Characteristics of Bi-2223 HTS Tapes Under Short-Circuit Current Impacts in Hybrid Energy Transmission Pipelines

A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current Ic ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.

Practice and Thinking on Current Planning Environmental Impact Assessment of Transmission and Transformation Power Grid in Jiangsu Province

The planning environmental impact assessment （EIA） of transmission and transformation power grid at levels of 500 and 220 kV had been finished completely in the 13 municipalities of Jiangsu Province by the end of 2012, which played important roles in guiding and planning the following transmission and transformation projects in environmental protection. In this paper, through the detail analysis on the objective and significance of the planning EIA of transmission and transformation power grid, legal basis and planning EIA practices, some suggestions and thinking about the planning EIA of transmission and transformation power grid were put forward.

Calculation of Eddy Current Loss and Short-circuit Force in SSZ11-50000/110 Power Transformer

The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.

Impact of surgery on the outcome after spinal cord injury – current concepts and an outlook into the future

Traumatic spinal cord injury（SCI）remains a devastating neurological disorder leading to severe consequences for the affected individual and their families.Further,socioeconomic implications should not be neglected as well.Although life expectancy after SCI increased tremendously,therapeutic treatment options remain limited.

高影响慢性疼痛的研究进展

对高影响慢性疼痛的现状、评估工具、影响因素及干预方面进行综述,旨在引起医务人员及研究者对高影响慢性疼痛的重视,为制订有效降低高影响慢性疼痛的干预方案提供参考。

电阻型直流故障限流器的冲击特性研究

直流故障限流器能够快速限制故障电流上升,但需要关注其在故障冲击过程中的限流动态特性。为此,开展电阻型限流器的故障冲击特性研究。首先,理论分析并推导限流器串入前后系统直流电压、限流器耐受冲击电流的数学表达式。然后,搭建直流大电流冲击平台,研发限流器实验室样机;在MATLAB/Simulink仿真平台中搭建限流器模型并开展冲击特性仿真分析。最后,分别对单线圈和多线圈并联结构的电阻型限流器进行大电流冲击测试。仿真与实验结果表明:故障冲击越大,限流器失超后电阻上升越快且幅值越大,限流效果越好;在冲击电压较低时,限流电阻会呈现先迅速上升然后下降的趋势。

冲击载荷下电涡流阻尼器磁场研究

为研究冲击载荷下电涡流阻尼器的磁场特性,建立了永磁式电涡流阻尼器模型和等效磁路模型,分析了空气间隙处磁场强度与结构参数之间关系;利用有限元法对冲击载荷下电涡流阻尼器的静、动态磁场以及涡流场特性展开研究。研究发现:电涡流阻尼器静态磁场呈“几”字形,阵列式分布,冲击载荷下次级筒产生的电涡流将会与静态磁场相互作用形成一个时刻变化的“几”字形动态工作磁场,且变化情况与阻尼器受到的冲击载荷有一定关系,本文研究结果对提高冲击载荷下电涡流阻尼力控制具有一定的参考价值。

大容量冲击短路试验发电机组继电保护方案

随着实验室容量不断提高,大容量冲击短路试验发电机组应用日益增加,其继电保护配置对机组与电网安全十分重要。以冲击短路试验发电机组继电保护为研究对象,描述了冲击短路试验发电机的主要故障类型,介绍了故障的继电保护原理,对比了电磁式电流互感器和全光纤电流互感器特点。同时以额定容量100 MVA冲击短路试验发电机为例,设计了适用于冲击短路试验发电机的继电保护方案,并详细分析了发电机差动保护、定子过负荷保护、转子接地保护参数整定方式,可为冲击短路发电机组继电保护配置提供参考。

Simulation Study of Potential Impacts of Tidal Farm in the Eastern Waters of Chengshan Cape, China

The sea area east of Chenshan Cape has peak tidal current flows that exceed 2.3 m s^-1,which make it a promising site for the development of tidal current energy.Before these resources can be exploited,a comprehensive assessment is needed of the potential environmental impacts of the extraction of this energy.In this paper,we describe our construction of a three-dimensional hydrodynamic model of the waters near Chengshan Cape,and verify the performance of the model using continuous data measured in situ.We modeled the potential impacts of the exploitation of these resources on the flow field by adding a momentum loss term in the governing equation of the model.Simulation results show that an assumed tidal farm with an estimated power output of 20.34 MW would have a significant impact on the surrounding water level,especially next to the farm,where fluctuation could reach 6 cm.The maximum drop in the flow velocity in the wake of the farm was predicted to be more than 0.8 m s^-1,and this influence would extend 10 km downstream.

Placement optimization of Multi-Type fault current limiters based on genetic algorithm

The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial applications.In this study,two objectives with the same dimensional measurement unit,namely,the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents,are considered.The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life.The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem.The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm(GA)method.Comparative and sensitivity analyses are performed.The results of the optimized plan are validated through simulations,indicating the significant potential of the GA for such optimization.

Research on Numerical Simulation of 3D Leakage Magnetic Field and Short-circuit Impedance of Axial Dual-low-voltage Split-winding Transformer

It is difficult to accurately calculate the short-circuit impedance, due to the complexity of axial dual-low-voltage split-winding transformer winding structure. In this paper, firstly, the leakage magnetic field and short-circuit impedance model of axial dual-low-voltage split-winding transformer is established, and then the 2D and 3D leakage magnetic field are analyzed. Secondly, the short-circuit impedance and split parallel branch current distribution in different working conditions are calculated, which is based on field-circuit coupled method. At last, effectiveness and feasibility of the proposed model is verified by comparison between experiment, analysis and simulation. The results showed that the 3D analysis method is a better approach to calculate the short-circuit impedance, since its analytical value is more closer to the experimental value compared with the 2D analysis results, the finite element method calculation error is less than 2%, while the leakage flux method maximum error is 7.2%.

矿用刮板输送机垂直冲击下负载电流特性研究

矿用刮板输送机在运行过程中易受液压支架推移不齐、采煤机截割底板不平的影响,承受着多种类型冲击,其中垂直方向的冲击作用最为明显,造成刮板输送机传动系统磨损严重、驱动电机功率不平衡等问题。笔者通过分析刮板输送机垂直冲击的形成原因,计算了不同垂直冲击作用下刮板输送机的运行阻力,建立了刮板输送机传动系统的垂直冲击仿真模型,并对刮板输送机在中部槽间隙、中部槽凸起弯曲、中部槽凹陷弯曲等工况下的冲击负载电流情况进行了仿真分析,结果表明:中部槽间隙越大,中部槽与中板发生的撞击就会越强烈,对刮板输送机传动系统的冲击越明显;垂直冲击产生的负载电流峰值与中部槽凹陷或凸起弯曲程度呈正相关;相邻中部槽最大弯曲角是决定刮板输送机冲击负载电流突变峰值及冲击稳定后负载增量的主要因素;中部槽凸起和凹陷弯曲产生的冲击对系统运行阻力的影响程度最大约为12%,是影响驱动系统电机功率不平衡的主要因素。在煤矿井下搭建了刮板输送机冲击负载监测平台,开展了不同垂直弯曲角度下的冲击负载电流监测试验,结果表明:不同程度的垂直冲击均使刮板输送机传动系统电机负载电流产生明显波动,且在短时间内,冲击电流峰值最高可达正常工作电流的1.5倍,对刮板输送机的链条、电机等零部件造成严重损害;现场采集的刮板输送机受到冲击后的电机电流曲线与仿真曲线变化趋势基本保持一致,平均绝对误差范围为0.435~1.342 A,验证了刮板输送机垂直冲击仿真模型的正确性与合理性。研究成果为提升刮板输送机的智能控制水平、保障煤矿运输装备的负载稳定和功率平衡提供了理论依据,进而降低综采工作面的运输成本,延长运输装备的使用寿命。

柔性电缆PCB内电层载流量研究与实验验证

对某微小型飞行器内部柔性电缆PCB的稳态载流能力和冲击电流载流能力进行了理论计算和设计。通过MIL-STD-275标准和经验公式,对柔性电缆PCB的稳态载流能力进行了复核复算;通过对照GJB4057—2000,估算出柔性电缆PCB的冲击电流载流能力。对于理论计算和估算值,设计了2倍理论值状态下的稳态载流测试和10倍理论值状态下的脉冲电流测试实验,实验结果与预期一致,验证了设计理论计算的正确性。在载流实验中,获取柔性PCB板在各个电流值载流状态下的温度情况,并通过Flotherm软件进行热仿真验证,模拟了PCB在各个电流值状态下的稳定温度,热仿真结果与实际测试结果相吻合,验证了实验数据的真实性与合理性。该载流量实验与仿真数据结果可为后续短时工作微小型飞行器内部PCB设计提供实验数据支撑。

快速陡脉冲重复电场下高频变压器绝缘介质损耗与冲击能量积聚特性

电力电子变压器中高频变压器须承受高频非正弦与高温的复杂应力。随着SiC等大功率半导体器件的使用,高频变压器中非正弦方波电压上升与下降沿出现陡脉冲应力,其dv/dt大于10 kV/μs,给高频变压器绝缘可靠性带来巨大挑战。高dv/dt包含大量高频谐波,从而导致绝缘介质损耗明显增加;高频、高dv/dt下绝缘遭受累积性冲击电应力,导致局部电场畸变,引发绝缘局部放电与损伤。该文围绕dv/dt对高频变压器绝缘介质损耗与冲击能量积聚的影响展开研究。采用阶跃响应函数模拟高dv/dt脉冲电压,结合绝缘介质损耗分解与计算,提出了dv/dt与方波电压叠加下绝缘介质损耗的计算方法。结果表明,绝缘介质损耗随dv/dt的增大而增加,绝缘热效应明显增加。根据绝缘在方波交变电场下能量储存和释放特性,分析了高dv/dt下绝缘能量积聚密度pd。采用有限元仿真分析10 kW、10 kHz、1000 V/750 V高频变压器绝缘电场、位移电流与冲击能量密度。结果发现,pd随着dv/dt增加而增大。结合介质损耗计算,研究指出在方波电压高dv/dt处(电压极性反转时),绝缘遭受累积电-热冲击应力,造成绝缘损伤。研究结果为大容量高频变压器绝缘失效与设计提供指导。

基于故障漏磁分析的变压器短路阻抗特性研究

变压器绕组在受到短路冲击下,会出现明显的漏磁情况。通过软件仿真与实验验证的方法,对不同情况下绕组主空道处的漏磁情况进行分析,分别考虑轴向漏磁与径向漏磁下的磁场分布规律,总结变压器受到短路电流冲击的影响;对形变情况下的绕组进行分析,讨论其磁场分布情况与受力情况,对其抗短路能力进行探讨,结果证明形变后的绕组在两端位置更容易受到短路电流的冲击,需要利用相应措施加以防护,以保证电力系统运行的稳定。

基于改进转子端环参数计算的深槽笼型异步电动机启动特性仿真分析

为了更为准确分析深槽笼型异步电动机的启动性能,本文在考虑铁芯饱和、导条涡流、绕组端部电阻和电感的基础上,进一步考虑了转子铁芯、转子压圈及平衡环对转子端环电抗参数的影响,以及转子导条伸出铁芯部分对转子端环电阻参数的影响。建立了750kW深槽笼型异步电动机场-路-运动耦合时步有限元模型,对其启动特性进行了全面的仿真分析,分析了电动机在启动过程中电磁场、转子导条涡流的变化情况,计算了电机在启动瞬间的冲击电流和冲击转矩,并将仿真结果与试验值进行对比分析。结果表明:采用本文所提出的基于改进转子端环参数的计算方法和场-路-运动耦合时步有限元模型,得到的深槽笼型异步电动机启动特性的计算结果具有更高的仿真精度,为今后的深槽笼型异步电动机启动性能优化设计、运行维护及保护整定提供有效参考。

高速公路对自然保护区生态影响分析——以大丰华高速涉及梅州鸿图嶂自然保护区为例

通过对大丰华高速公路涉及鸿图嶂自然保护区评价区的现状调查,掌握评价区的动植物多样性和土地利用现状,在工程分析的基础上,预测项目工程建设在施工期和运营期可能对自然保护区生态环境产生的影响,进而分析确定项目建设涉及自然保护区方案的可行性,并提出生态保护与恢复措施,以最大限度降低工程建设对自然保护区的不利影响。

配电变压器大容量短路试验仿真计算研究

本研究讨论了短路电流计算、绕组短路电动力计算、配电变压器绕组稳定性分析以及配电变压器大容量短路试验冲击系数计算,并采用PSCAD软件对一台315kVA配电变压器进行了仿真计算。

10kV配电网合环电流计算方法研究

合环转供电已成为10 kV配电网转移负荷的重要方式,而合环电流的计算是合环转供电操作的必要前提。为保证合环操作的顺利进行,提出了一种10 kV配电网合环电流计算方法。首先依据戴维南定理建立了典型配电网合环系统的等效电路;然后利用叠加定理对合环稳态电流和冲击电流进行了理论分析,并考虑最大合环冲击电流出现时刻和所在相的影响,改进了现有合环冲击电流计算方法,提高了计算结果的准确性;最后通过合环仿真模型对理论分析进行仿真验证,结果表明所提计算方法具有较高的准确性,对实际合环操作具有一定的指导意义。

中国近海中尺度涡分区分类与影响初探

海洋中尺度涡作为物质循环、能量串级和信息传递的关键尺度和重要环节,具有丰富的热动力学内涵。文章基于中国近海及毗邻海域的涡动能分区,重点综述中尺度涡的运动属性、动力学本质和局地特征,从尺度局限与尺度关联的角度阐示中尺度涡旋的扰动生成、传播、能量级联和耗散,及其在海洋多尺度动力过程、热盐配置、生源要素调控和中尺度海气相互作用中的影响,并就相关科学问题和进展提出研究建议。研究结果表明:研究中尺度涡的演变规律对理解海洋物质能量传递的多维度层次、尺度规模和过程形式具有重要意义,需整体加深海洋中尺度涡自适应观测和可预报性研究,增强海洋中尺度涡的尺度演绎分析和特异性分析,建立从天气尺度到气候环境变化、生物生态影响以及致害致灾风险的能量信息通道,构建中观海洋生态系统动力学理论与模型,探索海洋中尺度涡精细化灾害风险预评估区划和安全保障新途径。