The main characteristics of the leader channel during breakdown of a long air gap by high pulse voltage

Goal. Calculation and experimental determination of middle speed vL of advancement of plasma leader channel of a pulse spark discharge in the long air interval of the double-electrode discharge system (DEDS) «tip-plane». Methodology. Bases of the theoretical electrical engineering and electrophysics, electrophysics bases of technique of ultra- and high-voltage and high pulse currents, bases of high-voltage pulse technique and measuring technique. Results. The close calculation and experimental method of determination of middle speed vL of advancement of plasma leader channel of an electric pulse spark discharge is offered in the long air interval of DEDS «tip-plane». This method is based on the offered calculation empiric formula for finding of the indicated speed vL and results of decoding of oscillograms of process of cut of in-use standard interconnect аperiodic pulse of over- and high-voltage of temporal shape of Tm/Тd≈200 μs/1990 μs of positive polarity at an electric hasp in indicated DEDS of long air intervals with their minimum length of lmin, numeral making 1,5 m (first case) and 3 m (second case). It is shown that middle speed vL of advancement in atmospheric air of front of plasma channel of positive leader of an electric pulse spark discharge in probed DEDS «tip-plane» for two considered applied cases at lmin=1,5 m of lmin=3 m numeral makes approximately vL≈(1±0,03)∙105 m/s. The found numeral value of this speed vL well coincides with the known experimental information for speed of advancement of vL≈105 m/s in atmospheric air of plasma channel of negative leader for a long storm spark discharge in DEDS «charged cloud-earth». It is set that for the standard interconnect аperiodic pulse of high- and ultra- voltage of temporal shape of Tm/Тd≈200 μs/1990 μs of positive polarity middle value of aggressive strength Ed of high pulse electric field in the air interval of probed DEDS «tip-plane» numeral makes minimum length of lmin=1,5 m near Ed1≈360,8 kV/m, and for his minimum length of lmin=3 m of − Ed2≈313,4 kV/m. Originality. The comfortable is developed in the use and reliable in practical realization technicians-and-engineers calculation and experimental method of research in the conditions of high-voltage electrophysics laboratory of difficult electro-discharge processes of development of leader hasp of long air intervals and determination of minimum electric durability of air insulation of electrical power engineering and electrophysics equipment on working voltage of classes of 330-1150 kV. Practical value. Application in area of industrial electrical power engineering and high-voltage pulse technique of the got numeral electrophysics results and offered calculation and experimental method of determination of middle speed vL of advancement in atmospheric air of plasma channel of leader of a long spark discharge will allow, from one side, to deepen our scientific knowledges about a long electric pulse spark discharge in an air dielectric, and, from other side, to develop high-voltage electrical power engineering and electrophysics devices with enhanceable reliability of their work both in normal operation and malfunctions.

Leader discharge is one of the main phases in long air gap breakdown, which is characterized by high temperature and high conductivity. It is of great importance to determine thermal characteristics of leader discharges. In this paper, a long-optical-path Mach-Zehnder interferometer was set up to measure the thermal parameters (thermal diameter, gas density, and gas temperature) of positive leader discharges in atmospheric air. IEC standard positive switching impulse voltages were applied to a near-one-meter point-plane air gap. Filamentary channels with high gas temperature and low density corresponding to leader discharges were observed as significant distortions in the interference fringe images. Typical diameters of the entire heated channel range from 1.5 mm to 3.5 mm with an average expansion velocity of 6.7 m/s. In contrast, typical diameters of the intensely heated region with a sharp gas density reduction range from 0.4 mm to 1.1 mm, about one third of the entire heated channel. The radial distribution of the gas density is calculated from the fringe displacements by performing an Abel inverse transform. The typical calculated gas density reduction in the center of a propagating leader channel is 80% to 90%, corresponding to a gas temperature of 1500 K to 3000 K based on the ideal gas law. Leaders tend to terminate if the central temperature is below 1500 K.

Summary form only given. As the most promising large-scale non-thermal plasma for industrial applications, dielectric barrier discharge (DBD) in atmospheric air usually behaves as filamentary discharge. However, it was found that diffuse DBD free of filaments could be produced in a 3mm air gap at one atmospheric pressure using two plane parallel electrodes each covered by one specific alumina plate bought from Zhuhai Yueke Co. LTD. Based on the discharge photographs of short exposure time taken with an ICCD camera, the discharge was identified with Townsend discharge. The Townsend breakdown voltage is only 5.7 k V, significantly lower than 11.2 kV, the static breakdown voltage of the 3mm air gap. If the alumina plates were replaced by 1mm-thick quartz plates which have the same capacitance with the alumina plates, it's impossible to get avoid filamentary discharges in atmospheric air or even the pressure went down to 1k Pa.

The article presents an experimental model of training future engineers in specialty“Electric Power Engineering, Electrical Engineering and Electromechanics”in conditions of massive open online courses (MOOC). The article reveals the concepts of modeling, designing and validity in pedagogy. The stages of construction of the pedagogical model are presented. Four blocks of the model of training the students in specialty”Electric Power Engineering, Electrical Engineering and Electromechanics”for educational and scientific activities in the conditions of MOOC are presented: motivational, content and procedural, technological and productive. The motivational block is characterized by the definition of the main goals of the introduction of pedagogical technology: the preparation of a highly qualified specialist. The content and procedural block is based on the implementation of pedagogical conditions of educational and scientific training. The technological block consists of three stages: motivational, cognitive-procedural and control-evaluation. The productive block provides monitoring of educational and scientific training of students in the specialty "Electrical power, electrical engineering and electromechanics".It is determined that there is feedback between all blocks of the model, which allows to make changes in the content, forms and methods of teaching. The principles of construction and the main structural elements of each of the blocks are analyzed. The general principles for the training of future engineers in specialty ‘Electric Power Engineering, Electrical Engineering and Electromechanics” are determined in conditions of MOOC; forms, methods and means of instruction are described. It is considered that educational and scientific training is implemented through such forms of teaching as lectures, video lectures, webinars, workshops, video conferences, discussion in forums, participation in scientific conferences and seminars. It is determined that the result of the developed model is readiness of the students majoring in ‘Electric Power Engineering, Electrical Engineering and Electromechanics” for research and study.

Goal. Development of engineering method for settlement of threshold amplitudes Impk of single-pulse current ip(t) of different temporal shapes for electric wires and cables with polyethylene (PET), polyvinylchloride (PVC) and rubber (R) half-length insulation, used in modern pulsed power engineering, electrical engineering and electronics in their low- and high-current circuits. Methodology. Basis of the theoretical and applied electrical engineering, electrical power engineering, electrophysics bases of technique of high-voltage and large pulsed currents, bases of low- and high-current electronics, measuring technique, electromagnetic compatibility and standardization. Results. Development of engineering method is executed on close calculation determination of threshold amplitudes Impk of single-pulse axial-flow current ip(t) of different temporal shapes for electric wires and cables with copper (aluminum) current-carrying parts and PET, PVC and R half-length insulation, used in the ow- and high-current circuits of pulsed electrical power engineering, electrical engineering and electronics. Electrothermal resistibility of half-length insulation of the examined cable and wire products (CWP), proper maximum to the possible temperatures of heating of current-carrying and insulating parts of the probed wires and cables and shutting out the offensive of the phenomenon destruction in the indicated insulation of CWP, was fixed based on this method. Calculation analytical correlations are obtained for finding in probed CWP of threshold numeral values of Impk amplitudes of pulses of current ip(t), time-varying both on aperiodic dependence of type τf/τp with duration of their front τf and duration of their pulses τp and by law of exponential attenuation sinewave. It is shown that at Imp>Impk destruction of their half-length insulation, resulting in the decline of service life of CWP, will come from the thermal overheat of current-carrying parts of the examined electric wires and cables. The examples of practical application of the offered method are resulted upon settlement for a radiofrequency coaxial cable RC 50-4-11 with middle sizes is easily soiled with continuous PET insulation of threshold amplitudes of Impk of standard aperiodic pulses of current ip(t) from nano-, micro- and millisecond temporal ranges of shape of τf/τp=5 ns/200 ns, τf/τp=10 μs/350 μs and τf/τp=7 ms/160 ms. It is shown that with the proper growth of parameter τp>>τf for flow on a continuous copper tendon and split copper shell of radiofrequency coaxial cable RC 50-4-11 with middle sizes is easily soiled indicated homopolar pulses of current ip(t) substantial diminishing of their threshold amplitudes of Impk (with 531,2 кА for the nanosecond pulse of current of type 5 ns/200 ns to 1.84 кА for the millisecond impulse of current of type of 7 ms/160 ms takes place). Originality. An engineering method is first developed for close settlement of threshold numeral values of Impk amplitudes of single-pulse axial-flow current ip(t) of arbitrary peak-temporal parameters for electric wires and cables with copper (aluminum) current-carrying parts and PET, PVC and R half-length insulation. Practical value. Application in electrical engineering practice of the offered engineering method for determination of threshold amplitudes Impk of the indicated pulses of axial-flow current ip(t) for the probed electric wires and cables will allow considerably to increase service life of examined CWP.

Non-thermal plasma produced by diffuse discharge in air at atmospheric pressure has advantages in the industrial application of the plasma surface modification. However, the discharge in atmospheric air usually behaves as filamentary discharge rather than diffuse discharge. It was found that diffuse discharge can be produced in a 3mm gap of air at atmospheric pressure by using two plane parallel electrodes each covered by one specific alumina plate with a thickness of about 2 mm. Based on the discharge photographs of short exposure time taken with an ICCD camera, the diffuse discharge was identified with Townsend discharge. The Townsend breakdown voltage for this 3mm air gap is about 8.3 kV, significantly lower than 11.2 kV, the streamer breakdown voltage of this gap. If the alumina plate is too thin, the discharge transits to filamentary discharge. If it is too thick, the discharge is too weak to observe. The uniqueness of the shallow traps on the surface of the specific alumina plate, as well as the effect of the current limitation by dielectric leads to a Townsend discharge. The detail mechanisms for the formation of Townsend discharge are still under investigation.

The detection of hard radiation emanating from an electrical discharge in air is still a mysterious phenomenon. This thesis focuses on collecting experimental data around spark condition that could lead to the production of energetic photon bursts. Long spark discharges with positive and negative polarity in air are studied. We accurately measure the electrical currents on both electrodes during the formation of the discharge. The Xrays are detected with scintillation detectors, time synchronized with the electrical parameters. Bursts up to several 100 keV photons are observed. The advantage of ‘laboratory lightning’ is the controlled environment that allows to study the distribution of the X-rays in space and time. The experiments are performed in the high voltage laboratory at Eindhoven University of Technology. A 2 MV twelve stage Marx generator, with a standardized lightning impulse with 1.2/50 µs rise/decay time to half-maximum when unloaded, delivers the high voltage air breakdown. A 9 m tall 1:2000 capacitive high voltage divider (part of the waveshaping circuit) is used to monitor the voltage waveform produced by the Marx generator. The generator is connected to a spark gap with two conical electrodes at distances varying between 0.76 and 1.46 m. The current at the grounded electrode is measured by a Pearson current probe. An identical probe around the high voltage electrode was connected through a fiber optical data transmission system for electrical isolation. Electromagnetic disturbance from the discharge itself was reduced to a negligible level in the measurements by proper design of the cables and protection equipment. Fast X-ray detectors with good energy resolution are imperative for reliable X-ray registrations. We use conventional NaI(Tl), nanosecond fast BaF2 and two newly developed LaBr3(Ce+) scintillation detectors, all with suitable photomultiplier integrated. Later the DTU National Space Institute assisted in the experiments with a test Cadmium Zinc Telluride (CZT) semiconductor detector intended for the Atmosphere-Space Interactions Monitor (ASIM) project. In early measurements partial discharges at unexpected positions occurred that could also produce X-rays. This effect could be controlled by covering sharp protrusions with conducting foil. The currents measured through both electrodes differ substantially during the firsts few microseconds. This is caused by the Ramo-Shockley effect. In the development phase of the discharge a charge cloud developed around the high voltage electrode and most of the associated electric field lines end in the environment of the grounded electrode, but not on the electrode. Through this current difference between both electrodes it was possible to tell where burst of X-rays are formed. For both polarities of the high voltage, the bursts of X-rays are associated with the negative streamer formation at the cathode. For positive polarity surges X-ray bursts detected coincide with the onset of the upward negative streamer prior to the bridging of the electrode distance. In the case of negative polarity surges X-ray bursts coincide with the negative streamers immediately at the onset of the spark formation. No X-rays have been detected during the large current of the gap breakdown. At gap breakdown both currents become equal. In a parallel investigation we confirmed that the LaBr3(Ce+) scintillation detector suited best for our experimental study because of the short decay time compared with NaI(Tl) and the better energy resolution compared with BaF2. Still, we found that pile-up of multiple photons and/or electrons can occur in the LaBr3(Ce+) detectors in the 23 ns of the 1/e decay. The LaBr3(Ce+) detector has been calibrated and tested for its linearity at photon energies between 59.5 and 2505 keV, employing photomultiplier bias voltages from 568 up to 1000 V. Preliminary X-ray measurements with a small CZT semiconductor detector gave no conclusive results due to the poor detection events (6 out of 100) obtained. Additional experiments with a larger detector for higher detection rates are recommended for a better understanding of the particle distributions involved. An additional experiment was carried out to confirm the emission of X-ray during the streamer phase of an electrical discharge in air. Streamer filaments were produced in a small streamer-corona reactor with nanosecond high voltage pulses up to 65 kV with an optional 20 kVdc offset. The short high voltage pulse period prevents the streamers to develop into an air breakdown. The LaBr3(Ce+) scintillation detector recorded X-rays from the streamer filaments with very consistent timing of occurrences. This proves that processes near the streamers heads are able to produce X-rays. Various results were presented at a number of international conferences and workshops. Chapter 3 and Chapter 4 have been published in Journal of Physics D: Applied Physics.

The object of the research is the circuit simulation model of a streamer breakdown of a rod-rod air gap when exposed to positive voltage pulses. One of the most problematic places in this task is determination of the time interval of the streamer propagation. The lower bound of this interval corresponds to the beginning of the streamer propagation, and the upper bound corresponds to the time when the streamer reaches the opposite electrode. To create such model, it is not enough to take into account only the functional relationship between the breakdown voltage and the spacing between the electrodes.\n\nWith the help of Kind's equal-area criterion in the circuit simulation programs it is possible to create the model of electrical breakdown of any air gap, including the rod-rod configuration.\n\nThe article shows how to create the model of electrical breakdown of the air gap in the evaluation version of the Micro-Cap 11 circuit simulator. Using the model, the breakdown time of the air gap is determined when subjected to the lightning pulses of positive polarity with different amplitudes. Wherein, the moments of breakdown of the air gap both at the front and at the tail of the applied voltage pulse are measured. Simulation results are compared with experimental data. It is determined that the simulation relative error does not exceed 10%. As experimental data, the experimentally obtained expression for the volt-time characteristic of the rod-rod air gap subjected to the positive polarity voltage pulses is used.\n\nThe proposed model allows to predict the volt-time characteristic of various air gaps in a virtual experiment. The model can be used in scientific work or in the educational process as an auxiliary tool for visual demonstration of the conditions for the electric breakdown in long air gaps.

Ionic wind produced by positive and negative corona discharges in air

Welcome to the 2024 International Conference on Power Electronics and Electrical Engineering (P3E 2024). We are delighted to present this year’s conference’s Proceedings, which embody a significant landmark in our continuous endeavor to facilitate collaboration between industry and academic institutions, particularly focusing on the development of power electronics and electrical engineering. As an important force to promote social progress and economic development, electrical engineering not only covers a variety of aspects such as power systems, electronics, automatic control, etc., but also continues to be deeply integrated with cutting-edge technologies such as artificial intelligence, big data, cloud computing and other cutting-edge technologies, showing a strong vitality and broad prospects for development. This event promises a series of in-depth discussions on various highly relevant topics such as electric power system, high voltage and insulation technology, circuits and electronics, power transmission and distribution, motor control, and a range of innovations that will shape the future. It is an opportunity for us to understand their impact across various sectors and how we can harness them. The form of this conference was made flexible with a virtual conference, providing a more flexible and diverse way to promote academic exchanges and cooperation on a global scale. And several guests accepted an invitation to deliver their plenary presentations at the P3E 2024. Junxing Zhang (Associate Professor from Guizhou University, China) explained the high-performance adaptive control for nonlinear PMSMs based on backstepping technique; Ismail Musirin (Professor from Universiti Teknologi MARA, Malaysia) delved into the techniques in controlling power system planning operation based on multi-objective; Akash Saxena (Professor from Central University of Haryana, India) proposed an optimization framework for intelligent demand-side management controllers in effective smart grid load management; Mohamed EL-Shimy (Professor from Ain Shams University, Egypt) talked about weakly interconnected microgrids and power systems using PODs considering WECSs based on facts. Through the sharing of the latest research results and cutting-edge ideological views, and the in-depth discussion of relevant academic challenges, this conference contributed to the continuous development and academic prosperity of the field of power electronics and electrical engineering. This Proceedings of P3E 2024 cover a wide array of topics, showcasing the diverse and evolving nature of research in power electronics and electrical engineering. Each paper has undergone a meticulous peer-review process to maintain the highest academic standards. We hope the Proceedings will not only reflect the current state of research in the field but also inspire future collaborations and innovations. Finally, we would like to express our sincere gratitude to all the contributing authors for your support and trust in this conference. And this conference would not have been possible without the dedication of the organizing committee, the support of our sponsors, and, most importantly, the participation of each and every one of you. Your presence here is a testament to your commitment to pushing the frontiers of knowledge and fostering innovation and collaboration. May this conference motivate all participants to pursue excellence in their fields. The Committee of P3E 2024 List of Committee Member is available in this Pdf.

Education and training serve as critical elements of advancement of a nation’s economy in transition. The restructuring of the power engineering industry in Russia has called for a fast implementation of new management system in electric power engineering and radical training of professional managers at different levels in organizations. Management training in electric power engineering in Russia has been implemented by (1) preparing highly professional managers in higher education institutions and technical universities and by (2) improving the management skills of practicing managers in technical universities and educational centers of different power energy companies. This article reports the experience of introducing a new discipline ‘Management in Electrical Engineering’ at the Moscow Power Engineering Institute (Technical University) and reflects on training managers in electric power engineering at higher education and corporate educational centers.

The stable homogeneous dielectric barrier discharge (DBD) is obtained in atmospheric 2–3 mm air gap. It is generated using center frequency 1 kHz high voltage power supply between two plane parallel electrodes with specific alumina ceramic plates as the dielectric barriers. The discharge characteristics are studied by a measurement of its electrical discharge parameters and observation of its light emission phenomena. The results show that a large single current pulse of about 200 μs duration appearing in each voltage pulse, and its light emission is radially homogeneous and covers the entire surface of the two electrodes. The homogeneous discharge generated is a Townsend discharge during discharge. The influences of applied barrier, its thickness, and surface roughness on the transition of discharge modes are studied. The results show that it is difficult to produce a homogeneous discharge using smooth plates or alumina plate surface roughness Ra < 100 nm even at a 1 mm air gap. If the alumina plate is too thin, the discharge also transits to filamentary discharge. If it is too thick, the discharge is too weak to observe. With the increase of air gap distance and applied voltage, the discharge can also transit from a homogeneous mode to a filamentary mode. In order to generate stable and homogeneous DBD at a larger air gap, proper dielectric material, dielectric thickness, and dielectric surface roughness should be used, and proper applied voltage amplitude and frequency should also be used.

Summary form only given, as follows. Glow-to-arc transitions in filamentary glow discharges in atmospheric air can be largely avoided by use of a plasma cathode, as has been demonstrated in short filamentary discharges in air. In these experiments a dc-driven microhollow cathode discharge (MHCD) was used as a plasma cathode to sustain a stable, direct current discharge between the plasma cathode and a third positively biased electrode. We have, using the same concept, extended the gap distance (distance between plasma cathode and third electrode) from previously 2 mm to the range from 6 mm to 20 mm and have studied the electrical, optical and plasma properties of such long filamentary glow discharges in atmospheric air. The MHCD is ignited between closely spaced molybdenum electrodes, separated by a 130 /spl mu/m thick alumina layer, with a 130 /spl mu/m hole through the sample. The filamentary discharge was ignited at small gap distances, in order to keep the ignition voltage at a low level, and then the gap was extended to the desired distance. In a certain range of current the filamentary glow discharge (FGD) current was found to be identical to the microhollow cathode discharge current. In this range control of the FGD by the MHCD is possible. From previous measurements of short gap filamentary discharge the gas temperature was found to be approximately 2000 K], the electron density was estimated as close to 10/sup 13/ cm/sup -3/. We will report on the results of measurements of these plasma parameters in long filamentary air discharges, and the electrical parameters, which determine the current range of MHCD control of the FGD. Parallel operation of these controlled filamentary glow discharges by using individual or distributed ballast might allow the generation of large volume, high pressure glows in air.

Summary form only given. Reducing the diameter of the cathode opening to values on the order of 100 micrometer allowed us to operate stable DC hollow cathode glow discharges in air at atmospheric pressure. Discharge currents of up to 30 mA with forward voltages around 400 V have been realized. In order to generate arrays of microhollow cathode discharges without resistive ballast, the current voltage characteristic of the discharge needs to have a positive slope. Results of modeling show the required increase of the forward voltage with current at high current values. However, overheating of the electrodes prevents DC operation of parallel discharges in atmospheric air in this current range. In order to extend the range of operation into the high current mode, the discharge has been operated pulsed with pulse duration from 1 to 100 microsecond. First experimental results confirm the modeling results. The electrical characteristic and the optical appearance of the discharge plasma in pulsed microhollow cathode discharges and its applications will be discussed.

Teaching Reform of Electrical Engineering and its Automation under the Background of Outstanding Engineers