High Voltage AC Power Research Articles

Proximative and Contrastive Study of Malachite Green Dye Degradation Using Microplasma Discharge With Postliminary Phytotoxicity Analysis

Array of microplasma jets has been produced in atmospheric conditions using a high-voltage ac power source for the degradation of malachite green (MG) dye in the aqueous solution. The effect of plasma forming gases (air, oxygen, and argon) on the degradation was analyzed by UV-Vis spectrophotometer, and the formation of hydrogen peroxide during plasma–water interaction was quantified. Oxygen plasma produced a relatively high amount of hydrogen peroxide than air and argon, leading to efficient degradation. Oxygen plasma medium exhibited 14.78% and 9.85% higher energy yield than air and argon plasma, respectively. Observation shows that the degradation of MG dye in the aqueous solution follows the first-order kinetics irrespective of plasma forming gases. Phytotoxicity of untreated and oxygen microplasma treated MG dye solution was examined with the germination of tomato seeds. The results illustrate that the toxicity of MG dye was considerably reduced with the microplasma discharge treatment, as it induced 17.4% higher germination percentage than control. The study delineates that oxygen microplasma is an effective, economic and eco-friendly tool for detoxification of huge amount of MG dye in the aqueous medium.

Germination enhancement of green bell pepper (Capsicum annuum L) by using non thermal argon plasma

An attempt to enhance the germination of green bell pepper has been tried by using dry processing non thermal (cold) argon plasma treatment. As an emerging non thermal technology, cold plasma could be used to give a pretreatment to a thermal-sensitive material, such as pretreatment to seeds of bell pepper prior to be planted in soil to understand the effect of this dry process during the germination period. In this experiment, the used argon plasma was generated by flowing argon gas with the rate of 2 L/min through a positively charged of stainless pipe at a distance of 15 mm from aluminum plate electrode. With an applied voltage of 9.8 kV (peak-to-peak) electrical energy from a high voltage AC power supply, argon plasma irradiation was employed to the bell pepper seeds for a predetermined period of time as pretreatment to the seeds during pre-planting. It was found that the temperature of the plasma never exceeded 35°C during the plasma irradiation to assure that no thermal damage occurred to the seeds. It was also confirmed from this study that by giving non thermal plasma treatment for 30 minutes to the seeds may enhance the germination of the bell pepper plants up to 90% in stem length and almost 2.5 times in root length compared to the pepper without treatment.

Corona discharge development and its application to eliminate microorganism in raw milk

Raw cow’s milk or fresh milk is a natural food with a complete nutrients which provide many benefits for human health. Raw milk also provides almost ideal media for various microorganisms to grow rapidly that can harm human digestion, or make damages the milk itself. In attempt to investigate an appropriate processing technology as an alternative of thermal pasteurization, we developed non thermal corona discharge to eliminate total number of various microorganisms in milk. The generated corona discharge used 7 pins to plate surface configuration. With a distance 15 mm between the electrodes, the applied voltage of 6.48 kV by a homemade high voltage AC power supply yields in corona discharge that has temperature lower than 30°C after 8 minutes operation. The time dependent effects of the implementation of this discharge to raw milk were carried out at time interval 2, 4 and 8 minutes. It was found that there was three different types of bacteria colony morphology in the microorganism population of raw milk. The microorganism counts were decrease for 2 and 4 min corona treatments. However, when the corona treatment was done in 8 min, the total number of microorganism increased significantly. Although the corona discharge shows the potential benefits in milk decontamination processing at low temperature, more detailed study should be carried out to confirm the suitable in real application including the nutrient composition before and after treatment.

Multiple-Objective Control Scheme for Input-Series–Output-Series LCL-Filtered Grid-Connected Inverter System

An input-series–output-series inverter system is suitable for the large-capacity high-voltage ac power applications. If such a combined system comprising a number of small-capacity inverters is utilized in the high-power grid-connected power generation to replace a single high-capacity inverter, the voltage stress of the module would be greatly reduced. Additionally, the reliability of the whole grid-connected system could be effectively heightened owning to its flexible assembled-connection architecture. The principal issues for this grid-connected combined system touch upon multiple control objectives, including power balance, high power factor of the grid current, suppression of LCL resonance spike, and redundant operation of the system. Above all, the control variables are attentively screened to obtain a concise scheme to achieve the first three fundamental demands. Furthermore, the control units are dispersed into each module and a hot-swap technique is proposed to actualize the last objective, acquiring the superior reliability of the system. Finally, a three-module prototype is fabricated and the experimental results verify the effectiveness of the proposed strategy.

Colorimetric Method for Discharge Status Diagnostics based on Optical Spectroscopy and Digital Images

Discharge is a process, which involves changes in multiple species, and it is important for researchers to be able to describe changes in discharge status holistically. In this study, we applied AC and DC high voltage power sources to a short-gap needle-plane device in an atmospheric environment. We propose two new corona diagnosis methods based on spectral data and visible images. The experimental results demonstrate that, in the RGB system, the proportion of the blue component in AC corona images has the characteristic of decrease-stable-increase with voltage, and the corresponding result of the spectra is stable-increase. In the XYZ system, the AC corona chromaticity coordinates of both images and spectra demonstrate a linear fitting result with the voltage, and the image results contain a retracement process, showing shows the increase-stable-decrease trend of chromaticity coordinates x and y, which correlates well with oscilloscope results. The difference between the image and spectra results indicates that, compared to the spectra, high-resolution visible images are more sensitive to imperceptible changes in colorimetry information. The change of DC corona colorimetry characteristics can illustrate the change in AC corona colorimetry characteristics. Additionally, the dominant wavelength is proven to reflect the discharge species, and can reflect the vibrational temperatures. To the best of our knowledge, this paper represents the first attempt to systematically introduce colorimetry theory into discharge images and spectra. We successfully obtained colorimetric indicators with the linearity and low-dimension characteristics, which correspond well with known physical parameters.

Design and Model of Series-Connected High-Voltage DC Multipliers

The generation of high dc voltages is necessary for feeding many technical applications and testing the insulation material of high-voltage dc transmission lines and ac power cables with long lengths. The article proposes a modular multiplier high-voltage dc generator with integrated Cockcroft-Walton (CW) circuits. In this new topology, CW circuits are connected in series to produce a high dc output voltage with low regulation factor (<; 2%) and a negligible ripple factor without the need for costly filters to produce a nearly constant output voltage. The modules are fed by low input ac voltage sources that have the same magnitude and frequency. Numerical simulations using MATLAB/Simulink confirm the viability of the proposed generator. The generator is finally validated by experimental tests on a kV-size prototype.

Study on corona discharge spatial structure and stages division based on visible digital image colorimetry information

Due to the progress in photoelectric detection techniques, visible light images provide more abundant spatial structure information, which facilitates the detection of the colorimetry distribution in discharge images. In this study, the 50Hz AC high voltage power source was applied to the 15 mm needle-plane gap under room temperature and atmospheric pressure. The discharge images in the time scale of seconds were obtained by a high resolution digital camera. Two kinds of colorimetry indicators based on RGB model and HSI model were used to reflect the spatial structure and the colorimetry variation of discharge areas. Our experimental results demonstrated the growth, suppression, and penetration of the filamentary discharge and reflected that the relative intensity of characteristic color varies with different voltages. According to the variation of colorimetry information, we divided the AC corona stages, and the stage division results of two models are well correlated. Oscilloscope electrical signals verify the reliability of the colorimetry result, and colorimetry information shows the advantage of overcoming the randomness of one single discharge pulse amplitude. The colorimetry information extracted from images can represent the statistical characteristics of a large number of discharges, helping to characterize the spatial structure of corona discharges and evaluate its status.

Определение наведенных напряжений, создаваемых трехфазными линиями электропередачи в особых режимах

The purpose of the paper is to develop a method of computer simulation of induced voltages generated by high-voltage power lines in the modes of open phase faults and asymmetric short circuits. The study uses the methods of determining electric power system modes in phase coordinates implemented in the software package Fazonord. Air lines for various purposes running along the routes of high-voltage AC power lines are subjected to electrical and magnetic influences. Therefore, dangerous voltages may appear on the disconnected lines when they are located remotely (100 m and more) from the influencing line. To determine the levels of the induced voltages the modes of 220 kV power lines located in parallel to the 10 kV line are simulated. Calculations of voltages induced on the adjacent line are performed for the following operation modes of a transmission line: symmetric open fault of the phases A, B and C, whereas A is with the simultaneous short circuit to earth of the single phase and two phase short circuits. Consideration of different grounding methods of the line subjected to the influence showed that under some conditions the levels of the induced voltages can exceed 11 kV. The proposed method of computer simulation of electric power system modes developed at the Irkutsk state Transport University allows to determine the conditions of electrical safety when working on power and communication lines located in the areas of electromagnetic effects. The procedure is versatile and allows determination of the induced voltages on the lines exposed to electromagnetic effects in different operating modes.

Coordinated Control of HVDC and HVAC Power Transmission Systems Integrating a Large Offshore Wind Farm

The development of efficient and reliable offshore electrical transmission infrastructure is a key factor in the proliferation of offshore wind farms (OWFs). Traditionally, high-voltage AC (HVAC) transmission has been used for OWFs. Recently, voltage-source-converter-based (VSC-based) high-voltage DC (VSC-HVDC) transmission technologies have also been considered due to their grid-forming capabilities. Diode-rectifier-based (DR-based) HVDC (DR-HVDC) transmission is also getting attention due to its increased reliability and reduced offshore platform footprint. Parallel operation of transmission systems using such technologies can be expected in the near future as new OWFs are planned in the vicinity of existing ones, with connections to more than one onshore AC system. This work addresses the control and parallel operation of three transmission links: VSC-HVDC, DR-HVDC, and HVAC, connecting a large OWF (cluster) to three different onshore AC systems. The HVAC link forms the offshore AC grid, while the diode rectifier and the wind farm are synchronized to this grid voltage. The offshore HVDC converter can operate in grid-following or grid-forming mode, depending on the requirement. The contributions of this paper are threefold. (1) Novel DR- and VSC-HVDC control methods are proposed for the parallel operation of the three transmission systems. (2) An effective control method for the offshore converter of VSC-HVDC is proposed such that it can effectively operate as either a grid-following or a grid-forming converter. (3) A novel phase-locked loop (PLL) control for VSC-HVDC is proposed for the easy transition from the grid-following to the grid-forming converter in case the HVAC link trips. Dynamic simulations in PSCAD validate the ability of the proposed controllers to ride through faults and transition between grid-following and grid-forming operation.

Early AC Power: The First Long-Distance Lines [History

In 1883, A 2,000-V, SINGLE-PHASE, 133 1/3-Hz power distribution system, designed and built by French inventor Lucien Gaulard and his British backer John Dixon Gibbs for the Metropolitan Railway of London, stretched for 15 mi and provided electric power for arc and incandescent lights at five railway stations. In 1884, a single-phase, 3,000-V, 133 1/3-Hz Gaulard?Gibbs power distribution system in Italy (Figure 1) extended about 25 mi from Turin (elevation 240 m, population 250,000 in 1881) to Lanzo Torinese (elevation 530 m, population 2,700 in 1881). It was the first multiple-user ac power-distribution system in the world. Having a small town at the foothills of the Italian Alps as the destination demonstrated the practicality of bringing electric power to remote, sparsely populated locations by using high-voltage ac power transmission. This would not have been possible profitably with Thomas Edison's low-voltage dc power transmission.

WiFi-controlled portable atomic force microscope.

This article proposes to develop a WiFi-controlled portable atomic force microscope (AFM). The AFM consists of a horizontal probe, controlling circuits, digital to analog (D/A) and analog to digital (A/D) interfaces, a microcomputer (Raspberry Pi, RPi), and a laptop. The proposed AFM uses a pocket-size power supply to drive the controlling circuits, the D/A and A/D interfaces, as well as the RPi that constructs network hotspots and generates scanning signals. With special design and integration of the whole system, both of the AFM probe and electronic controlling system are portable. At a distance of 50 m from the proposed AFM, experiments in the constant height mode and the constant force mode are conducted to evaluate its performance. The results show that this WiFi-controlled AFM has a maximum scan range of 3.6 × 3.6 μm2 with nanometer order resolution. Meanwhile, it achieves satisfactory image contrast, stability, and repeatability. Compared with conventional AFMs, the AFM proposed in this paper no longer relies on commercial AC mains supply or high-voltage DC power supply, and realizes WiFi-controlled AFM scanning and imaging in 50 m or farther without wire or network cable connection to a laptop or a desktop computer. Given credits to these features, WiFi-controlled AFMs are expected to own a wider range of application, especially in isolated environments, outdoor researches, or even fieldwork investigations.

Application of Integrated Optical Electric-Field Sensor on the Measurements of Transient Voltages in AC High-Voltage Power Grids

Transient voltages in the power grid are the key for the fault analysis of a power grid, optimized insulation design, and the standardization of the high-voltage testing method. The traditional measuring equipment, based on electrical engineering, normally has a limited bandwidth and response speed, which are also featured by a huge size and heavy weight. In this paper, an integrated optical electric-field sensor based on the Pockels effect was developed and applied to measure the transient voltages on the high-voltage conductors in a non-contact measuring mode. The measuring system has a response speed faster than 6 ns and a wide bandwidth ranging from 5 Hz to 100 MHz. Moreover, the sensors have the dimensions of 18 mm by 18 mm by 48 mm and a light weight of dozens of grams. The measuring systems were employed to monitor the lightning transient voltages on a 220 kV overhead transmission line. The switching transient voltages were also measured by the measuring system during the commissioning of the 500 kV middle Tibet power grid. In 2017, 307 lightning transient voltages caused by induction stroke were recorded. The characteristics of these voltage waveforms are different from the standard lightning impulse voltage proposed by IEC standards. Three types of typical switching transient voltage in 500 kV AC power grid were measured, and the peak values of these overvoltages can reach 1.73 times rated voltage.

Induced electromagnetic field on underground metal pipelines running parallel to nearby high voltage AC power lines

High voltage AC (HVAC) power lines can induce significant amount of voltages on underground gas/oil metal pipelines in areas where they share similar Right of Way (RoW), the situation becoming serious particularly in case of fault conditions. Electromagnetic field generated by the HVAC power lines on these pipelines, generate unwanted voltages which present threats to the pipeline and its associated protective equipment such as cathodic systems. The aim of this research is to compute induced voltage on pipeline running parallel to HVAC power lines. The study was conducted using CDEGS software package and revealed that under steady state condition, results were in agreement with GB 6830-1986 standard. However, high currents are generated under single phase to ground short circuit rising the potential of adjacent soil including the underground pipeline beyond limits. Therefore, the gradient control wire mitigation technique is proposed to reduce these voltages to safe limits.

Modified Algorithm for Fault Detection on AC Electrical Traction Line: An Indian Climate Case Study

Almost all the developing countries are electrifying more and more rail routes with high-voltage ac electric power, mostly with 25 kV, 50 Hz, or 60 Hz. However, electrified nonsuburban areas of tracks are prone to the risk of railway systems’ reliability. Deviation of 1 km in the informed fault location from the actual shall consume 40–50 min in excess to clear those faults off. This paper made intensive study at the sampling region in India revealed that the variation happened in the parasite capacitance is primarily responsible for the erratic pinpointing of the persisting earth fault position on the electrified railway system. The experimental studies conducted with the help of table top as well as prototype models of high-voltage ac traction lines for the identification and quantification of those vulnerabilities causing the changes in the parasite capacitance on ac electric traction system and the subsequent remodeling of it are detailed in this paper. Furthermore, this paper suggests the feasible algorithm to mitigate railways’ risk in pinpointing the persisting earth fault on high-voltage ac power traction lines with the dynamically modeled high-voltage ac electric railway traction line. The proposed algorithm has been tested on trial basis after approval from Indian Railways.

Environmental impact indicators for the electricity mix and network development planning towards 2050 – A POLES and EUTGRID model

Most prospective studies of the European power system rely on least-cost evaluations. This study assessed the influence of environmental impact indicators on prioritisation of ‘dispatchable’ technologies in the European energy mix up to 2050, compared with a purely cost-optimal system based on carbon tax incentives, without suppressing economic growth considerations. A model that combined the Prospective Outlook for Long-term Energy Systems model (POLES) and the European and Transmission Grid Investment and Dispatch model (EUTGRID)was used in the analysis. Combined current and prospective life cycle assessment (LCA) methodologies were added to the EUTGRID model to include environmental considerations in the decision-making process. Shifting from an economic to an environmental merit order in prioritisation increased the share of renewables by 2.65% (with variations between countries) and decreased overall emissions by 9.00%. This involved a change in grid infrastructure. Investments were found to be more important when optimisation was based on an environmental criterion on new high-voltage AC power lines, which resulted in a 1.50% increase in the overall cost of the power system. Finally, considering an environmental, instead of an economic, merit order allowed decarbonisation to be achieved slightly faster, resulting in lower cumulative greenhouse gas emissions to the atmosphere.

Optimal Allocation of Flexible AC Transmission System Controllers in Electric Power Networks

Due to increasing power demand, incorporation of prosumers, continuous expansion, competitive market and inherent limitations of alternating current, the management and operation of power system has become very complex. For economical, reliable and secure operation, the use of emerging technologies is unavoidable. Flexible AC transmission system (FACTS) is one of the emerging technologies which does not only solve the problems but also gives new directions in existing high voltage AC (HVAC) and high voltage DC (HVDC) power systems. However, allocation of FACTS controllers i.e., determination of optimal location, size, number and type of these devices with minimized cost is a difficult problem. This paper, in broader sense, discusses FACTS allocation for the solution of issues of power system. The benefits and objectives of optimal allocation of FACTS have been reviewed from view point of objective functions, decision variables, constraints and recent optimization algorithms.

Tuning Electrode Properties and Surface Contacts for Uniform Deposits Produced by Atmospheric Plasma Dielectric Barrier Discharge Reactors

An investigation of the effect of experimental parameters on the temperature and uniformity of material deposition by atmospheric pressure dielectric barrier discharge (DBD) planar plasma reactors was conducted. The apparatus consisted of a pulsed AC high voltage power source with various electrode materials (aluminum, copper wire mesh, and aluminum/copper wire mesh) operating under a range of load resistances. Possible effects of non-ideal interfacial conditions for the contact surface between the electrode and the substrate were also studied with various modified surface thermal conditions. It was found that a hybrid electrode design with a fine copper (Cu) wire mesh attached to an aluminum plate of approximately 3 mm thickness produced the most visually uniform deposit, presumably as a result of both the superior conductivity provided by the Al metal plate and the stable plasma resulting from the relatively low breakdown voltage by using helium (He) as the dilution gas. Although the experimental conditions of plasma-enhanced chemical vapor deposition (PECVD) are often specific to particular systems and applications, this work provides insights on technical details which can be applied to various plasma DBD reactors.

Influence of Duty Cycle on Ozone Generation and Discharge Using Volume Dielectric Barrier Discharge

The influence of duty cycle on ozone generation and discharge characteristics was investigated experimentally using volume dielectric barrier discharge in both synthetic air and pure oxygen at atmospheric pressure. The discharge was driven by an amplitude-modulated AC high voltage–power supply producing TON (a single AC cycle) and TOFF periods with a widely variable duty cycle. The experimental results show that the energy delivered to the discharge during each AC cycle remains roughly constant and is independent of feed gas, duty cycle and TOFF. Both average discharge power and ozone concentration show an initial linear increase with duty cycle, and deviate gradually from linearity owing to an increase in gas temperature at higher duty cycles. Nevertheless, ozone yield remains nearly constant (45.7 ± 3.5 g/kWh in synthetic air and 94.7 ± 3.1 g/kWh in pure oxygen) over a wide range of applied duty cycles (0.02–1). This property can be conveniently employed to develop a unique ozone generator with a widely adjustable ozone concentration and simultaneously a constant ozone yield. Additionally, the discharges in synthetic air and pure oxygen have similar electrical characteristics; however, there are observable differences in apparent luminosity, which is weak and white-toned for synthetic air discharge, and bright and blue-toned for pure oxygen discharge.

Characteristics of Coaxial Dielectric Barrier Discharge at Atmospheric Pressure

To further explore the conditions and mechanisms of generating uniform plasma in the flowing gas at atmospheric pressure, the dielectric barrier discharge (DBD) characteristics of the flowing helium, helium/oxygen mixture and the helium/methane mixture were studied at atmospheric pressure in this paper. A coaxial cylindrical double air gap structure was researched by discharge experiment at atmospheric pressure, using a high frequency and high voltage AC power source at a flow rate of 4 L/min. The discharge current is recorded by camera, the waveforms of current and voltage are recorded by oscilloscope. The discharge patterns and evolution processes of different gases in this structure were analyzed. The experimental results show that the helium can achieve uniform discharge in the structure with the frequency of 12kHz and the voltage of 1-2kV. The discharge pattern is glow discharge. Discharge forms of Helium/methane mixture and helium/oxygen mixture were filament discharge. The current waveform has obvious asymmetry in the positive and negative half cycles. The discharge mainly occurs in the positive half cycle, and the asymmetry gradually decreases with the increase of the voltage.

Calibration of free-space radiometric partial discharge measurements

The present study addresses the calibration of four types of partial discharge (PD) emulators used in the development of a PD Wireless Sensor Network (WSN). Three PD emulators have been constructed: a floating-electrode emulator, and two internal PD emulators. Both DC and AC high-voltage power supplies are used to initiate PD, which is measured using concurrent free-space radiometry (FSR) and a galvanic contact method based on the IEC 60270 standard. The emulators have been measured and simulated, and a good agreement has been found for the radiated fields. A new method of estimating the absolute PD activity level from radiometric measurements is proposed.