Corona Discharge

Numerical computation of the electric field strength and ionic space charge density in electrode systems consisting of ionizing wire and non-ionizing cylinder, connected to the same DC high-voltage supply and facing a grounded plate, is a difficult problem, which is of interest to several electrostatic processes applications. In a previous study a simple numerical method has been proposed to calculate the spatial distributions of electric field and ionic space charge in a case of a continuum and uniform corona discharge originating at the surface of the wire. The aim of the present paper is to improve the physical model of the corona discharge in this particular electrode configuration, by assuming a more realistic law of charge injection on the wire circumference. The computations were carried out for an ionizing wire of radius r ¼ 0.1 mm, located at different distances h from a metallic tubular support of radius R ¼ 13.4 mm.The initial conditions of the corona discharge took into account the non-uniformity of the charge injection around the ionizing wire electrode. The computational results were compared with those obtained under the assumption of uniform corona discharge. The comparison pointed out that neither the non-uniformity of the electric field nor that of the charge injection can be neglected. They depend on the geometry of the electrode system and affect the distribution of the electric field and of the space charge density in the inter-electrode gap.

Corona discharge Dielectric barrier discharge Glow discharge Hydrogen a b s t r a c t Dissociation of hydrogen sulfide has been studied in four different discharges: AC corona, dielectric barrier, streamer, and contracted glow discharge. All experiments were done in a single geometry, close to a plug flow reactor, with the goal of fair comparison. The performance of corona discharge and DBD was studied in the initial gas temperature range of 300e1200 K. A specific energy requirement (SER) was calculated as function of energy input for each type of discharge and compared with earlier experimental results and modeling. The results showed that discharges with high E/n and low specific energy input (corona, DBD, and streamer) perform much worse than those with low E/n (contracted glow discharge) where specific energy input was high and gas temperature was elevated. The SER for non-thermal dissociation was 12e14 eV/molec. However, in the case of the contracted glow discharge, SER decreased to 2.4 eV/molec. This SER is close to the value predicted by thermodynamic equilibrium modeling. Further reduction of SER in a plug flow reactor does not seem possible.

The purpose of this paper is to study the effect of the high-voltage power supply waveform and the presence of a dielectric barrier on the collection of submicron particles in a wire-to-cylinder electrostatic precipitator. The experiments are carried out on two reactors (with or without dielectric barrier on the surface of the cylindrical collector electrode) with the same active section and volume. The results show that the highest collection efficiency is obtained with the negative dc corona. At equivalent electric power consumption, the Dielectric Barrier Discharge (DBD) is as effective as the positive dc corona and the ac corona. The efficiency can reach 99% with both studied reactors, if the necessary power is provided.

In a sulphur hexafluoride (SF6) discharge, regions of metal fluoride develop with time on the electrode surfaces as a result of chemical reaction between the electrode material and fluorine produced in the discharge. The influence of these fluorides on discharge behavior has been examined for several electrode materials: brass, copper, stainless steel, aluminum, and nickel, in SF6 positive corona discharges at a pressure of 200 torr and in SF6 glow discharges at a few torr. For observation and photography of the low-intensity corona discharges, an image intensifier system was used. For most of the electrode materials, the surface buildup of metal fluoride causes the structure of the discharges to be modified with time, and bright spots or filaments develop at the electrodes in times of the order of minutes. For nickel electrodes, the electrode-fluorine reaction is very slow, and little change in discharge behavior is observed, even after several hours. Nickel clearly represents the best choice of electrode material for any discharge device using a fluoride medium, particularly when uniformity and stability are required over long periods of time.

A cold atmospheric pressure plasma source, called hairline plasma, for biological and medical applications has been developed. Using the physical effect of the negative dc corona discharge, a nanosecond pulsed microplasma has been created. The device produces a very thin (d~30 mum) plasma filament with a length of up to 1.5 cm. Due to this geometrical parameters this plasma is

The trial compared the use of needle and plate electrode configuration (corona discharge) with parallel plate electrode configuration for postharvest treatment of apples (Malus domestica Borkh, cv. Fuji and Golden Delicious) during storage. The effect of electric field direction on physicochemical properties of fruit was also investigated. In Fuji apple storage, physicochemical parameters varied with water core content. Treatment of apples kept between parallel plate electric field suppressed weight loss unlike in the corona discharge field. Respiration and climacteric peak were suppressed in apples kept between parallel plate electric field. In corona discharge, after 7 days more respiration was noted in the treated than the untreated samples. The 'reversed' electric field treatment (apples on cathode plate) gave higher weight loss than the corresponding 'forward' electric field treatment (apples on anode plate) in the parallel plate arrangement. In corona discharge, the multiple of evaporation rate (ratio of water loss in treated sample to that of untreated sample) was higher for the 'forward' electric field direction (negative needle polarity) than the 'reversed' electric field direction (positive needle polarity).

Partial discharge (PD) is an electrical discharge, which does not bridge the electrodes between an insulation system completely under high electric field stress. PD events may affect the performance of insulation system because in long term, it may cause the breakdown of insulation system and failure of high voltage component due to repetition of PD events. In this work, two techniques of analysing PD data have been studied; the phase resolved partial discharge (PRPD) pattern and pulse sequential analysis (PSA) techniques. These two techniques were used to distinguish three main types of PD; they are corona, void and surface discharges. PD data were obtained from the measurement in high voltage laboratory in the University of Southampton, UK. In the end of the analysis, comparison between the PRPD and PSA methods was done to evaluate the advantages and disadvantages between the two techniques.

Hybrid plasma catalyst technology has great potential for indoor air purification. However, humidity is a critical parameter in plasma catalytic processes. In this work, several catalysts were tested downstream of a DC corona discharge and the effect of humidity was investigated on both ozone and toluene removal. Next, sorption measurements onto the catalysts were performed for toluene, trichloroethylene and acetone, using an equilibrium partitioning in closed system procedure to explain the obtained results in a quantitative manner.

Sulfonated azo dyes are separated by highperformance ilquid chromatography and introduced into the atmospherk pressure ion source of a trlple quadrupole mass spectrometer uslng pneumatic nebulizers. A heated nebulizer together wlth a corona dlscharge produces ions by gas phase chemical lon-Izath. Two related nebulizers operating at room temperature and fioatlng at a high vonage make use of Ions present In the liquid phase. Collision induced dissociation of [M -HIions shows SOs'-as a fragment characteristic of sulfonated azo dyes and parent ion scans on SO3*are used for identlflcation of azo dyes In environmental samples. Selected ion monitoring and selected reaction monltorlng are used for the determination of speciflc dyes.

The wettability and porosity of plastified poly(vinylchloride) (PVC) films were enhanced by a combination of two methods, respectively, by chemical grafting of hydrophilic additives and corona discharge treatment. Modifications of the surface morphology and surface energy are proved by scanning electron microscope images and contact angle measurements. It was found a better wettability and porosity of the plastified PVC films and a functionalization of the surface.

A negligible percentage of the cost of a Power Generation Plant or Transmission network goes towards the cost of insulators, yet the cumulative O&M costs, outage costs and equipment damage costs due to poor insulator performance can be staggering. Entire transmission grids have been known to collapse due to a pollution flashover on a single insulator. Common practices to try and attain uninterrupted performance of outdoor porcelain and glass insulators include live-line Insulator washing, application of silicone grease, specially designed ‘anti-fog insulators’, contamination source reduction and increased maintenance surveillance. These methods often fail to prevent failures and are at best temporary solutions.

One of the methods adopted to eliminate pollution flashovers is the use of RTV Silicone Insulator Coatings. Widespread field experience suggests this could be one of the most promising methods to eliminate flashovers, even in the harshest environments.

This paper reviews field experiences of gen-4 RTV Silicone HV Insulator Coatings (HVICs) in very heavily polluted environments and how they have had an exceptional success rate in eliminating flashovers, even when all other methods have failed.

RTV Insulator Coatings are being recognized as perhaps the most effective methods to eliminate pollution flashovers on ceramic insulators of up to 1200kV. Power utilities, heavy industry (captive power), technical consultants and academics are increasingly researching the subject. This presentation on Gen-4 RTV Insulator Coatings was for an IEEE event at Indian Institute of Technology (IIT, Delhi) and explains various key aspects of the coating. Contact [email protected] for more information

At COVID-19 time, viruses in water become gravely dangerous to human health and life and very resistant to traditional disinfection methods. As a type of encouraging endeavor for contamination removal, plasma discharge shows good results in dealing with viruses' removal. Indeed, more efficient, cheaper, and environmentally-friendly than conventional disinfection techniques , electrical discharge technologies are confirmed as. UV emission from plasma dispositions and the impacts of irradiation on microorganisms become broadly studied. Throughout ozonation, implementing pulsed high-voltages can lead to better diffusion of ozone in water and quicker transformation of ozone into free radicals. Via direct electrical discharges, purifying water has trends to be examined on a large-scale. Both in water and above water level, the electrical discharges possess their advantages and disadvantages. Above water level, which is in the gas phase, electrical discharges need less energy for the discharge to occur; however, in water, electrical discharges need an easier setup and form the chemically active species that could immediately bombard the aqueous contaminants. One of the kinds of electrical discharges, pulsed corona discharge remains the most tried and looks to be the most encouraging for treating water. Such methods could be methodically experimented with determining the optimal circumstances for killing COVID-19 and different pathogens from water. Merging plasma discharge, electrocoagulation, and magnetic field implementation can lead to better performances. As a secure physical separation, the final step has to involve activated carbon adsorption pursued by a membrane process to retain organic matter liberated from the cellular cytoplasm throughout oxidation and disinfection methods.

In Notzeiten, bei Gefahr erwartet man, daß die Politik dazu beiträgt, die Not zu wenden, aber eben ohne eine noch größere Not zu erzeugen.
Der Staat hätte in der Coronakrise die Kreativität von Unternehmern gut gebrauchen können. Das verordnete wirtschaftliche Koma war allein schon deshalb komplett falsch.
Demokratie und Marktwirtschaft oder Bevormundung und Sozialismus: Sind wir in einer Krise alle Sozialisten?

Mein Artikel ist zuerst am 5. Mai auf der Internetseite von „Recherche D“ erschienen (https://recherche-dresden.de/not-abwenden-ohne-noch-groessere-not-zu-erzeugen/) sowie in "Recherche D" Ausgabe 10 | August 2020, S. 40-43. Und dann noch, wie hier vorliegend, weiter ergänzt worden.
Die Annahme, das Handeln der GroKo-Regierung sei vom Machterhaltungsinteresse geleitet, aus der deduktiv geschlossen wurde, stützt sich auf frühere Meldungen, Frau Merkel lasse sich regelmäßig Meinungsumfragen vorlegen und richte anscheinend daran ihr Auftreten und auch ihre Entscheidungen aus: Ihre 180-Grad-Wenden in der Atomenergiefrage nach der Fukushima-Katastrophe und in der Flüchtlingskrise waren ja auch beifallsheischend und sie will unbedingt „unschöne Bilder“ vermeiden.
Inzwischen gibt es hinreichend Fakten, die die Schlußfolgerungen bestätigen und induktiv folgern lassen: Die Reaktionen der Regierung – sowohl das anfängliche Nicht-Handeln wie die späteren restriktiven Maßnahmen – sind allein machtorientiert. Fakten liefert dazu insbesondere die Analyse des Krisenmanagements von Oberregierungsrat Stephan Kohn, stellvertretender Leiter der Abteilung KM4 im Bundesinnenministerium (PdF: https://www.tichyseinblick.de/wp-content/uploads/2020/05/Corona-Ma%C3%9Fnahmenbewertung.pdf).

An experimental parametric study is made to investigate how the electrical corona discharge characteristics are influenced by the geometrical configuration and dimensions of the reactor and the electrode polarity of the applied voltage. Furthermore, features of the corona discharge plasma formed around the stressed electrode in some different gases are recorded photographically to provide more information on the physical mechanisms of the corona discharge in the investigated gases. The obtained results have been discussed in the light of gas discharge physics and its applications.

A number of polydimethysiloxane (PDMS) bonding techniques have been reported in the literature over the last several years as the focus on multilayer PDMS microfluidic devices has increased. Oxygen plasma bonding, despite cost, additional fabrication time and inconsistent bonding results, has remained a widely used method for bonding PDMS layers. A comparative study of four rapid, inexpensive alternative PDMS-PDMS bonding

A novel corn–zein coating structure on polypropylene (PP) films was developed to examine its feasibility as an alternative water vapor and oxygen-barrier for flexible packaging industry. The barrier properties of the resulting films were evaluated as affected by coating formulation ( ...

This study has been conducted during 2016, the samples were collected from discharge of General Company for Vegetable Oil Industry before and after treatment in Baghdad city. Some parameters were measured such as: Temperature, pH, Electrical Conductivity, Dissolve Oxygen and Phosphate, all reading before treatment are very high but the readings degreased rapidly after treatment. In contrast, oxygen concentration before treatment was low and elevated after treatment so much until reaches to the optimal condition for all biological and chemical properties. In this study 37 species of algal were recorded. The dominant group by the large number of species was Bacillarariophyce (24 species) followed by Cyanophycea (6species), Chlorophayce (5 species), Euglenophyceae (1species). This study shows that species recorded in the this studyeventually will stilted in Tigris river as a result of the discharge processing of this facility, therefore, some species can be found in Tigris river basin come from General Company for Vegetable Oil Industry.

As part of a pulsed corona system for pollution control applications, a high-voltage pulse generator was developed, constructed and tested . A 1kW generator delivers a 45kV, 100ns pulse across a 120Ω load with a risetime of 15ns and a repetition rate of up to1kHz. It comprises of a single magnetic compression (MC) stage which incorporates both amorphous metal and ferrite cores for fast magnetic switching. The compressor does not contain external remagnetization circuits that are commonly used in magnetic compressors. A fast semiconductor ABB A-Z switch specified for 2.5kA, 3kV is used as the main switch. A thorough theoretical analysis of the circuit topology is presented. Experiments with a dummy load showed a fair agreement with simulations. Typical voltage and current waveforms, volt-ampere characteristics and the corona discharge appearance are presented. The results of this study are used for developing a 6kW pulse generator for an advanced industrial-grade system.

Prior to large earthquakes the Earth sends out transient signals, sometimes strong, more often subtle and fleeting. These signals may consist of local magnetic field variations, electromagnetic emissions over a wide range of frequencies, a variety of atmospheric and ionospheric phenomena. Great uncertainty exists as to the nature of the processes that could produce such signals, both inside the Earth's crust and at the surface. The absence of a comprehensive physical mechanism has led to a patchwork of explanations, which are not internally consistent. The recognition that most crustal rocks contain dormant electronic charge carriers in the form of peroxy defects, O 3 Si= OO n SiO 3 , holds the key to a deeper understanding of these pre-earthquake signals from a solid state physics perspective. When rocks are stressed, peroxy links break, releasing electronic charge carriers, h Á , known as positive holes. The positive holes are highly mobile and can flow out of the stressed subvolume. The situation is similar to that in a battery. The h Á outflow is possible when the battery circuit closes. The h Á outflow constitutes an electric current, which generates magnetic field variations and low frequency EM emissions. When the positive holes arrive at the Earth's surface, they lead to ionization of air at the ground-air interface. Under certain conditions corona discharges occur, which cause RF emission. The upward expansion of ionized air may be the reason for perturbations in the ionosphere. Recombination of h Á charge carriers at the surface leads to a spectroscopically distinct, non-thermal IR emission.

SUMMARY The present paper proposes two possible hypotheses of the body image formation of the Turin Shroud (TS) based on corona discharge (CD). An impression mechanism based on CD proves to be the most credible one after verifying that some characteristics of the TS image are not in full agreement with the hypothesis of a simple burst of light proposed

Atmospheric-pressure plasmas are used in a variety of materials processes. Traditional sources include transferred arcs, plasma torches, corona discharges, and dielectric barrier discharges. In arcs and torches, the electron and neutral temperatures exceed 3000 C and the densities of charge species range from 10 16 -10 19 cm 03 . Due to the high gas temperature, these plasmas are used primarily in metallurgy. Corona and dielectric barrier discharges produce nonequilibrium plasmas with gas temperatures between 50-400 C and densities of charged species typical of weakly ionized gases. However, since these discharges are nonuniform, their use in materials processing is limited. Recently, an atmospheric-pressure plasma jet has been developed, which exhibits many characteristics of a conventional, low-pressure glow discharge. In the jet, the gas temperature ranges from 25-200 C, charged-particle densities are 10 11 -10 12 cm 03 , and reactive species are present in high concentrations, i.e., 10-100 ppm. Since this source may be scaled to treat large areas, it could be used in applications which have been restricted to vacuum. In this paper, the physics and chemistry of the plasma jet and other atmospheric-pressure sources are reviewed.

Corona discharge Dielectric barrier discharge Glow discharge Hydrogen a b s t r a c t Dissociation of hydrogen sulfide has been studied in four different discharges: AC corona, dielectric barrier, streamer, and contracted glow discharge. All experiments were done in a single geometry, close to a plug flow reactor, with the goal of fair comparison. The performance of corona discharge and DBD was studied in the initial gas temperature range of 300e1200 K. A specific energy requirement (SER) was calculated as function of energy input for each type of discharge and compared with earlier experimental results and modeling. The results showed that discharges with high E/n and low specific energy input (corona, DBD, and streamer) perform much worse than those with low E/n (contracted glow discharge) where specific energy input was high and gas temperature was elevated. The SER for non-thermal dissociation was 12e14 eV/molec. However, in the case of the contracted glow discharge, SER decreased to 2.4 eV/molec. This SER is close to the value predicted by thermodynamic equilibrium modeling. Further reduction of SER in a plug flow reactor does not seem possible.

This study discusses the possibility of using a corona discharge at atmospheric pressure and air RF plasma at low pressure for the cotton fibre activation prior to deposition of colloidal TiO 2 nanoparticles in order to enhance antibacterial, UV protective and self-cleaning properties. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of TiO 2 nanoparticles on the surface of cotton fibres. XPS elemental mapping indicated that TiO 2 nanoparticles were more evenly distributed across the surface of untreated and corona pre-treated cotton fabrics in comparison with RF plasma pretreated fabric. Atomic absorption spectroscopy measurements revealed that the equivalent total content of TiO 2 in the cotton fabrics pre-treated by corona and RF plasma was 31% higher than in the fabric that did not undergo any treatment prior to loading of TiO 2 nanoparticles. In order to achieve maximum bacteria (Gram-negative bacteria Escherichia coli) reduction, untreated cotton fabric had to be loaded with colloidal TiO 2 nanoparticles twice, but only once following corona or RF plasma pre-treatment. Deposition of TiO 2 nanoparticles onto cotton fabrics provided maximum UV protective rating of 50?. Extraordinary photocatalytic activity of TiO 2 nanoparticles deposited onto cotton fabrics was proved by self-cleaning of blueberry juice stains and photodegradation of methylene blue in aqueous solution under UV illumination.

Ability of a dc electrical discharge to control low-velocity airflow along a flat plate is analyzed. Specifically, the electrodes are flush mounted on the insulating surface of the plate creating a tangential corona discharge at close vicinity of the wall. In this paper, visualizations of the low-velocity airflow (up to 1.4 m/s corresponding to Re = 16 000) along the flat plate are presented.

From the early 20th century Nobel Prize winning (1923) experiments with charged oil droplets, resulting in the discovery of the elementary electronic charge by Robert Millikan, to the early 21st century Nobel Prize (2002) awarded to John Fenn for his invention of electrospray ionization mass spectroscopy and its applications to proteomics, electrostatic processes have been successfully applied to many areas of industry and medicine. Generation, transport, deposition, separation, analysis, and control of charged particles involved in the four states of matter: solid, liquid, gas, and plasma are of interest in many industrial and biomedical processes. In this paper, we briefly discuss some of the applications and research needs involving charged particles in industrial and medical applications including: (1) generation and deposition of unipolarly charged dry powder without the presence of ions or excessive ozone, (2) control of tribocharging process for consistent and reliable charging, (3) thin film (< 25 m) powder coating and powder coating on insulative surfaces, (4) fluidization and dispersion of fine powders, (5) mitigation of Mars dust, (6) effect of particle charge on the lung deposition of inhaled medical aerosols, (7) nanoparticle deposition, and (8) plasma/corona discharge processes. A brief discussion on the measurements of charged particles and suggestions for research needs are also included. ᭧

The steady radial distribution of chemical species in a wire-to-cylinder ozone generator filled with pure oxygen has been computed by applying four different plasma chemistry models of increasing complexity. The most complete model considers ten species (e, 02+, 02-, 0 3 -, 0-, 02, o~('A.J, o~( ' z~) , 0 and 03) and 79 reactions, including ionization by electron impact, electron attachment and detachment, electron-ion recombination, charge transfer, etc. The chemical model is coupled with the electrical model through Poisson's equation. The spatially averaged ozone density has been computed as a function of the current intensity and compared with the experimental values obtained by W spectroscopy.

Axisymmetric finite element models have been developed for the simulation of negative discharges in air without and with the presence of dielectrics. The models are based on the hydrodynamic drift-diffusion approximation. A set of continuity equations accounting for the movement, generation and loss of charge carriers (electrons, positive and negative ions) is coupled with Poisson's equation to take into account the effect of space and surface charges on the electric field. The model of a negative corona discharge (without dielectric barriers) in a needle-plane geometry is analysed first. The results obtained show good agreement with experimental observations for various Trichel pulse characteristics. With dielectric barriers introduced into the discharge system, the surface discharge exhibits some similarities and differences to the corona case. The model studies the dynamics of volume charge generation, electric field variations and charge accumulation over the dielectric surface. The predicted surface charge density is consistent with experimental results obtained from the Pockels experiment in terms of distribution form and magnitude.

We demonstrate the ability of non-thermal plasma to promote blood coagulation and tissue sterilization in under 15 seconds of treatment. We demonstrate no gross (visible) or microscopic damage to tissue in as much as 5 minutes of plasma treatment. This procedure would be safe for patients since there are no exposed electrodes, discharge is cold, and current is low. Initial experimental results obtained using cadaver organs and donor blood support the fact that the DBD plasma can simultaneously sterilize skin and promote coagulation in bleeding tissue. This technique will decrease wound healing time and virtually eliminate wound infections with skin flora.

Abstract-Surface potential decay (SPD) measurements are considered as the most appropriate technique for the investigation of the corona charging of dielectric surfaces. The aim of the experiments reported in the present paper was to point out the peculiarities of SPD in the case of non-homogeneous dielectrics, such as the non-woven fabrics employed for heat, ventilation and air conditioning. This study reports experimental data collected on two types of polypropylene (PP) media, characterized by different fiber diameters. The experiments were performed on 60 mm x 50 mm samples of non-weaved sheets of PP (sheet thickness: 300 m; average fiber diameter: 20 m), in ambient air (temperature: 18°C to 22°C; relative humidity: 25% to 60%). The samples were charged for 10 s by exposing them to the negative corona discharge, using a triode-type electrode arrangement, energized from a DC high-voltage supply. Their surface potential was then measured with an electrostatic voltmeter. The measured data indicate that the charge of the filter is limited by the local discharges that occur inside the fibrous dielectric. . His present research interests include the electrical properties of dielectric materials, the characterization of insulating systems, as well as the numerical and experimental modeling of electrostatic separation and precipitation processes.

The goal of this paper is to introduce some recently developed finite volume schemes to enable numerical simulation of electric fieldespace charge coupled problems. The key features of this methodology are the possibility of handling problems with complex geometries and accurately capturing the charge density distribution. The total variation diminishing (TVD) scheme and the improved deferred correction (IDC) scheme are used to compute the convective and diffusive fluxes respectively. Our technique is firstly verified with the computation of hydrostatic solutions in a two coaxial cylinders configuration. The homogeneous and autonomous injection from the inner or outer electrode is considered. Comparison has been made with the analytical solution. The numerical technique is also applied to the problem of corona discharge in a blade-plane configuration. The good agreement between our numerical solution and the one obtained with a combination approach of Finite Element Method (FEM) and Method of Characteristics (MoC) is shown.

An installation containing a DC negative corona discharge reactor, a pulse corona discharge reactor and a combined electron beam and microwave induced plasma reactor is presented. SO 2 is removed up to 42% through spontaneous reaction with ammonia without electron beam or microwave irradiation at the temperature below 70 1C. For the same removal efficiency of 98% for SO 2 and 80% for NO x at separate EB irradiation of 40 kGy, the required absorbed dose is about two times smaller for simultaneous electron beam and microwave irradiation. The SO 2 removal efficiency of simultaneous DC or positive discharge and microwave discharge is higher than separate DC, pulse and MW discharge. Also, the applied voltage level at which the removal efficiency reaches the maximum value is less than for the separate application of DC or pulse discharge. The NO x removal efficiency of DC or pulse discharge suffers little change by additional use of the microwave energy.

Non-contact measurements performed with the auto-compensated electrostatic induction probe of an electrostatic voltmeter are often employed to characterize the charging state of insulating materials, such as films or non-woven media. The aim of the paper is double: (i) describe a simple method for assessing the resolution of such a probe; (ii) discuss the significance that can be attributed to the value displayed by the electrostatic voltmeter when the charge is non-uniformly distributed at the surface of the bodies examined by the probe and no constant surface potential can be defined. The measurements were performed for some simple experimental models that simulate surface potential non-uniformity of constant-charge insulating bodies. By examining the different surface potential distribution curves that were obtained for each of the situations under study, it is possible to estimate the resolution of the probe. A commercial computer program based on the superficial charge simulation method was employed for the numerical analysis of the electric field in a simplified 2-D representation of the geometric system formed by the probe, the experimental model, and the grounded plate. The potential that anneals the electric field at the surface of the probe (to simulate its principle of operation) was calculated by an iterative method. A good agreement was found between the results of the numerical simulations and the experimental data. The errors that can be made in the interpretation of the results of surface potential measurements are illustrated by the case of a non-uniformly-charged non-woven polypropylene fabric.

The transition of a negative corona discharge into a glow discharge at atmospheric pressure is investigated. The volt-ampere characteristics of a pin-to-plate discharge configuration reveal the existence of three discharge regimes: corona, glow, and spark. The discharge luminosity is indicative of the differences in the electrical field distribution in the different regimes.

A simplified model of corona discharge on overhead wire has been proposed for propagating surge computations using the finite-difference time-domain method. The radial progression of corona streamers from the wire is represented as the radial expansion of cylindrical conducting region whose conductivity is several tens of microsiemens per meter. Two wire radii are considered: 5 and 2 mm, in order to simulate two experimental configurations by Noda. The critical electric field on the surface of a 5-mm radius wire for corona initiation is set to E 0 = 1.8 or 2.9 MV/m. For a 2-mm radius wire, it is set to E 0 = 2.2 MV/m. The critical background electric field necessary for streamer propagation is set to E cp = 0.5 MV/m for positive voltage application, and E cn = 1.5 MV/m for negative voltage application. The computed waveform of radial current (including both conduction and displacement currents) agrees well with the corresponding measured waveform. Also, the computed relation between the total charge (charge residing on the wire and emanated corona charge) and applied voltage (qV curve) agrees well with the corresponding measured one, except for relatively low applied voltages. Additionally, the increase of coupling between the energized wire and another one nearby due to corona discharge is well reproduced.