Breakdown characteristics of oil and paper insulation for a very fast transient voltage

This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043     

黑岱沟露天矿重型汽车预防性维修的探讨

通过对黑岱沟露天煤矿运输设备出动率调查,初步分析了目前主要运输设备的现状以及存在问题的原因和影响因素,就加大预防性维修的比重,实行全面的预防性维修制度提出了一些看法。     

复合聚全氟乙丙烯材料的介电及高频击穿性能研究

在聚全氟乙丙烯(FEP)中添加 TiO_2和 Al_2O_3,通过热压成型的方法制备了 FEP/TiO_2复合材料和 FEP/Al_2O_3复合材料,研究了氧化物添加量对复合材料介电常数、介电损耗和高频击穿性能的影响。结果表明,随氧化物含量的增加,复合材料的介电常数和介电损耗均增加;在同一添加量下,TiO_2对复合体系的介电性能影响较大。FEP/TiO_2复合材料的高频击穿性能随 TiO_2含量的增加而下降,在 TiO_2含量为4.0%(质量分数,下同)时,复合材料的损伤阈值已降为 FEP 材料损伤阈值的48.9 %。而 FEP/Al_2O_3复合材料的高频击穿性能随 Al_2O_3含量的增加而升高,当 Al_2O_3含量为1.2%时,复合材料的损伤阈值已增大到 FEP 材料损伤阈值的2倍,达到313 J/m~2。     

三相异步电动机运行指标的分析

利用电机学理论分析了影响电机起动转矩、起动电流、最大转矩和最小转矩的因素。     

提高钢水质量减少铸件气孔

通过规范冶炼的操作，加强冶炼过程控制，细化分解技术指标，制定奖励方案，提高了钢水质量，解决了铰链梁铸件的气孔问题。     

Species separation during coating growth on aluminium by spark anodizing

The mechanism of coating growth during sparking anodizing of aluminium is probed by use of an electrolyte containing both silicate and phosphate ions, with subsequent determination of the locations of silicon and phosphorus species through the coating thickness. Importantly, the main alumina-based layer of the coating contains incorporated silicon and phosphorus species of differing distributions. Phosphorus species are primarily found in a region next to the metal, representing roughly about 30% of the layer thickness. Silicon species are located mainly above this region to the layer surface. New coating material is added in discreet amounts associated with breakdown events, which provide short-circuit paths through the layer. The growth processes within the discharge region result in separation of the silicate- and phosphate-derived species, which may relate to their different mobilities, dependent upon factors such as charge, size and bonding with other species. Further, silicon-rich material is deposited at the surface of the alumina-based layer, which is often encountered in spark anodizing in silicate electrolyte.     

A multi-echelon production–inventory system with supply disruption

The article investigates an integrated multi-layer supply chain model consisting of supplier, manufacturer and retailer while supply disruption, machine breakdown, safety stock, maintenance breakdown occur simultaneously. At beginning of the production, manufacturer keeps some raw materials in stock received from second supplier at high price, as safety stock due to supply disruption of first supplier. Corrective maintenance is done immediately to restore its normal stage when machine breakdown occurs. Stock out situations at manufacturer and retailer are considered due to disruption of production for machine breakdown. The integrated expected costs of the chain in centralized (collaborating) and decentralized (Stakelberg approach) system are compared. A numerical example and its sensitivity analysis are provided to test feasibility of the model.     

制气废热锅炉故障分析及对策

制气废热锅炉用于吸收制气炉产生的尾气余热，是一种节能设备。该炉利用煤气发生炉的尾气通过换热反净化的水加热成饱和蒸汽，以供生产之用。本文就我厂重油裂解制气系统中三台废热锅炉出现的故障进行分析，从中找出故障的原因及处理办法。     

釜用机械密封的安装及故障分析

针对石油化工釜用机械密封中常出现的故障进行分析 ,并提出了改进措施 ,以便使机械密封更好地发挥作用 ,杜绝化工设备存在的跑、冒、滴、漏现象 ,即改善了环境 ,又节约了能源。     

测井资料在井壁稳定性研究中的应用

井壁稳定性问题是石油钻井工业面临的一个重大课题。利用测井资料研究井壁稳定性是一种有效的方法。文章利用声波、密度测井资料计算了岩石力学参数、岩石强度参数，在此基础上进行了地应力计算、进而确定了地层破裂压力和坍塌压力，预测了安全钻井液密度范围，为钻井设计提供参考，并可指导安全钻井。通过新疆X 201井安全钻井液密度窗口的测井预测值与实钻钻井液密度对比分析，证明利用测井资料评价井壁稳定性的可行性和准确性，具有工程应用价值。