直流SMC铁心高温超导故障限流器的研究

分析了直流电力系统保护的发展现状,设计了一种铁心型高温超导故障限流器。为了尽量延长限流的时间,限流器的铁心采用软磁复合材料(SMC)。限流器在系统正常工作时对电力系统影响很小,当短路故障发生时,它会很快表现为大阻抗以限制短路电流。基于磁场有限元与电路耦合的计算方法,首先对限流线圈在短路过程中的非线性电感进行精确计算,然后结合计算结果,在电路仿真程序中计算短路电流。通过对比SMC与硅钢铁心材料限流器的限流情况,可以看出SMC铁心限流器对于直流电力系统短路故障的限流效果更好。在短路故障发生后8 ms时,该限流器能将短路电流限制到最大值的12%。     

Proposal of flux‐lock‐type fault current limiter with high‐TC superconducting element

This paper proposes a new type of fault current limiter (FCL), which consists of a high‐T_C superconducting (HTS) element and two coils wound on the same core without any leakage magnetic flux. In this FCL, either the limiting impedance or the initial limiting current level can be controlled by adjusting the inductances and the winding direction of the coils. Therefore, this FCL could relax the material restrictions on high‐T_C superconducting FCL. A current‐limiting experiment by a model FCL was carried out, and the limiting performance was observed. The initial limiting current level of the model FCL was 1.7 times higher than the critical current of the HTS element, and the fault current is suppressed to 52% immediately after the short‐circuit in the test. Considering voltage–current characteristics of a high‐T_C superconductor in a computer simulation, the calculated results almost agreed with the experimental results. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 31–38, 1999     

Design guidelines of a flux‐lock superconducting fault current limiter with ac magnetic field coil for a 6.6‐kV distribution system

We have proposed a new type of fault current limiter, which consists of a flux‐lock reactor with high‐Tc superconducting (HTS) elements and an ac magnetic field coil (Flux‐Lock‐Type Fault Current Limiter: FLT‐FCL). The FLT‐FCL can increase both the current capacity and the limiting impedance by means of a transformer action and an ac magnetic field application mechanism. This paper reports the conceptual design of an FLT‐FCL for application to a 6.6‐kV/200‐A distribution system. Theoretical expressions for the current limiting behavior are derived and the new concept of “quench power” is proposed in order to estimate the required number of HTS elements for two types of FLT‐FCL and for a basic FCL type consisting only of HTS elements. Design guidelines for the FLT‐FCL are derived from the calculation results. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 17–25, 2001     

Fundamental performance of superconducting fault current limiter with two air core coils

In this paper, we theoretically compared the fundamental characteristics of fault current limiter (FCL) with high‐Tc superconductor (HTS) and two coaxial air‐core coils based on steady‐state analysis. Two types of FCL are possible. One is parallel type and the other is transformer type. The parallel type can be divided into two types according to the combination of the winding direction of coils. That is, there are two cases that the coils are wound so that the magnetic fluxes induced by coils reduce and increase each other. In this paper, we called them parallel type 1 and 2, respectively. There is no significant difference in the HTS volume required to satisfy both the specified limiting impedance Z_FCL and initial current I_ini in limiting operation among those three FCLs although the HTS in each type of FCL has different length and cross‐sectional area. In the cases of those FCLs, we can improve the current limiting performance by arranging the HTS in the coils and applying the magnetic flux to the HTS in the limiting operation. The magnitudes of the magnetic flux density are almost the same. From the viewpoint of the FCL impedance in normal operation, parallel type 1 has the most desirable structure. On the other hand, transformer type is the best to eliminate the magnetic flux applied to the HTS in the normal operation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 29–36, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20477     

新型磁控开关型故障限流器拓扑及试验研究

基于饱和铁心型高温超导故障限流器的拓扑,提出了一种适用于中高压电网的磁控开关型故障限流器拓扑结构,在偏置回路中串联了一个限流电感,通过故障前后交流电流的变化自动实现限流电感的退出和接入,从而实现对短路电流的限制,并研制了一台220 V/50 A试验样机。对限流器样机的试验结果表明,磁控开关型故障限流器在正常工作时电压损耗很小,对线路几乎没有影响;故障发生后,限流电感立即自动插入故障回路进行限流,基本不产生谐波,运行控制灵活且简单可靠,对短路电流具有快速、有效的限制作用。     

高温超导变压器关键技术

由于超导材料的无阻载流特性,其在超导电缆、超导限流器、超导变压器、超导储能、超导电机等超导电力装置中的应用引起人们极大兴趣。其中超导变压器具有体积小、重量轻、损耗低、无火灾隐患、无环境污染和低漏抗等特点。简要介绍了高温超导变压器基本结构,重点介绍了变压器研发过程中的关键技术问题,包括液氮和气氮低温绝缘特性、超导绕组损耗分析、电流引线设计、非金属低温容器设计等,为高温超导变压器的研发提供有用的参考。     

超导变压器几种不同绕组形式的环流分析

由于超导材料的零电阻特性,绕组各支路或并绕导线间漏电抗小小的不平衡将会引起很大的环流.环流的存在使得磁场分布更不均匀,进而影响交流损耗和临界电流.本文采用磁场计算与电路分析相结合的方法,即在用有限元法分析磁场并计算反映支路间电磁耦合的电感矩阵的基础上列写电路方程,计算了低压绕组取圆筒式、螺旋式和饼式等三种形式8种情形的环流,并分析了支路电阻对环流的影响.结果表明,仅从减小环流看,圆筒式绕组较螺旋式和饼式绕组更适合具有多根导线并绕的情况;而从减小环流和减少导线焊点考虑,双螺旋式绕组具有优势.同时还证明就环流来说,不能将二次侧圆筒式绕组各层两端短接后用铜线过渡到相邻层来代替绕组轴向并绕导线在层间的换位.     

Design study of a high‐temperature superconducting transformer

Many research and development projects on high‐temperature superconducting apparatus such as a transformer, fault current limiter, and cable are being actively pursued in the power field as a result of performance improvement of Bi silver sheath high‐temperature superconducting (HTS) wire. HTS transformers are considered to be among the most promising applications in view of efficiency improvement, the interface with cryogenic cable and normal temperature devices, incombustibility, overload capability, the function as a reactor, and the possibility of use as a fault current limiter. The necessary technical development items of an HTS transformer in order to achieve performance superior to conventional devices are examined. For this purpose, three‐phase 66‐kV 100‐MVA transformers were designed for the comparison of an HTS transformer and a conventional one with oil cooling. The desirable development items are an HTS wire current density of about 40 A/mm², an allowable winding strain of about 0.5%, a percent impedance of 7.5%, an air gap flux density of about 0.3 T, and AC losses of about 0.3 W/km‐A. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 25–31, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10087     

基于“场-路”耦合有限元分析法的变压器短路电抗仿真的研究

短路电抗法是检测电力变压器绕组变形的有效方法之一,开展变压器短路电抗的仿真计算研究,对于获取各种绕组变形故障时的特征信息具有重要意义。基于实验室中一台模型变压器的结构参数,分别建立了绕组正常及存在匝间短路故障时的有限元仿真模型,利用"磁-路"耦合的方法对变压器的漏磁场和漏感参数进行了计算,分析了绕组变形位置与变压器漏磁场之间的关系,并与在模型变压器上的实验结果进行了对比,结果表明:绕组内部发生匝间短路故障时,在径向中部的匝间短路对漏磁场的影响较大,而在轴向中层绕组的匝间短路对漏磁场的影响较小。研究成果对于指导短路电抗法的现场应用和绕组故障的检测提供了一定的理论依据。     

高压及超高压故障电流限制技术分析

220kV和500kV高压及超高压故障电流限制技术被认为是保障大电网安全稳定运行、提高供电可靠性和灵活性的有效途径。本文结合国内外高压及超高压领域的几个限流器工程示范项目,对比分析串联电抗限流技术、串联谐振限流技术、分裂电抗开断技术、超导限流技术以及其他混合限流技术的原理、设计和制造关键技术、可靠性和造价,并对各种限流技术的优缺点进行了评述。     

Recovery time to superconducting state after quench in superconducting fault‐current limiter

Since fault current tends to increase with electrical power demand, current‐limiting technology for overcurrents has been investigated. As a promising candidate, the superconducting fault‐current limiter (SC‐FCL) is expected to be introduced into power systems. One of the most important features of the SC‐FCL is recovery to a normal operating mode, that is, superconducting state rapidly after current interruption. In this paper, the recovery time of an SC‐FCL introduced into a distribution power system is discussed. To obtain the fundamental data, the recovery time of short Nb‐Ti superconducting cables was measured. We developed a method of calculation of the recovery time and it was confirmed that the calculated results agree with the measured ones. We studied the recovery characteristics of an SC‐FCL in a 6.6‐kV distribution system for the short‐circuit fault near the substation. We considered 3 and 17 cycles as the period from fault occurrence until current interruption. As a result, the superconducting cable length required to recover within the high‐speed reclosing time of 0.3 s are more that 270 and 480 m for 3 and 17 cycles, respectively. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 34–44, 2000     

基于可控串补的故障限流器

研究了一种基于可控串补结构的故障限流器,可对电网进行功率控制并在故障时降低短路电流水平。该故障限流器主要由并联电容、并联电感、反并联晶闸管和与开关并联的串联电感构成。开关用于装置在串补和限流模式间进行切换,装置正常工作时运行于串补模式,故障时迅速切换到限流模式运行,有效限制短路电流。该装置在原有串补装置上改动较少,可为现有设备增加故障限流功能做参考。通过Matlab/Simulink软件对系统进行仿真研究,结果表明此装置能够控制功率并限制短路电流,是电力系统中可靠的保护和控制装置。     

用三维有限元法计算分裂式变压器短路阻抗

为准确计算出分裂变压器高、低压绕组间的短路阻抗,首先采用ANSYS的三维静态磁标势法数值计算得出高压多并联支路与单个低压绕组间的多绕组电感矩阵,并依据电路理论将其简化为等效双绕组电感矩阵,进而得到短路阻抗百分比,并推导了高压各并联支路电流分配,最后给出一个概念设计的分裂式高温超导变压器算例。计算结果表明,低压各分裂绕组分别单独运行时,高压绕组的各并联支路电流分配不均,主要集中在与运行的低压分裂绕组紧耦合的高压支路中,故高压绕组与低压各分裂绕组间的短路阻抗主要由紧耦合的高压支路与低压分裂绕组间的漏磁路决定。     

新型磁控开关型故障限流器参数设计及模型机研究

基于饱和铁心型高温超导故障限流器拓扑,提出了一种适用于中高压电网的磁控开关型故障限流器结构。通过工作原理分析,论证了此拓扑结构的可行性,建立了限流器的数学模型和简化电路模型,推导出这种限流器系统的设计公式,并在此基础上研制了一台220V/50A限流器模型机。试验结果表明,该故障限流器具有快速、有效的故障电流限制作用,且具有结构简单可靠,运行控制灵活的特点。     

串联谐振型FCL对高压断路器开断短路故障的影响

基于串联谐振型故障限流器的等效分析模型,分别针对短路出线故障和近区故障,详细研究了限流电感及其并联杂散电容对短路电流、断路器瞬态恢复电压第一个峰值以及瞬态恢复电压上升率的影响,并综合以上指标得到了断路器苛刻度的变化规律。研究表明,选取合适的限流电感、采取合理的措施改变限流电感并联杂散电容能够有效地降低断路器的苛刻度,有利于断路器对短路故障的开断。     

电力系统高温超导故障限流器的研究

在阐述传统电力系统故障限流器的基础上，综述了高温超导体的基本特性、高温超导 限流的结构，并着重讨论了饱和电抗器型高温超导限流器的设计原理和限流效果。     

Required limiting impedance and capacity of fault current limiter installed in customer system with synchronous generator

We investigated the required limiting impedance and capacity of a fault current limiter (FCL) installed at an incoming feeder of a customer system with a synchronous generator in a utility distribution system. It was assumed that two types of FCL were installed, i.e. a resistive type (R‐type) FCL and an inductive type (L‐type) FCL. A fault current out of the customer system and a voltage in the customer system were calculated following a three‐phase, short‐circuit fault occurrence. It was found that the required type of FCL and the required limiting impedance depended on the rated capacity of the generator in order to obtain the suppression of the fault current under 0.1 kA_S and to maintain of customer voltage between 85 and 100% of the nominal voltage (6.6 kV). The capacity of FCL consisting of the smallest limiting impedance is discussed. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Transient stability of fully superconducting damperless generator at system fault and study of methods to suppress fault currents

A fully superconducting generator possesses both superconducting armature windings and superconducting field windings. Thus it has great potential merits to increase efficiency and decrease size and weight compared with a partially superconducting generator that has normal armature windings and superconducting field windings. To obtain these merits, the warm and cold dampers should be omitted. However, a fully superconducting and damperless generator (FSDG) has the following problems when it is operated while connected to a power line system: (1) the dynamic stability of the generator operation is deteriorated because the FSDG has no damping elements; and (2) when the power system is subject to a fault, large transient currents and electric torque are induced in the superconducting armature and field windings, which may cause quenching in the windings. As to problem (1), it was shown that the generator could be stabilized in wide range of the operation by controlling the excitation voltage of the field winding in the authors' previous work. In this paper, problem (2) is addressed. The authors investigate methods to suppress the peak values of the transient currents in the armature and field windings and the transient torque by adjusting electric parameters of the generator and introducing superconducting current limiters (the inductance type and the resistance type). Characteristics of these methods are studied by numerical simulation and it is shown that the introduction of the resistance-type current limiter is the most effective. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (1): 15–27, 1997     

高温超导线圈在工频交流下的失超判断

运行于电力系统中的超导电力装置可能会遭受交流过电流故障,从而导致超导态转变到常态(失超),因此检测失超是超导电力装置实际应用的重要基础。然而在交流工作条件下,超导线圈产生很大的电感电压,其幅值远大于超导线圈失超后的常态电阻电压,给失超判断带来困难。笔者应用超导线圈在交流下电感电压和电阻电压的相位变化关系原理,经过实验研究,提出了基于相位变化的超导线圈在交流下的失超判断方法,为超导线圈在交流下的失超检测提供了新的技术途径。     

干式空心电抗器磁场和电感的计算分析

基于场-路耦合计算模型,采用有限元软件对干式空心电抗器的磁场和电感进行了计算和分析。以一种空心电抗器为例,给出了磁场分布图以及各个包封的电流和电流密度值。将电流、电感和损耗的计算值与实测值进行比较,表明场-路耦合计算方法具有较高的准确度,可满足空心电抗器的工程设计要求。