Magnitude Of Applied Voltage Research Articles

Extinguishing and Combustion Characteristics of Electrically Controllable Solid Propellants Under Elevated Pressures

An experimental study was conducted on electrically controllable solid propellants (ECSPs) created using a polyethylene oxide polymer binder, lithium perchlorate, and multiwalled carbon nanotubes. The propellants decompose and ignite shortly after the application of a voltage potential and extinguish when the voltage is removed under atmospheric conditions. The ignition delay as a function of the applied voltage magnitude was determined for a range of ECSP compositions. Pressurized experiments were conducted in an optically accessible strand burner to characterize the burning properties of the ECSPs as a function of pressure and electrical power. Additional experiments were conducted at elevated pressures where the voltage potential was removed and reapplied to extinguish and reignite the propellant and determine the self-extinction limits of the ECSPs. The results demonstrate that small compositional changes can drastically impact the ability to extinguish the ECSPs at elevated pressures.

Zinc (II) removal from simulated wastewater by electro-membrane extraction approach: Adopting an electrolysis cell with a flat sheet supported liquid membrane

The aim of this study is to utilize the electromembrane extraction (EME) system as a manner for effective removal of zinc from aqueous solutions. A novel and distinctive electrochemical cell design was adopted consisting of two glass chambers, a supported liquid membrane (SLM) housing a polypropylene flat membrane infused with 1-octanol and a carrier. Two electrodes were used, a graphite as anode and a stainless steel as cathode. A comprehensive examination of several influential factors including the choice of carrier, the applied voltage magnitude, the initial pH of the donor solution, and the initial concentration of zinc was performed, all in a concerted effort to ascertain their respective impacts on the efficiency of zinc elimination. Two distinct carriers, namely tris(2-ethylhexyl) phosphate (TEHP) and bis(2-ethylhexyl) phosphate (DEHP) were evaluated, in a tandem with utilization of 1-octanol. The results revealed essential role played by the applied voltage in augmenting the rate of mass transfer of zinc across the membrane. The best operating conditions were utilized for 1-octanol enriched with 1.0 vol.% bis(2-ethylhexyl) phosphate as a carrier, applied voltage of 60 V, initial pH of 5, initial zinc concentration of 15 mg L-1, extraction duration of 6 hours, and stirring rate of 1000 rpm. Surprisingly, operating under these meticulously devised conditions culminated in the outstanding removal efficiency of 87.3 %. In comparison with no applied voltage, a substantial enhancement in removal efficiency was observed, trans­cending from a meager 36.67 % to an impressive 87.3 % at 60 V, suggesting thus a tremen­dous potential of EME as an efficacious technique for the elimination of heavy metals.

Organic phase change materials melting with electrohydrodynamics (EHD): Numerical simulation and experimental validation

Electrohydrodynamics (EHD), as an active heat transfer enhancement technique, would dynamically manipulate the performance of latent heat thermal storage (LHTS) system. In this paper, the melting characteristics of octadecane with EHD were simultaneously investigated by numerical simulation and experiments. A numerical model based on the finite volume method was developed to solve the Poisson-Nernst-Planck equation, Navier–Stokes equation, and energy equation. The solid-liquid interface position, charge density distribution, velocity field, and liquid fraction were reported. The accuracy of the numerical model was evaluated by the experimental results. For the case of melting without EHD, the numerical results agree well with the experimental results. The relative error between the simulation and experiment is less than 20.0% for the case of melting with EHD. The melting time would be significantly saved with the increasing applied voltage magnitude and inner electrode temperature. The melting time with EHD would be reduced by 13.6 times compared to the natural melting case. The flow in the liquid phase is chaotic and the Coulomb force is dominant than the dielectric force and the buoyancy. In addition, the influence of electrode arrangement on the melting behavior is studied. The melting can be decreased by 1.26 to 1.84 times by adopting four electrodes compared to melting under the configuration of a single electrode with the same cross-section. The proposed numerical model provides a reference for designing and predicting LHTS performance with EHD.

Impact of Sustained Supply Voltage Magnitude on Consumer Appliance Behaviour

Voltage rise caused by high levels of distributed generation is manifesting as voltage regulation challenges for many electricity network service providers. In this environment it would be ideal to reduce supply voltage magnitudes, however, many network operators are hesitant to do so due to concerns related to consumer appliance performance at reduced supply voltage magnitudes. Voltage regulation requirements are defined by network standards and network service providers must ensure voltages remain within specified limits. Through an evaluation of domestic appliance performance when supplied at various voltage magnitudes, this paper examines the impact of varying voltage levels on residential appliances. Equipment energy demand, operation and actuation were monitored for each applied voltage magnitude. While no equipment failures were recorded, appliance behaviour varied significantly with applied voltage magnitude. Individual appliance conservation voltage reduction (CVR) factors have also been established. The results highlight the importance of good voltage regulation and provide substantiated appliance performance figures for future studies. The outcomes of this paper allow electricity network service providers to understand the implications of supply voltage magnitude on domestic appliance performance, whether it be understating of the impact of higher voltage magnitudes caused by distributed generation or implications of reducing voltage magnitudes to provide headroom for distributed generation integration.

Preliminary Evaluation of the Impact of Sustained Overvoltage on Low Voltage Electronics-Based Equipment

Low voltage devices connected to public electricity supply networks can be subjected to a wide range of voltage quality, including sustained overvoltage. Assessing the impact of sustained overvoltage on devices connected to the distribution network is important in determining the appropriate variance of standard voltage levels without unduly impacting the utility and customers from a technical and economic perspective. Therefore, a clear understanding of the impact that sustained overvoltage has on the lifetime of the connected equipment is a necessary task. This paper investigates the impact of sustained overvoltage through a series of accelerated-life testing experiments on a custom designed test device representative of a common interface between the power supply and distribution network, a switch mode power supply. The switch mode power supply with combined rectifier and filtering capacitor represents one of the most common front ends of LV equipment in modern appliances, and the work here concentrates on the impact of overvoltage on capacitor ageing. The results of the testing indicate that there is an accelerated ageing impact correlated with the applied voltage magnitude. Furthermore, analysis shows that mismatches between appliance voltage rating and sustained network voltage, leading to accelerated ageing, may result in premature device failure without the consumer being aware of the root cause.

Study on the discrete dielectrophoresis for particle-cell separation.

This paper presents the application of the discrete dielectrophoretic force to separate polystyrene particles from red blood cells. The separation process employs a simple microfluidic device that is composed of interdigitated electrodes and a microchannel. The discrete dielectrophoretic force is generated by adjusting the duty cycle of the applied voltage. The electrodes make a tilt angle with the microchannel to change the moving direction of the red blood cells. By adjusting the voltage magnitude and duty cycle, we investigate the deflection of red blood cells and the variation of cell velocity along electrode edge under positive dielectrophoresis. The experiments with polystyrene particles show that the enrichment of the particles is greater than 150 times. The maximum separation efficiency is 97% for particle-to-cell number ratio equal to 1:2000 in the sample having high cell concentration. Using the appropriate applied voltage magnitude and duty cycle, the discrete dielectrophoretic force can prevent the clogging of microchannel while successfully separating the particles from the cells with high enrichment and efficiency. The proposed principle can be readily applied to dielectrophoresis-based devices for biomedical sample preparation or diagnosis such as the separation of rare or infected cells from a blood sample.

Identification and localisation of incipient discharges in transformer insulation adopting UHF technique

Incipient discharges formed in natural ester oil due to corona activity, surface discharges and particle movement were investigated using UHF technique. When the applied voltage magnitude is increased, on the inception of discharges, the peak to peak magnitude of the voltage of the UHF signal formed also increases. After certain applied voltage magnitude increase, if it is reduced, the magnitude of UHF signal formed is much higher than the magnitude of the signal formed when the voltage is increased. This phenomenon is observed with all the three types of discharges. Cross Recurrence plot (CRP) can be effectively used to determine the Time Difference Of Arrival (TDOA) of UHF signals. Self-similarity Recurrence Quantification Analysis (RQA) parameter is found to be more suitable technique to estimate the TDOA of UHF signals. CRP method is used to estimate TDOA correctly, even with low signal to noise ratio and it is found to be superior to Cross-correlation technique in estimating the TDOA. Estimated TDOA of UHF signals are validated and incipient discharge source is localized by adopting the non-iterative technique.

Determining potential capacity gains when repurposing MVAC cables for DC power transportation

Due to the changing and growing network, operators are looking at more creative and economic ways to reinforce power transportation paths. One such way, being researched by the DNV GL led FLINK project, is to use existing AC cables as flexible DC-links in the medium voltage level. To determine the capacity gain from switching to DC, one must consider many assumptions. The most influential assumption being the increase in applied voltage magnitude. There is, however, a lack of practical research in MVDC. Some assumptions do not scale directly from higher voltages. For example skin and proximity effects may be negligible. Depending on the assumptions made, the capacity gain can range between -50% to >177%. This paper explores the assumptions used to determine capacity gained by MVDC.

Regeneration of Sooty Surface Using Nanosecond Pulsed Dielectric Barrier Discharge

In this paper, the regeneration of sooty surface by using nanosecond pulsed surface dielectric barrier discharge type reactor is investigated experimentally. The goal is to characterize the regeneration process as a function of the applied voltage magnitude and pulse polarity. The reactor is composed of two electrodes separated by a dielectric and are arranged asymmetrically. The power supply system provides high voltage pulses with the following characteristics: voltage up to ±10 kV; rise and decay time less than 50 ns; and a frequency of 2 kHz. The main results show that the regeneration performance increases with the applied voltage magnitude and the duration of treatment. Furthermore, depending on the polarity and the magnitude of the applied voltage pulse, the cleaned surface area can be either more uniform along the active electrode (negative pulses) or extended on the dielectric surface (positive pulses). The regeneration mechanism remains not very well understood, but it seems that the soot particle size is reduced mainly due to the interaction with ozone molecules and oxygen radicals generated by the discharge.

Electrical model of dielectric barrier discharge homogenous and filamentary modes

This work proposes an electrical model that combines homogeneous and filamentary modes of an atmospheric pressure dielectric barrier discharge cell. A voltage controlled electric current source has been utilized to implement the power law equation that represents the homogeneous discharge mode, which starts when the gas breakdown voltage is reached. The filamentary mode implies the emergence of electric current conducting channels (microdischarges), to add this phenomenon an RC circuit commutated by an ideal switch has been proposed. The switch activation occurs at a higher voltage level than the gas breakdown voltage because it is necessary to impose a huge electric field that contributes to the appearance of streamers. The model allows the estimation of several electric parameters inside the reactor that cannot be measured. Also, it is possible to appreciate the modes of the DBD depending on the applied voltage magnitude. Finally, it has been recognized a good agreement between simulation outcomes and experimental results.

LIF diagnostics of hydroxyl radical in a methanol containing atmospheric-pressure plasma jet**Project supported by the National Natural Science Foundation of China (Grant Nos. 11465013 and 11375041), the Natural Science Foundation of Jiangxi Province, China (Grant Nos. 20151BAB212012 and 20161BAB201013), and the International Science and Technology Cooperation Program of China (Grant No. 2015DFA61800).

In this paper, a pulsed-dc CH3OH/Ar plasma jet generated at atmospheric pressure is studied by laser-induced fluorescence (LIF) and optical emission spectroscopy (OES). A gas–liquid bubbler system is proposed to introduce the methanol vapor into the argon gas, and the CH3OH/Ar volume ratio is kept constant at about 0.1%. Discharge occurs in a 6-mm needle-to-ring gap in an atmospheric-pressure CH3OH/Ar mixture. The space-resolved distributions of OH LIF inside and outside the nozzle exhibit distinctly different behaviors. And, different production mechanisms of OH radicals in the needle-to-ring discharge gap and afterglow of plasma jet are discussed. Besides, the optical emission lines of carbonaceous species, such as CH, CN, and C2 radicals, are identified in the CH3OH/Ar plasma jet. Finally, the influences of operating parameters (applied voltage magnitude, pulse frequency, pulsewidth) on the OH radical density are also presented and analyzed.

Separation by nanoparticles plasmonic resonance with low stress in microfluidics channel (analytical and design).

In this study, nanoparticles near-field plasmonic resonance is used to improve the traditional cell separation main outputs such as viability and efficiency. The live cells viability is severely depend on stresses, which are applied on cells in the microfluidics channel. Hence, for improving the cell viability, the enforced stresses inside of the structure should be declined. The major factors of the enforced stresses are related to the electric field non-uniformity, which are attributed to the hurdles and applied voltage magnitude. Therefore, in this study, a new structure is presented and thereby, the magnitude of the applied stresses on live cells is minimised which is contributed to the decreasing the non-uniformity strength of channel. It should be noted that in the new structure two arrays of nanoparticles were used to produce a short range and localised non-uniform electrical field because of their near-field plasmonic resonance. Hence, the enforced stress on the live cell severely decreased at the far-field and confined at the small section of the channel. It is due to, the near-field plasmonic amplitude is dramatically disappeared by increasing distance, hence, the cells far from the nanoparticles will be endured the low level but effective amount of the optical force.

Electric Effects on the Pre-Mixing Process in DBD Assisted Combustions

A method of pre-mixing process augmentation for fuel combustion using dielectric barrier discharges (DBD) is presented. The mixing process of fuel and air can be augmented by the edge electric field of the electrodes because its transverse component will exert an electric force on the charge particles generated by DBD. The experimental results show that the combustion can be drastically influenced by this augmentation of pre-mixing process. A hollow flame caused by non-sufficient mixing, in which the air flow velocity is much larger than that of fuel gas, is used to demonstrate this kind of augmentation effects. Once the discharge is ignited, the hollow region in flame will gradually disappear. And further, the flame can propagate backward into the quartz tube. In this paper, the dependences of this kind of augmentation on the applied voltage magnitude and on the distance d from the electrodes to mixing region are examined. The critical voltages for hollow elimination and onset of backward propagation of flame are measured. The augmentation effects will vanish once the value of d exceeds 2cm, the hollow flame can not be changed even the applied voltage is very high.

Factors of influence on surface erosion of epoxy resin exposed to electrical discharges

This paper investigates the influence of electrical as well as environmental stresses on surface erosion of polymeric materials used in high voltage insulation. The analyzed electrical stresses are applied voltage magnitude and frequency; whereas the environmental stresses of concern are temperature and humidity of air above sample surface. Suitable electrode arrangement is chosen in order to produce measurable erosion and guarantee the control of the analyzed stressing factors. Discharge intensity is defined by two parameters; total discharge energy and cumulative charge; whereas surface erosion severity is characterized by three quantities; surface eroded area, eroded volume and maximum erosion depth. Surface characteristics are obtained by a laser profilometer. From the obtained results a dependence of erosion severity on these stressing factors can be proven. A strong correlation between discharge intensity and material surface erosion is concluded.

The Effect of Magnitude and Shape of Applied Voltage on the Partial Discharge Behavior in Cylindrical Cavity within a Dielectric Material

One of the important phenomena which is important in equipment when they are under high voltage stress is Partial discharge (PD). Partial discharge measurement is commonly used to evaluate the performance of the insulation in high voltage system. Modeling of the discharge in insulation can give a better understanding of this important phenomenon. A cavity within a dielectric material is a highly stressed area and the ideal place for starting partial discharge and breakdown. The applied voltage is one of the important factors that PD activity is influenced by that. Previous studies have considered the behavior of PD activity in a spherical cavity at 50Hz of sinusoidal applied voltage. However, still not so much work on the simulation of the PD activity in the cavity under different condition. Also, there is little data are available on the effect of parameters on the PD activity. This paper describes the behavior of PD activity as a function of applied voltage in a cylindrical cavity within a homogeneous dielectric. COMSOL and MATLAB software were used to carry out the simulation based on the finite element method (FEM). The number of PDs per cycle changed with different applied voltage so the highest number of PD at 20kV and the lowest value at 8kV. The maximum PD magnitude is raised from 1200pC at 8kV to 2400pC at 20kV applied voltage. The number of PD is most prevalent for sinusoidal followed by triangular waveform and then sawtooth. Comparison of the simulation results and experimental results are in good agreement. The result can help the researcher to understand more about the characteristics and behavior of partial discharge. Which may help the insulation diagnostic testing or condition monitoring.

On OH Density of an Atmospheric Pressure Plasma Jet by Laser-Induced Fluorescence

For room-temperature atmospheric pressure plasma jets (RT-APPJs), because of the gas flow, the OH density at a given position is different from the case without the gas flow. In this paper, an OH density decay model, which includes the main loss processes of OH and gas flow effect, is present. Based on the model, the simulation results have a very good agreement with the OH decay behavior measured by laser-induced fluorescence. The absolute OH density of the RT-APPJ is obtained when the best fit is achieved, which is about $2.4\times 10^{13}~{\rm cm}^{-3}$ at 5 mm away from the plasma jet nozzle and 1 $\mu{\rm s}$ after the discharge. In addition, to control the OH density, the effect of voltage polarity, applied voltage magnitude, pulse frequency, pulsewidth on the OH density is also investigated and discussed.

Understanding surface discharge activity in copper sulphide diffused oil impregnated pressboard under AC voltages

The surface discharge injected current were measured by using High Frequency Current Transformer (HFCT). It is observed that the rise time of the current pulse is about 800ps. In addition, the rise time of the current pulses has not altered in copper sulphide (CuS) diffused Oil Impregnated Pressboard (OIP) material, but the width of the current signal has increased with the increase in the amount of copper sulphide diffusion into the pressboard. It is confirmed that the injected current pulse radiates Ultra High Frequency (UHF) signal and the dominant frequency of the UHF signal formed due to the surface discharge injected current is about 0.9 GHz. The characteristic frequency contents of the UHF signal formed due to surface discharge activity is the same with the virgin and copper sulphide diffused pressboard material. The surface discharge inception voltage is high with the virgin specimen compared with copper sulphide diffused oil impregnated paper insulating material and is the same irrespective of the amount of diffusion of copper sulphide to it. The Phase Resolved Partial Discharge (PRPD) analysis indicates that at the point of surface discharge inception, the discharge occurs at the peak of the applied AC voltage and when the applied voltage magnitude is increased, the discharge occurs at the rising portion of the applied AC voltage. The characteristics of the surface discharges formed are the same with the copper sulphide diffused oil impregnated pressboard material. It is noticed that with increase in ageing time, a reduction in partial discharge magnitude is observed. Attenuated total reflectance Fourier transform infra-red spectroscopy (ATR-FTIR) analysis was carried out to understand the characteristic changes that occur in the degraded zone formed due to surface discharges. The measurement of surface charge indicates that ageing of oil impregnated paper material increases the surface charge accumulation. Energy Dispersive Spectroscopy (EDS) confirms the presence of copper and sulphur in the aged Oil Impregnated Pressboard material. The Atomic Absorption Spectroscopy (AAS) results indicate that the amount of copper content in pressboard material have increased with ageing time.

Analysis of surface discharge activity in epoxy nanocomposites in liquid nitrogen under AC voltage

A marginal increase in surface discharge inception voltage is observed with increase in percentage of clay in epoxy nanocomposites in liquid nitrogen medium. The flashover voltage of epoxy nanocomposites increases with increase in percentage of clay in epoxy resin up to 3 wt% and above which a slight reduction is observed but much higher than the pure epoxy resin.The intercalated and exfoliated properties were analyzed through TEM studies.Contact angle marginally vary with percentage of clay in epoxy resin. The surface variations of epoxy nanocomposites analysed through surface roughness measurement and by attenuated total reflectance Fourier transform infra-red spectroscopy (ATR-FTIR).The rise time of injected current pulse due to surface discharge process is measured to be 800 ps. The UHF signal generated due to surface discharge (at the point of inception and propagation) formation on epoxy resin with different percentage of clay in liquid nitrogen medium have dominant frequency near 1 GHz. The PRPD pattern obtained at the point of inception of surface discharges, the magnitude of discharges is nearly same in both half cycle of the applied AC voltage. Surface discharge occurs in the rising part of the applied AC voltage. When the applied voltage magnitude is increased, the higher magnitude discharges occurs at the positive half cycle of the applied AC voltage.

Effects of Impulse Voltage Polarity, Peak Amplitude, and Rise Time on Streamers Initiated From a Needle Electrode in Transformer Oil

An electrothermal hydrodynamic model is presented to evaluate effects of the applied lightning impulse voltage parameters such as polarity, magnitude, and rise time on the initiation and propagation of the streamers formed in an IEC defined needle-sphere electrode geometry filled with transformer oil. Instantaneous velocity, column diameter, head curvature, maximum electric field, and the volume charge density have been investigated as the main characteristics of the streamer. Modeling results indicate that greater applied voltage peak amplitudes form streamers with higher velocity, greater head curvatures, and thicker columns. The bushy negative streamers usually initiate at almost twice the applied voltage magnitude and propagate slower than filamentary positive streamers. Results also show that in transformer oil at the same impulse voltage peak amplitude, shorter rise times create thicker positive and negative streamers.

Repetitively pulsed atmospheric pressure discharge treatment of rough polymer surfaces: I. Humid air discharges

Plasmas generated at atmospheric pressure are used to functionalize the surfaces of polymers by creating new surface-resident chemical groups. The polymers used in textiles and biomedical applications often have non-planar surfaces whose functionalization requires penetration of plasma generated species into sometimes complex surface features. In this regard, the atmospheric pressure plasma treatment of a rough polypropylene surface was computationally investigated using a two-dimensional plasma hydrodynamics model integrated with a surface kinetics model. Repetitively pulsed discharges produced in a dielectric barrier–corona configuration in humid air were considered to affix O. Macroscopic non-uniformities in treatment result from the spatial variations in radical densities which depend on the polarity of the discharge. Microscopic non-uniformities arise due to the higher reactivity of plasma produced species, such as OH radicals, which are consumed before they can diffuse deeper into surface features. The consequences of applied voltage magnitude and polarity, and the relative humidity on discharge dynamics and radical generation leading to surface functionalization, are discussed.