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Sima W.,Chongqing University | Wu P.,Chongqing University | Yuan T.,Chongqing University | Bai Y.,Chongqing University | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2016

In order to get an accurate soil structure, we put forward a method for solving the soil structure inverse problem by genetic algorithm (GA), in which the distinction produced by the experimental and theoretical curves of soil apparent resistivity is adopted to achieve an optimized soil structure. Compared with the present method which is used to solve the soil structure based on GA, first, the proposed method possesses advantages that we rationally set the initial precision of soil parameters, then the solution space is compressed, which makes the inverse problem of simple soil structure to directly converge to optimum in this precision; meanwhile, for the inverse problem of complex soil structure, the genetic-reckoning algorithm and variable precision method are introduced. So, during the estimation of soil structure, the solution space will be compressed into a certain scale and new individuals around the optimal solution will be introduced, which make the iteration process to more easily escape the local optimal solution, approaching the overall optimum. The calculation shows that the results of two-layer soil structure can coverage to overall optimum, the fitness value Fg=0 and for three-layer soil structure, the Fg calculated by the paper is smaller than simple GA; at the same time, the proposed method has a more stable output, the output difference is small in ten times repeated calculation. © 2016, High Voltage Engineering Editorial Department of CEPRI. All right reserved. Source


Hu Y.-Y.,University of Sichuan | Li X.-Y.,University of Sichuan | Li K.,University of Sichuan | Yang G.-Y.,China Southern Power Grid Maintenance & Test Center
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

Yunnan-Guangdong ±800 kV DC transmission project is the first UHVDC transmission project in the world. The DC power transmission system must supply emergency power when the load increases or AC system malfunctions at the receiving end. It requires the DC power system to overload operating to increase its transmission capacity. This paper mainly studies the overload capability of the converter valve. It proposes a theory of calculating the overload capability based on the junction temperature and cooling capability of the valve cooling system. Moreover, with the specific data, it calculates and analyzes the overload capability of converter valve in Chuxiong-Suidong DC transmission project. The result indicates that this arithmetic can get the accurate overload capability of converter valve, which can provide reference and guidance to the design and operation of the practical HVDC transmission project. ©, 2014, Power System Protection and Control Press. All right reserved. Source


Yang G.,China Southern Power Grid Maintenance & Test Center | Li X.,University of Sichuan | Hu Y.,Sichuan Electric Power Corporation | Li K.,University of Sichuan
Gaoya Dianqi/High Voltage Apparatus | Year: 2015

As one of the most important devices in the HVDC transmission system, the converter valve directly determines the reliability of the whole system. When the HVDC system has to operate in overload condition, the maximum current of the converter valve is defined as its overload capability to ensure the secure and reliable operation of the HVDC system. In this paper, the main factors affecting the overload capability of the converter valve are summarized, and a method for calculating overload capability of converter valve is proposed according to the thyristor junction temperature and the cooling capability of the valve cooling system. Moreover, the overload capability of the converter valve in the Anshun-Zhaoqing HVDC transmission project of the China Southern Power Grid is calculated with the roposed method. © 2015, Xi'an High Voltage Apparatus Research Institute. All right reserved. Source


Wu Q.-J.,China Southern Power Grid Maintenance & Test Center | Zhang N.,China Southern Power Grid Maintenance & Test Center | Zheng W.,China Southern Power Grid Maintenance & Test Center | Yang G.-Y.,China Southern Power Grid Maintenance & Test Center
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

When metallic return line occurs transient fault, DC protection system will not request fault restart in existing protection logic in Xing-An HVDC Project, which reduces the reliability of DC system. This paper proposes a metallic return line longitudinal differential protection (87MLL) at SIMADYN D platform. This protection acts as the main protection for metallic return line earth fault. This paper uses EMTDC model to simulate earth fault at different power, different fault location, different resistance monopolar metallic return operation. The result shows that the protection has misstrip risk when fault resistance is large, the arc can't extinguish during DC system restart when DC power is high. By comprehensively considering protection logic design scheme and EMTDC simulation result, we don't suggest to add 87MLL in Xing-An HVDC Project. Source


Wu Q.-J.,China Southern Power Grid Maintenance & Test Center | Zhou Q.,China Southern Power Grid Maintenance & Test Center | Huang Y.-L.,China Southern Power Grid Maintenance & Test Center | Yang G.-Y.,China Southern Power Grid Maintenance & Test Center
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

The feature of strong DC system and weak AC system in the CSPG becomes more obvious after Nuozhadu and Xiluodu HVDC system was put into operation. Transmission line fault, especially HVDC system block caused by lightning stroke fault impacts the safety and stability of power network for CSPG. This paper selects three typical lightning stroke fault which led to HVDC block in CSPG in 2013 to analyze response strategy of control and protection logic in different cases such as arc is not extinguished, dielectric strength is not restored, and transmission line is struck by lighting continuously. It points out the shortage of deionization time and the set time of fault counter. Finally, it suggests to avoid unnecessary HVDC system outage. Source

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