A Fault Current Limiting Hybrid DC Circuit Breaker

Due to the low impedance characteristic of the high voltage direct current(HVDC)grid,the fault current rises extremely fast after a DC-side fault occurs,and this phenomenon seriously endangers the safety of the HVDC grid.In order to suppress the rising speed of the fault current and reduce the current interruption requirements of the main breaker(MB),a fault current limiting hybrid DC circuit breaker(FCL-HCB)has been proposed in this paper,and it has the capability of bidirectional fault current limiting and fault current interruption.After the occurrence of the overcurrent in the HVDC grid,the current limiting circuit(CLC)of FCL-HCB is put into operation immediately,and whether the protected line is cut off or resumed to normal operation is decided according to the fault detection result.Compared with the traditional hybrid DC circuit breaker(HCB),the required number of semiconductor switches and the peak value of fault current after fault occurs are greatly reduced by adopting the proposed device.Extensive simulations also verify the effectiveness of the proposed FCL-HCB.

Phase Evolution Study and Optimization of the Heat Treatment Process for High Current Capacity Bi-2223 Tapes

Powder in tube process（PIT） was adopted for the fabrication of single filament Bi-2223 tapes, and a heat treatment process including the first heat treatment（HT1）, intermediate rolling（IR）, and second heat treatment（HT2） was performed. The phase evolution mechanism and microstructure changes during these heat treatment processes were systematically discussed. The influences of HT1 parameters on the phase evolution process of Bi-2223 tapes were discussed. With the optimized HT1 process, a proper Bi-2223 content of about 90% was achieved. HT2 process was also optimized by adding a post annealing process. An obvious increase of current capacity was obtained due to the enhancement of intergrain connections. Single filament Bi-2223 tapes with the critical current of Ic-90 A were fabricated with the optimized sintering process.

High Temperature Superconductivity in the Past Twenty Years Part 2——Towards to Practical Applications

After discovering high temperature superconducting materials 20 years ago, the preparation of applicable HTS materials has been pursued along with HTS mechanism and characteristic study. At present, the focus on the applied HTS technology has been moving to the industrial preparations from the laboratory research stage, and the technology has been well verified for practical applications from small to large scales. The fabrication techniques of engineering HTS materials are being industrialized; and various HTS devices are also on the way towards practical applications. This paper provides a comprehensive summary on the applied high temperature superconductivity with regard to various applicable HTS materials, their preparation techniques and charac- terization, and applications in a wide range.

Summary of the First Generation High Temperature Superconducting Wire: Processing, Characterization and Applications

Silver-clad （Bi,Pb）2Sr2Ca2Cu3O10＋x long wires produced by powder-in-tube techniques, which have been recognized as the first generation of the High Temperature Superconducting （HTS） wires, are expected to apply widely especially in strong current applications. In this work, the processing, characterization and application of the silver-clad （Bi,Pb）2Sr2Ca2Cu3Ol0＋x HTS wires are summarized. The HTS wires are fabricated using the combination of powder-in-tube technique, and the resulting wires are fully characterized by the means of chemical analyses, microstructural observation, electrical and magnetic measurements. The relationship among fabrication parameters, chemical and microstructural characteristics, and electrical and magnetic properties are analyzed. Applications of the HTS wires have also been introduced according to their strong current behaviors with various prototype devices made.

Interruption Characteristics of High-speed Switches in 500 kV Fault Current Limiter with High Coupled Split Reactance

A 500 kV high-voltage AC fault current limiter(FCL)based on a high coupled split reactor(HCSR)is pro-posed by the National key R&D project team.Low impedance under normal conditions and high impedance under short-circuit conditions are accomplished by the cooperation of HCSR and high-speed switches.High-speed switches play an important role in current limiting processes,thus interruption characteristics of the high-speed switch in the 500 kV FCL are studied in this paper.The simulation model of the FCL and the external equivalent power grid are established.The short-circuit current and recovery voltage characteristics of the high-speed switch in FCL are simulated.The results show that maximum DC component of the short-circuit current of the high-speed switch reaches 91%,the maximum peak value is 118 kA,and the longest arcing time is 14.8 ms.There is a discontinuity in the curve of the short-circuit current peak and arcing time as a function of the short-circuit occurrence time;the peak recovery voltage of a single break of the high-speed switch has a maximum value of 87.5 kV under a three-phase ungrounded short-circuit condition,and the rate of rise of recovery voltage is o.22 kV/s.The recovery voltage peak shows a period change with the short-circuit occurrence time,and the period is 10 ms.The effects of the shunt capacitor value and short-circuit ground resistance on the recovery voltage of high-speed switching are also studied.The research can be used for reference by R&D personnel and testersof500kVFCLs.Index Terms-Fault current limiter(FCL),high coupled split reactor(HCSR),high-speed switch,interruption characteristics,short circuit current.

基于电容限流的混合式高压断路器拓扑研究

随着电能传输容量越来越大、传输距离越来越远,高压、超高压直流输电网的“弱阻尼,低惯量”愈发严重。高压直流断路器已成为高压、超高压直流电网的关键器件之一。本研究提出的一种利用电解电容进行限流的混合式高压直流断路器,具备良好的故障电流开断能力,并能够抑制故障电流的快速上升,减少全控开关IGBT数量。首先,介绍基于电解电容进行限流的断路器的电路结构;然后,阐述其阻断故障电流的原理;最后,在仿真平台PSCAD上搭建了仿真模型。仿真结果表明:该断路器能够快速阻断故障电流,抑制电弧。

高压交流断路器标准的主要差异分析

本文主要对GB/T 1984—2014与IEC 62271-100:2021的差异进行分析,主要针对文本差异和基本技术参量差异两个方面,其中文本差异主要分析了适用范围和规范性引用文件、使用条件以及术语和定义;基本技术参量差异主要分析了额定绝缘水平、温升限值、TRV参数以及试验参量的容差。通过以上几个方面的分析,加深对标准理解和规范检测认证。

一种新型限流型高压直流断路器拓扑

随着柔性直流输电技术的不断成熟,直流输电变得越发普及,而高压直流断路器作为直流输电系统的关键部分,其重要性不言而喻。针对现有高压直流断路器存在故障时短路电流大、分断速度慢、避雷器吸收能量过高等问题,提出了一种具有限流能力的新型高压直流断路器拓扑,该拓扑在传统直流断路器换流支路基础上增加了H型桥限流部分,利用平波电抗器与限流部分共同限流,可以显著降低故障时电流的上升速率与峰值。文中详细说明了新型拓扑的基本工作原理,对故障分断过程进行理论分析并给出相关参数的影响关系及选取依据,通过搭建基于Pscad/Emtdc仿真软件的新型限流型断路器模型,与已有限流型断路器方案相比,避雷器能量吸收降低了62.8%,故障分断时间减少了0.8 ms,并具有良好的可靠性与经济性,仿真结果验证了所提新型限流型直流断路器拓扑可适用于当前柔性直流电网。

一种基于自适应电压限值的换相失败抑制策略

为有效抑制高压直流输电系统在不同故障程度下的换相失败,提出了一种基于自适应电压限值的改进低压限流控制器(voltage dependent current order limiter,VDCOL)设计方案。首先,详细分析了包含传统VDCOL的直流输电系统在换相失败及恢复期间的运行特性,并提出VDCOL曲线在不同时间段下应具备的动态性能。然后,引入直流电流这一反映故障特性的时变电气量优化传统VDCOL的直流电压上下限值,从而在不同时间段自适应改变电流指令启动电压阈值与电压-电流指令变化趋势,以满足输电系统换相失败及恢复期间的有功与无功需求。同时考虑到VDCOL电压上下限值的过度变化会恶化系统运行特性,对其范围的设置进行了解析和合理选取。最后,在PSCAD/EMTDC中对所提方法进行仿真测试。结果表明,所提出的改进控制策略能在一定程度上抑制直流输电系统的连续换相失败,同时有效地改善换相失败各阶段直流输电系统的运行特性。

含限流电抗器的环形直流微电网暂态对地高频电压保护方法

直流线路保护是直流微电网技术发展的关键,限流电抗器为直流故障保护算法的设计提供了便利。针对含限流电抗器的环形直流微电网,利用限流电抗器的故障暂态高频电压特性,提出一种基于限流电抗器两端对地高频电压的保护方法。该方法利用故障后线路两侧限流电抗器两端对地高频电压的差异性识别区内外故障,对于线路背侧阻抗呈容性将导致保护无法正确动作的情况,通过选择合适的频率能够很好地解决。仿真结果表明,该保护方法可快速、准确地判断故障线路和故障极,灵敏度与可靠性高,阈值易设定且无须相邻线路保护配合,对双端数据同步要求较低。该方法在不同的故障场景和运行方式下均能可靠进行故障识别和故障选极,并且耐受过渡电阻能力较强。

低温环境下高压断路器故障模拟

高压断路器是电力系统中的重要设备,发生故障会对电力系统的安全稳定运行造成影响。低温环境会影响断路器的开断性能,为研究低温下故障对断路器的影响,建立了液压弹簧机构和分合闸线圈模型,仿真分析了低温、分合闸线圈故障对分合闸时间与线圈电流的影响。搭建了低温环境下的故障模拟实验平台,在不同低温等级下进行了大量故障模拟实验。将断路器分合闸时间、分合闸线圈电流和振动信号边际谱能量作为特征量,分析其变化规律。研究发现:低温环境影响断路器的开断性能;断路器的分合闸时间随着温度的降低而增大;温度对线圈电流影响很小;–10℃以下振动信号边际谱能量变化较小。研究结果为低温环境下断路器的故障诊断提供了参考。

500 kV限流器高温超导磁体的制作与测试

超导限流器是对超高压输电线路短路故障电流实现快速、有效限制的一种新型电力装置。近年来随着国民经济的发展,用电负荷增长和供电可靠性需求增加,电网短路电流水平已经逼近甚至超过传统开关设备的开断能力,成为超高压电网发展和安全、稳定运行的重要制约因素之一。然而,电网结构调整等传统限流措施降低了电网的安全性和灵活性,亟需研制适用于超高压电网的限流装置。超导限流器集短路故障检测、触发和限流功能于一身,是电力系统最理想的限流装置。依托高电压等级限流器用超导磁体系统的研制项目,完成500 kV限流器用高温超导磁体系统制作与测试工作。该超导磁体的室温孔径为1660 mm,总高度为1960 mm,液氮量为2000 L,中心最大磁场为0.45 T,额定励磁安匝数为468000安匝,由3组线圈共计88个双饼组成,运行电流分别为220 A(YBCO线圈)/1000 A(Bi2223线圈)/220 A(YBCO线圈),杜瓦注入液氮后抽空减压至72 K稳定运行。经过绕制、接线、组装、焊接、检测等工序,完成磁体系统集成,降温后进行整体测试,一次性励磁成功,没有失超。整个系统绝缘等级大于10 kV、真空漏率优于10^(-6)(Pa·L)/s、液氮蒸发量小于70 L/d,指标均达到设计目标。

A Similarity Comparison Based Pilot Protection Scheme for VSC-HVDC Grids Considering Fault Current Limiting Strategy

In the voltage source converter based high-voltage direct current(VSC-HVDC)grids,fast and reliable protections are the key technologies.The traditional protection schemes are easily affected by fault resistance,line distributed capacitance,etc.Meanwhile,the influence of fault current limiting strategy(FCLS)has not been fully considered.In this paper,the fault characteristics under FCLS and the feasibility of traditional travelling wave protections are analyzed.To improve the reliability and sensibility,a similarity comparison based pilot protection scheme is proposed,which focuses on the relationship between the fault characteristics and the state of the protected transmission line,with the establishment of a precise frequencydependent transmission line model.The criteria based on the similarity comparison calculated by cross-wavelet can identify the fault effectively.Meanwhile,the protection scheme can also endure the influence of error synchronization.Finally,the protection performance is verified in the PSCAD/EMTDC under different fault conditions.

高温超导限流器对风电场故障穿越能力的影响研究

当电网发生故障时,风电场容易自动解列而导致故障更加严重,因此风电机组应具备一定的故障穿越能力。本文提出将高温超导故障限流器应用于风电场,以提高风电场低电压穿越的能力。通过建立高温超导限流器模型以及含高温超导限流器的风电机组并网模型,然后仿真在不同故障类型和不同拓扑下高温超导限流器对风电场故障穿越能力的影响。研究表明,使用高温超导限流器能够有效提高风电机组在系统发生单相、多相故障下的穿越能力,同时,提高单回线与双回线送出电能的风电场模型故障穿越能力。

Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

A common method to examine the current-limiting performance of saturated iron-core fault current limiter(SI-FCL) in high-voltage direct-current transmission based on voltage source converter(VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the currentlimiting effect of the SI-FCL.In this paper,the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined.Based on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.

A review of superconducting fault current limiters compared with other proven technologies

Several substations in operation were commissioned decades ago.These substations are overstressed,then their protection equipment cannot provide an effective safety condition to the system.In the worst cases,short‐circuits can cause permanent damage to the system if the overcurrent is higher than the capacity of the installed equipment.There are some possible solutions for those cases:replace all the equipment in the overstressed substation,build a new one in parallel or install a fault current limiter(FCL)device.From an economic point of view,introducing FCLs in the power system is the best way to solve the described problem.The commercial solutions available are the pyrotechnic FCL,air coil reactor,neutral earthing resistor,and high impedance transformer.However,these devices are limited and present several drawbacks.Since the’70s,there has been a search for reliable FCL devices that do not interfere in the regular operation of substations and could limit the fault currents to the protection system rated level.There were so many FCL technologies proposed in the last decades.These proposed new devices may use superconducting technologies,power electronics,or both.This paper reviews proven FCL technologies,focusing on full‐scale devices demonstrated in field and lab tests.The goal is to introduce the main FCL technologies in development and discuss didactically their operation principle,the built prototypes,the commercial units,whether they exist,and the main drawbacks for each technology presented.A final analysis of the level of maturity for each FCL technology is discussed using the TRL(Technology readiness level)scale in order to find technologies with more potential for mass production.The three technologies closer to the full commercial application are:the Resistive Superconducting FCL,the Saturated Iron Core FCL,and the Series Reactor FCL.

高温超导体临界电流密度非均匀分布研究进展

高温超导体因其优越性能和广泛应用前景受到了研究人员和业界人士的高度重视。在实际应用领域中,交流损耗关系着超导材料和系统的安全性、稳定性和经济性,所以准确计算并寻找降低交流损耗的方法对其产品商业化有着举足轻重的作用。近年来,众多研究人员基于不同的技术和方法对临界电流密度非均匀分布形式和对交流损耗的影响进行了研究。本文综述了高温超导体临界电流密度非均匀分布的理论模型和交流损耗数值计算方法,讨论了不同分布形式对交流损耗的影响。同时,本文还提供了利用磁场、交流损耗等宏观实验数据反演临界电流密度非均匀分布形式的方法。这些方法能为实际工况应用中高温超导体的设计和生产提供理论支撑。

40-meter-long REBCO tapes with critical current over 4,000 A/12 mm at 4.2 K and 13 T by advanced MOCVD

REBa_(2)Cu_(3)O_(7−δ)(REBCO,RE=rare earth)tapes doped with 5%and 15%Zr have been scaled up to lengths more than 40 m in a pilot‐scale advanced metal organic chemical vapor deposition(A‐MOCVD)tool.The precursor compositions used for the long tapes were guided by a study of the influence of(Ba+dopant)/Cu content on the critical current density(Jc)of 5 and 15 mol.%Hf‐and Zr‐added tapes at 4.2 K and 13 T.The 40‐mlong tapes exhibited a critical current(Ic)over 4,000 A/12 mm at 4.2 K and 13 T as well as over 1,400 A/12 mm at 20 K and 20 T.The critical current densities of a 40‐m‐long tape doped with 5%Zr at 4.2 K measured at the National High Magnetic Field Laboratory(NHMFL)were>10 MAcm^(−2)and>5 MAcm^(−2)at 14 T and 30 T,respectively,which are over three times those of commercial REBCO tapes.The infield Jc of 5%Zradded 40‐m‐long tapes was similar to those of previously‐reported high‐performance short samples made with 15%Zr or Hf.These results demonstrate the excellent potential of A‐MOCVD for manufacturing high Ic REBCO tapes for use in ultrahigh‐field magnet applications.

故障限流器电流转移过程研究

对于电流转移型故障限流器,电流转移的原理和各部件之间的相互作用决定了限流器的性能。本文以一种基于高耦合分裂电抗器的交流故障限流器为研究对象,建立了能够反映HCSR复杂回路对电流转移过程影响的宽频模型,联合电弧模型仿真分析了HCSR引入后对限流器支路电流转移过程的影响。结果表明,开关进入真空电弧不稳定阶段后,限流器存在电流从开关支路向HCSR限流电感支路转移的现象,这一正反馈过程导致限流器开关更容易过零熄弧、实现电流转移。