Arc Operation Research Articles

Multi-classification fault diagnosis of AC series arc based on wavelet decomposition and probabilistic neural network

Abstract AC series arc is difficult to detect because of its complex characteristics, and it can easily cause electrical fire or explosion and other accidents. In order to solve the problem that multi-class loads can not be easily recognized when an arc fault occurs, this paper presents a method for AC series arc multi-classification fault diagnosis based on wavelet decomposition and probabilistic neural network (PNN). According to the standard, the experiment platform of fault arc is designed in this paper, and the current waveform data of fault arc and normal operation under different load types are collected. The multi-dimensional characteristics of the high-frequency current waveform are extracted by processing the detail coefficients obtained by wavelet decomposition. According to the load type and working state, multi-classification data sets are built and input into PNN to train and test the fault diagnosis model. The proposed method can not only accurately detect the fault arc, but also effectively identify the fault load line, which has important reference significance for AC series arc fault diagnosis.

To Research on Application and Maintenance of Sulfur Hexafluoride (SF6) Circuit Breaker

Circuit breakers play an extremely important role in power systems, and Sulfur Hexafluoride (hereinafter referred to as SF6) gas is the medium for the main functions of circuit breakers, and it has the functions of insulation and arc suppression. After the excavation of SF6 and reports on its application in electric power equipment and recently related literature, inspiring the author to summarize - the unique characters of SF6 and the arc suppression and operation principle, and explained some proper terms on the nameplate of the circuit breaker, all those combine an article, which can be prone to understand, at the same time it is easy to navigate of international journal on the website. In addition, for the abnormal situation of the connecting circuit breaker between the two busses in the substation, the "time constant" formed by the equivalent resistance and inductance value of the DC component of the zero-sequence fault current is related to the breaking time of the circuit breaker. Finally, combined above mentioned character with the points that must be paid attention to maintenance and being repaired on SF6 breaker in during, those things will be compiled into an article, which can be used as a reference for technical personnel in the field of power engineering.

Threshold parameters of vacuum arcs with W-fuzz cathodes

An experimental technique was developed and performed to investigate the threshold currents and operation times of vacuum arcs with tungsten cathodes having a nanostructured (so-called “fuzz”) surface. The fuzz layer, pre-formed due to exposure of the tungsten samples with helium plasma, reduced the threshold current for arc initiation by an order of magnitude. For currents of tenths of an ampere, the average arc operation time was in the microsecond range. The experimental data were interpreted using the explosive emission (ecton) model of a vacuum arc cathode spot.

Estimation of Pressure and Temperature Rise Due to Internal Arc Generation in Switchgears

The switchgears are vital component in energy system which protects, regulates and isolates the electrical transmission line by making or breaking the high voltage circuit with the use of circuit breakers. During the operation of switchgear internal arc is a failure criterion which is a result of a short circuit current. To quench this arc, the internal arc chamber is used which encapsulates the energy generated and protects the further transmission system and appliances. The gas insulated switchgears used for medium voltage application are enclosed inside the metal chambers and thus design of these chambers becomes crucial as they handle high pressures and temperatures. This fact is also exacerbated by the condition that metal chambers are prone to sudden increase in pressure due to internal arc phenomenon. The type testing process used for validating the design of chamber against internal arc is time consuming, costly and thus shall be performed with no margin of error. The paper aims to establish the standardized approach to calculate the instantaneous pressure and temperature rise inside the gas tank of switchgear which are otherwise impossible to approximate given the short timeframe in which internal arc occurs by using the approaches discussed in the CIGRE committee reports.

Parameters of the Ion Flux Generated in a Vacuum Arc With a Dielectric Cathode in the First Minutes After Breakdown

Stability is one of the key directions of optimization for plasma sources. This article deals with the parameters of the plasma flux generated in a vacuum arc with a dielectric cathode made of CeO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}$</tex-math> </inline-formula> in the period after a breakdown when the cathode relaxes after the impact caused by the initiation of plasma. The dielectric nature of the cathode made the period of relaxation rather long. It was shown that the plasma flux during the relaxation of the cathode was characterized by intense oscillations of ion energies and differed in the ionic composition from stable arcing. Cerium ions Ce <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{++}$</tex-math> </inline-formula> represented about 30% of the generated flux in the first minutes of the arc operation. An interpretation is presented of the anomalies observed.

Torsional Resonance Identification in Turbine-Generator Shaft Due to the Operation of Electric Arc Furnaces at Steel Mills in Bangladesh Power System

Torsional Resonance Identification in Turbine-Generator Shaft Due to the Operation of Electric Arc Furnaces at Steel Mills in Bangladesh Power System

Operating regimes of a constricted arc discharge in a forevacuum-pressure, plasma-cathode electron source of pulsed large-radius electron beams

We have investigated the operating regimes of a pulsed constricted arc discharge in a forevacuum plasma-cathode electron source of large-radius electron beams. The configuration of the intermediate electrode (IE) with a constricting channel (CC) determines the maximum parameters (current and pulse duration) and operating regimes of the constricted arc. An IE with ceramic (aluminum nitride) CC and an IE with sectional tantalum CC, formed by several electrically insulated tantalum disks with co-axial holes, lead to an increase in the maximum parameters compared to an IE with metal CC. In particular, an IE with sectional tantalum CC provides the highest maximum parameters. The ceramic and sectional tantalum constricting channels also provide lower minimum pressure for which the constricted arc operates stably. When the pressure reaches a certain threshold value, which depends on arc current, a discharge system with IE with sectional tantalum CC provides stable operation for pulse duration up to 10 ms. An increase in pressure provides higher discharge current in the millisecond regime of the discharge operation. When the arc current reaches threshold values from 84 to 92 A (depending on gas pressure), a self-compressed (pinched) mode of operation of the constricted arc occurs. The pinched arc regime is characterized by the highest current and the longest pulse duration. The forevacuum electron source based on the constricted arc discharge with IE with sectional tantalum CC offers generation of low-energy (up to 8 keV) electron beam with current up to tens of amperes and pulse duration up to 10 ms.

A Startup Control Method for Plasma Lamps by Using Fractional-N Phase-Locked Loop Microwave Driver

The microwave-driven plasma light source has the feature of the full spectrum, similar to sunlight, and has broad application prospects. Startups of plasma lamps are very difficult since the plasma density and the resonator impedance are changing constantly with the warm-up process and the RF driver can hardly couple the power to the plasma efficiently. This paper presents a startup control method for plasma lamps by using an integrated fractional-N phase-locked loop (PLL) as the RF signal source. An RF control module including a 21 dBm RF source with a band of 430–460 MHz and detection circuits for the RF driver is developed, and the startup process of the plasma lamp is further studied by analyzing the return loss of the resonator under the plasma load. According to the test result, the maximum frequency deviation of the RF control module is 3.3 kHz over the working temperature range of −40–80 °C. The designed RF control module is used to drive a high-power amplifier to start the plasma lamp automatically. It takes 79 s to achieve the stable arc operation from the gas breakdown. The return loss of the resonator is −26 dB, with an incident power of 171 W and reflected power of 418 mW, indicating that the RF driver and the plasma achieve good coupling. Compared with continuous wave, the luminous flux of the lamp powered by RF pulse improves by 18% under the same electric power. This startup control method has stable performance, small temperature drift, and an effective control function for plasma lamps.

Numerical investigation of AC electric arc plasma heat dissipation in EAF

ABSTRACT The alternating current (AC) electric arc furnace (EAF) is a crucial steelmaking facility consuming electricity to melt the recycled scrap. The arc heat dissipation impacts the scrap melting rate. The present study established a mathematical model to simulate the AC electric arc and estimate its heat dissipation under different arc operations. The study was aimed to deduce the relationship between arc operating current, arc length and the share of different arc heat dissipation mechanisms for future application in the scrap melting model. Validations of arc modelling were conducted by comparing the results against experimental data and simulations in the literature. A statistical method based on data sampling was proposed to determine the AC arc state variables to approximate the arc heat dissipation. A scrap melting experiment was designed and implemented in NLMK EAF to validate the amount of share determined in the present study for different arc heat dissipation mechanisms.

Measurement of Momentum and Recoil Impulse of Plasma Jet of Vacuum Arc Thruster

To measure the mechanical momentum of a plasma jet, the deflection of a collector suspended on long threads in front of the jet was analyzed (ballistic pendulum method). Alternatively, the recoil impulse in frequency mode of arc operation was measured with a specially designed thrust balance. The dependence of the vacuum arc plasma jet momentum and recoil impulse on the arc current amplitude was studied in the current range from 10 to 800 A. The experiment shows that at a relatively low arc current ( $150~\mu \text{N}$ /A, which is consistent with the known data; with a further increase in the arc current (>100–150 A), the specific reaction force increases and can significantly exceed the above mentioned value. In addition, the specific reaction force strongly increases when the axial magnetic field is applied to the discharge cell. The experiments performed with two cathode materials are also compared. The material presented in the article is of interest for fundamental and methodological issues as well as for applications primarily to the creation and testing of vacuum arc based micro-thrusters ( $\mu $ VAT) for small/ultra-small satellites.

Increasing the oxygen dissociation degree in the plasma of a pulse-periodic Ar/O2 low-pressure arc

The results of a study on O2 dissociation conditions in the near-anode area of forcibly compressed low-pressure arc discharge are presented. A combined mode of discharge operation was applied to increase the O2 dissociation degree. In this mode, high-current pulses (up to 160 A) of short duration (100 μs) were imposed on a direct current discharge (up to 70 A). Probe measurements showed that a higher atomic oxygen concentration is caused by increasing not only the electron current, but also the voltage drop in the anode part of the discharge in the pulsed phase. A necessary condition for achieving high average values of O2 dissociation degree at high pulse ratio is the increased lifetime of oxygen atoms in the volume. This condition is fulfilled in a gas-discharge system with metal walls used for the deposition of oxide coatings through formation on the walls of amorphous oxide films, which have a low atomic oxygen recombination coefficient. An O2 dissociation degree of ∼0.4 in a low-pressure arc (less than 1 Pa) in Ar/O2 mixture was obtained by optimizing the parameters of the arc operation mode and the condition of the wall surface of the gas-discharge system.

In vitro study of the antibacterial properties of amorphous copper-doped carbon coatings

A deposition technology of amorphous carbon coating (a-C), doped with copper (C-$$$Cu), has been developed. The C-Cu coating deposition was performed with the simultaneous operation of arc- and pulse-arc sources with copper and graphite cathodes, respectively. There was studied the antibacterial activity of the a-C and C-Cu against E. coli, S. aureus and P. aeruginosa. The copper-doped coating has bactericidal activity against P. aeruginosa. The number of bacterial colonies is five times lower in compare with a-C and Ti.

Maximal current of a pulsed constricted arc discharge operating in the forevacuum plasma electron source

The paper presents results of investigation of maximal current of the pulsed constricted arc discharge generating emission plasma in the forevacuum plasma electron source. Distinctive feature of the forevacuum plasma electron source is the absence of pressure differential between region of formation of emission plasma and the region of acceleration and propagation of electron beam. Therefore, the operating conditions of the constricted arc in the forevacuum plasma source are significantly different from the conditions in the plasma electron sources generating electron beams at pressure 10–3–10–1 Pa. The constriction of the positive column of the arc discharge provides, as it known, to reduce influence of instability and chaotic behavior of the cathode spot of the arc on the formation of emission plasma. In the investigated pressure range 3–20.5 Pa, the maximal current of the constricted arc discharge has been limited either by extinction of the arc or by initiation of the cathode spots on the constricting electrode and transition of the arc operation to the cascade mode. Increase of gas pressure and the use of working gas with larger ionization cross section (e.g. argon) have provided increase of the maximal arc current. The increase in the constricting channel diameter has provided the increase of maximal current and provided lower minimal gas pressure, at which stable operation of the constricted arc ensured. The decrease of length of the constricting channel has provided noticeable increase in the maximal arc current only at gas pressure more than 12 Pa.

Equilibrum Composition of Thermal Plasma with Copper and Chromium Vapours Admixtures

Thermal plasma of electric arc is widely used in various technological applications: welding, cutting, lamps, spraying, protection of electrical installations, etc. Process efficiency is defined by different parameters that determine arc operation and influence the energy transfer within the medium. All energy exchanges depend on the medium, which is modified by the presence of the arc and more particularly by the appearance of new species from contact erosion. Sintered Cu-Cr composites are widely used as electrical contacts for vacuum circuit breakers. These materials take advantage of the high thermal and electrical conductivity of Cu and of the refractory and oxygen getter properties of reinforcing Cr particles. The aim of this paper is to give results of the calculation of the equilibrium composition of argon and air plasma with various admixtures of Cu and Cr.

Simulating changes in shape of thermionic cathodes during operation of high-pressure arc discharges

A numerical model of current transfer to thermionic cathodes of high-pressure arc discharges is developed with account of deviations from local thermodynamic equilibrium occurring near the cathode surface, in particular, of the near-cathode space-charge sheath, melting of the cathode, and motion of the molten metal under the effect of the plasma pressure, the Lorentz force, gravity, and surface tension. Modelling results are reported for a tungsten cathode of an atmospheric-pressure argon arc and the computed changes in the shape of the cathode closely resemble those observed in the experiment. The modelling has shown that the time scale of change of the cathode shape during arc operation is very sensitive to the temperature attained by the cathode. The fact that the computed time scales conform to those observed in the experiment indicate that the model of non-equilibrium near-cathode layers in high-pressure arc discharges, employed in this work, predicts the cathode temperature for a given arc current with adequate accuracy. In contrast, modelling based on the assumption of local thermodynamic equilibrium in the whole arc plasma computation domain up to the cathode surface could hardly produce a similar agreement.

Comprehensive Electric Arc Furnace Electric Energy Consumption Modeling: A Pilot Study

The electric arc furnace operation at the Štore Steel company, one of the largest flat spring steel producers in Europe, consists of charging, melting, refining the chemical composition, adjusting the temperature, and tapping. Knowledge of the consumed energy within the individual electric arc operation steps is essential. The electric energy consumption during melting and refining was analyzed including the maintenance and technological delays. In modeling the electric energy consumption, 25 parameters were considered during melting (e.g., coke, dolomite, quantity), refining and tapping (e.g., injected oxygen, carbon, and limestone quantity) that were selected from 3248 consecutively produced batches in 2018. Two approaches were employed for the data analysis: linear regression and genetic programming model. The linear regression model was used in the first randomly generated generations of each of the 100 independent developed civilizations. More accurate models were subsequently obtained during the simulated evolution. The average relative deviation of the linear regression and the genetic programming model predictions from the experimental data were 3.60% and 3.31%, respectively. Both models were subsequently validated by using data from 278 batches produced in 2019, where the maintenance and the technological delays were below 20 minutes per batch. It was possible, based on the linear regression and the genetically developed model, to calculate that the average electric energy consumption could be reduced by up to 1.04% and 1.16%, respectively, in the case of maintenance and other technological delays.

The investigation of an electric arc in a plasma chemical reactor for hazardous waste treatment

AbstractBACKGROUNDResearch was performed to reveal the main peculiarities of an operating electric arc in a plasma chemical reactor (PChR) for hazardous waste processing. The experimental study was performed in a model of PChR using thermal plasma as a heat source. Investigations described are conducted to study the voltage–current characteristics (VCC) and heat transfer between an electric arc and a flat anode during the free arc operation in an ambient nitrogen (N2) atmosphere.RESULTSPlasma torch (PT) parameters varied in the range of I = 100–600 A, U = 50–450 V, x = 0–400 mm, G = 2–4 g s−1 at atmospheric pressure using N2 as plasma‐forming gas. It was found that the power value of the laminar arc increased with increasing arc current and length. With increasing arc length, its initial part started to operate in a turbulent regime. It was observed that the region of laminar regime appeared in the area where arc power was inversely proportional to arc current. The dependence of the heat flux transferred by the electrons to the anode on arc current was determined. The distribution of convective heat flux density over the anode heating spot was analyzed and generalized. The experimental data on convective heat transfer in the anode (mean and critical point) were discussed.CONCLUSIONThis confirmed that plasma technology has several advantages over conventional incineration including higher temperatures, independence of heat source from the waste being destroyed or additional fuel, and shorter exposure time of hazards in the high‐temperature area. © 2019 Society of Chemical Industry

Beryllium thin films deposited by thermionic vacuum arc for nuclear applications

The aim of this paper is to investigate the influence of the thermionic vacuum arc (TVA) operation parameters (arc current, arc voltage and thermo-emission filament current) on the Be ion energy and plasma ionization degree, as well as on the topological, structural and mechanical properties of Be thin films.For this purpose, nanocrystalline Be thin films, with thickness of approximately 1 μm, were deposited by TVA on not intentionally heated silicon and stainless steel substrates by varying the arc voltage from 0.8 to 2.0 kV. Topological, structural and mechanical (hardness, Young's modulus, adhesion critical loads, and friction coefficient) properties of Be thin films were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), nanoindentation and scratch tests.The mechanical behaviour and structural changes are discussed based on TVA plasma diagnostics results. Be ion energy and plasma ionization degree were measured using cold and emissive probes, energy-resolved mass spectrometer and a quartz crystal microbalance.The preferential crystallographic orientation, morphology and packing density are sensitive to the selected processing parameters which, in turn, control, over a wide range, the plasma ionization degree and Be ion energy. The film deposited using an arc voltage value of 1.5 kV exhibits dense structure with low lattice defect density, high hardness, low coefficient of friction, good wear-resistance, fracture toughness and adhesion to the substrate.

Effect of a magnetic cusp configuration on the ion species ratio in a NBI ion source

In arc discharge plasma, ion species ratio depends on plasma density and ion confinement time. To increase an atomic ion species ratio in an NBI (neutral beam injector) ion source, various ion sources have been designed with a higher ratio of plasma volume to effective ion loss area for increasing ion confinement time. In such designs, most NBI ion sources have a large arc chamber with strong cusp magnetic field. KSTAR NBI ion source also has a large arc chamber with a strong azimuthal line cusp configuration but its atomic ion (H+) beam fraction is small because its normal operation power levels of the arc discharges are comparatively lower than those of other NBI ion sources. In particular, the H2+ ion beam fraction is relatively large at about 40%. This means that there are many primary electrons in the beam extraction region. Through several Ele-orbit code simulations, it was found that some magnetic cusp configurations are effective in preventing primary electrons from nearing the plasma grid facing a plasma and having a high voltage potential. To reduce the molecular ion fraction in KSTAR NBI ion source and consequently increase its atomic ion fraction, experiments regarding the application of several new magnetic cusp configurations to the arc chamber were performed. Experimental results show that the new magnetic cusp configuration can increase the atomic ion fraction to approximately 80%, despite the low arc operation power at KSTAR NBI ion source.

Diffuse vacuum arc on cerium dioxide hot cathode

A diffuse (spotless) vacuum arc was investigated on a hot cathode made from cerium dioxide. The discharge is obtained in the following range of current, voltage, and cathode temperature of I = 15–150 A, Va = 9–14 V, and Tc = 2.1–2.4 kK. The main characteristics of the plasma flow in space behind the anode with a hole were determined: it was found that the electron temperature at the working parameters lies in the range of 0.4–1 eV, the ions are predominantly singly charged, the average charge of the outgoing heavy particles reaches 0.9 e (elementary charge), and the most probable kinetic energy of the ions does not exceed 9 eV. Potentially found regimes of vacuum arc operation are promising for use in the work on implementation of the plasma method for spent nuclear fuel and/or radioactive waste reprocessing.