Table of Content

23 November 2013, Volume 46 Issue 11

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Power System

Corrosion and Protection of Hot-Dipped Components in Power Transmission Grid

CHEN Tong, TAN Tian, HONG Yi-cheng, ZHANG Jun-xi

2013, 46(11):  1-7.  DOI: 10.11930/j.issn.1004-9649.2013.11.1.6

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By taking advantage of the maintenance records together with the principle of corrosion electrochemistry, the corrosion that may occur during the service period of hot-dipped components in power transmission grid is analyzed. Considering the operating conditions and the service environments, the corrosion of components including transmission tower, anchor clamp, connecting piece, earth wire and stay wire, is classified and the corrosion mechanism is studied. In addition, several methods for life forecast of zinc coating are introduced, and related preventive measures are proposed based on the characteristic of service environment. Finally, it is proposed that the research of corrosion mechanism, protection technology and life forecast for hot-dipped components in power transmission grid under different service circumstances should be enhanced for the purpose of secure operation of the electric power system.

Reactive Voltage Optimization of a Complex Power Grid Integrated with Large-Scale Wind Power by Improved Artificial Fish Swarm Algorithm (AFSA)

XU Peng, LIU Wen-ying, ZHAO Zi-lan, LI Bo, WANG Ning-bo

2013, 46(11):  8-11.  DOI: 10.11930/j.issn.1004-9649.2013.11.8.3

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Large-scale wind power fluctuations and randomness have significant impact on the initial values of reactive power and voltage optimization, and, as a result, the solution process of reactive power optimization cannot take full account of the voltage-limit nodes with a rather premature convergence and cannot be the optimal solution. So, an improved artificial fish swarm algorithm(AFSA) is proposed to solve the var optimization problem of a gird with integration of large scale wind power. In the initial stage of algorithm process, the mutation mechanism is introduced to regulate the artificial fish-swarm. Meanwhile, in the later stage, the self-adaptive VISUAL and STEP are used to avoid the problems of local optimal solution and slow convergence which are common in the later computation stage. Finally, the GANSU grid is used for case study, which proves the feasibility and effectiveness of the proposed algorithm.

OpenDSS-Based Simulation and Modeling Platform of Smart Distribution System and Its Application

LI Peng, SUN Chong-bo, WANG Cheng-shan, GUO Xiao-long, ZHANG Fei, NIE Song

2013, 46(11):  12-16.  DOI: 10.11930/j.issn.1004-9649.2013.11.12.4

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OpenDSS simulation system can assist the simulation analysis and planning research for distribution grid that contains distributive power sources and energy-storage devices and provide an open and shared research platform for smart distribution grid. The features and advantages of OpenDSS are introduced from the three aspects including modelling method, simulation function and user-defined application. For the modelling method, the OpenDSS takes the asymmetric features of distribution system into account and divides the elements into four classes with the multi-phase modelling method. For the simulation method, the OpenDSS provides a fast power flow method based on which many other capacities are realized. For the user-defined application, OpenDSS can interact with other simulation software based on the COM interface. Some simulation cases are given to show the functions mentioned above for the purpose of promoting the application and development of distribution fast simulation and modelling (DFSM) in China.

Research on Virtual Reality Technology for Galloping Simulation of Power Transmission Lines

HU Chun-mei, JING Qian-ming, WANG Ming-zhe, ZHANG Cheng-xue, HU Ying-ying, HU Ji-cai

2013, 46(11):  17-21.  DOI: 10.11930/j.issn.1004-9649.2013.11.17.4

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Based on the requirements of power transmission line galloping simulation and their practical application, an overall framework of virtual reality reproduction for the galloping simulation of power transmission lines is constructed. A set of functions are developed based on the virtual reality technology, including power transmission line galloping simulation scenarios, nodal movement trajectory virtual reality scenario, whole-process oscillation mode reproduction scenario of galloping, and full nodal amplitude-time history scenario. Corresponding to the simulation system, a group of virtual reality application interfaces are designed and developed for different galloping prevention devices and galloping prevention schemes, which are of good human-computer interaction, simple in operation and easy for using.

Unconventional Installation and On-Site Partial Discharge Test of Ultra-High Voltage Convertor Transformer

NIE Hong-yu, CHEN Ling, LIU Rui, JIANG Wei, LIU Song-xiang, LI Hong-fei

2013, 46(11):  22-25.  DOI: 10.11930/j.issn.1004-9649.2013.11.22.3

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Due to the very limited period for installation of low-end convertor transformer in Jinping converter station, which is delayed by difficult transportation condition, unconventional installation techniques had to be adopted. Based on the successful commissioning experience of Jinping converter station, the paper introduces the method of on-site partial discharge test under the unconventional installation condition, and the analyzing and handling methods of abnormal discharge in the test. This partial discharge testing method not only well solves the possible discharge problems caused by unconventional installation techniques, but also significantly improves the testing efficiency and shortens the testing period, which will provide a useful reference for partial discharge testing of UHV converter transformers.

Research on Electric Field Characteristics of Busbar in HVDC Converter Substation

YUE Yun-feng, PENG Guan-yan, WANG Yan, LI Zhi-tai

2013, 46(11):  26-29.  DOI: 10.11930/j.issn.1004-9649.2013.11.26.3

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Study of electric field characteristics of busbar in the HVDC substation is substaintial to the substation design. Based on the Deutsch assumption, a computation model is established in this paper for the busbar surface electric field and ground total electric field of converter substation and the controlling indices of the total electric field are proposed for the ±800 kV converter substation. With this model, the corona characteristics and the total electric field of various typies of busbars are calculated and the height range of busbar installation and the total electric field on the ground is obtained. As a conclusion, the busbar type and installation method in the ±800 kV converter substation is suggested.

Security Research on Maintenance Operation of 10 kV and 110 kV Mixed-Voltage Transmission Lines on the Same Tower

PENG Yong, SU Zi-ming, LIU Kai, LIU Ting, XIAO Bin, WU Tian, TANG Pan

2013, 46(11):  30-35.  DOI: 10.11930/j.issn.1004-9649.2013.11.30.5

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Mixed 10 kV and 110 kV transmission lines on the same tower can save land resources effectively and make full use of the line corridor. When the 10 kV distribution line is for maintenance, induced voltage and current will occur on the examining line duo to electrostatic and electromagnetic coupling, which may cause harm to the maintenance workers. Furthermore, the synthesis electric field from the mixed transmission lines may also adversely affect the live workers. The ATP-EMTP is used in this paper to calculate the induced voltage and current during maintenance of the 10 kV lines. Both the ANSYS and electric field measurement are used to study the spatial electric field distribution of the mixed lines and the body surface electric field distribution of workers, based on which the security protection method is proposed for maintenance of the mixed 10 kV and 110 kV transmission lines.

Parameter Design and Steady State Characteristic Analysis of TCPSTs in a EHV-Grid

YU Hong-yang, ZHOU Fei, YANG Zeng-hui

2013, 46(11):  36-41.  DOI: 10.11930/j.issn.1004-9649.2013.11.36.5

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The uneven power load flow constantly leads to the flow congestion of the East China Power Grid with some lines having heavy load while other lines having inadequate utilization. In the mean time, building new transmission corridors will face many difficulties. As a result, the overall transmission capacity of the power grid is restricted seriously. In addition, the regional power grid also needs to enhance the transient stability and suppress the system oscillation. Theoretically, the working mechanism of the thyristors controlled phase shifters (TCPSTs) and the influence of transformer’s leakage reactance on the phase shift angle are analyzed. According to the main circuit of TCPSTs, a new parameter design method of main equipment, such as shunt and series transformers, etc., was proposed. Then the steady state characteristics of the TCPSTs are simulated based on a dual generators system to verify the correctness of the proposed parameter design method. Finally, a 500 kV loop network in East China Power Grid is analyzed for power flow optimization, in which the installation locations of TCPSTs are selected and a 4-generator loop network model with the TCPSTs is established based on the real-time digital simulation (RTDS) platform. The simulation result verifies that the TCPST can effectively optimize the active power distribution in the loop network and achieve the anticipated goal.

Feasibility Study of EHV Interconnection Between China Southern Power Grid (CSG) and Vietnam Electricity (EVN)

ZHU Qing-chun, LIN Ting-wei, HUANG Juan-juan, KANG Yi

2013, 46(11):  42-46.  DOI: 10.11930/j.issn.1004-9649.2013.11.42.4

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In recent years, Vietnam Electricity (EVN) faces great shortage of power supply due to fast power load growth and delayed power plant construction. So it can be a possible solution to expand the scale of interconnection between Vietnam Electricity(EVN) and China Southern Power Grid (CSG) based on the existed inter link of 220 kV and import more power from China. Meanwhile, CSG, especially the Yunnan province, has abundant hydropower in flood season, but a difficult power balance in dry season. Therefore, it is necessary to study the feasibility of bi-directional power trading through the expanded interconnection with EVN proposed above to improve the total operation efficiency. Based on the analysis of energy resources across the two countries’ boundary regions, the power balance, as well as the load curve coincidence of CSG and EVN, are studied, and the scheme of the EHV interconnection between CSG and EVN, including the scale and technical route, is proposed. Some constructive suggestions are given on power trading curves, and the economic feasibility of the EHV interconnection is analyzed in terms of the electricity prices.

Impact of Model Parameter Reduction on Load Classification

ZHENG Xiao-yu, ZHENG Jing-yuan, LIU Dong, WAN Xiong, LIANG Zhi-feng, LIU Li-hua

2013, 46(11):  47-51.  DOI: 10.11930/j.issn.1004-9649.2013.11.47.4

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As one of the important components in power simulation, load model has been getting more and more attention. But current load models have lots of parameters, which significantly affects the model's identification accuracy. To solve this problem, the common practice is to reduce the parameters and load classification is always utilized to eliminate the time-dependent characteristics of the power load. However, it is not known yet how the parameter reduction effects the load classification. Cluster analysis is firstly carried out in this paper to classify the load data, and then the trajectory sensitivity analysis is utilized to reduce the model parameters. Reclassification of the load data is then made after parameter reduction and a comparison is conducted between the classification results before and after parameter reduction. A case study indicates that the parameter reduction doesn't increase the classification error significantly and proves the efficiency of the proposed parameter reduction method.

Decoupling Algorithm of Dynamic Reactive Power Optimization with Consideration of Wind Power

YU Qing, HAN Xue-shan, YANG Si, LI Wen-bo

2013, 46(11):  52-56.  DOI: 10.11930/j.issn.1004-9649.2013.11.52.4

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The intermittency and randomness of wind power brings difficulties to the decision-making of dynamic reactive power optimization. Based on the time-dependent characteristics of wind power fluctuations, the paper introduces the concept of scenario in the dynamic reactive optimization model to describe the uncertainty of wind power output, and proposes a decoupling algorithm based on sensitivity information. In the algorithm, the action time and position of capacitors and transformers are firstly determined according to their sensitivity information in every single time interval and wind farm scene. Based on the results of discrete variables, the whole model is decoupled in time and the continuous variables are then determined. Case study of 14-bus system show that the algorithm proposed in this paper is both reasonable and effective.

A New Method for Determining Optimal Load Transfer Scheme in Distribution Network

SUN Da-yan, LIN Ji-keng, YUAN Long, WANG Gang, WANG Wen-jie, QIN Ling, GUO Xing

2013, 46(11):  57-61.  DOI: 10.11930/j.issn.1004-9649.2013.11.57.4

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In view of the slow calculation process of stochastic algorithm in determining the optimal load transfer scheme, a new method is proposed to solve the problem based on the adaptive immune algorithm with infeasible solution recovery in combination with the basic-tree topology fast judging method. With consideration of all the factors of load transfer, this method is characterized by a complete mathematical model. Due to its infeasible solution recovery technology, it has an advantage over stochastic optimization methods in calculation time. Furthermore, to increase the calculation speed, the basic-tree based topology radial fast identification strategy is used to judge the topological radial constraint limits in distribution system for each new solution during the iteration process, as a result, the calculation time for the evolution optimization process is further reduced. Several case studies have proved the effectiveness and validity of this method.

Energy Consercation and Environmental Protection

Application of WESP in Coal-Fired Power Plants and Its Effect on Emission Reduction of PM_2.5

MO Hua, ZHU Fa-hua, WANG Sheng, YI Yu-ping

2013, 46(11):  62-65.  DOI: 10.11930/j.issn.1004-9649.2013.11.62.3

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The wet electro static precipitator(WESP) has been used successfully in developed countries. In order to borrow the excellent experience abroad and promote the emission-reduction of PM_2.5 from the power sector in China, the paper analyzes the principle of WESP, and compares the applications between China and abroad with the technical economics of WESP analyzed. In addition, the contribution of WESP to the reduction of PM_2.5 from the power sector is also demonstrated in details. The foreign operation experience indicates that not only has the number of PM_2.5 particles been decreased effectively, but also the dust emission concentration is controlled below 10 mg/m³ as well as over 95% of the acid fog removal rate and remarkable achievement on Hg control. WESP has been put into operation successfully or is being constructed in some power plants in China. The monitor data show that the removal rate of PM_2.5, SO₃ and Hg is about 85%, 70% and 60% respectively. If WESP is installed in the 200-GW coal-fired generating units in the key pollutant control regions of Beijing—Tianjin—Hebei area, Yangtze River Delta and Pearl River Delta, 638 thousand tons of PM_2.5 can be reduced annually.

Feasibility Analysis of Three-Phase Circulating Fluidized Bed for Ammonia Decarbonization

HU Kang-tao, LIU Jing-hao, YANG Hai-rui, LEI Xiu-jian

2013, 46(11):  66-71.  DOI: 10.11930/j.issn.1004-9649.2013.11.66.5

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The gas-liquid-solid three-phase fluidized bed is widely used in petrochemical, electrochemical and biochemical processes. Compared with the traditional three-phase fluidized bed, the features of gas-liquid-solid circulating fluidized bed include operation simplicity, large inter-phase contact area, uniform gas-liquid mixture, good heat and mass transfer effect and easy temperature control. Therefore, it can be one of the potential reactors for ammonia decarbonization in coal-fired power plants. Based on the tests of three-phase circulating fluidized bed, the ammonia decarbonization technology with three-phase circulating fluidized bed acting as reactor is simulated and analyzed in Aspen Plus environment. The feasibility of the technology is also discussed.

Research and Analysis on Multi-Variety Filter Media for Flue Gas Purification of Coal-Fired Boilers

XIU Hai-ming

2013, 46(11):  72-77.  DOI: 10.11930/j.issn.1004-9649.2013.11.72.5

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In this paper some kinds of frequently used filter media for coal-fired boilers are introduced, together with the analysis on its structure and properties, to demonstrate the importance of mutual matching between the flue gas condition and filter media. Based on domestic coal situation, a series of experimental data and extensive engineering experience, the limitation of single filter media under different working conditions is illustrated, and then the adaptability of filter media to flue gas conditions is studied and analyzed to provide reference for reasonable selection of filter media. The paper also emphasizes on the PTFE based heat-resistant and anti-corrosion filter media to highlight the necessity of reasonable choice of filter media under poor working conditions. The development of those two filter media will accelerate the progress of the domestic electrostatic-fabric integrated precipitator and fabric filter technologies.

Research on Denitration Electricity Pricing for Coal-Fired Power Plants

JIANG Chun-lai, YANG Jin-tian, XU Yan-ling, SONG Xiao-hui, WANG Yan-chao

2013, 46(11):  78-83.  DOI: 10.11930/j.issn.1004-9649.2013.11.78.5

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From the view point of externality internalization theory and breakeven analysis theory, the model of denitration electricity pricing is established consisting of fixed cost, variable cost and reduction of pollutant charge. Through extensive investigations on the operation of the denitration installations equipped in 103 existing thermal generating units totaling 43 000 MW, main factors contributing to the denitration cost are summarized, including the installed capacity, the denitrification rate, the construction period and the coal type. Moreover, the denitration cost of SCR and SNCR techniques for different time periods and different installed capacities is calculated. It is concluded that the price of 0.010 yuan/(kW·h) and 0.012 yuan/(kW·h) can be carried out for newly built power plants with SCR techniques and active power plants respectively, while the price of 0.006 yuan/(kW·h) should be adopted for all the power plants with the SNCR techniques. The conclusion may be of great importance to improve the policy for denitration electricity pricing.

New Energy

Power System Economic Dispatch Containing Wind Power and Electric Vehicle Battery Swap Station

GAO Ya-jing, ZHAO Kai-xuan, ZHANG Zhan-long, LIANG Hai-feng

2013, 46(11):  84-88.  DOI: 10.11930/j.issn.1004-9649.2013.11.84.4

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Based on an analysis of the wind power and electric vehicle development, it is proposed to regard the battery swap stations as energy storage power stations and use grid dispatch to provide reserve for the power systems containing wind farms. Through prediction of wind power output and the battery swap station’s usable capacity, a new economic dispatch model is proposed in this paper with consideration of wind power and battery swap stations and the model optimization strategies are advanced. The particle swarm optimization (PSO) method is adopted to solve the model. The correctness and effectiveness of the model and algorithm are verified via a case study.

Researches on Internal Interferences of Harmonics Between DFIGs in Wind Farms

YUAN Zhi, WANG Wei-qing

2013, 46(11):  89-93.  DOI: 10.11930/j.issn.1004-9649.2013.11.89.4

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DFIGs with many power electronic equipment have been widely used in wind farms, which will cause harmonics. Especially, some reconnected-to-grid wind generators after maintained and repaired will cause the internal harmonic interferences with other wind generators in different working conditions. According to the theory of instantaneous reactive power and wind power generation, power flows and harmonic interferences between DFIG-based wind power generators in sub-synchronous condition and hyper-synchronous condition are studied and simulated by Matlab. The result shows that the internal harmonics are just caused by the power flows between the generators in different conditions, and the increase in the number of wind generators will exacerbate the harmonic interferences.

Impact of Floating Characteristics on Load of Wind Turbine Tower Base

DU Jing, XIA Zong-chao, JIN Xin, HE Yu-lin, XIONG Hai-yang

2013, 46(11):  94-99.  DOI: 10.11930/j.issn.1004-9649.2013.11.94.5

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Simulation techniques are applied to study the impact of floating characteristics on tower base load performance. In this paper, the floating platform and the wave load are taken into account in the established wind turbine model to formulate the floating wind turbine model. Finally, by taking the NREL 5 MW baseline wind turbine, the performance of typical loads of floating wind turbine and fixed wind turbine are simulated by virtue of FAST software package and corresponding results are compared. The research outcome shows that the floating characteristics have significant impact on the load fluctuations as well as the load limits of tower base. The comparison between the typical conditions of the two kinds of wind turbines indicates that the distribution of limit loads of floating wind turbines is more regular than that of fixed wind turbines, and the cause of this regular distribution is also analyzed.

Research and Verification of LVRT Control Techniques for Direct-Drive Wind Turbines

ZHENG Xiang-yu, SHEN Wei-cheng, LI Cheng, LIU Xiu-liang, LI Zhen

2013, 46(11):  100-104.  DOI: 10.11930/j.issn.1004-9649.2013.11.100.4

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With large-scale wind power integration in the power grid, the new grid codes for wind power integration require the wind turbines to have the capability of low voltage ride through(LVRT). For direct-drive wind turbine units, the DC bus chopper resistance is applied to limit the over-voltage in the current transformer when voltage falls, and an improved current control strategy is adopted to restrain the over-current. In this way, the LVRT operation of a permanent magnet synchronous generator (PMSG) is achieved. In this paper, the design of the chopper resistance is optimized based on the mathematic model of the grid side converter (GSC) and an improved current control strategy is proposed to regulate the over current of the GSC under grid voltage drop. In the end, the LVRT capability is tested on a 1.5 MW permanent magnet synchronous generator wind turbine to validate the correctness of the proposed design techniques.

Parameter Optimization of SVM Based on Improved PSO and Its Application in Wind Speed Predictions

ZHU Xiao-yan, ZHANG Jin-hui, FU Shi-peng, ZHU Xiao-xun

2013, 46(11):  105-108.  DOI: 10.11930/j.issn.1004-9649.2013.11.105.3

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For accurate prediction of short-term wind speeds in a wind farm, a new SVM (support vector machine) predicting method based on improved PSO(particle swarm optimization) is proposed, which is designed to improve the self-learning ability and social learning ability of the particle swarm algorithm by bettering its learning factors, consequently making the PSO more conducive to converge to the global optimal solution and to find a better and more accurate parameter values to minimize the error of support vector machine prediction. The testing results show that compared with the conventional PSO-SVM and SVM prediction, the improved PSO-SVM method is more accurate in prediction result and has lower errors.

Modeling Analysis of the Downtime of Wind Turbines During Trial Operation Period

ZHANG Mu-yong, RUI Xiao-ming, HUO Juan

2013, 46(11):  109-112.  DOI: 10.11930/j.issn.1004-9649.2013.11.109.3

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Grid-connected wind turbines are of large single outdoor mechanical and electric equipment, and the mean downtime(MDT) is an important indicator reflecting the reliability of the unit. For estimating the MDT during the trial operation period, a Weibull distribution- based method was proposed. By taking a wind farm in Qingdao city of Shandong province for downtime case study, which has 14 direct drive permanent magnet wind turbines of 1.5 MW, a Weibull distribution-based downtime model was established through excluding the suspected abnormal-data by Boxplots test and testing the revised data by Weibull probability paper. By intercepting the downtime data of 14 units in trial operation from December 2012 to March 2013, the upper MDT bound of point, bilateral interval and unilateral interval was estimated by the model. Based on the calculation results, the causes of the downtime were analyzed and some advises were proposed for reducing the unit downtime during the trial operation period.

Generation Technology

Performance of Direct Air-Cooled Condenser Under Windy Conditions and Its Influencing Factors

GAO Pei, ZHANG Xue-lei

2013, 46(11):  113-118.  DOI: 10.11930/j.issn.1004-9649.2013.11.113.5

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The environmental wind has significant effects on the heat transfer efficiency of direct air-cooled condensers. By way of the example of a 300-MW direct air-cooled condenser, the models of the air-cooled island and the heat exchanger units are built for numerical analysis. The effects of the environmental wind on the heat transfer efficiency of the air-cooled condenser are studied, and the dominant factor contributing to the reduction of the efficiency under windy conditions is found out. The result shows that the air inlet temperature at the edge of the heat exchanger units is greatly influenced by the environmental wind due to the hot air recirculation and the backward flow; the air inflow of the heat exchanger units on the upwind side is also seriously affected by the environmental wind since there is a negative pressure zone existing that lowers the performance of the fan. The decrease of the air inflow due to the fan performance degradation is the major factor affecting the performance of the air-cooled condenser.

Analysis on the High-Frequency Vibration Characteristics of Static and Dynamic Adjustable Axial Fan

CHEN Min-sheng

2013, 46(11):  119-123.  DOI: 10.11930/j.issn.1004-9649.2013.11.119.4

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The guide blades of one axial fan with combined static and dynamic adjustment have been cracked up repeatedly due to heavy vibrations. Through assembly tests, gas exciting tests, hammer tests, reinforcement tests and characteristic analysis, the cause of fan vibration is figured out. By way of comprehensive tests, the problem of fan bearing vibration is eventually solved. In addition, the technical improvement measures and solution outlines for the fan casing vibration are proposed, which provides a reference for dealing with the same type of vibration problem.

Impact and Reform of Area of Governing Stage Nozzle on Unit Performance

LI Xiu-ping, MIAO Cheng-gang, NIU Zhi-jun, ZHU Xiao-ling

2013, 46(11):  124-128.  DOI: 10.11930/j.issn.1004-9649.2013.11.124.4

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Generally, the heat consumption rate will be 3% to 7% higher than the designed value when the unit is operated at the range of 50%~80% of the rated load. Aiming at the low efficiency issue under partial loads, the causes of the sharp decrease of unit thermal efficiency are analyzed. Through comparison between theoretical analysis and field testing data, it is figured out that the low efficiency is mainly attributed to the increase of throttling loss of the main steam valve as the load is reduced. The technical outline for designing the area of the first-stage stationary blades is then proposed. In addition, the necessity and feasibility of improving the area of governing stage nozzles for existing units are presented with the implementation schemes put forward. Through practical operation the improvement is proved to be successful.

Review and Perspective of Integrating Wind Power into CHP Power System for Peak Regulation

LV Quan, CHEN Tian-you, WANG Hai-xia, LV Yang, LIU Rao, LI Wei-dong

2013, 46(11):  129-136.  DOI: 10.11930/j.issn.1004-9649.2013.11.129.7

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During the winter heating season in the northern China, many cogeneration units are incapable of peak regulation due to the demand of heat supply, which leads to abundant curtailments of wind power. In this paper, it is proposed that cogeneration plants can participate in regulation of curtailed wind power through decoupling the constraint of“power determined by heat”. The operation mechanism, technical characteristics and available scopes of peak regulation by cogeneration units are introduced. Moreover, the application and economic efficiency of this peak regulation mode are forecasted. Finally, the main topics of peak regulation by cogeneration units regarding power plants, power grids and national policies are discussed for future studies.

Analysis on X20CrMoV121 Steel After Long-Time Aging

LI Liang, XIE Jing, WANG Peng

2013, 46(11):  137-141.  DOI: 10.11930/j.issn.1004-9649.2013.11.137.4

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It is of great significance to analyze the material status of high-temperature parts in service as well as its security status and life loss. It is good to the safety operation, reasonable arrangements for unit maintenance cycle and maintenance cost reduction, etc. In order to investigate the safety status and service life of equipment, elongation tests, microstructure analysis and high-temperature lasting strength tests on the final superheater and final reheater tubes made of X20CrMoV121 steel were conducted in one thermal power plant after 12 000-h service. The results show that compared with the original tubes, the strength of the tubes in service is getting lower and the crystal grain of precipitation phases is becoming larger and rounder. In addition the substructure appears in martensite laths and the dislocation density declines apparently. However the high-temperature permanent strength is still higher than the designed value. Comprehensive analysis concludes that although certain aging occurs to some extents after 12 000-h operation, the tubes can still satisfy the requirements of safe operation under the designed working conditions.

Information and Communication

Study on Service Tracking Model of Smart Substations Based on IEC 61850 Standard

GE Ya-chuan, YIN Jun

2013, 46(11):  142-145.  DOI: 10.11930/j.issn.1004-9649.2013.11.142.3

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The service tracking model defined in the second edition of IEC 61850 standard is analyzed and studied. The logical node class, common data class, functional constraint, data objects and data attributes related to service tracking model are briefly described in this paper. Taking the access service tracking for buffered report control block as a case study, the paper introduces the application of the service tracking model, including its working flow, service features, objectives. The study on the service tracking model will provide a theoretical basis and method for solving the problem of abnormal information interactive in digital substation.

Application of Microwave Relay Technology in Interim Communication of Power Transmission Engineering

WU Fei-long

2013, 46(11):  146-149.  DOI: 10.11930/j.issn.1004-9649.2013.11.146.3

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In order to solve the problem that the OPGW cannot meet the time requirement for joint debugging of protection equipment when being connected to a new substation, a microwave relay telecommunication is proposed, in view of the limitations of various interim communication schemes. Through building up a hybrid communication link by a couple of SDH microwave equipment and existing OPGW, this technology opens a temporary channel to meet the time requirement for joint debugging of protection equipment. The application of this technology in several power transmission engineering projects shows that it can effectively solve the time problem of OPGW connection and joint debugging of equipment and has a broad application prospects.

Power Planning

Multistage Comprehensive Evaluation of Urban Power Distribution Network Planning

MA Li, ZHANG Jian-hua, LIU Nian, LIU Wei, SHOU Ting

2013, 46(11):  150-154.  DOI: 10.11930/j.issn.1004-9649.2013.11.150.4

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Existing researches of the comprehensive evaluation of urban power distribution network planning focus mainly on the power grid of the planning target year, ignoring other planning years. So, a comprehensive multistage evaluation method for distribution network planning is proposed. Firstly, based on existing research results, an evaluation index system, involving the superior power resources level, network structure level, load supply capacity and equipment technology level, is built. Secondly, according to the actual regional situation and development goals of the distribution network, the ideal evaluation index values are set as the comparative objects for the current situation of the distribution network and planning schemes. Finally, the whole process of the comprehensive evaluation of the distribution network planning are presented based on AHP-TOPSIS( analytic hierarchy process and technique for order preference by similarity to an ideal solution). The feasibility and effectiveness of the proposed method are verified by a case study of an actual distribution network planning schemes for an example region.

Role and Prospect of Pumped Storage Power Stations in China

CHENG Lu, BAI Jian-hua

2013, 46(11):  155-159.  DOI: 10.11930/j.issn.1004-9649.2013.11.155.4

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The current installed capacities of pumped storage power stations and their role in power system are analyzed. Under the new situation that clean energy are developing fast and power transmission scale is constantly expanding, the role of pumped storage power stations in different regional power grids is discussed. According to the related national planning, with consideration of the mid-long term power demand situation, the pumped storage station resources, the prophase works and the development policy, the development prospect of pumped storage stations in the future twenty years in China is predicted.