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Song G.-B.,Xian Jiaotong University | Cai X.-L.,Xian Jiaotong University | Gao S.-P.,Xian Jiaotong University | Suonan J.-L.,Xian Jiaotong University | Yang Z.-L.,Xinxiang Power Supply Company
Gaodianya Jishu/High Voltage Engineering | Year: 2011

The natural frequency signal of DC lines is more obvious than that of AC lines. Combining the system structure, it is found that the natural frequency of VSC-HVDC is related with line length. Theoretically, the natural frequency differential is zero for external fault and it is a huge value for the internal fault. Accordingly, a new pilot protection principle and its primary criterion for HVDC transmission line are proposed based on current spectrum analysis at both ends. For the dead zone at the midpoint of the line, a secondary criterion is proposed. At the same time, the system of VSC-HVDC is built in PSCAD and various faults are simulated. In the protection principle, only current information of both converters are used and synchronization is not needed for the transmission of natural frequency. The simulation results show that the protection principle can identify the faults reliably and rapidly in different conditions, and is not affected by the fault resistance. Source


Shi Y.,Henan Normal University | Wang M.,Henan Normal University | Shen M.,Xinxiang Power Supply Company
Journal of Petroleum Science and Engineering | Year: 2016

Measurement of oil-water flow parameters is of great importance in petroleum industry. Due to its complicated flow structure, it is still a challenging problem. This paper presents the use of a multi-electrode conductance sensor and a dual-plane electrical resistance tomography (ERT) sensor to measure phase fraction and velocity in a horizontal oil-water flow. A series of experiments is carried out on a two-phase flow loop using mineral white oil and tap water. Taking advantage of different conductivity values of two fluids, the estimation of phase fraction is obtained by conductance measurements. By correlating voltage fluctuation signals measured from upstream and downstream sensor, the velocity of oil-water flow is evaluated. The phase fraction and velocity measured from two techniques are compared. Experimental results show that the multi-electrode conductance sensor is more suitable to estimate phase fraction of oil-water mixture. For the velocity measurement, cross correlation velocity obtained with multi-electrode conductance sensor is more closer to the mixture velocity of oil-water mixture. © 2016 Elsevier B.V. Source


Wang H.,Wuhan University | Hu Z.,Wuhan University | Zhang Y.,Guangxi Electric Power Research Institute | Li C.,Wuhan University | And 2 more authors.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

This paper introduces a combination forecasting model which is based on ensemble empirical mode decomposition and least squares support vector machines(LSSVM) into forecasting short-term wind speed, in the view of excavating the nonstationarity and nonlinearity of wind series. Firstly, wind series are decomposed into a group of relatively stable subsequence by ensemble empirical mode decomposition to reduce mutual influences among diverse trend information. Secondly, build forecasting models respectively for each subsequence adopting least squares support vector machines. Adaptive disturbance particle swarm optimization and model learning feedback mechanism is used to jointly optimize the dimension of the learning sample input and the hyper parameters of LSSVM forecasting model to lower the predicting risk. Finally, the predicting results of each subsequence are superposed to obtain wind speed forecasting results. The case study shows that the proposed combination forecasting model is able to excavate wind series features effectively and has relatively high predicting accuracy. Source


Ke Z.,Xinxiang Power Supply Company
Applied Mechanics and Materials | Year: 2013

The smart grid is an ideal solution of the future electricity system, and scheduling aspects of the smart grid, the nerve center of the most intelligent can best embody the intelligent characteristic, this article summarizes the development of smart grid technologies, energy-saving scheduling, and the smart grid ofsignificance analysis to explore the implementation of energy-saving dispatch to the power industry, an energy efficient scheduling model and highlight the superiority of the energy-saving scheduling in order to ensure the smooth implementation of energy-saving scheduling. © (2013) Trans Tech Publications, Switzerland. Source


Du G.,Kaifeng Power Supply Company | Liu X.,Kaifeng Power Supply Company | Su G.-F.,Xinxiang Power Supply Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

Due to the large amount of branches and high grounding resistance of distribution grid, the single-phase-to-earth fault location has not been solved effectively. The single-phase-to-earth fault location technology is proposed by combining FTU and "S" signal injection method. Firstly, the zero-sequence voltage and zero-sequence current are measured by using line FTU so that the fault area is located. Then the "S" signal is injected, and the signal can be measured by electromagnetic induction theory so as to find the exact location of grounding fault. To avoid the influence of distributed capacitance to "S" injection signal, the calculation method of length of FTU isolation area is intensively studied. Moreover, the on-line location is possible by using this method. The correctness and feasibility of this technology have been fully proved by site experiments. Source

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