基于频域介电谱法的变压器油纸绝缘套管受潮状况分析

近年来频域介电谱法(frequency domain spectrum,FDS)作为一种无损检测方法,逐渐被尝试用来检测大型变压器、套管等油纸绝缘设备的绝缘状态。采用该方法对某500 kV变电站主变压器高中压中性点套管及低压故障套管进行了现场离线测量,然后将所测结果与实验室结果进行比对,分析其故障原因,实现了对现场实测数据的定性和定量分析,确认该批次套管存在出厂时套管芯子干燥不充分问题。研究表明,频域介电谱法不仅能够定性地反映套管内部受潮状况和受潮原因,而且还可以对其受潮程度进行定量分析,从而为该方法在实际生产中的进一步应用提供了理论和实践基础。     

湿蒸汽两相流湿度测量方法研究进展

总结了汽轮机中湿蒸汽两相流湿度测量的研究方法。介绍了传统的热力学法、光学法等测量方法及研究进展情况,并对目前湿度测量的一些新的方法,新型加热法、显微视频技术和微粒图像速度仪测量法、微波测量法、光纤光栅测量法等,进行了分析和研究。     

油浸式变压器绝缘含水量检测新方法

电力变压器绝缘结构中的水分会降低其介电常数,使其过早老化,从而威胁变压器的正常安全工作,在变压器制造及使用中,监测绝缘纸板中的微水分十分重要。针对目前几种测定油浸纸绝缘含水量方法的弊端,介绍了一种新的测定方法——介电频谱法,并采用该方法举例分析变压器受潮故障,实践证明了该方法的实用性和可靠性。     

储粮通风降水系统的研究

通过对9种机械通风降水系统的研究,优选出全敞式地槽鼓风降水系统、地上风道鼓风降水系统、排风扇等负压通风降水系统等三类通风降水系统。对含水量为16～17％的玉米进行试验,能够有效地降低到安全水分13％,对保持储粮品质具有良好的作用。其风网设计较为合理,气流分布较为均匀。通风降水系统中,单位风量、管道风速、表层风速、静压、开孔率、途径比等测定数据均符合设计要求,具有效果好、能耗低、费用少的经济效益和社会效益。     

作物生长条件下蒸发与蒸腾的模拟及土壤水份动态预报

以由能量平衡原理及边界层水汽扩散理论而导出的Ｐｅｎｍａｎ－Ｍｏｎｔｅｉｔｈ公式为基础，确立了棵间潜在蒸发及潜在植株蒸腾的计算模式．建立了以作物根量分布为基础的根系吸水模型．结合实测资料，导出了棵间实际蒸发的经验模式．应用上述经验与半经验模型，结合非饱和土壤水份运移方程，对田间土壤水份动态进行了模拟与预测，其结果与实测结果拟合较好．     

基于MODIS和AMSR-E遥感数据的土壤水分降尺度研究

微波传感器获得的土壤水分产品空间分辨率一般都很粗,而流域尺度上的研究需要中高分辨率的土壤水分数据。用MODIS逐日地表温度产品MOD11A1和逐日地表反射率产品MOD09GA构建温度-植被指数特征空间,并计算得到TVDI(Temperature Vegetation Dryness Index)指数,它与土壤水分呈负相关关系,能够反映土壤水分的空间分布模式,但并不是真实的土壤水分值。在AMSR-E像元尺度上求得TVDI与土壤水分的负相关系数,进而对VUA AMSR-E土壤水分产品进行降尺度计算得到0.01°分辨率的真实土壤水分值。经NAFE06(The National Airborne Field Experiment 2006)试验地面采样数据验证,降尺度后的土壤水分均方根误差平均值为6.1%。     

装备维修器材防潮包装干燥剂使用研究

对干燥剂的特点、使用要求、使用方法、包装用量等进行了研究,通过实例进行了说明,同时针对防潮包装实践,对防潮包装设计环节如何提高装备维修器材防潮包装的可靠性进行了研究。     

高性能PCB基体树脂的研究进展

概述了目前用于高性能印刷电路板的几种新型基体树脂,介绍了它们的发展方向和应用前景。     

野战弹药封套材料的透湿率指标论证

通过计算封套内部的相对湿度,论证了野战弹药封套材料的透湿率指标.     

Water-assisted sub-critical crack growth along an interface between polyimide passivation and epoxy underfill

Direct chip attach (DCA) microelectronic packaging technology is gaining prominence due to its numerous advantages. Delamination (debonding) of the underfill epoxy/ polyimide passivation interface of a DCA during hydro-thermal reliability testing has always been one of the salient problems. We have studied the water-assisted sub-critical crack growth along this interface and our measurement offers important clues as to the origins of the poor hydro-thermal testing results for these interfaces. A modified asymmetric double cantilever beam (ADCB) testing technique has been used to measure the sub-critical crack growth velocity v at various relative humidities and temperatures as a function of the crack driving force (strain energy release rate) G ^*. The presence of a significant partial pressure of water p _H2O produces a marked decrease (by up to a factor of 12) in the threshold G ^* for crack growth at measurable velocities. Above the threshold log v rises linearly with but then enters a regime where the crack velocity (v=v ^*) is almost independent of . Finally, at the values of G ^* corresponding to rapid crack propagation in the absence of water, log v increases very rapidly with G ^*. By analogy to the classic work on water-assisted sub-critical crack growth in silica-based glasses, where very similar features are observed, we believe that the sub-critical crack growth along the polyimide-epoxy interface results from stress-assisted hydrolysis of primary covalent bonds, in our case ester bonds across the interface. The regime of just above the threshold corresponds to a physicochemical situation where the water activity (p _{H 2O} ) at the crack tip is the same as that of the gaseous environment. In the regime where v=v ^* constant, the water activity at the crack tip is below that in the environment and the crack growth velocity is limited by the transport of water vapor to the bonds ahead of the crack tip. We develop a model of this crack growth following Wiederhorn 1967 that allows us to predict the sub-critical crack growth as a function of G ^* for arbitrary relative humidity and temperature conditions.