Corona Discharge Current Research Articles

Fabrication of Hydrophilic Organosilicon Coatings and Study of Their Resistance to Factors Accompanying Corona Discharge

Modern power industry widely uses high-voltage overhead lines to transport electricity, which are characterized by problems of corona discharge and leakage currents, especially in rain and snow conditions. One approach to solve these problems is to create protective coatings that can reduce corona in adverse weather conditions. This paper presents a study of a hydrophilic organosilicon coating based on aminopropyltriethoxysilane and PEG-400 for aluminum wires. Studies conducted to assess the resistance of the coating to prolonged contact with water, UV radiation and an ozone-saturated atmosphere have shown that the hydrophilicity of the coating increases under effect of these factors, which improves its anti-corona properties. Thus, durability under operating conditions open prospects for use of the developed coating in the energy sector.

Instrumentation for Sub-Ampere Lightning Current Measurement on a Tall Meteorological Tower in Complex Electromagnetic Environment

Measurement of lightning current plays a critical role in the field of atmospheric electricity. Traditionally, Rogowski coils or low-resistance shunts were employed for measuring lightning currents in the range from several amperes up to several hundreds of kilo-amperes, and high-value resistors were utilized for measuring corona discharge currents at sub-ampere levels. However, these approaches were not suitable for continuously recording the vast range of lightning currents. For this sake, we have developed a lightning current measurement system equipped with a shock-tolerant low-noise amplifier module. With the system installed on a tall tower, sub-ampere level currents just before the lightning initiation were observed for the first time. To confirm the authenticity of the recorded currents, the background noise of the measurement system and surrounding environment were identified, and a digital multi-frequency notch filter was proposed for de-noising. Results show that the system can achieve a current identification level of 50 mA even in complex electromagnetic environments, while having a measurement capability of 220 kA.

Laser nanoengineered coatings for efficient energy transportation through corona discharge suppression

Overhead high-voltage transmission lines are crucial for the modern power transportation industry, but their operation in an open atmosphere raises concerns regarding durability, corona discharge, and leakage currents, which have economic and environmental impacts. To mitigate these issues, new functional materials are being developed using laser nanotechnology, such as superhydrophobic, superhydrophilic, and SLIPS coatings. The suitability of each coating depends on specific operating conditions, requiring a compromise between various wire properties. In this study, we investigated the efficiency of these coatings in reducing corona discharge currents under dry and rainy weather conditions. Our research showed that superhydrophobic and superhydrophilic coatings effectively reduce corona discharge currents by up to 2–4 times, while SLIPS coatings, despite water-repellent properties, increase corona currents in rainy conditions. The obtained results allow suggesting two promising paths toward the improvement of corona protection by enhancing the durability of superhydrophobic coatings under intermittent prolonged rainy conditions and reducing ice adhesion to superhydrophilic coatings.

A Numerical Simulation Study on DC Positive Corona Discharge Characteristics at the Conductor’s Tip Defect

For investigating the relationship between the surface corona discharge of a DC wire and other influencing factors, a hybrid numerical model based on a fluid-chemical reaction was proposed to simulate the discharge process at the tip defect of the wire. Under different defect geometries and gas pressures achieved via simulation, the microscopic process of the reaction and movement of electrons and heavy particles during a positive corona discharge was studied, and characteristic parameters such as corona inception voltage and discharge current were analyzed. Furthermore, through the corona cage test, for a specific electrode configuration, corona inception voltages under different pressures were compared and verified, which showed that the model was reasonable. The results showed that the maximum electron density of the streamer head was about 1 × 1020 m−3, the rise time of the pulse current was about 10 ns, and the decay time was about 300–500 ns. The corona inception voltage decreased with an increase in the tip height and decreases in the tip curvature radius, conductor radius, and background air pressure; the amplitude of the pulse current increased with increases in the wire radius and curvature radius of the defect tip and decreases in tip height and background air pressure. The experimental results are consistent with the simulation results, which verifies the reasonability of the model.

Identification of corona discharges based on wavelet scalogram images with deep convolutional neural networks

This paper presents a new wavelet-based approach to automate the identification of positive and negative DC corona discharge current pulses. Two electrode systems with variable gap spacings formed corona discharges, and two commercial sensors (a high-frequency current transformer (HFCT) and a shunt resistor) captured transient corona discharge currents. The proposed method employs a continuous wavelet transform to generate time-frequency representations of corona discharge pulse currents, called scalogram images. The effects of sampling interval, data acquisition time, data shifting, and external noise components in the signals on the scalogram images were examined. The well-known pre-trained convolutional neural network models, AlexNet, MobileNet, and ShuffleNet, were tailored, and their ensemble structure was generated to discriminate scalogram images of discharge pulses. A framework was constructed to increase the generalization ability of the study. The results demonstrate that the scalogram images are robust candidates for corona discharge identification.

A High Kinetic Energy Ion Mobility Spectrometer for Operation at Higher Pressures of up to 60 mbar

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at absolute pressures around 20 mbar in order to reach high reduced electric field strengths of up to 120 Td for influencing reaction kinetics in the reaction region. Such operating points significantly increase the linear range and limit chemical cross sensitivities. Furthermore, HiKE-IMS enables ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to additional reaction pathways and fewer clustering reactions. However, operation at higher pressures promises increased sensitivity and smaller instrument size. In this work, we therefore study the theoretical requirements to prevent dielectric breakdown while maintaining high reduced electric field strengths at higher pressures. Furthermore, we experimentally investigate influences of the pressure, discharge currents and applied voltages on the corona ionization source. Based on these results, we present a HiKE-IMS that operates at a pressure of 60 mbar and reduced electric field strengths of up to 105 Td. The corona experiments show shark fin shaped curves for the total charge at the detector with a distinct optimum operating point in the glow discharge region at a corona discharge current of 5 μA. Here, the available charge is maximized while the generation of less-reactive ion species like NOx+ is minimized. With these settings, the reactant ion population, H3O+ and O2+, for ionizing and detecting nonpolar substances like n-hexane is still available even at 60 mbar, achieving a limit of detection of just 5 ppbV for n-hexane.

Comparison of Initiation and Temporal Evolution of Positive and Negative Ionic Wind Under Needle-to-Plate Electrode

Considerable research efforts have been devoted to the generation, characterization, and optimization of ionic wind produced by corona discharge. The current article tries to explain the mechanism that causes the different behaviors observed in negative and positive dc corona ionic wind. The steady-state and the transient state ionic wind produced by both polarities are studied through particle image velocimetry (PIV) technology. The results show that at transient state, a series of mushroom-like jets are produced in negative corona discharge ionic wind due to the effect of Trichel pulse. These jets merge with each other and combine momentum to form the wide structure at steady state. In comparison, the positive corona discharge current has no pulse, and the ionic wind has only one “I-shape” wave head during the initiation process. The dynamics of the jets is studied in detail. The formation of the jet series in negative corona, or single jet in the case of positive corona, is believed to play a key role in the generation of ionic wind.

Simulation and Study of DC Corona Discharge Characteristics of Bar-Plate Gap

In this paper, the corona discharge process of the bar-plate gap at −1 kV DC voltage is simulated using a two-dimensional axisymmetric plasma module. We analyze the variation of air negative corona discharge current, and the distribution morphology of microparticles in different discharge stages in detail. The significance of plasma chemical reactions at some typical time and the distribution characteristics of heavy particles are investigated according to reaction rates. Results show that, in the current rising stage, the collision ionization reactions (e.g., R1 and R2) and electron adsorption reaction (e.g., R3) play a major role, which lead to the increase in charged particles and the formation of an electron avalanche. In the current drop stage, all reaction rates decreased, except for collision ionization and electron attachment, partial charge transfer reactions (e.g., R8, R10, R11, and R14), and composite reactions (e.g., R16, R17, and R18), which come into play and gradually reduce the number of charged ions in the gap. In the current stabilizing stage, the main chemical reactions are composite reactions (e.g., R16 and R17), then the corona discharge ends. For the heavy particle distribution, O2+ and O4+ are the main positive ions, O2− is the most abundant negative ions, and the neutral particles are mainly O.

Investigation of the Energy Efficiency of Electrohydrodynamic Drying under High Humidity Conditions

Electrohydrodynamic (EHD) drying is an emerging drying technology that is based primarily on the phenomenon of ionic discharge between two electrodes. The aim of this study was to experimentally investigate the energy efficiency of the EHD drying based on the corona discharge current. Moreover, we aimed to compare the energy efficiency of the EHD drying with that of other available drying technology options under the condition of high humidity, which mimics Indonesia’s environment as a potential target for implementation, given that it is of interest to investigate the feasibility of the EHD drying in a real environment. The results show that the dominant parameters of the EHD drying rate are the corona discharge current and the moisture content zones of the target objects. Findings from this study show that the EHD drying technology could be effectively used to replace the conventional drying process in developing countries having high humidity environments and facing energy consumption challenges.

Qualitative Determination of Polysulfide Species in a Lithium-Sulfur Battery by HR-LC-APCI-MSn with One-Step Derivatization.

Lithium-Sulfur (Li-S) batteries are one of the most promising next-generation batteries due to their ultrahigh energy density up to 500 W h kg-1. However, despite the steady progress during the last several decades, there have been significant challenges for practical applications and commercialization. One of the major issues is controlling the lithium polysulfide (LiPS) shuttling process, which causes premature cell failure. To better understand the mechanism of the LiPS shuttling chemistry, a qualitative and quantitative analysis on polysulfide species in Li-S cell has profound significance for realizing highly efficient sulfur electrochemistry. Here we report a qualitative determination of the derivatized polysulfides in the electrolyte of a custom-made Li-S pouch cell with a high-resolution liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry method for the first time. The ionization efficiency of the methylated polysulfides was affected by the tune parameters such as the corona discharge current, the vaporizer temperature, and the source capillary temperature. It was found that the source capillary temperature was the dominant parameter to increase the peak intensity of CH3S7- ion, which was the smallest peak in the spectrum. An unusual and unique ionization pattern for methylated polysulfides detected in atmospheric pressure chemical ionization negative mode was elucidated by using first-principles calculations.

Application of a nanosecond corona discharge generator for electrical separation of ores

The use of a pulsed nanosecond voltage source in a corona separator was investigated. Measurements of the distribution of corona discharge current were obtained. The influence of the interelectrode distance on the distribution of the corona discharge current was investigated. Experiments with gold-bearing quartz-sulfide ore and ilmenite ore were carried out. A concentrate was obtained with a gold content of 48 g/t, a mass equal to 18.7% of the original, which corresponds to the extraction of 92% of gold. The titanium content of ilmenite was enriched from 2.87% to 18.1%.

“Electrical wind” in CO2–laser mixtures at superatmospheric pressures

This article presents the results of “electrical wind” investigations in CO2–laser mixtures at superatmospheric (1–12 atm) pressures. It is established that for a fixed value of the unipolar corona discharge current, the gas flow velocity does not depend on the pressure, but is determined by the chemical composition of the working mixture. The maximum values of the “electrical wind” velocity are achieved in carbon dioxide and molecular nitrogen and their values are 3.2 and 2.9 ms−1. In typical laser mixtures CO2:N2:He = 1:1:1 – 1:1:3 the velocity of the “electrical wind ” are in the range from 2.5 to 1.5 ms−.

Features of streamer form of corona discharge in respect to electric gas purification

An article briefly describes advantages of streamer form of corona discharge over corona discharge of direct voltage. With the purpose of confirmation of hypotheses about possibility of stabilization of discharge processes in electric fields of streamer form of corona discharge oscillography voltage and current were done, and volt amperage features at various frequencies of pulse voltage were taken. Impact of parameters of electrodes system «Potential plane with corona needles – grounded plane» to value of discharge current was studied. Outcomes of study of power features and character of change in strength of electric fields of streamer form of corona discharge are presented.

Best choice of insulation gas medium for MMGS in fast linear transformer driver

Gas spark closing switch is one of the most important components for a fast linear transformer driver (FLTD). In this paper, we describe the investigation of insulation gas media for a multi-gap multi-channel gas spark closing switch. A six-gap gas switch with corona needles was tested in a typical FLTD brick with two capacitors of 40 nF and a load resistor of about 10 Ω. Corona discharge current, self-breakdown voltage distribution, and triggered breakdown performance were tested when the gas switch was filled with air, N2, CO2, SF6/N2, and C4F7N/N2. When C4F7N/N2 was applied, there was no abnormal breakdown with low voltage found in the whole test process; the trigger breakdown delay time and switch jitter were very stable, and no pre-fire was found during about 2000 triggered shots. Therefore, we think the C4F7N/N2 gas mixture with a very little amount of C4F7N can dramatically improve the switch performance. It is valuable and easy to realize the application of C4F7N/N2 mixture in large scale pulsed power facilities.

Some geometrical and electrical aspects on the wire-to-cylinder corona discharge

Corona discharge is a gas discharge that can be applied in a vast number of industrial applications. In all of them, knowing the current-voltage curves (CVCs) is of high importance because they determine the corona discharge operation range, from the inception voltage to the breakdown voltage. The CVCs are influenced by geometrical factors, ambient conditions and electrical parameters so the one only way to increase operation range without achieving spark voltage is lowering the inception voltage. Regarding geometrical parameters, it is widely known that reducing the distance between electrodes decreases the inception voltage, however two behaviours are found for the emitter radius in the literature. One of them establishes that there is a limit to the emitter size from which there is no change in the CVCs, while the another theory states that by reducing the emitter radius there is always an increase in the corona current. A series of measurements were carried-out for wire-to-cylinder corona discharge in parallel arrangement to study the influence of geometrical and electrical parameters over the current-voltage curves, mainly focusing in the wire radius. The results show that reducing the emitter radius always produces an increase in the corona discharge current. Although the inception voltage is generally higher for positive than for negative polarity, the experimental data suggest that there is an emitter radius from which this trend changes, being the negative inception voltage larger than for positive i.e. the inception voltage depends on the polarity of the discharge and the wire radius. Furthermore, the determination of the inception voltage by using four formulae is compared with the experimental data due to its importance to establish the operation range of corona devices. The influence of geometrical parameters is especially relevant to design and manufacture corona discharge devices e.g. low noise and without moving parts flying systems.

Pulse Current of Multi-Needle Negative Corona Discharge and Its Electromagnetic Radiation Characteristics

Negative corona discharge occurs widely in high voltage transmission lines and other “high voltage” uses, which can cause strong electromagnetic interference (EMI). In this research, the pulse current of multi-needle negative corona discharge and its electromagnetic (EM) radiation characteristics were studied and compared with that of single-needle negative corona discharge. A dipole radiation model was established to analyze the EM radiation characteristics of the negative corona discharge. The results show that the Trichel pulse discharge process of one discharge needle in multi-needle discharge structure will inhibit the discharge of the other discharge needles. It is only when the voltage reaches a certain threshold will the current and EM radiation fields of multi-needle discharge structure with a significant increasing of amolitude. The frequency of EM radiation of negative corona discharge is not affected by the number of needles, but is only related to ambient air pressure. This research provides a basis for detecting corona discharge sources in different conditions.

DC negative corona discharge characteristics in air flowing transversely and longitudinally through a needle-plate electrode gap

The electrical characteristics of a steady-state DC negative corona discharge in air flowing transversely or longitudinally in relation to the needle-to-plate (or mesh) electrode axis were experimentally investigated. The velocity of air flowing into the corona discharge chamber was limited to a range from 0 to 6 m/s, typical of electrostatic precipitators, gas ionisation sensors and EHD pumps. The investigations showed that in this airflow velocity range three discharge current modes of the DC negative corona could exist: the Trichel-pulse corona mode, the ‘Trichel pulses superimposed on the steady current (or DC) component’ mode and the steady glow (the steady current or DC) corona mode, regardless of the airflow direction. The average corona discharge current, which is a macroscopic corona discharge parameter, was almost not affected by the airflow. However, both microscopic corona discharge parameters: the electric charge and the repetition frequency of Trichel pulses were influenced by the airflow. The transverse airflow caused an increase in the electric charge and a decrease in the repetition rate of Trichel pulses, the both by about 25% at a velocity of 6 m/s. In the case of longitudinal airflow the average corona current slightly increased when the airflow was directed towards the mesh and decreased when the airflow was directed towards the needle tip. Similarly as in the case of transverse airflow, the electric charge and the repetition frequency of Trichel pulses were affected by the longitudinal airflow. The electric charge and the repetition frequency of Trichel pulses increased and decreased, respectively, with growing airflow in the direction towards the needle electrode. The airflow growing in the direction towards the mesh electrode produced the opposite effect - the electric charge and the repetition frequency of Trichel pulses decreased and increased, respectively. The opposite behaviours of the electric charge and the repetition frequency of Trichel pulses with growing airflow velocity could explain the weak dependence of the negative corona average current on transverse or longitudinal airflow. Therefore, the independence of the negative corona average current of the airflow cannot be considered as sufficient proof that the airflow (up to 6 m/s) does not affect the negative corona parameters.

Experimental analysis of direct current corona discharge

This paper presents the experimental analysis of current-voltage characteristic of DC corona discharge. In experiments were used an electrostatic discharge system, consists of an active brass electrode, and a passive copper electrode (plane). A high-voltage source has been used to produce the positive or negative DC discharge. To analyse the influence of active electrode surface were used a conical and a spherical electrode, with small radius of curvature. The gap between the electrodes was varied by moving the passive electrode. Current-voltage characteristics of DC corona discharge were obtained at a constant distance between the discharge electrodes, by changing the amplitude of supply voltage. Corona current and voltage were acquired using a digital oscilloscope. Experiments allowed the study of the effects due to the active electrode and the air gap between the electrodes, on the onset voltage and the current of corona discharge.

Dielectric Breakdown-Assisted Corona Discharge-Based Pressure Sensor Using Poly-Si Microtips

We report the development of low-power, dielectric breakdown-assisted corona discharge (CD)-based ionization pressure sensor for low-to-high vacuum measurements. The device possesses a reduced interelectrode spacing $d_{\mathrm{ int}}$ ( $= 1.25~\mu \text{m}$ under unbiased condition) and utilizes sharp microtip corners to generate electric field $E \,\, >$ dielectric breakdown field of the air $E_{b}$ (=3 MV/m) at low bias voltage $V_{b}> 2$ V. $E$ developed at the microtips ionizes the air molecules through dielectric breakdown of the intervening medium to produce ionization current, which obeys the modified CD current expression. The CD current has power law dependence on pressure and is utilized in the development of pressure sensor. Three variants of devices with single $(T_{1})$ microtip, 50 $(T_{50})$ microtips, and 100 $(T_{100})$ microtips are fabricated using the surface micromachining technique, and their performance is investigated and compared. Enhanced sensor performance is obtained for the device with an increased number of microtips $J$ . Our proposed device $T_{100}$ offers a wide dynamic range of $10^{-4} \,\, -50$ mbar and a high sensitivity of $2.03~\mu \text{A}$ /mbar and consumes low power of $0.34~\mu \text{W}$ .

On temperature dependence of the parameters of corona discharge current–voltage characteristics

The dependences of the parameters of corona discharge current–voltage characteristics on the gas temperature are considered in this work. It is shown that the corona discharge ignition voltage U c (T) of helium and nitrogen decreases with the increase in temperature. The dependence of the parameter A(T) is complicated. It increases at the initial and final sections of the studied temperature range (20–369°C) and decreases at its central portion with two extrema. As the discharge in nitrogen is unstable, we failed to obtain any definite regularity. Generalized dependences that make assertions about the presence of a discharge different from a corona are presented. We made an assumption of an important role of two effects in the observed processes: the absorption of ions by the surface of electrodes and the continuous change in ion mobility due to the ion mass variation in the course of clustering and declustering of ions. It is supposed that there is a dynamic equilibrium between them in a steady state.