采用串联电抗器限制青海西宁地区电网短路电流研究

随着青海电网规模的不断增大,短路电流超标已成为电力系统安全运行面临的重大问题。分析青海西宁地区短路电流的发展趋势,分析青海东部地区750 kV母线短路电流超标的原因,利用支路阻抗追加法计算装设串联电抗器后节点阻抗参数和母线短路电流,并在此基础上提出限制青海东部地区短路电流的措施,研究成果可为青海电网限制短路电流提供借鉴。     

基于零序电压相位变化的分布式光伏发电孤岛保护方法

分布式光伏主要接入35 kV及以下低压配电网,低压配电网故障主要以单相接地故障为主,约占70%以上。由于单相接地故障不影响系统功率正常输送,当电网发生故障时,常规分布式光伏孤岛保护方法存在孤岛判别失效及不可靠问题,给电网安全稳定运行带来严重挑战。首先,推导了电网发生单相接地故障时的零序电压表达式,定性分析了影响零序电压大小和相位的关键因素。其次,对比分析了电网中性点不接电和经消弧线圈接地2种方式下,电网发生单相接地故障时的零序电压大小和相位变化规律,在此基础上,提出了基于零序电压相位变化的分布式光伏孤岛识别方法。最后,对所提出的孤岛保护方法在实际工程中的应用提出建议。     

基于HBCORS无验潮水深测量技术在荆江河段的应用初探

目前,水道地形测量模式已基本定型于利用GPS测定水底点的平面位置,利用测深仪测定水底点的水深,附之以瞬时潮位或水位资料,获得点位的高程。随着各地连续运行卫星定位服务系统的投入运行,本文提出了一种无验潮模式下的水道地形测量模式,即不测定潮位或水位,而直接利用HBCORS的RTK测量技术,从而获得高精度的水底点高程。本文通过实际工程,用无验潮模式与传统模式在精度上进行对比,得出了该方法在精度上和效率上都有很大的提高,值得推广应用。     

Homotopy analysis of unsteady heat transfer started impulsively from rest along a symmetric wedge

In this paper, the unsteady heat transfer over an impulsively started wedge is investigated. The mixed convection, namely, the thermal boundary-layer growth is caused by the sudden increase of the surface temperature as it is set into motion. The analytic approximations with high accuracy are given using the Homotopy–Padé technique, which agree well with the numerical results using an implicit finite-difference method known as Keller–Box method. It is found that the Homotopy–Padé approximations have no relation to the auxiliary parameters ?_f and ?_g, which play important roles in the homotopy analysis method.     

Effect of Spherical Ni Powder on Microstructure of Secondary Carbon in MgO-C Refractories Matrix

In order to tackle the shortcomings of high brittleness,hard graphitization,and poor oxidation resistance resulted from carbonization of phenolic resin of Mg O- C refractories, effects of 2 mass% spherical Ni, and2 mass% spherical Ni plus 7. 5 mass% Al composite powder on microstructure of the secondary carbon in Mg O- C refractories matrix were investigated. The results show that a large number of carbon whiskers form after the carbonization of phenolic resin with Ni powder;in the Mg O- C refractories matrix with only Ni powder,the carbon microspheres form at all treatment temperatures and change slightly with the temperature rising;the carbon whiskers begin to generate in the specimens with composite powder at 1 000 ℃,the diameter of the carbon whiskers is about 0. 4- 0. 5 μm,and the length is about 3- 4 μm,and the formed carbon whiskers increase gradually with the temperature rising.     

变温吸附法分离氯气氧气工艺技术研究

采用变温吸附的方法将氯化氢催化氧化产物中氯气和氧气进行分离提纯,通过正交实验考察了吸附压力、吸附时间、吸附温度和解析温度对解析气中氯气的浓度和回收率的影响。实验结果表明在吸附压力为2 bar、吸附时间为50 min、吸附温度为40℃、解析温度为100℃的条件下,解析气中氯气的浓度和回收率最大,分别为99.8%、88.4%。     

含氟有机化合物的双疏特性及其研究进展

综述了具有双疏特性的有机氟化合物的物理化学性质,含氟有机化合物织物整理剂、有机聚合材料及表面改性的研究进展。     

国外中、高碳钢优质线材用方坯表面清理方法

阐述了中，高碳钢优质线材用方坯的表面质量要求，介绍了国外一些钢厂采用的表面清理工艺和表面缺陷在线检测与清理设备，提出了武钢添置优质线材用方坯表面清理设备的有关建议。