Journal articles on the topic 'Equivalent operation line'
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1
Dong, Yuan Yuan, Fei Wang, Yong Gang Lei, and Guo Wei Wang. "Equivalent Stress Cycles Based on District Heating Operation." Applied Mechanics and Materials 713-715 (January 2015): 295–99. http://dx.doi.org/10.4028/www.scientific.net/amm.713-715.295.
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We investigated supply water temperature of the district boiler between 2006 and 2014.And calculated the design life cycles of heating pipeline based on the district boiler as the heat source. Then superposed the number of the design life cycles caused by pipelines accidents and district boiler of the main trunk lines, distribution lines and subscriber connection line, we obtained the design life cycles of different heating pipes. This result can provide a basis for fatigue damage analysis of heating pipe fittings.
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Pană, Adrian, Alexandru Băloi, and Florin Molnar-Matei. "Mathematical Explanations of a Paradox Observed in a HVAC (High Voltage Alternating Current) Untransposed Overhead Line." Energies 12, no. 4 (February 22, 2019): 734. http://dx.doi.org/10.3390/en12040734.
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The constructive asymmetry of the untransposed overhead lines of a high voltage alternating current is the cause of a great number of difficulties in their operation and modeling. In order to model the operating regimes of such lines, the symmetrical component method, based on constructive symmetry and thus the symmetry of the equivalent phase parameters, is inappropriate, which is why many research papers have been dedicated to either setting up improved modeling methods or to returning to phase coordinate modeling. This paper intends to justify a paradox found on some untransposed overhead lines of a high voltage alternating current during the no-load operating conditions by performing phase coordinate modeling. In such a situation, the transmission or distribution operators measured significant negative values for the active powers on one or two phases at the beginning of the lines. Considering the case of a real untransposed overhead line operating under no-load conditions, the paper starts from presenting the recorded electrical values. Then, the paper moves on to outlining the Carson’s simplified computing relations for calculating the series and shunt primitive equivalent parameters and Kron’s transformation relationships for calculating the phase equivalent parameters. After applying them to the real line, the calculation of the power flow for the no-load operating conditions, which is applied to an equivalent scheme of the line consisting of nine identical octopoles, is performed. Both the untransposed line and its transposed variant are studied here. The values of the electrical amounts obtained by the calculation for the untransposed line are basically similar to those obtained by measuring on the real line, which gives a mathematical confirmation of the so-called paradox. Its occurrence represents the effect of the asymmetry of the equivalent phase capacities, which causes a redistribution of the active powers between the phases of the network to which the overhead line operating in no-load conditions is connected.
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Doberkat, Ernst-Erich. "A stochastic interpretation of propositional dynamic logic: expressivity." Journal of Symbolic Logic 77, no. 2 (June 2012): 687–716. http://dx.doi.org/10.2178/jsl/1333566646.
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AbstractWe propose a probabilistic interpretation of Propositional Dynamic Logic (PDL). We show that logical and behavioral equivalence are equivalent over general measurable spaces. This is done first for the fragment of straight line programs and then extended to cater for the nondeterministic nature of choice and iteration, expanded to PDL as a whole. Bisimilarity is also discussed and shown to be equivalent to logical and behavioral equivalence, provided the base spaces are Polish spaces. We adapt techniques from coalgebraic stochastic logic and point out some connections to Souslin's operation from descriptive set theory. This leads to a discussion of complete stochastic Kripke models and model completion, which permits an adequate treatment of the test operator.
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Xu, Zai De, Guo Cheng Sun, Ben Ren Pan, Ning Xu, Chao Qun Li, and Hong Zhong Ma. "An Equivalent Modeling for Synthesis Load of Distributed Network with Small Hydropower." Applied Mechanics and Materials 666 (October 2014): 119–24. http://dx.doi.org/10.4028/www.scientific.net/amm.666.119.
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A distributed network with small hydropower is taken as research subject, and in PSASP environment a simulation network is constructed, which is based on the network’s connection mode and operation data. At first, this paper give a description of 3rd mode of small hydropower generator, and generalize common analysis methods of synthesis load, and on this basis lists three means that used for aggregating parameters, then choose weighted average method to aggregate necessary parameters of Small hydropower generators. Secondly, the operation data is fully used to determine the equivalent impedance of the network. Finally, in order to verify the accuracy and feasibility of the method raised by the paper, the author make a comparison of small hydropower generators’ relative rocking curve before and after equivalence, meanwhile, analyzes change regulation of active power in contact line before and after the equivalence.
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Xian, Wenyuan, Ran Ding, Ying Qiao, Zongxiang Lu, Shangqiang Li, and Hong Lin. "Steady-state Operation Area of VSC-HVDC Converter Station Connecting Renewable Energy Cluster by Isolated Network." E3S Web of Conferences 182 (2020): 02003. http://dx.doi.org/10.1051/e3sconf/202018202003.
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When the large-scale renewable power island is connected to VSC-HVDC transmission system, we should figure out the steady-state operation area of VSC-HVDC converter station. Based on the equivalent model of renewable energy island, the constraints of VSC-HVDC converter station are analyzed, and a fast method for calculating steady-state operation area of converter station is presented in this paper. The influence of equivalent line impedance of renewable energy island, transformer ratio of converter station and voltage setting value of grid-connected point on steady-state operation area of converter station is analyzed. And the three-dimensional view of the steady-state operation area of the converter station under different grid-connected voltage is depicted.
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Adak, M., and N. R. Mandal. "Thermomechanical analysis through a pseudolinear equivalent constant stiffness system." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 217, no. 1 (March 1, 2003): 1–9. http://dx.doi.org/10.1243/147509003321623103.
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A non-uniform heating and cooling cycle caused by a welding or line heating operation leads to deformation. To ascertain the extent of deformation calls for solving a complex thermal elastoplastic problem. In this investigation the concept of a pseudolinear constant stiffness system has been effectively implemented to solve this non-linear problem. The concept has been tested by solving a case of angular deformation of a beam model caused by bead-on-plate welding. The theoretical results compared well with those of the experimental ones.
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Lian, Shuai, Bintang Li, Jianbo Wang, and Rui Jiang. "On-line Update Method for the Sensitivity Consistency Model of Interconnected Power Grid Based on Electric Power Big Data." E3S Web of Conferences 256 (2021): 01014. http://dx.doi.org/10.1051/e3sconf/202125601014.
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Real-time fast calculation of the power flow of the interconnected power grid is an important guarantee for the reliable operation of the interconnected power grid. The topology of the interconnected power grid is complex, and the calculation of the power flow of the whole network is large and timeconsuming. The sensitivity equivalent model can effectively simplify the interconnected power grid and shorten the time of the power flow calculation of the whole network. The operating state of the power grid is constantly changing. In order to ensure the accuracy of the power flow calculation results, it is necessary to update the uniform sensitivity equivalent model in real time. Due to factors such as the vertical management system between the interconnected power grids and the principle of commercial confidentiality, it is difficult to share information between interconnected power grids in real time, and the sensitivity equivalent model cannot be updated in real time, resulting in too much error in the calculation results and no reference value. To solve this problem, this paper proposes an online update method for the sensitivity equivalent model of the interconnected power grid based on power big data to solve the problem of excessive power flow calculation errors caused by the untimely update of the equivalent model parameters, and to ensure the operational reliability of the interconnected power grid.
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Yan, Gangui, Dan Wang, Qi Jia, and Wenbo Hu. "Equivalent Modeling of Dfig-Based Wind Farms for Sub-Synchronous Resonance Analysis." Energies 13, no. 20 (October 17, 2020): 5426. http://dx.doi.org/10.3390/en13205426.
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The order of the detailed model of doubly-fed induction generator (DFIG) wind farms are too high and the simulation is difficult. Most of the existing research has used a single-machine equivalent model and clustering aggregation model for equivalence and few papers have explored the principles and equivalent conditions of the single-machine equivalent model under sub-synchronous resonance (SSR). Due to this reason, this paper equates DFIG wind farms connected with series compensated transmission network to two separate units based on the principle of matrix similarity transformation and the mathematical model and physical model of each unit has been studied. Then, the DFIG wind farm equivalent model’s validity is analyzed in number difference and collecting line difference based on linearization analysis. Finally, the system model is built in EMTDC/PSCAD, the damping analysis method is used to test the equivalent model’s validity and further reveal the mechanism of the system’s unstable operation. The results show that: the equivalent model can effectively reduce the system dimension and accurately reflect the dominant oscillation characteristics of DFIG wind farm under SSR; when SSR occurs, the damping coefficient of DFIG wind farm is negative under the oscillation frequency.
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Gaevskii, A., V. Bodnyak, and A. Gaevskaya. "ANALYSIS OF MONITORING DATA ON THE OPERATION OF PV-INVERTERS CONNECTED TO DISTRIBUTION NETWORK." Alternative Energy and Ecology (ISJAEE), no. 31-36 (January 6, 2019): 12–22. http://dx.doi.org/10.15518/isjaee.2018.31-36.012-022.
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The article deals with the problems of the PV plants operation in the low voltage network (LVN), namely the influence of PV generation on bus voltages and stability of network, as well as disconnecting the inverters from network in order to avoid overvoltages. The operating of PV inverter tied to LVN is considered on the framework of the reduced two-bus equivalent circuit. One bus of this circuit describes the inverter which is connected to the step-up transformer via short line and second one is the equivalent representation of LVN. The reduced two-bus circuit in contrast to the multi-bus schemes has exact solutions for power flows between PV plant and network. The analytical solutions obtained for this model allows us to determine the voltage stability region, the disconnecting conditions from the network (islanding), the dependence of the bus voltages on the levels of generation and load. On the base of this model, the monitoring data for power and output voltages of three-phase Growatt 30 kW inverter were analyzed. The inverter is tied to LVN by a relatively short line segment with known parameters which is typical for private and small industrial photovoltaic systems. The stable operation of PV plant in the network depends on the ratio of generation and consumption levels at the bus on the plant side, as well as on the capacity of the connecting line. Under analyzing of an overvoltage in the inverter bus appearing due to large solar radiation, one should take into account the limited inverter’s possibility to reduce the output power by changing the operating point on the curve “voltagepower”. The article performs the optimization calculations which determine the parameters characterizing the inverter and line capacity. The developed method for analyzing monitoring data of modern inverters can be a useful tool in solving problems of PV plant equipment diagnostics, as well as of predicting the electricity amount supplied to the network.
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Liu, Gao, Li Hui Wu, Bao Qiang Liu, Hu Zhang, Jin Bei Zheng, and Hong Shen. "Optical Fiber Sensor Salt Dense On-Line Monitoring Research." Applied Mechanics and Materials 325-326 (June 2013): 708–11. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.708.
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To detect the pollution level of insulators in operation, based on light energy loss theory of medium optical wave guide and mathematical modeling of least squares supporting vector machine, by a lot of contrast tests, this paper designed and developed monitoring terminal of optical sensor. Collecting live temperature, humidity luminous flux attenuation etc. and sending the collected data to data monitoring centre through GSM data communication module, the workstation of data monitoring centre could calculate to get equivalent salt deposit density (ESDD) using mathematical model, so that insulators pollution level can be detected on-line automatically and continuously.
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Minnegaliev, Aleksandr, Ruslan Rakhimov, Ruslan Suleimanov, and Mansur Gainanshin. "Snow-pillow: creation experience and prototype operation." E3S Web of Conferences 163 (2020): 05009. http://dx.doi.org/10.1051/e3sconf/202016305009.
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A snow-pillow (or snow-measuring pillow) is a device designed to directly determine the snow water equivalent in the snow cover by measuring the weight or pressure of the snowfall. Snow-pillows allow collecting, accumulating and transmitting information about snow accumulation and snow melting with high discreteness, accuracy and promptness. Within the framework of implementing the initiated project, a snow-pillow prototype was created based on analogue strain-measuring sensors working in conjunction with an accumulating mechanism and a digital indicator run via a microcontroller. Subject to agreement with the directorate of the Federal State Budgetary Institution “Bashkir UGMS”, the snow-pillow prototype was installed on the territory of the meteorological station Ufa-Dema in November 2019. Placing the pillow at the active weather observation station allows comparing the results obtained from the prototype with the data obtained at the station. Comparing the observation results for the autumn-winter season of 2019 has allowed us to conclude that the results obtained at the snow pillow are in line with the data of instrumental observations. The operating experience of the snow pillow shows that the prototype created under the project is applicable for evaluating the snow water equivalent, provided some minor changes are introduced into the design. In the future, observation results obtained from a network of snow pillows can be used for adjusting analytical models of snow accumulation and melting within the territory.
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Zarudskiy, Georgy K. "Minimization of Technical Active Power Losses in Extra-High Voltage Overhead Power Lines Taking the Corona Effect into Account." Elektrichestvo, no. 3 (2022): 5–21. http://dx.doi.org/10.24160/0013-5380-2022-3-5-21.
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A technique has been developed to minimize active power losses that takes into account the corona effect on extra-high voltage overhead power transmission lines in normal modes of their operation. The corona effect is modeled by a specific conductivity, which is a nonlinear function of the voltage level. The equivalent conductivity value is corrected for the actual weather conditions iteratively by changing the r.m.s. voltage value. A universal expression for estimating the effect of operating parameters on the change of voltage along the line length and a graphic illustration of this effect are presented. By differentiating the functional dependence of the total active power losses, formulas are obtained for calculating the operating parameters corresponding to the minimum loss values, assuming that the conductivity does not depend on voltage. It is shown that the operating and technical limitations on the voltage values at the line ends and in its intermediate sections significantly reduce the range of transmitted power with minimal losses. The iterative calculation sequence for determining the reduced voltage level corresponding to the lowest total losses is outlined. The transmitted power values at different corona intensities are calculated. The study results have shown the need to take into account the nonlinear dependence of equivalent conductivity on the r.m.s. voltage value.
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Voitkans, Janis, and Arnis Voitkans. "Tesla Coil Theoretical Model and its Experimental Verification." Electrical, Control and Communication Engineering 7, no. 1 (December 1, 2014): 11–19. http://dx.doi.org/10.1515/ecce-2014-0018.
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Abstract In this paper a theoretical model of Tesla coil operation is proposed. Tesla coil is described as a long line with distributed parameters in a single-wire form, where the line voltage is measured across electrically neutral space. By applying the principle of equivalence of single-wire and two-wire schemes an equivalent two-wire scheme can be found for a single-wire scheme and the already known long line theory can be applied to the Tesla coil. A new method of multiple reflections is developed to characterize a signal in a long line. Formulas for calculation of voltage in Tesla coil by coordinate and calculation of resonance frequencies are proposed. The theoretical calculations are verified experimentally. Resonance frequencies of Tesla coil are measured and voltage standing wave characteristics are obtained for different output capacities in the single-wire mode. Wave resistance and phase coefficient of Tesla coil is obtained. Experimental measurements show good compliance with the proposed theory. The formulas obtained in this paper are also usable for a regular two-wire long line with distributed parameters.
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Kim, Ui-Jin, and Seok-Gyu Oh. "New Sub-Module with Reverse Blocking IGBT for DC Fault Ride-Through in MMC-HVDC System." Energies 14, no. 6 (March 11, 2021): 1551. http://dx.doi.org/10.3390/en14061551.
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When integrating multi-grid renewable energy systems, modular multi-level converters (MMCs) are promising for high-voltage DC (HVDC) transmission. Because of the characteristics of the system, however, it is more difficult to prevent a fault at the DC terminal than at the AC terminal of the MMC. Accordingly, a fault ride-through (FRT) strategy for the operation of the MMC in the DC terminal is required for stable system operation. In this paper, a solution for closed-circuit overcurrent caused by a permanent line-to-line DC fault is proposed. This method is able to reduce the fault current through the adjustment of the slope of the total voltage in the system by operating a sub-module having lower switching losses and fewer passive devices compared with existing topologies. Additionally, through the equivalent circuit of the proposed scheme in a sub-module in case of a fault, the FRT mechanism for the fault current is explained. The feasibility of this proposed technique was verified through time-domain simulations implemented by Powersim, Inc.
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Gao, Jun. "Research and Analysis on Acceptance and Evaluation of WuGuang Railway Noise Testing." Applied Mechanics and Materials 602-605 (August 2014): 2205–9. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.2205.
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HSL (HSL line) noise mainly exhibits on the noise source and its radiation intensity. Testing on noise can be done at the location with maximal noise vertical distribution, by monitoring on certain points continuously 14h, general monitoring to equivalent sound lever of 1h operation no less than average density day and night, and independent monitoring to noise susceptible architecture.
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Ye, Jun, Ke Zheng, Hong Liang Sun, and Yu Chen. "Transient Simulation of Lightning Wave on Transmission Line." Applied Mechanics and Materials 462-463 (November 2013): 585–91. http://dx.doi.org/10.4028/www.scientific.net/amm.462-463.585.
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Lightning is the main reason to cause line tripping and service interruption, and its surge wave invaded into substation over the line is also the key factor which impact on the safe operation of equipments. Research on over-voltage transmission of lightning will be benefit to measure the lightning interference impact on energy metering equipments. Analyzing the transient process of the transmission line must adopt the telegraph equations. In this paper, the partial differential equations were discrete with the FDTD method. Then the equivalent power source of lightning is added at the starting point and the purely resistive load is added at the terminal. Finally, the transient propagation process of lighting was simulated in MATLAB. The three type of lossless non-uniform, lossy uniform or non-uniform transmission lines were considered.
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Liu, Zhi Chun, Qian Yang, and Ming Lei Sun. "The Application of Equivalent Flow Model in Groundwater Resources Loss Estimate of Fractured Rock Tunnel." Advanced Materials Research 368-373 (October 2011): 1249–52. http://dx.doi.org/10.4028/www.scientific.net/amr.368-373.1249.
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This With the deepening of sustainable development strategy, groundwater environmental problems caused by tunnel projects are becoming more and more outstanding. This paper estimate the groundwater resources loss of fractured rock tunnel adopting equivalent flow models. In order to increase the model fidelity, the author considers the nonhomogeneous and anisotropic characteristics of fractured rock. Based on Shibanshan tunnel in Shijiazhuang-Taiyuan passenger line, this paper estimated the groundwater resources loss of fractured rock tunnel in construction stage and operation stage, which provides technical support for decreasing loss of groundwater resources.
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Zhu, Li Yun, Jin Gang Wang, Yu Yi Fan, and Yun Jie Bai. "The Simulation of Distribution Parameter of the Three-Phase D-Dot Voltage Sensor." Applied Mechanics and Materials 556-562 (May 2014): 2123–27. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.2123.
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As an electric coupling sensor, the D-dot voltage sensor can achieve non contact measurement of voltage. With the advantages of simple structure, a high dynamic range and measurement bandwidth, it can meet the needs of accurate measurement[1][2]. Thus it has great application prospects in voltage on-line monitoring, relay protection or other fields in the power system. This paper considered the operation of the three-phase lines, and established the D-dot voltage sensor simulation model in the simulation platform of Ansoft Maxwell 3D. With the simulation of the sensor working conditions, we can get the distributed parameters of the system under three-phase lines in operation, construct an equivalent circuit of measurement and analyze the simulation results to get a voltage signal of input and output. The simulation results show that, with the equivalent circuit simulation of the three-phase D-dot voltage sensor, if we improve electrode capacitance parameter, there will be a good linear relationship between the input and output.
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B, Sathyaprabakaran, Subrata Paul, and Debashis Chatterjee. "A New strategy for on- line Droop adjustment for Microgrid connected DGs." International Journal of Power Electronics and Drive Systems (IJPEDS) 9, no. 1 (March 1, 2018): 139. http://dx.doi.org/10.11591/ijpeds.v9.i1.pp139-149.
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This paper proposes a simple and effective control technique for interconnection of DG resources to the power grid via interfacing converters based on Phase locked loop (PLL) and Droop control. The behaviour of a Microgrid (MG) system during the transition from islanded mode to grid-connected mode of operation has been studied. A dynamic phase shifted PLL technique is locally designed for generating phase reference of each inverter. The phase angle between filter capacitor voltage vector and d-axis is dynamically adjusted with the change in q-axis inverter current to generate the phase reference of each inverter. During fluctuations in load capacity, the grid-connected system must be able to supply balanced power from the utility grid side and micro-grid side. Therefore, droop control is implemented to maintain a balanced power sharing. The inverter operates in voltage control mode in order to control the filter capacitor voltage. An adjusted droop control method for equivalent load sharing of parallel connected Inverters, without any communication between individual inverters, has been presented. The control loops are tested with aid of MATLAB Simulink tool during several operating conditions.
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Popov, Maxim G., Azamat A. Dautov, Petr N. Mankov, Alexey A. Melnikov, and Konstantin G. Goriachevskii. "EXPERIMENTAL RESEARCH OF LINE POWER UNLOADING AUTOMATICS WITH ITS TRIPPING CHARACTERISTICS CORRECTION." Vestnik Chuvashskogo universiteta, no. 1 (March 30, 2022): 142–55. http://dx.doi.org/10.47026/1810-1909-2022-1-142-155.
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In conditions of complicated structure of modern power grids, a special emphasis is given to the issues of ECA failure-free operation. This article is concerned with the problems of increasing sensitivity and selectivity of line power unloading automatics because its correct operation plays an important role in ensuring energy security and survivability of power systems.
Within the framework of this paper, the full cycle of development of ECA algorithm is considered. ECA is performing the functions of line power unloading automatics. The development cycle includes the tasks of tentative assessment of electrical equipment operating modes, rationale for choosing the automatics tripping characteristics, algorithm design and programmable logic controller (PLC) based implementations. It also includes the laboratory testing with the use of real-time hardware and software complex.
The calculation data of steady-state and transient operating modes of power electrical equipment presented in the article were carried out in software complexes RastrWin, Rustab. The power facilities of the interconnected power systems of Urals, Siberia and Kazakhstan were considered as modeled objects of power systems. In accordance with the obtained results, the tripping characteristics of device being developed were determined.
Based on the results of mathematical simulation of electrical equipment transient operating modes, the major disadvantages of device algorithm, which controls the active-power flow through the line, were determined. Besides, methods focused on increasing the sensitivity and selectivity of such automatics are proposed.
The developed algorithm controls the active-power flow over a given cross section. Measurements of electrical parameters are carried out at one of the lines in cross section. The total value of active-power flow over the cross section is calculated according to the equivalent circuit. To increase the sensitivity and selectivity of automatics, the algorithm uses the action time adjustment. It is determined depending on the previous operating mode of transmission line.
The algorithm for line power unloading automatics described in this article was implemented on a PLC system in accordance with the IEC 61131 standard. The obtained device was successfully tested on the real-time hardware and software complex. This paper presents the results of the carried out device performance tests, and the characteristics of the used mathematical simulation.
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Zhang, Hui, Wenling Jin, Mengpeng Hu, Mai Hu, Jingqiu Liang, and Qiang Wang. "Investigation and Optimization of a Line-Locked Quartz Enhanced Spectrophone for Rapid Carbon Dioxide Measurement." Sensors 21, no. 15 (August 2, 2021): 5225. http://dx.doi.org/10.3390/s21155225.
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We have developed a rapid quartz enhanced spectrophone for carbon dioxide (CO2) measurement, in which the laser wavelength was tightly locked to a CO2 absorption line and a custom quartz tuning fork (QTF) operating at 12.5 kHz was employed. The intrinsic QTF oscillation-limited response time, as well as the optimal feedback interval, was experimentally investigated. By tightly locking the laser to the R(16) transition of CO2, we obtained a stable laser operation with its center wavelength variation kept within 0.0002 cm−1, merely three times the laser linewidth. The reported CO2 sensor achieved a detection limit of 7 ppm, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 4.7 × 10−9 W·cm−1·Hz−1/2, at a response time of 0.5 s. The detection limit can be further improved to 0.45 ppm at an integration time of 270 s, illustrating a good system stability. This spectrophone enables the realization of compact and fast-response gas sensors for many scenarios, where CO2 concentration from sub-ppm to hundreds of thousands of ppm is expected.
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Liu, Zhi Chun, Xin Qiang Gao, and Ming Lei Sun. "The Apply of Anisotropy Equivalent Flow Model in Research of Tunnel Drainage Influence Radius." Applied Mechanics and Materials 90-93 (September 2011): 1250–55. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.1250.
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Tunnel drainage influence range is a difficult hydrological problem. It relates directly to tunnel groundwater environment influence degree in construction and operation stages. Based on Shibanshan tunnel in Shijiazhuang-Taiyuan passenger line, this paper analyses influencing factor of tunnel drainage influence radius and flow transient process adopting heterogeneity and anisotropy equivalent flow models. This paper studies the tunnel drainage influence radius and construction progress , hydrology factors, geological factors and rainfall infiltration factors relations. Research results show that the influence factors are rock permeability, rainfall infiltration recharge and aquifer thickness on tunnel top, less influence factors are structure surface direction, anisotropy characteristic coefficient and primary support of the closed time. The conclusions will provide technical supports for evaluating the tunnel construction of groundwater environmental impact.
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Hai, Tian Shu, Qing Hao Wang, Chang Xin Ge, Shao Yong Wu, Peng Fei Cheng, Shuo Cheng, Yang Hu, Zhi Xuan Li, Dong Wei Huang, and Feng Shi. "The Research on Deposition Saturation of Disc Suspension Porcelain Insulator." Advanced Materials Research 986-987 (July 2014): 1881–83. http://dx.doi.org/10.4028/www.scientific.net/amr.986-987.1881.
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The equivalent salt deposit density (ESDD) is an important characteristic of our country which is used to measure insulator deposition level. The contamination of the insulator would reach saturation after a period of time.In order to increase the specific creepage distance, disc suspension porcelain insulator lower surface inward concave, which makes the rain washing the upper surface difficult, that cause the saturation time of lower surface longer than upper surface .For studying the operation insulator contamination saturation time and reflecting the ESDD of the actual operation line accurately,this paper adopts a comparison method between empty hanging insulator surface and operation insulator surface to measure the ESDD , the field experimental results further verify that the saturated time of disc suspension insulator lower surface is longer, so as to lay the foundation for the ESDD measurement.
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Xie, Jin Bao, Ying Han, Long Han, and Rui Na Yang. "Taboo Search Algorithm for Optimizing Shunting Scheme of Through Wagon Flow Delivering and Fetching Operation." Applied Mechanics and Materials 178-181 (May 2012): 1908–14. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.1908.
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In order to improve the efficiency of selecting the optimal scheme from the delivering and fetching shunting schemes of through wagon flow to and from the enterprise dedicated lines which are located in radial shape, the taboo search algorithm is applied in the process finding the optimal solution. The objective function is directly used as the fitness function, and the solution generated by exchanging the wagon group delivering order of one dedicated line with another is taken as the new solution; the taboo list is two-dimensional array, and a fixed value is given as the taboo length; if the evaluation value of the current optimal solution is superior to the historical one, the taboo rules will be defied and the current optimal solution be directly accepted; once the iteration number reaches the predetermined number, the calculating process will be terminated. The simulation results verify the effectiveness of the Taboo search algorithm to the problem, and show that the bigger the number of the dedicated lines, the more the number of equivalent schemes and the higher the searching efficiency is. And the smaller the number of the equivalent schemes, the bigger the search scope is. If the number of the dedicated lines is not more than 8, the processing time by computer is not longer than 15 milliseconds.
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Ghaffarian, Mohammad Saeid, Gholamreza Moradi, Somayyeh Khajehpour, Mohammad Mahdi Honari, and Rashid Mirzavand. "Dual-Band/Dual-Mode Rat-Race/Branch-Line Coupler Using Split Ring Resonators." Electronics 10, no. 15 (July 28, 2021): 1812. http://dx.doi.org/10.3390/electronics10151812.
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A novel dual-band/dual-mode compact hybrid coupler which acts as a dual-band branch-line coupler at the lower band and as a rat-race coupler at the higher band is presented in this paper. One of the most interesting features of the proposed structure is that outputs of the proposed coupler in each mode of operation are on the same side. This unique design is implemented using artificial transmission lines (ATLs) based on open split ring resonators (OSRR). The low-cost miniaturized coupler could be operated as a dual-band 90° branch-line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz. The proposed coupler could be utilized in the antenna array feeding circuit to form the antenna beam. The structure’s analytical circuit design based on its equivalent circuit model is provided and verified by measurement results.
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BLAZHKO, Lyudmila S., Artem A. KISELEV, Igor P. KISELEV, and Andrey V. ROMANOV. "Discussing the effect of the wheelset equivalent conicity on the stress-strain state of the rails." Proceedings of Petersburg Transport University 2021, no. 2 (June 2021): 261–72. http://dx.doi.org/10.20295/1815-588x-2021-2-261-272.
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Objective: To assess the effect of the wheelset equivalent conicity on the stress-strain state of the rails. Methods: Authors used numerical integration methods for systems of nonlinear differential equations of motion in the Universal Mechanism software package. Experimental studies were carried out on the St. Petersburg – Moscow high-speed line using a multichannel strain-gauge station. Methods of mathematical statistics have been used to process the results of numerical simulation and field experiment. Results: The stresses and strains in the wheel-rail contact area and their dependence on the wheelset equivalent conicity have been determined. According to numerical simulation and field experiment, the convergence was within 15 %. Practical importance: The need for updating the standards for the maintenance of a rail track on high-speed lines has been revealed. Allowing for the wheelset equivalent conicity decreases the risk of intense hunting oscillation, which would reduce the dynamic wheel–rail effect. Mobile treatment of rails on the way makes it possible to extend the safe operation time and reduce the rolling stock motion resistance force of the track.
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Li, H. X., A. H. Zhu, C. C. Ma, P. W. Sun, J. W. Yang, and K. Q. Zhang. "Influence of Wheel Profile Wear Coupled with Wheel Diameter Difference on the Dynamic Performance of Subway Vehicles." Shock and Vibration 2021 (June 10, 2021): 1–15. http://dx.doi.org/10.1155/2021/6694561.
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In view of the coexistence of wheel profile wear (WPW) and wheel diameter difference (WDD) on an actual subway line, a dynamic analysis method based on coupling between WPW and equivalent in-phase WDD was proposed. Based on the measurements from a subway vehicle in operation on this line, dynamics modeling and calculations were performed for a single carriage of this vehicle. Later, the interaction between the effects of WPW and equivalent in-phase WDD on the vehicle dynamic performance was analyzed, and the dynamic response in the presence of coupled damage was compared between the outer and inner wheels. Furthermore, the difference in the dynamic response caused by different positions of the larger-diameter wheels (i.e., on the inner track or outer track) was analyzed for the case where equivalent in-phase WDD occurred between the front and rear bogies. The results show that when the vehicle ran on a straight line, the coupling between WPW and WDD reduced the vehicle’s stability but improved its ride comfort. When the vehicle traveled on a curved line, it showed reductions in the lateral wheel/rail contact force, derailment coefficient, axle lateral force, and wear index if the outer wheels had a larger diameter. As a result, the deterioration of the vehicle’s dynamic performance due to the increasing degree of WPW slowed down, and its curve negotiation performance improved. Meanwhile, the outer wheels had significantly greater lateral wheel/rail contact force, derailment coefficient, and wear index compared to the inner wheels. When a −1 mm WDD was coupled with the worn wheel profile for 14 × 104 kilometers traveled, the dynamic performance indexes of the vehicle were close to or even exceeded the corresponding safety limits. The findings can provide technical support for subway vehicle maintenance.
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Yang, Jia, Hai Bao, and Ling Wang. "Study on Electricity-Theft Criterion Based on the Unchanged Line Resistance of the Distribution Network." Advanced Materials Research 614-615 (December 2012): 1385–89. http://dx.doi.org/10.4028/www.scientific.net/amr.614-615.1385.
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The power, voltage and current will change along with the change of grid’s operation mode; however, the line resistance is unchanged. This paper analyzed the limitation and inadaptability of the existed methods used for anti-electricity-theft. And most of the criterions are based on the variable electrical quantities. In order to establish a criterion that can find out the position of electricity-theft accurately, it chose line resistance as a reference value, and calculated the equivalent resistances of each node and branch combining with the actual measurement system. To verify the validity of this criterion, a medium and low voltage distribution network was structured in the Matlab/Simulink simulation platform. The results, which are basically consistent with the actual situations, show that the criterion based on line resistance can well investigate electricity-theft, and also verify that the introduction of this method will bring great benefits to engineering applications.
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Ahmedova, Olga, Anatoliy Soshinov, and Natalia Shevchenko. "Analysis of influence of external atmospheric factors on the accuracy of fault location on overhead power lines." E3S Web of Conferences 178 (2020): 01057. http://dx.doi.org/10.1051/e3sconf/202017801057.
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Devices of fault location are widespread in electrical grids. In overhead power lines of voltages of 10 kV and higher, such devices are based on measurements of parameters in emergency mode. These devices can be divided into two main groups: designed to determine fault location of short circuits and of ground short circuit. In both cases, when detecting fault location, analyzed are not only the current and voltage parameters at the accident time, but also the parameters of overhead power line. When analyzing equivalent circuits of power lines, approximate tabular values of direct and quadrature parameters are used. It was revealed, that the line parameters are significantly affected by external atmospheric factors: ambient temperature, soil moisture, wind strength and direction, ice formation, etc. To accurately determine the fault location, it is necessary to evaluate the influence of these factors on the linear parameters of the overhead line. The paper presents analysis of the influence of changes in atmospheric factors on parameters of overhead power line. A methodology for calculating the operation setpoints of the device for fault location in power line is given.
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Moradi, Elham, Ali-Reza Moznebi, Kambiz Afrooz, and Masoud Movahhedi. "Four-way Gysel power divider/combiner with back-to-back configuration for dual-band operation." International Journal of Microwave and Wireless Technologies 10, no. 2 (October 17, 2017): 265–70. http://dx.doi.org/10.1017/s1759078717001064.
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In this paper, a four-way dual-band Gysel power divider (GPD)/combiner based on a back-to-back microstrip structure method is proposed and investigated. A two-layer substrate is adopted to implement this PD. In order to divide the input signal into four equivalent signals, the input and four output ports of the proposed PD are placed on the top and the four external isolation resistors are placed on the bottom layer of the substrate. Furthermore, the dual-band response is achieved by adding a short-circuit stub and an open-circuit stub to the structure. Then, the theoretical closed-form design formulas are derived based on the considered conditions and circuit transmission line theory. Finally, for verification purpose, a prototype PD is designed, fabricated, and measured which works at dual frequencies of 1 and 2 GHz simultaneously. The good agreement between simulation and measurement results, which show good impedance matching, isolation, as well as power transmission, verifies the correctness of the design theory.
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Pozo, Borja, José Ángel Araujo, Henrik Zessin, Loreto Mateu, José Ignacio Garate, and Peter Spies. "Mini Wind Harvester and a Low Power Three-Phase AC/DC Converter to Power IoT Devices: Analysis, Simulation, Test and Design." Applied Sciences 10, no. 18 (September 11, 2020): 6347. http://dx.doi.org/10.3390/app10186347.
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Wind energy harvesting is a widespread mature technology employed to collect energy, but it is also suitable, and not yet fully exploited at small scale, for powering low power electronic systems such as Internet of Things (IoT) systems like structural health monitoring, on-line sensors, predictive maintenance, manufacturing processes and surveillance. The present work introduces a three-phase mini wind energy harvester and an Alternate Current/Direct Current (AC/DC) converter. The research analyzes in depth a wind harvester’s operation principles in order to extract its characteristic parameters. It also proposes an equivalent electromechanical model of the harvester, and its accuracy has been verified with prototype performance results. Moreover, unlike most of the converters which use two steps for AC/DC signal conditioning—a rectifier stage and a DC/DC regulator—this work proposes a single stage converter to increase the system efficiency and, consequently, improve the energy transfer. Moreover, the most suitable AC/DC converter architecture was chosen and optimized for the best performance taking into account: the target power, efficiency, voltage levels, operation frequency, duty cycle and load required to implement the aforementioned converter.
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Quan, Yu Sheng, Ning Chen, Shai Gen Han, and Pu Xin Shi. "New Methodology of Monitoring for the Contamination Degree of Insulators." Applied Mechanics and Materials 521 (February 2014): 339–42. http://dx.doi.org/10.4028/www.scientific.net/amm.521.339.
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Insulator is an essential part of overhead line. In recent years, the news about the insulator flashover is increasing. The main reason of insulator flashover is insulator surface contamination. Insulator flashover is a serious threat to the safe and stable of transmission lines operation. With the development of China's comprehensive national strength, power companies and power users demand on grids stability is highly increased. Currently usual methods of insulator monitoring are ESDD (equivalent salt deposit density), experiment and on-line detecting of leakage current [. But they can't fully meet our requirements. Now this paper will present a new method, which is made correlation analysis by harmonic analysis based on two ends of the existing lines to the data acquisition apparatus of voltage and current signals. Without additional hardware devices online monitoring of insulator surface contamination can be achieved.
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Yang, Zhuan Zhao, Dao Xin Liu, and Xiao Hua Zhang. "Study on Residual Strength of Pipe with Single Hemisphere Bottom Defect Using FEM Analysis." Advanced Materials Research 314-316 (August 2011): 1367–71. http://dx.doi.org/10.4028/www.scientific.net/amr.314-316.1367.
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The stress and strain condition of the corroded line pipe with single hemisphere bottom defect under deferent inner pressure were analyzed by the Finite Element Methods (FEM) in this paper; At the same time, the residual strength models for the corroded pipe were established based on both the Von Mises equivalent stress and the Von Mises equivalent strain of the finite unit on the defect local zone respectively, the residual strength was decreased with the defect size (d/t) linearly. This way, the residual strength for the corroded pipe with a given defect size (d/t) could be conducted by using the model properly, which could help the owner make a decision when happened to the same defect in the operation. The analysis results shown that the residual strength calculation should choose based on stress when the defect depth (d/t) was less than 0.5, or else choose based on the strain when defect depth (d/t) was exceeds 0.5.
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Gade, VeeraBhadra Chary, and Mercy Rosalin Kotapuri. "A Three Phase Matlab Simulink Model of IEEE 57 Bus Power System Network." International Journal of Engineering & Technology 7, no. 4.24 (November 27, 2018): 142. http://dx.doi.org/10.14419/ijet.v7i4.24.21875.
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The Electrical power system, field engineers always strive to design a Real time power system model to anticipate the practical outcomes. The simulation software not only fixes the changes in power system, but also trying to perceive the potential impact of power system before construction. A realistic model of the power system is very essential for the future and present operations. Present, this paper makes center of attention on designing of 3-phase power system network of IEEE 57 bus power system network within the Matlab Simulink module. It supports GUI (Graphical User Interface) based models of power system components, which are used to design a dynamic model of the power system. The present design is based on the test case data and the one line diagram; so that the three-phase model is equivalent to single phase one line diagram. The simulation of this model allows for verification of voltage, current, active power and reactive power of each bus and variation of those parameters with respect to time domain waveform. The present model is also useful for learning the operation of the power system network under Steady state, Transient state and Dynamic state with the application of FACTS, Fuzzy, and ANN etc.
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Wang, Ling Yun, Ye Shuang Zheng, Jie Pan, and Yuan Liu. "Power Flow Calculation of Distribution Network with DG Based on Advanced Forward and Backward Substitution Algorithm." Applied Mechanics and Materials 483 (December 2013): 569–73. http://dx.doi.org/10.4028/www.scientific.net/amm.483.569.
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Compared with the traditional power system, there are some differences in the aspect of distribution network structure, line parameters and load parameters in the power system with distributed generations. Therefore, the conventional power flow algorithm can not be applied to this kind of networks. Considering that the distributed generations have special influence on the operation of distributed network, a novel power flow calculation method for this kind of distribution network is studied in this paper. Several equivalent circuit models of distributed generations and the corresponding approaches have been researched. The feasibility of this proposed power flow algorithms can be verified through the program designed in Matlab software.
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Lu, Guang Ming, Wei Zhang, Jian Feng Yan, Yong Jun Yu, Zhi Hong Yu, Yan Hui Qin, Ying Lv, et al. "Comparative Analysis of the Calculation Results of Online Short-Circuit Current Based on PSASP and Fault Wave Recording." Advanced Materials Research 1070-1072 (December 2014): 897–901. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.897.
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In daily operation process,the results of online short-circuit current calculation and fault wave recording is different, the differences between the two results affected the dispatcher’s decision. In-depth analysis of the calculation process and finding the possible causes of the differences should be done. The on-line PSASP short-circuit current calculation based on power flow and scheme was studied. The boundary conditions and calculation models of two methods were studied, the influence of the modeling scope and equivalent circuits to the short-circuit current was also studied. Fault wave recording calculated short-circuit current through forward calculation, the middle to both sides calculation and backward calculation, and the differences of the three calculation mode were also analyzed. Through the above analysis and comparison, online data equivalent to 220kV high voltage side of the transformer greatly impacts short-circuit current, but effective value calculation method of fault wave recording has a little impact on the short-circuit current, mainly in the following reasons, the first one is that non-dispatching power plant is equivalent to a load, the second one is that several different types of load is equivalent to a load using one load model, the third one is that all devices connecting to low voltage side of the 220kV transformers are equivalent to 220kV. Conclusions of the analysis can provide the basis for the practical work of online short-circuit current calculation.
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Wang, Chen, Shihui Luo, Ziqiang Xu, Chang Gao, and Weihua Ma. "Research on Bogie Frame Lateral Instability of High-Speed Railway Vehicle." Shock and Vibration 2018 (May 29, 2018): 1–13. http://dx.doi.org/10.1155/2018/8469143.
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In order to find out the reason for the bogie frame instability alarm in the high-speed railway vehicle, the influence of wheel tread profile of the unstable vehicle was investigated. By means of wheel-rail contact analysis and dynamics simulation, the effect of tread wear on the bogie frame lateral stability was studied. The result indicates that the concave wear of tread is gradually aggravated with the increase of operation mileage; meanwhile the wheel-rail equivalent conicity also increases. For the rail which has not been grinded for a long time, the wear of gauge corner and wide-worn zone is relatively severe; the matching equivalent conicity is 0.31-0.4 between the worn rail and the concave-worn-tread wheel set. The equivalent conicity between the grinded rail and the concave-worn tread is below 0.25; the equivalent conicities are always below 0.1 between the reprofiled wheel set and various rails. The result of the line test indicates that the lateral acceleration of bogie frame corresponding to the worn wheel-rail can reach 8.5m/s2, and the acceleration after the grinding is reduced below 4.5m/s2. By dynamics simulation, it turns out that the unreasonable wheel-rail matching relationship is the major cause of the bogie frame lateral alarm. With the tread-concave wear being aggravated, the equivalent conicity of wheel-rail matching constantly increases, which leads to the bogie frame lateral instability and then the frame instability alarm.
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Akhmedova, Olga, Anatoliy Soshinov, Farit Gazizov, and Svetlana Ilyashenko. "Development of an Intelligent System for Distance Relay Protection with Adaptive Algorithms for Determining the Operation Setpoints." Energies 14, no. 4 (February 12, 2021): 973. http://dx.doi.org/10.3390/en14040973.
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The drastic consequences of emergencies force us to look for ways to increase the stability of the device operation at overhead power transmission lines (OHPTL). It can be achieved by developing new algorithms for determining the protection operation setpoints and detecting the damage location. Fault detection at OHPTL of 10 kV and above is mainly carried out by the devices based on the measurement of emergency mode parameters. For fault detecting one should analyze the parameters of not only current and voltage at the accident time, but also of the overhead power line. Specific active resistance, specific reactance, specific active conductivity and specific reactive conductivity are used to characterize the overhead power transmission lines. As a rule, these parameters are normalized to the unit of length of the overhead line (OHL) and linear values are used in the calculations. When analyzing power lines, tabular approximate values of longitudinal and transversal parameters in equivalent circuits are used, although solving problems in an unsimplified form leads to significant refinements of the known solutions, since OHLs are influenced by external atmospheric factors (ambient temperature, soil moisture, wind force, ice formation, etc.). The paper analyzes these characteristics and evaluates the influence of the listed factors on the linear longitudinal and transversal parameters of overhead lines. A functional dependence of external factors on the distance protection actuation setpoint was obtained. A method for automatic correction of the setpoint of the intelligent protection complex and an adaptive relay protection algorithm was developed, taking into account changes in climatic factors, enabling to reduce the “dead zone” length and increase the protection sensitivity. The use of line parameters obtained from the sensors in the calculations give rise to a more accurate fault detection based on the use of remote sensing methods.
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Wang, Yanyun, Guoqiong Zhou, Chunping Zeng, Wenbin Zhang, Yanan Ren, Yi Ke, Hequn Chu, and Chunguang Suo. "Research on On-Line Detection Method of Transformer Winding Deformation Based on VFTO." Sensors 21, no. 21 (November 6, 2021): 7386. http://dx.doi.org/10.3390/s21217386.
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At present, the detection of transformer winding deformation faults is carried out in an offline state, which requires the transformer to cooperate with the implementation of planned power outages, or it takes place after the sudden failure of the transformer when it is out of operation. It is difficult to obtain the status information of the windings online in time. Since the transformer will suffer very fast transient overvoltage (VFTO) impact during operation, combined with the principle of the frequency response method, an online detection method of transformer winding deformation based on VFTO is proposed. In order to study the frequency response characteristics of transformer winding under the impact of VFTO, the generation process of VFTO is simulated by simulation software, and the equivalent circuit model of transformer winding before and after deformation is established. The VFTO signal is injected into the transformer circuit model as an excitation source, and the changes of resonant frequencies of frequency response curve under different deformation types and different deformation degrees of winding are analyzed. The simulation results show that the frequency response curves of different winding deformation types are different. Different deformation degrees are simulated by increasing the radial capacitance by 4%, 13%, and 23%, series inductance by 2%, 4%, and 6%, and longitudinal capacitance by 3%, 6%, and 9%, and the change of resonance frequencies can comprehensively reflect the deformation information of winding. At the same time, the tests of different deformation types and deformation degrees of the simulated winding are carried out. The results show that with the deepening of the change degree of the simulated fault inductance value, the frequency response curve shifts to the low-frequency direction, confirming the feasibility of the online detection method of transformer winding deformation based on VFTO.
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Yan, Xiangwu, Hongbin Ma, Jiaoxin Jia, Waseem Aslam, Chenguang Wang, Shizheng Zhang, and Baixue Liang. "Precise Reactive Power-Voltage Droop Control of Parallel Virtual Synchronous Generators That Considers Line Impedance." Electronics 10, no. 11 (June 3, 2021): 1344. http://dx.doi.org/10.3390/electronics10111344.
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Problems such as high power coupling, low distribution accuracy, and insufficient reactive power-voltage droop accuracy occur when distributed generators are operated in parallel due to the influence of line impedance. The precise control of output reactive power and voltage is difficult to achieve using traditional virtual synchronous generator (VSG) control. Taking this into consideration, this study proposes a virtual synchronous generator reactive power-voltage integrated control strategy that considers line parameters to solve this problem. First, the impedance voltage drop of the line is compensated for in accordance with local information control to ensure the consistency of the control voltage in parallel operation of distributed generators and to realize the precise droop control of reactive power and the voltage of the point of common coupling (UPCC). Second, virtual negative impedance control is added to change the equivalent output impedance characteristics of the system and achieve power decoupling. On this basis, the active frequency and reactive voltage decoupling control effect of the improved control strategy is quantified and analyzed using the relative gain matrix. The accuracy of reactive power distribution and droop control is theoretically derived and analyzed by establishing a small-signal model of a two-machine parallel system. Finally, the accuracy and effectiveness of the proposed integrated control strategy are verified via a simulation model and an experimental platform for parallel operation. Results show that the proposed integrated control strategy can effectively solve the problems of power decoupling and accurate distribution, reduce system loop current, and realize accurate reactive power-voltage droop. Compared with the traditional VSG control strategy, the dynamic deviation of UPCC is reduced by at least 40% when a large-scale load disturbance occurs.
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Li, Dong, and Xing Fu Jin. "A Novel Pilot Protection for HVDC Transmission Lines Based on Model Error Function." Applied Mechanics and Materials 397-400 (September 2013): 1878–82. http://dx.doi.org/10.4028/www.scientific.net/amm.397-400.1878.
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In order to solve the problems in existing protection for high voltage direct current (HVDC) transmission lines, such as insufficient sensitivity for main protection and slow operation for backup protection, a novel pilot protection for HVDC transmission lines based on model error function is proposed in this paper. In the principle, through analyzing the fault component networks, external fault is equivalent to a capacitance model, while the internal fault is equivalent to a inductance model. Taking capacitance model as a benchmark, the model error function was defined to describe the degree of consistency between actual fault data and the benchmark. When an external fault occurs, fault data agree with the capacitance model and model error equals zero. When an internal fault occurs, fault data do not agree with the capacitance model and model error does not equal zero. According to this, a protection criterion is constructed. Theoretical analysis and simulation show that the new principle, not affected by transition resistance and line distributed capacitance current, can identify internal faults and external faults reliably and rapidly.
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Eberspächer, M. A., M. Bauer, and T. F. Eibert. "Design and analysis of an isotropic two-dimensional planar Composite Right/Left-Handed waveguide structure." Advances in Radio Science 9 (July 29, 2011): 73–78. http://dx.doi.org/10.5194/ars-9-73-2011.
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Abstract. A two-dimensional isotropic Composite Right/Left-Handed (CRLH) waveguide structure is proposed which is designed for operation in X-band. The balanced structure possesses left-handed behaviour over a large bandwidth from 7.5 GHz up to its transition frequency at 10 GHz. Above this region, the unit cell behaves in a right-handed manner up to 13.5 GHz. Operating the structure within these bands yields a frequency dependent index of refraction ranging from −2.5 ≤ n ≤ 0.8. Isotropic characteristics are obtained between 8.5 GHz ≤ f ≤ 12 GHz resulting in −1.5 ≤ n ≤ 0.8. The planar CRLH structure is designed based on transmission line theory, implemented in microstrip technology and optimized using full-wave simulation software. An equivalent circuit model is determined describing the electromagnetic behaviour of the structure whose element values are obtained by even and odd mode analysis. The design of the unit cell requires an appropriate de-embedding process in order to enable an analysis in terms of dispersion characteristics and Bloch impedance, which are performed both.
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Lou, Xiansi, Wei Chen, and Chuangxin Guo. "Using the Thermal Inertia of Transmission Lines for Coping with Post-Contingency Overflows." Energies 13, no. 1 (December 20, 2019): 48. http://dx.doi.org/10.3390/en13010048.
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For the corrective security-constrained optimal power flow (OPF) model, there exists a post-contingency stage due to the time delay of corrective measures. Line overflows in this stage may cause cascading failures. This paper proposes that the thermal inertia of transmission lines can be used to cope with post-contingency overflows. An enhanced security-constrained OPF model is established and line dynamic thermal behaviors are quantified. The post-contingency stage is divided into a response substage and a ramping substage and the highest temperatures are limited by thermal rating constraints. A solving strategy based on Benders decomposition is proposed to solve the established model. The original problem is decomposed into a master problem for preventive control and two subproblems for corrective control feasibility check and line thermal rating check. In each iteration, Benders cuts are generated for infeasible contingencies and returned into the master problem for adjusting the generation plan. Because the highest temperature function is implicit, an equivalent time method is presented to calculate its partial derivative in Benders cuts. The proposed model and approaches are validated on three test systems. Results show that the operation security is improved with a slight increase in total generation cost.
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Titt, Uwe, Enzo Pera, and Michael T. Gillin. "Monte Carlo Simulations of Neutron Ambient Dose Equivalent in a Novel Proton Therapy Facility Design." International Journal of Particle Therapy 6, no. 4 (March 1, 2020): 29–37. http://dx.doi.org/10.14338/ijpt-19-00071.1.
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Abstract Purpose The neutron shielding properties of the concrete structures of a proposed proton therapy facility were evaluated with help of the Monte Carlo technique. The planned facility's design omits the typical maze-structured entrances to the treatment rooms to facilitate more efficient access and, instead, proposes the use of massive concrete/steel doors. Furthermore, straight conduits in the treatment room walls were used in the design of the facility, necessitating a detailed investigation of the neutron radiation outside the rooms to determine if the design can be applied without violating existing radiation protection regulations. This study was performed to investigate whether the operation of a proton therapy unit using such a facility design will be in compliance with radiation protection requirements. Methods A detailed model of the planned proton therapy expansion project of the University of Texas, M. D. Anderson Cancer Center in Houston, Texas, was produced to simulate secondary neutron production from clinical proton beams using the MCNPX Monte Carlo radiation transport code. Neutron spectral fluences were collected at locations of interest and converted to ambient dose equivalents using an in-house code based on fluence to dose-conversion factors provided by the International Commission on Radiological Protection. Results and Conclusions At all investigated locations of interest, the ambient dose equivalent values were below the occupational dose limits and the dose limits for individual members of the public. The impact of straight conduits was negligible because their location and orientation were such that no line of sight to the neutron sources (ie, the isocenter locations) was established. Finally, the treatment room doors were specially designed to provide spatial efficiency and, compared with traditional maze designs, showed that while it would be possible to achieve a lower neutron ambient dose equivalent with a maze, the increased spatial (and financial) requirements may offset this advantage.
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Aizenberg, Igor, Riccardo Belardi, Marco Bindi, Francesco Grasso, Stefano Manetti, Antonio Luchetta, and Maria Cristina Piccirilli. "Failure Prevention and Malfunction Localization in Underground Medium Voltage Cables." Energies 14, no. 1 (December 25, 2020): 85. http://dx.doi.org/10.3390/en14010085.
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A smart monitoring system capable of detecting and classifying the health conditions of MV (Medium Voltage) underground cables is presented in this work. Using the analysis technique proposed here, it is possible to prevent the occurrence of catastrophic failures in medium voltage underground lines, for which it is generally difficult to realize maintenance operations and carry out punctual inspections. This prognostic method is based on Frequency Response Analysis (FRA) and can be used online during normal network operation, resulting in a minimally invasive tool. In order to obtain the good results shown in the simulation section, it is necessary to develop a lamped equivalent circuit of the network branch under consideration. The standard π-model is used in this paper to analyse sections of a medium voltage cable and the parameter variations with temperature are used to classify the state of health of the line. In fact, the variation of the electrical parameters produces a corresponding variation in the frequency response. The proposed system is based on the use of a complex neural network with feedforward architecture. It processes the frequency response, allowing the classification of the cable conditions with an accuracy higher than 90%.
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Zhao, J. K., C. Y. Gao, and D. Liu. "The extendedQ-range small-angle neutron scattering diffractometer at the SNS." Journal of Applied Crystallography 43, no. 5 (July 31, 2010): 1068–77. http://dx.doi.org/10.1107/s002188981002217x.
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The extendedQ-range small-angle neutron scattering diffractometer (EQ-SANS) at the Spallation Neutron Source (SNS), Oak Ridge, is designed for wide neutron momentum transfer (Q) coverage, high neutron beam intensity and good wavelength resolution. In addition, the design and construction of the instrument aim to achieve a maximum signal-to-noise ratio by minimizing the background. The instrument is located on the high-power target station at the SNS. One of the key components in the primary flight path is the neutron optics, consisting of a curved multichannel beam bender and sections of straight neutron guides. They are optimized to minimize neutron transport loss, thereby maximizing the available flux on the sample. They also enable the avoidance of a direct line of sight to the neutron moderator at downstream locations. The instrument has three bandwidth-limiting choppers. They allow a novel frame-skipping operation, which enables the EQ-SANS diffractometer to achieve a dynamicQrange equivalent to that of a similar machine on a 20 Hz source. The two-dimensional low-angle detector, based on3He tube technologies, offers very high counting rates and counting efficiency. Initial operations have shown that the instrument has achieved its design goals.
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Olkkonen, Martta-Kaisa. "Online Moisture Measurement of Bio Fuel at a Paper Mill Employing a Microwave Resonator." Sensors 18, no. 11 (November 9, 2018): 3844. http://dx.doi.org/10.3390/s18113844.
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This paper investigates online moisture measurement of biofuel employing a strip line cavity resonator at approximately 366 MHz, attached above and below the conveyor belt. An existing sensor design is modified for the factory assembly, and the correct operation has been tested prior to this paper with a small number of measurement points and collected reference samples (n = 67). The purpose is now to concentrate on the accuracy of the measurement and increase the number of measurement points (n = 367). The measurements were made in 5 different lots, and the thickness and moisture properties of the biomaterial mat were varied between minimum and maximum levels by adjusting the settings of the belt filter press that presses pulp slush into a mat. In order to further reduce inaccuracy, at the maximum one standard deviation was allowed from the average height of the equivalent water layer for each dataset, and consequently the number of samples was reduced to 235. A linear fit and a parabola fit were determined for thickness of the equivalent water layer vs. the relative resonant frequency shift: R2 = 0.82 and R2 = 0.78.
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Slatin, V. V., M. A. Demkin, and A. V. Golubkina. "The Main Provisions of the Methodology for Assessing the Convergence of the Results of Mathematical Modeling of Continuous Processes of Avionics Devices and Field Experiments." Mekhatronika, Avtomatizatsiya, Upravlenie 19, no. 10 (October 11, 2018): 680–88. http://dx.doi.org/10.17587/mau.19.680-688.
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The questions of estimation of convergence of the processes received in single flight tests of an aviation complex and at mathematical modeling are considered. This evaluation is performed based on the methods of analysis of variance and means of verification of statistical hypotheses in decision-making on the convergence of the compared processes. For each of the compared processes, the least squares method determines the regression lines. By methods of mathematical statistics the permissible proximity of regression lines of the compared processes is established and the average regression line equivalent to the mathematical expectation of the analyzed statistical processes is determined. With respect to this line, the variance of deviations of the compared statistical processes is determined and their belonging to the General sample of processes is estimated. This suggests that under normal laws of the distribution of measurement errors there is an adequacy of the processes of the mathematical model of the stages of operation of the aviation complex and the observed processes of these stages during flight tests of the aviation complex under study.
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Chaber, Bartosz, and Wiktor Łodyga. "A Realistic Spark-Gap Model in Computer Simulation of Blumlein Transmission Line." Energies 15, no. 11 (May 26, 2022): 3919. http://dx.doi.org/10.3390/en15113919.
Full textAbstract:
Over the years, the use of numerical simulations in the development of high voltage pulse generators has become a standard approach. Nevertheless, the modeling of spark-gaps, one of the most commonly used switching devices in such generators, has always been a weak point of the process, especially in coupled circuit and field simulations. Although the complex SPICE spark-gap models do exist, it is difficult or impossible to directly couple them with field simulations. Thus, in many cases, the spark-gap models used were elementary and required many assumptions, which led to the prolongation of the design process. Our paper describes the coupling of a realistic circuit model of an air spark-gap, with a Finite Element Method simulation, solving the wave equation in the time domain. The simulation describes the operation of a Blumlein transmission line as a pulse generator. One of the advantages of the proposed solution is that the input parameters of the empirical model are measurable physical quantities characterizing the spark-gap circuit. We have carried out two numerical experiments testing the simulation for both the matched, resistive load and for a dipole antenna connected to the output of the Blumlein transmission line. The test results confirm that the circuit-field simulation can model Blumlein transmission lines with both simple elements (e.g., resistors) and complex circuits (e.g., an equivalent circuit of a dipole antenna) attached to its terminals.
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Zebbadji, Tahar, Seddik Hadji, and Rachid Ibtiouen. "Line and Grid Impedance Impact on the Performances of a Parallel Connected Modular Inverter System." International Journal of Power Electronics and Drive Systems (IJPEDS) 6, no. 1 (March 1, 2015): 100. http://dx.doi.org/10.11591/ijpeds.v6.i1.pp100-108.
Full textAbstract:
With the rising fuel cost, increasing demand of power and the concerns for global climate change, the use of clean energy make the connection of power electronics building bloc in the heart of the current research. The high output current applications make the parallel connection of modular inverters to be a solution for the use of low power building block inverters where the output power cannot be handled by a single inverter configuration. In this context, average-modeling using average phase–leg technique allows the <em>n</em>-parallel connected inverters to be analyzed accurately and rapidly without requiring the complexity of the full switched inverter topology. The obtained analytical solution along with the equivalent circuit model makes easier the design of the control loop. The analytical solution of the <em>n</em>-parallel connected inverters shows the impact of the line and grid impedance on the performance of the overall system. The impact of this coupling has to be investigated such that the main feature of paralleling inverters is guaranteed and that the inverter mode of operation will not be compromised. The main advantage of paralleling inverters can be lost for a certain coupling impedance considerations.