Simulation of arcs for DC relay considering different impacts

Recently DC relay has been concerned as a key component in DC power distribution,management and control systems like aircraft,new energy vehicle,IT and communication industries.Ordinarily,magnetic force and contact moving speed have great influence on arc behaviours in the breaking process.This paper focuses on the numerical investigation of arc during the contact opening process in a real 400V/20 A DC relay product coupling with an inductive load circuit.A 3D air arc model based on the magneto-hydrodynamic theory was built and calculated.A method coupling different computational software was used to take the nonlinear permanent magnet and contact opening process into consideration simultaneously.Arc behaviours under different magnetic field and contact opening speed were presented and discussed carefully.It has been found that the increase of the magnetic field is beneficial to the quick build-up of arc length and voltage.Arc breaking duration becomes shorter with the increase in contact opening speed from 63.5 rad s^-1 to 94.5 rad s^-1,such reduction is less significant with an increase of opening speed from 94.5 rad s^-l to 118.5 rad s^-1.

Influence of the axial magnetic field on sheath development after current zero in a vacuum circuit breaker

After current zero,which is the moment when the vacuum circuit breaker interrupts a vacuum arc,sheath development is the first process in the dielectric recovery process.An axial magnetic field（AMF） is widely used in the vacuum circuit breaker when the high-current vacuum arc is interrupted.Therefore,it is very important to study the influence of different AMF amplitudes on the sheath development.The objective of this paper is to study the influence of different AMF amplitudes on the sheath development from a micro perspective.Thus,the particle in cell-Monte Carlo collisions（PIC-MCC） method was adopted to develop the sheath development model.We compared the simulation results with the experimental results and then validated the simulation.We also obtained the speed of the sheath development and the energy density of the ions under different AMF amplitudes.The results showed mat the larger the AMF amplitudes are,the faster the sheath develops and the lower the ion energy density is,meaning the breakdown is correspondingly more difficult.

Chromatic processing for feature extraction of PD-induced UHF signals in GIS

Partial discharge(PD) detection is an effective means of discovering insulation faults in gas-insulated switchgear(GIS). One of the most extensively used methods in PD detection has historically been the ultrahigh frequency(UHF) method. This study evaluates the chromatic processing methodology and its key factors for feature extraction of UHF signals in GIS. Three types of artificial defects are installed in the GIS tank at 0°, 90°, and 180°, respectively. The features of the UHF signals are extracted in the chromatic space, and PD discrimination of the defects is achieved. The influences of processors are studied before the feature selections are suggested. The time-stepping method is proposed to determine the rules of UHF signal frequency characteristics that vary with time. Finally, the process and options of the chromatics-inspired methodology are summarized.

Numerical analysis on the effect of process parameters on deposition geometry in wire arc additive manufacturing

Here we develop a two-dimensional numerical model of wire and arc additive manufacturing(WAAM)to determine the relationship between process parameters and deposition geometry,and to reveal the influence mechanism of process parameters on deposition geometry.From the predictive results,a higher wire feed rate matched with a higher current could generate a larger and hotter droplet,and thus transfer more thermal and kinetic energy into melt pool,which results in a wider and lower deposited layer with deeper penetration.Moreover,a higher preheat temperature could enlarge melt pool volume and thus enhance heat and mass convection along both axial and radial directions,which gives rise to a wider and higher deposited layer with deeper penetration.These findings offer theoretical guidelines for the acquirement of acceptable deposition shape and optimal deposition quality through adjusting process parameters in fabricating WAAM components.

Research on vibration energy harvesting technology of power equipment based on alternating magnet array

Vibration with a frequency of 100 Hz is widely distributed in the power equipment,and it can provide a new way to supply energy for sensors by vibration energy harvesting.The vibration energy harvesting method based on electromagnetic induction principle was studied through the arrayed structure of magnets and coils.Static magnetic field models were established for four magnet array structures and it was found that the alternating magnet array has the largest magnetic flux and magnetic flux gradient.Based on the alternating magnet array,prototypes of energy harvester with vertical and parallel movement mode were proposed.Through structural parameter optimisation analysis,two different energy harvesters were fabricated and it was found that the energy harvester with a parallel movement mode has better output performances.The energy harvester could provide output voltage/current and power of 8.35 V/17.39 mA and 15.13 mW(matched resistance is 200Ω)at an acceleration of 5 m⋅s^(-2).The 100 mF capacitor could be charged to 2.72 V within 300 s,and the final voltage of the capacitor is greater than 3 V,which could sustainably drive commercial wireless temperature/humidity sensors.

A fuse-based DC circuit breaker with vacuum interrupter enhanced by an external transverse magnetic field

Due to the increasing power system capacity,the interruption of large fault currents has gradually become a major challenge in power systems.At the moment,such currents are interrupted mainly via circuit breakers based on the method of active current commu-tation.However,these types of circuit breakers tend to be costly and oversized.One possible alternative—a fuse-based circuit breaker with current commutation process enhanced by an external transverse magnetic field(ETMF)—is proposed by the authors.Its main advantage lies in the fast current commutation achieved by an ETMF-enhanced three-stage increase of the vacuum arc voltage.The study of the current commutation process is mainly represented by the authors,and the influencing factors of the current commutation—contact opening speed and ETMF current—are discussed.At last,the proposed circuit breaker is verified by an experiment,whose results show that a short-circuit current of 42 kA can be interrupted within just 2 ms.

Multicomponent SF6 decomposition product sensing with a gas-sensing microchip

A difficult issue restricting the development of gas sensors is multicomponent recognition. Herein, a gas-sensing (GS) microchip loaded with three gas-sensitive materials was fabricated via a micromachining technique. Then, a portable gas detection system was built to collect the signals of the chip under various decomposition products of sulfur hexafluoride (SF6). Through a stacked denoising autoencoder (SDAE), a total of five high-level features could be extracted from the original signals. Combined with machine learning algorithms, the accurate classification of 47 simulants was realized, and 5-fold cross-validation proved the reliability. To investigate the generalization ability, 30 sets of examinations for testing unknown gases were performed. The results indicated that SDAE-based models exhibit better generalization performance than PCA-based models, regardless of the magnitude of noise. In addition, hypothesis testing was introduced to check the significant differences of various models, and the bagging-based back propagation neural network with SDAE exhibits superior performance at 95% confidence.

Detection of decomposition products of SF6/air gas mixture by electron attachment mass spectrometry

Sulphur hexafluoride(SF_(6))is widely used in gas insulation,and its decomposition products can be used to diagnose potential insulation failures.Quick and accurate detection of decomposition products can help to understand equipment-operating conditions in time.In this study,the decomposition products of SF_(6)/air gas mixtures under different pulsed discharge voltages were studied.It was found that the main products were SOF_(2),SO_(2)F_(2),SO_(2),CF_(4)and SOF_(4),and the yields of SOF_(2),SO_(2)F_(2),SO_(2)and SOF_(4)increased with the number of discharge pulse.The productive rate of SOF_(2),SO_(2)and SOF_(4)were positively correlated with the discharge voltage,and when the discharge voltage increased from 5 to 15 kV,their yields after 50,000 discharges increased by 49%,120%and 1100%,respectively.The productive rate of SOF_(2)and SO_(2)were positively correlated with the proportion of air in the gas mixtures while that of SOF_(4)was opposite.When the proportion of air increases from 0%to 90%,their yields after 50,000 discharges became 270%,3169%and 10%of the originals,respectively.In addition,the productive rate of SO_(2)F_(2)was not affected by discharge voltage and the proportion of air in the gas mixtures.SO_(2)F_(2),SOF_(2),SOF_(4)and SO_(2)can be used as the basis for judging the discharge failures and the discharge degree of power equipment.

Hybrid piezo/triboelectric nanogenerator for stray magnetic energy harvesting and self‐powered sensing applications

Stray magnetic fields with a fixed frequency of 50/60 Hz are ubiquitous in buildings,factories,and power system equipment.Researchers are increasingly focusing on har-vesting electrical energy from stray magnetic fields to provide sustainable energy for the Internet of Things(IoT)devices.Magneto‐mechano‐electric energy conversion is the most efficient way to convert low‐frequency stray magnetic fields into electricity.In this study,we proposed a hybrid piezo/triboelectric nanogenerator(HP/TENG)on the basis of a cantilever beam to use stray magnetic fields from the surrounding environment.The hybrid nanogenerator provided high output voltage/current and power of∼176 V/375μA and 4.7 mW(matched impedance of 20 kΩ)in a magnetic field environment of 4 Oe.The device provided a stable 3.6 V direct current output by incorporating energy management circuitry to sustainably drive power to commercial wireless temperature/humidity sensors.The HP/TENG has a significant application potential in IoT,which can use stray magnetic energy and a power wireless sensor system.