Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column's diameter gradually becomes wider. The 11.14 V–12.33 V drops along the17 μm space charge layer away from the cathode(65.5 k V/m–72.5 k V/m) when the current varies from 20 k A–80 k A.The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core,but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment.

Simulation and Experimental Analysis of Arc Motion Characteristics in Air Circuit Breaker

In this paper, to simulate the arc motion in an air circuit breaker （ACB）, a three- dimensional magneto-hydrodynamic （MHD） model is developed, considering the influence of ther- mal radiation, the change of physical parameters of arc plasma and the nonlinear characteristic of ferromagnetic material. The distributions of pressure, temperature, gas flow and current density of arc plasma in the arc region are calculated. The simulation results show some phenomena which discourage arc interruption, such as back commutation and arc burning at the back of the splitter plate. To verify the simulation model, the arc motion is studied experimentally. The influences of the material and position of the innermost barrier plate are analyzed mainly. It proved that the model developed in this paper can efficiently simulate the arc motion. The results indicate that the insulation barrier plate close to the top of the splitter plate is conducive to the arc splitting, which leads to the significant increase of the arc voltage, so it is better for arc interruption. The research can provide methods and references to the optimization of ACB design.

The Influence of Contact Space on Arc Commutation Process in Air Circuit Breaker

In this paper, a 3D magneto-hydrodynamic （MHD） arc simulation model is applied to analyze the arc motion during current interruption in a certain air circuit breaker （ACB）. The distributions of pressure, temperature, gas flow and current density of the arc plasma in the arc region are calculated, and the factors influencing the commutation process are analyzed according to the calculated results. Based on the airflow in the arc chamber, the causes of arc commutation asynchrony and the back commutation are investigated. It indicates that a reasonable contact space design is crucial to a successful arc commutation process. To verify the simulation results, the influence of contact space on arc voltage and arc commutation is tested. This research can provide methods and references to the optimization of ACB design.

Yaxi Brand Lowvolt Frame-type Air Circuit Breaker

The Yaxi brand DW18 series tow-volt frame-type air circuit breakers are made by the Xian Yaxi Electric Appliance Company, using advanced technology. Their technical performance has reached the world advanced level and they have been designated by the State Science and Technology Commission as national key products.

Research on arc root stagnation when small current is interrupted in self-excited circuit breaker

The self-excited DC air circuit breaker(SE-DCCB)has been widely used in urban rail transit due to its excellent stability.It can realize forward and reverse interruption,but has difficulty interrupting small currents due to the phenomenon of arc root sticking at the entrance of the arc chamber in the splitting process,which is known as arc root stagnation.A coupling model of the self-excited magnetic field and magnetohydrodynamics is established for the SE-DCCB with the traditional structure.The magnetic field,temperature and airflow distribution in the arc chamber are investigated with an interrupting current of 150 A.The simulation results show that the direction and magnitude of the magnetic blowout force are the dominant factors in the arc root stagnation.The local high temperature of the arc chamber due to arc root stagnation increases the obstruction effect of the airflow vortex on the arc root movement,which significantly increases the arc duration time of small current interruption.Based on the research,the structure of the magnetic conductance plate of the actual product is improved,which can improve the direction and magnitude of the magnetic blowout force at the arc root so as to restrain the development of the airflow vortex effectively and solve the problem of arc root stagnation when the small current is interrupted.The simulation results show that the circuit breaker with improved structure has a better performance for a small current interruption range from 100 A to 350 A.

高海拔环境下大容量直流空气断路器灭弧性能研究

高原轨道交通和电工产业转型对起关键保护作用的大容量直流空气断路器(LC-DCCB)提出了更高要求,但现有产品在高海拔地区的开断仍存在一定问题。该文以轨道交通用LC-DCCB为研究对象,首先基于磁流体动力学(MHD)理论,考虑湍流效应的影响,对其在高海拔环境下开断18 kA短路电流进行仿真;然后对电弧形态及灭弧室内温度场、电磁场、气流场进行分析,得出高海拔地区空气电弧开断困难的主要原因;最后根据仿真与理论分析,考虑采用合理数量和布局的间插式U型栅片改善电弧开断特性。结果表明:随着海拔的升高,电弧前期运动速度加快,但断路器的灭弧性能降低;在高海拔环境下电弧存在严重的弧根粘滞和弧根拖尾现象,弧根拖尾畸变空间电场,不利于熄弧;同时,在不同海拔环境下,电弧会产生不同程度的反向运动现象,易导致弧后重燃。该研究深入揭示了高海拔环境下LC-DCCB电弧演变过程及复杂开断现象背后的物理本质,可为该类产品研发提供理论指导。

直流空气断路器高海拔环境下电弧重燃现象及其抑制措施

高海拔环境下直流空气断路器(DC ACB)在电弧开断过程中易发生重燃,导致开断失败的概率增加。为了抑制DC ACB高海拔开断时的电弧重燃,以轨道交通用车载DC ACB为研究对象,建立了二维磁流体动力学(MHD)仿真模型,分析了不同海拔下DC ACB中的电弧演变过程,通过增大横向磁场及设置“C”形栅片对其高海拔开断性能进行优化。结果表明增大横向磁场,2 km、3 km海拔下DC ACB不发生电弧重燃,但4 km、5 km海拔下发生电弧重燃。4 km、5 km海拔下,在增大横向磁场的基础上采用含“C”形栅片的改进灭弧室结构,能够使DC ACB在高海拔环境下成功开断。

LW25-252型断路器气动阀体密封圈检修(检验)方法

某220 kV站内进口设备LW25-252型断路器为单台供气式气动机构,内部气动阀由于存在运行时间较长,密封圈老化导致出现气动阀频繁漏气。文章通过研究该站LW25-252型断路器中VA133、VA134型气动阀,经过对气动阀的拆接、工作原理分析以及各部位密封垫作用,确定阀体内活塞杆密封圈为气动阀漏气根源,根据阀体活塞杆结构研制专用工具供拆解、组装阀体,并进一步模拟集中供气模式设计气动阀体检测平台,对修后气动阀进行自测自检,实现对该厂家VA133、VA134型气动阀自拆自修自检,降低对外部厂家援助依赖。

基于有限元法的主断路器断口缺陷分析

为减小产品尺寸,机车车辆主断路器断口间常采用灌封硅凝胶来改善绝缘性能。当灌封胶与灭弧室外壳及外支撑绝缘子间的粘接出现问题时,两个复合界面上将出现缺陷,形成由空气填充的气隙缝。文章针对该现象,预估气隙缝位置及大小并建立仿真模型,计算峰值为138 kV的标准操作过电压(250/2500µs)下该模型电场强度的数值大小和电场分布,着重分析了气隙缝周围的电场畸变。仿真结果表明:灭弧室瓷壳表面较外支撑绝缘子内表面气隙缝的电场强度大,畸变更严重。

多联机空调系统电气设计常见问题探讨

针对多联机空调系统电气设计中的一些常见问题,从室外机配电功率,断路器是否需要设置RCD,断路器降容,电缆敷设及载流量修正和室内机配电方式、控制等方面进行探讨,并给出相应的意见及建议。

ACB电子控制器关键技术研究

提出一种双电源供电的断路器电子控制器电路,增加了系统可靠性。基于低功耗理念,设计了集高精度多路交流信号采集模块、磁隔离型RS 485通信模块、液晶显示与输入模块、中央控制器模块等,经测试系统功耗为0.79 W。相比常规产品最大低功耗提升71%,电流精度最大提升48%。系统采用多任务实时操作系统,通过多路采集模块将电流、电压信号采样,实时计算电流、电压值,具有过载、短路、瞬断、缺相、电流不平衡、电压不平衡等保护特性,同时考虑控制器的热记忆功能,实现了对三相电流信号进行12次谐波分析,MODBUS通信协议的支持。

Influence of the gassing materials on the dielectric properties of air

Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.

超大容量ACB接线端子散热技术研究

分析了万能式断路器(ACB)的温升途径与机理,介绍了当前散热领域的常用技术(热管和导电膏)。结合具体的ACB项目,采用热管和导电膏散热技术,在ACB产品设计中,提高散热性能,控制温升,改善品质,从而提高其工作性能。

磁吹直流空气断路器弧根跃迁及对开断特性的影响研究

直流空气断路器的弧根跃迁与其开断特性有着密切的关系。该文搭建实验平台,采用高速摄像机拍摄电弧演变过程,得到清晰的弧根跃迁图像,观测弧根跃迁过程中的“双弧根”现象。基于磁流体动力学理论,建立二维磁吹直流空气电弧模型。模型中赋入鞘层条件,通过耦合外电路模块模拟实验工况,对开断过程中电弧温度场、气流场及弧根跃迁现象进行分析。在此基础上,完成磁场、烧蚀金属蒸气浓度变化对弧根跃迁及开断特性影响的仿真研究。结果表明:磁场强弱会改变弧柱高温区的运动轨迹,影响前后侧的气流场分布,改变局部区域电导率,产生弧根的停滞与跃迁现象,显著影响断路器的开断性能。外施50m T磁场会发生弧根跃迁现象,弧根跃迁可以减少烧蚀,加速开断,其本质成因是通过“双弧根”完成的。“双弧根”现象是由于引弧板表面电导率增大,在其表面形成新的导电斑点形成的。烧蚀产生的金属蒸气不总是阻碍熄弧,当灭弧室中铜蒸气浓度达到50%~60%时,出现弧根跃迁,减少燃弧时间,有利于开断。

低压智能ACB中接地保护准确性研究

接地故障保护功能是智能ACB中根据客户需求附加的保护功能,其动作的准确性直接影响配电系统的安全与可靠。介绍了常见配电系统的接地信号的两种常用获取方式:矢量和与地电流,从理论上分析了影响接地保护准确性的关键因素。结合这两种接地方式,参照相关标准,讲述了相应的软硬件解决方案,其中包括接地故障电流传感器的选择、信号滤波放大处理电路、软件编程等。最后采用FFT算法提取出了故障信号基波进行保护处理。经过对样机的验证,两种接地方式所采取的解决方案均提高了接地保护的准确性,从而进一步保证了配电系统安全可靠地运行。

中压直流空气断路器短路分断电弧特性研究

基于磁流体动力学理论,考虑空间湍流影响,搭建多物理场耦合中压直流空气断路器大空间、全动态电弧模型,对中压直流空气断路器短路开断电弧进行仿真研究。结果表明:中压直流空气断路器在短路开断电弧过程中,弧根转移会导致弧压、弧流及功率出现波动,电弧弧根出现黏滞现象;栅片间弧柱区会产生电弧反向现象;电弧熄灭速度与外施磁场大小成正相关,但变化趋势并不呈现线性关系。为解决中压直流空气断路器短路电流开断困难问题,提供理论依据。

一起35 kV SF_(6)断路器气压低频繁告警的故障分析

SF_(6)气体绝缘高压断路器,其气压会因为泄漏和温度等原因而发生变化,对变电站安全运行造成影响。文章针对案例进行具体分析,在气压低频繁告警的故障发生时,应对断路器进行检漏检查,快速定位故障点,并加强在日常运维和检修过程中的防范。

电力机车用22CB系列真空断路器典型漏风故障分析

真空断路器用于接通及断开25 kV接触网与电力机车间的电路,它是机车电源的总开关和保护设备,研究分析真空断路器故障现象及产生原因能够对生产商制造工艺和机务段使用维护提供宝贵的指导经验。漏风故障是真空断路器主要的故障类型,文中通过对电力机车用22CB系列真空主断路器4起典型的漏风故障进行分析,对现有的真空断路器生产检修工艺及管理提供改善建议,从而降低产品故障率,提升可靠性,保障电力机车安全稳定运行。

万能式断路器综合性能检测系统研制

介绍了一套基于虚拟仪器技术的万能式断路器综合性能检测系统设计方案。系统以工控机为控制核心,配置数据采集卡、信号调理电路和三相大电流发生器、气动夹具等组成系统硬件平台,利用LabVIEW软件开发相关测试及数据处理软件,实现数据采集和处理,满足了万能式断路器综合性能检测的需要。实际运行表明,该系统具有稳定可靠、操作方便、维护简单的特点。

一起500kV SF_6断路器爆炸事故的分析

针对S变电站发生的一起500 kV SF_6断路器爆炸事故,该文根据保护动作、现场检查和后续试验情况对事故原因进行分析。最终,推定该事故起因为断路器的绝缘拉杆在制造工艺上存在缺陷,设备运行时,该缺陷会导致产生局部放电,进而逐步破坏内部绝缘,最终导致击穿并引发设备爆炸。据此,对与该故障设备同型号、同批次的瑞典P公司产绝缘拉杆进行全部召回,并更换为试验证明绝缘性能优良的瑞士T公司产绝缘拉杆,以避免类似事故再次发生。