Table of Content

10 August 2016, Volume 49 Issue 8

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Power System

Research on Key Joints of 750 kV Concrete Filled Steel Tube Substation Truss Structures

ZHANG Guangping, XI Zenghong, GONG Liang, WANG Shuping, YANG Junfen, YANG Chao

2016, 49(8):  1-6.  DOI: 10.11930/j.issn.1004-9649.2016.08.001.06

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As a reasonable structure in mechanical properties, the concrete filled steel tube(CFT) structure generally has considerable economic value. To promote construction of CFT structure in 750 kV substation, and provide theoretical basis for construction of the Qiaowan 750 kV substation in Gansu, experiment study on three kinds of key connection joints is performed. Test results show that all joints used in project have high strength reserve and ductility, and the failure form are all satisfied with‘strong connection and weak bar’ design principle. It is can be widely applied in 750 kV CFT substation after summarization on engineering projects.

Research on Lightning Overcurrent of Substation and Its Influence on Device Sensors

ZOU Zhenyu, CHEN Bo, YU Yuming, ZHAO Junlong, CHEN Changtao, LI Kejun, LOU Jie

2016, 49(8):  7-11.  DOI: 10.11930/j.issn.1004-9649.2016.08.007.05

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The lightning of substation will affect the insulation safety of electrical equipment, and the strong EMI caused by the discharge process may damage the sensitive devices of the secondary equipment. A model is established for the lightning overcurrent of substation by using EMTP/ATP software. In the simulation, the amplitude of overcurrent and overvoltage of each equipment are obtained. Then, by taking the GIS partial discharge sensor as an example, the EMI influence on the sensors during lightning is simulated and analyzed by using MagNet software. The result shows that the overcurrent caused by lightning can produce a maximum induced voltage of 323V in serious cases and may seriously damage the sensors.

Power System Fault Diagnosis Based on Rough Set and Petri Network Optimized by BP Algorithm

GAO Zhengzhong, GONG Qunying, LIU Longji, LI Shiguang, ZHAO Lina

2016, 49(8):  12-16.  DOI: 10.11930/j.issn.1004-9649.2016.08.012.05

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In order to improve fault diagnosis process, a power grid fault diagnosis method is proposed based on rough sets and Petri network combined with Back-Propagation algorithm. Firstly, the rough set theory is applied to grid fault symptoms for deduction of minimum decision table from the redundant fault information. Then, diagnosis rules are extracted and optimal Petri net model is created. Petri net’s parallel processing ability is used to implement efficient fault diagnosis. BP algorithm is adopted to train the weight values of Petri network parameters. The results of grid instance show that the proposed model can find fault zone accurately, and has good adaptability, speediness and fault tolerance.

Research on Voltage Sags Influence of High Voltage Level and Bulk Experiment Base Access to Power System

ZHANG Zhiqiang, TANG Xiaojun, LI Xiaojun, WANG Xiaoyang, ZHANG Bo, LV Pan

2016, 49(8):  17-20.  DOI: 10.11930/j.issn.1004-9649.2016.08.017.04

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An electric switch experimental study base, which operates on the highest voltage level domestically, will access to Gansu 330 kV Tianshui power grid. The main experiments in the base are switch dynamic and thermal current experiments and transformer short circuit experiments. During experiments, the continuous short circuit will cause severe voltage sags of Gansu power system. In order to evaulate effects of voltage sags to power system, appropriate standard is first selected to check experiment base accessing. Based on actual data of Gansu power grid, simulation of voltage sag value is performed for different experiment projects and experiment capacities. The impacts of voltage sags to power system protection settings, power plant auxiliary machine and surrounding sensitive load equipment are analyzed according to simulation results and national standard. The results can be used to support security assessment of large-capacity switch electrical short-circuit experiment base accessing to system.

Impacts of Operation of 750 kV Yili-Kuche Power Transmission Line on Security and Stability of Xinjiang Power Grid

LI Xiaojun, ZHANG Zhiqiang, ZHENG Chao, LV Pan, ZHOU Zhuan, CHANG Xiqiang, WANG Heng

2016, 49(8):  21-25.  DOI: 10.11930/j.issn.1004-9649.2016.08.021.05

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The 750 kV Xinjiang Yili-Kuche power transmission and transformation project will form the Tianshan western section of a large ring network after completion and being put into operation in 2016. A calculation and analysis is made on the Xinjiang power grid before and after operation of the Yili-Kuche Line in terms of power flow distribution, safety and stability level, short-circuit current level and small disturbance stability. And the effects of the operation of Yili-Kuche line on the transmission capacity of key sections are studied. Calculation results show that the operation of Yili-Kuche line will realize inter-supply between north and south of Xinjiang power, and complementation between hydropower and photovoltaic power; lower the Isolated running risk of Yili region after tripping of Yili-Wusu line; improve the angle stability and small disturbance stability of Xinjiang power grid and upgrade the outbound power delivery capacity of Yili and Kuche region.

Application Research on Assembly Foundation of Transmission Lines

CHENG Yongfeng, ZHENG Weifeng, ZHANG Qiang, LU Xianlong, DING Shijun

2016, 49(8):  26-30.  DOI: 10.11930/j.issn.1004-9649.2016.08.026.05

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As a type of tower foundation which is light in weight for a single structural unit and easy in assembly on site, the assembly foundation has found application in trassmission lines in the desert and frozen soil area. Due to its limitation in some aspects, the assembly foundation, however, has not been studied comprehensively. Based on a review of the releveant information of the assembly foundation at home and abroad, and a study of its appliacation in electric power industry and emergency repair and full-scale tests, an comprehensive analysis is made on existing technical problems in application of the assembly foundation in transmission line and some design optimization proposals are put forward for its more extensive application.

Study of Joint Bearing Capacity With Slope Change on Tower Consist of Steel Tubes　and Angles

JU Yanzhong, WANG Haichao, ZHANG Chuchu, WANG Dehong, BAI Junfeng, WANG Xinying

2016, 49(8):  31-35.  DOI: 10.11930/j.issn.1004-9649.2016.08.031.05

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In order to study joint feature with slope change on tower consist of steel tubes and angles, static full-scale tests on two same size joint with different slope and loading modes are performed. Analysis is carried out on loading process, bearing capacity and failure mode. Both node failure modes are gusset plate buckling in tests indicating that gusset plate is weak area. A three-dimensional solid model of joint with slope change on tower consist of steel tubes and steel angles are built by using finite element software ABAQUS. A parameter analysis is conducted to investigate main factors affecting bearing capacity of joint with slope change. The results show that all failure modes of joint are instability of gusset plate on compression side and gusset plant is weak area. According to parameter analysis result, in a certain range, the bearing capacity increases as gusset plate thickness increased. Every 2 mm increase of gusset plate thickness increases capacity by 5% to 9%. When the thickness is increased to a certain limit, the capacity is improved by 30% and gusset plate is fully utilized.

Seismic Performance Analysis of Steel-Reinforced Concrete Combined Shearwall Structure of High Voltage Side Valve Hall in ±800 kV Converter Station

GU Qun, ZHANG Mi, ZHANG Yuming, CHANG Wei, YING Jie, SHEN Weihua

2016, 49(8):  36-40.  DOI: 10.11930/j.issn.1004-9649.2016.08.036.05

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The Steel-Reinforced Concrete Combined entire shearwall Structure, Steel-Reinforced Concrete Combined t-shaped section shearwall Structure and other Steel-Reinforced Concrete Structure of High Voltage Side Valve Hall in ±800 kV Converter Station are compared by seismic response spectrum analysis, elastic time-history analysis and elastic-plastic time-history analysis. The results show that longitudinal section firewall with T seismic wall hybrid structure whose transverse firewall disconnected to Valve Hall has high bearing capacity and good deformation in elastic and elastic-plastic stage which meets standard requirements. The torsion effects of other three structural models are remarkable and sensitive to disasters including earthquakes, especially strong earthquake which easily leads to brittle structure failure or collapse. The analysis results can provide technical guidance for structural selection of future UHVDC Converter Station Valve Hall.

Sensitivity Study of Structural Enlarged Base Parameters on Uplift Bearing Capacity for Digged Foundations

LU Xianlong, ZHENG Weifeng, TONG Ruiming, CUI Qiang

2016, 49(8):  41-44.  DOI: 10.11930/j.issn.1004-9649.2016.08.041.04

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Base enlargement is a widely used method to improve uplift performance of digged foundations of transmission towers. The portion of concrete amount of enlarges base increases with the increasing of embeddment and bell diameter of tower foundation. Furthermore, base enlargement is difficult and dangerous during construction. Taguchi method is applied to investigate effect of structural parameters of enlarged base on uplift load bearing capacity of the digged foundations. The selected structural parameters are embedment to bell diameter ratio, angle of the conical surface against the vertical and shaft diamter. A orthogonal array is selected and 9 digged foundations are designed according to Taguchi method with those three factors and corresponding three levels. Thirty-six field tests are performed at four sites in Gansu province including three Gobi gravel sites and one loess site. Analysis of signal-to-noise(S/N) ratio and analysis of variance(ANOV) methods are used to evaluate testing results. The results show that soil strength is the decisive factors for ultimate uplift capactiy of digged foundations for transmission towers. The uplift performance improves when each of three structural parameters mentioned above increases. However, sensitivities of these factors are different for the foundations embedded in different grounds. In Gobi gravel, the senstivities in ascending order are embedment to bell diameter ratio, shaft diamter, and angle of the conical surface against the vertical. In loess soil, senstivities for the same sequence are in descending order.

Research on the Ultimate Transmission Length of Power Cables

ZHANG Lei, ZHENG Xinlong, GAO Zhen, PENG Weilong, LIN Yong, XU Zheng

2016, 49(8):  45-49.  DOI: 10.11930/j.issn.1004-9649.2016.08.045.05

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Different from overhead transmission lines, the power cables have large shunt capacitance, which leads to large charge capacitive current and high open end overvoltage under no-load operation condition. Based on the positive sequence model for power cables, a steady state analytical method is proposed to study the ultimate transmission length of power cables. The method proposed in this paper can calculate the ultimate length of lossy cables with different end voltages. The study shows that the open end overvoltage has little limitation on the cables with a length under 200 km. The open end overvoltage is less than 1% for the cable with a length under 40 km, which is in good agreement with the field test. The capacitive charge current is the bottleneck for limiting the transmission length of cables. However, the calculation results show that when the compensation ratio is set at 0.3, a 100-km long cable, much longer than the 60-km long cable now in common use, can have a power factor of 0.94, indicating that the 100-km super-long cable is theoretically feasible.

Determination of Metal Elements in Transformer Oil with ICP-AES after Microwave Digestion

LIU Songtao, ZHANG Jing, CHEN Chuanmin, JIA Wenbo

2016, 49(8):  50-53.  DOI: 10.11930/j.issn.1004-9649.2016.08.050.04

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The pretreatment of transformer oil samples must be carried out before the process to determine the metal elements in transformer oil. In order to improve the efficiency of sample treatment, the three-step microwave digestion method is established. Using HNO3-H2O2 as the digestion acid and the method of ICP-AES in combination with the three-step microwave digestion, the Fe and Cu contents in the oil sample are measured. The results show that the RSDs of the two element contents are kept below 2% with the recoveries of standard addition between 98.4% and 101.2%. The analytical results obtained by the three-step microwave digestion method are compared with those by the China electric power industry standard(DL/T 263-2012 )． Verified by t-test at the confidence level of α=0.05, no significant difference is observed between the two methods. This method is simple, rapid and accurate, which is of great significance to detect the metal elements in transformer oil.

Short-Term Power Load Forecasting Based on Improved SVR

QIAN Zhi

2016, 49(8):  54-58.  DOI: 10.11930/j.issn.1004-9649.2016.08.054.05

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In conventional SVR prediction algorithm, parameters including RBF kernel function parameters, insensitive coefficient and punish coefficient are selected manually. The random selected parameters lead to performance uncertainty. The initial parameters of artificial fish algorithm greatly influence optimization performance. By applying particle swarm optimization and chaotic theory to conventional artificial fish algorithm, the global optimization ability can be improved. Detailed analysis are performed are testing data of improved SVR load prediction model. Results show that the proposed method has better prediction accuracy and good engineering application value.

Fault Location Algorithm Based on Current Calculation for Parallel Transmission Lines on Same Tower

DING Jianzhong, BAO Youli, LI Cheng

2016, 49(8):  59-63.  DOI: 10.11930/j.issn.1004-9649.2016.08.059.05

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Fault location on double circuit transmission circuit is easily impacted by fault type and not well researched. A fault location method based on current calculation is proposed. The proposed method can be used in both single loop and cross line fault type. Based on distributed parameter PI model of PI equivalent circuit, the proposed method utilizes current on both terminals to locate fault. The fault location equation is simple and easily solvable with less impact on system operation mode and system parameters. PSCAD fault simulation and Matlab numerical results show that the proposed algorithm is reliable, practical and accurate. It is not easily affected by transition resistance and fault types.

New Energy

Real Time Prediction of Wind Power Based on Relevance Vector Machine

YANG Mao, ZHANG Qiang

2016, 49(8):  64-68.  DOI: 10.11930/j.issn.1004-9649.2016.08.064.05

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The volatility and randomness of wind have significant impacts on the wind power prediction. Accurate and reasonable prediction can ensure a reliable, continuous and stable system operation. An ultra-short term wind power prediction method is proposed based on relevance vector machine. The relevance vector machine is a probability learning model based on the Bayesian theory, and compared with the support vector machine(SVM), it has the advantage of sparse probability model and minor kernel function calculation. Then, based on an analysis of the rolling multi-step prediction model, a short-term wind power prediction model of relevance vector machine is developed. The model has been implemented for wind power prediction to a lot of wind farms in Jilin province, and the testing results show that the proposed model can effectively improve the prediction accuracy and is valuable for engineering implementation.

Analysis of Sparse Fourier Transform for Vibration Signal of Wind Turbine Gearbox

ZHAO Hongshan, GAO Duo, ZHANG Jianping

2016, 49(8):  69-73.  DOI: 10.11930/j.issn.1004-9649.2016.08.069.05

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The on-line spectrum analysis for vibration signal of wind turbine gearbox demands fast algorithms. In order to improve the speed of the algorithm, the spectrum analysis with Sparse Fast Fourier Transform (SFFT) algorithm is proposed in this paper. First, the SFFT algorithm is used to leverage the window function to filter vibration signal. Then, after the Fourier coefficients being hashed, the k largest (in magnitude) coefficients of the Fourier Transform of vibration signal can be estimated by locating and estimating methods. The SFFT algorithm has a simple structure and a sub-linear runtime in the signal size n. It has been verified through analyzing the vibration signal of wind turbine gearbox that the SFFT algorithm has a faster performance than FFT algorithm in on-line spectrum analysis.

An Opportunistic Maintenance Strategy for Offshore Wind Turbine Based on Accessibility Evaluation

FU Yang, XU Weixin, LIU Lujie, ZHAO Hua, PANG Liping

2016, 49(8):  74-80.  DOI: 10.11930/j.issn.1004-9649.2016.08.074.07

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Maintenance of offshore wind power plants is known to be expensive and costly and limits the development of offshore wind power industry to a certain extent. In order to solve this problem, the paper proposes an opportunistic maintenance method, which can function both correction and prevention. Considering the impact of weather conditions on the maintenance activities, this method applies the Markov method and dynamic time window to represent the weather conditions, and the index used to evaluate the maintenance accessibility is then proposed. During the investigation, the Monte Carlo method is applied to simulate the component failures and select the appropriate cycle. Taking the minimum expectation cost as objective function, the opportunistic maintenance is optimized by considering the strategy of the perfect maintenance and the strategy of both perfect and imperfect maintenance. An offshore wind farm is taken for simulation case study, and the simulation results indicate that the opportunistic maintenance considering both perfect and imperfect strategies is more economical, which proves the effectiveness of the method.

Research on Energy Management Strategy for the Islanded Mode of Micro-Grid

FENG Jianghua, ZHAO Xin, SU Zhan，

2016, 49(8):  81-86.  DOI: 10.11930/j.issn.1004-9649.2016.08.081.06

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Energy management is the core for controlling islanded micro-grid system. The system structure of an islanded micro-grid is designed according to the real situation of a border post. Besides, the energy management strategy based on hybrid energy storage system is also investigated. Firstly, the overall structure of energy management system is designed. Then, the power allocation and SOC adjustment are studied in details. The simulation result has verified the effectiveness of the proposed energy management strategy.

Research and Analysis on Current Control Methods of a Single-Phase Grid-Connected Inverters for Photovoltaic Modules

QIN Rui, ZHEN Wenxi, CHEN Yicong, MA Xiping, YANG Jun, WEI Bo

2016, 49(8):  87-92.  DOI: 10.11930/j.issn.1004-9649.2016.08.087.06

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The basic current control methods of a single-phase grid-connected inverter for photovoltaic modules are studied, and an inverter control strategy of dual close loop with proportional resonant (PR) controller and grid voltage fed forward is presented in this paper. Based on a theoretical analysis of the PR controller, the parameters are designed. In order to study the effect of the control method for improving the output power quality, a simulation model of the grid-connected inverter control system is established, and the PI control and PR control method are respectively analyzed under three scenarios including grid with nominal voltage, grid with voltage mutation and grid containing low harmonics. The result of this study is significant for developing the control system of single-phase grid-connected inverters.

Research on the Recovery Voltage of Wind Farm Tie Line during Open-Phase Operation

WANG Yuelin, LI Fengting, XIN Chaoshan

2016, 49(8):  93-98.  DOI: 10.11930/j.issn.1004-9649.2016.08.093.06

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In view of the open-phase running case after single-phase grounding protection action, the voltage characteristics of the fault phase and its influence factors are analyzed. Besides, the impedance characteristics of wind power and conventional energy are studied. The recovery voltage model of fault phase is developed in PSCAD. And the effects of fault properties, wind turbine types, wind power output, tie line arrangement modes as well as voltage levels are simulated and studied. The research results show that the wind farm, quite different from conventional energy, has a positive and negative sequence impedance much higher than the zero sequence impedance when tie line open-phase runs, which results in the increase of sound phase current, and consequently leads to the inductive coupling voltage much higher than that of the conventional energy. The research results can provide a theoretical basis for the adaptive sequential reclosing of wind farm tie line and improve the success rate of reclosing.

A Multi-Layer Optimization Method of Price Incentive Demand Response for Improving Photovoltaic Power Accommodation Rate of Microgrid

MA Jian, DI Kaili, LI Rui

2016, 49(8):  99-105.  DOI: 10.11930/j.issn.1004-9649.2016.08.099.07

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The microgrid with high percentage of photovoltaic(PV) generation has the problem of PV power accommodation. Reasonable adjustment of power load can help to improve the PV accommodation rate, and the price-incentive demand response is an effective means to adjust the power load. Based on the time-of-use (TOU) price incentive demand response, an novel method is proposed to improve the PV accommodation rate of microgrid through optimizing the TOU price to reasonably adjust the power load. After analyzing the multivariate nonlinear property of the model, a multi-layer optimization model is established in this paper, which considers both the economics of power generation and the PV accommodation rate. The accommodation ability of microgrid for PV power can be improved through hierarchical iterative solution by the improved simulated annealing algorithm and the mixed integer programming. Numerical simulation results show that this method can significantly improve the PV power accommodation rate without increasing the cost of demand side, and consequently improve the overall economic performance of microgrid.

Technology and Economics

Research on Regional Differences of Carbon Dioxide Emissions Performance Embodied in China’s Industrial Electricity Consumption

HOU Jianchao, GUO Juan

2016, 49(8):  106-109.  DOI: 10.11930/j.issn.1004-9649.2016.08.106.04

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Taking a cue of the theory of carbon dioxide emissions embodied in international trade, this paper calculates provincial carbon dioxide emissions embodied in China’s industrial electricity consumption by using provincial energy balance table in the period of 1995-2013. Based on the method of the Theil index，the regional differences of carbon dioxide emissions performance embodied in China’s industrial electricity consumption are measured and the overall differences are decomposed. The results show that the overall differences of carbon dioxide emissions performance embodied in China’s industrial electricity consumption, which are mainly caused by the internal differences of a region, tend to increase. Since 1995, the contribution of the eastern region’s internal differences to the overall differences tends to decrease and the contribution of the middle & western region’s internal differences to the overall differences tends to increase. The contribution of regional differences to the overall differences tends to decrease. The causes for the differences and their changes are analyzed and the corresponding policy recommendations are given.

Comprehensive Self-Determined Evaluation of Electric Power Development Level Based on IOWA Operator

KANG Yi, ZHOU Yifan, BING Huanshuai, HU Wei, GUO Jian

2016, 49(8):  110-115.  DOI: 10.11930/j.issn.1004-9649.2016.08.110.06

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A comprehensive evaluation method of electric power development level is proposed in this paper based on objective self-determined evaluation. The evaluation index system contains 6 second-order indexes and 31 third-order indexes. The general and complete index system can provide a comprehensive description of the electric power development level from multiple perspectives. An IOWA operator-based objective self-determined evaluation method is used to establish a linear weighted model for evaluation of the electric power development level. Furthermore, a case study is conducted to make a comprehensive evaluation of the electric power development level in typical provinces in China, which has proved the validity of the proposed index system and evaluation method.

Method for Allocating Fixed Cost by Considering Time-of-Use Flow Tracing and Peak Load Responsibility

CAO Fang, CAI Yue, LI Chengren, YOU Peipei

2016, 49(8):  116-120.  DOI: 10.11930/j.issn.1004-9649.2016.08.0116.05

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Allocation of transmission grid’s fixed cost is one of the most important processes in the tariff setting, which is directly related to the rationality and justification of the pricing policy. According to the characteristics of high voltage transmission grid’s fixed cost, an allocation method of transmission grid’s fixed cost is proposed in this paper by considering the timely flow tracing and peak load responsibility. Based on the flow tracing, the maximum usage ratio of each line is calculated for peak and valley period, which forms the basis of transmission fixed cost allocation. The method follows the ideal of peak load responsibility. Meanwhile, the peak-valley price mechanism is reflected in the transmission link. The rationality of the method is verified by using IEEE30-bus system. Compared with the traditional flow tracing method, the proposed method is more reasonable in reflecting the usage of the transmission fixed cost by load.

Estimation of Receiving-End Grid Power Peaking Cost and Compensation Mechanism Based on Large-Proportion Renewable Energy Transmission

BAI Hongkun, ZHOU Maiyu, YIN Shuo, JIN Liang

2016, 49(8):  121-125.  DOI: 10.11930/j.issn.1004-9649.2016.08.121.05

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Tianshan-Zhongzhou UHVDC Project is the first UHVDC project in Xinjiang for outbound power transmission. With a designed annual transmission capacity of 44 billion kW·h, it will play an important role in energy resources optimization for a large area. The Tianshan-Zhongzhou UHVDC Transmission Project is built for transmission of both thermal and wind power in Xinjiang. Different proportion of the thermal and wind power has different influences on the operation of Henan power grid. The magnitude of power transmission during Xinjiang power valley will influence the load peaking operation and increase the peaking cost of Henan power grid. By taking this project as an example, a study is made on estimation of receiving-end grid power peaking cost and compensation mechanism based on large-proportion renewable energy transmission, which is expected to provide a reference for formulating relevant electricity price policy.

Information and communications

Multi-Dimensional Evaluation Model for Distribution Communication Network Planning by Considering Index Relationship

GUO Fang

2016, 49(8):  126-129.  DOI: 10.11930/j.issn.1004-9649.2016.08.126.04

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A multidimensional evaluation model for distribution communication network planning by considering the index relationship is proposed in this paper, in which an evaluation index system is built based on the characteristics of distribution communication network and relevant national technical specifications. The weights of the indexes are determined according to analytical hierarchy process. The theory of Grey Relational Analysis is applied to the model as to determine the fuzzy evaluation matrix. As a result, the problem for experts to subjectively assign weight coefficients and membership functions is solved. A regional distribution communication network planning scheme is chosen for modeling, and the feasibility and effectiveness of the proposed method is verified.

An Efficient Cognitive Radio Communication Algorithm for Electric Power IOT Information Control

ZHAI Shaolei, LI Bo, ZHANG Linshan, TANG Biao

2016, 49(8):  130-134.  DOI: 10.11930/j.issn.1004-9649.2016.08.130.05

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The application of Internet of Things(IOT) in smart grid is the development result of information and communication technology to a certain stage, which will effectively integrate communication and power system infrastructure resources. Cloud transmission is a highly efficient and interference-immune way for broadcasting communication. In order to realize the on-line monitoring of transmission lines and improve the efficiency of electric power communications, a novel cognitive communication method is proposed for power IOT in this paper, which applys the cloud transmission technology in the cognitive radio communication. In the communicaiton scheme, a secondary link is superimposed onto the Orthogonal Frequency-Division Multiplexing(OFDM) in the frequency domain as to support the fast transmitter- receiver (Tx-Rx) interaction to improve the efficiency and reliability of the interconnected control.

?Energy Conservation and Environmental Protection

Research and Practice of Flue Gas Mercury Reduction Technology in Coal-Fired Power Plants

SHI Xiaohong, ZHANG Yi, ZHAO Rui, CHEN Chuangshe

2016, 49(8):  135-139.  DOI: 10.11930/j.issn.1004-9649.2016.08.135.05

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In order to master the technology of flue gas mercury emission control in coal-fired power plants, the Sanhe Power Plant conducts the study on flue gas mercury emission reduction. In the study, four kinds of technologies are used on flue gas mercury removal. They are adding calcium bromide(CaBr2) to the as-fired coal, injecting activated carbon before the flue gas enters the electrostatic precipitators(ESP), adopting the co-mercury removal technology with CaBr2 and ordinary activated carbon, and modifying the fly ash before it enters the ESP. The study results show that all the four technologies have good mercury removal efficiency, among which the efficiency of adding CaBr2 to feed coal reaches as much as 77.5% with the lowest operating costs; while that of co-mercury removal technology with CaBr2 and ordinary activated carbon can even reach 92.6% but with the highest operating costs.

Experimental Study on the Usage of Carbide Slag as Desulfurization Agent for Wet Flue Gas Desulfurization System

LI Xinghua, NIU Yongjun, ZHANG Liqing

2016, 49(8):  140-143.  DOI: 10.11930/j.issn.1004-9649.2016.08.140.04

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Using carbide slag to replace limestone as desulfurization agent is a new technology turning wastes into treasures. Take the example of the 600-MW unit of a power plant, where limestone was previously utilized as desulphurization agent. The experimental study on the usage of carbide slag as desulfurization agent is carried out. The effects of different pH values on the desulfurization efficiency and the gypsum quality are analyzed respectively, and the economic performance of carbide slag and limestone as desulfurization agent are compared as well. The study results show that the performance of carbide slag as a desulfurization agent is satisfactory with the corresponding cost greatly reduced. However, the water contents may rise in the byproduct gypsum, which makes it necessary to enhance the pretreatment of the desulfurization agent and optimize the design of gypsum dewatering system.

Application of Ultra-Low Emission Technical Roadmaps of Coal-Fired Power Plants

LI Bo, , ZHAO Jinyang, LV Junfu

2016, 49(8):  144-147.  DOI: 10.11930/j.issn.1004-9649.2016.08.144.04

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There are a variety types of coal in China, of which those with medium/high ash and medium/high sulphur contents have been widely used in large coal-fired power plants. Under the background of increasingly stringent pollutant emission standards, it is absolutely necessary to explore and analyze the technical roadmaps of ultra-low emission adaptable to these types of coal. This paper conducts the analysis on the applications of ultra-low emission techniques in three coal-fired power plants fueled by medium/high ash and medium/high sulfur coal. The results show that, it is possible for such plants to make the NOx, SO2 and dust emissions reach the ultra-low emission standards by selecting appropriate technical roadmaps. In this paper the advice is also provided on how to choose the ultra-low emission technical roadmaps for coal-fired power plants using medium/high ash and medium/high sulfur coal.

Diagnosis of Typical Operation Faults of SCR Flue Gas Denitrification System in Coal-Fired Power Plants

HE Jinliang, JIN Lipeng, LU Chengzheng, SONG Yubao, LIANG Junjie, FANG Zhaojun

2016, 49(8):  148-153.  DOI: 10.11930/j.issn.1004-9649.2016.08.148.06

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The typical operation faults of SCR denitrification system include insufficient agent supply, uniformity of ammonia injection and poor quality of its automatic control in coal-fired power plants. To solve these problems, taking a SCR flue gas denitrification system in a power plant for instance, the following solutions are presented: (1) improving the quality of steam used for heating up the liquid ammonia and cleaning up the impurities in the ammonia system; (2) optimizing the automatic control logic for ammonia injection; (3) optimizing the hot ammonia injection adjustment. The test results show that all these faults are eliminated after correction and optimization in this power plant. Now the quantity of agent supply changes with the unit loads, the automatic control system for ammonia injection operates normally, and the concentrations of NOx and ammonia-slip at the reactor outlet reach the designed requirements and keep stable in the operation. The security and economy of the denitrification system has been improved.

The Formation and Control of SO3 in Coal-Fired Flue Gas

GUO Yanpeng, DI Huajuan, PAN Danping, YANG Linjun

2016, 49(8):  154-156.  DOI: 10.11930/j.issn.1004-9649.2016.08.154.03

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The SO3 in coal-fired flue gas is harmful to the operating conditions in coal-fired power plants, the environment and the human health. To effectively reduce the SO3 content in flue gas, based on the in-depth analysis on the sources of SO3 and the formation of sulfuric acid mist, the control measures employed both at home and abroad to inhibit the formation of SO3 and reduce its emissions are presented. Meanwhile, the pros and cons of the technologies are analyzed. With the technology analysis, the denitration operation condition optimization and the wet electrostatic precipitator are considered the better ones in effectively controlling SO3.

Research Progress of CFD-Based SCR Flue Gas De-NOx Technology for Coal-Fired Power Plants

ZHAO Dazhou, LIU Peiqi, HE Sheng, ZHENG Wenguang

2016, 49(8):  157-161.  DOI: 10.11930/j.issn.1004-9649.2016.08.157.05

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Although the selective catalytic reduction(SCR) flue gas denitrification technology has been widely used, some problems still keep happening occasionally such as the wearing and the blockage of the catalyst, the uneven mixing of reducing agent with flue gas, etc. With the CFD technology the scenarios from multiple differentaspects can be simulated, which is helpful to resolve these problems. In this paper, the literatures on the progress of CFD-based SCR flue gas denitrification technology are summarized. On the basis of sorting out the literatures, the application of computational fluid dynamics CFD software in the simulation of SCR flue gas denitrification is expounded, which mainly includes the simulations of flow field,concentration field, gas-solid two-phase flow and chemical reactions. It is concluded that reasonable and uniform flow fields are the essential to the economic and security operation of the whole SCR system. The integrated simulations of SCR model coupled with detailed reaction kinetics model, furnace combustion model combined with SNCR model will capture more attention in the future studies.

Retrofit of Energy Saving on Secondary Air Fan of a 135-MW CFB boiler

GUO Xinhai, LI Jianfeng, WANG Guiliang, LENG Jie, LV Lei, QI Yueqin, LV Hongqi, LV Junfu

2016, 49(8):  162-166.  DOI: 10.11930/j.issn.1004-9649.2016.08.162.05

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The CFB boiler is developed rapidly due to its outstanding characteristics suitable to the circumstances in China. However, compared to the pulverized coal boiler, its special combustion style makes it necessary to adopt the high-pressure primary and secondary air fans, which leads to high auxiliary power consumption rate. In order to improve the efficiency of the secondary air fan of a 135-MW circulating fluidized bed (CFB) boiler, the technical retrofit is conducted on the fan by installing small blades between the original blades to enhance its efficiency. The comparison between the fan performance test data before and after the retrofit shows that the flow and the efficiency are improved significantly after the retrofit; the lower the speed is, the larger margin of the fan performance is achieved.

Genration Technology

Study on Layered Slagging Mechanism at Platen Superheater during High Alkali Coal Combustion

TAN Houzhang, WEI Bo, WANG Xuebin, WANG Yibin, RUAN Renhui, HU Zhongfa

2016, 49(8):  167-171.  DOI: 10.11930/j.issn.1004-9649.2016.08.167.05

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The reserves of Zhundong(ZD) coal in China are huge. However, due to its high contents of Na and Ca, slagging and fouling are serious on the surface of the platen superheater at the furnace outlet area(at the flue gas temperature of around 1 000 °C). In this paper, to explore the mechanism of the slagging in the high alkali coal combustion process, study is conducted on the slag samples from the platen superheater of a 350-MW boiler. With the study, an obvious layered structure is observed in the slag, and the element compositions and compounds in each layer are very different. This is because in the developing of slags, with the deposite temperature rising, different physical-chemical reactions happen in the ash particles. Through the classification and the detailed analysis on the compounds in each layer, the formation mechanisms of those different compounds are proposed.

Simulation on Air-Fuel Distribution in Low NOx Tangential Firing Boilers

LIU Fuguo, WANG Haichao

2016, 49(8):  172-177.  DOI: 10.11930/j.issn.1004-9649.2016.08.172.06

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To optimize the air-fuel distribution in the furnace of low NOx tangential firing boilers, the model for monitoring the furnace air and fuel distribution is established, in which the relationships are obtained between the local excess air coefficients in the primary combustion or the separated over fire air(SOFA) zones and the wind box-furnace outlet pressure discrepancy, the secondary air baffle opening, as well as the mill air-fuel flow and other parameters. Based on the model, a simulation system for the furnace fuel and air distribution is developed to improve the air-fuel distribution of a practical operating boiler. The results show that the improved air and fuel distribution is helpful to reduce the energy consumption of the forced draft fan and improve the coal powder burnout.

Optimization on the Startup Process of 600-MW Supercritical Unit

YU Dezhong

2016, 49(8):  178-180.  DOI: 10.11930/j.issn.1004-9649.2016.08.178.03

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To meet the requirements of frequent and quick startup of units by the power grid, the startup procedures are adjusted by optimizing the operation pattern of two 600-MW supercritical units of a power plant, which includes moderate opening of high-pressure regulating valve, optimization of steam parameters and condenser vacuum, etc. Through the implementation of the optimized procedures, the safety and the success rate of the unit startup are improved and the startup duration is shortened, which not only meets the requirements of the power grid, but also produces good economic benefits for the power plant.

Security Evaluation of Outlet Temperature Increase of Medium-Speed Pulverizer and Its Impact on Boiler Operation

ZHANG Liangli, SHEN Li, TAO Jun, WANG Zhun, QIU Lichun

2016, 49(8):  181-184.  DOI: 10.11930/j.issn.1004-9649.2016.08.181.04

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In the practical operation of the milling system, cool wind is mixed to regulate the pulverizer outlet temperature, therefore, properly increasing the pulverizer outlet temperature is helpful to improve the system economic performance. From the aspects of the CO concentration in the coal pipe, the lubricating oil temperature of the bearings and the wall temperature of the burner nozzles, the security is quantitatively evaluated after the outlet temperature of the ZGM medium-speed pulverizer is raised. Based on the secure operation of the pulverizer, the impacts of the temperature increase on the milling performance and the boiler combustion are studied, which concludes that there should be a limit on the temperature increase to ensure the secure operation of the milling system.