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1.
Ice shedding on transmission lines results in longitudinal unbalanced forces on adjacent transmission towers,which significantly threaten the safety of transmission lines.The methodology of ice shedding simulation on transmission lines is developed by using the finite element method and validated by comparing the simulation results with those obtained from the model scale experiments done by previous researchers.The responses of the tower line system induced by simultaneous ice shedding on the conductor and ground wire are analyzed.The developed methodology is then applied to study ice shedding considering unzipping effect,in which the influence of the velocity of ice shedding on the responses is investigated.Results from this study show that the longitudinal unbalanced forces induced by simultaneous ice shedding from the ground wire are greater than those from the conductor under similar condition.During the analysis of ice shedding considering unzipping effect,the slower the velocity of ice shedding is,the closer the responses are to those resulting from static unloading;and the faster the velocity of ice shedding is,the closer the responses are to those resulting from simultaneous ice shedding. 相似文献
2.
Numerical models of typical 500 kV ultra high voltage (UHV) transmission lines are set up in ABAQUS/CAE software. The dynamic response of the transmission lines with different structure parameters under various ice shedding load cases are analyzed, and th 相似文献
3.
In order to accurately calculate corona loss from the bare bundled conductors of HVDC transmission lines, considering the uneven distribution of sub-surface electric field caused by interactions between the sub-conductor, different corona onset voltage and corona loss differences in different positions as sub-conductor, the authors propose a more accurate method of calculating of bipolar corona loss from the bare bundled conductors of HVDC transmission lines by analyzing mechanism under the corona, according to the condition of gas self-sustaining discharge to decide corona onset voltag. The method is applied to the synthetic electric field of ±800 kV to verify its effectiveness. The results show that the corona loss is the most serious outside of sub-surface distribution of wire round and lighter inside even without any corona loss. Each pole’s losses are mainly concentrated in three sub-lines inside of the wire. Finally, analysis the affection of ± 800 kV line parameters on corona loss. The results show that sub-conductor radius and pole pitch have obviously impact on the corona loss and they are the main factors. They should be given priority in engineering design. 相似文献
4.
Drag coefficients of quad-bundled conductor under different wind speeds and attack angles are firstly determined by means of wind tunnel test. Meanwhile, the drag coefficients are obtained by numerical simulation method and the results are consistent with those by the wind tunnel test. Furthermore, cross flows around six-bundled and eight-bundled conductors are numerically investigated, and the drag coefficients are then determined. Compared with the determination method of wind load on conductor in current Chinese code and the IEC code for the design of transmission line, the drag coefficients defined in the Chinese code may be too large for bundled conductors, and may need to be adjusted based on further theoretical and wind tunnel test investigation. 相似文献
5.
The AC flashover performance of 110 kV iced potential transformer is investigated by testing in laboratory to analyze the influence degree of icing on the safe and reliable operation of power system. The results show that the AC flashover voltage of 110 kV iced potential transformer decreases with the ice amount increasing. The relation between icing flashover voltage and ice amount accords with the negative exponential function law, and the characteristic index is in the range of 0.085～0.100. Meanwhile, the relation between icing flashover voltage and ice thickness accords with the negative power function law, and the characteristic index is in the range of 0.40～0.55. The flashover voltage of 110 kV iced bushing is related to the pollution before icing. The relation between icing flashover voltage and salt deposit density (SDD) accords with the negative power function law, and the characteristic index is in the range of 0.21～0.26. When the ice thickness is up to 25 mm and SDD is 0.08 mg/cm2 and above, the icing flashover occurs on the 110 kV potential transformer in service. The effective measures to prevent AC icing flashover of 110 kV potential transformer are to increase the height of the structure and install creepage extenders. The results can offer consults for the external insulation selection and design of substation in ice covered regions. 相似文献
6.
Nominal electric field calculation at the ground level of UHV DC transmission lines based on radial basis function method 
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下载免费PDF全文 Nominal electric field at ground level is one of the important factors for the design of transmission lines. FEM meets two big challenges in electromagnetic field computation. One comes from the mesh generation, which is a big difficulty especially in complex geometry. The other is the long time calculation. So the radial basis function method is introduced to calculate the nominal electric field at the ground level of UHVDC transmission lines. Not only the definition and ideas, but also the detailed implementation procedure of radial basis function method are presented. Computer programs are developed to simulate the model and the influences of conductor configuration on nominal electric field intensity are analyzed. Examples of calculation show that the results are accorded with those available literatures, and agreed satisfactorily with analytic solutions of the coaxial cable model. The height of the polar lines and conductor inter-spacing has a remarkable influence on ground nominal electric field intensity while the sub-conductor radius and number of sub-conductors have little influence. 相似文献
7.
Analysis of the distorted scaling factor in wind tunnel modeling of power transmission line system
Because of the limitation of the model making and the existing wind tunnel’s size, it is difficult to keep the line and tower in the same scaling factor in developing the aeroelastic model of the power transmission lines system, and a distorted scaling factor is needed in span length of the lines. With the instance of a 1 000 kV two circuit power transmission lines, the finite element analysis under the along wind load in time history is conducted with keeping the tower in the same and the line scaling factor being 1, 0.5 and 0.25 respectively. The results show that the response of the power transmission lines systems keep in the same, and then the wind induced vibration of the distorted model in the wind tunnel test can actually reflect the response of the power transmission lines system under the wind load. 相似文献
8.
Yangtianqing tailings dam is a new dam planned for a copper mine. At the design period, test in laboratory is carried out to simulate the process of dam pile based on the design information of Yangtianqing tailings dam. And the regularity of the saturation lines’ change at the condition of flood and normal is studied, when the dam have been heaped to the about 2/3 of the total height (120 m). Based on the test data, the stability coefficients of the dam at this height in different conditions are obtained with the Slide software, and they could be served for the following test and the mine’s future safety production. It is shown that the dam is safe in the normal condition, while in the condition of flood, the stability coefficient is less than the benchmark in national standard. Thus, it is necessary to rectify the preliminary design or to take other measures to ensure the safety of the tailings dam. 相似文献
9.
Vehicle exhaust,dust and grease in tunnels are hard to be degraded,thus there will be more and more pollutants and the traffic safety will be influenced. Therefore,regularly cleaning tunnels is important for guaranteeing the traffic safety in tunnels. A tunnel cleaning method with dry ice is proposed,and a model of dry ice cleaning tunnel is developed based on the physical,chemical and cleaning properties of dry ice. Some experiments about the surface hole,surface temperature and the uniaxial compressive strength of the concrete are conducted. The surface damage and the compressive strength of the concrete is researched after the cleaning process. The test results show that：the dry ice cleaning method can thoroughly clean the surface of concrete;the surface damage and the compressive strength is little influence by the temperature and dry ice micro blasting. So dry ice cleaning method can be used for cleaning tunnel. 相似文献
10.
Based on the concept and characteristics of disaster resilience, technical robustness and organizational robustness were discussed by updating trunk lines of urban water supply system for two different earthquake magnitudes, M 6.5 and M 7.0 respectively, where lifeline earthquake loss model was taken as a starting point. Monte Carlo based GIRAFFE model was adopted in this research. Result shows that retrofit of trunk lines is helpful for both technical robustness and organizational robustness, and the updating effect would become more significant as the earthquake magnitude increases. Furthermore, criticalness of pipelines is not determined by the earthquake magnitude, but as time goes it depends on their respective locations in the system and system configuration. At the moment instantly after earthquake, the pipelines which are located at the center of system would be more critical; while 24 hours later, the pipelines which are closer to the reservoir will become more critical. 相似文献
11.
Based on the structure of cost factor in transmission lines project and the characteristic of neural networks, the paper shows up using artificial neural networks to estimate the cost of project and provide a method to investigate them. By analyzing the structure of project cost and influence factor, the paper builds both input and output neural cell for cost of transmission line project. The paper builds the model of artificial neural networks and exports the steps of the algorithmic. The project sample is used in history to train and test the model. At last, the model gets satisfactory result and meets the investigation requirement of engineering budgetary estimation. Therefore, the paper provides an impersonality and quick investigation method for budgetary estimation of power projects. 相似文献
12.
The radiation field created by the transmission line stroked by lightning far from the lightning channel has been analyzed by the FDTD method.The authors we establish the calculation model and FDTD calculation method of transmission line,and discusses the import of lightning excitation source.The simulation of lightning stroked on a single transmission line in free space or stroked on three-phase high voltage transmission lines in actual environments has been done,and gives the distribution of transient radiation field around the transmission lines when lightning overvoltage wave transmits along the transmission line.The simulation result shows that: the effect of the transient radiation field caused by lightning over voltage wave done with environment is obvious,and the high frequency component of transient radiation field may disturb or do harm to the electronic facility or communication facility around the transmission lines. 相似文献
13.
Frost heave has caused serious distresses to railway roadbeds in seasonal, especially deep seasonal, frozen regions. Therefore, frost heave prevention is the basic principle of roadbed design in seasonal frozen regions for many years. Frost heave has caused serious distresses to railway roadbeds in seasonal, especially deep seasonal, frozen regions. Therefore, frost heave prevention is the basic principle of roadbed design in seasonal frozen regions. The coupled heat fluid transport equation and two dimensional finite element method were employed to simulate the maximum frozen depth in the coming 50 years under the roadbed with XPS insulation board in the conditions of different depth, width, thickness and construction season for studying the insulation effect. Based on numerical simulation, appropriate depth, width and construction season were proposed for insulation design and the relationship between the thickness of insulation board and the height of roadbed was analysed as well. 相似文献
14.
Power Lines Icing Characteristics of the Three Gorges District and a Model of the Accumulation of Ice on Electric on Electric Power Lines 总被引：2，自引：0，他引：2
Jiang Xingliang Sun Caixin Gu Leguan Lu Chonghui 《保鲜与加工》1998,(2):16-19
Based on the study of accidents investigation of the electrical power lines because of icing in the district of Three Gorges,this paper analyzes the icing conditions and characteristics of various ice accreted and develops a model of the accumution of hard rime on electrical lines. 相似文献
15.
Through study of the rule of the air current between the metro stations which had installed the safety door system and the tunnel, this text established a physics model and a mathematics model, gained the mix coefficient which can marks the degree of the influence stopcock wind in metro inflict to the heat environment, exerting reasonable assumption and simplification, making use of the CFD imitation, adopting tracer air. The text elected three kinds of safety door system with different height to simulate and compare, gained the exact value of the mix coefficient, and simulated the energy consumption of subway air conditioning in different height of safety door by the mix coefficient. 相似文献
16.
There is no universal method of finding the analytic solutions to transmission lines discribed by partial differential equations,so many researchers are studying and developing transmission line theories.Computing steady-state solutions of uniform transmission lines is one part of the study.The paper introduces another method of computing sinsoidal steady-state solutions of lossy uniform transmission lines.First,the complex expressions of voltage and current with zero initial state are obtained from the complex frequency-domain model of lossy uniform tansmission lines.The network functions,which are the ratios of voltage and current's image functions to the excitation's image function,can be found from the complex expressions.Sinusoidal steady-state solutions can be obtained by using the relation between network function and system's frequency characteristic.Finally,the method is demonstrated to be effective by an example. 相似文献
17.
Framework design of multimedia data parallel management in the informatization of rural areas 下载免费PDF全文
下载免费PDF全文 In order to realize the efficient transmission and analysis of multimedia data under TD-SCDMA network, a parallel management framework is proposed. This framework improves the general framework for data management by parallelizing the generation of standardized data and the analysis of original data. It not only reduces the data volume in transmission and analysis, but also fits for parallel optimization. Focusing on image analysis in the informatization of rural areas, the authors introduce the procedures to realize the parallel management framework. As can be seen from experiment results, the data volume of image data is reduced to 1/12 after parallel optimization, and the time cost of analysis is substantially reduced. Thus, it can effectively relax the requirement of the TD-WCDMA transmission bandwidth for multimedia application in the informatization of rural areas. 相似文献
18.
In order to calculate and analyze the effect of two transmission lines in parallel on the reliability evaluation of bulk power system, a model including independent outage, common mode outage and dependent outage of these lines is deduced and a new algorithm corresponding to the model is presented. Two transmission lines in parallel including common mode outages and dependent outages can be really simulated as a multi-state component. While reliability indices are calculated, the probability and frequency of independent outage, common mode outage and dependent outage of a system failure state can be calculated at the same time, and computation complexity is reduced. The proposed model and algorithm are applied to the RBTS system, IEEE One Area RTS96 system and a real power system for reliability computation and analysis. Results show that the new algorithm is credible and validity. 相似文献
19.
When contactless power transmission (CPT) systems are operating normally, load variation will cause the system operating frequency to drift and the resonance frequency scope to deviate from the desired level. These fluctuations in turn cause the system to vary substantially and affect its normal operation. Considering the slip road track of the primary circuit and the phase angle change between the front of the sub network rectifier circuit current and the voltage, we employ different circuit models to analyze the nature and size of the load for the two types of anti perceptual situations. An algorithm is derived to calculate the junior circuit parameters with the load on the rails. Simulation analysis for the load identification under two different load conditions is conducted, and the expected results achieved. 相似文献
20.
The dynamic balance equation of the system is set up by means of the Hamilton variational principles with the constraint conditions of the clamp points of spacers in the sub conductors by the penalty function. The numerical simulation for galloping of twin bundle conductors is achieved with the time integral by Newmark method and the Newton Raphson iteration solution for nonlinear equation. The validity is approved with simulation for the galloping of horizontal and vertical icing twin bundle conductor. The difference of aerodynamic loads, which is due to the impacts of wake flow of windward sub conductor on lee sub conductor, on the individual sub conductors can be considered with the proposed approach. It is appropriate for further study in the field of bundle conductor galloping. 相似文献