Inverse Problem Solution and Regularization Parameter Selection for Current Distribution Reconstruction in Switching Arcs by Inverting Magnetic Fields

Current density distribution in electric arcs inside low voltage circuit breakers is a crucial parameter for us to understand the complex physical behavior during the arcing process. In this paper, we investigate the inverse problem of reconstructing the current density distribution in arcs by inverting the magnetic fields. A simplified 2D arc chamber is considered. The aim of this paper is the computational side of the regularization method, regularization parameter selection strategies, and the estimation of systematic error. To address the ill-posedness of the inverse problem, Tikhonov regularization is analyzed, with the regularization parameter chosen by Morozov’s discrepancy principle, the L-curve, the generalized cross-validation, and the quasi-optimality criteria. The provided range of regularization parameter selection strategies is much wider than in the previous works. Effects of several features on the performance of these criteria have been investigated, including the signal-to-noise ratio, dimension of measurement space, and the measurement distance. The numerical simulations show that the generalized cross-validation and quasi-optimality criteria provide a more satisfactory performance on the robustness and accuracy. Moreover, an optimal measurement distance can be expected when using a planner sensor array to perform magnetic measurements

Direct observation of vacuum arc evolution with nanosecond resolution

Sufficiently high voltage applied between two metal electrodes, even in ultra high vacuum conditions, results in an inevitable discharge that lights up the entire gap, opening a conductive channel through the vacuum and parasitically consuming large amounts of energy. Despite many efforts to understand the processes that lead to this phenomenon, known as vacuum arc, there is still no consensus regarding the role of each electrode in the evolution of such a momentous process as lightning. Employing a high-speed camera, we capture the entire lightning process step-by-step with a nanosecond resolution and find which of the two electrodes holds the main responsibility for igniting the arc. The light that gradually expands from the positively charged electrode (anode), often is assumed to play the main role in the formation of a vacuum arc. However, both the nanosecond-resolution images of vacuum arc evolution and the corresponding theoretical calculations agree that the conductive channel between the electrodes is built in the form of cathodic plasma long before any significant activity develops in the anode. We show evidently that the anode illumination is weaker and plays a minor role in igniting and maintaining the conductive channel.Peer reviewe

Tests of IEEE 1588-based synchronization system in substation

Kao metoda sinkronizacije, IEEE1588 norma je primijenjena u trafostanici, to bi trebalo osigurati ispitanu i provjerenu sinkronizacijku točnost i čvora interoperabilnosti. Metoda sveobuhvatnog testiranja za IEEE1588 se predlaže u ovom radu. Nadalje, IEEE1588 platforma testiranja ure izgrađena je kao podrška predložene metode ispitivanja. Na temelju analize sinkronizacije pogreške ure i metode ispitivanja načela značajke, ocjenjene su točnost i stabilnost glavne ure i pomoćne ure. Drugo, ispitivanje usklađeno s normom za usvajanje odziva značajke je postignuto dizajniranjem konkretnog slučaju, na osnovi navedenog, a potom analizirati pojedinosti provedbe sukladnosti. Prema zahtjevima ispitivanja, dizajnirana je testna osnovna ploča. Konačno, pokus utemeljen na uređajima transfostanice proveden je uporabom IEEE1588 platforme testiranja ure. Izvedivost predloženih metoda dodatno je potvrđena s rezultatima testiranja.As a synchronization method, IEEE1588 standard has been applied in substation, it should be tested and verified ensure synchronization accuracy and node interoperability. A comprehensive testing method for the IEEE1588 is proposed in this paper. Furthermore, IEEE1588 clock testing platform is built to support the proposed testing method. Based on the analysis of the clock synchronization error and the performance testing principle method, the accuracy and stability of master clock and slave clock were evaluated. Secondly, the conformance testing to adopt performance response was achieved by designed specific case, based on the above, and then to analyse the conformance implementation details. According to testing requirements, test bed designed. Finally, the experiment based on substation devices was carried out using the IEEE1588 clock testing platform. The feasibility of the proposed methods was further verified with the testing results

Optimization on the jet characteristics of the main nozzle of hot-blowing snow removal device

The exhaust devices used by snow removal vehicles are mainly based on hot-blowing snow removal. Due to the inherent characteristics of the turbojet engine such as low flow rate and high exhaust temperature, the modified hot-blowing snow removal device has problems of low snow removal efficiency and the possibility of ablation and damage to the road surface. In order to solve the problem, transforming the turbofan engine with a high flow rate and a low exhaust temperature into a hot-blowing snow removal device is an important improvement to achieve efficient and safe snow removal operations. In order to convert a medium bypass ratio turbofan engine into a hot-blowing snow removal device, the computational fluid dynamics (CFD) software CFX was used to analyze the internal and external flow field characteristics of the main nozzle of an exhaust device under the 60 % rated condition of the engine. The effective area sizes of the jet velocity and temperature predicted by the external flow field were used to optimize the layout of the main nozzle

Effect of Arc Chute on DC Current Interruption by Liquid Nitrogen in HTS Electrical System of Distributed Propulsion Aircraft

The distributed propulsion aircraft with HTS electrical system is a novel concept for future airliners, which can reduce by more than 70% fuel burn and NO x emissions. The circuit breakers ensure the security of this novel aircraft by isolating electrical faults timely. Solid-state circuit breakers (SSCBs) are preferred due to their fast response and high performance in the cryogenic circumstance. However, the high conduction loss of SSCBs impedes their further application. A mechanical switch using liquid nitrogen (LN 2 ) as an arc extinguishing medium shows excellent DC current interruption performance. The LN 2 switch is characterized with extremely low contact resistance, and the proper use may reduce the conduction loss of power switches significantly. Nevertheless, the effect of metal type arc chutes on the arcing process in the LN 2 is still not clear. Thus the objective of this paper is to understand the effect of metal type arc chutes on the current interruption performance of LN 2 . Silicon iron arc chutes are employed. Neodymium (NdFeB) magnets are used to stretch the arc into the arc chutes. The maximum interrupting current is 1 kV/ 2 kA when only magnets are applied. Further applying the arc chutes leads to a significant drop in the arc voltage and interruption performance. Since the high relative permeability of silicon iron weakens the magnetic field acting on the arc, metal type arc chutes are not recommended. 1 kV / 10 kA fault current is successfully cleared by the combination of resistance type superconducting fault current limiter (R-SFCL) and LN 2 switch with magnets, during which the R-SFCL responds to the fault within 420 μs, compensating the long clear time of the LN 2 switch

PSpice simulacije za enofazne usmernike za testiranje DC varovalk

In this article, simulations were realized for different power rectifiers used for testing DC fuses. Using the OrCAD PSpice software, a single-phase uncontrolled bridge rectifier and a single-phase controlled bridge rectifier are simulated for different loads. From the data analysis, some important conclusions were realized regarding the form of the temperature waveforms in transient conditions and quasisteady state thermal conditions.V tem članku so bile izvedene simulacije za različne usmernike moči, ki se uporabljajo za preskušanje enosmernih varovalk. S programsko opremo OrCAD PSpice se simulirajo enofazni nenadzorovani mostni usmernik in enofazni mostični usmernik za različne obremenitve. Iz analize podatkov je bilo ugotovljenih nekaj pomembnih zaključkov glede oblike temperaturnih valov v prehodnih pogojih

Spectroscopic study of vacuum arc plasma expansion

Vacuum breakdown (also known as arc or discharge) occurs when a sufficiently high electric field is applied between two electrodes in vacuum. The discharge is driven by the formation of an intensively glowing plasma at the cathode, which is followed by the ignition of an anode flare that gradually expands and fills the gap. Although it has been shown that the anode electrode does not play a significant role in the breakdown initiation, the nature of the anodic glow is of paramount importance for understanding the breakdown evolution. In this work, we use time- and space-resolved spectroscopy to study the anode flare. By using different anode and cathode materials, we find that excitations from both anode and cathode ions and neutrals contribute to the anodic glow. This implies that the cathodic plasma expands towards the anode without emitting any detectable light and starts glowing only when it reaches and interacts with the anode electrode. This interaction causes the introduction of anodic species in the plasma. The latter starts producing an expanding glow which contains spectra from both the cathode and anode materials and gradually fills the gap as the plasma equilibrates. Finally, we observe that after a breakdown, cathode material deposits on the anode electrode, gradually coating it. After hundreds of breakdowns, this coating covers the anode, resulting in the decay and possible elimination of the anode material signal in the spectra.Peer reviewe

Effect of the anode material on the evolution of the vacuum breakdown process

Vacuum breakdown, also known as vacuum discharge, is a common phenomenon in nature and is gaining an increasingly important role in modern technologies. In spite of a remarkable advance in our understanding of the nature of the breakdown, the role of the anode, i.e. the positively charged electrode, in the development of the breakdown is still completely unclear. In this paper, we employ a streak camera with picosecond time resolution to observe precisely the evolution of anodic glow from different anode materials. The results show that the choice of the anode material does not affect either the delay time between the cathodic and anodic flares or the formation of the conductive channel. Furthermore, we show that the heating of the anode surface by runaway electron currents is not sufficient to evaporate enough atoms for the anodic glow. On the other hand, we show that the neutrals for the anodic flare can be produced by the ions from the expanding cathode plasma by sputtering. Finally, the coincidence in time of the voltage collapse and the anode glow is consistent with the fast expansion of the cathode plasma, which causes both the voltage collapse and the anode glow when it reaches the anode, and densifies by sputtering and reflection. However, the two events are not in direct dependence of one another, since the order of their appearance is random, implying that a fully conductive channel can be established without any light emission from the anode.Peer reviewe