断路器跳位监视回路与防跳的配合实例分析

本文在对断路器机构防跳和保护防跳的二次回路分析基础上,对工程实例中断路器跳位监视回路的接线方式进行了理论分析.然后通过工程实例证明了理论分析的正确性,指出当断路器采用保护防跳时,跳位监视回路应选择直接接入合闸回路;断路器采用机构防跳时,跳位监视回路应选择串断路器常闭接点与防跳常闭接点后接入合闸回路.最后根据试验现象对以...     

带合闸电阻的断路器特性参数的现场测试

断路器是电网的重要电气设备,电力系统中的投、切空载线路,会产生操作过电压。为此,要在断路器上装设合闸电阻,释放电网的能量,从而保护电网电气设备。合闸电阻在主断口(灭弧室)合闸前的几个毫秒投入,在主断口合上若干毫秒后自动切除。提前投入时间的准确性在电网中很重要,在新设备投运前,现场测试断路器特性参数是十分必要的。     

断路器合闸过电压计算与分析

针对550kV变电站罐式断路器在投入空载输电线路时引起的断路器合闸电阻损坏问题,通过利用电磁暂态程序EMTP仿真单相断路器在不同合闸相角下的合闸过电压,计算了暂态过电压下合闸电阻的热量,发现合闸电阻故障的原因,重点分析了合闸过电压对断路器中合闸电阻绝缘的影响.仿真结果表明,由于线路中电抗器对合闸过电压具有一定的抑制作用,因此,各个节点上的过电压幅值较小,同时,合闸相角对合闸过电压幅值具有一定的影响.     

断路器操作机构压力低对继电保护的影响及对策

分析了断路器的液压和气动操作机构中“压力低闭锁重合闸”回路的重要性,该回路缺失可能会发生非预期合闸,对断路器的安全和电网的稳定构成了威胁.针对存在的问题,提出了线路间隔断路器操作压力低闭锁重合闸回路的解决方案,明确了断路器操作机构压力和SF6气体压力低闭锁功能的实现方式.还对线路保护带断路器传动试验中的时序配合问题进行了简要分析.     

110kV断路器跳合闸回路故障分析

文章对一起110kV断路器不能合闸原因进行分析,并提出对跳合闸回路的合理改造,改造后回路可以避免跳合闸线圈烧毁。     

电力系统110KV变电站35KV断路器合闸线圈烧坏原因浅析

首先概述了现阶段电力输变电系统110KV变电站内35KV高压电气开关保护回路稳定性的基本现状,深入讨论影响高压断路器合闸回路合闸可靠性、稳定性的主要因素及预防措施.提高电力系统高压断路器的稳定性和安全可靠性不仅是输变电系统保护控制的首要目的,也是电力系统有效运行的主要条件.在此提出自己的一些观点和同仁探讨交流.     

超高压断路器合闸电阻测量方法

为了使断路器年度预防性试验中合闸电阻的测量工作变得安全、简便、准确、高效,在分析现有高压断路器合闸过渡电阻测量方法局限性的基础上,探讨电压比值法和电流比值法测量超高压断路器合闸过渡电阻的方法与原理,并用实例验证测量方法的可行性,针对不同的现场试验条件提出2种测量方法的选取建议,为电力系统推广此技术提供参考依据.     

500kV断路器取消合闸电阻问题的探讨

通过采用消除数值振荡的特征差分法和Monte Carlo法对多条500kV线路进行统计模拟计算,研究了取消线路侧断路器合闸电阻后500kV电力系统合闸过电压和金属氧化物避雷器耗散能量的一些统计规律,提出了取消500kV电力系统线路侧断路器合闸电阻的判据,这一结果可作为有关工程设计的参考。     

ZN28系列户内式6KV小车断路器合闸线圈烧毁原因分析及处理方法

本文通过对一起ZN28系列户内式6KV小车断路器合闸线圈的烧毁原因进行分析,论述事故发生的原因,并提出处理方法。     

重合闸在500kV系统应用的几个问题

500kV系统变电站主接线大部分采用一个半断路器接线,一条出线对应两个开关,线路保护CT采用和电流,中间开关同时和两条出线有关联等。一个半断路器接线的复杂性主要体现在开关保护及自动装置的配合上,因此重合闸应用是一个较为复杂的问题。理清楚重合闸的原理和应用对500kV系统安全生产有着十分重要的意义。     

中国共产党第一代领导集体的人才特色

中国共产党第一代领导集体 ,可谓群星荟萃。毛泽东的统帅才能 ,刘少奇的理论才干和独当一面的本领 ,周恩来的杰出外交才华和处理事务的灵活周到 ,朱德的军事才干 ,任弼时的处理日常事务的详备细致 ,陈云的精细理财能力 ,邓小平的务实和不时闪现的帅才光芒 ,等等 ,各有千秋。本文粗线条地探讨这一人才群体中毛、刘、周、陈、邓五位代表人物的才能特点及表现 ,阐明其人才组合优势。     

中和度对水性硅溶胶/聚氨酯杂化树脂交联性能的影响

水性聚氨酯/无机复合材料兼具有机物和无机物的优点,是一类非常有发展前景的复合材料。然而,有机物与无机物之间的差异使两相相容性不好,不仅限制了无机材料在聚合物基体中的作用而且导致复合材料结构不均,综合性能下降。因此,保证无机粒子在聚氨酯基体中的均匀分散是制备性能优异的水性聚氨酯/无机复合材料的关键。本文将高支化度的水性硅溶胶（KS560）添加到3–氨基丙基三乙氧基硅烷（APTES）封端的WPU乳液中,通过sol-gel反应制备了均一的水性聚氨酯/SiO₂复合乳液（WPU/SiO₂）。体系的中和度（DN）由三乙胺/2,2–二羟甲基丙酸（TEA/DMPA）的摩尔比控制。研究了体系DN值对复合乳液结构和性能的影响。通过²⁹Si NMR及流变实验证实WPU与KS560之间的化学交联结构。随着DN值增加,这种化学交联程度增大,使得流变的储能模量值降低。SEM照片发现KS560的加入可分散转移成膜过程中产生的应力,并阻止裂纹的形成。而DN值增加有利于改善复合胶膜表面的平整度。同时,KS560为WPU引入了聚硅氧烷网络结构,使复合材料热稳定性,耐水性及力学性能均得到提高。当DN为80%时,复合材料的吸水率达到最低值4%。另外,随DN值增加,KS560与WPU之间的界面强度,KS560之间的缩合程度增加,这使复合材料的拉伸强度及模量值均增加。因此,DN值为80%时可制备综合性能优异的WPU/SiO₂复合材料。     

Analysis of the effects of the heat of sorption on the process of heat transfer in moisture exchange across a membrane

A theoretical study has been conducted to investigate the effects of mass transfer on heat transfer in moisture exchange across a membrane and a mathematical model describing the heat transfer process with consideration of the heat of sorption was established. A dimensionless variable, Ψ =JLλ /δ (T ₁₀−T ₂₀), which controls the effect of the heat of sorption on the heat transfer in membrane process, was obtained through theoretical analysis, and the effects of Ψ on the heat transfer process were analyzed. Results showed that in the case that the temperature gradient and mass transfer are in the same direction, the effective heat flux changes the direction at Ψ=1. For Ψ<1, the heat transfers from high to low temperature sides through the membrane, and the total thermal resistance increases with increasing the moisture flux across membrane or reducing the temperature difference between the bulk flows on the two sides of membrane. For Ψ>1, the overall effect of the heat and mass transfer is that the effective heat flux points from low to high temperature sides and the total thermal resistance decreases with increasing the mass flux or reducing the temperature difference. In the case that the temperature gradient and mass transfer are in the opposite directions, the existence of the heat of sorption acts to enhance the heat transfer from high to low temperature sides, causing a reduced total thermal resistance, and the greater the mass flux or the smaller the temperature difference, the smaller the total thermal resistance. Supported by the National Natural Science Foundation of China (Grant No. 50576040)     

关于计算中心管理中存在的问题及对策

论文结合我校实际，列举了计算中心存在的四个问题：实验室人员长期缺编，实验技术人员职称结构不尽合理；实验室工作人员参与科研和为社会服务的积极性不高；大量计算机超期服役，设备投入计划性不强；实验指导书和实验上机操作等实验文件尚不健全．应采取三个对策；注重人才培养和队伍建设；建立健全各种规章制度，做到有章可依；保持良好服态度，提高服务质量．     

地区电网母线电压合格率管理的研究与应用

通过对某地区电网电压合格率管理模式进行研究,分析无功电压管理现状和面临形势,提出完善支撑手段为管理前提、强化实时调整为管理核心、开展专业分析为管理保障、优化电网结构为管理根本、实施考核评价为管理手段,"五维一体"建立跨部门、跨专业、跨层级协同管理工作机制,形成地区电网电压合格率的管理新模式。将该管理模式在某地区电网实施应用,电网母线电压合格率提升至99. 96%,提升了电能质量,创造了良好的经济效益,为其他地区电网企业电压管理提供有益的参考。     

Pore structure characteristics of the relative water-resisting layer on the top of the Ordovician in Longgu Coal Mine

In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 × 10⁻³–2.782762 × 10⁻³, 4.1092 × 10⁻³–7.3387 × 10⁻³ and 2.0891 × 10⁻³–3.2705 × 10⁻³ μm², respectively, and porosity of that is 0.6786–0.9197%, 0.3109–0.3951% and 0.9829–1.8655%, respectively. The results indicate that: (1) the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 μm; (2) the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; (3) the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m; and (4) the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting layers.     

局部放电带电检测技术在GIS设备缺陷诊断中的应用

根据1起典型的GIS设备隔离开关内部安装工艺问题导致的悬浮电位局部放电缺陷诊断,通过射频巡检技术、特高频局部放电检测技术、超声波局部放电检测技术、六氟化硫气体成分检测技术等多种方法联合,确定缺陷性质并进行精确定位,指导针对性检修处理,阐述局部放电检测应用技术、故障精确定位方法以及缺陷解体检修验证过程的现场实际经验。通过分析,特高频与超声波局部放电检测技术能够高效、精确地发现GIS设备内部缺陷,这种技术的可操作性强,适宜全面推广。     

速度滑移下液压主轴轴心轨迹动态研究

基于载荷增量法和扰动压力法,研究液体液压主轴系统的动态性能。通过有限差分法求解计入微尺度速度滑移效应的不定常油膜压力分布的雷诺方程,并得出非线性油膜力。应用载荷增量法和扰动压力法求解反映油膜动态特性的4个动态刚度和阻尼系数,并用于转子轴心轨迹的动力学描述,求解存在偏心质量下的转子轴心轨迹,实现液压主轴系统的流-固耦合分析。研究结果表明：速度滑移对液压主轴的动态刚度和阻尼性能造成了一定的影响。动刚度系数K_xx、K_xy、K_yx和K_yy受滑移影响降低的最大比率分别为4.85%、4.85%、7.20%、7.16%,速度滑移降低了油膜阻尼系数C_yx、C_xy和C_yy,阻尼系数C_xx受滑移影响比较复杂;随着转子偏心质量距的不断增加,主轴轴心运行轨迹在不断扩大,系统的稳定性不断降低。最后,通过液压主轴回转精度实验验证了轴心轨迹模型的正确性和有效性。     

浅析知识经济对财务会计的影响

知识经济的出现并迅速发展壮大，对现行会计理论带来了广泛而深远的影响，中就知识经济对会计目标、会计假设、记账方法、会计计量、会计核算、无形资产、财务报告等现行会计理论的影响作了分析。     

Effect of the benzene ring of the dispersant on the rheological characteristics of coal-water slurry: Experiments and theoretical calculations

In this study,low-rank coal-water slurry(LCWS) was prepared using polyoxyethylene dodecylphenol ether(PDPE) and polyoxyethylene lauryl ether(PLE),respectively.A combination of experiments and simulations was used to investigate the pulping properties and microscopic mechanism of the LCWS samples prepared using the two agents,so as to explore the influence of benzene ring on the performance of dispersant.The results of the LCWS preparation experiments revealed that the pulp-forming performance of PDPE exceeded that of PLE.When LCWS concentration is 62%,64%,and 66%,the apparent viscosity corresponding to PDPE is 247.80,504.17,and 653.10 mPa·s,and the apparent viscosity corresponding to PLE is 548.10,1470.61,and 1549.98 mPa·s,respectively.The C_(1000)(When the apparent viscosity is 1000 mPa·s,the corresponding concentration of LCWS is defined as C_(1000)) values of PDPE and PLE are 67.60% and 62.95%,respectively.In addition to the van der Waals forces and hydrogen bonds between the PDPE and/or PLE molecules and coal,the benzene rings of PDPE present π-π stacking effect with the aromatic rings of coal.That could facilitate and strengthen the adsorption of PDPE on coal,which would be conducive to further improving the dispersion of coal particles.The two dispersants have no significant difference in effect on the pyrolysis of LCWS.The simulation results indicated that the times for PDPE and PLE molecules to reach flat adsorption state on coal are approximately 290 and 565 ps,respectively.The self-diffusion coefficient(D) of the PDPE and PLE on coal is 3.16 x 10~(-6) and6.57×10~(-6) m~2/s,respectively,and their interaction energies with coal are 785.71 and 648.60 kcal/mol,respectively.The results of the simulation calculations demonstrated that PDPE adsorbed on coal easier than PLE,and its binding is more stable than that of PLE owing to the π-π stacking effect,which is conducive to uniform dispersion of coal in solution.The simulation results confirmed the experimental results.