基于多传感器的分台区线损异常信号定位方法

为了精准定位全景电网分台区线损信号，提高线损异常信号检测识别能力，提出基于多传感器的智能全景电网分台区线损异常信号定位检测方法。采用多源异构的参数识别和传感器组网控制方法，构建智能全景电网分台区线损异常信号的时域模型；通过多维参数识别和多维传感器参数定位，辨识智能线损信号阵列参数，检测智能全景电网分台区线损异常信号的特征；分析线损异常信号的稳定性特征分量，定位异常信号。试验结果表明，所提方法的异常信号定位精度达到了60%以上，能够对线损信号精准定位，提高了异常信号检测性能。     

基于梯度算法的低压台区线损异常实时检测方法

针对传统线损异常检测方法缺乏规范的体系、智能化程度较低,为电网台区带来一定风险的问题,提出基于梯度算法的低压台区线损异常实时检测方法。利用数据挖掘算法挖掘低压台区线损异常数据,作为检测方法的数据支持,通过预处理线损异常数据恢复缺失值,引入梯度算法得到用于识别线损状态的梯度计算公式作为检测依据,建立一个低压台区线损异常实时检测模型。实例应用结果表明,该方法可准确识别低压台区线损异常原因,且具有96.6%的异常检测查全率。     

基于边缘计算的低压用户窃电检测

低压用户窃电导致线损电量增加,对台区线损异动进行归因分析是识别窃电用户的有效途径。低压用户通信异常多发,可导致用电信息采集系统主站数据失真,易误导窃电检测。利用配变终端可就地完整准确采集台区数据的特点,提出基于边缘计算的低压用户窃电检测方法。首先,在通信正常和异常的条件下,分析台区窃电用户用电量与线损电量的关联关系;然后,在配变终端窃电检测模块中对真实的台区线损和用户用电量进行归因分析来识别窃电用户;最后,基于高损台区实际数据的仿真分析,验证了所提方法相比于在主站侧采用异常数据以及采用不同缺失数据填补算法修复后的数据进行窃电检测时的优势。     

计及用户侧数据不确定性的台区线损粗糙算法

台区线损治理是电网公司消费侧运营管理的核心议题,也是提质增效保障电网利润的基础。依托安装的电能信息采集终端,电网营销系统采集维护着海量的用户数据,利用实时采集的电网大数据去探知电网的运行情况并进行及时的维护是台区线损治理的有效途径。电网监测采集的数据量虽然庞大,但面对复杂的台区线损不合格原因仍然捉襟见肘。利用已知的采集数据,建立数据与故障原因之间的因果关系链可极大的减轻运维人员的工作压力,提升线损治理水平。海量的监控终端在采集、通信与维护的过程中必然存在着数据的不准确性,提出利用粗糙集理论解决用户侧数据的不确定性,给出了不同故障下的特征数据,分析了故障与数据的内在联系,实现了故障参数特征数据的解耦。给出了导致台区故障原因的分类,并验证了所提出分类方法的正确性。     

基于知识图谱的台区线损异常分析

电网公司的基本职能之一是提供安全可靠的电能,而线损率是衡量电能质量及电网经济效益的核心标准.能够及时发现并解决台区线损异常是电网公司关注的重点.近年新兴的知识图谱技术能够清楚地描述实体之间的关系,并能将复杂的自然语言转化成脉络清晰的三元组,因此,可将知识图谱技术运用到台区线损异常原因判断中.根据电网信息系统中的电力数据构建出台区线损异常知识图谱,分析各类异常原因特征并构建判断规则,经过推演格算法优化构建出台区线损异常原因判断方法.经实例验证,所提方法在台区线损异常原因判断方面的准确度优于电网方法,并极大地提升了判断速度,具有实用性和高效性,为知识图谱技术在电力行业的应用提供了新思路.     

台区线损合理性分析模型研究与应用

线损是衡量供电企业经营状况的重要指标。利用海量历史数据构建台区线损合理性分析模型,将台区划分为多个类别,在此基础上构建并应用台区线损异常判定工具,提高线损异常识别准确率,实现台区线损的精益化管理。     

考虑气象因素的台区线损异常智能识别模型及应用

在气候多变的山区,天气情况对台区实时线损波动影响较为严重,但在目前的线损管理中,并未充分考虑气象因素对线损的影响。利用基于距离和密度的局部离群因子检测算法,建立考虑气象因素的台区线损异常智能识别模型,快速有效识别易受气象因素影响的台区,评估异常天气对台区日线损的影响程度,并结合实时和预报气象信息,建立台区线损异常情况预警模型。最后以天气多变的某县供电公司为例进行实证分析,结果表明考虑气象因素的台区线损异常智能识别模型可有效识别线损易受异常天气影响的台区,为区县供电所开展台区线损治理提供依据,辅助提升台区线损精细化管理。     

基于k-means聚类算法的低压台区线损异常辨别方法

目前电力公司对于台区线损异常的判断是当线损率超过一定阈值时为线损异常,这样的判断具有片面性和局限性。针对如何有效辨别线损异常的问题,在研究聚类算法和线损率数据特性的基础上,提出了一种基于k-means聚类算法的线损异常辨别方法。首先将低压台区线损率进行一次k-means聚类分成3类,然后根据各类数据的数量状况判断是否进行二次分类,最终根据平均线损率的大小、聚类中心的距离等因素,判断该低压台区是否存在线损异常,对聚类结果中线损率高的那一类数据的时间离散度进行分析,得到低压台区线损异常的程度。实验结果证明,该方法具有一定的实际应用效果,可以提高线损异常判断的准确性。     

基于K-Medoids聚类的分布式光伏台区线损异常感知算法

为保证分布式光伏台区稳定运行,精准有效地划分台区线损数据,提出基于K-Medoids聚类的分布式光伏线损异常感知算法,精准判断分布式台区线损异常程度。采用局部异常因子（LOF）算法判断分布式光伏台区数据局部异常程度,并筛选和去除受孤立点影响产生的异常线损数据。采取K-Medoids聚类方法聚类分析筛选后的分布式光伏台区数据,将异常线损率区间结合异常线损数据的聚类中心和欧式距离,完成台区线损异常感知。并创新性地引入粒度计算优化K-Medoids聚类算法聚类中心,提升异常数据感知效果。试验结果表明,所提算法可有效避免孤立点对异常感知效果的影响,精准有效地感知分布式光伏台区线损异常,并清晰划分台区线损数据类别。     

基于电能计量采集物联网的多维线损治理技术研究与应用

为解决低压台区线损合格率低、治理困难等问题,本文依据一套完整的电能计量采集物联网系统,通过其本身的台区识别技术、采集大数据分析等功能,为电力公司管理、计量设备异常及其他人为原因等造成的各种低压台区线损提供了多维治理手段,对电网结构和用户性质复杂的低压台区线损治理提供了有力的技术支撑,切实提升台区线损精益化管理水平,为电...     

Thermoelectric properties of Bi and Cu co-doped Ca3Co2O6single crystals

Single crystals of Bi and Cu-doped Ca₃Co₂O₆were synthesized in a molten K₂CO₃flux. Using an obtained single crystal of (Ca_0.985(5)Bi_0.015(5))₃(Co_0.990(3)Cu_0.010(3))₂O₆elongated to the c-axis direction of the crystal structure, the electric resistivity (ρ) and Seebeck coefficient (S) were measured from room temperature to over 1000 K in air. The single crystal showed p-type semiconducting behavior with ρ values of 1.8 Ω cm at 303 K and 0.017 Ω cm at 1000 K. The S values were +254 μ VK^{− 1} at 325 K, +360 μ VK^{− 1} at 420 K, and +214 μ VK^{− 1} at 1000 K. The power factor (S ² ρ ^{− 1}) increased with an increase of temperature and attained 2.70 × 10^{− 4} Wm^{− 1}K^{− 2} at 1000 K.     

电力系统概率小扰动稳定性研究进展

随着电力系统新能源渗透率的不断增大,考虑到新能源具有随机性强、波动性大等特征,会对高渗透率的新能源电力系统小扰动稳定性产生影响,从而制约电力系统的发展。为此,文章着重针对小扰动的来源、对电力系统的影响以及分析方法进行了总结归纳,首先简要介绍了小扰动的相关概念,后从风电等不确定新能源发电、电动汽车等新型负荷接入电网以及网络安全三方面阐述了各自对电力系统的影响,并对小扰动分析方法进行归类,分析了蒙特卡洛法(MCM)、随机响应面法(SRSM)和概率分配法(PCM)的相关原理以及研究现状。最后介绍了现阶段小扰动的抑制措施并提出了对未来电网发展方向的一些思考。     

Quality assurance of PASADENA hyperpolarization for 13C biomolecules

Object  Define MR quality assurance procedures for maximal PASADENA hyperpolarization of a biological ¹³C molecular imaging reagent. Materials and methods  An automated PASADENA polarizer and a parahydrogen generator were installed. ¹³C enriched hydroxyethyl acrylate, 1-¹³C, 2,3,3-d₃ (HEA), was converted to hyperpolarized hydroxyethyl propionate, 1-¹³C, 2,3,3-d₃ (HEP) and fumaric acid, 1-¹³C, 2,3-d₂ (FUM) to hyperpolarized succinic acid, 1-¹³C, 2,3-d₂ (SUC), by reaction with parahydrogen and norbornadiene rhodium catalyst. Incremental optimization of successive steps in PASADENA was implemented. MR spectra and in vivo images of hyperpolarized ¹³C imaging agents were acquired at 1.5 and 4.7 T. Results  Application of quality assurance (QA) criteria resulted in incremental optimization of the individual steps in PASADENA implementation. Optimal hyperpolarization of HEP of P = 20% was achieved by calibration of the NMR unit of the polarizer (B ₀ field strength ± 0.002 mT). Mean hyperpolarization of SUC, P = [15.3 ± 1.9]% (N = 16) in D ₂O, and P = [12.8 ± 3.1]% (N = 12) in H ₂O, was achieved every 5–8 min (range 13–20%). An in vivo ¹³C succinate image of a rat was produced. Conclusion  PASADENA spin hyperpolarization of SUC to 15.3% in average was demonstrated (37,400 fold signal enhancement at 4.7 T). The biological fate of ¹³C succinate, a normally occurring cellular intermediate, might be monitored with enhanced sensitivity.     

Thermal and dielectric properties of ZnO-B2O3-MO3glasses (M = W, Mo)

Glasses in the ZnO-B₂O₃-MO₃(M = W, Mo) ternary were examined as potential replacements to PbO-B₂O₃-SiO₂-ZnO glass frits with the low firing temperature (500–600^∘C) for the dielectric layer of a plasma display panels (PDPs). Glasses were melted in air at 950–1150^∘C in a narrow region of the ternary using standard reagent grade materials. The glasses were evaluated for glass transition temperature (T _g ), softening temperature (T _d ), the coefficient of thermal expansion (CTE), dielectric constant (ε _r ), and optical property. The glass transition temperature of the glasses varied between 470 and 560^∘C. The coefficient of thermal expansion and the dielectric constant of the glasses were in the range of 5–8 × 10^{− 6}/^∘C and 8–10, respectively. The addition of MO₃to ZnO-B₂O₃binary could induce the expansion of glass forming region, the reduction of T _g and the increase in the CTE and the dielectric constant of the glasses. Also, the effect of the addition of MO₃to ZnO-B₂O₃binary on the transmittance in the visible-light region (350–700 nm) was investigated.     

Investigation on the design and synthesis of new systems of BNT-based lead-free piezoelectric ceramics

Three primary differences between BNT- and PZT-based ceramics were analyzed from the composition and the active component of the materials. Based on the analysis the authors’ group developed the new idea of the design of the multiple complex in the A-site ions of BNT compounds. (Bi_0.5Na_0.5)²⁺, Bi³⁺ and Na⁺ in the ABO₃ structure are defined as A-site, A₁-site and A₂-site ions, respectively, and A, A₁ and A₂-site ions can be simultaneously or singly substituted partially by alkaline-earth metal ions, metal ions with +3 valence and metal ions with +1 valence, respectively. Under this consideration, Several new systems of Bi_0.5Na_0.5TiO₃ (abbreviated as BNT)-based lead-free piezoelectric ceramics were proposed. These ceramics can be prepared by conventional ceramic techniques and have excellent piezoelectric performance. Among these materials, Bi_0.5(Na_1−x−y K _x Li _y )_0.5TiO₃ possesses higher piezoelectric constant (d ₃₃ = 230 pC/N), higher electromechanical couple factor (k _p = 0.40), larger remanent polarization (P _r = 38.9 μC/cm²) and a better P-E hysteresis loop until about 200^∘C. This work was supported by the projects of NSFC (50410179), (50572066), and (59972020), and NAMMC (2001-AA325060).     

Preparation of SnO2 whiskers via the decomposition of tin oxalate

A new method for preparing SnO₂ whiskers by the decomposition of SnC₂O₄ is suggested. A Whisker-like morphology of a SnC₂O₄ precipitate was attained via the gradual addition of an oxalic acid solution to a hot SnCl₂ aqueous solution (T > 50^∘C). In comparison, when the solution temperature was either lower than 50^∘C or when ethanol was used as the solvent, the SnC₂O₄ precipitate showed an angular and relatively isotropic morphology. The morphology of the SnC₂O₄ precipitate remained even after its thermal decomposition into SnO₂ at 400^∘C indicating that SnC₂O₄ precipitation is a key step in preparing the whiskers. The formation mechanism of SnO₂ whiskers was explained by the supersaturation during the precipitation of SnC₂O₄.     

Co-Modification of Ba5NdTi3Ta7O30 Dielectric Ceramics by Substitution and Introducing Secondary Phase

Co-modification of Ba₅NdTi₃Ta₇O₃₀ dielectrics ceramics was investigated through Pb substitution for Ba and introducing Bi₄Ti₃O₁₂ secondary phase. The dielectric constant increased from 150 to 283, the temperature coefficient of the dielectric constant decreased from –2500 ppm/°C to –1279 ppm/°C, and the dielectric loss decreased to 0.0007 at 1 MHz. Meanwhile, the bi-phase ceramics were investigated to achieve temperature stable ceramics with high dielectric constant and low dielectric loss. As the composition x varied from 0.4 to 0.7 for (1 – x)(Ba_0.8Pb_0.2)₅NdTi₃Ta₇O₃₀/xBi₄Ti₃O₁₂, the temperature coefficient of the dielectric constant changed from negative to zero to positive.     

Hydrogenation induced transformation of paramagnetism to room-temperature ferromagnetism in co-doped TiO2 ceramics

Effects of Co _x Ti _1−x O _2−δ on the sinterability and the ferromagnetism properties of Co ₂sO ₃/TiO ₂ (0.0 < x < 0.06) ceramics are investigated in this paper. It is found that the Co-doped Ti O ₂ ceramics transform from paramagnetism to room-temperature ferromagnetism (RTFM) after hydrogenation. With annealing temperatures at 600^∘ C and 1000^∘ C, these as-prepared samples present anatase and rutile structures respectively, which are analyzed with X-ray diffraction (XRD). After hydrogenation, the relation between temperature variations and the magnetic susceptibility for the hydrogenated samples were measured under zero-field-cooled and field-cooled conditions by using SQUID magnetometer. And the hysteresis loops are observed. These ferromagnetism resonance data suggest that the observed RTFM is at least partly due to the Cobalt nano-particles in our hydrogenated samples.     

Oxygen permeation properties and surface modification of acceptor-doped CeO2/MnFe2O4 composites

The preparation and oxygen permeation properties of the (Ce_0.8Pr_0.2)O_2−δ − x vol% MnFe₂O₄ composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce_0.8Pr_0.2O_2−δ, an oxygen flux density of 6 μmol⋅cm⁻²⋅s⁻¹ (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000^∘C. Unlike composites consisting of Gd-doped CeO₂ and MnFe₂O₄, the oxygen permeability of the (Ce_0.8Pr_0.2)O_2−δ – x vol% MnFe₂O₄ composites was almost constant regardless of the volume fraction of MnFe₂O₄; however, the optimum volume fraction of MnFe₂O₄ was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere. In addition, the surface modification of the (Ce_0.8Gd_0.2)O_2−δ – 15 vol% MnFe₂O₄ composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm² on the both side of the 0.3 mm-thick (Ce_0.8Gd_0.2)O_2−δ – 15vol% MnFe₂O₄ composite increased the oxygen flux density from 0.30 to 0.76 μmol⋅cm⁻²⋅s⁻¹ in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by a large pO₂ gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce_0.8Gd_0.2)O_2−δ – 15vol% MnFe₂O₄ composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition of the LB film.