吹灰蒸汽对炉内受热面吹损的分析

对张家口发电厂8号炉低温过热器受热面大面积吹损原因进行了分析,并采取了相应的措施,避免了低温过热器大面积爆管泄漏的发生,保证了锅炉的安全运行.     

雷电损害风险评估浅析

为客观评价建筑物的雷电损害,从建筑物的年平均预计雷击次数N、雷击损坏类型和原因p、建筑物及其内部造成的损失δ等3要素的相互关系中得出雷电损害风险值Rd,将Rd与最大可接受值Ra比较来决定是否要做防雷以及采取何种措施降低雷电风险;通过从建筑物内外人员伤亡和内部设备的损失价值量化计算评估雷电的损害度,从而更科学、安全、经济、合理地采取适当防雷措施。提出了雷电损害风险评估在不同阶段中的应用。     

浅谈电动机断相运行的危害及预防

电动机在工农业生产中得到了广泛应用,其一旦产生故障则直接影响到工农业正常生产。电动机断相变成缺相运行是电动机常见故障之一。分析电动机断相原因,了解其危害,预防性地采取积极措施,确保电动机正常运行,对工农业生产和企业安全经济运行,具有重要的现实意义。 1 电动机断相造成缺相运行的现象及原因 正常运转的三相电动机发生断相造成缺相运行时,电动机转子的电流将突然增大,电动机温升会由此加剧,严重时甚至烧毁电动机。如果原来停着的三相电动机发生断相,一旦通电不但启动不起来,而且还会发出“唔唔”作响的声音。造成三相电动机缺相…     

Damage of a distribution transformer due to through-fault currents:an electrical forensics viewpoint

Insurance coverage for commercial premises includes direct loss and damage of the mechanical and electrical plant as well as consequential loss or damage. In recent years, many electrical failures have given rise to huge claims. It is, therefore, also in the interest of the electric power engineering community that the reliability of new systems being designed is acceptable and justified in the light of escalating claims for consequential loss or damage. For many existing power distribution systems in Singapore, it may require a reassessment of the need for additional features to improve the reliability. A case study is presented in this paper to illustrate this point. The case involved a failure investigation that was conducted on a distribution dry-type transformer     

Analysis of Surface Degradation of Silicone Rubber Insulation Due to Tracking Under Different Voltage Profiles

Tracking is basically a carbonaceous process. In the present study, the tracking phenomenon in silicone rubber material has been studied under AC and DC voltage. The influence of applied voltage magnitude, conductivity, and flow rate of the contaminant on tracking, were analyzed. It is observed that the tracking is more severe under DC voltages. The tracking time is less under negative DC voltage compared to the positive DC voltage. The tracking mechanism is explained in detail. The leakage current during the tracking studies was measured and its trends were analyzed by using the moving average technique. The leakage current magnitude is high with thermally aged specimens when compared to the virgin specimen, irrespective of the type of applied voltage. It is realized that the tracking time and the leakage current magnitude shows an inverse relationship. In addition, the surface condition of the insulation material was analyzed with the water aged specimen and the diffusion coefficient of the material was calculated. The reduction in contact angle of the specimen has direct impact in the reduction of its tracking time. The tensile test and DMA test results indicate that thermal aging of the specimen alter the mechanical properties of the material. The activation energy of the material was calculated through DMA studies, indicating that materials with high activation energy show an increase in tracking time of the specimen.     

Fast Wafer Level Reliability Monitoring: Quantification of Plasma-Induced Damage Detected on Productive Hardware

This paper describes the investigation of a Plasma-Induced Damage (PID) event in the metal stack of an 8-in 130-nm-high volume process line. The relevant PID stress and measurement sequence used during standard productive fast Wafer Level Reliability Monitoring, which had detected this event, is discussed, and it is shown to be very effective. Additionally, hot carrier stress was performed on MOS transistors with antenna structures connected to the gate electrode for the quantification of the effect of PID on MOS device characteristics. It is demonstrated that the complete investigation can be done on production wafers in a very short time and only on scribe line test structures, saving time and hardware cost for extra wafers.      

局部放电对油浸绝缘纸表面损伤特性研究

为了提高绝缘材料的耐局部放电能力,对局部放电损伤过程中油浸绝缘纸的表面形貌、表面粗糙度、表面电导率、表面生成物和气隙气体进行了研究.根据局部放电相位分布(phase-resolved partial discharge,PRPD)模式的变化将放电损伤过程划分为5个阶段,分别利用光学显微镜、扫面电镜、原了力显微镜和高阻仪对每一损伤阶段的绝缘表面情况进行分析,并用气质联动仪分析了其气隙气体组分.研究结果表明:在5个损伤阶段中,绝缘表面相继出现"烧蚀"、"剥皮"、"裂化分丝"、"回坑"和"树枝化"现象,且有"液滴"和品状"固体"相继生成,电负性气体含量交替下降上升;绝缘表面三维粗糙度先下降后上升:绝缘表面电导率总体呈现增长趋势并最终趋于稳定,但在不同损伤阶段其增长速率不同.提供了判断油浸绝缘纸表面状况及缺陷发展状况的参考信息.     

基于紫外成像图像信息的绝缘子表面放电量化方法

紫外成像法是一种有效的非接触式放电检测方法,为采用紫外成像法量化绝缘子的表面放电电信号强度,论文以紫外图像中放电光斑面积的大小作为紫外成像量化参量,试验对比研究了绝缘子放电的紫外成像图像和电脉冲信号特征,分析得到了观测距离为9m和紫外成像仪在几种典型增益下的光斑面积与脉冲电流的峰值、脉冲电流平均值的关系。研究了可见光通道与紫外通道的图像参数随距离增加时的变化规律,研究发现两者具有近似相同的衰减特性,在此基础上提出了采用可见光通道的信息用于估计成像区域面积的方法,避免了不同距离下检测到的结果没有对比性的问题,论文最后采用了最小二乘回归支持向量机实现了对放电强度的估计。     

乙丙橡胶表面电痕腐蚀对极化——去极化电流的影响

电痕是引起绝缘表面劣化的主要原因之一。针对矿用乙丙橡胶电缆绝缘表面电痕腐蚀问题,文中以不同电痕发展阶段的乙丙橡胶试样为研究对象,试验测量并分析了乙丙橡胶表面电痕腐蚀程度与极化—去极化电流之间的关系,提取了去极化初始电流值、电流衰减稳定值和凹点出现时间3个特征量。对比不同电痕腐蚀程度试样的极化—去极化电流曲线及其特征量发现:在去极化初始阶段,初始电流值、放电速率和去极化电流衰减稳定时刻的电流值与乙丙橡胶表面电痕损伤程度密切相关;随着测量时间的延长,去极化电流曲线上出现凹点,该凹点出现时间与表面电痕腐蚀程度相关。研究结果证明,使用极化去极化电流方法可以对乙丙橡胶的表面电痕腐蚀程度进行有效评估。     

PFC电感漆包线表面破损对产品性能的影响

漆包线表面破损是PFC电感失效的主要原因之一,但漆包线表面破损的大小及深度对电感整体性能影响不同.PFC电感受行业手工绕线加工工艺影响,过程会不可避免造成刮破漆包线的隐患,而对PFC电感进行外观全检和匝间耐压测试,能够在早期筛选出表面破损的匝间绝缘不良的电感,本文通过研究漆包线破损程度对产品性能的影响来降低行业内电感的...     

基于非奇异终端滑模控制的水面无人船轨迹跟踪

针对欠驱动水面无人船舶的有限时间轨迹跟踪,提出了非奇异终端滑模与变指数幂次趋近律结合的控制方法.利用输出重定义的方法构造无人船舶跟踪误差动态模型,引入基于跟踪误差的非奇异终端滑模,消除传统终端滑模的奇异问题,保证在有限时间跟踪并保持期望轨迹;引入变指数幂次趋近律,通过在不同阶段改变指数调节系统的趋近过程,来解决滑模在远...     

制造业跟踪系统解决方案

制造业跟踪系统解决方案, 利用其先进、成熟的网络技术和通信技术为管理者提供了有力的工具,并可以为企业的ERP系统和SCM系统提供及时、准确、详实的基础数据,使企业的管理手段和管理水平产生质的飞跃。     

高温时加有机绝缘阻燃剂的放电与电痕特性

通过测试接触角(θ)和比较漏电痕迹指数(CTI),计算放电量和放电频谱分布参数,分析了在聚碳酸酯绝缘材料中添加不同含量溴系阻燃剂和在纸基树脂绝缘材料中添加磷系阻燃剂对有机绝缘的电气绝缘性能的影响与在常温和高温环境下其电气性能的变化。结果表明,两种材料具有相同的趋势:随阻燃剂含量的增加,θ减小,放电量增加,放电能量增大,CTI值减小;随温度的升高,θ减小,放电量减小,放电能量变小,CTI值增大。也就是说,添加阻燃剂后有机绝缘的绝缘性能下降,随温度升高耐电痕性将会增强。     

采用面向对象技术和方法的电力系统网络拓扑的快速跟踪（一）

本文首先回顾了文［１］基于面向对象（ＯＯ）的电网拓扑表示,接着用面向对象的思想方法对厂站的拓扑跟踪和电网的拓扑跟踪进行了分析（ＯＯＡ）,并建立电网拓扑ＯＯ模型中的关键方法－启发式网络分区算法,该方法避免了用深度和广度搜索及矩阵计算进行网络分区计算的计算量大或占用内存多、计算时间长的缺点。     

Lightning and Power Surge Damage to Appliances

Lightning rarely damages appliances by direct stroke to the appliance. Damage is usually caused by direct strokes to the power lines or by induced surges. Induced surges are caused by the release of bound charges on the line when overhead clouds lose charge because of a strike to objects other than the line. The direct stroke produces a large voltage, while induced surges usually have a lower magnitude voltage. Lightning usually damages appliance electrical insulation which leads to a continuation of the damage by the 60-Hz power that has the appearance of a non- lightning-related failure. Lightning or power surge damage can probably be ruled out if the equipment has failed because of certain problems such as an open conductor or a bad bearing. Electric lamps can provide a clue as to whether a high-voltage surge occurred in the electrical system because the filaments often open when subjected to such surges. Equipment can be protected by a design to withstand the highest normal voltage spikes expected. Proper grounding and bonding also is important. For critical components or equipment, surge arresters may be required.     

On the Use of Low-Cost Computer Peripherals for the Assessment of Motor Dysfunction in Parkinson's Disease—Quantification of Bradykinesia Using Target Tracking Tasks

The potential of computer games peripherals to measure the motor dysfunction in Parkinson's diseases is assessed. Of particular interest is the quantification of bradykinesia. Previous studies used modified or custom haptic interfaces, here an unmodified force feedback joystick and steering wheel are used with a laptop. During testing an on screen cursor moves in response to movements of the peripheral, the user has to track a continuously moving target (pursuit tracking), or move to a predetermined target (step tracking). All tasks use movement in the horizontal axis, allowing use of joystick or steering wheel. Two pursuit tracking tasks are evaluated, pseudo random movement, and a swept frequency task. Two step tracking tasks are evaluated, movement between two or between two of five fixed targets. Thirteen patients and five controls took part on a weekly basis. Patients were assessed for bradykinesia at each session using standard clinical measures. A range of quantitative measures was developed to allow comparison between and within patients and controls using analysis of variance (ANOVA). Both peripherals are capable of discriminating between controls and patients, and between patients with different levels of bradykinesia. Recommendations for test procedures and peripherals are given.     

汽轮机轴承烧瓦与轴颈的渗巴氏合金现象

简述轴承工作性质，巴氏合金应用与相组成的基本情况。论述汽轮机转子在两个电厂长期运行后，由于轴颈发生的不正常摩擦损伤，在大修改造中由无损检查、机械加工揭示出轴颈存在严重的渗巴氏合金现象，低熔点金属Sn、Sb与Cu向转子材料晶界的深层渗入最终导致了3根大型在投转子的严重开裂与报废。图11表2     

绝缘试样的漏电痕迹劣化与环境因素的影响

目前尚无非常规环境下评估绝缘材料漏电痕迹劣化的国际标准,故按IEC60112和IEC60587国际标准论述了不同种类绝缘试样在紫外线照射、低气压、γ射线辐射、酸雨及高温环境下的漏电痕迹劣化特征,即紫外线照 射可改变环氧树脂的绝缘破坏时间;在低气压环境下聚碳酸酯的CTI值增大,聚对苯二甲酸乙二醇酯的CTI值减小;随着γ射线照射量的增加聚萘二酸丁醇酯的CTI值增大,聚对苯二甲酸丁二醇酯的CTI值减小;聚碳酸酯随着温度的升高CTI值增大;聚苯乙烯在酸雨环境下绝缘强度无明显变化。在非常规环境下,如果用CTI值变小的绝缘材料将导致电器设备绝缘过早击穿而引起电气事故。     

几种降低雷电危害计算机网络的技术

针对雷电对计算机网络的危害,分析雷电侵入计算机网络的主要途径;以实例介绍降低雷电危害计算机网络的技术.     

Optical Damage Limits to Pulse Energy From Fibers

The irradiances or fluences encountered in pulsed fiber lasers and amplifiers are sometimes high enough to destroy the fiber. The ultimate limit is set by the intrinsic damage threshold irradiance of doped silica. Other nonlinear processes such as self-focusing and stimulated Brillouin scattering are also important. We present here the results of our measurements of the damage threshold, and of our analysis of how self-focusing and Brillouin scattering influence the power limit.