Electrical treeing behaviors in silicone rubber under an impulse voltage considering high temperature

In this paper,work was conducted to reveal electrical tree behaviors（initiation and propagation）of silicone rubber（SIR） under an impulse voltage with high temperature.Impulse frequencies ranging from 10 Hz to 1 k Hz were applied and the temperature was controlled between 30 °C and 90 °C.Experimental results show that tree initiation voltage decreases with increasing pulse frequency,and the descending amplitude is different in different frequency bands.As the pulse frequency increases,more frequent partial discharges occur in the channel,increasing the tree growth rate and the final shape intensity.As for temperature,the initiation voltage decreases and the tree shape becomes denser as the temperature gets higher.Based on differential scanning calorimetry results,we believe that partial segment relaxation of SIR at high temperature leads to a decrease in the initiation voltage.However,the tree growth rate decreases with increasing temperature.Carbonization deposition in the channel under high temperature was observed under microscope and proven by Raman analysis.Different tree growth models considering tree channel characteristics are proposed.It is believed that increasing the conductivity in the tree channel restrains the partial discharge,holding back the tree growth at high temperature.

A method to deliver patterned electrical impulses to Schwann cells cultured on an artificial axon

Information from the brain travels back and forth along peripheral nerves in the form of electrical impulses generated by neurons and these impulses have repetitive patterns. Schwann cells in peripheral nerves receive molecular signals from axons to coordinate the process of myelination. There is evidence, however,that non-molecular signals play an important role in myelination in the form of patterned electrical impulses generated by neuronal activity. The role of patterned electrical impulses has been investigated in the literature using co-cultures of neurons and myelinating cells. The co-culturing method, however, prevents the uncoupling of the direct effect of patterned electrical impulses on myelinating cells from the indirect effect mediated by neurons. To uncouple these effects and focus on the direct response of Schwann cells,we developed an in vitro model where an electroconductive carbon fiber acts as an artificial axon. The fiber provides only the biophysical characteristics of an axon but does not contribute any molecular signaling.In our "suspended wire model", the carbon fiber is suspended in a liquid media supported by a 3D printed scaffold. Patterned electrical impulses are generated by an Arduino 101 microcontroller. In this study, we describe the technology needed to set-up and eventually replicate this model. We also report on our initial in vitro tests where we were able to document the adherence and ensheath of human Schwann cells to the carbon fiber in the presence of patterned electrical impulses(hSCs were purchased from ScienCell Research Laboratories, Carlsbad, CA, USA; ScienCell fulfills the ethic requirements, including donor's consent). This technology will likely make feasible to investigate the response of Schwann cells to patterned electrical impulses in the future.

Electrical Aging Phenomena of Power Cables Aged by Switching Impulses

Due to the insufficient information regarding the aging phenomenon of cables caused by switching impulses, we aged 15 kV XLPE and EPR cable samples by 10 000 switching impulses in experiments and tested them. Plus in order to compare the aging phenome- non under multi-stress conditions, additional EPR cable samples were aged by rated AC voltage and current with switching impulses superimposed. We used measurements of partial discharge parameters to monitor the cables’ conditions during their aging process, and the AC breakdown voltages measurement to evaluate the cables after aging. Moreover, the Fourier transform infrared (FTIR) spectroscopy measurements revealed the changes of insulation materials after aging. The measurement results confirm that the accelerated aging of cable samples had taken place. The impacts of each individual aging factor are shown through the selected measurements and comparison. The study also helps to assess the reliability of the XLPE and EPR cables under similar condition while serving in power systems.

Analysis of impulse electric field effect on organic exhaust gas decomposition

The technique of organic exhaust gas decomposition with impulse corono dischrge plasma has been investigated in this study. It has been discovered that the impulse electric field affected the decomposition efficiency with the secondary electron emission coefficient (δ) of the corona electrode as an intermediary: when the impulse voltage power ( W ) was fixed the corona electrode material with higher δ could induce higher decomposition efficiency. In these experiments, wolfram electrode which has the highest δ has really induced the highest decomposition efficiency.

Effect of electrical stimulation on neural regeneration via the p38-RhoA and ERK1/2-Bcl-2 pathways in spinal cord-injured rats

Although electrical stimulation is therapeutically applied for neural regeneration in patients, it remains unclear how electrical stimulation exerts its effects at the molecular level on spinal cord injury （SCI）. To identify the signaling pathway involved in electrical stimulation improving the function of injured spinal cord, 21 female Sprague-Dawley rats were randomly assigned to three groups： control （no surgical intervention, n = 6）, SCI （SCI only, n = 5）, and electrical simulation （ES; SCI induction followed by ES treatment, n = 10）. A complete spinal cord transection was performed at the 10^th thoracic level. Electrical stimulation of the injured spinal cord region was applied for 4 hours per day for 7 days. On days 2 and 7 post SCI, the Touch-Test Sensory Evaluators and the Basso-Beattie-Bresnahan locomotor scale were used to evaluate rat sensory and motor function. Somatosensory-evoked potentials of the tibial nerve of a hind paw of the rat were measured to evaluate the electrophysiological function of injured spinal cord. Western blot analysis was performed to measure p38-RhoA and ERK1/2-Bcl-2 pathways related protein levels in the injured spinal cord. Rat sensory and motor functions were similar between SCI and ES groups. Com- pared with the SCI group, in the ES group, the latencies of the somatosensory-evoked potential of the tibial nerve of rats were significantly shortened, the amplitudes were significantly increased, RhoA protein level was significantly decreased, protein gene product 9.5 expression, ERK1/2, p38, and Bcl-2 protein levels in the spinal cord were significantly increased. These data suggest that ES can promote the recovery of electrophysiological function of the injured spinal cord through regulating p38-RhoA and ERK1/2-Bcl-2 pathway-related protein levels in the injured spinal cord.

Movement Patterns of Metallic Particles in a Single Phase Gas Insulated Busduct with Superimposed Lightning and Switching Impulses

Transient over voltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus,like circuit breakers,transformers,insulators etc.Therefore it is necessary for the GIS also to withstand such voltages without breakdown of Insulation.The system has to be tested under these conditions.Usually the GIS system operates on power frequency.Lightning Impulse Voltage of 1050 kV and Switching Impulse Voltage of 750 kV superimposed on Power frequency voltages of 75 kV,100 kV and 132 kV are applied to Single Phase Gas Insulated Busduct and the maximum movement of Aluminum,Copper and Silver particles is determined.The movement patterns are also determined with and without Monte Carlo Simulation for movement of particle in axial and radial directions.The results show that there is a sudden jump in the movement at the application of impulse on sine wave.This is because of high magnitude voltage of 1050 kV during 1.2/50 μs.Similar movement patterns of reduced maximum movement is observed for Switching Impulse superimposed on sine wave.The results are presented and analyzed.

Dynamic correlative effect between urbanization and electricity consumption

Energy especially for rapid electricity consumption increasing is an obvious problem during the process of urbanization and economic growth. It is also an important research field to explore intrinsic regular pattern of electricity consumption and provide solving approaches. Firstly, this paper studies the relationship between electricity consumption and urbanization via GMM model by stages and regions. The results show that the most obvious stage of urbanization on electricity consumption is the stage between 1992-2000. The residents' income has an evident infl uence on electricity consumption of east region and industry also has generated stronger driving force in central and west regions. Then the paper analyzes the relationship between urbanization and electricity consumption by impulse function and gray correlation, and the variables of urbanization and industrialization both have various positive impulse effect. Estimating the gray correlation, central provinces with high population density and large shares of industry have high correlation degree in urbanization and electricity consumption.

Proper Understanding of the Nerve Impulses and the Action Potential

Neurologists define the transmission of nerve impulses across the membranes of the neural cells as a result of difference in the concentration of ions while they measured an electric potential, called as an action potential, which allows the propagation of such nerve impulses as electrical signals. Such measurements should guide them to a logical explanation of the nerve impulses as electric charges driven by the measured action potential. However, such logical conclusion, or explanation, is ignored due to a wrong definition of the flow of electric charges as a flow of electrons that cannot pass through neural networks. According to recent studies, electric charges are properly defined as electromagnetic (EM) waves whose energy is expressed as the product of its propagating electric potential times their entropy flow which is adhered to the flow of such energy. Such definition matches the logical conclusion of the nerve impulses as electric charges, as previously explained, and defines the entropy of the neural network, measured by Ammeters, in Watt or Joule/Volt. The measured entropy represents a neurodiagnostic property of the neural networks that measures its capacity to allow the flow of energy per unit action potential. Theoretical verification of the innovative definition of nerve impulses is presented by following an advanced entropy approach. A proper review of the machine records of the stimulating electric charges, used in the diagnosis of the neural networks, and the stimulated nerve impulses or stimulated responses, represents practical verifications of the innovative definitions of the electric charges and the nerve impulses. Comparing the functioning of the thermoelectric generators and the brain neurons, such neurons are defined as thermoelectric generators of the electric nerve impulses and their propagating, or action, potential.

New “Intellectual Networks” (Smart Grid) for Detecting Electrical Equipment Faults, Defects and Weaknesses

The most important elements of “intellectual networks” (Smart Grid) are the systems of monitoring the parameters of electrical equipment. Information-measuring systems (IMS), which described in this paper, were proposed to use together with rapid digital protection against short-circuit regimes in transformer windings. This paper presents an application’s experience of LVI-testing, some results of the use of Frequency Response Analysis (FRA) to check the condition of transformer windings and infra-red control results of electrical equipment. The LVI method and short-circuit inductive reactance measurements are sensitive for detecting such faults as radial, axial winding deformations, a twisting of low-voltage or regulating winding, a losing of winding’s pressing and others.

Comparison of Rehabilitation Outcomes with Acoustic Radiation Force (ARFI) Elastosonography in Hemiplegic Patients Treated with Neuromuscular Electrical Stimulation

To evaluate the gastrocnemius/soleus and biceps brachii muscle stiffness by Acoustic Radiation Force Impulse (ARFI) elastography in the hemiplegia patients, sixty patients with hemiplegia after stroke were recruited. Baseline data were collected including age, gender, body mass index, education level, dominant side, affected side, time since stroke, stroke etiology. All patients were evaluated with before treatment and posttreatment with Broonstroom staging, Modified Ashworth spasticity scale, and Functional Independence Measures scale. The patient was divided into 3 groups: 1) Neuromuscular electrical stimulation group, 2) Rehabilitation group, 3) Neurumusculer electrical stimulation + Rehabilitation group. Affected and unaffected side biceps and gastrocnemius, ARFI elastography measurements were used to measure thickness and elastic values. In addition, before and after treatment, length and thickness were measured from all patients. Of the 60 subjects, 28 were female (46.7%) and 32 (53.3%) were males, with an average age of 58.42 ± 9.03 years. There was a significant difference between the upper and lower limbs after the treatment in terms of Brunstroom staging. In terms of Modified Ashworth scale, there was a significant difference in lower extremity only after treatment. When compared to the affected/unaffected side, before and after treatment, there was a significant difference in the measurements in both the medial gastrocnemius and the lateral gastrocnemius in all three groups. Further research with larger numbers of patients for longer periods is needed to clarify the relationship between the muscle hardness and degree of spasticity.

Time Domain Modeling of Powerline Impulsive Noise at Its Source

Noise characteristics of an indoor power line network strongly influence the link capability to achieve high data rates. The appliances shared with PLC modems in the same powerline network generate different types of noises, among them the impulsive noises are the main source of interference resulting in signal distortions and bit errors during data transmission. With regard to impulsive noise many models were proposed in the literature and shared the same impulsive noise definition: “unpredictable noises measured in the receiver side”. Authors are, consequently, confronted to model thousands of impulsive noises whose plurality would very likely come from the diversity of paths that the original impulsive noise took. In this paper, an innovative modelling approach is applied to impulsive noises which are studied here directly at their sources. Noise at receiver would be simply the noise model at source convolved by powerline channel block. In the new analytical model, the impulsive noise at source is described by a succession of short pulses, each modeled by a phase-shifted Gaussian. Noises at source are classified into 6 different classes [1], and a noise generator is established for each class.

The effects of microfilament and microtubule inhibitors and periodic electrical impulses on phloem transport in pea seedling

In phloem transport, whether protoplasmic activity participates in assisting sap flow in sieve element_companion cell complex has long been in debate. The present investigation assumed microfilament (MF) and microtubule (MT), the two constituents of the protoplasmic cytoskeleton, as motive force, and employed germinating pea seedling suspended in moist chamber as experimental material: the seed being the source; the elongating root, the sink. 14 C_labeled sucrose was added to the seed as indicator. The amount of sap transported from source to sink was measured by the increase in root elongation. The transport phloem was within the cylinder of the peeled root in the middle. The exposed cylinder was treated with MF inhibitor (cytochalasin B), or microtubule inhibitor (amiphos_methyl). Results showed that the sap influx into the elongating root, and the 14 C activity as well, was reduced by about one half in treatment with cytochalasin B, and much less by amiphos_methyl treatment. Similar effect was shown in electrical impulse treatment, which seems to disrupt the MF and MT configuration.

布仑口水电站冲击式机组柔性电制动技术应用

为保证布仑口水电站机组停机过程中轴承油膜不被破坏,确保机组瓦温运行在安全范围内,解决制动停机问题,文章以新疆布仑口水电站为背景,介绍了冲击式机组柔性电制动技术的工程应用,重点介绍了布仑口电站冲击式机组停机方式、柔性电制动停机原理、电制动主回路接线形式、电制动流程、电制动系统主要设备参数,并对柔性电制动技术的基本思路和工程实现进行探讨。

干燥空气绝缘开关柜中应用的固封极柱绝缘结构设计及优化

为了实现气体绝缘开关柜的绝缘介质由SF6向干燥空气等环保型气体转变,开发一种结构小型化、绝缘水平满足要求的干燥空气绝缘开关柜中使用的固封极柱是亟需解决的问题。文中分析了40.5 kV SF6固封极柱置于干燥空气绝缘开关柜中的相间及对地电场分布,结果显示灭弧室动、静端盖板以及绝缘拉杆附近的气—固沿面电场严重超标,易造成沿面闪络。依据气—固复合绝缘理论,采取增加均压屏蔽网、改进绝缘壳体外观结构、重新设计绝缘拉杆等措施进行电场优化。通过仿真分析,优化设计后的固封极柱灭弧室端盖附近沿面最大场强由3.4 kV/mm降至2.03 kV/mm,绝缘拉杆沿面最大场强由4.1 kV/mm降至1.7 kV/mm。对优化前后的固封极柱进行了局部放电和雷电冲击耐压试验,局部放电试验的起弧电压由35 kV提升到62 kV,雷电冲击耐压试验的峰值耐受电压由145 kV提升到218 kV,证明了优化方案的可行性,为后续40.5 kV及更高电压等级的类似固封极柱的研发及优化提供了有关参考。

脉冲电流下对AL6061合金进行熔孔止裂与愈合的仿真研究

Al6061铝合金常应用于航空航天领域蒙皮制造,因其中等硬度与低强度的弱点,在承受复杂载荷时容易出现微裂纹,进而影响服役安全可靠性。脉冲电流是一种极速、非平衡的金属材料微小裂纹修复工艺,可以克服该材料不易焊接修复的短板。在既有的实验基础上建立单边预制裂纹缺口模型,采用有限元仿真手段,进行了热-电-力三场耦合数值模拟,计算不同参数下裂纹区域的电场、温度场和应力场分布。使用“生死单元”法模拟止裂熔孔的产生,并获得了不同几何、物理参数下止裂熔孔尺寸变化的规律。结果表明:焦耳热形成的止裂熔孔降低裂尖的集中应力,抑制裂纹扩展,裂纹区域高温区与基体常温区形成温度梯度相互约束产生巨大的热压应力促使裂纹宽度减小,进而直至愈合;初始熔孔尺寸与裂纹长度成正比、与板厚成反比,最佳尺寸直径为0.1 mm以内;电流值和电流加载时间均能控制熔孔生长,电流值一定时,当时间达到0.12 s形成的熔孔尺寸超出最佳止裂尺寸范围。研究成果为特定金属材料的裂纹止裂与愈合提供了机理参考和仿真方法。

空间超高比冲推进技术综述

比冲是衡量空间推进系统效率的核心指标,持续提高比冲是空间推进技术发展的永恒追求,以木星以远行星际探测为代表的复杂宇航任务对空间推进系统提出达到超高比冲的要求。系统梳理了超高比冲空间推进的主流技术路线,从静电加速机制、电磁场加速机制、新型推进剂加速机制以及新能源加速机制等方面阐述了实现超高比冲的技术途径,分析了提升比冲的关键技术,给出了超高比冲技术发展建议,展望了超高比冲技术的应用前景,为超高比冲技术突破提供参考。

交流GIS用支柱绝缘子绝缘结构优化设计

支柱绝缘子作为气体绝缘金属封闭开关设备(GIS)中重要的支撑部件,其绝缘性能影响着GIS的可靠性和稳定性。本文以工程GIS用支柱绝缘子为研究对象,选取绝缘子表面切向电场强度作为绝缘性能指标,分析了绝缘子伞裙的数量、起始位置、根部半径、顶部半径参数以及收缩伞裙结构对绝缘性能的影响。结果表明:通过增设伞裙,绝缘子切向电场分布呈现波峰、波谷震荡,有利于阻碍绝缘子沿面放电的发展。最大切向电场强度随伞裙数增加而增大,随伞裙起始位置距高压电极距离增大而减小,其位置随伞裙根部半径变化发生转移。优化结构与原始结构相比,其沿面最大切向电场强度由12.66kV/mm下降至9.69kV/mm,降幅为23.5%,通过负极性雷电冲击考核及裕度试验,绝缘裕度高达1.3倍以上。

基于多频率加权叠加的冲击电压刻度因数评估方法

冲击高压信号为幅值高、持续时间短、频率覆盖范围宽的单次脉冲波形,电压转换装置受分布参数的影响,其刻度因数难以直接溯源至现有的国家基准或标准量值。提出一种基于多频率分量加权叠加的冲击电压刻度因数评估方法。根据帕萨瓦尔定理,针对冲击电压转换装置,建立冲击刻度因数与多频率交流刻度因数之间的函数关系,将暂态的、单次的波形刻度因数溯源难题转化为稳态的、周期的交流刻度因数获取与频段权重计算的问题,通过分析该评估方法的计算误差优于0.05%。最后提出了基于该评估方法的实施方法,开展了基于标准电容分压器的计算验证,其扩展不确定度优于0.02%。结果表明,基于多频率分量加权叠加的冲击电压刻度因数评估方法能够准确评估冲击电压转换装置的冲击刻度因数并具有电学计量手段上的可行性和可操作性。

交流GIS用紧凑型盆式绝缘子沿面绝缘特性研究

盆式绝缘子作为气体绝缘金属封闭开关设备(GIS)中核心元件,在保证绝缘强度前提下,为了减小设备体积,减少SF6气体使用量,文中以工程实际GIS用盆式绝缘子为研究对象,基于沿面电场优化开展了紧凑型盆式绝缘子方案设计,重点研究了盆子中心导体处倾斜角度、高压屏蔽电极根部到盆子中心导体距离及盆式绝缘子侧壁角度对切向场强的影响。仿真结果表明,紧凑型盆式绝缘子凹、凸侧面切向场强呈现单双峰结构变化,凸侧面最大切向场强大幅上升,整体最大切向场强降低5.5%;中心导体处倾斜角度为6°~8°时,凹面侧最大切向场强取得极小值。通过对文中设计的紧凑型盆式绝缘子进行负极性雷电冲击考核及裕度试验,绝缘裕度不减反增,高达1.35倍,为紧凑型盆式绝缘子的工程推广提供参考。

66kV干式变压器雷电冲击试验故障分析

本文中作者针对研发的一台66kV等级干式变压器雷电冲击试验过程出现的故障进行了研究,通过有限元仿真方法复现了试验故障原因,并通过仿真数据优化设计方案后,使得产品顺利通过了试验验证,证明了仿真分析的有效性及准确性。