Types Of Electrical Discharges Research Articles

An implicit time integration approach for simulation of corona discharges

Corona discharge is a type of electric discharge that occurs when a small conductor carries a voltage strong enough to ionize the surrounding air. The resultant ions are drifted by the electric field and transfer their momentum to neutral particles via elastic collisions, creating a flow effect known as ionic wind that has promising application in flow control. Over the last two decades, a large amount of numerical works have been realized to study this effect. However, simulation of corona discharges with explicit time integration usually requires an excessive amount of time to finish, ranging from days to months in two dimensions, depending on mesh size and physical end time. The reason lies in the profound disparity between physical time scales in a discharge: for example, electron density evolves on the order of picoseconds while the time scale of airflow dynamics is on the order of milliseconds. The objective of this work is therefore to reduce the CPU time of corona discharges. We propose an implicit time strategy in the scope of the Local Field Approximation plasma model. We investigate some algorithms, namely the Lie operator splitting, the Douglas-Rachford method and a nonlinear variant of the Gauss-Seidel algorithm, to solve the system of discrete equations, which are adapted to take into consideration a constraint on the electron density. This constraint is introduced to compensate for sources of electrons from physical processes that are not accounted for in the plasma model; it is expressed by a minimum density, or floor density, imposed on the electrons. Therefore, simplified plasma models can be employed for discharge simulations, for instance a four-specie, four-reaction model is used in this article. The investigation is done on a one-dimensional wire-to-wire corona discharge. After having identified the most suitable algorithm, we carry on to two-dimensional simulations and compare the numerical results with experiment data for different levels of floor density.

Electric discharge detection and localization using a distributed optical fiber vibration sensor

Partial discharges are a type of electric discharge that cause localized breakdowns in a small portion of an insulating material without forming a complete rupture. In high power electric machines as well as in transmission lines, partial discharges are caused by the degradation and/or the presence of defects in the insulation. The damage caused by the partial discharges can be either thermal, mechanical or chemical and can cause progressive deterioration of the insulation and lead to catastrophic failure causing serious safety risks. In this work a Distributed Optical Fiber Sensor System (DOFS) for vibration measurements based on Sagnac interferometry is proposed. This system uses acoustic wave emission phenomena to detect and locate electric discharges in electric machines and insulated electrical cables. Two experiments were carried out evaluating the performance of the system. Electric discharges were measured firstly over a conductive board with an attached 10 m long flat-coiled optical fiber sensor and secondly, over a 1.20 m long electrical cable with an optical fiber sensor longitudinally attached to it. Results demonstrate that due to the high sensitivity of the system it is possible to detect partial discharges in both proposed experiments. This effect is observed even with a theoretical fiber optical sensing spatial resolution of approximately 50 m.

Supply Systems of Non-Thermal Plasma Reactors. Construction Review with Examples of Applications

A review of the supply systems of non-thermal plasma reactors (NTPR) with dielectric barrier discharge (DBD), atmospheric pressure plasma jets (APPJ) and gliding arc discharge (GAD) was performed. This choice is due to the following reasons: these types of electrical discharges produce non-thermal plasma at atmospheric pressure, the reactor design is well developed and relatively simple, the potential area of application is large, especially in environmental protection processes and biotechnologies currently under development, theses reactors can be powered from similar sources using non-linear transformer magnetic circuits and power electronics systems, and finally, these plasma reactors and their power supply systems, as well as their applications are the subject of research conducted by the author of the review and her team from the Department of Electrical Engineering and Electrotechnology of the Lublin University of Technology, Poland.

Феноменология электрических разрядов, возникающих между отрицательно заряженным облаком водного аэрозоля и землёй

Studies of electrical discharges generated in the electric field of charged aerosol clouds make it possible to obtain better understanding of how lightning occurs in thunderclouds. For this purpose, an experimental setup was developed, which allows charged aerosol clouds of negative polarity to be produced. A charged aerosol cloud creates electric field strength sufficient to generate electrical discharges between this cloud and the earth. The experimental setup for obtaining an artificially produced charged aerosol cloud is briefly described. The experimental setup is equipped with a set of measuring instruments for recording the electrical and optical signals of discharges and for photographing the discharges themselves. A database has been accumulated in the course of experiments, which includes the waveforms of discharge current pulses recorded using digital oscilloscopes, the waveforms of signals from optical sensors recording the development of discharges in space and time, and the snapshots of discharges. By using the accumulated information it is possible to classify discharges that occur between artificially produced charged aerosol clouds of negative polarity and the earth by type and parameters. An analysis of the experimental data has shown that both upward and downward discharges can occur between a charged aerosol cloud and the earth, which is typical for natural lightning phenomena. The snapshots of the most characteristic types of electric discharges observed in experiments and simple models explaining the development of these discharges are studied.

First-principles study of Pd-MoSe2 as sensing material for characteristic SF6 decomposition components

SF6 decomposition component detection is an effective way to diagnose the severity and type of electric discharge. In this study, MoSe2 based material has been chosen as the gas sensing material for the detection of SOF2 and SO2F2, the two characteristic decomposition components of SF6. Based on density functional theory calculations, the adsorption properties of both SOF2 and SO2F2 on intrinsic and Pd doped MoSe2 are studied by analyzing the adsorption structure, charge transfer, density of states, and molecular orbit. The results show that SOF2 and SO2F2 adsorb on intrinsic MoSe2 by physisorption, resulting in weak gas sensitivity. After Pd doping on MoSe2, it dramatically enhances the gas sensitivity of MoSe2 to SOF2 and SO2F2; both the gases interact with Pd-MoSe2 by chemisorption. In addition, SOF2 and SO2F2 show an increase in conductivity during the adsorption process to different extents. The calculation results show that Pd-MoSe2 can be a potential gas sensing material for SOF2 and SO2F2 detection in SF6-insulated equipment.

The breakthrough phase of lightning attachment process: From collision of opposite-polarity streamers to hot-channel connection

Recent progress in studying the breakthrough phase (BTP) of the attachment process in lightning and long sparks is reviewed. The main focus is on the new insights gained from recent observations for 3 types of electric discharges: natural lightning (Nag et al., 2012; Tran and Rakov, 2017a,c), rocket-and-wire triggered lightning (Howard et al., 2010; Hill et al., 2016), and long sparks (Kostinskiy et al., 2016). The BTP (also known as the final jump) starts when the poorly-conducting streamer zones, developing ahead of the hot channels of negative downward leader (DL) and positive upward connecting leader (UCL), come in contact and a common streamer zone (CSZ) is formed. The beginning of BTP (establishment of CSZ) is usually marked by an abrupt current rise, a burst of dE/dt pulses (referred to as leader burst or LB), and hard X-ray emission. During the BTP, hot channels of both DL and UCL extend toward each other inside the CSZ, resulting in its shrinking, until the high-impedance CSZ is eliminated and low-impedance connection of DL to the grounded object is established. The process of bridging of CSZ by hot leader channels is accompanied by the formation of slow front (SF) in the channel current and in electric and magnetic field waveforms at both close and far distances from the channel. Attempted or relatively weak hot-channel connections producing current surges and associated field pulses superimposed on the SF (SF pulses) can occur. The SF lasts some microseconds and ends at the onset of the submicrosecond-scale fast transition (FT), which signifies the end of BTP. During the BTP, the current rises from the UCL level of the order of tens to hundreds of amperes to about 50% of the overall (SF + FT) current peak, which is of the order of tens of kiloamperes (for negative first strokes). This two orders of magnitude current rise during the BTP occurs before the collision of hot leader channels inside the CSZ; that is, before the onset of return stroke proper.

Study of the airflow induced by a sliding discharge plasma actuator

Sliding discharge, as a new type of electrical discharge, is being gradually applied in plasma active flow control in recent years. In this work, the particle image velocimetry (PIV) experiments were conducted to investigate the airflow characteristics induced by the sliding discharge plasma actuator at varied voltage signals. The results show that the integral thrust produced by the negative alternating current (AC) power is stronger than normal AC power under the same voltage magnitude. The induced airflow direction changes along with the changing of two power voltage signals. Furthermore, the angle of the induced airflow is mainly linear with the loading voltage.

On the possibility of making natural ball lightning using a new pulse discharge type in the laboratory

A new type of electrical discharge was discovered in Gatchina, which produces long-lived luminous formations with the same unique physical properties as natural ball lightning. This paper reviews the research work on the Gatchina discharge that has been done by a number of independent groups and which has provided important insights into the nature of both the discharge and ball lightning formation processes. However, the luminous formations that appeared in the experiments by these groups have a shorter lifetime than objects created by the authors of the proposed method and fail to exhibit some of the specific properties of ball lightning. In this paper, the basic parameters and operation regimes of a facility for creating such formations are discussed; their optimization will eliminate these drawbacks. The review discusses the properties of both the discharge and the luminous objects formed in it, which were observed by the present authors and which other groups failed to reproduce. A model of natural ball lightning is proposed, in the framework of which the peculiar properties of the Gatchina discharge and of the long-lived luminous formations observed in it are explained. The experimental facility developed exhibits a number of features that allow the near-100%-effective production of long-lived luminous formations, thus enabling their physical characteristics to be studied, in principle, on a systematic basis.

Clinical, brain imaging, and electroencephalogram evaluation of cases of cerebral palsy with epilepsy

Background Cerebral palsy (CP) is a chronic disorder of movement and posture. It is the result of a nonprogressive damage of immature nervous system caused by several factors that have occurred in prenatal, perinatal, or postnatal periods. Epilepsy is one of the most common problems among patients with CP. Objectives The aim of the study was to evaluate patients with epileptic CP by clinical findings, electroencephalogram (EEG), as well as cranial MRI findings. Patients and methods This cross-sectional study was conducted on 70 patients, seen at pediatric neurology clinics at Al-Azhar University Hospitals. All patients were subjected to detailed medical history, detailed general and neurological examination, EEG, and MRI brain. Result Spastic quadriplegia was the most common type, seen in 29 (41.4%) cases. Generalized tonic–clonic seizure was the most common type of convulsion in our cases (42.9%). EEG abnormalities were commonly seen in CP with epilepsy (78.6%). The most common MRI scan abnormalities in epileptic children with CP were brain atrophy. Conclusion Spastic quadriplegia is the most common type of CP associated with seizures. EEG is a useful tool in detecting types of electrical discharges. MRI is the most useful tool in detecting the etiology of CP.

Dynamic generation of supercritical water fluid in a strong electrical discharge in a liquid

A new impetus for the development of electro physics is associated with using different types of electrical discharges in biology and medicine. These applications are based on their energetic and non-toxic factors affecting the medium on a cellular level. For the study of such processes, a mathematical model of a high-current low-temperature Z-discharge in a liquid, forming by the electrical explosion of a thin-walled metal shell, connected to a pulsed high-voltage generator, has been developed. High efficiency energy conversion, introduced into the plasma discharge to the energy of fluid motion, provides various bio chemical applications of such physical processes. The investigation is conducted through numerical solution of one-dimensional single-temperature non-stationary equations of radiation magneto hydrodynamics, one way describing the evolution of hydrodynamic, thermal and electrical characteristics of the medium throughout the area under consideration. The electrical approximation based on the assumption that the electric field in the discharge has a uniform distribution. The results are presented as a function of the electric current and the plasma channel length of time, as well as the temperature and pressure distributions at different time points along the radius of the cylindrical region in which the explosion occurs.

Variations in cosmic rays during thunderstorms and new geophysical effects

Processes that occur during thunderstorms accompanied by anomalous disturbances in cosmic rays are comprehensively investigated using the Carpet air shower array at the Baksan Neutrino Observatory. The data collected so far indicate the discovery of a new type of electric discharge: runaway electron break-down in the near-threshold regime. A glow in the stratosphere corresponding to this discharge is detected, as is stabilization of geomagnetic micro-pulsations. Both are demonstrated using one event as an example.

Influence of the type of electric discharge on the properties of the produced aluminium nanoparticles

The effect of the method of aluminum nanopowder production on the aluminum products with water reaction is described. It has been established that the interaction of aluminum nanopowder prepared by the electric wire explosion, the phase composition of the reaction products mainly consists of boehmite (AlOOH) and has a fibrous structure. Therefore, that boehmite (AlOOH) can be used for modification of polymer membranes. The modified membranes can be used as water treatment from the impurity of formed true solutions according to adsorptive mechanism, and from colloidal nanometer and micron particles according to the mechanism of mechanical separation of particles depending on sizes.

Electrode patterns in arc discharge simulations: effect of anode cooling

Self-organized electrode patterns are often observed experimentally in diverse types of electrical discharges, including atmospheric-pressure electric arcs, but rarely captured in general-purpose computational plasma dynamics simulations. Time-dependent three-dimensional thermodynamic non-equilibrium (two-temperature) simulations reveal the spontaneous formation of self-organized anode attachment spot patterns in the free-burning arc, a canonical direct-current (dc) discharge with an axisymmetric electrode configuration and the absence of external forcing. The simulations are based on a monolithic fluid-electromagnetic plasma flow model numerically implemented within a second-order-accurate in space and time variational multiscale finite element framework. Simulation results show the gradual emergence of spot patterns with increasing levels of anode cooling: from a single diffuse spot for low cooling levels to the eventual coverage of the anode region by small spots for intense cooling. The characteristics of the patterns, such as the number, size and location of the spots, markedly depend on the imposed total current. Furthermore, the patterns transition from steady to dynamic with decreasing total current for high cooling levels. The pattern dynamics show the formation of new spots by the splitting of old ones occurring in the center of the plasma, as well as the movement and eventual extinction of spots at the plasma boundaries. The different types of anode patterns (from diffuse to self-organized spots) have a significant effect on the total voltage drop across the plasma column, but a minor effect on other plasma characteristics away from the anode region. The results indicate that thermal instability together with equilibration between heavy-species and electron energy have a dominant role in the formation of anode patterns in arc discharges.

Development and Testing of a Self-Triggered Spark Reactor for Plasma Driven Dry Reforming of Methane

A versatile reactor was developed for plasma induced dry reforming of methane at atmospheric pressure and room temperature. Among different types of electrical discharges tested, low-power self-triggered pulsed spark discharges give the best results in terms of CH4 and CO2 conversion, H2 and CO yield and selectivity, and energy efficiency. Moreover, undesired carbon deposits are not formed, certainly due to the low temperature but also to the short but strong current pulses between the electrodes, the surfaces of which are kept ‘‘clean’’ by the discharge itself. Optical emission spectroscopy was also used to investigate the plasma emitting species and to determine the average electron density.

Hypergravity effects on glide arc plasma

The behaviour of a special type of electric discharge – the gliding arc plasma – has been investigated in hypergravity (1g–18g) using the Large Diameter Centrifuge (LDC) at ESA/ESTEC. The discharge voltage and current together with the videosignal from a fast camera have been recorded during the experiment. The gliding of the arc is governed by hot gas buoyancy and by consequence, gravity. Increasing the centrifugal acceleration makes the glide arc movement substantially faster. Whereas at 1g the discharge was stationary, at 6g it glided with 7 Hz frequency and at 18g the gliding frequency was 11 Hz. We describe a simple model for the glide arc movement assuming low gas flow velocities, which is compared to our experimental results.

Comparison of flows induced by a dielectric barrier discharge and a sliding discharge

Two types of electric discharges to be used for the purpose of air flow control are compared. The parameters measured in experiments are the electric characteristics of the discharges and the velocity of flows generated by them. The ionic wind velocity in the sliding discharge is demonstrated to be smaller than in the dielectric barrier discharge. The volume forces acting from the discharge on air and the efficiency of the electro-gas-dynamic action are estimated. The presence of an additional electrode in the case of the sliding discharge is found to affect the distribution of the spatial charge and change the forces, leaving the electric characteristics unchanged.

Low‐frequency radio emissions from high‐altitude sprite discharge

When lightning strikes from a towering cumulonimbus cloud down to the ground, the electrical discharge can perturb the atmosphere's electric field, potentially triggering a second event—sprite discharge. This more elusive type of electrical discharge, which produces lightning that is red in color, initiates from high altitudes, with streamers propagating down toward the top of the cumulonimbus cloud. Coincident with the dramatic displays, researchers have previously identified low‐frequency radio emissions, which they suggest may be produced in association with the sprite discharge. Investigating this hypothesis, Qin et al. used a two‐dimensional plasma model to calculate the radio emissions that should be produced by a single sprite streamer.

Plasma Sheet Actuator Driven by Repetitive Nanosecond Pulses with a Negative DC Component

A type of electrical discharge called sliding discharge was developed to generate plasma aerodynamic actuation for flow control. A three-electrode plasma sheet actuator driven by repetitive nanosecond pulses with a negative DC component was used to generate sliding discharge, which can be called nanosecond-pulse sliding discharge. The phenomenology and behaviour of the plasma sheet actuator were investigated experimentally. Discharge morphology shows that the formation of nanosecond-pulse sliding discharge is dependent on the peak value of the repetitive nanosecond pulses and negative DC component applied on the plasma sheet actuator. Compared to dielectric barrier discharge (DBD), the extension of plasma in nanosecond-pulse sliding discharge is quasi-diffusive, stable, longer and more intensive. Test results of particle image velocimetry demonstrate that the negative DC component applied to a third electrode could significantly modify the topology of the flow induced by nanosecond-pulse DBD. Body force induced by the nanosecond-pulse sliding discharge can be approximately in the order of mN. Both the maximum velocity and the body force induced by sliding discharge increase significantly as compared to single DBD. Therefore, nanosecond-pulse sliding discharge is a preferable plasma aerodynamic actuation generation mode, which is very promising in the field of aerodynamics.

P01-81 - Addiction and pain

Pain is an unpleasant sensory and emotional experience associated with existing or potential tissue damage or described in terms of such damage.ObjectiveTo define the nature and severity of substance abuse in patients attending detox cure and the importance of pain during the weaning.Materials and methodsThis is a cross-sectional study done in March 2010 over 30 patients hospitalized in the “center of help and listening to Tina-Sfax”.Through a questionnaire, we collected the biographical data, the drugs used and ways of administration, the association of toxic and the characteristics of pain: type, location, extension.We spent the TDEA: test of alcohol dependency, the DAST: screening for drug abuse and the scale of overall pain intensity.ResultsThe mean age of patients was 24.5 years, 86.7% of our sample were men. 47% of our patients consulted by their own and 47% at the request of one third. 76.7% of patients consuming the Subutex. Poly drug was present in 50%. The intravenous way was present in 76.7% cases.46.7% of our patients had twice-daily dosing, 33.6% consumed a daily basis and 100% were addicted.The pain was constant among 63.3% of patients, it was in kind of burning and tearing in 60% of patients. She was paroxysmal and in type of electrical discharge in 63.3% of cases.ConclusionThe cure of detox can cause various types of pain, which can lead to relapse or failure of the process of weaning.

The "cometary" discharge, a possible new type of DC electric discharge in air at atmospheric pressure, and its bactericidal properties

A new type of electric discharge was observed during studies of a DC discharge of the point-to-point type in air at atmospheric pressure. Some of its properties were studied with respect to its bactericidal properties.