58-63 ◽  
Author(s):  
Gunnar Håkonseth ◽  
Erling Ildstad
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Electric Fields ◽  
Current Density ◽  
Test Object ◽  
Dielectric Response ◽  
Electric Field Distribution ◽  
Time Dependent ◽  
Polarization Current ◽  
Dependent Polarization

Layered paper–oil insulation is used in several types of HVDC equipment. In order to better understand breakdown mechanisms and optimize the design, it is important to understand the electric field distribution in the insulation. In the present work, a test object with such insulation has been modeled as a series connection of oil and impregnated paper. The permittivity, conductivity, and the dielectric response function has been measured for impregnated paper and oil separately and used as parameters in a dielectric response model for the layered insulation system. A system of differential equations has been established describing the voltages across each material, i.e. across each layer of the test object. These equations have been solved considering a DC step voltage across the whole test object. Based on this, the time-dependent electric field in each material as well as the time-dependent polarization current density in the test object have been calculated. The calculated polarization current density was found to agree well with the measured polarization current density of the test object. This indicates that application of dielectric response theory gives a good estimate of the time-dependent electric field distribution in layered insulation systems. The results show that 90 % of the change from initial values to steady-state values for the electric fields has occurred within the first 35 minutes after the voltage step. This applies to the electric fields in both of the materials of the examined test object at a temperature of 323 K.

Bubble Formation and Detachment Under the Influence of Electric Fields and the Role of Gravity

2005 ◽  
Author(s):  
C. Herman ◽  
Z. Liu ◽  
E. Iacona
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Heated Surface ◽  
Gravity Level ◽  
Reduced Gravity ◽  
Bubble Behavior ◽  
Transfer Coefficients ◽  
High Heat Transfer ◽  
The Impact ◽  
Bubble Removal

Boiling is an attractive solution to cooling problems in aerospace engineering because of the high heat transfer coefficients associated with phase change processes. Bubble detachment from an orifice shows some resemblance to bubble departure in boiling. The buoyancy force is responsible for bubble removal from the surface in terrestrial conditions. In space, with the gravity level being orders of magnitude smaller than on earth, bubbles formed during boiling can remain attached to the surface. As a result, the amount of heat removed from the heated surface can decrease, and it is difficult to predict reliably and accurately. The impact of electric fields is investigated with the aim to control bubble behavior and help bubble removal from the surface on which they form in reduced gravity. The behavior of single gas bubbles injected through an orifice into an electrically insulating liquid is studied in reduced gravity under the influence of static electric fields and the results of the experiments are compared with data obtained using a simplified model. The bubble life cycle was visualized in terrestrial conditions and reduced gravity. Bubble departure, volume and dimensions at detachment were measured and analyzed for different parameters such as gravity level, electric field magnitude and electric field uniformity. Results suggest that these parameters significantly affect bubble behavior, shape, volume and dimensions at detachment.

scholarly journals The influence of circulation weather types on the exposure of the biosphere to atmospheric electric fields

2020 ◽  
Vol 65 (1) ◽  
pp. 93-105 ◽  
Author(s):  
K. Kourtidis ◽  
K. Szabóné André ◽  
A. Karagioras ◽  
I.-A. Nita ◽  
G. Sátori ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Field Potential ◽  
Low Frequency ◽  
Potential Gradient ◽  
Human Condition ◽  
Weather Types ◽  
Mean Values ◽  
Using Data ◽  
The Impact

AbstractWe present an analysis of the impact of circulation weather types (CT) on a factor that might influence biological systems and the human condition, the electric state of the atmosphere. We present results on the influence of CT to the magnitude, the direction (positive or negative), the fluctuation magnitude, and the short-term peaks of the atmospheric electric field (potential gradient, PG), using data from a station in Greece. CTs with high vorticity centers over Greece are associated with high positive and negative excursions of the PG, higher PG variability, and rain events. CTs with thinner 850–500 hPa layer are associated with higher daily mean values of fair-weather PG. We also examine the influence of CT on the frequency and amplitude of the naturally occurring extremely low-frequency electric field fluctuations known as Schumann resonances (SR) using data from a station in Hungary. The first and second mode SR frequencies are increased during CTs associated with higher 500 hPa geopotential heights and higher 850–500 hPa layer thickness. This hints to a lower-upper atmosphere coupling. So, CTs not only influence the general temperature and humidity conditions to which the biosphere is exposed, but they also affect its exposure to atmospheric electric fields.

scholarly journals Effects of the airwave in time-domain marine controlled-source electromagnetics

Geophysics ◽  
2011 ◽  
Vol 76 (4) ◽  
pp. F251-F261 ◽  
Author(s):  
Jürg Hunziker ◽  
Evert Slob ◽  
Wim Mulder
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Time Domain ◽  
Beam Steering ◽  
Data Set ◽  
Controlled Source ◽  
Controlled Source Electromagnetics ◽  
Subsurface Reservoir ◽  
The Impact ◽  
Depth Water

In marine time-domain controlled-source electromagnetics (CSEM), there are two different acquisition methods: with horizontal sources for fast and simple data acquisition or with vertical sources for minimizing the effects of the airwave. Illustrations of the electric field as a function of space and time for various source antenna orientations, based on analytical formulation of the electric field in two half-spaces, provide insights into the properties of the airwave and the nature of diffuse electric fields. Observing the development of the electric field over time and space reveals that diffusive fields exhibit directionality. Therefore, techniques that have thus far mostly been applied to wavefields can be adapted for CSEM. Examples range from the well-known up-down decomposition to beam steering. Vertical sources have the advantage of not creating an airwave. On the other hand, it is quite difficult to achieve perfect verticality of the source antenna. Results, using a numerically modeled data set to analyze the impact of the airwave on a signal from a subsurface reservoir in the case of a slightly dipping vertical source, indicate that already for a dip of [Formula: see text], the airwave contributes 20% to the complete electric field in our configuration of reservoir depth, water thickness, and conductivity values.

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