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.     

SPWM逆变器过压保护电路的研究

本针对SPWM逆变器工作中的安全性问题，阐述了如何利用电路实现过压保护。     

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.     

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…     

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.     

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。     

合理应用消雷器降低线路跳闸率

本文分析了220KV朱陈线安装消雷器后,线路跳闸率的降低,肯定了使用消雷器后取得的防雷效果,并简述了消雷器保护范围及经济分析.