Electric field and current density in the impulse corona discharge in a rod/plane gap

1968 ◽  
Vol 304 (1477) ◽  
pp. 187-210 ◽  
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Electric Fields ◽  
Current Density ◽  
Plane Surface ◽  
Discharge Process ◽  
Conduction Current ◽  
Charge Densities ◽  
Charge Field ◽  
Current Densities

Measurements have been made of corona discharges in positive rod/earthed plane systems subjected to impulse voltages up to 200 kV. For this an electrostatic fluxmeter for the examination of electric fields and charge densities present in the corona has been developed and used. Measurements of electric fields and current densities so obtained during the discharge are compared with conventional measurements of total current densities. These show that the transient at the centre of the plane is a double pulse of time separation 0.1 to 1.0 μ s. The first pulse is shown by the fluxmeter to be due to induced charge on the plane surface and the second to electron emission from the surface. At the plane electrode the space charge electric field can be as great as 8 kV/cm, and the conduction current density in the corona 45 A/m 2 . The duration of the decaying space-charge field is several seconds. The construction, calibration and synchronization of the fluxmeter, which can measure electric fields down to 10 V/cm with a time resolution of 0.5 ms, are described. The principles of the device in separating the displacement and conduction current com­ponents in the discharge process are discussed.

Maximum ion currents from flames and the maximum practical effects of applied electric fields

1964 ◽  
Vol 277 (1371) ◽  
pp. 468-497 ◽  
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Electric Fields ◽  
Laminar Flames ◽  
Limiting Current ◽  
Ion Currents ◽  
Forming Process ◽  
Ion Generation ◽  
Two Factors ◽  
Current Densities

The maxima limiting all practical effects of the movement of flame ions in electric fields are shown to depend on the current densities available. The theory of the electric field and space charge distributions inside and outside the flame is developed, checked experimentally, and used to deduce such maxima. Two factors are identified as limiting current densities; the rate of ion generation per unit flame area and the space charge-induced breakdown at the electrodes. The latter is shown to be ultimately limiting and the theory is used to calculate numerical values for all practical maxima. The former is limiting only in some flat laminar flames parallel to electrodes, but it leads to a method of measuring rates of ion generation in flames. The method is developed experimentally on the basis of the theory and applied to a series of hydrocarbon/air and hydrogen/hydrocarbon/air flames. As an example of its use, the results are applied to calculations of activation energies and orders of the ion-forming process.

scholarly journals DETERMINATION OF ELECTRIC FIELD IN TERMS OF CURRENT AND CHARGE BY THE CONTINUITY EQUATION APPROACH

2019 ◽  
Vol 7 (4) ◽  
pp. 162-170
Author(s):  
Pitri Bhakta Adhikari
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Electric Fields ◽  
Current Density ◽  
Continuity Equation ◽  
Equation Approach ◽  
Speed Of Light ◽  
Extended Charge ◽  
Current Densities

To determine an expression for the electric field in terms of current density and charge density is used the continuity equation approach. In this approach, the expression of electric field using scalar and vector potential relates the charge density and current density. The major consequence of these equations is that they visualize how varying electric fields propagate at the speed of light. In Maxwell's electrodynamics, formulated as it is in terms of charge and current densities, a point charge must be regarded as the limit of an extended charge, when the size goes to zero. Hence, the total electric field at the point P is

scholarly journals Statistical Study on Space Charge effects and Stage Characteristics of Needle-Plate Corona Discharge under DC Voltage

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2732 ◽  
Author(s):  
Disheng Wang ◽  
Lin Du ◽  
Chenguo Yao
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Corona Discharge ◽  
Discharge Process ◽  
Space Charge Effects ◽  
Discharge Characteristics ◽  
Charge Effects ◽  
Dc Voltage ◽  
Field Distributions ◽  
Space Charges

The air’s partial discharges (PD) under DC voltage are obviously affected by space charges. Discharge pulse parameters have statistical regularity, which can be applied to analyze the space charge effects and discharge characteristics during the discharge process. Paper studies air corona discharge under DC voltage with needle-plate model. Statistical rules of repetition rate (n), amplitude (V) and interval time (∆t) are extracted, and corresponding space charge effects and electric field distributions in PD process are analyzed. The discharge stages of corona discharge under DC voltage are divided. Furthermore, reflected space charge effects, electric field distributions and discharge characteristics of each stages are summarized to better explain the stage discharge mechanism. This research verifies that microcosmic process of PD under DC voltage can be described based on statistical method. It contributes to the microcosmic illustration of gas PD with space charges.

scholarly journals Charge Densities above Pulsar Polar Caps

2000 ◽  
Vol 177 ◽  
pp. 463-464
Author(s):  
A. Jessner ◽  
H. Lesch ◽  
Th. Kunzl
Keyword(s):  
Neutron Star ◽  
Electric Field ◽  
Work Function ◽  
Potential Barrier ◽  
Electric Fields ◽  
Surface Potential ◽  
Thermal Emission ◽  
Equilibrium Density ◽  
Charge Densities ◽  
Polar Caps

A simplified model provided the framework for our investigation into the distribution of energy and charge densities above the polar caps of a rotating neutron star. We assumed a neutron star withm= 1.4M⊙,r= 10km, dipolar field |B0| = 1012G,B||Ω and Ω = 2Π · (0.5s)−1. The effects of general relativity were disregarded. The induced accelerating electric fieldE||reachesE0= 2.5 · 1013V m−1at the surface near the magnetic poles. The current density along the field lines has an upper limitnGJ, when the electric field of the charged particle flow cancels the induced electric field: At the polesnGJ(r=rns,θ= 0) = 1.4 · 1017m−3.The work function(surface potential barrier)EWis approximated by the Fermi energyEFof magnetised matter. Following Abrahams and Shapiro (1992) one needs to revise the surface density from the canonical 1.4 · 108kg m−3down toρFe = 2.9 · 107kg m−3. Withwe obtain a value ofEF=Ew= 417eV. There are two relevant particle emission processes:Field (cold cathode) emissionby quantum-mechanical tunneling of charges through the surface potentialandthermal emissionwhich is a purely classical process. In strong electric fields it is enhanced by the lowering of the potential barrier due to the Schottky effect. The combined Dushman-Schottky equationwithtells us, thatat temperatures> 2 · 105K the the Goldreich-Julian current can be supplied thermal emission alone. The surface temperature however has a lower limit in the order of 105K due to the rotational braking. Therefore, in most cases a sufficient supply of charges for the Goldreich-Julian current is available and the electrical field accelerating the particles will be quenched as a result of their abundance. Otherwise a residual equilibrium electric field Eeqremains with:and hence the equilibrium density is:n=nfieid(Eeq,EW) +nDS(Eeq,EW,T) For a temperature just below the onset of thermal emission (T= 1.85 · 105K) the charge density is found to vary almost linearly with the work functionEWfor values ofEWbetween 0.3 and 2 keV. At the chosen value forEWof 417 eVthe residual electric field amounts to only 8.5% of the vacuum value. Even in the residual electric field the particles are rapidly accelerated to relativistic energies balanced by inverse Compton and curvature radiation losses.

How does dissipation work in the electron diffusion region of asymmetric magnetic reconnection

2020 ◽  
Author(s):  
Michael Hesse ◽  
Cecilia Norgren ◽  
Paul Tenfjord ◽  
James Burch ◽  
Yi-Hsin Liu ◽  
...  
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Stagnation Point ◽  
Electric Fields ◽  
Current Density ◽  
Electron Flow ◽  
Diffusion Region ◽  
Density Maximum ◽  
Density Peak ◽  
Electron Diffusion

<p>At some level, magnetic reconnection functions by means of a balance between current dissipation, and current maintenance due to the reconnection electric field. While this dissipation is well understood process in symmetric magnetic reconnection, the way nonideal electric fields interact with the current density in asymmetric reconnection is still unclear. In symmetric reconnection, the current density maximum, the X point location, and the nonideal electric field determined by the divergence of the electron pressure tensor usually coincide. In asymmetric reconnection, however, the electric field at the X point can be partly provided by bulk inertia terms, implying that the X point cannot be the dominant location of dissipation. On the other hand, we know that the nongyrotropic pressure-based electric field must dominate at the stagnation point of the in-plane electron flow, and that electron distributions here feature crescents. The further fact that the current density peak is shifted off the position of the X point indicates that there may be a relation between this current density enhancement, the location of the stagnation point, and the electron nongyrotropies. In this presentation we report on further progress investigating the physics of the electron diffusion region in asymmetric reconnection with a focus on how to explain the dissipation operating under these conditions. </p>

Die Raumladungsbremsung von Elektronenlawinen

1959 ◽  
Vol 14 (11) ◽  
pp. 989-994
Author(s):  
K. J. Schmidt-Tiedemann
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Electron Avalanche ◽  
Homogeneous Electric Field ◽  
First Order ◽  
Charge Field ◽  
The Common ◽  
Negative Space ◽  
Theoretical Results ◽  
First Order Perturbation

The electric field generated by the positive and negative space charge of a single electron avalanche moving in a homogeneous electric field is calculated. Treating the interaction of the avalanche with its own space charge field as a first order perturbation, a growth formula is obtained which differs markedly from the common TOWNSEND formula. The theoretical results fit well with experimental data on avalanche statistics reported in the literature.

The structure of the impulse corona in a rod/plane gap. II. The negative corona: propagation and streamer/anode interaction

1979 ◽  
Vol 367 (1730) ◽  
pp. 321-342 ◽  
Keyword(s):  
Simple Model ◽  
Electric Field ◽  
Space Charge ◽  
Electric Fields ◽  
Electric Field Distribution ◽  
Electron Lifetime ◽  
Gas Temperature ◽  
Negative Corona ◽  
Negative Impulse ◽  
Total Electric Field

The electric fields due to negative impulse corona space charge in a 0.5 m rod/plane gap have been investigated with a rotating fluxmeter probe. Spatial development has also been studied by simultaneous photography. The results indicate that a total electric field of about 1.8 MV m-1 is required near the head of the streamer for propagation, and a simple model is proposed of the electric field distribution in the gap at various stages of development. Measurements of transfer charge, due to interaction of streamers with the plane, yield estimates of the free electron lifetime and the gas temperature in the streamer. Possible models of the charge distribution in streamers are considered, with their associated electric fields, and best agreement with the data is obtained when most of the space charge is assumed to be concentrated at the tip. Comparison is made with earlier work on positive coronas.

Properties of Space Charge Distributions and Conduction Current in XLPE and LDPE under DC High Electric Field

2016 ◽  
Vol 198 (3) ◽  
pp. 19-26 ◽  
Author(s):  
TSUYOSHI KATO ◽  
RYO ONOZAWA ◽  
HIROAKI MIYAKE ◽  
YASUHIRO TANAKA ◽  
TATSUO TAKADA
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
High Electric Field ◽  
Conduction Current ◽  
Charge Distributions

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.

Sign in / Sign up

Export Citation Format

Share Document