Discharge Current Characteristics Research Articles

Simulation on the effect of oxygen concentration on the positive secondary streamer generated in oxygen-rich nitrogen–oxygen mixtures under atmospheric pressure

In this study, we investigated the effect of various O2 concentrations, from 20% to 90%, in nitrogen–oxygen ( N2/O2 ) mixtures on the characteristics of secondary streamers. As oxygen molecules have different molecular characteristics from nitrogen molecules in terms of ionisation threshold and electron attachment property, streamer discharges generated under various nitrogen–oxygen ratios may exhibit differing characteristics such as electron density, electric field, and radical formation. We focused on the changes in these parameters in secondary streamers using simulations. Simulations were first performed under the same conditions as those in previous experiments to compare the results of the ozone production, discharge current, and discharge emission characteristics. To compare the ozone production characteristics, simulated O radicals–the precursor of ozone–were used in the simulation for simplicity. This comparison showed that, although the absolute values of each parameter were different, the simulation exhibited a similar trend in the case of the experimentally obtained oxygen concentration dependence. After the validity of the simulation was verified to some extent via a comparison with the experiment, the results obtained from the simulation were analysed in detail. The results showed that, although the electric field strength in the secondary streamer did not change much as the oxygen concentration increased, the decrease rate of the electron density was greatly accelerated by the electron attachment reaction of oxygen. As a result, many of the electrons had already dissipate during the development of the primary streamer, and few electrons remained when the secondary streamer was formed. This effect suggests that the ratio of the amount of O radicals produced in the primary streamer to that produced in the secondary streamer changes as the oxygen concentration changes.

Multi-channel current electro-optic isolated measurement and discharge current characteristics in a parallel plate transmission line driver

Multi-channel current electro-optic isolated measurement and discharge current characteristics in a parallel plate transmission line driver

Conversion of CO2 in a pulsed arc discharge

We present a study of CO2 gas conversion into a mixture of CO2, CO and O2 by means of a pulsed arc discharge at atmospheric pressure. The CO2 molecule is dissociated as a result of the interaction with the highly energetic electrons and excited species produced in the plasma domain. The plasma conversion of CO2 provides a relatively simple approach to CO2 conversion without the need of special materials required by chemical reactors. In this study, the discharge operates at atmospheric pressure, which leads to a reduced efficiency compared to the low pressure operation due to the additional electron losses via elastic collisions. The operation at atmospheric pressure, however, provides simplicity, robustness and low cost of the discharge system, which makes it very attractive from an industrial point of view. Further, we use a pulsed discharge, which, in comparison to the DC discharges, provides additional possibilities for optimizing the dissociation process by controlling precisely the energy input into the plasma. This is achieved by controlling the pulse repetition rate and duty ratio in addition to the discharge current and gas flow characteristics. We present results for the CO2 dissociation rate and energy efficiency for a wide range of different discharge parameters.

Experimental scaling laws for the discharge oscillations and performance of Hall thrusters

Low-frequency (5–30 kHz) discharge current oscillations characterize the operation of Hall thrusters and represent a valuable metric not only to monitor the thruster behavior, but also to optimize the thruster performance. Two types of low-frequency oscillation modes are commonly observed: a global “breathing” mode, associated with the propellant ionization, and a local mode, typically characterized by a lower oscillation amplitude and the appearance of azimuthal spokes. The main characteristics of discharge oscillations and the transition between the two oscillation modes vary greatly with the thruster geometry and the operating condition. In this work, we present the results of an experimental campaign carried out on a 20 kW-class thruster prototype, SITAEL’s HT20k, with an exchangeable discharge channel and a magnetic circuit. Three different channel sizes were tested over a wide range of operating conditions and magnetic fields. For each operating point, a high frequency measurement of the discharge current was performed, recording the main characteristics of the oscillations. The data collected were then processed to derive the influence coefficients of each thruster parameter on the discharge current characteristics, as well as their dispersion. Finally, this allowed us to formulate general, data-driven scaling laws for the discharge current salient features, such as oscillation amplitude and dominant frequency. The gathered insight sheds light on the physical processes involved in the thruster discharge. At the same time, the possibility to model with simple functional laws the main oscillatory mode of Hall thrusters offers a unique aid to the optimization of thruster design and the evaluation of thruster performance during life.

Interaction between negative corona discharge and droplet emission from liquid Taylor cone

We investigated the behavior of droplets, the Taylor cone tip, and discharge current characteristics in electrospraying with negative corona discharge, and analyzed the interaction among them in the time scale of several micro seconds. Negative corona discharges using 1 wt% sodium dodecyl sulfate solution or ethylene glycol as liquid cathode were investigated, and the discharge current pulse had a distinctive structure with serial pulse trains. The pulse train structure indicated that the discharges from the Taylor cone are in the form of Trichel pulses with a dynamic cathode. We found that the electric field, liquid conductivity, and liquid viscosity had no significant effect on the discharge current characteristics, with the exception of the current peak value, whereas a higher electric field or higher liquid viscosity led to extended pulse train intervals and durations. These effects can be attributed to the change in time scale of the cone tip curvature variation. The above results indicate that the curvature radius of the cone tip dominates the discharges from the Taylor cone. The emission and transfer of droplets between electrodes were observed using back-lit images and Mie-scattered light images taken by a high-speed camera. The droplet emission was synchronized with the leading current in the Trichel pulses. The terminal velocity of the droplets transferring discharge gap was proportional to the revised electric field. The experimental results indicate that the droplet emission mechanism from the Taylor cone with discharges is supposed to differ from that without discharges explained by the Rayleigh limit. The reasonable explanation for the droplet emission mechanism is that the droplets are torn off the liquid cone tip by the strong electric field associated with discharges.

Analysis of the ESD Reconstruction Methodology Based on Current Probe Measurements and Frequency Response Compensation for Different ESD Generators and Severity Test Levels

System-level electrostatic discharge testing according to IEC 61000-4-2 has been the main standardized electrostatic discharge immunity testing procedure for the last few decades. The correlation between a failed test result and the injected electrostatic discharge current waveform characteristics, as well as the reduced reproducibility of the standard methodology, have always concerned product manufacturers and test engineers. In an effort to accurately reconstruct the electrostatic discharge current during immunity testing, researchers are focusing more and more on the usability of current probes in capturing the injected current in “real time”. In this article, the results of a proposed methodology, based on current probe measurements and a frequency response compensation method, published in recent bibliography, for different test levels and electrostatic discharge generators are presented, aiming to highlight the advantages and disadvantages of the method, investigate its universal applicability, and introduce points of future work toward the current reconstruction during system-level electrostatic discharge testing effort.

Modeling and parameter identification of composite power supply for plug-in HEV

By analyzing the characteristics of the components of PHEV composite power supply, the voltage characteristics, temperature characteristics and capacity efficiency of batteries and supercapacitor are clarified. The dynamic voltage characteristics of batteries and supercapacitor are simulated by modeling the composite power supply. Based on the cross current discharge characteristics of lithium-ion batteries and the application conditions of batteries in PHEV, the second-order linear battery model recommended in PNGV is selected in this paper; for supercapacitor, the simplified RC branch model can be used to describe the characteristics, and the experimental data are used to identify the parameters involved in the model, and the accuracy of the model is verified.

The Smart Rivers approach: Spatial quality in flood protection and floodplain restoration projects based on river DNA

AbstractMany river rehabilitation projects have been implemented in the past 30 years, strengthening the natural dynamics and ecology of river systems, while reconciling the functions of flood protection, navigation, sediment extraction, and cultural identity. Still, the planning and design of floodplain projects is subject to debate on how to best follow the “natural” characteristics of specific river stretches, the “DNA of the river.” Unlike many other approaches of integrated river management, this approach entails a design strategy for spatial quality in river floodplain development projects at local and regional level, where the current discharge characteristics of the upstream river basin are taken as given. Starting point is the landscape ecological basis of the river, defining the characteristic (hydro‐morphological) processes and geomorphological/geological structures in each stretch of the river and floodplain area. An in‐depth characterization of these structures and processes helps design floodplains that can accommodate the various river management and development objectives. Often economically strong functions, like flood protection, can be partnered with weaker ones, such as ecosystem restoration. To safeguard spatial quality and sustainability in these integrated projects, the governance aspect is essential. Therefore the Smart Rivers approach addresses both substantial aspects (the “DNA of the River”) as well as procedural and governance elements (called the “Quality Relay”). The principles of the approach are applicable to project design along regulated rivers in densely populated areas all over the world.This article is categorized under: Water and Life > Conservation, Management, and Awareness

Study on the Arc Motion Characteristics of Multi-Chamber Arrester Based on 3D Model

In ultra HVDC transmission system, arcing horn gap breakdown makes the arc hard to extinguish, threatening transmission safety. Multi-chamber arrester (MCA) is applied in extinguishing the arc to ensure safety. Here, we investigated the arc motion characteristics of the MCA to analyze its arc extinguishing ability. First, a three-dimensional model of the arc plasma in a single chamber was established based on magneto-hydrodynamic (MHD) theory, and the arc motion inside and outside the chamber were analyzed. Next, changes of temperature, velocity and pressure field were simulated. The results showed that the time required for arc totally exiting the chamber is approximately $96~\mu \text{s}$ , the airflow maximun velocity is about 865 m/s, and the highest pressure is more than 4 atm. Particularly, there is a flow reflux at the outlet, as the air flows inward from the outside and form an “oscillation”. Moreover, the arc motion characteristics of different discharge currents within different chamber structure were analyzed. It was found that the spacing between anode and cathode, the radius of electrodes and the outlet radius are the key factors regulating the airflow velocity, and the outlet radius of the chamber has the greatest influence. At last, the accuracy of our model was validated with experimental data.

Charging balance management technology for low-voltage battery in the car control unit with combined power system

The article presents the results of mathematical models and algorithms development complex, which is aimed at ensuring a positive charge balance of an automobile low-voltage rechargeable battery in car control systems with a hybrid power system. The aim of the work is to create and implement a set of software and mathematical models on one of the existing passenger car model, using the default components and systems of the car, to achieve a positive energy balance of the automotive low-voltage power network, and also to solve the problem of battery discharge by normalizing the turn-on time of powerful consumers leading to fast battery discharge. As criteria for the optimal performance of the proposed models and algorithms, the SOC parameters are considered - state of charge (%), battery charge (A * h), charge and discharge current of a battery (A), voltage on a battery during its charge when a charging current is absent or in a quiescent state (V), ambient temperature (˚C). Authors defined: composition of a control system, the necessary logic and a set of mathematical models implemented by electronic systems to control the charging balance of the automotive low-voltage power supply network, connections and functions of systems and components. As a result of a full-scale experiment, charge and discharge graphs, experimental data, current characteristics and dynamics of their changes during operation, experimental time-current dependencies during the operation of each component of a low-voltage power grid were obtained. The results of the work support to improve energy balance of an electrical power network, increase the efficiency and service life cycle of batteries, formulate system and technical requirements for control systems and their subsequent implementation. Versatility solutions are provided for improving management of charge balance car battery.

Monitoring leakage currents of suspension insulators of high voltage overhead power lines

The relevance of studying partial discharge currents (PDC) arising on the surface of suspension insulators of high-voltage overhead power lines (HVPL) is substantiated. Increasing PDC leads to increasing active energy losses and unauthorized shutdowns of high-voltage power lines due to the electric arc overlap of the suspension insulator. A laboratory bench for PDC experimental studying has been developed and manufactured. As a result of experimental studies we have determined static and dynamic characteristics of partial discharge currents; we have developed the algorithm for processing experimentally obtained results using Microsoft Excel spreadsheet editor. Recommendations have been developed for developing the hardware of the PDC sensor that allows increasing sensitivity, expanding the range of the controlled parameter and improving its dynamic characteristics in order to increase the accuracy and to expand the range of operation of the PDC sensor and to reduce the time it takes to establish its output signal. Equipping 220-500 kV power lines with PDC sensors of suspension insulators with telemetry will allow reducing the number of unauthorized emergency shutdowns of high-voltage power lines; realizing continuous current monitoring of the state of suspension insulators and receiving in real time the information of the integral value of PDC

Study of human blood under influence of magnetic field by AC dielectric and thermally stimulated discharge current methods

The aim of the present work is to study the effect of magnetic field on thermally stimulated discharge current (TSDC) characteristics and dielectric properties of human blood and to derive the useful parameters for the evaluation of DC and AC relaxation process. The TSDC and dielectric parameters of blood samples have been recorded under the influence of magnetic field. In low-frequency region, $$\varepsilon^{\prime}$$ decays rapidly and attains almost constant value in higher-frequency region; however, variation of imaginary part of permittivity is not similar to $$\varepsilon^{\prime}$$ . The variation of complex permittivity e* is characterized by a broad peak. The area of curves decreases with the increase in applied magnetic field. The dielectric loss (tan δ) varies from 0.4 to 1.8. The tan δ is characterized by a peak in lower-frequency region. The origin for variation of dielectric properties is the reduction in impedance and change in conductivity under the influence of electric and magnetic field. The TSDC maxima are observed at 54 ± 3 °C and 75 ± 5 °C with heating rate of 3 °C min−1 assigned as β and α peak, respectively. The height of peak is observed to be increased with forming magnetic field; however, positions of peaks are almost same.

Research on discharge effect of solar array with power supply subjected to hypervelocity impact

Plasma-induced discharge is an important effect on the solar array of orbiting space vehicles subjected to hypervelocity impact, which will pose a serious threat to the power supply system of spacecraft. The paper investigates experimentally the process that the projectile in various impact velocities and incidence angles impact on solar array with sandwich structure comprising of a coverglass, a silica gel and a 2A12 aluminum liner at the different positions. The electron temperature and density of the plasma were diagnosed by applying in independent-constructed Triple Langmuir Probe diagnostic system, meanwhile, the charging and discharge test system were also constructed by ourselves. Three sets of experiments have been performed by two-stage light gas gun loading system and related measurement system. Especially, residual velocity was measured when projectile pierced through the solar array with composite structure. Experimental results revealed the discharge causes based on stress wave theory, and the discharge current characteristics of a primary and a secondary discharge of solar array induced by hypervelocity impact were given through hypervelocity impact experiments. Finally, it will provide a valuable benchmark for the construction of solar array against space debris.

Alternating Current Discharge Characteristics and Simulation Analysis of Rod-Plane Short Air Gaps under Salt Fog Conditions

In this paper, smog meteorological conditions in the natural environment is simulated by the salt fog method. The study of the alternating current (AC) discharge characteristics of rod-plane short air gaps in salt fog environments has important guiding significance for how to strengthen the external insulation strength of ultra-high voltage (UHV) transmission lines and electrical equipment in smog environments. The rod-plane short air gap is selected as the model to simulate the extremely uneven electric field. The AC discharge test is carried out in the salt fog environment with different conductivity, and the finite element method (FEM) is used to simulate the distribution of electric field in air gap under salt fog environment conditions. The results show that under clean fog conditions the AC discharge voltage in the air gap increased by 15.1% to 35.5% compared to that under dry conditions. With the increased conductivity of salt fog, the AC discharge voltage in air gap decreased by 4.1% to 9.2% compared to that under clean fog conditions, and the reduction is within 10%. The distortion of the electric field and the adsorption of free electrons in the gap by droplets lead to the decrease of the electric field intensity in the air gap. With the increase of the conductivity, the electric field intensity in the air gap increases slightly. Meanwhile, the influence of salt fog and its conductivity on the AC discharge voltage of rod-plane short air gap is examined, becoming saturated with the increase of the gap distance and the conductivity of salt fog.

HVDC 인가에 따른 고체 절연물 부분방전 및 누설전류 특성 연구

HVDC 인가에 따른 고체 절연물 부분방전 및 누설전류 특성 연구

Mechanism of saline deposition and surface flashover on outdoor insulators near coastal areas part II: Impact of various environment stresses

This is the second in a two-part paper series dealing with sea salt transportation and deposition mechanisms, and discussing the serious issue of degradation of outdoor insulators resulting from various environmental stresses and severe saline contaminant accumulation near the shoreline. The deterioration rate of outdoor insulators near the shoreline depends on the concentration of saline in the atmosphere, influence of wind speed on the production of saline water droplets, moisture diffusion and saline penetration on the insulator surface. This paper comprises two parts. The first part, deals with the impact of different environmental stresses on insulator surface degradation, including wind speed and direction, cold fog and rainfall. The second part concerns the flashover process related to saline contamination of the surface under constant and variable cold fog wetting rates and equivalent salt deposit density (ESDD). The experiments were performed on high voltage insulators based on the model presented in Part-I. Based on the proposed model, the influence of wind speed and direction on the pollution accumulation rate and impact of wetting rate on discharge current and surface flashover process were investigated. The equations S=S0e(Vdep0/αh)[e(−αx/v)−1] and D=Doe(Vdep0/αh)[e(−αx/v)−1] are derived from the model for saline concentration and deposition show good reliability and well represent the results obtained. Test results also show that due to the different wetting and contamination deposition rate, surface discharge current characteristics of tested insulator in rain are different with that in cold fog, which lead to different surface flashover voltages. An experimental setup was mounted for artificial saline contamination deposition. The proposed model can be therefore used to investigate insulator flashover near coastal areas and for mitigating saline flashover incidents.

Negative DC corona discharge current characteristics in a flowing two-phase (air + suspended smoke particles) fluid

The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the “Trichel pulses superimposed on DC component” mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in “pure” air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in “pure” air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s.

Synthesis of hydrogenated diamondlike carbon thin films using neon–acetylene based high power impulse magnetron sputtering discharges

Hydrogenated diamondlike carbon (DLC:H) thin films exhibit many interesting properties that can be tailored by controlling the composition and energy of the vapor fluxes used for their synthesis. This control can be facilitated by high electron density and/or high electron temperature plasmas that allow one to effectively tune the gas and surface chemistry during film growth, as well as the degree of ionization of the film forming species. The authors have recently demonstrated by adding Ne in an Ar-C high power impulse magnetron sputtering (HiPIMS) discharge that electron temperatures can be effectively increased to substantially ionize C species [Aijaz et al., Diamond Relat. Mater. 23, 1 (2012)]. The authors also developed an Ar-C2H2 HiPIMS process in which the high electron densities provided by the HiPIMS operation mode enhance gas phase dissociation reactions enabling control of the plasma and growth chemistry [Aijaz et al., Diamond Relat. Mater. 44, 117 (2014)]. Seeking to further enhance electron temperature and thereby promote electron impact induced interactions, control plasma chemical reaction pathways, and tune the resulting film properties, in this work, the authors synthesize DLC:H thin films by admixing Ne in a HiPIMS based Ar/C2H2 discharge. The authors investigate the plasma properties and discharge characteristics by measuring electron energy distributions as well as by studying discharge current characteristics showing an electron temperature enhancement in C2H2 based discharges and the role of ionic contribution to the film growth. These discharge conditions allow for the growth of thick (>1 μm) DLC:H thin films exhibiting low compressive stresses (∼0.5 GPa), high hardness (∼25 GPa), low H content (∼11%), and density in the order of 2.2 g/cm3. The authors also show that film densification and change of mechanical properties are related to H removal by ion bombardment rather than subplantation.

Evaluation of Energy-Conversion Efficiency of Multineedle-to-Plate Corona-DBD Plasma for Organic Degradation in Soil

In this paper, energy-conversion efficiency ( $\eta $ ) of multineedle-to-plate corona-dielectric-barrier discharge (DBD) at atmospheric pressure was investigated for the application of degradation of organics in soil. Discharge current characteristics with applied voltage were measured. The factors contributing to $\eta $ included applied voltage, discharge frequency, multineedle electrode, and dielectric. $\eta $ increased with the applied voltage and resonant frequency generated the highest $\eta $ value. The number of needles and the variable distance between every two needles for the high-voltage electrode both had influence on $\eta $ . The examination of $\eta $ was also performed for the dielectrics characterization investigated. In order to facilitate the evaluation of the contribution of corona-DBD plasma to the remediation of organic-contaminated soil, p-nitrophenol (PNP) was used as target. Up to approximately 80% degradation was observed for PNP in soil exposed 3 mm away from the multineedle electrode. The plasma that remediated the soil sample with higher PNP concentration exhibited more efficient for the conversion of the electric energy.

Characteristics of Discharge Currents Measured through Body-Attached Metal for Modeling ESD from Wearable Electronic Devices

Characteristics of Discharge Currents Measured through Body-Attached Metal for Modeling ESD from Wearable Electronic Devices