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.

Vacuum Dielectric Recovery Characteristics of a Novel Current Limiting Circuit Breaker Base on Artificial Current Zero

为了保证新型强迫换流型真空直流限流断路器关断短路电流的可靠性，对该型断路器分断过程的真空介质恢复特性进行研究。设计了与断路器关断过程等效的介质恢复试验方案，通过等效试验结果和理论推演公式的拟合，得到了新型强迫换流型限流断路器真空灭弧室触头打开过程的动态介质强度恢复规律。研究结果表明：减小燃弧能量、提高触头运动速度可提高真空灭弧室介质的临界击穿电压；综合考虑燃弧时间与燃弧能量及触头开距的关系，随着燃弧时间的增加，真空灭弧室临界击穿电压先减小后增大。所得介质恢复规律可以作为新型断路器优化设计的参考依据。

New Generation of Outdoor Vacuum Circuit Breakers with Rated Voltage up to 40.5 kV

The article describes design peculiarities of the novel compact vacuum circuit breaker with rated voltage 40.5 kV. The design incorporates several novel technical solutions： polycarbonate support insulation, mono-stable magnetic actuator, labyrinth pulling insulator, core-type flexible contact and new compact vacuum interrupter （VI）. Phases are encapsulated into silicone rubber providing required creepage distance and excellent tracking resistance. These novelties along with extensive modeling of the mechanical and electrical fields followed by design optimization resulted in weight reduction of more than 50% compared with alternatives available in the market. And this is in spite of built in sensors measuring： phase currents, zero-sequence current, phase voltages.

Study of post-arc residual plasma dissipation process of vacuum circuit breakers based on a 2D particle-in-cell model

In order to get an insight into residual plasma radial motion during the post-arc stage,a twodimensional(2D)cylindrical particle-in-cell(PIC)model is developed.Firstly,influences of a virtual boundary condition on the residual plasma motion are studied.For purpose of validating this 2D cylindrical particle-in-cell model,a comparison between one-dimensional particle-in-cell model is also presented in this paper.Then a study about the influences of the rising rate of transient recovery voltage on the residual plasma radial motion is presented on the basis of the 2D PIC model.

Study on Restrike Phenomena for 40.5-kV Vacuum Circuit Breakers

When interrupting short circuit fault by 40.5-kV vacuum circuit breakers, it is significant to eliminate multiple restrike phenomena, which occur frequently and result in high overvoltage and even interruption failure. A synthetic circuit that can supply a DC recovery voltage after current zero was used to study multiple restrike phenomena in switching. Some key factors including breaking current, clearance between open contacts, electrode structure and contact material, which may affect restrike characteristics, were studied. Under various clearances, the statistical probability of restrike was obtained. As a result, the best scope of clearance between open contacts was found. The performance of CuCr50/50 and CuCr75/25 material were compared. Two kinds of electrode structures, namely 1/2 coil structure and cup-shaped axial magnetic structure, were tested. After a high-current interruption, conditioning effoct was realized and the probability of restrike decreased.

The Voltage Distribution Characteristics of a Hybrid Circuit Breaker During High Current Interruption

Hybrid circuit breaker （HCB） technology based on a vacuum interrupter and a SF6 interrupter in series has become a new research direction because of the low-carbon requirements for high voltage switches. The vacuum interrupter has an excellent ability to deal with the steep rising part of the transient recovery voltage （TRV）, while the SF6 interrupter can withstand the peak part of the voltage easily. An HCB can take advantage of the interrupters in the current interruption process. In this study, an HCB model based on the vacuum ion diffusion equations, ion density equation, and modified Cassie-Mayr arc equation is explored. A simulation platform is constructed by using a set of software called the alternative transient program （ATP）. An HCB prototype is also designed, and the short circuit current is interrupted by the HCB under different action sequences of contacts. The voltage distribution of the HCB is analyzed through simulations and tests. The results demonstrate that if the vacuum interrupter withstands the initial TRV and interrupts the post-arc current first, then the recovery speed of the dielectric strength of the SF6 interrupter will be fast. The voltage distribution between two interrupters is determined by their post-arc resistance, which happens after current-zero, and subsequently, it is determined by the capacitive impedance after the post-arc current decays to zero.

Study on TRV of circuit breaker in two substation operational ways and its countermeasure

To verify a vacuum breaker's feasibility,when a transformer substation chooses a vacuum circuit breaker,it takes two different actual operational ways to cut off a transformer.This paper,using the power system computer aided design/electro magnetic transient in DC system(PSCAD/EMTDC)software,simulates the substation system and studies transient recovery voltage(TRV)caused by the two different ways which can cut off a with load transformer or a no-load transformer.Simulation and calculation results show that TRV indexes of the first way are much higher than that of the second one,and their TRV indexes are both in a permissible range.The breaker is proved to be available.Besides,this paper proves that paralleling resistance has a good effect when the indexes exceed the standard.The resistance value depends on specific circumstances.

高速列车过分相VCB延时断开故障测试及原因探究

高速列车车载真空断路器(VCB)性能是列车安全稳定运行的重要保证之一。近年来,国外某型号动车在过分相时出现VCB延时断开故障,导致只能通过降弓方式来预防带电过分相引发的安全隐患。针对以上问题,推测其原因是VCB触头间电弧烧蚀或牵引变压器合闸时刻励磁涌流导致的VCB过载造成。主要针对牵引变压器合闸励磁涌流进行研究,通过现场测试和PSCAD仿真探究励磁涌流的影响因素和实际可达到的最大值。结果表明,列车过分相VCB完成合闸后实测最大电流达到756.67 A,不会对VCB触头造成实质性损伤。牵引变压器励磁涌流大小主要受VCB合闸电压相角和变压器铁芯剩磁影响,且励磁涌流并非导致VCB触头熔焊的主要因素,VCB合断时触头间的电弧烧蚀才是造成VCB触头熔焊的主要原因。

永磁同步电机执行机构新型控制算法研究

电机执行机构应用于断路器中,具有结构简单、动作分散小、可控性强等优点,为实现断路器开关触头对预设参考曲线的跟随提供可能。传统的控制方式参数固定无法根据断路器开关触头运动过程进行参数调整,跟随性差;智能控制算法计算复杂,影响控制系统快速性,且工程上极难实现。提出一种分段式伪微分控制策略,该控制策略避免了被控变量的直接微分,具有快速动态响应和抗干扰能力,同时,根据环境分段式赋予控制系统参数,保证了跟随精度。建立该控制策略模型进行仿真分析,并研制126 kV断路器电机执行机构控制系统以试验验证,仿真及试验结果均表明了该控制策略的有效性。

真空与气体一体化串联机械开关及其直流快速转移应用

为提升中压混合式直流断路器的自然换流性能,该文提出一种真空与气体一体化串联机械开关,分析真空与气体一体化串联用于电流转移性能的工作原理。并基于此设计了双超程联动的真空与气体一体化串联开关实验样机,研究了气体类型、气压、触头结构、触头材料等参数对电弧电压特性的影响规律,确定了W70Cu桥式两触点结构,采用H2和N2体积比为2:3、气压为0.3 MPa的氢氮混合气体,弧压可由20 V提升到120 V,电流转移时间由1 900μs缩短至300μs。同时测试了静态瞬态开断电压(TIV)分布特性,真空间隙承担主要电压(55%),串联整机耐压水平为20 kV。验证了真空与气体一体化串联开关应用于中压混合式直流断路器的可行性和有效性。

动车组合闸过电压故障机理兮析及仿真研究

[目的]动车组出分相时,断路器合闸产生的过电压会加剧高压设备的绝缘老化,研究合闸过电压的产生机理及影响因素对动车组主电路绝缘匹配和设备选型具有理论意义。[方法]结合动车组主电路结构和过分相过程,分析其正常运行方式下操作过电压的形成原因。考虑真空断路器合闸弹跳特性对过电压的特殊影响,建立动车组主电路仿真模型;对比研究动车组主电路合闸过电压特征,得出主回路状态动作时刻、动车组高压电缆参数、接触网参数及设备特性对过电压的影响规律。[结果及结论]极端状态下过电压峰值为工频电压峰值的2.39倍,接近《高速动车组整车试验规范》规定的2.4倍,在极端工况下产生的过电压会对动车组高压设备的绝缘性能产生影响,甚至导致击穿现象。因此,需采取如采用相控合闸技术控制断路器在目标相位闭合、选择单位分布电容较小的高压电缆、改进真空断路器的机械特性等相关措施进行防范,以有效降低动车组合闸过电压。

2/3匝线圈式纵磁触头大开距真空断路器分闸速度设计

合理设计纵磁触头真空断路器的分闸速度特性,可有效避免大电流开断过程中真空电弧阳极斑点的形成或缩短阳极斑点持续时间,显著提升断路器短路电流开断性能。然而,现阶段仍然缺乏线圈式纵磁触头真空断路器全行程分闸速度特性的量化设计方法。该文试验研究了电弧电流、分闸速度对2/3匝线圈式纵磁触头大电流真空电弧阳极放电模式演变的影响规律,获得了不同分闸速度下线圈式纵磁触头阳极放电模式图,据此提出线圈式纵磁触头分闸速度的量化设计方法:初始分闸速度v1应不小于其从强电弧模式演变为扩散态电弧模式的临界触头开距峰值所对应的分闸速度;平均分闸速度v2应不大于大开距活跃阳极放电模式形成的临界触头开距峰值所对应的分闸速度;同时,对比实际开断过程中触头间隙磁感应强度与阳极放电模式演变的临界纵向磁感应强度,可校验上述分闸速度特性设计的合理性,并能预测该纵磁触头以任一分闸速度开断任一短路电流时的阳极放电模式演变特性。应用上述方法,该文确定了126 kV单断口真空断路器的分闸速度特性设计值为v1=3.5 m/s、v2=3.0 m/s,并通过型式试验验证了断路器在上述分闸速度特性下的短路电流开断性能。

基于图像信息熵与多元变分模态分解的电缆局放信号去噪方法

局部放电(PD)检测是评估交联聚乙烯(XLPE)电缆绝缘状态的主要手段。针对电缆终端与中间接头局部放电现场检测时存在白噪声、周期性窄带干扰,以及去噪过程中自适应性较弱的问题,该文提出了一种基于图像信息熵与新型自适应多元变分模态分解的去噪方法。首先,对信号进行多元变分模态分解,重组信号并转换成灰度图像,进而计算图像一维信息熵。在考虑算法执行效率的同时,将Pearson相关系数与图像信息熵优化算法的模态参数相结合。其次,通过计算各本征模态分量的峭度来判定其主导分量的性质特征,利用峭度对噪声敏感的特性区分PD特征信息与噪声干扰分量,进而对噪声干扰分量进行3σ准则滤波。最后,通过新型改进小波阈值算法得到去噪信号。利用该方法对PD信号进行去噪,并与基于Spearman的变分模态分解(S-VMD)法、自适应集合经验模态分解(NAEEMD)法、短时傅里叶变换-奇异值分解(STFTSVD)法进行对比分析。结果表明,该方法对现场PD信号具有良好的抑噪性能,且耗时少、执行效率高、工程应用价值高。

72.5 kV快速真空断路器技术研究及开发

短路故障的快速切除对提高电网输电线路的输电能力和提高电力系统暂态稳定性至关重要。快速真空断路器是实现短路故障快速切除的理想选择。文中目标是设计一款新型单断口72.5 kV快速真空断路器并对其短路电流开断性能进行验证。采用具有多重悬浮屏蔽罩与轻量化技术的72.5 kV真空灭弧室用作灭弧器件,电磁斥力机构用作操动机构,一款特殊设计的油阻尼器用作速度调节器。为满足短路电流开断要求,依据阳极放电模式将分闸速度特性定量化调控为:前15 mm行程内平均分闸速度v1为5 m/s,满开距30 mm内平均分闸速度v2为1.59 m/s。经测试,开发的72.5 kV快速真空断路器的分合时间分别为(1.2±0.04)ms和(18±0.20)ms;进行了T100s(b)方式下的40 kA(rms)和80 kA(rms)的短路开断性能验证。开断结果显示,研制的72.5 kV单断口快速真空断路器满足了国标GB 1984—2014全燃弧时间窗口开断要求。

基于两间隙异步联动的一体化高压真空灭弧室电场设计

输电等级真空灭弧室是迫切需要解决的行业级难题,为克服单断口真空灭弧室绝缘瓶颈和多断口串联结构复杂等问题,该文提出了一种基于两间隙异步联动的一体化高压真空灭弧室结构,该结构采用辅间隙与主间隙串联异步联动,辅间隙协助主间隙绝缘和灭弧,有望实现252kV及以上电压等级真空灭弧室的工程应用。建立了两间隙异步联动的一体化高压真空灭弧室电场仿真模型,分析了进出线方向、主辅间隙、屏蔽罩等对电场强度和电压分布关系的影响规律,并研究了屏蔽罩结构和环形陶瓷分压电容器等分压措施对电场提升的效果。研究表明:静端盖为出线端、动端盖为进线端时,主间隙开距为60 mm、辅助间隙开距为30 mm可以满足分压关系按照开距大小分布,最大电场强度相比于长间隙开距60 mm时降低27.3%。外部并联环形陶瓷分压电容器可以满足双向分断的要求,进线端在静端盖时外部并联环形陶瓷分压电容器灭弧室相较于未并联电容的灭弧室最大电场强度降低30%左右,初步说明了基于两间隙异步联动的一体化高压真空灭弧室结构的可行性和有效性,研究可为高电压等级真空灭弧室研制提供新思路和新方法。

混合式直流断路器内部关键参数对电弧电流转移特性的影响研究

真空电弧电流转移是自然换流型混合式直流断路器开断过程中的一个重要组成部分。文中通过建立真空电弧电流转移的理论分析模型,得出影响真空电弧电流转移的主要因素为真空电弧电压、内部杂散电阻电感参数和电力电子器件的串并联结构。实验方面,通过改变电力电子开关中电力电子器件的串联或并联个数研究了电力电子器件的串并联结构对真空电弧电流转移特性的影响,通过改变电力电子开关中杂散电感或电阻的数值和所处位置研究了内部杂散电阻电感参数对真空电弧电流转移特性的影响。最后,探究了促进电弧电流转移的方法。本研究将为混合式直流断路器的结构设计和参数优化提供理论依据。

融合连续过渡模型与Helmer模型的真空断路器开断模型研究

真空断路器广泛应用于中压等级电网中,在频繁操作场景下易出现过电压问题,而真空断路器的弧后暂态过程直接决定了其分断特性和过电压特征。为解决现有真空断路器模型难以同时对其弧后过程和高频特性仿真的问题,该文搭建了融合连续过渡模型和Helmer模型的真空断路器开断模型,并通过试验和计算确定其仿真参数。以切除35kV系统用并联电抗器为例,研究该真空断路器融合模型与连续过渡模型和Helmer模型计算结果的差异。结果表明,融合模型能够同时考虑弧后介质恢复过程中重击穿和冷间隙重击穿现象;其弧后参数计算与连续过渡模型基本一致,高频开断特性和Helmer模型较为接近。通过分析高频开断过程中的鞘层生长和重击穿情况,可以得到引起真空断路器高频重击穿的主要原因。该文仿真结果验证了所提出的真空断路器开断模型的准确性,可为真空断路器高频分断条件下的弧后鞘层发展分析和重击穿原因判断提供参考。

投切并联电容器时真空断路器连续重燃事故的机理分析

并联电容器作为无功补偿装置,要随电力系统的无功负载变化进行频繁投切。由于用于投切的真空断路器重燃率较高,切除并联电容器时容易发生重击穿故障。文中针对西北某330 kV变电站低压侧采用真空断路器切除35 kV电容器时,两相电容器分别发生鼓包喷油的严重事故展开研究。通过现场检查、过电压理论分析及电磁暂态仿真分析等手段,分析获得了故障产生的原因。仿真波形与事故录波波形完好吻合,验证了所提出事故发生过程的准确性,并证明了真空断路器连续重燃是电容器故障的根本原因。最后,提出改善措施以降低真空断路器发生重击穿的概率,以避免切除并联电容器时重击穿事故的发生。

真空断路器铜铬金属蒸气等离子体非局部热力学平衡态物性参数分析

真空断路器在大电流故障开断过程中,以真空为介质条件的灭弧系统内所产生的金属蒸气电弧等离子体组氛与电极材料特性密切相关。为了研究开断过程中金属蒸气等离子体物性参数的变化,以真空断路器CuCr25~CuCr75触头电极材料为研究对象,建立非局部热力学平衡模型,研究铜铬合金不同配比下金属蒸气等离子体粒子组氛分布。采用统计热力学方法求得等离子体热力学参数,分析不同合金配比下比焓和比定压热容分布;利用Chapman-Enskog法计算等离子体输运参数,探究铜铬合金材料配比对电导率的影响。