High-voltage Pulsed Discharge Research Articles

Numerical simulation of the breakdown process of dielectric in high voltage pulse discharge

In order to study the breakdown process of the insulating medium of the needle-needle electrode under the action of high-voltage pulse discharge, the HV-LAB simulation software was used to study the discharge channel formed in the three kinds of insulating media, namely water, transformer oil, and air, and the three-dimensional model of the discharge breakdown insulating medium was designed. The process of discharge channel expansion, voltage, current, power, and energy loss in the discharge channel is analyzed. The results show that in the process of high-voltage pulse discharge breakdown of the insulating medium, the formation time of the discharge channel of transformer oil is long, the energy is accumulated, the number of discharge channels is less, the horizontal isopotential lines are dense, and the energy is concentrated. Under the same discharge conditions, the energy consumption of transformer oil in the process of high-voltage pulse discharge is the least. The results of this study can provide a reference for the selection of high-voltage crushing insulation medium.

Numerical Simulation of Electrode Structure on High Voltage Pulse Discharge Characteristics

For the study of the different electrode structures of the high voltage pulse discharge breakdown process of the insulating medium, the numerical simulation software is compiled to establish two kinds of the electrode structure of high voltage pulse discharge three-dimensional model, finite element difference method to simulate the expansion of plasma channel, the discharge characteristics of electrode structure internal voltage, and current of plasma channel and the impact of energy consumption. The simulation results show that, compared with the needle-needle electrode structure, the needle-plate electrode structure has a shorter time to reach the critical field strength of distilled water smaller breakdown voltage, shorter time to establish the discharge channel, smaller equivalent resistance, faster extension speed of the discharge channel, and less energy consumption for breakdown. And other conditions are the same. The results of this study can provide a theoretical reference for the structural design of high-voltage pulse-crushing electrodes.

Uniform Action of Plasma of a Nanosecond Pulsed High-Voltage Discharge on the Surface of a Flat Anode

The results of an experimental study of the effect of a plasma of a nanosecond pulsed high-voltage discharge in air at atmospheric pressure, excited in a sharply nonuniform electric field, on the surface of a flat-grounded electrode are presented. It is shown that at relatively large interelectrode distances between the pointed cathode and the flat anode, a diffuse discharge is implemented, which ensures a uniform action of the discharge plasma on the anode surface.

Stress wave analysis of high-voltage pulse discharge rock fragmentation based on plasma channel impedance model

High-voltage pulse discharge (HVPD) rock fragmentation controls a plasma channel forming inside the rock by adjusting the electrical parameters, electrode type, etc. In this work, an HVPD rock fragmentation test platform was built and the test waveforms were measured. Considering the effects of temperature, channel expansion and electromagnetic radiation, the impedance model of the plasma channel in the rock was established. The parameters and initial values of the model were determined by an iterative computational process. The model calculation results can reasonably characterize the development of the plasma channel in the rock and estimate the shock wave characteristics. Based on the plasma channel impedance model, the temporal and spatial distribution characteristics of the radial stress and tangential stress in the rock were calculated, and the rock fragmentation effect of the HVPD was analyzed.

Effects of Static Pressure on Failure Modes and Degree of Fracturing of Sandstone Subjected to Inter-Hole Pulsed High-Voltage Discharge

This research aims to explore the fracturing behaviors of sandstone subjected to pulsed high-voltage discharge (PHVD) under different static pressures. An experimental method of rock fracturing induced by inter-hole PHVD was proposed. The static pressure was applied to the specimens, then the proposed method was applied to induce electrical breakdown testing under static loading. The microscopic fracture morphology of the sandstone was observed. The influences of the direction and level of static pressure on the crack length and fractal dimension of sandstone under the effect of PHVD were discussed. The results indicated that in the absence of static pressure, there are a discharge channel and multiple radial cracks in the sandstone after electric breakdown. The microscopic analysis implies that rock failure in the zone around the discharge channel is mainly influenced by the high temperature; while radial cracks are induced by shock waves. When static pressure is vertical to the discharge channel, tensile and compressive stresses concentrate in different parts around the discharge channel, which can remarkably alter the distribution zone and propagation path of cracks. In addition, the fractal dimension and total length of cracks first decrease, then increase with increasing static pressure. When static pressure is parallel to the discharge channel, the distribution characteristics and propagation direction of cracks are unchanged; however, under this loading mode, circularly distributed hoop tensile strains are generated at the zone around the discharge channel, which enables the fractal dimension and crack length increase with increasing static pressure.

Prospective life cycle assessment of recycling systems for spent photovoltaic panels by combined application of physical separation technologies

The design of an optimal system for recycling photovoltaic panels is a pressing issue. This study performed a prospective life cycle assessment using experimental and pilot data to reveal the effectiveness of the proposed technologies. The proposed technologies include aluminum frame separation; precise mechanical separation consisting of primary and secondary grinding; the hot-knife method for glass/ethylene-vinyl acetate separation; and high-voltage pulsed discharge that targets copper and silver in cell sheets. Implementing resource recovery technology decreases landfill waste because the hot-knife procedure facilitates the reuse or recycle of glass. The largest concentration of copper busbar is produced by high-voltage pulsed discharge, which can be easily incorporated into smelting processes. The blending of low-concentration metal waste with other trash and ore changes the concentration criteria accepted in the smelting operations. Applying the detailed inventory data for the metal concentrations in this investigation could enhance the outcomes.

Evaluation of Conducted Electromagnetic Interference Behavior of Copper Vapor Laser

High power and high repetition rate electrically excited copper vapor laser (CVL) is a strong source of radiated and conducted electromagnetic interference (EMI). The thermal energy required to raise the temperature (∼1600°C) to generate copper vapor and the required voltage pulse for population inversion is provided by the pulse generating unit (PGU). The PGU generates a voltage pulse of the order of ∼13 kV with a rise time of less than 100 ns and a current pulse in the range of ∼500 A with a similar rise time. The high voltage and current generated by PGU along with the high voltage pulse discharge in the laser tube serves as a prominent source of EMI and affects the performance of nearby electronic devices. This article presents a comprehensive study of conducted EMI from a high-power and high voltage discharge inside the CVL system and its impact on laser performance. The conducted noise from the laser is a function of laser impedance and is proportional to the magnitude of load mismatch. A simple and robust technique is presented to reduce the conducted noise from CVL. The correlation between the laser electrode pin configurations and the conducted noise is also presented.

Improvement of circuit oscillation generated by underwater high voltage pulse discharges based on pulse power thyristor

High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by 77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.

Applications of Underbalanced Fishbone Drilling for Improved Recovery and Reduced Carbon Footprint in Unconventional Plays

Fishbone Drilling (FbD) consists of drilling several micro-holes in different directions from the main vertical or deviated wellbore. Similar to multilateral micro-hole drilling, FbD may be used to enhance hydrocarbon production in naturally fractured formations or in refracturing operations by interconnecting the existing natural fractures. When combined with underbalanced drilling using a coiled tubing rig, FbD enhances the production further by easing the natural flow of the hydrocarbon from the reservoir to the wellbore. The design aspects of the Fishbones include determining the number, length, distance between the branches, and the angle of sidetracking of the branches from the main borehole. In addition, the design of efficient drill string components to suit the FbD conditions are another important design aspect in FbD technology development. Examples of this include a high-performance small, diameter downhole motor and the use of High Voltage Pulsed Discharge (HVPD) plasma shock waves at different pulse frequencies and wave pressures to impose shear forces on the formation to break it more easily. This paper will present a comprehensive review of the FbD technology, including some of its current applications and design aspects. The possibility of using FbD in conjunction with hydraulic fracturing to boost production by creating a network of connected fractures will be discussed, and some of its technical and economic benefits and challenges will be compared

Monitoring of n-hexane degradation in a plasma reactor by chemical ionization mass spectrometry.

n-Hexane (C6H14) removal and conversion are investigated in a filamentary plasma generated by a pulsed high-voltage Dielectric Barrier Discharge (DBD) at atmospheric pressure and room temperature in a dry N2/O2 (20%) mixture with C6H14. The degradation of n-hexane and the by-product formation are analyzed in real-time using a high-resolution Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometer coupled with Chemical Ionization (CI). As alkanes are reacting slowly with H3O+ ions, two precursor ions were used: O2+ to follow the n-hexane mixing ratios and H3O+ to follow the mixing ratios of organic by-products. As the CI-FTICR technique can work at high mixing ratios, studies were made between 5 and 200 ppm of n-hexane. Absorption spectroscopy is also used to follow ozone and carbon dioxide molecules. We show that the DBD efficiency increases for lower n-hexane mixing ratios and a large number of by-products are identified, with the major compounds being: formaldehyde, acetaldehyde, propanal, carbon dioxide, and carbon monoxide along with nitrate compounds. Based on the nature of the by-products characterized, a mechanism accounting for their formation is proposed.

Evaluation of the antimicrobial effects of Capsicum, Nigella sativa, Musa paradisiaca L., and Citrus limetta: A review

The extensive use of antibiotics and vaccines against microbial infections can result in long-term negative effects on humans and the environment. However, there are a number of plants that have antimicrobial effects against various disease-causing microbes such as bacteria, viruses, and fungi without negative side effects or harm to the environment. In this regard, four particular plants- Capsicum, Nigella sativa, Musa paradisiaca L., and Citrus limetta have been widely considered due to their excellent antimicrobial effect and ample availability. In this review, we discuss their antimicrobial effects due to the presence of thymoquinone, p-cymene, pinene, alkaloids, limonene, camphene, and melanin. These antimicrobial compounds disrupt the cell membrane of microbes, inhibit cellular division, and form biofilm in bacterial species, eventually reducing the number of microbes. Extraction of these compounds from the respective plants is carried out by different methods such as soxhlet, hydro-distillation, liquid-liquid extraction (LLE), pressurized liquid extraction (PLE), solid-phase extraction (SPE), supercritical fluid extraction (SFE), pulsed electric field (PEF), microwave-assisted extraction (MAE), enzyme-assisted extraction (EAE), ultrasound-assisted extraction (UAE), and high-voltage electrical discharge. Suitable selection of the extraction technique highly depends upon the associated advantages and disadvantages. In order to aid future study in this field, this review paper summarizes the advantages and disadvantages of each of these approaches. Additionally, the discussion covers how antimicrobial agents destroy harmful bacteria. Thus, this review offers in-depth knowledge to researchers on the antibacterial properties of Capsicum, Nigella sativa, Musa paradisiaca L. peels, and Citrus limetta.

Revealing pre-breakdown processes of a single-gap pseudospark switch triggered from the anode side

Pseudospark switch is a special kind of low-pressure (typically 1–100 Pa) high-voltage pulsed discharge switch with the hollow electrode configuration. This paper experimentally investigates the pre-breakdown processes of a single-gap pseudospark switch triggered from the anode side. The species and contents of impurities on copper electrode surface are firstly analyzed, which mainly include C, N and O. Then, at the same conditions, the trigger delay and jitter of triggering from the anode side are significantly higher than the cathode side, as well as the minimum voltage and pressure that the switch can be triggered. The evolution of the discharge region of the pseudospark switch triggered from the anode side is observed by the ICCD camera for the first time in the literature. The time-resolved images show that the luminescence firstly appears in the hollow anode where the trigger discharge happens and then in the hollow cathode, the cathode hole, the main gap and the anode hole successively, which is completely different from triggering from the cathode side. Finally, a model considering the migration and collisions of ions and fast atoms is established, and it points out that the ion flux from the hollow anode plays an important role in triggering from the anode side. The key processes also include the formations of the positive space charge column inside the hollow cathode and the intense secondary electron emission as an electron source for the main gap.

Delay Correction for Pre-Breakdown Phase of Subsonic Stream Discharge in Water

Shock waves generated by streamer discharge in water have huge application value to improve unconventional reservoirs. In this paper, experiment platform for high-voltage pulse discharge in water, which beneficial to research the pre-breakdown phase of subsonic streamer discharge in water of high-frequency discharge application scenarios is established. The mechanism of stream discharge and the importance of polarization process were analysed by high voltage theory. The initial time of flow column development was determined based on the time-varying characteristics, and the time of pre-breakdown phase was corrected by using the lightning shock intercept analysis theory. The results show that the polarization process should be incorporated into the pre-breakdown phase. Meanwhile, the initial development time of the flow column is the 3μs of the experimental data. After modification, the polarization process is shortened by 0.9372μs and the delay correction ratio is 24.57% after modification.

Plasma-enhanced electrostatic precipitation of diesel exhaust particulates using nanosecond high voltage pulse discharge for mobile source emission control

This study reports enhancement in the electrostatic precipitation (ESP) of diesel engine exhaust particulates using high voltage nanosecond pulse discharge in conjunction with a negative direct current (DC) bias voltage. The high voltage (20 kV) nanosecond pulses produce ion densities that are several orders of magnitude higher than those in the corona produced by a standard DC-only ESP. This plasma-enhanced electrostatic precipitator (PE-ESP) demonstrated 95 % remediation of PM and consumes less than 1 % of the engine power (i.e., 37 kW diesel engine at 75 % load). While the DC-only ESP remediation increases linearly with applied voltage, the plasma-enhanced ESP remains approximately constant over the applied range of negative DC biases. Numerical simulations of the PE-ESP process agree with the DC-only experimental results and enable us to verify the charge-based mechanism of enhancement provided by the nanosecond high voltage pulse plasma. Two different reactor configurations with different flow rates yielded the same remediation values despite one having half the flow rate of the other. This indicates that the reactor can be made even smaller without sacrificing performance. Here, this study finds that the plasma enhancement enables high remediation values at low DC voltages and smaller ESP reactors to be made with high remediation.

Effects of Confining Pressure and Hydrostatic Pressure on the Fracturing of Rock under Cyclic Electrohydraulic Shock Waves

For an array of applications of the high voltage pulse discharge technology in reservoir stimulations and to gain a deeper understanding of the fractures mechanism of deep well rock under cyclic electrohydraulic shock waves (EHSWs), the effect of confining pressure and hydrostatic pressure on the fracturing of rock under EHSWs are investigated in this paper. Firstly, a two-dimensional (2D) water-explosive numerical model is built to match the computed peak pressure of the EHSW with that obtained by the empirical formula by tuning the relevant parameters, based on the equivalent method of EHSWs. Then, a rock model is established to obtain the stress distribution under static loads. Subsequently, the water-explosive model is coupled with the rock model to obtain the stress distribution under static and dynamic loads. In addition, based on this coupling model, the influences of confining pressure and hydrostatic pressure on circumferential stress, radial stress in the rock and the fracturing of rock around the wellbore are discussed. Finally, two improvement measures (increasing discharge energy and changing loading mode) are proposed to acquire greater fracture density based on intensive numerical simulations. The results show that the increase in hydrostatic pressure is beneficial to the crack formation and development, whereas confining pressure is harmful. Moreover, the inhibitory effect of confining pressure on crack formation is greater than the promotion effect of hydrostatic pressure on crack formation. Increasing the discharge energy can effectively promote the development of the number and length of main cracks. Under four repetitive loading modes with the same total discharge energy (1.36 × 15 kJ), the greatest fracture density can be obtained by using repetitive loading mode with a gradually decreasing mode of discharge energy (first level: 2 times (1.36 × 5 kJ); second level: 5 times (1.36 × 1 kJ)).

Optical Emission Spectroscopy of Underwater Spark Generated by Pulse High-Voltage Discharge with Gas Bubble Assistant

This paper is aimed at the investigation of the acoustic and spectral characteristics of underwater electric sparks generated between two plate electrodes, using synchronized gas bubble injection. There are two purposes served by discharge initiation in the bubble. Firstly, it creates a favorable condition for electrical breakdown. Secondly, the gas bubble provides an opportunity for the direct spectroscopy of plasma light emission, avoiding water absorption. The effect of water absorption on captured spectra was studied. It was observed that the emission intensity of the Ha line and a shockwave amplitude generated by discharge strongly depend on the size of the gas bubble in the moment of the discharge initiation. It was found that the plasma in the underwater spark channel does not correspond to a source of black-body radiation. This study can be also very useful for understanding the difference between discharges produced directly in a liquid and discharges produced in gas/vapor bubbles surrounded by a liquid.

Influence of Pulse Amplitude and Frequency on Plasma Properties of a Pulsed Low-Current High-Voltage Discharge Operated at Atmospheric Pressure

Non-equilibrium conditions in plasma are often achieved by pulsed power delivery, where the pulse shape and repetition rate determine the properties of the plasma constituents and thus its chemical reactivity. The evaluation of the latter is becoming increasingly important to understand the observed effects, especially when new application fields are targeted. The composition of the plasma and the occurring chemical reactions can be calculated using various models. Thereby, the temperature of the electrons, the electron number density, as well as the heavy particle temperature are usually required as the basis of such calculations. In this work, the influence of pulse amplitude and repetition rate on these plasma parameters is determined by laser scattering for a low-current, high-voltage discharge operated with nitrogen at atmospheric pressure. In particular, the characteristic parameters regarding the plasma free electrons in such discharges have not yet been experimentally determined to this extent. The results are validated by spectroscopic measurements, i.e., the electron density is estimated from the Stark broadening of the hydrogen beta line and the heavy particle temperature is estimated by fitting the spectrum of nitrogen molecular transitions. Depending on the operating frequency, a pure nitrogen discharge with an input power of about 650 W displays an electron density between 1.7×1021m−3 and 2.0×1021m−3 with electron temperatures in the range of 40,000 K and heavy particle temperatures of about 6000 K in the core of the discharge channel. Furthermore, a relatively slow electron recombination rate in the range of 20 µs is observed.

Spectroscopic Characterization of a Pulsed Low-Current High-Voltage Discharge Operated at Atmospheric Pressure

The advantages of pulsed low-current high-voltage discharges operated at atmospheric pressure and the ease with which such discharges can be implemented industrially contributed to their popularity. However, the high reactivity of a pulsed plasma implies that thorough diagnostics are needed to fully understand the interactions inside these plasmas. Some of the key parameters determining plasma properties of low-current discharges are the electron number density and the temperature of heavy particles. Both parameters can be determined experimentally with spectroscopic techniques, for example by investigating the broadening of spectral lines due to the Stark effect and by fitting synthetic spectra to molecular transitions. To the authors’ knowledge, experimentally determined electron densities for pulsed low-current discharges operated in a power range between 300 W and 1000 W have not been performed in previous works. Thus, in this work, the electron number density and temperature of heavy particles of one of several commercially available plasma systems are determined by means of emission spectroscopy.

Experimental Study of the Structural Damage to Coal Treated by a High-Voltage Electric Pulse Discharge in Water

Experimental Study of the Structural Damage to Coal Treated by a High-Voltage Electric Pulse Discharge in Water

Energy Plasma Graphite Wastewater Treatment System Based on Internet of Things Platform

If graphite plasma wastewater cannot be properly treated, it may cause serious pollution to the natural environment. In this paper, the conditions of wastewater degradation by high-voltage pulse discharge are optimized. On this basis, it is proposed to improve the discharge power supply and reactor to effectively strengthen the discharge and improve the degradation rate of organic matter. The wastewater is degraded by high-voltage pulse discharge and coagulation Fenton oxidation. The specific degradation effect is as follows: when the initial pH of aeration is about 10.00 mm and the initial pH of aeration is about 80 mm/L, the specific degradation effect of wastewater is about 1.00-200 mm. The degradation rate of chemical oxygen demand in 120 min can reach 49.84%. The graphite plasma wastewater treatment system designed based on the Internet of things platform has made a great contribution to the balance between industrial production and natural environment in China.