Study on shift schedule saving energy of automatic transmission of ground vehicles

INTRODUCTION The technology of automatic transmission inthe automobile is widely applied in the groundvehicle to increase productivity and decrease in-tensity of labor. However, the performance of theground vehicle in various operating conditions,such as low speed, heavy load and sharply changingload, is very different from that of the automobile innormal operation. Therefore, the ground vehiclecannot adopt the method of the lock-up clutch usedin the automobile to solve the problem o…     

Study on shift schedule saving energy of automatic transmission of ground vehicles

To improve ground vehicle efficiency,shift schedule energy saving was proposed for the ground vehicle automatic transmission by studying the function of the torque converter and transmission in the vehicular drivetrain.The shift schedule can keep the torque converter working in the high efficiency range under all the working conditions except in the low efficiency range on the left when the transmission worked at the lowest shift,and in the low efficiency range on the right when the transmission worked at the highest shift.The shift quality key factors were analysed.The automatic transmission's bench-test adopting this shift schedule was made on the automatic transmission's test-bed.The experimental results showed that the shift schedule was correct and that the shift quality was controllable.     

Wind-induced vibration control of long-span power transmission towers

We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.     

Modern travelling wave based fault location techniques for HVDC transmission lines

The modern travelling wave based fault location principles for transmission lines are ana-lyzed. In order to apply the travelling wave principles to HVDC transmission lines, the special tech-nical problems are studied. Based on this, a fault locating system for HVDC transmission lines is developed. The system can support modern double ended and single ended travelling wave princi-ples simultaneously, and it is composed of three different parts: travelling wave data acquisition and processing system, communication network and PC based master station. In the system, the fault generated transients are induced from the ground leads of the over-voltage suppression ca-pacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 Kv Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China. Some field op- eration experiences are summarized, showing that the system has very high reliability and accu- racy,and the maximum location error is about 3 km(not more than 0.3% of the total line length). Obviously, the application of the system is successful, and the fault location problem has finally been solved completely since the line operation.     

Aeolian vibration control measures for ground wires of Han River long span transmission lines

Long span ultra-high voltage （UHV） transmission lines have serious aeolian vibration problems. To control these vibrations, we improved the energy balance method in the following aspects： the wind power input, the conductor self-damping, and the damper dissipated power. Meanwhile, we built a theoretical mechanical model of β wire dampers and derived energy dissipation calculation formulae. This permits the vibration energy dissipated by β wire dampers can be considered in the energy balance method. Then, we developed a computer program based on the improved energy balance method using Matlab, and analyzed UHV long span ground wires of the Han River long span project in P. R. China. The results show that the combination of β wire dampers and Stockbridge dampers can reduce vibration of UHV long span transmission lines, which provides a reference for research and construction of UHV engineering projects.     

钢管输电铁塔插板节点受拉极限承载力分析

大型输电铁塔广泛应用钢管节点,为了简化制作安装,避免复杂的相贯线切割,塔身斜材与主材的连接经常将钢管开长槽孔和插入的钢板焊接.由于钢管截面只是部分和钢板连接,在拉力作用下,管板节点易发生剪切滞后破坏.为研究剪切滞后对管板节点受拉极限承载力的影响,进行了一系列分析,并将研究结果和现行设计规范公式进行了比较.     

利用转速图判断机床传动机构故障

介绍了如何利用转速图判断机床传动机构的故障,确定故障位置,避免盲目维修。     

DC steady-states analysis of lossy uniform transmission lines

1 Introduction In the past 20 years with the rapid development of VLSI (very large scale integration) circuits and continual spread of electric power system scale, theories on transmission lines have become an important research field where finding the analytic solutions to lossy transmission line equations remains a tough nut. Since the mathematical tool cannot provide effective help, there is no universal method to solve transmission line equations [1]. A number of researchers have obtaine…     

Overvoltage suppression for UHV transmission lines

The overvoltage phenomena of ultra high voltage (UHV) transmission lines are analyzed and verified by EMTDC/PSCAD simulation. Referring to the theoretical analyses and operating experiences of extra high voltage (EHV) transmission lines in China and UHV transmission lines in Russia and Japan, the methods to suppress the internal overvoltage in UHV transmission lines by protection and control strategies are discussed. Through the cooperation among the recloser, shunt reactor, tripping and closing resistance, and metal oxide varistor (MOV), the overvoltage can be restrained within an acceptable level.     

基于OrCAD/PSpice 15.7的无损均匀线实验研究与实践

针对无损均匀线理论教学及传统实验存在的问题,提出运用OrCAD/PSpice 15.7进行无损均匀线仿真实验研究的实验教学方法。正确设置PSpice中无损均匀线的模型参数值,可分析无损均匀线的时域特性、频域特性,并对正弦交流工作下沿线各点的电压和电流值进行仿真。     

评价机构传动质量的新方法-当量压力角法

对压力角和传动角作为衡量机构传动质量的不足进行了分析,提出采用当量压力角的合理性与实际意义.     

Effects of un-transposed UHV transmission line on fault analysis of power systems

The conventional fault analysis method based on symmetrical components supposes that the three-phase parameters of un-transposed transmission line are symmetrical in case of fault. The errors caused by the method with the symmetrical distributed parameter circuit model as the equivalent circuit of the un-transposed ultra high voltage (UHV) transmission line were studied under both normal operation and fault, and the corresponding problems arising were pointed out. By contrast with electromagnetic transient and power electronics (EMTPE) simulation results with the asymmetrical distributed parameter circuit model of un-transposed line, it is shown that the conventional method cannot show the existence of negative and zero sequences before fault happening and there are many errors on voltage and current after fault happening which are different with fault types. The error ranges of voltage and current are 2.13%-81.13% and -7.82%-86.15%, respectively.     

Single-phase earth fault current distribution between optical fiber composite overhead ground wire and ordinary ground wire in transmission system

It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution. Features of double sided elimination method were illustrated. Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method. Influences of some factors, such as single-phase earth fault location and ground resistance of poles, on short-circuit current distribution were discussed. Results show that: 1) results of the loop method conform to those of double sided elimination method; 2) the fault location hardly influences macro-distribution of short-circuit current. However, current near fault location is evidently influenced; and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.