Table of Content

05 July 2017, Volume 50 Issue 7

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Column of Power Market & Reform

Key Issues for Pilot Reform of Incremental Distribution Network Business

HUANG Liming, YANG Su, TU Junming, QU Haoyuan

2017, 50(7):  1-6.  DOI: 10.11930/j.issn.1004-9649.2017.07.001.04

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The deregulation of incremental distribution network investment business is the focus and difficulty of the new round of electric power system reform, which has attracted attentions of all sectors of society. with the country’s 106 pilots identified, the deregulation of incremental distribution network investment business proceeds from the top-level design to the implementation phase. In order to promote the smooth implementation of the pilot reforms, several key issues for deregulation of incremental distribution network investment business are studied in depth in this paper based on a deep interpretation of related policies, including deregulation mode, pricing mechanism, the way that the power generation enterprises to participate in the pilot reforms, and the supporting mechanism. Some relevant suggestions are proposed. The research results can provide a reference for decision-making in formulating schemes and specifications of the incremental distribution network investment pilot reforms.

Recent Developments and Key Issues of China’s Retail Electricity Market

MA Li, ZHANG Xiaoxuan, YANG Su, XUE Song, QU Haoyuan

2017, 50(7):  5-9.  DOI: 10.11930/j.issn.1004-9649.2017.07.005.05

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With the issuance of the document“Several policies about further deepening electric power system reforms”and relevant supporting documents by the China’s state government, the retail electricity market reform is accelerating. The retail electricity companies are being set up in succession by generation enterprises, industrial parks and social capitals, and the competition in retail electricity market is appearing gradually. The development of China’s retail electricity market is systematically analyzed, and the future development trend is studied with combination of the international experience in terms of competitive landscape, transactional model, business development and competition means. Finally, some solution measures are proposed to such problems arising in the development of retail electricity market as the development of retailers, the implementation of end-user’s option right, last resort power supply service and retail electricity market supervision. The research results can provide a reference for the development of retail electricity market in China.

Market Mechanisms for Wind Generation in ERCOT Market and the Inspiration for China

WANG Xuanyuan, MA Li, QU Haoyuan

2017, 50(7):  10-18.  DOI: 10.11930/j.issn.1004-9649.2017.07.010.09

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Texas is the state with the largest installed wind power capacity in the US. The ISO of Texas, ERCOT(Electric Reliability Council of Texas), was once faced by challenges of integrating large-scale wind power. In 2009, ERCOT’s wind curtailment reached 17%. Through grid investment and Texas’s Nodal Market putting online, wind curtailment has dropped significantly in ERCOT system, with average annual rates below 2% in recent years. This paper mainly focuses on market mechanisms and operational improvement that ERCOT has adopted to integrate wind resources. In the end, this paper proposes suggestions for China’s electricity market reform and development on wind power integration.

Operation System of Active Distribution System Considerring Active Demand and Sale Market

LIU Xiaojie, SU Xiaolin, YAN Xiaoxia, WU Fujie, ZHANG Chao

2017, 50(7):  19-27.  DOI: 10.11930/j.issn.1004-9649.2017.07.019.09

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With the increase of demand response resources and the introduction of bilateral interaction in the power sale market, the active distribution system and corresponding operation framework is required. Based on the analysis of characteristics of various generalized demand response resources, and with combination of the future power sale market features such as pluralistic players and diversified modes, the aggregation agent of consumer resources is proposed to integrate the demand response ability within user agent areas, and to respond to the operation and scheduling demand of distribution network. A three-layer architecture and operation organization system is developed of active distribution system consisting of power sale companies, aggregation agents and response consumers, which is suitable for smart grid construction and power market development requirements. And the function, profit model and synergetic mechanism of main entities in the system are analyzed and designed.

Electricity in Europe: A Historical Perspective

Jean-Paul BOUTTES, François DASSA

2017, 50(7):  28-32.  DOI: 10.11930/j.issn.1004-9649.2017.07.028.05

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Europe was at the forefront of energy and electricity 20 years ago. In the 1 990 s electricity was abundant and affordable, and Europe was home to large industrial firms that were leaders in their sector and world-class power utilities. Today, Europe is losing ground. Europe now pays more for electricity than the main countries it competes with, its industrial fabric is shrinking, and its power companies are experiencing difficulties. Why this reversal would happen? Since 1 990 s, the bottom-up approach to building the European power system was replaced by a top-down logic. A single model was applied to all countries. Electricity issues were addressed using competition and environment to the Commission. The abstract and not very“systemic”vision adopted over the past two decades or so has yielded very disappointing results in terms of carbon emissions, competitiveness and industrial development. Taking a look back at history will not only help understand changings, but also gives some guidance for the future.

Analysis of Power Direct Trade Organization Under New Round of Electricity Reform

YAN Yu, LI Gengyin, LI Guodong, ZHOU Ming, PANG Bo, LI Zhu

2017, 50(7):  33-37.  DOI: 10.11930/j.issn.1004-9649.2017.07.033.05

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Since implementation of the new round of power institutional reform, the pace of power market construction is continuously accelerating. Based on an introduction of electricity direct trading practices within the business region of SGCC in 2016, 4 typical inter-provincial electricity direct trading organized by Beijing Electric Power Trading Center are introduced, which include Yindong electricity direct trading, Zhejiang electricity direct trading, Ximeng-Shandong UHV AC electricity direct trading and Jing(Beijing)-Jin(Tianjin)-Tang(Tangshan) region electricity direct trading. An analysis is made on the existing problems in electricity direct trading organizations in China, including complicated demands of all parties, distempered trading rules, serious inter-provincial barriers and poor market awareness of market players. Finally, some specified recommendations are given on trading rules construction, breaking inter-provincial barriers and strengthening market awareness.

New Energy

Solar Curtailment of Centralized PV Station and Its Countermeasures

LU Liang, DING Kun, ZHOU Shiyuan, HE Shi'en, WANG Ningbo

2017, 50(7):  38-42.  DOI: 10.11930/j.issn.1004-9649.2017.07.038.05

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The reasons for solar power curtailment of centralized PV station is analyzed from aspects of peak capacity, transport capacity, absorptive capacity and equipment operation. Calculation methods of solar power curtailment based on benchmark PV station and irradiance data restoration are proposed. Calculation is performed on practical operating data by using proposed methods. The application of two algorithms are also described. Finally, measures for promoting PV power consumption and reducing abandoned PV power are presented from aspects of national policy, development planning, dispatching and consumptive market in order to promote a healthy, sustainable and stable development of centralized photovoltaic.

Management Mode of Integrated Construction of Electric Vehicle Charging Piles and Municipal LED Facilities

ZHANG Shixiang, LI Linfeng

2017, 50(7):  43-48.  DOI: 10.11930/j.issn.1004-9649.2017.07.043.06

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Low voltage direct current is required as energy supply by both municipal LED facilities and electric car charging piles. An integrated construction model is proposed to improve lagging of charging piles construction.The benefits and shortcomings of three existing charging piles construction model, namely government-driven, power grid-driven, and electrical vehicle manufacture-driven, are compared. A private capital-driven mode is then introduced. Combined with practical situation of China's charging pile development, a four-party joint investment mode for the construction of charging piles is proposed, which includes government guidance and support, electric vehicle manufacturers, power grid companies and private capital investment.

A Review of Optimization Planning and Designing of Distributed Energy Systems

REN Hongbo, QIU Liuliang, WU Qiong, CAI Qiang

2017, 50(7):  49-55.  DOI: 10.11930/j.issn.1004-9649.2017.07.049.07

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To exhaust the high-efficient, energy-saving and environmental benefits of distributed energy systems, the optimal planning and design are of vital importance. In this study, based on the development and evolution process of distributed energy systems, the corresponding studies at home and abroad are reviewed and discussed with the respect to the optimization of distributed combined heat and power system, distributed hybrid energy system, and distributed energy internet. Finally, the current research status is analyzed and the possible research direction is proposed.

Accommodating Capability Analysis and Comprehensive Assessment Method of Large-Scale New Energy Areas Interconnected

GAO Che, NIU Dongxiao, MA Ming, WANG Ningbo, GAI Xiaoping

2017, 50(7):  56-63.  DOI: 10.11930/j.issn.1004-9649.2017.07.056.08

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With the rapid increase of installed capacities of the renewable energy, the UHVDC power transmission grid based on long-distance regional interconnection will greatly promote the new energy accommodation in larger regions. In this paper, according to the trend of large-scale and large-scope allocation of renewable energy sources in China, an analytical model is developed of the accommodation capabilities in the sending and receiving ends of inter-regional power grids, and a comprehensive evaluation method is proposed of the flexibility of the power systems in the sending and receiving ends from the perspective to satisfy the net-load climbing demand of power systems. By taking two trans-region HVDC systems in China for case study and combined with HVDC's flexible adjustment operation modes, the scenario analysis is carried out according to different HVDC's adjustment operation modes, and it is demonstrated by real cases that the HVDC transmission channel has better economic and social benefits when following the transmission curves of renewable energy output characteristics in the sending end. It is concluded that the proposed model and method can provide an effective mode for comprehensive evaluation and production simulation of interconnected power grids integrated with large-scale renewable energies.

Research and Design of Grid Energy Dispatch Model Based on Demand Response

LIAO Bingjie, LI Ruiqi

2017, 50(7):  64-68.  DOI: 10.11930/j.issn.1004-9649.2017.07.064.05

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The conventional method to satisfy grid peak load requirement is increase peak regulation installed capacity. However, short sustention period of electricity peak load leads to very low economic efficiency with this method. The stochastic and intermittent characteristics of new energy source also bring new challenges to energy dispatch. A user stimulus-response behavior model is built to coordinate and optimize resources on both supply and demand sides. The model considers roles of supply-side and demand-side incentives on power grids containing new energy resources such as wind power. The composite control strategy on demand side can effectively complement and enrich the demand response theory in wind power optimization scheduling. The model is tested with regional wind power forecasting and summer typical daily load data. Testing results show that proposed model can flatten load curve and reduce grid operation cost effectively.

Generation Technology

Technical Study on Three-Staged Pipe-Blowing Method Used in Double Reheat Unit

WANG Lin, LIU Hui, LIU Chao, GAO Jinghui, ZHAO Zhidan, WANG Hongyv, MENG Yingqi

2017, 50(7):  69-73.  DOI: 10.11930/j.issn.1004-9649.2017.07.069.05

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Due to the higher thermal efficiency and the lower pollutant emissions, the double-reheat cycle technology is getting moreapplied in the industry.. Therefore, the steam blowing process for the new units with double-reheat cycle calls for urgent study. In this paper, an ultra-supercritical 660 MW double-reheat boiler is taken as the study object. Based on the routine one-staged and two-staged pipe-blowing techniques, the three-staged pipe-blowing with pressure-reduction steam is proposed in accordance with the arrangement of the boiler heating surfaces. The results of the target plate test show that the number of the flushed spots are less than 5 and the diameters of the spots are all smaller than 0.5 mm, which completely meets the requirements of the national codes. The three-staged pressure-reduction pipe-blowing method, which produces good blowing quality, can provide practical reference for subsequent units with double reheat technology.

Study and Application of Improving Load Response Capacity with Superheaters Stored Energy for Coal-Fired Power Plant

HE Jun, YAN Bo, PENG Daogang, ZHANG Xiaoliang

2017, 50(7):  74-78.  DOI: 10.11930/j.issn.1004-9649.2017.07.074.05

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There are a lot of energy storage in the pipes of the superheaters at power plant. Experimental data showed that unit power generation and the main steam pressure change quickly through changing superheaters stored energy. The paper proposes a coordination control method including the boiler heat stored energy feed-forward. The results show that the proposed method can effectively suppress the throttle pressure fluctuation.Thus, the method significantily accelerate the load response ability, as well as enhances peak load regulation ability of coal-fired power plant.

Numerical Simulation on Effects of Peak-Valley Combustion Mode on Furnace Combustion Characteristics

LÜ Hongkun, TONG Jialin, ZHANG Ming, XIONG Jianguo, YING Mingliang, QI Xiaojuan, YU Bin

2017, 50(7):  79-84.  DOI: 10.11930/j.issn.1004-9649.2017.07.079.06

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In order to better reduce the NO_x emission of coal-fired boilers, it is necessary to optimize the conventional low NO_x combustion mode. The numerical simulation method is employed for an ultra-supercritical boiler with low NO_x combustion technology. The impacts of the peak-valley combustion mode on the temperature, the concentration field, the burnout rate and the slag volume are studied and compared with the conventional low NO_x combustion mode. The simulation and analysis results indicate that while keeping the excess air ratio of both the reduction zone and the burnout zone constant, the peak-valley combustion mode outperforms the conventional low-NO_x combustion mode in low NO_x combustion and has little effect on the combustion, the gas temperature, the bottom slag volume and the burnout rate. Under an optimal condition, the NO_x concentration in furnace exit cross section is reduced by 12%.

Impact of the Running Modes of Coal-Fired Units on Energy Consumption in in-Depth Peak Load Cycling

ZHANG Liangli, LI Min, ZHOU Xiaomeng, LI Yijin, YANG Jianguo, ZHAO Hong, SHI Haoxun

2017, 50(7):  85.  DOI: 10.11930/j.issn.1004-9649.2017.07.085.05

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Based on the test results of the net coal consumption of a 4×600 MW power plant, it is proposed that a critical time exists in the long-term peak load cycling when the low-load operation is switched to the two-shift operation. The economics of the two operation modes are analyzed. It concludes that the economic benefits will become more significant when there are more units with lager capacities and longer peak regulation running time in a power plant. Along with the load rate of power grids decreasing, the in-depth peak load cycling does not occur only at nights. Consequently, the two-shift operation deserves more attention for its benefits in energy conservation and emissions reduction.

Boiler Control System Based on Dynamic Linear Regressive Predictive Algorithm and Burning State Observer

GUO Yiwen, WANG Lin, GENG Linxiao, GAO Haidong, GAO Lin, CHENG Guodong, JIN Guoqiang

2017, 50(7):  90-95.  DOI: 10.11930/j.issn.1004-9649.2017.07.090.06

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Aiming at the problem of large main steam pressure fluctuations caused by the burning process lag in the boiler control system of the thermal power generator units, a new boiler control system is proposed. The auto-regressive predictive control algorithm and the burning state observer are used to correct the required fuel volume from the aspects of pressure variations and the burning process, and the corrected signal is introduced into the boiler control system as feedforward to increase the stability of main team pressure control. Using PLC as the central controller,the loading simulation at 5%MCR and 10%MCR is conducted on the APROS simulation model of a 300 MW thermal power unit according to the AGC specifications. The simulation results show that the new boiler control system can not only accelerate the load response speed, but also ensure the better tracking performance of main steam pressure control. It improves the responding capabilities and qualities of AGC and is valuable for practical applications.

Numerical Simulation on Resistance Characteristics of the Low Temperature Economizer Installed in Flues in the Coal-Fired Power Station

DU yuying, ZHAN Yang, SUN Yongbin, LV Junfu, QIAO Yanqi, PENG Hongwen, LIU Chuang, XIE Yuhui

2017, 50(7):  96-101.  DOI: 10.11930/j.issn.1004-9649.2017.07.096.06

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To more accurately predict the flow resistance of the low temperature economizer in complex flow field in engineering designs, this paper proposes a method to simulate the resistance characteristics by using the resistance coefficient of the low temperature economizer obtained by direct simulation of the parts of the fin tube bundles and the porous media model.Based on this method, the resistance characteristics of a low temperature economizer installed in a coal-fired power station is studied. It is found that the bent narrow exit_and_entrance flue type will affect the total pressure distribution of the low temperature economizer, but it has relatively samller effects on the resistance of the low temperature economizer. The fin tube structure and the macro structure of the low temperature economizer are the main reasons for the formation of its high resistance. The error between the predicted value and the measured value of the resistance is small, which indicates that the numerical simulation method proposed in this study is able to meet the needs of engineering design.

Energy Conservatino and Environmental Protection

Application of SO₃ Removal with Alkaline Sorbent Injection in Large Capacity Coal-Fired Power Plants

GAO Zhipu, HU Dong, ZHANG Zhigang, GUO Tingting, WANG Haigang, CHEN Kunyang

2017, 50(7):  102-108.  DOI: 10.11930/j.issn.1004-9649.2017.07.102.07

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In order to solve the problems of air heater fouling, duct corrosion, ammonium bisulfate adhering to ESP and plume opacity to meet the strict SO₃ emission standards in the future, the SO₃ removal technology with alkaline sorbent is studied in this paper. The technical characteristics of the dry sorbent injection are compared with those of the slurry injection. In addition, the applicable scope of different alkaline sorbents is studied, and the reserves and prices of the mineral resources in China are also investigated. Then the technical and economic characteristics of the sorbent injection system are analyzed on a 600 MW coal-fired unit that fires the coal with 1% sulfur content. The results show that the technology of alkaline sorbent injection is an effective way to solve SO₃ pollution and related issues. All sorbents injected in suitable positions can meet the requirements of SO₃ removal efficiency. The injecting location and the economy are vital for determining the technical route. The operation cost of the slurry injection system is about 2.9 times of that of the dry sorbent injection system in China. The dry sorbents such as Ca(OH)₂ and MgO are recommended, Ca(OH)₂ is better to be injected at the inlet or outlet of the air heater and MgO to be injected at the SCR inlet or outlet.

Multi-Objective Optimization on CFB Boiler Desulfurization and Denitrification Systems

WANG Qi, BAI Jianyun, WANG Xinfeng, WANG Li

2017, 50(7):  109-114.  DOI: 10.11930/j.issn.1004-9649.2017.07.109.06

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In order to minimize the cost of desulfurization and denitrification while meeting the pollutant discharge standards and achieving economic operation, an in-service 300 MW CFB boiler pollutant control system is taken as the study object. Based on the study on the major factors that affect the desulfurization and denitrification results, a system model is established with the SO_x and NO_x emission concentration, the desulfurization and denitrification efficiency, and the major influencing factors as the constraints and the economic performance as the objective function. By solving the optimization model, an optimal solution is obtained which both satisfies the constraints and minimizes the raw material consumption and the electricity consumption. The method, which meets the new environmental standards and enables the system cost to be the lowest at the same time, provides new ideas for the energy saving of the CFB boiler pollutant removal system.

Study on Blank Test of Low-Concentration Particulate Matter Gravimetric Testing for Coal-Fired Power Plants

LIU Hanxiao, YAO Yuping, LI Jianguo

2017, 50(7):  115-121.  DOI: 10.11930/j.issn.1004-9649.2017.07.115.07

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The flue gas ultra-low emission has been fully implemented in coal-fired power plants. Therefore, it is imperative to further improve the particle testing technology at low concentrations. In this paper, through field measurements, and in consideration of the related provisions in ISO 12141-2002, the study on the blank test of particulate matter testing at low concentrations is carried out for coal-fired power plants. The blank testing and comparison on imported and domestic cartridges indicate that the imported quartz filter cartridge outperforms the domestic one. In addition, the comparison study of blank test between the integrated sampling head and the membrane is also conducted. It is observed that the disassembling operation can increase the fluctuation amplitude of the blank test deviation. Then based on the study results, the onsite testing is performed. At last, the reasonableness and necessity of blank test are discussed for the establishment and revision of the relevant standards.

Study on Layout of Wet ESP, FGD Absorber and Stack in Indirect Natural Draft Cooling Tower

ZHAO Li, YANG Yingzhe, CHEN Lei, YANG Lijun

2017, 50(7):  122-126.  DOI: 10.11930/j.issn.1004-9649.2017.07.122.05

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To take full advantage of the internal space of the air cooling tower, reduce land occupation and save budget, the layout plan of Four-in-One indirect cooling tower is proposed regarding the steam turbine cooling system with indirect natural draft cooling system, in which the desulfurization absorber tower, the wet electrostatic precipitator(ESP) and the stack are integrated together into the cooling tower. Furthermore, based on the numerical simulation, the heat transfer performance and thermal performance of the cooling tower are studied. Therefore the recommended minimum anti-freezing water flow and the anticorrosion area of the inner wall of the cooling tower are obtained.

The in-Depth Water Conservation and Zero Discharge Technology for Gas Turbine Power Plants

ZHANG Zhiguo, HU Dalong, WANG Jing, YU Yaohong, XU Zhen

2017, 50(7):  127-132.  DOI: 10.11930/j.issn.1004-9649.2017.07.127.06

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In order to meet the increasingly stringent environmental policy requirements, it is of great significance to carry out the research on in-depth water conservation and zero discharge technologies for gas turbine power plants. In this paper, the water intake, discharge and consumption, as well as the water balance in a gas turbine power plantare analyzed . Based on the situation that the gas turbine power plant does not have a system of desulfurization, coal handling and deslagging that is able to consume high salinity waste water, an in-depth water conservation and zero discharge method is proposed. First, by improving the make-up water quality for the circulating system, the concentration rate is increased, and the water intake and discharge are substantially reduced. Second, the circulating sewage and reverse osmosis concentrate are concentrated by stages to reduce the high salinity waste water. At last, the small amount of high salinity waste water are evaporated and crystallized. Thus, the waste water zero discharge is achieved.

Experimental Study on Improving the Concentration Ratio of Circulating Water by Processing Make-up Water with Nanofiltration in Coal-Fired Power Plants

LI Le, MA Zhihuan, ZHAI Shaojing, LI Yajuan, WANG Zhengjiang, ZHAI Jiaming, JIANG Xiaoyan

2017, 50(7):  133-137.  DOI: 10.11930/j.issn.1004-9649.2017.07.133.05

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Large quantities of water are required in thermal power plants, of which primarily the circulating cooling water accounts for over 70% of the total water consumption. To explore the operating control technique of the circulating cooling water with high concentration ratio, the make-up water treatment with nanofiltration (NF) processing is studied and tested in a power plant with the processing capacity of 18 m³/h. The test results show that at the recovery of 90%, the desalination rate is about 70%, while the removal rate of divalent ions, such as Ca²⁺, Mg²⁺ and SO₄^2-, is over 80% and the COD of yielding water is not more than 2 mg/L. Then, the NF processed water is used in the static scale inhibition test and the coupon corrosion test. The test results show that the concentration ratio of the circulating water can be maximized by as much as 33.98 times, and at this time, the circulating water system can operate at high concentration ratio with zero cooling tower discharge, which exhibits remarkable water-saving effect and environmental benefits.

Cause Analysis and Countermeasures of Ammonia Injection Valve Blockage in Coal-Fired Power Plant Denitration System

JIANG Pengwei, GUO Yuefei, NI Ye

2017, 50(7):  138-142.  DOI: 10.11930/j.issn.1004-9649.2017.07.138.05

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In coal-fired power plants, the normal operation state of SCR flue gas denitration system is of great significance to environmental protection. In several SCR denitration equipments of a coal-fired power plant, the ammonia control valves are blocked in the winter, and the equipment has to be shutdown to carry out manual cleaning, which will severely interrupt the normal operation of the SCR system and affect NO_x emissions specified by national standards. Through the analysis on the liquid ammonia quality, ambient temperature, equipment structure and materials, and the ingredients of the blockade, it is found out that the blockage is caused by the mixture of carbon steel rusting on the inner wall of ammonia supply tube and the oily volatile matter in the ammonia Based on the actual situation of the equipment, the problem is entirely solved by virtue of a series of countermeasures such as adjusting the operation mode of the ammonia evaporator, pipeline purging, the structure retrofitting of the ammonia injection valve, and replacing the pipe with the stainless steel material, etc.

The Interpretation of National Standard on Plate-Type DeNO_x Catalysts

LI Qian

2017, 50(7):  143-146.  DOI: 10.11930/j.issn.1004-9649.2017.07.143.04

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The demand of power plant for DeNO_x catalysts has been rising dramatically high over the recent years. However, due to the late start of the manufacturing and application of SCR catalysts in China, the establishment of corresponding standards is also lagged behind. On the basis of the corresponding standards of Europe and the United States, the first product standard GB/T 31584—2015 of plate-type DeNO_x catalyst in China was published in 2015. In order to help the catalyst manufacturers, power plants and independent product testing organizations to better implement and apply this standard, the current situations of the main product standards and testing method standards for DeNO_x catalysts both in China and abroad are introduced. Meanwhile the key technical contents of the newly issued standard Plate-type DeNO_x catalysts (GB/T 31584—2015) are interpreted.

Power System

Study on the Resettlement Modes of Half-Wavelength Tuned Network of Transmission Lines

ZHAO Yongxi, WANG Songfeng, WANG Huaxin, WANG Jian, CHEN Aiyou, XUE Tianshui

2017, 50(7):  147-152.  DOI: 10.11930/j.issn.1004-9649.2017.07.147.06

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When the actual length of transmission line is less than the half wavelength, the manual tuned compensation is needed. However, detailed analysis is needed to determine the appropriate tuned network types. Firstly, based on the existing three types of tuned networks, their respective suitable modes for compensation are investigated. In addition, the installation and distribution mode suitable for each tuned network is discussed. Finally, the overvoltage of each tuned transmission lines is comparatively analyzed. The results show that the reactive power is surplus when distributed compensation is used for capacitor-type tuned network; For PI and T type, the overvoltage level under distributed installation is higher than that under centralized mode, and the overvoltage level is low when line side compensation is used. Therefore, it can be concluded that the C type tuned network is suitable for the distributed compensation, while the PI and T type tuned networks are more suitable for centralized compensation; the three types of tuned networks are suitable for centralized installation on the line side.

Research on HVDC Core Equipment “Factory Overhaul” Maintenance System Construction

HU Siquan, CHANG Yong, LIU Kun, FAN Caiyun, ZHANG Ping, WANG Xiaomin

2017, 50(7):  153-158.  DOI: 10.11930/j.issn.1004-9649.2017.07.153.06

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To ensure that HVDC converter station equipment maintenance management adapts to the fast development of massive HVDC transmission projects operation nowadays and in future, present HVDC converter station maintenance management problems are analyzed in detail. A HVDC core equipment maintenance management system is proposed to achieve professional, intensive, flat and integrated maintenance management. With proposed system, a core equipment factory overhaul maintenance management mechanism is established which focused on the construction and management of routine maintenance center, condition-based maintenance center, emergency repair center, HVDC system simulation center, reliability analysis center and spare parts storage workshop. Compared with existing HVDC equipment maintenance management, the proposed HVDC core equipment factory overhaul maintenance management mode has advantages of effective coordination of human, technical and equipment resources and further maintenance management efficiency and labor productivity improvement to guarantee long-term reliable operation of HVDC system. Research results have significant reference value to construction and maintenance of HVDC equipment.

Research and Project Application of Field Winding Ground Fault Protection System on Brushless Rotating Excitation Generator

WANG Guang, CHEN Jun, ZHANG Qixue, YU Haibo, LIU Le

2017, 50(7):  159-163.  DOI: 10.11930/j.issn.1004-9649.2017.07.159.05

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Regarding present application problems of field winding ground fault protection system (MRET) on brushless rotating excitation generator, a new rotating field winding ground fault protection system scheme is proposed. The system structure and basic principles are discussed in detail. Several key techniques, including injection rotor ground protection, wireless communication technology, auto-adjustability of power frequency and digital protection, are analyzed. The field operation on several generators greater than 300 MW proves validity and reliability of proposed protection system.

Analysis of DC Bias Suppression Method of the Large Transformer's Neutral Series Capacitor and Its Effect on Relay Protection

WANG Ting, ZHANG Kanjun, WEN Bo, CHEN Kun

2017, 50(7):  164-168.  DOI: 10.11930/j.issn.1004-9649.2017.07.164.05

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HVDC power transmission system that works in monopole or bipolar asymmetric operation mode generates neutral current which causes transformer DC magnetic biasing and in turn influences safe and stable operation of transformer and AC systems. Taken a 500 kV substation as example, the capacitor connected in series to transformer neutral can suppress DC biasing. However, it also changes transformer zero sequence and behavior of zero-sequence current relay and distance relay. Theoretical analysis of relay protection is performed and analysis results are verified by simulation. The results show that small capacitor connected in series to the neutral point of station transformer has no influence on relay protection performance.

Position Optimization of Existing and Added Cables Based on Finite Element Method

GUO Ran, NIU Haiqing, WU Juzhuo

2017, 50(7):  169-174.  DOI: 10.11930/j.issn.1004-9649.2017.07.169.06

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The mode of laying power cable in pipes was designed to allow additional cable circuits to meet the future load increase. For different positions of original and additional cables, the temperature field and ampacity are different. It is, therefore, necessary to optimize the positions of original cables and additional ones. A finite element model is built in this paper by taking the 3×4 pipes for laying distribution cables as an example,and the validity of the model is verified by comparing the results of temperature-rise experiments and that of simulation. Based on the model, the positions of the original 6-circuit and 1 additional circuit are optimized based on the lowest conductor temperature of the most serious heating cable under the condition of same ampactiy for all circuits. The simulation result shows that the more scattered the cables are, the more uniform the temperature field is, and the lower the conductor temperature of the most serious heating cable. The optimal position of the additional cable is related to the position of original cables. Therefore, it is suggested that the future additional cables should be taking into account when optimizing the original position of cables.

Optimization of the Bay Resources in Substations based on Hierarchical Model

HU Xiaofei, LI Yuanyuan, SUN Zi'an, ZHANG Shiqiang, JIA Honggang, JIANG Yi

2017, 50(7):  175-179.  DOI: 10.11930/j.issn.1004-9649.2017.07.175.05

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With respect to the contradiction between increasing access requirements of distribution network in urban centers and the limited bay resources in power grid, a bay resource optimization method is proposed in this paper based on hierarchical model. For outer-layer planning, the substation of loads is selected for optimization by taking the balance of the substation capacity utilization as target; For inner-layer planning, the association between load and bays is taken for decision-making by taking the largest number of idle bays as target; and the maximum bay resource utilization is used as optimal scheme for final bay resource allocation scheme. The practical simulation results show that the proposed method has good practicability, and can provide a reference for the planning and construction of urban distribution networks.

Analysis on the High Transmission Tower's Transient Characteristic Caused by Lightning Stroke Considering the Impact of Equivalent Radius

XIONG Junhui, WANG Zhongyi, WANG Peng, LIU Xingting, ZHAO Yang

2017, 50(7):  180-184.  DOI: 10.11930/j.issn.1004-9649.2017.07.180.05

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The transient process caused by lightning stroke to the top of high transmission tower is of great importance in the design of the application of the transmission line, line insulator and arrester. In this paper the existing surge impedance models for transmission towers home and abroad are introduced in brief, to improve the model, on this basis the tower body is divided into different pieces, considering the impact of equivalent radius and then analysis the influence of lightning propagation. Through the contrastive analysis of the segments of the tower, the lighting current waveform, and the amplitude of lighting current, and surge impedance effect on the transient characteristic of the tower, combining theoretical analysis, from which we can find that the subdivision of the tower will reduce the overvoltage and prolong the transient process. The conclusion is available for reference to the design of high transmission tower.