Ground Electrode Research Articles

Sake pasteurization using a novel continuous flow pulsed electric reactor with cooling system

A pulsed electric field (PEF) reactor that has two flow paths separated by a membrane was constructed for sake pasteurization. The treatment and cooling solutions were supplied to the flow paths in contact with a ground electrode and a high-voltage electrode, respectively. The characteristics of microbial inactivation in the continuous operation of the novel PEF treatment were investigated using the NaCl solution containing Escherichia coli as the model treatment solution and the NaCl solution as the cooling solution. The effects of the flow rate of the cooling and treatment solutions on the microbial inactivation efficiency and temperature of the treatment solution were investigated. In the PEF treatment at two different treatment solution flow rates, the lower flow rate could achieve effective inactivation, and the temperatures of the treatment solutions after PEF treatment were almost the same. Increasing the cooling solution flow rate was effective in preventing the increase in the temperature of the treatment solution during PEF treatment, but the temperature of the treatment solution remained at around 28 °C when the flow rate was increased. The effects of the electrical conductivity of the cooling solution on the microbial inactivation efficiency and temperature of the treatment solution were also investigated. It was demonstrated that increasing the electrical conductivity of the cooling solution increased not only the inactivation efficiency but also the temperature of the treatment solution after the PEF treatment, and determining the appropriate electrical conductivity of the cooling solution is essential for effective pasteurization. Finally, pasteurization of sake with the reactor using the obtained appropriate electrical conductivity and flow rate of cooling solution was demonstrated. The sake yeast and Lactobacillus homohiochii in sake were fully inactivated by PEF treatment, and the temperature of sake after PEF treatment was maintained below 40 °C. • Cooling through a membrane was effective in controlling the temperature of sake. • The electrical conductivity of the cooling solution affected the inactivation efficiency. • Microorganisms in sake were completely inactivated by PEF treatment. • The temperature of sake after pasteurization by PEF was below 40 °C.

Ultrasonic unilateral double-position excitation lamb wave defect detection and quantification method for ground electrode of transmission tower

The power transmission tower’s ground electrode defect will affect its normal current dispersion function and threaten the power system’s safe and stable operation and even personal safety. Aiming at the problem that the buried grounding grid is difficult to be detected, this paper proposes a method for identifying the ground electrode defects of transmission towers based on single-side multi-point excited ultrasonic guided waves. The geometric model, ultrasonic excitation model, and physical model are established, and the feasibility of ultrasonic guided wave detection is verified through the simulation and experiment. In actual inspection, it is equally important to determine the specific location of the defect. Therefore, a multi-point excitation method is proposed to determine the defect’s actual position by combining the ultrasonic guided wave signals at different excitation positions. Besides, the precise quantification of flat steel grounding electrode defects is achieved through the feature extraction-neural network method. Field test results show that, compared with the commercial double-sided excitation transducer, the single-sided excitation transducer proposed in this paper has a lower defect quantization error in defect quantification. The average quantization error is reduced by approximately 76%.

Simulation and Structure Optimization of Grounding Circuit Model for Power Transmission Line Tower

The lightning current dispersion process through the steel bar inside the concrete pile foundation of the transmission line tower is impeded by the high concrete resistivity. In order to improve the current dispersion performance of the pile foundation, this paper proposes a method to place flexible graphite grounding electrode along the shaft wall of the tower foundation and verified its feasibility. Both single-pile and four-pile foundations are applied to build vertical grounding models of transmission line tower with three different grounding structures, respectively, including flexible graphite grounding line, flexible graphite grounding fabric and combined graphite electrode. The effect of three grounding structures on the current dispersion and resistance reduction is studied by finite-element method. Simulation results indicate that by applying the above three grounding structures on the vertical pile foundation can significantly improve the current density distribution of the excavated pile foundation and reduce the grounding resistance. When the grounding resistance is [Formula: see text], the resistance reduction efficiencies of the above three methods can reach 48.56%, 53.86% and 54.53%, respectively. Considering the limited construction area, this paper compares the foundation that is placed combined graphite grounding electrode with square-ray grounding grid, and it can be seen that by placing vertical grounding electrode can save the land area of 295.99[Formula: see text]m2. This paper can provide reference for the design of excavation pile foundation grounding structure under limited construction area.

Study and Numerical Simulation of Negative and Positive Corona Discharge: A Review

Two models to describe the phenomenon of corona discharge are presented: the first is known as the plasma model which with plasma chemistry defines the volumetric and surface reactions among charge carriers such as electrons, positive, and negative ions. This model uses Poisson's equation and a formulation of the space-charge density to calculate the electric field necessary to solve the species transport equations. Besides, only the plasma model determines the density of the charge carriers. The second is a simplified model which describes the corona discharge in terms of current conservation coupled with Poisson's equation. This model does not have any connection with the attributes of plasma chemistry. Both models propose solutions for the electric potential and space charge density distribution from the corona electrode to the ground electrode.

Efficient direction-independent fog harvesting using a corona discharge device with a multi-electrode structure

Efficient collection of water from fog can effectively alleviate the problem of water shortages in foggy but water-scarce areas, such as deserts, islands and so on. Unlike inefficient fog meshes, corona discharge can charge water droplets and further enhance the water-collecting effect. This study proposes a novel multi-electrode collecting structure that can achieve efficient and direction-independent water collection from fog. The multi-electrode structure consists of three parts: a charging electrode, an intercepting electrode and a ground electrode. Four types of water-collecting structures are compared experimentally, and the collection rates from a traditional fog mesh, a wire-mesh electrode with fog coming from a high-voltage electrode, a wire-mesh electrode with fog coming from a ground electrode and a multi-electrode structure are 2–3 g h−1, 100–120 g h−1, 60–80 g h−1 and 200–220 g h−1, respectively. The collection rate of the multi-electrode structure is 100‒150 times that of a traditional fog mesh and 2–4 times that of a wire-mesh electrode. These results demonstrate the superiority of the multi-electrode structure in fog collection. In addition, the motion equation of charged droplets in an electric field is also derived, and the optimization strategy of electrode spacing is also discussed. This structure can be applied not only to fog collection, but also to air purification, factory waste gas treatment and other fields.

Streamer-to-spark transitions in deionized water: unsymmetrical structure and two-stage model

This letter focuses on the streamer-to-spark transitions generated by microsecond pulsed discharges (±20 kV of amplitude, 150 μs of pulse width) in deionized water to provide a quantitative insight into the underwater breakdown process. The discharge channel during underwater electrical breakdown is generally considered as a homogenous blackbody radiator by the arc model. However, we report an unsymmetrical structure of negative breakdown channel in water which shows great discrepancy from the frequently observed uniform structure. An improved two-stage analytical model is proposed to quantitatively estimate the parameter variations of the discharge channels, e.g. radius, temperature, pressure. The calculated results show that the discrepancy in parameters of different parts of negative discharge channel is tremendous. Specifically, during negative electrical breakdown, the region of discharge channel near ground electrode owns greatest values in characteristic parameters (e.g. T max = 22 300 K, P max = 0.145 GPa and v max = 219 m s−1), which are far above the counterparts of main body of channel. By introducing field ionization and impact ionization mechanisms during the propagation of the streamer, we explain the rapid expansion of positive discharge channel and the regions of negative channel near the needle tip as well as the ground electrode. Besides, the deposited homocharges at the gas–liquid interface weaken the ionizations in main body of negative breakdown channel, and hence causing the formation of the unsymmetrical structure.

Electrohydrodynamic and heat transfer characteristics of a planar ionic wind generator with flat electrodes

• Two corona discharges with different polarities are produced simultaneously. • The minimum discharge gap to maintain a stable corona discharge is determined. • The intensity and direction of the generated ionic wind is revealed. • The relationship between the heat transfer enhancement ratio and power consumption is established. In this study, a planar ionic wind generator with two flat electrodes was investigated numerically and experimentally to reveal its electrohydrodynamic and heat transfer characteristics. The multi-physical characteristics, including the discharge process, movement of electrons, positive ions, and negative ions, as well as the formation of ionic wind and its flow characteristics were simulated numerically. It was found that two corona discharges with different polarities were produced simultaneously when a high voltage was applied between the emitting and the ground electrodes. The intensity and direction of ionic wind produced by planar ionic wind generator was revealed. The effects of discharge gap, flat electrode thickness, and discharge polarity on the heat transfer characteristics and power consumption of the planar ionic wind generator were also investigated experimentally. The minimum discharge gap to maintain a stable corona discharge is determined. A better heat dissipation capacity of the planar ionic wind generator can be obtained with a larger electrode gap, and the optimized ionic wind generator can reduce the surface temperature of a 2.05 W powered heat source by more than 46 °C compared with natural cooling. The maximum heat transfer coefficient is 35 W∙m −2 ∙K −1 . This study can provide a theoretical guidance for the application of planar ionic wind generators to highly compact electronic devices.

Analysis of Lightning Strike Effects on Crude Oil Storage Tank Protection System at PT. Pertamina Balongan Indramayu

Main Gathering Station (MGS) Balongan Pertamina EP Asset 3 OGT is an industry engaged in the oil and gas sector by always paying attention to QHSE (Quality, Health, Safety and Environment) aspects. This industry is a national vital object categorized as a zone 1 and zone 2 hazardous area. There is a source of danger that has the potential to cause damage to equipment and people. The electrical installation used is a lightning protection system with reference to the NFPA 780-2017 standard concerning the Standard for the Installation of Lightning Protection Systems. The rolling sphere method is used to calculate the need for a lightning protection system. To calculate the need for a grounding electrode, a rod electrode grounding system is used. Construction MGS Balongan (Hazardous Construction) has a value of direct lightning strike frequency (Nd) of 0.03 lightning strikes per year with an equivalent area of building lightning strikes (Ae) of 1082.95 m2. The value (Ng) of the intensity of lightning strikes to the ground is 27.6 lightning strikes per km2 per year, the protection level is level II with a radius of 30 meters and the earth resistance value is 0.344 Ω. The design value of this calculation is in accordance with PUIL 2011 standards, namely it must be below 5Ω for the overall value of earth resistance.

Effect of DC Deep-Well Ground Electrode Materials on gas Evolution

The uniqueness of DC deep-well ground electrodes (DWGEs) lies in their low area requirements. However, the gas produced by DWGEs during electrolysis may cause more severe exhaust problems than those caused by conventional electrodes. To investigate the influence of different electrode materials on the gas evolution of DWGEs, an innovative U-shaped experimental platform is proposed for the separate collection of cathode and anode gases. The metal–electrolyte contact interface in a DWGE project was simulated, and gas evolution experiments were performed on three typical ground electrode materials. The gas evolution rates of the electrode materials when operate as cathodes and anodes were obtained. Polarization curves were used to compare the corrosion rates of the three materials and evaluate the effects of these rates on the gas evolution rates of the materials. The results revealed that when operated as anodes, mixed metal oxide (MMO) and high-silicon cast iron produced oxygen, whereas carbon steel did not. Furthermore, the evolution of O₂ in MMO was faster than that in high-silicon cast iron. When operated as cathodes, the three materials generated hydrogen, and carbon steel exhibited the slowest H₂ evolution rate. The current distribution in the different gas evolution processes was summarized. The supplied current was used as the reaction current of metal corrosion and for gas generation. Under the same current, quicker corrosion corresponded to a lower amount of gas evolution for a material.

접지시스템 최적 설계 사례 연구

The grounding system is a power system facility that establishes safety in the work place by decreasing the induced voltage by burying ground conductors and electrodes in the ground. The most important variable affecting the type and size of the grounding system is the soil resistivity. In order to obtain resonable and effective soil resistivity, necessary and sufficient field measurements as well as selection of a suitable soil model are essentially required. The grounding system is implemented in various ways, such as the selection of ground conductors and electrodes, as well as the mesh configuration of a ground grid and its burial depth. Economical factors such as material cost and construction cost of the grounding system are also required as variables for optimization. This paper is a case study of designing and reviewing a grounding system that reflects efficiency and economic feasibility using the grounding grid design and analysis software.

Three-dimensional multilayer concentric bipolar electrodes restrict spatial activation in optic nerve stimulation

Objective. Intraneural nerve interfaces often operate in a monopolar configuration with a common and distant ground electrode. This configuration leads to a wide spreading of the electric field. Therefore, this approach is suboptimal for intraneural nerve interfaces when selective stimulation is required. Approach. We designed a multilayer electrode array embedding three-dimensional concentric bipolar (CB) electrodes. First, we validated the higher stimulation selectivity of this new electrode array compared to classical monopolar stimulation using simulations. Next, we compared them in-vivo by intraneural stimulation of the rabbit optic nerve and recording evoked potentials in the primary visual cortex. Main results. Simulations showed that three-dimensional CB electrodes provide a high localisation of the electric field in the tissue so that electrodes are electrically independent even for high electrode density. Experiments in-vivo highlighted that this configuration restricts spatial activation in the visual cortex due to the fewer fibres activated by the electric stimulus in the nerve. Significance. Highly focused electric stimulation is crucial to achieving high selectivity in fibre activation. The multilayer array embedding three-dimensional CB electrodes improves selectivity in optic nerve stimulation. This approach is suitable for other neural applications, including bioelectronic medicine.

Cold plasma treatment of porous scaffolds: Design principles

AbstractThree‐dimensional porous scaffolds have the potential to revolutionize a number of fields, including stem cell research, biomedical implants, tissue engineering, and regeneration, as well as energy technologies, filtration, and sensing. The ability to precisely engineer their surface properties is paramount to successful and enduring application. Plasma treatments promise to deliver homogeneous surfaces with tailored characteristics while generating few by‐products and not relying on the diffusion of liquids into a porous network. However, forming plasma inside complex interconnected pores is a significant challenge and requires much parameter fine‐tuning. This study uses numerical modeling to investigate key parameters which affect plasma breakdown and makes practical recommendations for achieving treatment homogeneity. We consider a dielectric barrier discharge (DBD) system, where nitrogen gas flows through a glass tube containing a porous scaffold, which is surrounded by a cylindrical electrode, with ground electrodes at either end of the tube. The parameters investigated include the scaffolds' pore size and porosity as well as electrode size and position. The results showed that homogeneous treatment is achieved by avoiding alternative breakdown pathways such as a poor seal between the scaffold and the glass containment tube, using a narrow supply electrode centered at the scaffold, and positioning ground electrodes as close as possible to the supply electrode without arcing. This strategy maximizes the electric field strength at a given voltage, allowing for higher pressures to be used, which in turn give a more homogeneous mean free path inside the pores.

Assessment and mitigation of DC bias risk in power grids at provincial boundaries

With the wide application of high voltage/ultra-high voltage (HV/UHV) DC transmission technology, the impact of DC grounding electrode location selection on the surrounding power grid has become increasingly prominent, especially the problem of DC bias hazard caused by DC grounding electrodes at provincial grid boundaries needs to be solved urgently. This paper studies the assessment and prevention of trans-regional DC bias risk, and proposes an inversion method of earth resistivity model based on the measured data of neutral current in the provincial boundary area. Firstly, the DC bias risk of provincial boundary power grid is simulated and calculated, and the influence of reasonable selection of earth model on the accuracy of risk assessment results is explained. Based on the classical Fletcher-Reeves conjugate gradient method and the measured neutral current data, a reduced-order inversion method for the earth resistivity parameters of the provincial boundary power grid is proposed. On this basis, a set of DC bias risk control scheme is formulated for the actual project of Gannan power grid. Finally, the feasibility of the scheme is verified by simulation and measured data.

Single-ended protection method of MMC-HVDC transmission line based on random matrix theory

The physical electrical boundary at both ends of the MMC-HVDC transmission line is composed of smoothing reactors and has a high-frequency blocking effect. This behavior causes the time-domain characteristics of the initial part of the polar line current waveform to be significantly different under the internal and external MMC-HVDC line faults, and can lead to two different fault modes. However, the operation of the DC line traveling wave protection with du/dt as the core can be easily affected in the presence of high resistance (HR). Furthermore, it is difficult to set the criterion setting value. To solve the aforementioned problems, this paper proposes a line single-ended protection method based on the random matrix theory (RMT). First, the difference between the internal and external line current fault modes is analyzed. Second, the physical characteristics of the two modal differences in the RMT are analyzed. Third, the single Ring Law is used to achieve visualization, and mutation energy is used as the starting criterion. The fixed values of the spectral radius and Euclidean distance of the spectral radius are utilized as the identification criteria for the internal and external line faults. Furthermore, the set value of the spectral radius is used as the fault selection criterion. Last, a 77-level bipolar MMC-HVDC system grounded through the grounding electrode lead is built in RTDS to verify the adaptability of the proposed method to HR and noise. The results show that the method can quickly and reliably detect DC line faults and fault poles under different fault locations and different transition resistances, and the RMT protection can be further improved with the increasing number of fault samples.

Removal of Mist Particles by a Two-Stage Electrostatic Precipitator Featuring Plastic Plate Electrodes

To reduce corrosion, cost, and weight, we developed a nonmetallic, two-stage electrostatic precipitator (ESP) using electrodes fabricated from carbon ink and polyethylene terephthalate (a plastic), rather than expensive corrosion-resistant metals. Five collection modules were manufactured; we varied the materials used to fabricate the high-voltage and ground electrodes. The plate-type electrodes of the collection module were made of stainless steel, carbon-coated plastic (CPC), or plastic-coated carbon (PCP). Particle removal performance was investigated by the voltages of the precharger and collection modules, the particle diameter, the airflow rate, and the particle collection area. The particles were an oil mist. The electrode material had little effect on particle removal performance. The experimental performances of two-stage ESPs featuring plastic and carbon plate electrodes met the theoretical efficiencies predicted by the Deutsch equation and Cochet charging theory. Although fluttering developed when the flow velocity exceeded 2 m/s over CPC electrodes, the use of PCP electrodes (the rigidity of which was reinforced by the plastic coatings) eliminated fluttering. Moreover, in an extremely humid condition where the water vapor continuously condensed into water droplets, the polyethylene terephthalate film of the PCP electrode ensured stable operation without spark regardless of humidity or water droplets on the surface. In summary, plastic electrodes were light and economical, while affording high removal efficiencies similar to the removal efficiencies of metals. Moreover, the PCP electrode plastic coating protected the carbon ink from abrasion and corrosion.

Application of Geo-electrical Method in Preliminary Study for Earth Electrode Site Selection

Electrical power transmission is usually done as high voltage transmission for efficiency. For that purpose, effective grounding is necessary especially at the location of the power transmission control center. To obtain a good connection to the ground, very conductive or low resistivity soil should be present up to an appropriate depth at the earth electrode site. In this paper we present the results of the geoelectrical survey performed in a candidate site in the southern part of South Sumatra province, Indonesia. The objective of this preliminary study is to delineate the most appropriate location for the grounding electrodes. Data acquisition for 2D resistivity tomography was done along several lines crossing the survey area. Low resistivity layer of 10 Ohm.m or less up to 50 m depth was found at the north-western sector of the area.

Numerical simulation of coaxial–coplanar dielectric-barrier discharge in atmospheric helium

A self-consistent two-dimensional fluid model is employed to investigate the coaxial–coplanar dielectric-barrier discharge (DBD) excited by the sinusoidal voltage in atmospheric helium. Simulation results show that there are two current pulses in the positive half cycle, but only one in the negative half cycle. The discharge is transformed from the Townsend-like mode, through the glow-like mode, and back to the Townsend-like mode in both the positive and negative half cycles, during which the electric field line exhibits an arc-shape profile due to the configuration of coaxial–coplanar electrodes. In the glow-like mode, the cathode fall is located near the inner edge of the ground electrode at the first positive current peak, but close to the outer edge of the ground electrode at the second positive current peak. At the negative current peak, the cathode fall is distributed near the outer edge of the high voltage electrode. Since the instantaneous anode and the instantaneous cathode are on the same side of the discharge space, the dielectric layer is simultaneously covered by positive and negative surface charges due to the movement of charged particles. It is also found that the surface charge density changes significantly on the dielectric layer facing the electrodes. A further study reveals that a stronger discharge always occurs in the central circular area and an alternately complementary discharge takes place in the periphery ring area in the positive half cycle due to the activator–inhibitor effect. This feature is helpful for producing uniform plasma in a whole cycle of DBD.

Study on the Interference Distribution Characteristics of the HVDC Grounding Electrode Current with Buried Pipelines Based on MoM and FEM

It is very important to calculate the interference of high voltage direct current (HVDC) grounding current with pipelines accurately and take proper protective measures to ensure energy transmission safety. There is still a lack of systematic research into related prediction methods that consider the nonlinear polarization on the interface between the soil and pipelines. In this paper, a methodology is proposed for calculating the coupling voltage and current on buried pipelines induced by grounding currents that accounts for nonlinear polarization based on the method of moments (MoM) and the finite element method (FEM). The validity of the proposed mathematical model is verified by a scale experiment. The interference distribution characteristics under different parameters are analyzed using the proposed method. The results show that the relationship between the maximum leakage current density and the electrode grounding current satisfy the linear function. The corrosion area becomes more concentrated as the grounding current increases. The corrosion area range increases substantially as the distance increases, whereas the influence degree decreases substantially. Both the maximum leakage current density and corrosion risk area are positively correlated with the soil resistivity.

Enhancing signals of microfluidic impedance cytometry through optimization of microelectrode array.

Microfluidic impedance cytometry shows a great value in biomedical diagnosis. However, the crosstalk between neighboring microelectrodes strongly weakens the impedance signal. Hereby, we demonstrate a novel microfluidic impedance cytometer consisted of sensing electrodes and ground electrodes (GNDs). The simulation reveals a signal enhancement by more than five times with GNDs compared to that without ones. We also found that the linear correlation between the impedance at a high frequency and that at a low frequency varies as microparticle size changes, which can be used for microparticle classification. The study can help with microelectrode optimization and signal processing for microfluidic impedance analysis.

A New Grounding Resistance Reduction Method for Wind Turbines by Grounding Grid Connection in Limited Areas

Restricted by cultivated land vegetation, road construction, and land acquisition compensation costs, the grounding electrode extension method is not applicable for grounding resistance reduction of some wind turbines in limited areas. A new grounding resistance reduction method is proposed and verified for wind turbines by connecting nearby wind turbine grounding grids. To study the efficiency of the proposed method, the grounding characteristics of connected grounding grids are calculated. Simulation results indicate that the grounding resistance of connected grounding grids is smaller than that of box extension grounding grids. The grounding characteristics of the grounding grid connection are affected by grounding current frequency and material parameters. The grounding grid connection increases the current dispersion area and reduces the ground potential rise of the grounding conductor.