SF6断路器空载介质恢复特性数值模拟中的耦合计算方法

SF6高压断路器空载下介质恢复特性的数值模拟取决于液压操动机构的输出动力特性、开断过程中灭弧室内气流场的分布以及电场总分布.传统方法对介质恢复特性的数值模拟是先分别对上述三部分进行数值计算,然后根据三部分的数值计算结果计算介质恢复特性.本文以介质强度的计算为纽带,将三者联系起来,首先建立了对介质恢复特性进行数值模拟的耦合方程,然后在液压机构操动力的驱动下,对每一行程步距通过耦合方程,计算每一步距下的液压操动机构的输出特性、灭弧室内气流场与电场的分布及介质恢复强度,最后求得全行程下的介质强度恢复特性.通过空载开断过电压的校核,证明所求得的介质恢复特性满足对该断路器空载开断能力的要求.     

触头烧损对SF_6断路器介质恢复特性的影响

为研究126 kV SF6断路器在多次切合补偿设备过程中的介质恢复特性,根据电流较小时电离不充分的特点,建立了SF6双温度电弧等离子体模型并将它应用到气流场计算中。根据多次开断过程中静弧触头的实际烧损情况,建立了灭弧室内电场及气流场的数学模型。采用流注理论临界击穿判据计算开关的介质恢复特性曲线并分析触头烧损对其影响。在此基础上,考虑动弧触头对静弧触头的挤压磨损,通过对灭弧室进行3维电场分析,分析了不同烧损情况对电场分布的影响。研究结果表明:触头烧损对临界击穿电压的影响十分明显,当开距为67 mm时,烧损角θ=60°的临界击穿电压与无烧损情况相比降低了180%;随着θ增大,静弧触头表面的电场畸变愈加严重,当烧损角θ=80°时,静弧触头表面某点的电场强度是无烧损情况下的8.91倍。根据以上分析,提出了改善SF6断路器中触头烧损对介质恢复特性影响的方法。     

压气式SF_6断路器无载开断过程中触头堵塞现象的研究

利用数值分析,研究了SF_6断路器在无载开断条件下触头堵塞对灭弧室内气流场的影响,讨论了触头堵塞效应与介质强度恢复的关系。     

弧触头烧蚀程度对灭弧室内短路开断过程多物理场的影响

为研究SF6断路器开断过程中弧触头烧蚀程度对灭弧室内多物理场变化的影响,建立了弧触头接触行程分别减小0、5、10和15Smm下灭弧室内开断过程的多物理场耦合仿真模型,获得了短路电流开断过程中灭弧室内温度、气流和电场分布特性。计算结果表明：开断过程中,弧道最高温度出现在弧根处,其值随弧触头烧蚀程度变化不大;随着弧触头烧蚀程度的加剧,SF6气体最高速度不断减小,吹弧效果减弱;最大场强集中在静弧触头端部或动弧触头弧角处,且随弧触头烧蚀程度加剧而畸变更严重。基于此,根据流注理论的气体击穿判据计算了不同弧触头烧蚀程度下SF6介质恢复特性,发现当弧触头接触行程减小15 mm时,临界击穿电压低于瞬态恢复电压,触头间隙可能再次击穿造成电弧重燃。研究结果可为SF6断路器电寿命退化机理提供理论支撑。     

高压SF6自能膨胀式断路器无载开断过程中灭弧室内气流场的数值分析

本文以质量守恒定律、动量守恒定律和能量守恒定律为基础,数值分析了ＳＦ６自能膨胀式断路器无载开断过程中灭弧室内的气流场。气流场的变化分为三个阶段。在第一阶段中,膨胀室内气体压力、密度增加,为下一阶段吹弧做好准备。在第二阶段中,动静弧触头之间的区域形成滞止区,气流场在空心动弧触头及导电杆内达到超音速流,这些有利于电弧的熄灭。在第三阶段中,主喷口扩张区与喉部之间存在超音速流,影响介质恢复强度;在静弧触头     

4种典型交流滤波器断路器灭弧室电场分析

内部绝缘不足是引起换流站交流滤波器(alternating current filter,ACF)断路器发生爆炸事故的原因之一,为此开展了典型ACF断路器灭弧室内部电场分布的仿真研究。首先,基于电场数值分析理论,采用Solidworks和ANSYS软件建立了4种典型550 kV ACF断路器三维数值仿真模型;然后,仿真分析了弧触头网格剖分尺寸对灭弧室电场计算结果的影响,基于仿真数据对比分析了4种结构的ACF断路器在熄弧后开断过程中灭弧室的电场分布和不均匀系数,评估了断路器灭弧室内部相对绝缘强度;最后,分析了燃弧时间和平均开断速度对典型ACF断路器灭弧室电场的影响,初步提出了优化措施。仿真分析结果表明:弧触头的剖分尺寸可取0.2~0.5 mm;4种典型结构ACF断路器灭弧室内电场分布属于稍不均匀场,在正常开断情况下都能满足绝缘裕度要求;增加燃弧时间和平均开断速度,能够减小典型ACF断路器灭弧室各部件最大场强,提高绝缘裕度。     

高压SF_6断路器灭弧室内激波的混沌特性

研究灭弧室内气流场的特性对高压SF6断路器的优化设计具有重要的意义。为此通过数学变换,采用压力方程代替质量守恒方程,建立一维可压缩气流场物理数学模型,基于有限体积法求解容性小电流开断下高压SF6断路器灭弧室内气流场,得到马赫数分布以及激波产生处的密度、压力、速度与温度等主要气流参数的分布。利用分离变量法对灭弧室内气流运动方程的基本解进行求解研究,得到灭弧室内存在由混沌态过渡到周期运动的非线性动力学行为描述。结果表明:激波的不稳定性是造成混沌现象的根源之一,激波处混沌行为有利于SF6断路器的开断。     

高压SF_6/N_2混合气体断路器冷态介质恢复特性计算分析

基于N-S方程与拉氏方程对空载SF_6/N_2混合气体断路器灭弧室内的气流场和电场建立数学模型,计算断路器开断过程的气流特性和电场分布,分析混合比对触头间介质强度薄弱区域的气流特性影响。提出SF_6/N_2混合气体的击穿判据,计算不同SF_6/N_2混合比、开断速度及充气压力的介质恢复强度,研究断路器重击穿现象,结合SF_6/N_2混合气体液化温度、全球变暖潜能值,提出适用于断路器空载操作要求的SF_6/N_2配比方案。计算结果表明:在开断过程气流特性的作用下,介质恢复强度曲线呈现随开距增加先上升后下降,再继续升高的趋势。当灭弧室内触头间开距为14mm时,20%SF_6/80%N_2和80%SF_6/20%N_2的介质恢复强度分别是纯SF_6的54.5%和91.5%;对于不同比例的SF_6/N_2混合气体,相同时间内开断速度9.6m/s与4.8m/s相比,介质恢复强度的增长速率明显加快;开距14mm时,60%SF_6/40%N_2在充气压力0.7MPa下的介质恢复强度是0.9MPa下的77.8%。考虑液化和温室效应问题,当灭弧室压力0.7MPa、开断速度9.6m/s时,SF_6/N_2的最佳混合比为60%:40%。     

双断口结构对特高压SF6断路器气流场影响分析

基于动网格技术,根据边界的运动、变形和重新构建计算区域的网格,对双断口特高压SF6断路器开断过程的气流场进行仿真。采用有限体积方法,对灭弧室内有源、有粘、可压且伴有激波、湍流的复杂流路的气流场进行数值计算。通过550kV单断口灭孤室与1100kV SF6双断口灭弧室总体与喷口、静弧触头、动弧触头周围气流场特性进行定量描述与对比分析,找到不同流路下的气流场的变化,为串联多断口结构对特高压SF6断路器介质恢复特性影响分析与设计提供基础。     

气流流路对高压SF_6断路器介质强度混沌影响

高压SF6断路器的开断性能主要取决于灭弧室内的介质恢复能力。开断过程中,气流在可变流路中呈跨音速流动,将不可避免地产生湍流与激波,气流参数变化存在混沌特征,且灭弧室内部各气流参数在毫秒级时间与毫米级空间内气流运动行为复杂多变。采用有限体积法对550k V单断口高压SF6断路器开断容性小电流情况下的气流场进行数值求解,通过改变喷口长度及型面可调控气流流路,改变气流参数时空行为;采用有限元法得到灭弧室内电场分析;基于流注理论得到不同喷口结构下灭弧室内的介质恢复特性。由于断路器开断过程中介质强度恢复存在混沌,影响断路器的开断性能,通过改变喷口气流流路可以有效调控断路器内气流参数的混沌特性,以增强介质恢复能力,提高开断性能。     

高压断路器辅助开关分断能力研究及结构优化设计

对FK-口型辅助开关灭孤室进行二维数学建模,分析其内部电场强度分布,推导出电流过零后介质击穿的判断条件,对灭弧室结构进行优化,达到降低电场强度,使电场分布趋于均匀的目的,为辅助开关的优化设计提供了有效的解决方法.     

Effect of puffer volume and operating force on dielectric recovery performance in thermal puffer-type gas circuit breaker

In order to investigate the influence of puffer volume V/sub P/ and operating force to dielectric performance of GCB at current interruption, we calculated the prospective dielectric withstand voltage V/sub W/ between arcing contacts. The withstand voltage was calculated by the electric field strength appeared on arcing contacts and the allowable electric field strength E/sub W//sup */ of hot gas due to thermal puffer action. We could clarify that large initial puffer volume V/sub P/ can increase withstand voltage V/sub W/ at current breaking point and also that an optimum point exists in operating force F. For example, it was found that in case of the operating force of 1000 kgf, the puffer volume V/sub P/ of 1.2 liter would be best choice in the interrupting condition of i=50 kA and arcing time of 1.35 cycle.     

252kV自能SF_6断路器开断能力的研究和提高

提高电力系统元件的可靠性是提高电力系统可靠性的重要措施。笔者主要从优化断口间的绝缘结构、改善介质状况和增强热膨胀效应方面来提高断路器的开断能力。所研究的252 kV断路器总体设计方案采用双室+双动的自能式灭弧室结构和触头运动方式,并结合定型产品的设计经验进行了关键结构参数的设计优化:确定热膨胀室和压气室的容积及其配合问题,保证了大电流开断的可行性;利用电场分析软件,对断路器的关键部位的电场强度进行了计算、分析和优化;为了抑制由电弧引起的气体密度的下降,加强热气体的排放效率,进行了导气流通道的改进,改善了介质状况。所研制的断路器通过全部型式试验,并已投入生产,同时为后续产品的研发提供了技术平台。     

触头盒内最大电场强度的计算

建立了舌形触头盒内最大电场强度的计算公式。公式表明触头盒的介电常数愈大,盒内触头最大电场强度愈小,公式计算结果与实测相当接近,可供舌形触头盒绝缘结构设计参考。     

A study of capacitive current switching capability by flashover characteristics between contacts of circuit breakers

This paper describes the capacitive current interruption capability of circuit breakers from the viewpoint of flashover characteristics between the contacts of breakers. The authors obtained flashover characteristics between the contacts having a short gap between them by comparing the data for new contacts and the data for contacts eroded after having been exposed to three interruptions at T60 according to amended regulations JEC 2300 (1998) and IEC 62271‐100 (2001). Comparison of the flashover characteristics and the electric field calculations obtained by measurements using new and eroded contacts have shown that the deterioration of dielectric strength amounts to 10 to 20%. The authors also conducted flashover tests for the contacts and nozzle after a significant number of interruptions. The total number of interruptions can be considered as the maximum possible number of interruptions according to CIGRE research. The deterioration of dielectric characteristics is 10 to 30%. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 28–37, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10281     

The irreversibility of dielectric strength of vacuum interruptersafter short-circuit current interruption

The irreversibility of dielectric strength of commercial vacuum interrupters after a large number of consecutive short-circuit current interruptions is investigated in order to find out how dielectric performance of a vacuum interrupter degrades during its service life. Breakdown voltage data were measured in appropriate experiments in which the types of tested interrupters and arcing conditions were varied. It was found that for interrupters with poor contact material the dielectric strength can deteriorate severely, falling below limits required by standards. It is concluded that the most important for the irreversible decrease in the dielectric strength is the contact material, i.e. its erosion properties. It appears that contacts with axial magnetic field are less susceptible to irreversible changes in dielectric strength after short-circuit current interruption than contacts with transverse magnetic field     

The electric field in porous materials calculated with the grainconsolidation model

We have used the grain consolidation model (GCM) to study the spatial variation of the electric field inside a porous medium such as oil impregnated cellulose. The calculations were primarily performed in order to determine the maximum electric field within the composite, which is important for the overall dielectric strength of the material. In the composite as a whole, the maximum field may be considerably higher than in a homogeneous medium under the same applied external field. The contacts between the solid particles in the composite material are more realistically described in the GCM than in effective-medium models, and a comparison shows that the GCM yields higher maximum fields than effective-medium theory. Two different 3-dimensional geometries have been used in the GCM calculations and the results indicate that the exact geometry is of minor importance. These models are isotropic, while many important insulation materials are highly anisotropic. In order to illustrate the effects of different geometries, we have also performed calculations on a 2-dimensional geometry. In this case, it appears as if the lack of contacts between the solid particles mainly influences the maximum field in the phase which has the highest complex conductivity. If the conductivities of both phases are almost equal, the maximum field is close to the applied field. Increasing the difference in conductivity between the oil and the solid increases the maximum electric field. We have also shown that the GCM can be used to estimate the electric field in the presence of interface effects     

72.5kV真空灭弧室电位和电场分布研究

为分析72.5 kV真空灭弧室的电位分布和电场分布及其影响因素,建立了其轴对称有限元分析模型,计算了其电位分布和电场分布,研究了真空击穿的面积效应,并分析了主屏蔽罩的结构尺寸及多个屏蔽罩对真空灭弧室内部电场分布的影响。结果表明:真空灭弧室动静触头之间、触头和屏蔽罩之间的电位变化比较显著,灭弧室内部电场分布不均匀;随着触头间隙距离、触头半径及倒角部分曲率半径的增大,触头表面有效面积将增大,而灭弧室内部最大场强将有所减小;增大主屏蔽罩的半径和长度,可以使屏蔽罩两端的场强有所减小,在真空灭弧室内安装多个屏蔽罩,可以改善内部电场分布。计算结果可为高电压等级真空灭弧室的优化设计提供参考。