基于负荷预测的0.4 kV配网低电压风险评估方法

我国现阶段的配电网网架结构依然十分薄弱,智能化水平低,缺乏先进的检测技术和高效的运维模式。在现阶段低压电气信息不开源的情况下,为解决0.4 kV配网无差别运维效率低的问题,文章分析了适用于低压配网状态评估的评价维度,并基于负荷预测结果提出了低压台区低电压风险评估方法,引入了微增容量所引起的压降比,实现对低电压风险的定期管控。该文对于优化低压配电网运维资源配置、指导低压配网差异化运维模式的建立,以及提高低压配电网运维整治效率具有一定的参考价值。     

The control of abnormal grain growth in low-voltage SnO2 varistors by microseed addition

In this research, the addition effects of three different quantities of micron-sized seeds (microseeds) to a SnO₂ varistor prepared from nanomaterials on the microstructure and electrical properties were studied. Moreover, surge-withstanding capability of low-voltage SnO₂ varistors was investigated. The X-ray diffraction pattern disclosed a single phase SnO₂ for microseed grains. The morphological features of samples were characterized using scanning electron microscopy. The abnormal distribution of grain size with elongated grains of SnO₂ in fine grains matrix was observed in sintered samples without microseeds. The low content of microseed addition (0.3 wt%) had not controlled abnormal grain growth, however, it increased mean grain size to 37 µm. Although the high content of microseeds (7.5 wt%) stopped abnormal grain growth, it had a negative effect on relative density and mean grain size. The normal grain size distribution with maximum mean grain size (45 µm) was obtained in samples containing 1.5 wt% microseeds. These samples showed the lowest breakdown field (240 V/cm) and the highest surge-withstanding capability (1.5 kA/cm²). Furthermore, the standard deviation of the electrical parameters of these samples was improved due to normal grain-size distribution.     

Parallel Multipopulation Differential Evolutionary Particle Swarm Optimization for Voltage and Reactive Power Control

This paper presents parallel multipopulation differential evolutionary particle swarm optimization (DEEPSO) for voltage and reactive power control (VQC). The problem can be formulated as a mixed integer nonlinear optimization problem and various evolutionary computation techniques have been applied to the problem including PSO, differential evolution (DE), and DEEPSO. Since VQC is one of the online controls, speed‐up of computation is required. Moreover, there is still room for improvement in solution quality. This paper applies parallel multipopulation DEEPSO in order to speed up the calculation and improve solution quality. The proposed method is applied to IEEE 30, 57, and 118 bus systems. The results indicate that the proposed method can realize fast computation and minimize more active power losses than the conventional evolutionary computation techniques.     

Sustainable disassembly line balancing model based on triple bottom line

End of life (EOL) phase of a product is receiving more attention due to increase in environmental concerns, and many studies have been conducted for value creation in EOL, focusing on concepts as remanufacturing, reuse and recycling in sustainable production manner. This study especially focuses on one of global problem, e-waste. To minimise the amount of wastes and maximise recovered materials from EOL, disassembly is one of the most important concept, associated with reuse, and balancing disassembly line in an optimal way is essential for organisations. In disassembly line balancing (DLB), not only precedence of tasks, but also risk criteria related to environment and human safety should be considered for sustainability. The aim of this study is to propose a model based on triple bottom line (TBL) dimensions, i.e. human safety, environmental safety and business criteria. To achieve sustainability in DLB, and for risk assessment in sustainable DLB, it had been decided to use a multi-criteria method, i.e. TODIM, acronym in Portuguese of ‘Tomada de Decisão Iterativa Multicritério’. The proposed model included 22 disassembly criteria categorised under TBL dimensions, which are derived from the literature. Implementation of the study was conducted for computer disassembly processes, and as a result of the study approximately 12% an improvement in cycle time was succeeded. In the long run, the integration of sustainability in disassembly operations may contribute to the competitive advantage of the company in terms of differentiation and corporate image by achieving business, environment and human targets simultaneously.     

High performance multi-layer varistor (MLV) from doped ZnO nanopowders by water based tape casting: Rheology,sintering, microstructure and properties

In this work, we report the fabrication of a high performance multi-layer varistor (MLV) via water based tape casting method using novel compositions of nanomaterials. Bi₂O₃, CaO and Co₃O₄ doped ZnO nanopowders were prepared by solution combustion synthesis (SCS) route, calcined at different temperatures (550, 650, 750 and 850?°C) and characterized by TEM, XRD, SEM and AFM. The nanopowder (crystallite size ~30?nm) calcined at 650?°C for 1?h was used as the starting material for MLV fabrication. Compositions of the slurry containing doped ZnO nanopowders, binder and plasticizer in water solvent were optimized for the fabrication of thick film. The rheological properties of the slurries having different solid loadings were analysed and thick films of various thicknesses (50–500?µm) were prepared by varying the feeding rate of tape casting. The film roughness of 38.3?nm for the thick film made from 40?wt% solid slurry was found to be superior compared to other samples due to the presence of reduced crack and shrinkage. MLV fired at 950?°C for 1.5?h exhibited a coefficient of nonlinearity of 18 and breakdown voltage of 291.5?V that yields superior properties compared to commercial MLVs.     

融合前沿研究的液体电介质击穿教学研究

针对《高电压与绝缘技术》课程中液体电介质的教学难点，提出了融合前沿研究的液体电介质击穿教学方法。基于前沿的液体放电应用背景与先进的液体放电研究平台，形象地展示液体电介质的动态击穿过程，在教学内容、教学方法、考核方式等方面进行科教融合改进，实施“以学生为中心”理念的课程教学设计。该教学方式取得了较好的教学效果，能够为其它知识点的教学质量提升提供参考。     

Effects of temperature on creepage discharge characteristics in oil-impregnated pressboard insulation under combined AC–DC voltage

Due to the complexity of the valve side winding voltage of the converter transformer, the insulation characteristics of the oil-impregnated pressboard (OIP) of the converter transformer are different from those of the traditional AC transformer. The study on effect of temperature on the creeping discharge characteristics of OIP under combined AC–DC voltage is seriously inadequate. Therefore, this paper investigates the characteristics of OIP creepage discharge under combined AC–DC voltage and discusses the influence of temperature on creepage discharge characteristics under different temperatures from 70°C to 110 °C. The experimental results show that the partial discharge inception voltage and flashover voltage decrease with increasing temperature. The times of low amplitude discharge (LAD) decrease and amplitude of LAD increases. Simultaneously, the times of high amplitude discharge (HAD) gradually increase at each stage of creepage discharge with higher temperature. The analysis indicates that the charge carriers easily accumulate and quickly migrate directional movement along the electric field ahead of discharging. The residual charge carriers are more easily dissipated after discharging. The ‘hump’ region of LAD moves to the direction of higher discharge magnitude. The interval time between two continuous discharges is shortened obviously. The concentration of HAD accelerates the development of OIP insulation creepage discharge. The temperature had an accelerating effect on the development of discharge in the OIP under applying voltage.     

Low voltage operating organic light emitting transistors with efficient charge blocking layer

Charge injection/blocking layers play important roles in the performances of organic electronic devices. Their incorporation into organic light emitting transistors has been limitted, due to generally high operating voltages (above 60 V) of these devices. In this work, two hole blocking molecules are integrated into tris-(8-hydroxyquinoline) aluminum (Alq₃) based light emitting transistors under operating voltage as low as 5 V. The effects of hole blocking and electron injection are decoupled through the differences in the energy levels. Significantly improved optical performance is achieved with the molecule of suitable energy level for electron injection. Surprisingly, a decreased performance is observed in the case of another hole blocking molecule evidencing that charge injection overweighs charge blocking in this device architecture.     

"不知火"柑橘全自动包装生产线的设计与研究

目的为了解决柑橘在实际包装过程中因于人工手动装袋、装箱等导致的效率低下问题,设计一条全自动柑橘包装生产线。方法基于“不知火”柑橘的特殊体型特征,使用传送带分级装置对其进行分级;通过倾斜皮带解决柑橘排列姿态的整理问题;经给袋式包装机装袋后,采用扭结式扎口装置对其进行封口;利用并联机器人对其进行装箱。通过计算生产节拍,合理规划每个工序的循环时间,并通过Flexsim软件对该生产线进行仿真分析与平衡优化。结果该生产线整体效率由89%提升到93%,能够正常运行且满足生产力的需求。结论该柑橘包装生产线实现了柑橘的分级、整料、装袋、装箱等工序,降低了工作强度,提高了生产效率,实现了包装过程的自动化。     

LWD仪器临界电压数据读取分析与解决

锂电池是LWD仪器正常工作的动力来源,是仪器的心脏。仪器出井后,需要在井口读取数据,当锂电池的电量接近耗尽时,会导致数据读取失败的问题。该问题处理不当,会造成长期占用井口,影响钻井时效,严重时还可能会因短路造成昂贵的LWD仪器损坏。锂电池的临界电压问题暴露了该仪器的设计缺陷,在此通过技术方法充分利用INSITE系统本身提供的功能,绕过其设计缺陷将问题解决。