Streamer Corona Research Articles

Upward propagation of gigantic jets revealed by 3D radio and optical mapping.

Occasionally, lightning will exit the top of a thunderstorm and connect to the lower edge of space, forming a gigantic jet. Here, we report on observations of a negative gigantic jet that transferred an extraordinary amount of charge between the troposphere and ionosphere (∼300 C). It occurred in unusual circumstances, emerging from an area of weak convection. As the discharge ascended from the cloud top, tens of very high frequency (VHF) radio sources were detected from 22 to 45 km altitude, while simultaneous optical emissions (777.4 nm OI emitted from lightning leaders) remained near cloud top (15 to 20 km altitude). This implies that the high-altitude VHF sources were produced by streamers and the streamer discharge activity can extend all the way from near cloud top to the ionosphere. The simultaneous three-dimensional radio and optical data indicate that VHF lightning networks detect emissions from streamer corona rather than the leader channel, which has broad implications to lightning physics beyond that of gigantic jets.

DC-driven positive streamer coronas in airflow

An experimental study of the effect of airflow on positive self-pulsating streamer coronas in a needle-to-plate geometry is presented. The experiments are performed in an open return wind tunnel with winds up to 30 m s−1 orthogonal to the needle. The experimental data is presented in terms of statistical properties of the discharge, inferred from high resolution, large sample-size current waveforms. The key properties of the current pulsations, namely inter-pulse period, peak current, deposited energy, and pulse width are analyzed as a function of wind speed and applied DC voltage. All parameters increase in dispersion with wind speed. The mean of the inter-pulse period decreases with wind speed and the mean pulsation frequency increases. The peak currents and energies per pulsation have a general tendency to decrease in magnitude but also higher-current, higher-energy, streamer bursts are observed. At low wind speeds, streamers preferentially propagate in the downwind direction but, as the wind speed is increased, more streamers can propagate upwind. The measurements are interpreted using an analytical model of charge transport.

Positive corona streamer interaction with metalized dielectric: Possible mechanism of cathode destruction

This paper examines the effect of pulsed positive point-to-plane corona discharge in millimeter air gaps on the surface of a metalized dielectric. A footprint method was applied to reveal the streamer–surface interaction with Al and Zn thin films (20–50 nm) as a sensitive indicator. A thin metal film-dielectric substrate system was destructed at relatively low typical average currents of 20–50 μA during exposure times of 2–200 s. Destruction occurred in local zones with a size of several μm2 per one discharge pulse, which is substantially lower than the conventional streamer size of several tens of micrometers. An offered model of electro-thermal heating of the cathode layer shows that the dielectric surface temperature can achieve 1000 K and more during the single current pulse of submicrosecond duration. The indicated mechanism is possibly responsible for the effects of the discharge plasma interaction with low heat conductivity cathodes, including biological objects. Intensive heating of the cathode layer should be considered when modeling the streamer–cathode interaction.

Responses of Rice Seed Quality to Large-Scale Atmospheric Nonthermal Plasmas

Atmospheric nonthermal plasma (ANTP) is used for various biological applications including seed quality improvements in crop production. However, the underlying mechanisms of plasma-induced seed action are not fully explained and operating large-scale ANTP on seeds is highly challenging. Two large-scale ANTPs, streamer corona plasma (SCP) and dielectric barrier discharge (DBD) plasma, were used to enhance rice seed vigor through surface modification and functionalization. The SCP and DBD plasma were conducted under the same power source and applied to rice seeds to modify their surface from being highly hydrophobic to being highly hydrophilic, as defined by the apparent contact angle measurement. The results show that SCP requires less treatment time (~ 2 min) for surface activation than the DBD plasma process (~ 10 min). Both plasma-treated seeds showed higher seed vigor than non-treated seeds. For 50% of the viable seeds to emerge, the SCP-treated seeds took on average about 62 h., while the untreated rice seeds took around 72 h. The germination percentage of all conditions is ~ 92% which is a typical proportion of good seed quality. The microstructure of the rice seed surface suggests that the bombardment of highly energetic ions and the reaction of reactive oxygen and nitrogen species on the seed surface cause morphological changes via surface etching and functionalization without any adverse effects on seed nutrition.Graphical abstract

Influence of trace SF 6 on streamer corona development in SF 6 /N 2 mixtures under positive DC voltages

Influence of trace SF ₆ on streamer corona development in SF ₆ /N ₂ mixtures under positive DC voltages

Radiation Phenomenon Due to Streamers of Sprites

An upper atmospheric phenomenon i.e., sprites can be thought to be mainly caused by the propagation of positive corona streamers. This research presents the formulation for the calculation of radiation power received from the propagating corona streamers responsible for the origination of the sprites. The produced magnetic field variation using the calculated electromagnetic radiation power is found to be similar with the previous observation-based research work.

Breakdown Characteristics of Long Air Gap at Different Frequency Based on Series Resonance

In today’s rapid economic development, with the development of science and technology, higher requirements have been put forward in the economic operation of the system. This requires various departments to make more reasonable use of existing energy and equipment, and to ensure quality. Meet all aspects of supply with more energy-saving and more economical operation methods. Therefore, more and more attention has been paid to the research on the method of predicting the breakdown voltage of the air gap. Although domestic and foreign scholars have used power frequency test transformers to carry out a large number of long air gap experimental researches, the research on the breakdown voltage of long air gaps based on the principle of vector machines is still blank. In this paper, a vector machine test device is used to study the breakdown discharge characteristics of a long air gap at two frequencies of 229Hz and 68Hz. Comparing the test phenomena at different frequencies, it is found that the initial discharge voltage of the streamer corona is lower when the frequency is 229Hz, and the discharge phenomenon before breakdown is more intense, and the quality factor will be significantly reduced due to the violent discharge. At the same time, under the same test conditions, the breakdown voltage at 229Hz is lower than that at 68Hz, and as the air gap increases, the difference between the two is greater. The experimental results show that the breakdown voltage of the long air gap based on the vector machine is different when the frequency is different, and the safety distance of the field withstand voltage test should be evaluated according to the experimental data under the vector machine condition to ensure the safety of the test.

General processes responsible for the space leader birth in streamer coronas of negative leaders

Local section of one streamer in the streamer coronas ahead of negative leaders of long laboratory sparks can develop into ‘space leaders’, called so because of their high conductivity and initially being unconnected to the main negative leader. Available data of experimental research do not allow reliably unveiling a mechanism causal to the space leader birth. We, here, discuss a hypothetical but general mechanism based, mostly, on thermodynamics. The plasma-chemistry processes in one of the streamers of the negative leader corona and Joule heating of the gas within the streamer channel are casual to a birth of a conducting area in this streamer at the strength of the ambient electric field less than the selfbreakdown magnitude of 30 kV cm−1. Two conclusions follow from the analysis. First, sufficiently high ambient field strength E 0 is required to heat the gas to a temperature sufficiently high for a birth of the conducting area during the observed time t obs. Second, the current of one streamer does provide sufficient heating; for this, the being heated area is to be fed by a multitude of the streamer branches. We limit ourselves to considering processes responsible for a formation of hot conducting areas in the negative corona. We assume that the birth of the heated area in the streamer, start new streamers from its ends and further heating of this area occurs in some local domain where the field strength exceeds the mean magnitude 11 kV cm−1 in the leader corona. We, proceeding from the experimentally observed time t obs of 1 show that the minimal magnitude of the E 0 of 20 kV cm−1 in the being heated area is required to ensure the gas temperature of 2000 K fitting the t obs. To illustrate our conclusions, we, using simplified models, carry out simulations treating selfconsistently the evolution of the electric field and the associated plasma chemistry.

Influence of Silicone Rubber Coating on the Characteristics of Surface Streamer Discharge.

A pollution flashover along an insulation surface—a catastrophic accident in electrical power system—threatens the safe and reliable operation of a power grid. Silicone rubber coatings are applied to the surfaces of other insulation materials in order to improve the pollution flashover voltage of the insulation structure. It is generally believed that the hydrophobicity of the silicone rubber coating is key to blocking the physical process of pollution flashover, which prevents the formation of continuously wet pollution areas. However, it is unclear whether silicone rubber coating can suppress the generation of pre-discharges such as corona discharge and streamer discharge. In this research, the influence of silicone rubber coating on the characteristics of surface streamer discharge was researched in-depth. The streamer ‘stability’ propagation fields of the polymer are lower than that of the polymer with silicone rubber coating. The velocities of the streamer propagation along the polymer are higher than those along the polymer with silicone rubber coating. This indicates that the surface properties of the polymer with the silicone rubber coating are less favorable for streamer propagation than those of the polymer.

A Novel Dielectric Barrier Discharge (DBD) Reactor with Streamer and Glow Corona Discharge for Improved Ozone Generation at Atmospheric Pressure.

Discharge mode is an important parameter for ozone synthesis by dielectric barrier discharge (DBD). Currently, it is still challenging to stably generate glow discharge with oxygen at atmospheric pressure. In this paper, a DBD reactor with a layer of silver placed between the electrode and the dielectric layer (SL-DBD) was developed. Experimental results show that both streamer and glow corona discharge were stably generated under sinusoidal excitation with a 0.5 mm discharge gap in a parallel-plate DBD, due to the increased electric field strength in the discharge gap by the silver layer. It was also found that, in the SL-DBD reactor, glow corona discharge enhances the discharge strength by 50 times. The spectral peak of O at 777 nm in SL-DBD is increased to 28,800, compared with 18,389 in a reactor with a streamer only. The SL-DBD reactor produces ozone with a concentration of as high as 150 g/m3 and shows good stability in an 8 h durability test.

Physical Simulation of the Spectrum of Possible Electromagnetic Effects of Upward Streamer Discharges on Model Elements of Transmission Line Monitoring Systems Using Artificial Thunderstorm Cell

The results of a physical simulation using negatively charged artificial thunderstorm cells to test the spectrum of possible electromagnetic effects of upward streamer discharges on the model elements of transmission line monitoring systems (sensor or antennas) are presented. Rod and elongated model elements with different electric field amplification coefficients are investigated. A generalization is made about the parameters of upward streamer current impulse and its electromagnetic effect on both kinds of model elements. A wavelet analysis of the upward streamer corona current impulse and of the signal simultaneously induced in the neighboring model element is conducted. A generalization of the spectral characteristics of the upward streamer current and of the signals induced by the electromagnetic radiation of the nearby impulse streamer corona on model elements is made. The reasons for super-high and ultra-high frequency ranges in the wavelet spectrum of the induced electromagnetic effect are discussed. The characteristic spectral ranges of the possible electromagnetic effect of upward streamer flash on the elements of transmission line monitoring systems are considered.

Использование искусственной грозовой ячейки для исследования влияния незавершенных восходящих разрядов на функционирование сосредоточенных модельных элементов систем мониторинга воздушных линий электропередачи

The results of a study using an artificial thunderstorm cell of the possible influence of incomplete ascending discharges from concentrated model elements of overhead line monitoring systems on their functioning in the electric field of a thundercloud and/or lightning are presented. It is shown that ascending incomplete discharges (streamers and/or leaders) are formed from the model elements of the overhead line monitoring system (sensors, receiving and transmitting devices of a concentrated type), which can affect the functioning of such devices, including due to the fact that frequencies close to the operating frequencies of the elements of the overhead line monitoring system are present in the spectrum of their currents. It is established that the spectral characteristics of incomplete streamer and leader discharges formed from model elements of sensors and of receiving and transmitting devices of the monitoring system under the influence of an artificial lightning cell include frequency ranges close to the frequency ranges of analog-to-digital converters of sensors and data transmission devices over a high-frequency channel of concentrated monitoring systems. The essential role of the streamer corona on the formation of the ultrahigh-frequency component of the current pulse of incomplete discharges is revealed. The obtained results can help to ensure lightning protection of monitoring systems in a real thunderstorm situation.

Selective Apoptotic Effect of Plasma Activated Liquids on Human Cancer Cell Lines.

Plasma medicine is a new field focusing on biomedical and clinical applications of cold gas plasmas, including their anticancer effects. Cold plasmas can be applied directly or indirectly as plasma-activated liquids (PAL). The effects of plasma-activated cell growth medium (PAM) and plasma-activated phosphate buffered saline (PAPBS) were tested, using a plasma pen generating streamer corona discharge in ambient air, on different cancer cell lines (melanoma A375, glioblastoma LN229 and pancreatic cancer MiaPaCa-2) and normal cells (human dermal fibroblasts HDFa). The viability reduction and apoptosis induction were detected in all cancer cells after incubation in PAL. In melanoma cells we focused on detailed insights to the apoptotic pathways. The anticancer effects depend on the plasma treatment time or PAL concentration. The first 30 min of incubation in PAL were enough to start processes leading to cell death. In fibroblasts, no apoptosis induction was observed, and only PAPBS, activated for a longer time, slightly decreased their viability. Effects of PAM and PAPBS on cancer cells showed selectivity compared to normal fibroblasts, depending on correctly chosen activation time and PAL concentration, which is very promising for potential clinical applications. This selectivity effect of PAL is conceivably induced by plasma-generated hydrogen peroxide.

On a possible mechanism of space stem formation at the negative corona streamer burst periphery

It's a common knowledge for spark discharge researches that negative leaders in air always propagate in a step-wise manner. A new step forms when a space leader attaches to the primary negative one. Space leaders originate from small fusiform plasma formations which are called space stems. For now, there is no any established idea about how space stems form in conditions when the background electric field inside the negative corona volume is about three times less than the dielectric strength of air. In this study, we propose a new mechanism of space stem precursors formation which is based on the joint action of ionization and electron drifting processes occurring at the negative corona streamer burst boundary in the presence of strongly inhomogeneous stochastic electric field. It is supposed that electric field fluctuations are formed by chaotically positioned clusters of negative charge which can be considered as basic elements of spatio-temporal noise and are transported into the negative corona volume by negative streamer heads. The last are emanated from the newly-formed leader tip during the development of the negative corona streamer burst finishing the step-formation process. The model is applied to specify conditions under which space stem precursor genesis is possible and to analyze the peculiarities of proposed mechanism at different altitudes above sea level.

Degradation of aniline in water with gaseous streamer corona plasma.

This paper demonstrated the effects and influencing factors in degrading aniline by gaseous streamer corona plasma along water surface under different discharging gas atmospheres. For aniline with an initial concentration of 100 mg l−1, the degradation was fastest when the reactor was not ventilated, and the degradation rate is 98.5% under 7.5 min treatment. While the degradation was slowest when Ar was ventilated, the degradation rate is 98.6% after treatment for 60 min. Some active particles were detected using a multi-channel fibre-optic spectrometer during the discharge, such as Ar, OH, N2, and N. In particular, NO was detected during air discharge. The NO and could produce ; then generated nitric acid would affect the pH value of the solution. The intermediate product by N2 discharge is nitrophenol, and nitrophenol would be converted to p-benzoquinone. The O2 discharge could produce an intermediate product of aminophenol. The intermediate products in Ar discharge were in small amounts and the final mineralization effect was the best.

Heating of a Local Region of a Branching Streamer as a Starting Point of a Space Leader and a Negative-Leader Step

Localized plasma formations called space leaders are observed in streamer coronas of negative leaders of long laboratory sparks. The main leader completes a step when the space leader comes into contact with the head of the main leader. In the present work, we discuss the creation mechanism of local plasma formations (henceforth, generally, referred to as the hot spots) that are able to initiate a space leader. It is assumed that spontaneous increase in the conductivity in a local region of one of the streamers of the main leader corona initiates two secondary coronas from the ends of this region. The corona current warms up the region, leading to formation of the hot spot, provided that the magnitude of the field in the heated region is sufficiently high. Finally, hot spots grow into the space leader with further increase in the temperature and conductivity. The necessary condition for achieving the temperature of ≈2000 K in the hot spot within the observation time of tobs ≤ 1 µs is the magnitude of the ambient electric field strength E0 = 20 kV cm–1 that is almost twice higher than the average magnitude of the electric field strength of ≈11 kV cm–1 in a negative corona.

Technology of partial discharge detection by means analysis of impulse interaction

In this paper the approach based on impulse analysis for partial discharge (PD) control and identification for high voltage insulation are summarized and the experimental research of impulses of different nature for detection some typical PD defects are discussed. Some physical effects at different voltage levels are shown and a method for the representation and characterization of the PD is introduced. Special test cells with different types of defects such as a streamer corona and pore inside oil-paper insulation of condenser type are used for the investigations. The experimental procedure for PD identification by means of impulse form transformation is shown and discussed. Experimental equipment and measurements are described. It is shown that using of impulse of nanosecond duration and commutative impulse allows the characterization and controlling PD in high voltage insulation.

On the Potential Impacts of Extreme Low Temperature on Threshold Inception Characteristics of Negative Corona Discharge

The potential impacts of extremely low temperature on threshold inception characteristics of negative corona discharge are straightly estimated through the numerical algorithm and the extremely low temperature experiments. First, the inception criterion models of glow and streamer corona are solved for assessing the salient characteristics of corona inception at varying temperatures. The feasibility of the inception models applied to different temperature environments has been verified with our measurements and literature experimental data. Through introducing temperature into transport properties, the primary avalanche propagation, ionization boundary, and electron distribution are simulated at two inception modes. Computational results show that the microscopic parameter of negative corona inception has a pronounced relationship with temperature. The inception voltage of the wire-plate electrode is measured in a platform with temperature adjustable. It is observed that with the decrease of temperature, the inception field and voltage increases pronouncedly in the range from −100 °C to 30 °C, which can be attributed to the rise of effective ionization and photon absorption.

Simulation Study on Discharge Process of Negative Polarity in UHV Tower-line Air Gap

Carrying out the research on the physical simulation model of the negative polarity discharge process in UHV tower-line air gap is of great significance to the lightning protection of UHV transmission lines. Based on the physical mechanism of negative discharge in long air gap, a physical simulation model including initial corona initiation and streamer development, leader initiation, streamer-leader system development, and final jump is established. The model considers the characteristics of corona initial development, the randomness of the leader path, and the negative development of the negative leader. Finite element software was used to calculate the background potential distribution of the gap, and the experimental observations were used to verify the model established in this paper. Finally, the model was used to simulate the discharge process of the negative polarity in tower-line air gap under actual size of tower window structure. The results show that the simulation calculations agree well with the test results.

Semiemprical Estimate of the Temperature of the Medium in the Corona Discharge of a Plasma-Chemical Reactor

Temperatures have been identified in the corona hood and streamer of a plasma-chemical reactor during the formation of a polymer film with carbon nanosized particles. A semiempirical procedure has been proposed to estimate these temperatures. It has been shown that in the case where the temperature in the streamer volume is ~600°C and it is ~1400°C in the corona hood, polycrystalline carbon nanoparticles are formed in the plasma-chemical reactor whose agglomerates penetrate into the polymer film.