架空输电线路鸟害防治措施研究现状及展望

鸟害是威胁架空输电线路安全稳定运行的重要因素之一。全面分析和评价应用于国内外输电线路的鸟害故障防治措施,提出了应重视鸟害防治工作、借鉴其他学科研究成果、建立引鸟、驱鸟、防鸟三位一体的鸟害防治体系,绘制鸟害等级区划图等建议,以期为提高电网的安全可靠性、防治鸟害故障提供参考。     

架空输电线路的鸟害故障对策措施研究

随着社会经济的发展,人们对生活质量要求越来越高,电力行业也随之得到快速的提升。然而在日常生活中一些鸟害因素造成输电线路杆塔故障。本文主要针对架空输配电线杆塔因受到过电压、机械伤害和空气等多种原因导致的鸟害故障进行研究。通过分析其具体原因发现安装避雷器可以有效减少鸟类与地面之间的摩擦力从而降低对电力系统设备带来损伤,使电网得到进一步优化。     

220 kV线路鸟害故障分析及防治对策

针对巴彦淖尔河套地区近年来220kV线路连续不断发生的鸟害故障,通过分析比较,阐述了鸟类对架空电力线路的危害,分析了河套地区鸟害故障的原因特征及故障规律,并结合工作实际提出了具体的防鸟害措施。     

模糊评价与PSO优化的LSSVM架空输电线路故障率预测

准确计算架空线路故障率对于保障线路安全稳定运行有重要意义。分析确定架空输电线路故障的影响因素,将其划分为4个一级指标和21个二级指标,建立线路故障指标评价体系。分别采用三角分布法和模糊试验法确定定量指标和定性指标的隶属度函数,利用九分度AHP法计算各指标权重,通过模糊运算得到各影响因素的评价值。根据故障造成损失的严重程度,划分故障为缺陷、失效和事故三类;采用粒子群算法对LSSVM进行参数寻优,以运行时间和4个一级指标为支持向量,建立线路I级故障率预测模型,经检验该模型的平均相对误差为2.36%。算例验证了此线路故障率计算方法的有效性,计算结果可为电力部门制定线路运维措施提供参考。     

输电线路鸟粪故障分析与工程治理

为有效降低鸟粪故障跳闸发生的频次,通过分析研究其共性特点,找出鸟类体积尺寸和地理环境系数关键技术指标并进行了量化,建立了统一鸟害系数与防鸟害措施的一一对应关系,给出了体系建设过程中鸟类体积尺寸确定、防鸟技术分类、现场调查、防鸟害评估等具体方法和范例,由此建立了鸟害区段图绘制的理论基础,提出了混合型防鸟害技术思路和干字型塔中相吊串防鸟害新技术。实例应用表明,该治理技术效果明显。     

—种新型35kV电缆登杆平台全绝缘架空引下线装置研制

针对国内外35 kV架空输电线路引下线装置因各类外力而造成的破坏难题,对现有35 kV引下线装置外力破坏故障原因进行了分析,总结现有防护外力破坏装置的不足之处,分别从引下线绝缘层厚度、材质以及绝缘胶片包材设计等方面进行了研究,选取安全可靠、电气性能优异的材料制造了满足35 kV输配电线路引下线装置所需的绝缘导线和绝缘胶片包材,提升了35 kV输配电线路引下线装置防止外力破坏的效果,从而更好地确保35 kV输配电线路的安全可靠运行。     

架空电力线路鸟害分析与预防

针对鸟类的频繁活动极易造成电力架空线路故障甚至事故,从鸟害的形成机理上进行分析和归类,并提出了相应的防治措施。     

起动初始条件对GDI汽油机反转直接起动模式实现的影响

针对一台4G15缸内直喷汽油机试验研究了冷却水温、活塞初始位置、油轨内燃油压力等起动初始条件对反转直接起动模式实现的影响,并分析了在不同初始条件下膨胀缸和压缩缸控制参数的优化选取策略。研究结果表明:随着初始条件的变化,与之相匹配的优化控制参数也有所改变。燃油压力和冷却水温降低后,需采用较浓的混合气。冷却水温在70~80℃之间时有利于反转起动模式的实现,提高燃油压力同样也有利于反转起动模式的实现。为使反转直接起动模式成功实现,活塞初始位置需要控制在适当的范围内,当压缩缸活塞初始位置处于上止点后曲轴转角为-60°~70°之间时,在压缩缸和膨胀缸相继着火后可使发动机获得较大的正向转动速度,有利于提高起动响应性。     

脉冲注入法用于直流输电系统接地极线路故障测距

摘要： 分析了直流输电系统在双极运行方式下,外部注入脉冲信号在接地极线路上的传播过程,提出一种利用注入脉冲信号的直流输电系统接地极线路故障测距方法。该方法通过周期性地从接地极线路始端注入脉冲信号探测线路是否发生故障,在判断线路发生故障后,通过改变注入脉冲信号的宽度和脉冲极性探测故障点位置,最后以取平均值的方式得到故障测距结果。以PSCAD/EMTDC为仿真平台,搭建了直流输电系统在双极运行方式下的接地线路故障测距仿真模型,并借助MATLAB对仿真波形数据进行分析,仿真结果表明该方法是可行的。     

基于SCADA数据的国产风力机可靠性评估

基于国内某风电场SCADA系统的现场数据,评估国产风力机的可靠性。通过对故障数据的归类分析,根据故障率、停机时间等指标确定影响风力机可靠性的关键零部件;采用相关性函数分析风力机故障率与环境温度的相关性;利用时间序列方法分析风力机故障率和可靠性的季节性特征。分析结果表明:与文献中的风力机故障数据相比,所研究风力机样本的故障频率偏高,其中,电气系统和控制系统的故障率最高、平均维修时间较短,主轴、齿轮箱和发电机的故障率低、平均维修时间较长。此外,该组风力机的故障率与环境温度具有明显的相关性,表现出较为显著的季节性特征。     

Thermal performance of a shallow solar-pond integrated with a baffle plate

A shallow solar-pond integrated with a baffle plate is investigated theoretically and experimentally under Tanta prevailing weather conditions. A transient mathematical model is presented for the pond. The energy-balance equations for various parts of the pond are solved analytically using the elimination technique. In order to validate the theoretical model, experiments are performed under the batch mode of heat extraction with a black painted baffle plate made of stainless steel, with and without vents in the plate, for different masses of water in the upper and lower layers. It is found that the pond-water temperature decreases with increasing vent area; therefore, the baffle plate should be used without vents with shallow depths of the upper water-layer. Experiments have also been carried out using baffle plates made from Al and mica in order to study the effect of the thermal conductivity of the baffle plate on the pond’s performance. The average temperature of the pond water is found to be less dependent on the thermal conductivity of the baffle plate. It is also inferred that the present system could provide 88 L of hot water at a maximum temperature of 71 °C at 3:00 pm with a daily efficiency of 64.3% when the baffle plate is used without vents. The pond can retain hot water until 7:00 am of the next day at a temperature of 43 °C, which can be used for most domestic applications. Comparisons between experimental and theoretical results indicated that the theoretical model could be used for estimating the pond’s performance with good accuracy.     

Effect of different control strategies on rapid cold start-up of a 30-cell proton exchange membrane fuel cell stack

Many places experience extreme temperatures below −30 °C, which is a great challenge for the fuel cell vehicle (FCV). The aim of this study is to optimize the strategy to achieve rapid cold start-up of the 30-cell stack at different temperature conditions. The test shows that the stack rapidly starts within 30 s at an ambient temperature of −20 °C. Turning on the coolant at −25 °C show stability of the cell voltage at both ends due to the end-plate heating, however, voltage of intermediate cells fluctuates sharply, and successful start-up is completed after 60 s. The cold start strategy changes to load-voltage cooperative control mode when the ambient temperature reduced to −30 °C, the voltage of multiple cells in the middle of the stack fluctuate more drastic, and start-up takes 113 s. The performance and consistency of the stack did not decay after 20 cold start-up experiments, which indicates that our control strategies effectively avoided irreversible damage to the stack caused by freeze-thaw process.     

Effect of Inclination Angle and Filling Ratio on Thermal Performance of a Two-Phase Closed Thermosyphon under Normal Operating Conditions

In this paper, the effect of the inclination angle on the thermal performance of a two-phase closed thermosyphon with different filling ratios has been investigated experimentally under normal operating conditions. A series of experiments were carried out for inclination angle range of 5°–90° and filling ratios of 15%, 22%, and 30%. A copper thermosyphon with an outside diameter of 16 mm, an inside diameter of 14.5 mm, and a length of 1000 mm was employed. Distilled water was used as the working fluid. The results show that the two-phase closed thermosyphon has the highest thermal performance in the inclination angle range of 15°–60°. A good agreement was observed between the experimental results of this study and those available in the open literature. The interesting phenomenon of geyser boiling occurred in our experiments for filling ratios equal or greater than 30%. The geyser boiling puts no limitation on thermal performance of thermosyphon, but it should be avoided because it damages the condenser end cap due to the slug striking.     

Study of a novel solar adsorption cooling system and a solar absorption cooling system with new CPC collectors

One two-phase thermo-syphon silica gel-water solar adsorption chiller and LiBr-H₂O absorption chiller with new medium CPC (Compound Parabolic Concentrator) solar collectors were investigated. The reliability of adsorption chiller can be improved, because there is only one vacuum valve in this innovative design. Medium temperature evacuated-tube CPC solar collectors were firstly utilized in the LiBr-H₂O air conditioning system. The former system was applied in north of China at Latitude 37.45° (Dezhou city, China), the latter system was applied at Latitude 36.65° (Jinan city, China). Experimental results showed that the adsorption chiller can be powered by 55 °C of hot water. The adsorption chiller can provide 15 °C of chilled water from 9:30 to 17:00, the average solar COP (COPs) of the system is 0.16. In the absorption cooling system, the efficiency of the medium temperature evacuated-tube CPC solar collector can reach 0.5 when the hot water temperature is 125 °C. The absorption chiller can provide 15 °C of chilled water from 11:00 to 15:30, and the average solar COPs of absorption system is 0.19.     

Experimental performance of cooling photovoltaic panels using geothermal energy in an arid climate

In this study, an experimental prototype was built to examine the use of an underground water tank as a heat exchange medium with the soil to reduce photovoltaic (PV) panel operation temperatures and simultaneously improve PV efficiency. Three PV systems were evaluated: a benchmark PV panel without cooling (panel A); a PV panel with water spray cooling (panel B); and a PV panel with evaporative cooling (panel C). The cooling techniques in modules (B) and (C) were used to investigate the effects of underground water on the performance of PV panels in arid conditions. Four cases were devised as follows: spray panel back cooling (I), spray front and back cooling (II), spray front and back cooling using an Arduino controller (III), and repeating case III with different water flow rates (IV). Readings were taken from 9:00 am to 4:00 pm  from May to August. The experimental results showed that the use of underground water spray cooling led to reductions in the temperature of PV panel B, 14°C, 17.6°C, 18.8°C, and 22.7°C for cases I, II, III, and IV, respectively, when compared with the uncooled panel, and efficiency improved by 3.5%, 4.8%, 18%, and 23.1%, respectively.     

沟道坡度对泥石流起动模式影响的模拟试验研究

沟道内松散堆积物在不同坡度下形成泥石流的机理不同,为研究沟道坡度对泥石流起动模式的影响,通过泥石流物理模拟进行了松散堆积体形成泥石流的试验,选取5组坡度和三种级配研究了不同坡度和级配下松散堆积体形成泥石流的起动方式。结果表明,沟道堆积物在坡度为14°和15°时呈典型的沟床起动特征,在坡度大于15°时呈滑坡流态化起动特征,临界坡度在15°与16°之间;泥石流起动时孔隙水压力随堆积体级配减小而减小,重度随堆积体级配减小而增大,级配对泥石流形成方式无明显影响。     

Performance analysis of direct solar dryer driven by photovoltaic thermal energy recovery and solar air collector for drying materials and electricity generation

The direct-type solar dryer is characterized by very simple construction, less maintenance, cost-effectiveness, and is easy to handle. The present study aims to enhance the performance of a direct-type solar dryer. To achieve this, the photovoltaic (PV) panels with thermal energy recovery and solar air collector were integrated with the direct-type solar dryer. In this study, the PV panels with thermal energy recovery and solar air collector were utilized as preheating units to raise the air temperature before entering the direct solar dryer. Moreover, the PV panels were utilized to drive the air blower. In this study, three incorporated models are suggested to study the performance of the solar dryer integrated with PV panels with thermal energy recovery and solar air collector. The model of each component was validated by the previously recorded empirical data. The results confirmed that the dual utilization of the PV panels with thermal energy recovery and solar air collector as a preheating unit raised the air temperature entering the direct solar dryer by the rate varying between 29°C and 42°C within the period 9:00 a.m.–4:00 p.m. Also, the moisture content of banana samples inside the direct solar dryer reduced from the initial value of 72% (wb) to the value of 33.4% (wb) within 7 h (9:00 a.m.–4:00 p.m.). During this operating period, moisture removal from the banana samples varied between 110 and 400 g/h.     

CFD analysis of hydrogen injection pressure and valve profile law effects on backfire and pre-ignition phenomena in hydrogen-diesel dual fuel engine

This paper focuses on optimizing the hydrogen TMI (timed manifold injection) system through valve lift law and hydrogen injection parameters (pressure, injection inclination and timing) in order to prevent backfire phenomena and improve the volumetric efficiency and mixture formation quality of a dual fuel diesel engine operating at high load and high hydrogen energy share. This was achieved through a numerical simulation using CFD code ANSYS Fluent, developed for a single cylinder hydrogen-diesel dual fuel engine, at constant engine speed of 1500 rpm, 90% of load and 42.5% hydrogen energy share. The developed tool was validated using experimental data. As a results, the operating conditions of maximum valve lift = 10.60 mm and inlet valve closing = 30 °CA ABDC (MVL10 IVC30) prevent the engine from backfire and pre-ignition, and ensure a high volumetric efficiency. Moreover, a hydrogen start of injection of 60 °CA ATDC (HSOI60) is appropriate to provide a pre-cooling effect and thus, reduce the pre-ignition sources and helps to quench any hot residual combustion products. While, the hydrogen injection pressure of 2.7 bar and an inclination of 60°, stimulate a better quality of hydrogen-air mixture. Afterwards, a comparison between combustion characteristics of the optimized hydrogen-diesel dual fuel mode and the baseline (diesel mode) was conducted. The result was, under dual fuel mode there is an increase in combustion characteristics and NOx emissions as well as a decrease in CO2 emissions. For further improvement of dual fuel mode, retarding diesel start of injection (DSOI) strategy was used.     

Co-pyrolysis of waste polypropylene and rice bran wax‒ production of biofuel and its characterization

The present study aims to investigate the interaction during co-pyrolysis of Polypropylene (PP) and Rice bran wax (RBW). Initial characterization of feedstock was found to be suitable to carry out further experimental sets. Further, the pyrolysis experiments of PP, RBW and different blends (1:1, 1:2, 1:3, 2:1 and 3:1) were carried out in a semi-batch reactor. As per TGA analysis the temperature range between 400 °C and 650 °C at a constant heating rate of 25 °C/min was determined. The maximum liquid yield of PP, RBW was approximately 76%, 86% at the temperature of 500 °C and 600 °C respectively. Whereas maximum liquid yield from co?pyrolysis was obtained at 1:3 blend i.e. 81% at 550 °C.GC?MS results inferred the highest percentage of hydrocarbon whereas 1:3 blends has lower oxygen containing groups than RBW in liquid products. FTIR data of all blends indicates higher range of alkyl and aromatic compounds. H1 NMR results also confirmed the higher compounds into aliphatic region than aromatics or heteroaromatics groups. Further, most of the fuel properties of 1:3 blend falls within the range of gasoline and diesel properties. Study was extended to know crystallization behaviour of fuel by DSC analysis from two consecutive heating and cooling cycles of ?50 to 60 °C and reversed till ?50 °C at 10 °C min ?1. Two peaks at ?24 °C and 26 °C were observed during heating cycle whereas single peak at 23 °C during cooling cycle. 1:3 blend residual char characterization was also included in the work. Unfortunately, the SEM and BET results inferred that the char was not highly porous.     

反井钻机在斜井施工中的应用

通过工程实践,将反井钻机施工技术成功应用到48°和60°斜井开挖施工中,证明反井钻机施工斜井工艺完全可以替代传统的人工反导井或爬罐斜井施工工艺,是一种高效、安全地施工工艺。同时反井钻机施工斜井多见于60°～90°,反井钻机施工技术在48°斜井的开挖施工中的成功应用．将反井钻机的应用范围扩大到48°～90°。