As important structural units, biomass nanomaterials have exhibited great potentials to construct high-performance macroscopic materials for broad applications by liquid assembly. However, the liquid aggregation of nanomaterials was less investigated. Here, we demonstrate that the one-dimensional (1D) zwitterionic chitin nanocrystals (ZChNCs) can be reversibly captured and released by two-dimensional (2D) planar catchers of graphene oxide (GO) sheets. The dominant electrostatic regulation strategy by pH variation drives that there are three reversible changes for the liquid aggregation of ZChNCs and GO, which were the isolated dispersion state (pH > 7), homogeneous hybridization state (7 ≥ pH ≥ 5), and partially stacked hybridization state (pH < 5), respectively. We found there are no sedimentation during the change of liquid aggregation with the higher absolute Zeta potentials (almost>30 mV). Moreover, the ZChNCs-GO nanohybrids have reached a maximum Zeta potential up to -80 mV, which can be explained by the ionization of excess carboxyl groups on the surface of ZChNCs. Besides, the electrostatic regulation endows the nanohybrids with rheological behavior, which is beneficial to the macro assembly of liquid nanomaterials. This work provides a new class of hybrid colloidal nanomaterials, opens the structural design dimension of macro assembly and holds great potentials in high-performance biodegradable material.

对绝缘纸热老化行为及其纤维素纤维折射率在热老化过程的演变规律进行了探究.分别在120℃和130℃下对油纸试样进行加速热老化试验,测得了不同老化时期的聚合度、糠醛含量、碳氧气体含量等特征量,探究其变化规律.根据试验中绝缘纸结晶度的变化趋势,对其折射率变化情况做出合理推论,并通过阿贝折光仪进行进一步分析.最后基于色散染色法,探究热老化时油纸纤维素纤维折射率的演变规律.结果表明:随着老化的进行,聚合度下降,糠醛含量、碳氧气体含量上升,绝缘纸的折射率和结晶度均变大,油纸纤维素纤维折射率也变大.可以考虑将纤维素折射率作为评估绝缘纸老化的新特征量.

通过对大量实测数据及26个省、自治区、直辖市统计数据的深入分析,确定了钢芯铝绞线压接结构的典型缺陷及其所占比例,系统分析了各种缺陷形成的原因.而后通过X射线成像和准静态拉力实验相结合的方法,研究了各种典型缺陷在不同尺寸下对压接结构承载能力的影响,结合试验结果分析了不同缺陷对承载能力影响的机理.研究结果表明,防滑槽漏压、防滑槽欠压和不压区压接为最主要的三种缺陷,其中防滑槽漏压、欠压以及铝管压接长度不够会增大钢芯承受载荷的占比,钢芯穿管不到位、钢芯断裂会增大铝绞线承担载荷的比例.

为提升纤维素绝缘纸的力学性能与热稳定性,利用KH550对纳米SiO2进行表面改性,将其掺杂到纤维素绝缘纸中,通过分子模拟建立不同接枝密度的纳米SiO2/纤维素复合模型,并对各模型的力学性能、均方位移、内聚能密度、溶解度参数和径向分布函数进行计算和分析.结果表明:KH550接枝密度为12.5％的纳米SiO2/纤维素复合模型抗形变能力最佳,并具有较大的内聚能密度和溶解度参数,改性效果最佳.

为提高交叉跨越线路的安全运行水平,以某220 kV交叉跨越线路作为研究对象,利用线性滤波法模拟大风工况和正常工况下的脉动风速时程曲线,对交叉跨越线路有限元模型进行动态分析计算,然后重点对金具的受力状态进行对比分析,找到易损位置,并提出相应的改进措施.结果表明:悬垂串球头挂环连接处受到的应力最大;两种工况下应力与许用应力的比值分别为0.35和0.44,和现场实测断裂位置吻合,需要重点注意;在球头和直棒连接处加厚,安全系数由1.5提高到1.6,可有效降低金具破坏风险.

Herein, a three-dimensional (3D) finite element model of a strain clamp-conductor system is established, with an NY-300/40 compression-type strain clamp taken as an example. The tensile load-carrying capacity of the strain clamp under standard crimping conditions is analyzed with LS-DYNA software, and the simulation results are compared with the experimental results to verify the accuracy of the model. On this basis, the tensile load-bearing capacity and failure mode of the strain clamp-conductor system are analyzed when the crimping length between the steel anchor and steel core is insufficient. Studies have shown that the grip strength of a strain clamp is provided mainly by the crimping between the steel anchor and the steel core. Under standard crimping conditions, the tensile load-bearing capacity of the strain clamp can meet the design requirements. Moreover, because the crimping length between the steel anchor and steel core is sufficient, the strain clamp fails due to aluminum strand breakage rather than the steel core being pulled out of the steel anchor. When the crimping length is insufficient, the grip strength of the strain clamp decreases with decreasing crimping length. Although the absolute value of the grip strength does not decrease significantly, the failure mode gradually changes from the breakage of the aluminum strands to the steel core being pulled out of the steel anchor. For the NY-300/40 compression-type strain clamp, the corresponding critical crimping length (i.e., when the change in failure modes occurs) between the steel core and the steel anchor is 50∼60 mm.

The accurate and fast diagnosis of transformer winding deformation faults is of significance to power suppliers and utilities. An improved winding mechanical deformation fault classification method is proposed. In this study, the transformer frequency response data is used to draw polar plots, and then its texture features are extracted for fault classification. The classification model constructed by multiple support vector machines is successfully obtained and shows good classification effect. Besides, this article uses an improved genetic algorithm based on the Emperor-Selective mating scheme and catastrophic operation, to optimize the parameters of support vector machine. The feasibility and accuracy of the proposed method are verified with experimental data obtained from a model transformer, and the proposed method is demonstrated to exhibit better performance compared with the traditional method.

以NY-300/40压缩型耐张线夹为对象,建立了耐张线夹-导线系统的LS-DYNA三维有限元模型,模拟研究了标准压接长度(110 mm)时耐张线夹的拉伸受力性能并与试验结果进行了对比,验证了模型的正确性,在此基础上分析了钢锚与钢芯压接长度变化时耐张线夹的抗拉承载特点.研究表明,耐张线夹的握力主要来自于钢锚与钢芯的压接.标准压接情况下,耐张线夹的抗拉承载力能满足设计要求,而且由于压接长度足够,其失效方式是铝绞线断裂而非钢芯从钢锚中拉脱.当钢锚与钢芯压接长度不足时,随着压接长度的减小,耐张线夹的握力亦逐渐减小,虽然其握力绝对值减小幅度不大,但其破坏模式逐渐由铝绞线断裂转变为钢芯被从钢锚中拉脱,就本文的分析对象而言,破坏模式发生转变时钢芯与钢锚间的临界压接长度在50～60 mm.

Received: 2 December 2019 Accepted: 17 February 2020 Through long-term operation, transformers often encounter internal faults. The traditional detection methods of these faults face several constraints, namely, limited space, heavy workload, and dense elements. To resolve these constraints, this paper designs an internal fault detection system for transformer based on wall-climbing robot. In the hardware part, the main controller receives the information captured by visual sensors, and controls the electromagnetic driving mechanism, such that the wall-climbing robot could walk against the walls inside the transformer and detect the internal defects. In the software part, socket programming was performed to design WIFI Connect, face recognition, and interface programs, providing a visual display and real-time transmission of fault information. Finally, our system was applied to detect the insulation discharge faults inside transformers of two substations. The fault locations of the two cases were quickly identified: shielding paper and corner ring for Case 1, and voltage regulating coil and iron core piece for Case 2. The results show that our system can detect the internal defects of transformer efficiently at a low cost. The research results shed new light on the intelligent, unmanned detection of internal faults of transformer.

TEMPO-mediated oxidation has been successfully used to prepare carboxylated chitin nanofibers (ChNFs) with purified chitins originating from the outer shells of crab and shrimp (alpha-form) or tubeworm (beta-form). However, the method for obtaining carboxylated ChNFs with squid pen chitin (hydrated beta-form) has not been developed yet. It might be due to the existence of the small amount of partial deacetylation (DD approximate to 9%) in the squid pen beta-chitins. Herein, ultrafine (2-4 nm in width and several micrometers in length) and carboxylated beta-ChNFs were fabricated directly from the squid pen with simultaneously removing of protein, CaCO3 and other non-chitin components by one-step oxidation procedure using ammonium persulfate (APS) and followed ultrasonic disintegration under acid conditions. When 45 wt% APS was used to react with squid pen, the carboxylate content of ChNFs reaches 0.802 mmol/g. Therefore, the beta-ChNFs with anionically charged groups (COO-) can be dispersed stably in aqueous solution under basic conditions. Meanwhile, thus-obtained beta-ChNFs aqueous solution even with very low concentration (0.8%) can be transformed to transparent, robust and moldable hydrogels by gas coagulation of acetic acid.

通过鸟粪影响情况下,绝缘护套在220 kV线路上不同缠绕方式的耐受性试验和缠绕绝缘护套后临界危险区域划分试验,证明了绝缘护套在220 kV线路上能有效防止鸟粪通道跟均压环之间的放电,降低了鸟粪闪络的概率.由此提出,绝缘护套作为一种新型防鸟粪闪络装置,用于改善鸟粪闪络事故是比较有效可行的.

Based on the commercial general finite element software ABAQUS, the simulation model of service process of die forging joint of steel-cored aluminum splicing sleeve was constructed. The load distribution and the change of relative sliding between aluminium stranded conductor and aluminium pipe of the joint were calculated by using the established simulation model. The results indicate that with the increase of the asymmetry degree of die forging (the steel pipe deviating from the center of aluminium pipe), both the stress concentration at the contact point/surface and the relative sliding between the aluminium tube and the aluminium strand conductor increases, which leads to the increase of the load proportion of the steel core. The simulation results well explain the crack of connecting pipe in transmission line operation.

Novel hybrid nanomaterials composed of graphene and chitin nanofibers (ChNFs) were successfully prepared by one-pot ball milling. Under strong shear and collision force of ball milling, graphite was exfoliated to mono-layer or few-layer graphene with the assistance of chitin nanofibers. Unexpectedly, the hybridization of exfoliated graphene and ChNFs was realized simultaneously. Morphology analysis observed that the ChNFs were adsorbed tightly on the surface of graphene, providing for reduced graphene hydrophobicity and enhanced stability of the hybrid dispersion. In addition, the concentration of exfoliated graphene reaches up to 1.5 mg ml(-1). Strong interaction between graphene and ChNFs may benefit from the large amounts of carboxylate groups on the surface of ChNFs, which was prepared by TEMPO-mediated oxidation of chitin. As prepared graphene/ChNFs hybrids can remarkably enhance both the tensile strength and toughness of Poly(vinyl alcohol). This study provides a green, simple and large-scale synthesis method for preparing water-dispersible graphene/ChNFs hybrid nanobuilding blocks, which shows great promise potential in various applications requiring biocompatibility, hydrophilicity, electrical conductivity and strong mechanical properties.

特高压交直流输变电工程承担全球能源互联网的重要使命,其中外绝缘污秽特性是制约其安全运行的重要因素.本项目利用首批投运的特高压1,000千伏交流和±800千伏直流线路并行段,设置了首个在运特高压交、直流污秽对比试验站,并开展全线污秽测量.在特高压直流污区图绘制方法与应用、实际运行特高压交直流污秽特性、输变电设备污秽数据挖掘分析技术三个层面取得创新和突破.

针对±800 kV某特高压直流线路玻璃绝缘子集中自爆问题,本文对线路沿线省份玻璃绝缘子自爆情况进行了统计,对玻璃绝缘子集中自爆的规律和原因进行了分析.根据线路自爆情况,对自爆绝缘子按生产厂家、自爆位置、污区等级、自爆月份和是否涂RTV进行统计分析,发现,玻璃绝缘子厂家间的自爆情况存在明显的差异性;自爆位置沿串分布大致呈"马鞍"形,与电场分布有较好的一致性;自爆故障大多发生在夏季,且污秽等级对自爆故障存在影响;是否涂RTV涂料对自爆影响不大.结果表明:产品质量问题是发生集中自爆的重要原因,电场强度对绝缘子自爆存在重要影响,绝缘子表面污秽、温差和机械载荷也对自爆存在影响.

Nitrogen-enriched (N-enriched) carbon nanofiber aerogels (NCNAs) with an ultrafine nanofiber network structure were designed and prepared by using chitin nanofiber aerogels as the precursor. Because of the uniform nanofibrous architecture and nitrogen-rich composition of chitin nanofiber aerogels, the NCNAs exhibited large specific surface area (4901597 m(2) g(-1)) and a high nitrogen content (2.07-7.65%). As a consequence, supercapacitor electrodes prepared from NCNA-900 showed specific capacitances as high as 221 F g(-1) at the current density of 1.0 A g(-1) and good capacitance retention of 92% over 8000 cycles in a 6.0 mol L-1 KOH electrolyte without further activation. Moreover, the NCNA-900 could also be applied as an effective adsorbent for dye adsorption, such as Congo red (496 mg g(-1)) and Rhodanine B (489 mg g(-1)). In view of an excellent electrochemical performance and high adsorption capacities for dyes as well as cost-effective and eco-friendly approaches, NCNAs derived from marine chitin show great potential for application in energy storage and environmental remediation.

针对一起220kV电缆终端击穿故障,结合解剖检查,笔者分析认为,故障原因为应力锥安装工艺质量不佳,造成应力锥与电缆接触面位置存在局部放电,持续作用下造成电缆绝缘和应力锥绝缘老化且绝缘强度下降,最终导致电缆击穿,由此提出相应的防范措施.

A rapid and high-yield (up to 85%) preparation of a zwitterionic chitin nanofiber (DE-CO-ChNF) has been demonstrated.

对2003-2015年间,国家电网涉鸟故障相关信息进行统计分析.2013年1月-2015年5月,采用样线法和样点法对河南省域高压输电线路鸟类多样性进行调查;对记录到涉鸟故障相关鸟类进行统计分析,依据涉鸟故障的类型、发生频次、分布区域、居留类型等指数分析,高危种类主要有:喜鹊、灰喜鹊、大嘴乌鸦、秃鼻乌鸦、黑鹳、东方白鹳、大鵟、红隼、黑领椋鸟、丝光椋鸟等.对主要涉害鸟类的生物学习性、识别特征进行分析,对危害类型、鸟害的机理进行探讨.