Table of Content

10 November 2016, Volume 49 Issue 11

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Special Contribution

Analysis and Suggestions on Renewable Energy Integration Problems in China

PEI Zheyi, WANG Caixia, HE Qing, WANG Yuefeng, FAN Gaofeng, LIU Lihua, WANG Jingran

2016, 49(11):  1-7.  DOI: 10.11930/j.issn.1004-9649.2016.11.001.07

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Renewable energy integration becomes an increasingly critical issue in China. The amount of curtailed wind and solar energy hit new record in 2015, which mainly happened in the“Three Norths” area of China. Based on abundant data, current situation of renewable energy integration in the“Three Norths” area is analyzed first, and then in-depth analysis of reasons of large amount of renewable energy curtailment in these areas is also performed. Analysis shows that strengthening power grid construction is the solid foundation to solve renewable energy integration issue, and implementing heat and power decoupling is an effective meansure to alleviate renewable energy curtailment. Furthermore, improvement of relevant policies will provide instituional guarantee for renewable energy integration, while both market and planning methods are basic solutions for solving renewable energy integration issues.

Power System

Analysis on Surge Current Characteristics of Electromagnetic Closed-Loop Operation in 750 kV/220 kV Power Grid

LI Shan, LI Wei, CHEN Wentao, HE Dandong, ZHANG Yuan, WANG Jian

2016, 49(11):  8-13.  DOI: 10.11930/j.issn.1004-9649.2016.11.008.06

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It is especially important to study the impact of surge current on electromagnetic closed-loop operation in the EHV power grid. Based on the 750 kV/220 kV closed-loop operation practice of the Xinjiang Bazhou 750 kV substation, a simplified model of surge current is established. The main factors that impact the surge current are analyzed, including voltage difference, phase angle difference and total impedance, and their relations with the surge current are studied. Furthermore, the scheme of closed-loop operation is formulated according to the grid structure of local power system so as to realize the operation. The measured characteristics of surge current are consistent with the theoretical conclusions, which can provide guidance for other grid closed-loop operations.

Analysis on the Time-Dependent Characteristics of ZnO Varistor’s Capacitance after DC and AC Degradation

XU Le, YOU Zhiyuan, HU Yuling, ZHANG Jieru, BAI Yang

2016, 49(11):  14-19.  DOI: 10.11930/j.issn.1004-9649.2016.11.014.06

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In order to study the time-dependent characteristics of ZnO varistor’s microscopic capacitance after AC and DC degradation, a theoretical analysis is made on the parameters which influence the microscopic capacitance of ZnO varistor based on the block model. By applying the AC and DC degradation test on the samples of ZnO varistors with different experimental time, it is found that the macroscopic capacitance tends to decrease firstly and then increase after AC and DC degradation. When the AC and DC degradation time is relatively short, the microscopic capacitance reduces a little compared to the initial value. When the AC and DC degradation time is long enough, the microscopic capacitance substantially increases compared to the initial value. Based on the investigating results, it can be concluded that the time-dependent characteristics of microscopic capacitance are resulted from the releasing process of electron captured by interface state and the thermal failure process of grain boundary layer, which has a certain reference value for studying the degradation properties of ZnO varistor.

Thyristor Valve Synthetic Operational Test of ±800 kV/6 250 A Ximeng-Taizhou UHVDC Project

CAI Licun, CHANG Zhongting, LI Juan

2016, 49(11):  20-24.  DOI: 10.11930/j.issn.1004-9649.2016.11.020.05

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To meet the thyristor valve operation test requirements of the Ximeng-Taizhou ±800 kV/6 250 A project, a new-type synthetic test circuit is built. The main features of the test circuit and the principal problems that need to be addressed are introduced. The main equipment parameters of the synthetic circuit are investigated and used for the operation test of ±800 kV/6 250 A thyristor valve. The test result shows that the proposed synthetic test circuit can meet the operation test requirements of the ±800 kV/6 250 A thyristor valve, and the rationality and reliability of the thyristor valve design are verified.

Research on Electric Contact Calculation and Heating of 500 kV Transmission Line Clamps

BAO Jiankang, GAO Bo, ZHANG Xueqing

2016, 49(11):  25-30.  DOI: 10.11930/j.issn.1004-9649.2016.11.025.06

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In order to solve the clamp breaking problems caused by high operating temperature of 500 kV transmission line clamps, the calculation method of clamp contact resistance is investigated based on the NY-type clamps, and a finite element model of clamp electric contact heating is established with ANSYS to study the relation between the maximum electric contact temperature and the contact pressure and the temperature variation from the internal to external of the clamp. From the studies, it is found that the maximum temperature tends to decrease rapidly first and slowly afterwards with the pressure increase, and the maximum temperature reaches 31.42 ℃ at I=600 A under rated pressure; With the pressure increase, the maximum temperature occurs successively on the electric contact between aluminum plate and bolt, and the electric contact between the aluminums, and the electric contact between aluminum plate and bolt; A temperature difference exist between the internal and external of clamps but their temperature varies consistently, so the external temperature of clamps can present indirectly the operating temperature of clamps. Finally, the calculation method and simulation results are verified by experiments.

Break Fault Diagnosis Method of Grounding Grids Based on Regularization

ZHU Liwei, SHEN Xiaoming, YANG Fan, LIU Xingping, WANG Xiaoyu, LIU Kai

2016, 49(11):  31-35.  DOI: 10.11930/j.issn.1004-9649.2016.11.031.05

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In order to detect break fault of grounding grids, a diagnosis method based on regularization is proposed. This method adds a penalty factor to fault diagnosis function in order to solve ill conditioned problem in reverse fault diagnosis. Experimental results show that proposed method can effectively detect single or multiple break fault in grounding grids, which validate feasibility and effectiveness of proposed method.

Research of High Speed Circuits Signal Integrity of Controller Platform in Power System

GU Zaogen, LI Ning, ZHANG He, XU Jiansong

2016, 49(11):  36-41.  DOI: 10.11930/j.issn.1004-9649.2016.11.036.06

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Signal integrity(SI) of high speed circuits of the control platform for IGBT series valve is analyzed. The PCB impedance calculation is performed to analyze the effects of through hole radius, wiring length and width on signal integrity. The optimized parameters are found after calculation. The experimental results show that it is beneficial to improve the signal quality by optimizing routing parameters. Potential system failure for high speed signal overshoot and ringing phenomenon is also avoided.

Discussion and Practice of Visual Remote Inspection of Transmission Line

JIANG Tao, CAI Fudong, YANG Xuejie, LI Simao

2016, 49(11):  42-45.  DOI: 10.11930/j.issn.1004-9649.2016.11.042.04

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Based on the analysis of problems in traditional image and video monitoring technology on transmission lines, a visual remote inspection method for transmission lines is proposed. Combined with Cloud and Wechat technology, a highly-integrated monitoring device, which is much smaller, lighter, easier to install and more endurable than before, is developed to supervise lines intermittently during inspection. Practices in Zibo State Grid prove the feasibility and efficiency of proposed method.

Prediction Model for Icing Thickness of Power Transmission Line Based on Grey Support Vector Machine

MA Xiaomin, GAO Jian, WU Chi, HE Rui, GONG Yiyu, LI Yi, WU Tianbao

2016, 49(11):  46-50.  DOI: 10.11930/j.issn.1004-9649.2016.11.046.05

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In order to reduce the impact of icing accidents on transmission lines, prediction of icing thickness on transmission lines is very effective in anti-icing work of power grid. A short-term prediction model based on grey support vector machine for icing thickness of transmission lines is proposed. The methods of dirty data elimination and data preprocessing are analyzed. The accuracy and applicability of proposed model are verified by comparison between model predictions and measured data. Predicted maximum ice thickness can provide guidance on monitoring icing condition, early warning and AC/DC ice melting work. Compared with support vector machine (SVM) and generalized regression neural network prediction model, the proposed method has average error of 0.325 mm, and average absolute error of 2.61%, which is suitable for short-term prediction of icing thickness of transmission line. The application of the prediction model can guide the transmission line ice-resistant work in the ice area.

Research on the Converter Valves Charging and Triggering Passive Inversion Test of Xiamen Flexible DC Transmission Project

HU Wenwang, SHI Jiyin, TANG Zhijun, LIN Guodong, DENG Chaoping

2016, 49(11):  51-56.  DOI: 10.11930/j.issn.1004-9649.2016.11.051.06

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In order to ensure the safety of Xiamen flexible DC project converter valves, it is necessary to confirm the correctness of the triggering phase sequence of converter valves before the first time deblock of converter valves with line breaker. According to the real bipolar connection mode of Xiamen flexible DC project, the test scheme of converter valves charging and triggering passive inversion is proposed. Firstly, the converter valves are charged without control and the voltage of unworking pole control system is used as the voltage of working pole control system for phase-locking and control. Then, the line breaker is disconnected, and in order to prevent excessive bypassing of valve submodules under low voltage, the pole control and protection system deblocks converter valves automatically for 200 ms to complete the passive inversion after the breaker returns to the node. The field test result verifies the feasibility and effectiveness of the scheme, and proves the correctness of the working among pole control and protection system, valve basic controller and converter valves, and the safety of converter valves is assured. According to the test results, the method for determining the time delay of the control system and the corresponding compensation method are put forward. The scheme can also provide a useful reference for other similar projects.

Design and Research on Composite Flanges Applied to Composite Cross Arms

WANG Jiao, ZHAO Xueling, WANG Huchang

2016, 49(11):  57-62.  DOI: 10.11930/j.issn.1004-9649.2016.11.057.06

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In order to reduce the cross arm length, tower weight and the power line corridor width, it is proposed to replace the conventional steel node with the composite flange, so as to realize the composite connection of composite cross arms. The load behaviors of composite flange are studied by tests and finite element simulations, and results show that the bearing capacity of the composite flange can meet the requirements of general 750 kV transmission lines.

Discharge and Gas Decomposition of Typical Insulation Defects in 500 kV SF₆ Current Transformer

WANG Yuanyuan, SHAO Yingbiao, WANG Shiqian, MIAO Fufeng, TIAN Chunzheng, JI Shengchang

2016, 49(11):  63-69.  DOI: 10.11930/j.issn.1004-9649.2016.11.063.07

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Two 500 kV SF₆ CTs with aluminum cylinder grading structure and cone capacitor grading structure are selected to analyze discharge and gas decomposition characteristics of insulator surface defect and combining defect. The influences of defect type, discharge path length and sampling positions are discussed. It is found that measuring PRPD is an effective assistant method for gas analysis. The detection results of the improved sample port are more accurate than that of regular one. Typical gas decomposition products of the insulation material related defects are CF₄ and CS₂. In insulator surface defect, concentration of SO₂ is higher than SO₂F₂; the growth rate of S₂OF₁₀ concentration is relatively low; types of decomposition products vary with discharge path length. In the combining defect, the growth rates of SO₂F₂ and SO₂ are relatively higher than that of S₂OF₁₀.

Research and Application of New Type of Electricity Tariff Recovery Control Measures

TANG Kejian, WANG Shuquan, SUN Qiang

2016, 49(11):  70-74.  DOI: 10.11930/j.issn.1004-9649.2016.11.070.05

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Electricity tariff recovery is an important content of power marketing. Based on an investigation of the tariff recovery status quo in power grid enterprises, this paper analyses the different consumption habits and payment features of the consumers, and studies a new type of tariff recovery control strategy that meets the customer’s needs. The business process for two tariff control modes is developed and solutions are proposed to various abnormal problems.

New Enery

Modelling and Optimal Control of PEMFC Grid-Connected Power Generation System

CAI Guowei, KONG Lingguo

2016, 49(11):  75-81.  DOI: 10.11930/j.issn.1004-9649.2016.11.075.07

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According to the electrochemical, gas flow and temperature characteristics of proton exchange membrane fuel cell(PEMFC), a custom dynamic model of the PEMFC generation system is established based on PSCAD/EMTDC with consideration of the FC module efficiency and life span, and the PEMFC operation optimization algorithm and grid-connection control strategy are proposed. The FIFO algorithm is adopted in FC module operation optimization, and the equivalent FC module running time is achieved. Boost circuit and double loop control of outer voltage loop and inner current loop are adopted in DC/DC conversion section, and steady output of voltage is achieved. Constant power control strategy of double loop control of outer power loop and inner current loop is adopted in DC/AC grid-connected inverter section, and friendly and synchronous grid-connection of PEMFC grid-connected power generation system is achieved. The correctness and effectiveness of the proposed system in this paper are verified through the PSCAD/EMTDC software platform.

Research on the Nonlinearity Characteristics of VRB-Boost Converter System

YAN Haojie, XU Ye, WANG Jinquan, XU Lei, YAN Jun

2016, 49(11):  82-87.  DOI: 10.11930/j.issn.1004-9649.2016.11.082.06

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The nonlinear behavior of VRB-Boost converter system is crucial to the safety and stability of microgrid. Furthermore, the nonlinear behavior can be influenced by the state variables, such as the state of charge(SOC) and the load impedance. Firstly, a mathematical model of the vanadium redox flow batteries (VRB) is established based on VRB’s electrical characteristics with consideration of the state of charge. Then, a discrete iterative mapping model of the current-controlled Boost converter is developed based on the stroboscopic mapping method. Thus, an unified model of the VRB-Boost converter system is established based on the above mentioned models. The unified model is then used to analyze the causes of the system’s nonlinear behavior induced by the SOC and load R. Simulation is conducted to obtain the bifurcation diagram of the system output varying with the SOC of VRB and the load R. Through comparison of the bifurcation diagrams under different conditions of state variables, the impact characteristics of the SOC of VRB and load R on the system’s nonlinear behavior are obtained. The experimental results proves the correctness of the theoretical analysis.

Study on the Impact of PV Generation on Voltage Sensetivity of Smart Distribution Network Feeder

LI Weiliang, LIU Ronghui

2016, 49(11):  88-93.  DOI: 10.11930/j.issn.1004-9649.2016.11.088.06

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Based on the distribution networking feeder, the sensitivity matrices of voltage fluctuation in distribution feeder are propposed with and without PV integration, and the relationship between vlotage and load of different nodes is established. In the same time, the validity and the correctness of the sensitivity matrix is verified through simulation on the long-distance radiant multi-branch distribution feeders. The sensitivity matrix can be used to analyze the node voltage changes caused by integration of the distributed PVs, and it is also very helpful for the long distance feeders in remote areas in predicting the possibility of beyond-limit voltage. Similarly, the sensitivity matrix can be extended to the analysis of the node voltage of distribution network with multible feeders, reactive compensation and planning of distributed PVs. And it can also be used to study the distribution network power confidence interval criterion for judging the voltage fluctuation margin, which can be used as the criterion for distribution network feeder automation and distribution network self-healing load transfer as to improve the voltage quality and power supply reliability of the distribution network.

Feasibility Analysis on Energy Balance of Doubly-Fed Wind Power Systems Under Grounding Faults

WANG Ke, WANG Xinxia, JIAO Dongxiang, ZHANG Peng, WEI Xinyu

2016, 49(11):  94-99.  DOI: 10.11930/j.issn.1004-9649.2016.11.094.06

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The paper introduces the energy imbalance problems of doubly-fed induction generator(DFIG) under grid faults, which occurs between the input energy of the wind turbine and the output energy of DFIG connected to the power grid. No literature has covered them yet until present. The output energy of DFIG is related to the excitation control strategy of rotor side converter. Firstly, an analysis is made on the output active power of DFIG under existing excitation control strategies, which shows that the DFIG electromechanical energy balance cannot be achieved under the existing excitation control strategy. Then, based on an analysis on the relation between the output active power of DFIG and the three major factors of rotor current, including the amplitude, frequency and phase of rotor current, the rotor current command is deduced to achieve the electromechanical energy balance of DFIG. A simulation circuit system is developed by using Matlab/Simulink, which verifies the correctness of the above deduction process.

Generation Technology

Implementation of Reliability Technologies for Domestic Distributed Control System

NIU Haiming, ZHANG Hongmin

2016, 49(11):  100-104.  DOI: 10.11930/j.issn.1004-9649.2016.11.100.05

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The steady operation of distributed control systems (DCS) is highly dependent on the system reliabilities. In order to enhance the reliabilities of the DCS system, this paper proposes three principles, i.e., preferential prevention, weakening impact and online maintenance, for the implementation of generalized reliability technologies based on the technical characteristics and control requirements of large thermal power generation units. According to these principles, the realization methods, principles and specific measures are discussed accordingly in the aspects of network communication, hardware performance, system power supply, early-warning function, software optimization and engineering design. To be specifically, the duplicate communication packets through duplex network can improve the fault tolerance of the system, while the redundant power supply plan can improve the power supply reliability design and the standardized algorithm can normalize the software utilization and realize safe actions during faults. In addition, the DCS system designed with these technologies has been successfully used in a 1 000-MW class ultra-supercritical thermal power unit. It has passed the testing under extreme conditions and gone through long-term operation, thus can be popularized broadly.

Performance Testing on the DCS of a Large Thermal Power Generation Unit

LIU Zhe, WAN Wenjun, HU Kangtao

2016, 49(11):  105-111.  DOI: 10.11930/j.issn.1004-9649.2016.11.105.07

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As the core part of data processing and management of large thermal power generation units, the distributed control system (DCS) performs monitoring and control over mass real-time and historic operation data. Therefore its performance has great impacts on the secure and stable operation of the units. In this paper, the test study on the DCS performance is conducted for a 1 000-MW ultra- supercritical coal-fired power generation unit, which consists of real-time testing, redundancy testing, network performance testing and anti-interference testing. The testing methods are presented and the results are analyzed, such that both the existing problems and the potential issues of the system are discovered. At last, the corresponding suggestions on improving the stability and maintainability of the DCS system are put forward, which is of great importance to guide the unit tuning.

Study on Depressurized Steam Blowing of Demonstrative 1 000-MW Unit with Double Reheat Cycles

CHEN Youfu, TAO Qian, GUAN Shipian, DING Jianliang

2016, 49(11):  112-118.  DOI: 10.11930/j.issn.1004-9649.2016.11.112.07

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Double reheating is the key technology developed for the ultra-supercritical coal-fired units. According to the characteristics of the demonstrative 1 000-MW unit with double reheat cycles, in this article, the two-stage depressurized steam blowing approach is proposed, which is to blow the primary and the secondary reheaters as well as the superheaters separately. The process design and the parameter selection are performed for this approach. With the boiler operating situation during blowing being taken into account, the characteristics of the parameters are analyzed with reasonable control methods and attentions over the parameters being presented in detail. The study may provide instructions for depressurized steam blowing in the boilers of the same type.

Startup Sequence and Troubleshooting of 1 000-MW Double Reheat Steam Turbine

XUE Jiangtao, MA Yunxiang, ZHANG Yaohua, DING Jianliang

2016, 49(11):  119-123.  DOI: 10.11930/j.issn.1004-9649.2016.11.119.05

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Based on the actual tuning process of the steam turbines in the second-phase project of Guodian Taizhou Power Plant, the startup procedures of the 1 000-MW ultra-supercritical turbines with double reheat cycles manufactured by Shanghai Turbine Company is presented, and the problems exposed in the process are analyzed with the corresponding solutions proposed, such as large exhaust steam temperature deviation, long warm-up time, high LP outer casing temperature and unsuccessful double casing startup. In addition, some control logics and the startup parameters of steam temperature and pressure as well as governing valve opening are optimized, which makes the turbine operation more energy-efficient with ultra-low emissions. This case can provide applicable guidance for the tuning and trial operation of double reheat ultra-supercritical steam turbines.

Study on Effects of Air-Staging Combustion on the Static Characteristics of Reheat Steam Temperature

HUANG Xiangbin, LONG Tao, JIANG Hongli, WEI Tongsheng

2016, 49(11):  124-128.  DOI: 10.11930/j.issn.1004-9649.2016.11.124.05

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The air-staging combustion has great impacts on furnace combustion and radiant heat exchanging processes. The analysis figures out that the reheat steam under temperature at low loads is attributed to high flue gas temperature and substantial radiant heat exchange volume in the main combustion zone. In addition, the theoretical analysis and the field tests indicate that the optimization of oxygen contents and furnace-windbox differential pressure may raise the reheat steam temperature, thus improving the performance of reheat steam under temperature at low loads. This paper may provide valuable reference for the operation optimization of boilers with air- staging combustion.

Study on Online Eddy Current Detecting of the Boiler Heating Surface Tube Elbow in Thermal Power Plants

LIU Yunlong, LI Dengke, QIN Yongliang, XIONG Liang, SHEN Dingjie, LONG Yi

2016, 49(11):  129-134.  DOI: 10.11930/j.issn.1004-9649.2016.11.129.06

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According to the characteristics of the closed ends, the tight tube panel layouts and the narrow detecting space in online eddy current detecting of the boiler heating surface tube elbow in thermal power plants, an external placed saddle-shaped eddy current detecting probe is designed, which can be used to test the small diameter austenitic stainless steel tube elbow. The comparative sample tube is made in accordance with the eddy current detecting technical standards. Through the sample testing and the applications in thermal power plants, the results show that the designed saddle-shaped eddy current detecting device has better sensitivity and reliability to the linear defects more than 0.2 mm deep and the hole-like defects larger than D1.4 mm. It can realize the non-destructive online testing of the austenitic stainless steel tube elbow that has serious oxidation and corrosion as well as more concentrated stress.

Analysis and Treatment of Bearing 1 Vibration Fault in a 600-MW Steam Turbine

LI Yuchun, CHEN Tao, YANG Weimin, QI Minfang

2016, 49(11):  135-139.  DOI: 10.11930/j.issn.1004-9649.2016.11.135.05

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Due to the excessive shaft vibration on Bearing 1 of a 600-MW supercritical unit when it is switched from single valve to sequential valve operation mode at around 460 MW load level, the sequential valve mode cannot be normally committed, which has great impact on the economic performance of the unit. By virtue of field data collection and analysis, the cause of the abnormal vibration is analyzed precisely in the aspect of vibration mechanism. Through shafting level adjustment, the abnormal vibration of Bearing 1 is successfully eliminated. This case is useful for analyzing similar vibration fault in supercritical power plants.

Analysis on Primary Frequency Regulation Performance of the Units under DC Blocking Fault in UHV Receiving End Power Grid

XUAN Xiaohua, YIN Feng, ZHANG Yongjun, ZHANG Bao, LU Min, CHEN Liyue

2016, 49(11):  140-144.  DOI: 10.11930/j.issn.1004-9649.2016.11.140.05

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The East China power grid has gradually formed a UHV (Ultra High Voltage) large receiving end grid. However, high voltage DC block faults occur occasionally, which brings high risk to the safety of power grid frequency. The consequences of some of the faults show that the primary frequency regulation performance of the units in the grid is not able to meet the new requirements, and the drop of the frequency is out of expectation. In this paper, the ideal primary frequency regulation capability and the actual response of the units in the grid are analyzed based on the DC bipolar blocking fault happened on September 19, 2015. Taking the units in Zhejiang Power Grid as an example, the factors that would affect the primary frequency regulation capability are proposed, and the technical requirements and measures for improving the primary frequency regulation ability of the thermal power units are put forward accordingly to provide reference for the optimization of the primary frequency regulation control strategy in the new power grid pattern.

Common Issues of Runback Fossil Fuel Power Plant Load Shedding and Its Technical Code Constitution

ZHANG Qiusheng, JIA Qiangbang, YIN Feng

2016, 49(11):  145-148.  DOI: 10.11930/j.issn.1004-9649.2016.11.145.04

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The common issues existing in the implementation of the technical code of DL/T 1213-2013 for runback in fossil fuel power plants are classified and analyzed in this paper. With focusing on the common problems in RB failure, the specific measures are summarized, and the corresponding technical specifications are constituted, in which the constitution background, the RB types, the test conditions, as well as the test acceptance conditions and standards are illustrated in detail. In addition, the details in RB action quality quantification and grading are also presented, which is an explanation and supplement to the technical code.

Application of Improved Oxygenated Treatment on Ultra-Supercritical Unit with Precise Low Oxygen Content Dosing Technology

LI Junwan, CAO Jieyu, LIU Wei, HE Lei, WANG Dejun, MENG Linhui, WANG Sihua

2016, 49(11):  149-152.  DOI: 10.11930/j.issn.1004-9649.2016.11.149.04

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It is of vital importance to implement oxygenated treatment for(ultra) supercritical units to effectively inhibit flow accelerated corrosion in feed-water and high pressure heater drain systems. The improved oxygenated treatment with low oxygen content, appropriate feed-water pH value reduction and precise oxygen dosing technology is developed to solve the oxide scale problems in both the superheaters and the reheaters. Compared with the traditional oxygenated treatment using low oxygen content, this technology can further improve the economic efficiency of condensate polishing system, effectively inhibit flow accelerated corrosion in high pressure heater drain system and reduce its iron contents without any extra oxygen content increase in the steam, which not only eliminates the adverse effect of oxygen dosing on oxide scale exfoliation but also has the advantages of other oxygenated technologies. Its application on 1 000-MW ultra-supercritical unit shows good effects such that the whole water-steam circuit system is fully protected effectively.

Energy Conservation and Environment Protection

Evaluation on Ultra-Low Emission Performance of SCR Flue Gas Denitrification Device for 300-MW Class Coal-Fired Units

FENG Qianwei, ZHANG Yang, WANG Fengji, ZHU Yue

2016, 49(11):  153-158.  DOI: 10.11930/j.issn.1004-9649.2016.11.153.06

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The evaluation and analysis on the ultra-low emission performance of SCR denitrification device can provide reference and guideline for its stable, efficient and economic operation. Taking the SCR denitrification device of three 300 MW coal-fired units with ultra-low emissions for example, the operation parameters are evaluated, such as the denitrification efficiency, the inlet/outlet NO_x concentration distribution, the outlet flue gas velocity distribution, the ammonia escape rate, the conversion rate of SO₂ into SO₃, and the system resistance. Thusthe major properties of the device are obtained. The test results show that the overall performance of the device is good, but there still exist some problems such as flow field imbalance, fly ash clogging and excess ammonia escape. Therefore, the methods and recommendations are proposed to solve such problems.

Experimental Study on Limestone-Gypsum Wet Desulphurization with Simulated Flue Gas under Oxygen-Enriched Combustion

LIU Yi, ZHONG Zhaoping, ZHAO Kai, SHI Xiaohong, CHEN Chuangshe, WANG Wenbao

2016, 49(11):  159-164.  DOI: 10.11930/j.issn.1004-9649.2016.11.159.06

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To study the efficiency of limestone-gypsum wet flue gas desulfurization under oxygen-enriched combustion, the desulfurization test is conducted on the self-established experiment rig. Through controlling the CO₂ concentration(the volume fractions as 14%, 60%, 70%, 80% and 90%) in the desulfurization system, the impacts of different flue gas velocity, liquid gas ratio, inlet SO₂ concentration, and slurry pH value on the SO₂ absorption characteristics under the oxygen-enriched combustion atmosphere are studied. It is discovered that with the increase of flue gas velocity and inlet SO₂ concentration, and the decrease of gas liquid ratio and slurry pH value, the desulfurization efficiency drops; the higher CO₂ concentration in the system, the lower desulfurization efficiency is observed. Meanwhile, under different CO₂ concentration atmosphere and slurry pH value, the gypsum crystal grain size is studied by using the laser particle analyzer and the gypsum is scanned by using the SEM electron microscope, from which it shows that the slurry pH value and the CO₂ concentration do not have obvious impacts on the crystallization of gypsum.

Troubleshooting and Preventive Measures of WESP Spray Nozzle Faults in Coal-Fired Power Plants

LU Ruiyuan, LI Zhuo, WANG Liqiang

2016, 49(11):  165-169.  DOI: 10.11930/j.issn.1004-9649.2016.11.165.05

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In order to meet the ultra-low emission requirements for coal-fired power plants, the wet electro-static precipitator(WESP) is used in some regions of the country. As the key part of WESP, the spray nozzle will immediately endanger the WESP operation in case of fault, such as blockage and dropping down, two types of major faults in the spray nozzle operation. Taking the WESP of a 600-MW unit firstly installed in Guangdong Province for example, based on the analysis on the operation experience, series of the feasible and effective contingency countermeasures are proposed. For instance, before the spray nozzle installation, clean up the WESP spraying circulating water system thoroughly and equip the nozzle with fine filter to lower the contents of solid impurities as much as possible. During the operation, flush the front collecting plate sparge pipe more frequently with large volume of water and tune the self-cleaning filter running mode. During the unit startup phase, increase drain tank blowdown, and reduce the overflow water from the water circulating tank to the drain tank, etc. The practice shows that with these measures, the failure rate has been significantly dropped.

Optimization of Corrugated Plate Mist Eliminator Hook Dimensions with Response Surface Method

HONG Wenpeng, LEI Jianqi

2016, 49(11):  170-174.  DOI: 10.11930/j.issn.1004-9649.2016.11.170.05

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The computational fluid dynamics(CFD) method and the 2-D incompressible, unsteady flow model are used to conduct a numerical simulation of the gas-liquid two-phase flow field inside a corrugated plate demister with hook. The demister performance simulated values and experimental values are compared. By taking advantage of the numerical calculation result, the effect of the hook-length, hook-angles and hook-radiuses on the demister performance are studied based on the response surface method (RSM) combined with the statistical software Design-Expert, and the quadratic polynomial prediction model of the above three impact factors are also derived. The simulation results show that the demister performance simulation values are consistent with the experimental values, which verifies the reliability of the calculation result. Among the factors mentioned above, hook-length, hook-angles, hook-radiuses, square term of hook-length and the interaction of hook-length and hook-angles have the most significant impacts on the response values. Within the size range, the performance achieves the optimal when H=10 mm, β=39.59°, and r=24 mm. In conclusion, the study results are helpful to further improve the design method of the mist eliminator.

Study on Regeneration of Used SCR Catalysts Containing Ba

YU Weijia, WANG Jinxiu, CHEN Jinsheng, YU Yanke, MIAO Jifa

2016, 49(11):  175-180.  DOI: 10.11930/j.issn.1004-9649.2016.11.175.06

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The regeneration of deactivated commercial selective catalytic reduction(SCR) catalysts is helpful to improve the economic efficiency of power plants and protect the environment. Take the example of the deactivated SCR catalysts containing Ba from a power plant as the study object, three methods, i.e., combined sodium hydroxide and citric acid cleaning, dilute sulphuric acid cleaning and ammonium sulfate solution cleaning, are adopted to conduct the regeneration processing of the catalysts. The physicochemical properties of the catalysts before and after the regeneration are tested, then the deactivation causes and the performance recovery are analyzed by various characterization and evaluation methods. Moreover, the regeneration effects of the three methods are compared. The results show that the deposit of the impurities such as BaSO₄, K and Na detected on the surface of the used catalysts are the root cause leading to the catalytic activity deterioration. The three regeneration methods can all remove the impurities of K and Na at different levels. After the regeneration the denitration efficiency is improved substantially at different molar ratios of ammonia to nitrogen, among which, ammonium sulfate solution cleaning method produces the most desirable effect.

Approach of Energy Saving and Consumption Reduction of Circulating Water Pump and Its Application

LI Zhiheng, ZHANG Juan, SONG Xing

2016, 49(11):  181-184.  DOI: 10.11930/j.issn.1004-9649.2016.11.181.04

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The circulating water system in Huadian Laizhou Phase I Project adopts once-through water supply system using seawater as the water source. According to the characteristics that seasonal air temperature changes, microorganism reproductions and tidal differences would cause substantial increase of the circulating water temperature and volume at the same loads and time the comprehensive analysis and optimization are conducted in the aspects such as periodic half side flushing, circulating water pump operation modes and circulating water system users and the optimal operation mode is obtained, which enables better energy saving and consumption reduction.