Time filter

Source Type

Shi X.,China Coal Technology and Engineering Co. | Wu K.,Hydro China Xibei Engineering Corporation
ICPTT 2014 - Proceedings of the 2014 International Conference on Pipelines and Trenchless Technology | Year: 2014

It is very important to detect underground pipes for urban planning, designing, constructing and managing. To know the distribution of underground pipes, GPR is available to provide real-time profile diagrams on the site which are clear and direct because of its high resolution, quick detecting and non-destructive feature. The radar is efficient especially when conventional methods fail to detect, and it is applicable to detect all kinds of metal and non-metal pipes. In this paper, the detecting principles, methods, techniques of the Radar had been introduced. In addition, the paper also analyzes and summarizes the features for underground pipes made from different materials shown on radar image profiles with application cases in order to prove its effectiveness. © 2014 American Society of Civil Engineers.

Shi X.,China Coal Technology and Engineering Co. | Wu K.,Hydro China Xibei Engineering Corporation
ICPTT 2014 - Proceedings of the 2014 International Conference on Pipelines and Trenchless Technology | Year: 2014

In this paper, principles, approaches and techniques of electromagnetic method applied to detect underground pipes are introduced; distributions and features of horizontal and vertical components Hx and Hz of geomagnetic field generated by direct coupling are analyzed theoretically and technical requirements of Frequency Domain EM in catering to detect underground pipes are summarized with the application effects elaborated through an application case in the end. © 2014 American Society of Civil Engineers.

Liu W.,Guangdong Tianlian Group Co. | Shen H.,Henan Institute of Science and Technology | Gao L.-G.,Hydrochina Xibei Engineering Corporation | Rong H.-Z.,Guangdong Tianlian Group Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

A control method based on direct torque control of brushless doubly-fed wind generation system is presented. A model which includes wind turbine, gear-box, and brushless doubly-fed machines for this system is set up. As wind change, by means of controlling the electromagnetic torque of brushless doubly-fed machines, the best tip speed ratio of wind turbine is realized, and eventually the generating operation mode with maximal wind energy capture comes true.

Lian J.-J.,Tianjin University | Zhang Y.,Tianjin University | Liu F.,Tianjin University | Yu X.-H.,HydroChina Xibei Engineering Corporation
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2013

Vibration source compositions and their effects on powerhouse were investigated for a roof overflow hydropower station with a bulb tubular unit. Based on the theoretical analysis and prototype observation data, powerhouse structure vibration frequencies excited by the unit operation and flow discharge were identified, and dynamic load sources were determined. Furthermore, the contributions (%) of different frequencies were calculated when the vibrations of the main measured points reached the maximum values. The contributions of the measured frequency bands energy to whole vibration response were also examined. The change laws of different frequency vibrations versus the load were presented. The results showed that the slot jet impingement, the vibration of the runner blade and the vibration due to the incorrect connection relationship are the main vibration sources; the powerhouse vibration induced by flow discharge is small, and it has no effect on the powerhouse structure's operation and safety. The results provided a basis for evaluating this model hydropower station's powerhouse vibration with a certain level.

Jia R.,Xi'an University of Technology | Zhang Y.,Hydro China Xibei Engineering Corporation | Hong G.,Guangxi Power Grid Beihai Power Supply Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

An intelligent method for fault diagnosis of transformer based on least squares support vector machine(LSSVM) is proposed. In order to improve the accuracy of fault diagnosis, the improved particle swarm optimization(IPSO) algorithm is adopted to optimize the parameters of LSSVM algorithm. The improved IPSO algorithm can adjust the balance between global and local search capabilities suitably. Experiment results prove that the method not only gets good classification results, but also achieves higher diagnostic accuracy than normal LSSVM and BP neural network. Consequently, the IPSO-LSSVM model is proper in fault diagnosis of transformer.

Wang T.,Lanzhou University | Wang T.,Hydro China Xibei Engineering Corporation | Wang T.,Chinese Academy of Sciences | Zhang M.,Hydro China Xibei Engineering Corporation | And 2 more authors.
Journal of Applied Geophysics | Year: 2012

The Hilbert-Huang transform (HHT) is a novel signal analysis method in seismic exploration. It integrates empirical mode decomposition (EMD) and classical Hilbert transform (HT), which can express the intrinsic essence using simple and understandable algorithm. But there is a serious mode mixing phenomenon in EMD. To solve the mode mixing problem, a noise-assisted data analysis method called ensemble empirical mode decomposition (EEMD) is adopted instead of EMD. In this paper, the applications of EMD and EEMD on time-frequency analyzing behaviors were compared, and the results show that (1) EMD decomposes an original nonlinear and non-stationary signal into a series of simple intrinsic mode functions (IMFs), but with the mode mixing phenomenon. (2) EEMD skillfully solves the mode mixing problem by adding a white noise to the original signal. (3) The synthetic signal example reveals the remarkable ability of EEMD to decompose the signal into different IMFs and analyze the time-frequency distribution of the signal. (4) The time-frequency spectrum obtained by EEMD more realistically reflects the real geology than by EMD. © 2012 Elsevier B.V.

Li X.,Xi'an Jiaotong University | Li Z.,China Electric Power Research Institute | Zhang Q.,Xi'an Jiaotong University | Li J.,Hydro China Xibei Engineering Corporation
Gaodianya Jishu/High Voltage Engineering | Year: 2013

Spark resistance is a key parameter influencing the life and efficiency of switch delivering power. In order to measure spark resistance accurately, we proposed a method that obtained spark resistance of gas gap through optical analysis. Firstly, we used a spectrograph to measure the emission spectrum of spark discharge under a high voltage pulse. Based on the emission spectrum, the time-dependent electron temperature and density in different locations of the discharge channel were calculated; meanwhile, the conductivity of the spark channel in different stages of discharge was calculated in accordance with an improved formula raised by Spitzer. Then, through radial images of the spark channel taken by the spectrograph, we measured the length of spectrum to calculate the diameter of the spark channel. Using the conductivity and the diameter, we obtained the resistance of spark channel. The results showed that the conductivity increased rapidly at first and then decreased slowly till it kept at about 104 S/m; meanwhile, the spark resistance decreased sharply from insulation state to about 0.1 Ω and then kept steady. The steady values fitted well with those calculated by former empirical formulae. It is concluded that, as the current increases, the conductivity of spark channel keeps unchanged. The increase of spark radius will result in the decrease of spark resistance; meanwhile, the increasing pressure and decreasing electron temperature of spark channel will lead to the decrease of conductivity and the increase of spark resistance.

Li J.,Xi'an University of Architecture and Technology | Liu N.,HydroCHINA Xibei Engineering Corporation
Advanced Materials Research | Year: 2012

Chinese vernacular residence is a unique type of architecture which evolved through time under the special geographical conditions. From the beginning of the traditional residence, it has been constructed using natural materials, forming a set of mature construction methodology with natural material. The article analyzed and reflected on the traditional building material in west China. The construction of traditional villages and residence are taken as object of study to explore the building strategy of constructing vernacular village houses. Efforts have been made to establish a conversational relation between tradition and present world and also to propel the process of renewing the vernacular architectures rationally. Moreover, references can be provided to rebuild regional culture in vast rural area in China, and the sustainable development and creation of vernacular architecture. © (2012) Trans Tech Publications, Switzerland.

Song Y.,Chang'an University | Ju G.,HydroChina Xibei Engineering Corporation
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

Approach of determining shear strength of rock mass at present is briefly reviewed. Taking Maerdang hydropower station located in the upstream of the Yellow River for example, the relationship between shear strength and BQ rating is built up on the basis of rock mass classification, suggested shear strength by codes and in-situ large scale shearing test; and the relationship between BQ rating and GSI is also created according to field survey and measurement. Based on these, shear strength of rock mass at in-situ test point is estimated by Hoek-Brown criterion. The result shows that rock mass shear strength derived from this paper's method is coincident with practical situation; while equivalent fraction coefficient from Hoek-Brown criterion is lower than test value and cohesion force is far greater than that from shearing test. It is shown by error analysis that the difference between experiment values and estimated ones is mostly induced by the span of minimum principal stress used in Hoek-Brown criterion. For this situation, some cautions and corresponding resolve methods while using Hoek-Brown criterion are reminded.

Wang X.X.,China Three Gorges University | Deng C.J.,HydroChina Xibei Engineering Corporation
Advanced Materials Research | Year: 2014

Excavation unloading zone corresponds to stress decreased area of slope rock mass after excavation. Quality of slope rock mass in this area will be degraded due to excavation disturbance, and the mechanical parameters of rock mass will be also degraded accordingly. Therefore, determining the range of excavation unloading zone accurately is one of the key factors to ensure the rationality and validity of numerical simulation results of rock slope excavation. In this paper, the range of excavation unloading zone is determined by comparing stress field before and after excavation, choosing stress component perpendicular to excavation face as comparative standard in calculation, which can be calculated by computer program with FLAC software. Stress adjustment of slope rock mass due to excavation is a dynamic and changing progress, so the range of excavation unloading zone is changing during excavation, which can be achieved by a cycling program in numerical simulation. The correctness and usefulness of this method is proved by the calculation results of example analysis. © (2014) Trans Tech Publications, Switzerland.

Loading Hydrochina XIBEI Engineering Corporation collaborators
Loading Hydrochina XIBEI Engineering Corporation collaborators