高温超导电缆研究进展综述

人们对电能需求的持续增长,促使电网输电密度和输电容量逐渐增大,传统的输电技术将遇到越来越多的问题。高温超导电缆具有传输容量大和功率密度高等优势,是解决这些问题和满足未来大容量电力传输的重要技术之一。在综合分析国内外大量文献资料的基础上,介绍高温超导电缆的基本结构、发展现状和关键技术,总结制约其工业化应用过程当中面对的主要问题,并提出了高温超导电缆的发展建议。     

高温超导电缆在城市地下输电系统应用的可行性研究

本文通过对交流高温超导电缆系列设计计算对额定电压35kV、110kV、220kV的高温超导电缆,按不同传输电流(或传输容量),以高温超导电缆的传输效率(损耗与传输容量比)、高温超导电缆外径限值和超导导体绕制结构限制条件,确定高温超导电缆适用性界定条件,提出城市地下输电、配电系统用高温超导电缆可行方案.     

高温超导电缆暂态热过程仿真研究

高温超导电缆输电技术作为一种新型电力传输技术,已成为当前电力传输技术的重要发展方向之一.当高温超导电缆运行在电力系统中时,必将经受诸如系统短路故障电流、瞬时大负荷冲击等各种故障电流冲击,高温超导电缆的传输能量较高,一旦发生故障,不仅会对高温超导电缆本体造成损伤,还会严重影响其供电可靠性乃至整个电力系统的稳定性.为保证电力传输系统的安全稳定运行,对超导电缆失超的热过程进行研究是非常有必要的.本文首先介绍了超导电缆失超的暂态热过程数学模型,接着确定了其边界条件,最后在Matlab中,对超导电缆在电流冲击下的热过程进行了仿真研究.     

高温超导直流电缆现状

文中对高温超导直流电缆现状进行了介绍。高温超导直流电缆是用于直流输电的高温超导电缆。高温超导直流电缆发展相对落后于高温超导交流电缆,国际上示范项目也较少。但随着轻型直流输电应用的逐渐发展,高温超导直流电缆越来越引起人们的重视。高温超导直流电缆的本体结构和高温超导交流电缆本体结构类似。高温超导直流电缆具有输电损耗小、适合长距离输电、增加电网稳定等功能。比较适用于背靠背直流输电,工业直流输电,互联网数据中心直流供电,远距离、大容量直流输电等场合。此外,还介绍了目前国际上主要的超导直流电缆项目及研究机构情况。     

高温超导导线在低平行磁场下传输性能的研究及其在电缆应用中的影响

在迄今流行的认知当中,第二代高温超导导线相对于一代导线具有更优良的磁场性能,然而本研究发现在液氮温度和低平行场(平行于导线宽面)的条件下实际情况恰好相反。文中通过测量研究和文献调研相结合,确认了这一现象的可靠性。高温超导电缆在远距离输电和大型城市输电方面都具有显著的性能优势,必将为我国电力能源领域带来重大的技术变革。而在高温超导电缆等应用技术中,低平行场是典型的使用条件,根据本研究得到的数据并考虑到价格因素,目前一代导线在这些应用领域中具有明显的相对优势。     

基于FBG的直流高温超导电缆失超检测

高温超导电缆输电具有损耗小、传输密度高、无电磁污染等特点,越来越受到各国的重视。但是当超导电缆发生失超故障时,产生的焦耳热会影响电缆的绝缘,使电缆无法正常运行。快速准确的失超检测就显得尤为重要。设计制作了一条高温超导电缆的模型,并搭建了高温超导电缆的测温与保护平台,采用光纤光栅测温对其失超之后铜骨架的温度变化进行测量,结合理论分析与仿真计算,论证了光纤光栅能满足对于高温超导电缆失超检测的要求。该方法具有反应速度快、结构简单的特点,可用于检测采用Triaxial结构和实心骨架的高压交直流超导电缆失超故障,为高温超导电缆的失超检测技术的实际应用提供了参考依据。     

液氢温区YBCO超导带材的交流损耗研究

超导电缆具有载流能力强、损耗低等优势,是电力输送的良好选择。但是,超导电缆需工作于低温环境。液氢温度为20K,可为超导电缆提供低温条件,将超导电缆输电与液氢燃料输送相结合,可解决超导电缆在输电中的瓶颈问题。开展了液氢替代液氮后高温超导带材的传输交流损耗研究。针对美国超导公司提供的黄铜加强YBCO带材,采用H法有限元模型,仿真分析了液氢、液氮冷却时超导带材的传输交流损耗。结果表明采用液氢作为超导带材的冷却介质时,带材正常金属产生的涡流损耗和磁性基底产生的铁磁损耗对总损耗的影响程度较小。所得结果可为液氢温区超导电缆的设计和运行提供参考。     

交流高温超导电缆构型研究综述

高温超导电缆相对于常规电缆,具有载流能力高、结构紧凑、传输损耗小等优势,在大规模电力传输或走廊受限的线路扩容方面,具有发展潜力。近二十年来,国内外已有多组电缆进行试验验证或投入示范运行。通过回顾交流高温超导电缆的构型研究,介绍了较为常见的三相独立式、三芯式和三相同轴式结构,同时还介绍了几种新型交流高温超导电缆构型,如悬挂架空式、扭曲堆叠式、圆芯式、双同轴式和快速冷却式等,分析了各种不同构型交流超导电缆的特点,梳理出交流超导电缆改进的技术路线和发展趋势。     

液氮下绕包绝缘的电性能研究

高温超导电缆具有载流能力大、损耗低和体积小的优点,传输容量将比常规电缆高3~5倍,而电缆本体的焦耳热损耗几乎为零。因而,高温超导电缆相对于常规电缆具有极大的优势,其研制水平也在迅速提高。超导电缆中,其绕包绝缘的性能对于超导电缆稳定运行起着十分重要的作用。随着超导电缆的电压等级的提高,对绝缘的性能要求也随之提升。用PPLP,100HN,100CR,150FCR019绕制绕包绝缘并测试了它们的击穿性场强,并对它们的击穿性能进行对比分析,为超导电缆绝缘的选材和设计提供参考。     

高温超导限流电缆研究现状与发展趋势综述

高温超导限流电缆是一种新型超导电缆,充分利用了第二代高温超导体的优势,在电力系统正常和故障状态时分别表现低阻抗载流和高阻抗限流特性。高温超导限流电缆集成了超导电缆与超导限流器两种超导电力装备的功能。对于超导电缆和超导限流器,分别都有相关研究综述,而对于高温超导限流电缆缺乏系统性综述研究。从高温超导限流电缆的原理与结构出发,综述国内外有关高温超导限流电缆的研究现状,针对面临的技术问题进行分析。总结出高温超导限流电缆动态电流分布、载流限流瞬态变化过程、高温超导限流电缆接入到电力系统的新拓扑结构等关键技术和基础科学问题,获得了高温超导限流电缆未来的发展方向和趋势。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.