电缆附件冷热交替循环电压试验方法研究

电缆终端的电气绝缘是电缆系统的绝缘薄弱环节,针对运行于高寒地区的电缆附件,提出采用冷热交替循环电压试验进行试验考核,并基于电缆附件的热循环电压试验方法,提出电缆附件冷热交替循环电压试验方法,以GIS终端为试品进行试验研究,研究结果可为运行于高寒地区的电缆系统附件提供试验考核方法。

345kV XLPE绝缘电力电缆系统热循环电压试验温度的精确检测

文章介绍了根据标准AEIC CS 9-15、IEC 62067:2011进行345kV XLPE绝缘电力电缆系统热循环电压试验影响温度测量的因素,进行了合理的改进,保障该电缆在热循环电压试验过程中温度能够得到精确的控制及测量,使得试验过程中电缆导体温度、表面温度、环境温度误差减小,提高试验的精准性。

MPA包覆的银纳米粒子修饰电极制备和电化学表征

运用自组装和电化学组装法,将MPA包裹的银纳米粒子修饰到金电极表面,制备成银纳米粒子单层和多层膜修饰电极.循环电压电流和电化学阻抗谱测定结果表明:以MPA包覆的银纳米粒子修饰电极的氧化电位明显负移,显示出银纳米粒子具有更高的活性.以0.5 mmol/L的K3[Fe(CN)6]溶液为检测体系,电化学阻抗谱测试得出电极表面对探针分子的阻碍作用有所增加.循环电压电流结果表明:与单层膜修饰电极相比,多层膜修饰电极的峰电流显著增加.

正负极互换式小球藻光合微生物燃料电池性能

交替利用小球藻的光合作用和呼吸作用,设计、搭建了正负极交替互换式微藻燃料电池模型,考察了该电池的启动时间,产电性能与燃料（还原糖）浓度、温度等影响因素的关系,最后探讨了该电池的产电机理。结果表明：电池构建成功并产电,启动电池时间大约400 min。运行过程中,还原糖浓度变化在4.38~6.0 g/L时,电压保持稳定。在45~50℃范围内,该电池表现出良好的工作性能,输出电压达到550 m V。电池经过多次正负极交换后,电压绝对值呈循环变化趋势。碳毡电极表面可见明显的小球藻生物膜,据此推测,生物膜上产生的电子通过电极直接经外电路传递到阴极,而阴极则如设计,小球藻光合作用产生的氧气接收电子。建议可提高小球藻在电极表面形成生物膜的速度来提高电池的性能。

混凝土与碳纤维混凝土材料的电阻率变化研究

制备了素混凝土及纤维含量不同的碳纤维混凝土材料,并对其在循环电压加载下的电阻率进行了测试。分析表明,电场对材料的电阻率有很大的影响,随着电压加/卸载循环次数的增加,素混凝土的电阻率逐渐升高,直至内部的水化再次达到平衡时,电阻率保持不变;在同一次循环中,卸载时的电阻率高于加载时的电阻率。加入碳纤维后,混凝土的电阻率变化幅度变小,电场对电阻率的影响变弱,并且阐述了引起这种变化的原因。

Mechanical and electrical properties of coarse-grained soilaffected by cyclic freeze-thaw in high cold regions

To evaluate the geotechnical properties of coarse-grained soil affected by cyclic freeze-thaw,the electrical resistivity and mechanical tests are conducted.The soil specimens are prepared under different water contents,dry densities and exposed to 0?20 freeze-thaw cycles.As a result,the stress?strain behavior of the specimen(w=14.0%andρd=1.90 g/cm^3)changes from strain-hardening into strain-softening due to the freeze-thaw effect.The electrical resistivity of test specimen increases with the freeze-thaw cycles change,but the mechanical parameters(the unconfined compressive strength qu and the deformation modulus E)and brittleness index decrease considerably at the same conditions.All of them tend to be stable after 7?9 cycles.Moreover,both the dry density and the water content have reciprocal effects on the freeze-thaw actions.The failure and pore characteristics of specimens affected by freeze-thaw cycles are discussed by using the image analysis method.Then,an exponential function equation is developed to assess the electrical resistivity of specimens affected by the cyclic freeze-thaw.Linear relations between the mechanical parameters and the electrical resistivity of specimens are established to evaluate the geotechnical properties of the soil exposed to freeze-thaw actions through the corresponding electrical resistivity.

High tap density of Ni_3(PO_4)_2 coated LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 with enhanced cycling performance at high cut-off voltage

The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by electrochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer(ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated Li Ni1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99% capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy(EIS) results show that the current exchange density i0 of the coated sample is higher than that of Li Ni1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2coating can prominently enhance the high rate performance of the Li Ni1/3Co1/3Mn1/3O2, especially at high cut-off voltage.

Low cycle fatigue properties and cyclic deformation behavior of as-extruded AZ31 magnesium alloy

The low cycle fatigue(LCF)properties of as-extruded AZ31 Mg alloy were investigated under total strain amplitudes in the range of 0.4%-1.2%with strain rate of 1×10- 2s -1.Due to the twinning effect in compression during loading and the detwinning effect during unloading,the alloy showed an asymmetric hysteresis loop.The cyclic stress response exhibited cyclic hardening at high total strain amplitudes.The cyclic deformation behaviors were discussed using the Coffin-Manson plot,which divided the plastic strain amplitudes into the tension side and the compression side.Through the LCF tests that were started from either tension or compression under a total strain amplitude of 1.0%,the interaction between the twinning effect and dislocation was analyzed.The twinning effect during the LCF test and the variation of the dislocation density were investigated using optical microscopy and transmission electron microscopy,respectively.

Dual Pressure versus Hybrid Recuperation in an Integrated Solid Oxide Fuel Cell Cycle--Steam Cycle

A SOFC （solid oxide fuel cell） cycle running on natural gas was integrated with a ST （steam turbine） cycle. The fuel is desulfurized and pre-reformed before entering the SOFC. A burner was used to combust the remaining fuel after the SOFC stacks. The off-gases from the burner were used to produce steam in a HRSG （heat recovery steam generator）. The bottoming steam cycle was modeled with two configurations： （1） a simple single pressure level and （2） a dual pressure level with both a reheat and a pre-heater. The SOFC stacks in the present SOFC-ST hybrid cycles were not pressurized. The dual pressure configuration steam cycle combined with SOFC cycle （SOFC-ST） was new and has not been studied previously. In each of the configuration, a hybrid recuperator was used to recovery the remaining energy of the off-gases after the HRSG. Thus, four different plants system setups were compared to each other to reveal the most superior concept with respect to plant efficiency and power. It was found that in order to increase the plant efficiency considerably, it was enough to use a single pressure with a hybrid recuperator instead of a dual pressure Rankine cycle.

Tailoring electrolyte enables high-voltage Ni-rich NCM cathode against aggressive cathode chemistries for Li-ion batteries

The LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(Ni-rich NCM)cathode materials suffer from electrochemical performance degradation upon cycling due to detrimental cathode interface reactions and irreversible surface phase transition when operating at a high voltage(≥4.5 V).Herein,a traditional carbonate electrolyte with lithium difluoro(oxalato)borate(Li DFOB)and tris(trimethylsilyl)phosphate(TMSP)as dual additives that can preferentially oxidize and decompose to form a stable F,B and Si-rich cathode-electrolyte interphase(CEI)that effectively inhibits continual electrolyte decomposition,transition metal dissolves,surface phase transition and gas generation.In addition,TMSP also removes trace H_(2)O/HF in the electrolyte to increase the electrolyte stability.Owing to the synergistic effect of Li DFOB and TMSP,the Li/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) half cells exhibit the capacity retention 76.3%after 500 cycles at a super high voltage of 4.7 V,the graphite/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)full cells exhibit high capacity retention of 82.8%after 500 cycles at 4.5 V,and Li/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)pouch cells exhibit high capacity retention 94%after 200 cycles at 4.5 V.This work is expected to provide an effective electrolyte optimizing strategy compatible with high energy density lithium-ion battery manufacturing systems.

Theoretical analysis of the harmonic characteristics of modular multilevel converters

To understand the operation principle of the modular multilevel converter(MMC)deeply,it is necessary to study the harmonic characteristics of the MMC theoretically.Besides,the analytical harmonic formulas of the MMC are useful in designing the main circuit,reducing the losses and improving the waveform quality.Based on the average switching function and the Fourier series harmonic analysis,this paper deduces the analytical expressions for such electrical quantities as the arm voltage,the arm current,the capacitor voltage,the capacitor current and the circulating current of the MMC.Finally,a digital model of a 21-level MMC-HVDC system is realized in PSCAD/EMTDC.The results of the analytical expressions coincide with the simulation results,which verify the effectiveness and feasibility of the proposed analytical expressions.

Analyzing trap generation in silicon-nanocrystal memory devices using capacitance and current measurement

The combination of capacitance- and current-voltage （CV/IV） measurements is used to analyze trap generation in sili- con-nanocrystal memory devices during Fowler-Nordheim （FN） programming/erasing cycling. CV and IV curves are meas- ured after certain P/E cycles. The flatband voltage （Vro） and the threshold voltage （VtQ are extracted from CV curves by solv- ing one-dimensional Schrtidinger and Poisson equations. Both hole and electron trappings are observed in the tunneling SiO2. They show up in the accumulation and the inversion, respectively. By fitting FN tunneling current, the area densities of cy- cling-induced electron traps in the blocking oxide and in the tunneling oxide are finally determined.

The way to improve the energy density of supercapacitors:Progress and perspective

Compared with other energy storage devices, supercapacitors have superior qualities,including a long cycling life,fast charge/discharge processes,and a high safety rating.The practical use of supercapacitor devices is hindered by their low energy density.Here,we briefly review the factors that influence the energy density of supercapacitors.Furthermore,possible pathways for enhancing the energy density via improving capacitance and working voltage are discussed. In particular,we offer our perspective on the most exciting developments regarding high-energy-density supercapacitors, with an emphasis on future trends.We conclude by discussing the various types of supercapacitors and highlight crucial tasks for achieving a high energy density.

Synthesis and electrochemical performance of Sn-doped LiNi_(0.5)Mn_(1.5)O_4 cathode material for high-voltage lithium-ion batteries

ABSTRACT LiNi0.5Mn1.5-xSnxO4 （0≤x≤ 0.1） cathode materials with uniform and fine particle sizes were successfully synthesized by a two-step calcination of solid-state reaction method. As the cathode materials for lithium ion batteries, the LiNi0.5Mn1.48Sn0.0204 shows the highest specific capacity and cycle stability. In the potential range of 3.5-4.9 V at room temperature, LiNi0.5MnL4sSn0.0204 composite material shows a discharge capacity of more than 117 mA h g-1 at 0.1 C, while the corresponding discharge capacity of undoped LiNi0.5Mn1.5O4 is only 101 mA h g-1. Moreover, in cycle performance, all the LiNi0.5Mnl.5-xSnxO4 （0 ≤ x≤ 0.1） samples show better capacity retention than the undoped LiNio.sMnx.sO4 at 1 C rate after 100 cycles. Especially, for the LiNi0.5Mn1.5O4, the discharge capacity after 100 cycles is 90 mA h g-1, while the corresponding discharge capacities of the undoped LiNi0.5Mn1.5O4 is only 56.1 mA h g-1. The significantly enhanced DLi＋ and the enlarged electronic conductivity make the Sn-doped spinel LiNi0.5Mn1.504 material present even more excellent electrochemical performances. These results reveal that Sn-doping is an effective way to improve electrochemical performances of LiNi0.5Mn1.5O4.

A high potential biphenol derivative cathode: toward a highly stable air-insensitive aqueous organic flow battery

Aqueous organic flow batteries have attracted dramatic attention for stationary energy storage due to their resource sustainability and low cost. However, the current reported systems can normally be operated stably under a nitrogen or argon atmosphere due to their poor stability. Herein a stable airinsensitive biphenol derivative cathode, 3,30,5,50-tetramethylaminemethylene-4,40-biphenol(TABP), with high solubility(>1.5 mol L^(-1)) and redox potential(0.91 V vs. SHE) is designed and synthesized by a scalable one-step method. Paring with silicotungstic acid(SWO), an SWO/TABP flow battery shows a stable performance of zero capacity decay over 900 cycles under the air atmosphere. Further, an SWO/TABP flow battery manifests a high rate performance with an energy efficiency of 85% at a current density of60 m A cm^(-2) and a very high volumetric capacity of more than 47 Ah L^(-1). This work provides a new and practical option for next-generation practical large-scale energy storage.