Pulsed Voltage Conditions Research Articles

Research on partial discharge signal denoising based on Kalman-WPT

Abstract Oil-immersed insulating paper will produce partial discharge under high-frequency pulse voltage conditions, so suppressing or reducing the generation of partial discharge signals is an important method for stabilizing the operation of power equipment. However, it has been found in experiments that various interference signals can affect the generation, capture, and measurement of partial discharge signals during various analyses. Therefore, how to capture partial discharge signals effectively and accurately through denoising algorithms has become the focus of this series of experiments. Kalman filtering and wavelet packet transform are the most basic and commonly used methods for denoising at this stage. By analyzing and comparing the basic principles and characteristics of the two methods, the author proposes a Kalman-WPT joint denoising method and conducts simulation analysis using MATLAB 2022b. Multiple controlled experiments have shown that the signal-to-noise ratio of selected discharge signals has increased from 1.3052 for Kalman filtering and 8.9553 for wavelet packet transform to 10.3702, which is sufficient to prove that this method enhances the denoising effect on the original partial discharge signal, reduces waveform distortion, and greatly improves signal detection accuracy.

Electrochemical degradation of perfluorooctanoic acid in aqueous solution by boron-doped diamond electrodes under pulsed voltage conditions

• Degradation of persistent substance by pulsed electrochemical oxidation. • Pulsed degradation more efficient than direct current. • Pulse width affects the degradation rate. • Degradation of PFOA with Pt and graphite electrodes. The aim of this study was the electrochemical degradation with boron-doped diamond (BDD) electrodes using pulsed direct current (PDC). An electrochemical characterization of the BDD electrode in aqueous solution was performed to determine the optimal parameters for the PDC. By means of cyclic voltammetry a capacity of 81 µFcm −2 of the electrolytic double layer was determined and confirmed by impedance spectroscopy. Impedance spectroscopy showed an optimal frequency range of 1–5 Hz and thus an ON-time of the voltage pulse of 100-300 ms. An OFF-time of minimum 100 ms was determined by chronoamperometry. Perfluorooctanoic acid (PFOA) was selected as a model substance to investigate the influence of pulsed operation on electrochemical degradation. Based on the PDC experiments, an amplitude of 8 V was obtained for the pulsed electrochemical degradation of PFOA in aqueous solution. The variation of the ON-time showed an influence on the degradation rate of PFOA. The pulsed degradation with an ON-time and an OFF-time of 300 ms showed a degradation of PFOA of 56%. In contrast, only 42% degradation was achieved under direct current conditions. In addition, comparative experiments were carried out with platinum and graphite electrodes, showing the degradation of PFOA. Degradation and transformation products of PFOA were identified by liquid chromatography with high resolution mass spectrometry.

A mathematical model to predict the porosity of nickel pillars manufactured by localized electrochemical deposition under pulsed voltage conditions

Metal parts manufactured with engineered porosity offer advantages over traditional parts as they have excellent specific mechanical properties at a lower weight. This is especially of interest in the aerospace and automobile industries. Additive manufacturing allows for creating parts with computer aided design (CAD) modeled lattice structures that offer lightweight parts. However, there is a need for porous structures at the micron scale (<50 µm) which cannot be achieved in a controlled manner using traditional powder-bed based metal additive manufacturing processes. Electrochemical Additive Manufacturing (ECAM) is a novel non-thermal metal additive manufacturing process capable of producing metal 3D parts with engineered porosity at the micron scale. There is a lack of understanding of the cause of porosity and controlling the porosity generated in the parts created using this process. In this paper, the effects of the electrical parameters of deposition, such as the pulse duty cycle and pulse frequency during electrodeposition, on the porosity of the manufactured parts were mathematically modeled. The model predicts that higher frequency electrodeposition leads to more porous structures. The model developed in this study can be used to predict the process parameters needed to deposit nickel microstructures with desired levels of porosity between 20 and 55 %. These model predictions were also validated by experiments. Two mechanisms for the cause of porosity in the deposits were identified. The diffusion-limited deposition phenomenon causing a lack of availability of cations results in larger sized pores and hollow structures to form on the part. The crystal growth and the nucleation process cause micron-scale pores.

Electroluminescence Dynamics in Perovskite Solar Cells Reveals Giant Overshoot Effect.

High performance of both photovoltaic and electroluminescent devices requires low nonradiative recombination losses. In perovskites, such loses strongly depend on the carrier traps related to the mobile ions and vacancies, causing I- V hysteresis of solar cells and influencing the performance of other optoelectronic devices, such as photodetectors and LEDs. To address the dynamics of the mobile ions, here we investigate electroluminescence time evolution in perovskite solar cells under constant and pulsed voltage conditions. We propose a model, accounting for the spatial ion accumulation and explaining the complex electroluminescence dynamics both on fast (microseconds) and slow (seconds) time scales. We demonstrate the appearance of a high-intensity short electroluminescence peak (overshoot pulse) immediately after termination of the electrical pulse. The generation of a giant overshoot pulse suggests a simple way to achieve high pulsed luminescence intensity with a low current density, which opens new prospects toward optical gain and implementation of electrically pumped lasers.

Comparative study of 0° X-cut and Y + 36°-cut lithium niobate high-voltage sensing.

A comparison study between Y + 36° and 0° X-cut lithium niobate (LiNbO3) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y + 36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5 μs voltage pulses to both crystals, the voltage-induced shift scaled linearly with voltage. For the Y + 36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz-100 kHz. Using the same conditions as the Y + 36° cut, the 0° X-cut crystal sensed a shift of 10-273 ps for DC voltages and 189-813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250-2 ns and the Y + 36°-cut crystal sensed a time shift of 0.115-1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. When the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.

Fabrication of GaN-based metal-oxide-semiconductor light-emitting diodes operating in ultraviolet spectral region

Integrated light-emitting diodes (LEDs) that operate in the UV spectral region were fabricated using GaN layers grown on sapphire substrates by metal-organic vapor phase epitaxy. Schottky-type LEDs and metal-oxide-semiconductor (MOS) LEDs were realized. The near-band-edge emission of GaN was observed in the electroluminescent spectra with reversed bias under pulsed-voltage conditions. The insertion of an aluminum oxide layer in the GaN-based LED leads to an increase in electroluminescent intensity.

Integrated light-emitting diodes grown by MOVPE for flat panel displays

Integrated light-emitting diodes (LEDs) that operate in the UV spectral region were fabricated using GaN layers grown on sapphire substrates by metal-organic vapor phase epitaxy (MOVPE). Schottky-type LEDs with a simple structure were realized. The near-band-edge emission of GaN was observed in the electroluminescent spectrum with reversed bias under pulsed voltage conditions. The light-emission and electric characteristics of the LEDs are discussed.

Temperature dependence of penetration and coherence lengths in lead nanowires

Magnetization curves well belowTc of a lead nanowire array electrodeposited under pulsed voltage conditions areconsidered. Numerical simulations based on a two-dimensional resolution (2Dmodel) of the Ginzburg–Landau (GL) equations for cylindrical configurationshave also been developed. By freely adjusting the GL phenomenological lengthsλ(T) and ξ(T), the experimental magnetization curves are reproduced to within a 10% error margin. The 2Dmodel also allows us to check the cylindrical symmetry of the obtained configurations. Beyond theexperimental–theoretical agreement, the question of whether the GL model remains valid far belowTc is also addressed. The temperature dependence of the adjusted characteristic lengths iscompared with different theoretical and empirical laws. The most satisfactory agreement isachieved for the Gorter–Casimir two-fluid model. A comparison with a lead nanowire arrayelectrodeposited under constant voltage conditions allows us to distinguish both samples interms of their electronic mean free paths. The characterization of the latter quantitiesconcurs perfectly with the experimental expectation given the different electrodepositiontechniques.

The nature of divergent-field surge-voltage endurance in epoxy resin

An experimental study has been conducted to quantify the voltage endurance of electrical grade epoxy resin insulation when subjected to pulse voltages in a divergent field. Voltage endurance has been quantified as a function of pulse width, repetition rate, and polarity. Supporting measurements of free radical generation have been made by electron paramagnetic resonance (EPR), and the progress of the aging mechanism tracked by sensitive photonic emission measurements. The results suggest (at least for positive polarity) that estimates of endurance under pulse voltage conditions can be made from conventional power frequency data, However, it is shown that a correction is necessary to allow for the effects of waveform, and a theory is advanced for that purpose.

Time‐domain analysis of kerr electro‐optic cells for high‐voltage pulse measurements

AbstractThe time‐domain behavior of Kerr modulators operating under pulse voltage conditions is analyzed and discussed. Comparison with the ordinary quasistatic approach is established, showing the inadequacy of the latter. © 1994 John Wiley &amp; Sons, Inc.

Measurements of discharge parameters of the ion source at high potential

The present measurement system is composed of signal preprocessors, an A/D conversion card, optical fibers, a microcomputer, and an interface. After discharge parameters of an ion source at high potential, i.e., analog signals, are preprocessed by means of LPF, amplitude limit, and normalization, they are changed into digital signals by A/D conversion. The digital signals are transferred through optical fibers to low potential, then they are gathered, processed, or stored by the microcomputer. The system can measure eight analog signals at high potential through scanning. Each measurement will take about 160 μs with a precision of ±1 LSB, i.e., ±0.4% maximum relative error at full range. Measurements of discharge parameters of the ion source at high potential were made for a steady state ion source and a high current pulse ion source successively, whose results are in good agreement with practical cases. The formation and propagation of interference and approaches of anti-interference under high current and high pulse voltage conditions are briefly described in the present article.

Evaluation of ultramicroelectrodes for the detection of metal ions separated by capillary electrophoresis

Carbon-fiber, platinum, gold, and mercury films deposited on a gold substrate were evaluated for amperometric detection of metal ions under constant- and pulsed-voltage conditions. The carbon electrodes were rods 10 μm×250 μm long, and the other electrodes were disks 10-25 μm in diameter. Detector response was not reproducible for solid electrodes operated under constant voltage, but was considerably improved for mercury film electrodes. Detection of 14 test metal ions separated in a 25-μm capillary gave detection limits in the range of 10 amol to 50 fmol without removal of background signal from oxygen