Arcing Model of a Disconnector and its Effect on VFTO

In the computational process of very fast transient over-voltage （VFTO）, it is essen-tial to find an accurate model for a gas insulated substation. The arcing model of the disconnector is particularly important. The general arcing model is not able to give a good description of the arc development process. In this paper, based on the physical process of arcing and existing arc models （the exponential time-varying resistance model and the segmental arcing models）, a dy- namic arcing model is proposed, which is divided into two stages before and after the zero crossing. The dynamic arcing model combines hyperbola time-varying resistance and the Mayr model to describe the dynamic process of arcing. The present paper creates an arc model blockset upon the Matlab/Simulink software platform. Moreover for a specific 1100 kV station, VFTO is simulated in detail based on different arcing models. It is demonstrated that the dynamic arcing model can describe the physical arc process precisely and is useful for improving the accuracy of VFTO simulations.

Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low- voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.

Numerical Simulation of Gas Flow During Arcing Process for 252 kV Puffer Circuit Breakers

A numerical simulation model for 252 kV puffer circuit breaker is constructed, by using a proven commercial computational fluid dynamics （CFD） package, PHOENICS. The model takes into account the moving parts in the circuit breaker, turbulence enhanced momentum and energy transport, radiation transport. The arcing process in a SF6 puffer circuit breaker with two hollow contacts is simulated under different conditions, and the simulation results are verified with experimental results. Through simulation, the pressure, temperature and velocity in the arc quenching chamber can be obtained. The simulation model is also capable of predicting the influence of design parameters variations on breaker performance, and can thus help to reduce the number of short-circuit tests during the design stage.

Dynamic physical characteristics of DC arc on arcing horn for HVDC grounding electrode line

The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fault arc and pantograph-catenary arc.In this work,an experimental platform for the DC arc on the arcing horn was built,and mechanisms of the arc column short circuit and arc root movement were studied.This work further analyzes the characteristics and mechanisms of the arc motion when wind speed and direction,magnetic field and the expansion angle of the electrode are varied.Arc root movement is more likely to occur at the upper electrode.There is a competitive relationship between arc expansion and the transferring effect.The effect of wind on the arc column is greater than the effect on the arc root.The magnetic field has a significant driving effect on both the arc column and the arc root.The research results provide a comprehensive experimental basis for forther probing the method of DC arc suppression,and the improvement of the arcing horn.

Research on the energy consumption mechanism and characteristics of the gallium indium tin liquid metal arcing process

For high-voltage direct current(HVDC)power grid transmission with higher voltages,the energyconsuming branch of the DC circuit breaker is required to dissipate huge energies of more than megajoules in a short time in the case of a fault and short circuit.The requirements for huge volume and weight are difficult to meet with energy-consuming equipment based on ZnO.In this paper,a new energy consumption method is proposed based on gallium indium tin(GaInSn)liquid metal in the arcing process,and a test platform with adjustable short-circuit current is built.The mechanism triggering GaInSn liquid metal arcing energy consumption is studied.It is found that short-circuit current and channel aperture are the key parameters affecting the energy consumption of liquid metal arcing.The characteristics of GaInSn liquid metal energy consumption are investigated,and four stages of liquid metal energy consumption are found:oscillatory shrinkage,arc breakdown,arc burning phase change and arc extinction.The influence of short-circuit current and channel aperture on the energy consumption characteristics of GaInSn liquid metal is investigated.To further explore the physical mechanism of the above phenomena,a magneto-hydrodynamic model of energy consumption in the GaInSn liquid metal arcing process is established.The influence of short-circuit current and channel aperture on the temperature distribution of the liquid metal arc is analyzed.The mechanism of the effect of short-circuit current and channel aperture on peak arc temperature and the temperature diffusion rate is clarified.The research results provide theoretical support for this new liquid metal energy consumption mode DC circuit breaker.

Pressure Rise in Electrical Installations due to Internal Arcing in CO2 as Insulating Gas

Internal arcs cause a rapid increase in pressure in electrical installations. The type of insulation gas has influence on pressure development. Typically SF6 is used incompact metal-clad switchgear, however, it has a high global warming potential. Because of this, the replacement of SF6 by alternative gases such as CO2 is under discussion. The pressure developments in a closed vessel filled with air, SF6 and CO2 are measured and compared. During internal arcing in gas-insulated switchgear, overpressure causes a rupture of a burst plate and hot gas escapes into the surrounding room mixing with air. In order to predict the pressure development in electrical installations reliably, the portion of energy causing pressure rise, arc voltage as well as reliable gas data i.e., thermodynamic and transport properties, must be known in a wide range of pressure and temperature. These data are up to now not available for CO2/air mixtures. The thermodynamic properties are directly calculated from the number densities, internal partition functions and enthalpies of formation. The transport coefficients are deduced using the Chapman-Enskog method. Comparing measured and calculated pressure developments in a test arrangement demonstrates the quality of the calculation approach.

Calculation of Nozzle Ablation During Arcing Period in an SF_6 Auto-Expansion Circuit Breaker

The nozzle ablation process is described as two phases of heat and ablation in the interruption for an SF6 circuit breaker in this paper. Their mathematical models are established with the Fourier heat conduction differential equation respectively. The masses of nozzle ablation with different arc durations and arc currents are calculated through the model of the nozzle abla- tion combined with an MHD （magneto-hydrodynamic） arc model. The time of the temperature rise on the inner surface of the nozzle under a given energy flux and of reaching the pyrolysis temperature under different energy fluxes is respectively analyzed. The relations between the mass of nozzle ablation and breaking current and arc duration are obtained. The result shows that the absorbing energy process before the nozzle ablation can be neglected under the condition of the energy flux entering into nozzle q 〉 10^9 W/m^2. The ablation is the severest during the high-current phase and the ablation mass increases rapidly with the breaking current and with arc duration respectively.

Analysis of the Carbon Nano-Structures Formation in Liquid Arcing

Graphite electrodes were used for the direct current （DC） arc discharge in water. And high-resolution transmission electron microscopy （HRTEM） was used to investigate the products. Based on the experimental phenomena and nano-structure products, arc plasma characteristics in water were analyzed theoretically. Two growth regions and relevant growth modes were proposed to interpret the formation mechanisms of nano-structures by arc discharge in water. Furthermore, liquid nitrogen and cross magnetic field was applied to change the arcing state respectively, and new carbon nano-structures were obtained. Their formation mechanisms were also analyzed correspondingly.

ARCS动机模型与情景模拟教学法在麻醉学教育领域的应用效果

随着医学教育的不断发展,传统教学方法已难以满足现代麻醉学教育的需求。因此,探索新型教学策略,以激发学生的学习兴趣和积极性,提升教学质量,成为当前麻醉学教育领域的重要课题。本研究旨在探讨ARCS动机模型与情景模拟教学法在麻醉学教育领域的应用效果。通过对ARCS动机理论及情景模拟教学方法的理论梳理,以及对麻醉学科的教学现状和所面临挑战的分析,深入讨论将ARCS动机模型应用于麻醉学课程设计中的策略,并详细说明实施情景模拟教学的具体做法。这种方法不仅能够有效激发学生的学习兴趣,提高其专业知识和技术能力的掌握水平,而且还能增加教师对于教学过程的满意度,从而显著提升整体教学质量。

Processing,microstructure,and mechanical properties of wire arc additively-manufactured AZ91 magnesium alloy using cold arc process

Thin walls of an AZ91 magnesium alloy with fine equiaxed grains were fabricated via cold arc-based wire arc additive manufacturing(CA-WAAM),and the droplet transfer behaviours,microstructures,and mechanical properties were investigated.The results showed that the cold arc process reduced splashing at the moment of liquid bridge breakage and effectively shortened the droplet transfer period.The microstructures of the deposited samples exhibited layered characteristics with alternating distributions of coarse and fine grains.During layer-by-layer deposition,the β-phase precipitated and grew preferentially along grain boundaries,while the fineη-Al_(8)Mn_(5)phase was dispersed in the α-Mg matrix.The mechanical properties of the CA-WAAM deposited sample showed isotropic characteristics.The ultimate tensile strength and elongation in the building direction(BD)were 282.7 MPa and 14.2%,respectively.The microhardness values of the deposited parts were relatively uniform,with an average value of HV 69.6.

致敬温哥华文化脉络 ARC'TERYX始祖鸟北京三里屯店

ARC'TERYX始祖鸟门店遍布全球。身为行业的顶尖领导者,始祖鸟带着源于温哥华的山脉森林基因与当代美学,登陆北京地标三里屯核心商圈,锁定高端消费市场,掀起户外运动的热潮。设计以山脉森林的探险之旅为切入点,致敬温哥华文化脉络,通过与自然的持续对话,引导消费者在多元化的主题空间中漫游,给户外爱好者和资深鸟粉带来前所未有的全新体验。

基于ARCS动机模型的小学信息科技探究式教学设计与实践

基于ARCS动机模型,深入探讨了小学信息科技探究式教学的设计与实践。ARCS动机模型作为一种深受认可的教学设计理论,通过四大关键要素——注意、切身性、自信、满意,有效激发并持久维持学生的学习动机。通过分析ARCS动机模型在教学中的应用原理,以及其与小学信息科技教学的契合度,指出将ARCS动机模型应用于小学信息科技教学中,能够有效提升学生的学习动机,促进学生的全面发展。

高职院校学生ARCS学习动机模型的探索与实践

本研究利用发放调查问卷、查阅文献和现场访谈等方法,结合ARCS学习动机模型,对现阶段高职院校学生学习现状进行调查研究。结合调查分析结果,借助ARCS学习动机模型进行教学设计并实施教学,调动学生学习的积极性,激发学生的学习动机,提高了学生的学习兴趣和学习能力。

高等教育线上线下混合教学模式探索和实施

根据新工科建设方案及理工科专业课程特色,教学过程以问题前导,以任务驱动,以思政案例贯穿,以多层级路径开展,以学生为中心。本文根据高等理工科专业基础课程特点,给出了基于BOPPPS(Bridge in引导、Objective学习目标、Pre-assessment前测、Participatory learning参与式学习、Post-assessment后测、Summary总结)模型和ARCS(Attention注意、Relevance关联、Confidence信心和Satisfaction满意)模型的混合式教学流程和活动。分析了课程整体设计思路及教学模型、学情分析与目标设定、课程内容设计与资源整合、教学过程与实施方法、学习评价与教学反馈、课程成效等内容,包括教学模型、评价体系、线上线下教学过程及实施办法和效果,通过师生互动和学生反馈意见,不断更新各个平台的教学资源,改进教学方法,持续提升课程教学质量。

小花楼织机织造技艺数字化教育设计研究

目的为了缓解小花楼织机织造技艺面临失传的问题,根据ARCS动机理论展开织造技艺数字化教育的设计研究,提升学习者在体验过程中的注意力和理解力,增强其掌握织造技艺的自信和满足感。方法结合ARCS动机理论和小花楼织机的织造技艺知识点,将数字化教育划分为三个教育单元,即小花楼织机的交互及展示设计、小花楼织机结构的模块化设计、实物模型控制及模拟设计,并在Unity平台中展开Arduino开发板以集成设计,由浅入深地构建数字化教育场景。结论对照实验结果表明,基于ARCS动机理论的数字化教育方式具有可行性和实践性,小花楼织机织造技艺的知识可达性和教育互动性有了显著提高,为蜀锦织造技艺的传承和发展提供了一定的参考价值和实践意义。

挖掘机液压混合动力系统跟踪控制研究

由于挖掘机混合动力系统参数的不确定性和系统的非线性给挖掘机的跟踪控制带来了巨大的困难。对此,构建了挖掘机液压混合动力系统模型,并采用改进的自适应鲁棒控制(ARC)实现挖掘机液压混合动力系统的跟踪控制。根据挖掘机液压混合动力系统,对液压系统、挖掘机动力学和发动机进行数学建模。利用线性稳定反馈控制规律,采用改进的自适应鲁棒控制,使挖掘机液压混合动力系统具有足够大的反馈增益。最后对斗杆、动臂和铲斗的倾角进行跟踪仿真实验,给出了系统模型位置和速度的跟踪误差,并与PI控制进行比较分析。结果表明:相比于PI控制,ARC控制下的斗杆、动臂和铲斗倾角的最大振幅波动率和倾角的波动范围都有所降低,且回转位置和速度的跟踪误差超调较小。说明采用ARC控制的挖掘机混合动力系统控制方法,能够更好的补偿系统模型的非线性,具有较好的控制稳定性以及跟踪精度。

OBE-ARCS导向的化学工程专业学位研究生课程体系建设和课堂教学模式创新

立足学校理工交叉学科特色,化学工程专业以OBE理念为指导,融合产学研用多要素,对专业学位研究生的核心课程体系进行重构;基于ARCS动机模型,创新研究生课程教学模式;协同专业、课程和教材思政,构建一体化育人机制;依托工程实践基地建设,强化理论与工程实践的结合。基于以上举措构建的“四维一体”育人模式将研究生的知识学习、能力培养、意识强化、专业素养提升紧密融合,在培养高质量应用型人才方面取得了显著成效。

基于向量法近似的圆弧SAR成像方法

Arc SAR是一种能够在短时间内可重复扫描360°的雷达成像技术,具有重访周期短,观测范围广等优点,在边坡检测、山体滑坡等场景中有着广泛的应用前景。在Arc SAR模式下雷达随着机械臂进行圆周运动来形成合成孔径,因其运动轨迹不是直线,所以不能直接运用传统直线导轨的成像方法,需为Arc SAR设计新的成像算法,然而现有的成像方法不能很好地平衡精度和复杂度。在距离多普勒算法中,由于采用泰勒展开来近似斜距,导致成像质量不佳,或是需采取分割策略进行成像。因此,提出了一种新的距离多普勒算法,利用目标与雷达的向量关系进行近似,求得了近似斜距表达式,继而得到了距离多普勒域的信号表达式。基于这一表达式,提出了相应的相位误差补偿方法,完成了图像聚焦。最后通过点目标仿真验证了该算法的有效性。

基于ARCS模型的翻转课堂教学设计

以“取样定理”为例,提出采用ARCS模型进行翻转课堂教学设计的案例。教学内容设计注重核心价值观的传播,从取样定理形成的历史脉络引出课程思政;运用多种教学手段,提升学生注意力;重视学习内容的关联设计,学生端倚重信息技术应用,及时反馈,提升学生自信度;学习评价注重应用性,提升学习满意度。教学实施结果表明,该教学设计能调动学生的课堂热情,师生满意度高。

ARCS模型视角下高职英语教学资源建设与应用研究

基于ARCS模型视角的高职英语教学资源平台建设和应用,坚持以学习者为中心,以整体化、系统化、标准化、科学化、合作性、共享性、循环性改进为原则,围绕高职学生岗位英语语言技能和职业素养目标,构建高职英语课程教学资源库和教学资源共享平台,完善学习成果考核评价体系,建立质量评估和诊改机制,多举措提升教改能力,促进数字化技术与教学改革实践深度融合与双向赋能。