Table of Content

05 May 2013, Volume 46 Issue 5

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Security column

Research on Slagging Prevention in 600-MW Supercritical Boilers with Four-Wall Tangential Firing

WU Ying, MAO Xiao-fei, WANG Qian, CHEN Lin-guo

2013, 46(5):  1-5.  DOI: 10.11930/j.issn.1004-9649.2013.5.1.4

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In order to solve the serious slagging problem in a 600-MW supercritical boiler of a power plant, research was conducted to figure out the slagging locations based on the analysis of features on the structure of the boilers with wall tangential firing. Testing combined with numerical simulation was adopted in the research. By watching the peep holes and blowing the soot blower one by one, slagging was located around the burner nozzles rather than the lower part of the platen superheater where slagging frequently happened. Analysis showed that there is deviation existing in the furnace temperature distribution; low ash fusion temperature of the as-fired coal and high cross-sectional thermal load in the burner zones are the main reasons for furnace slagging. Some countermeasures were taken and the slagging problem in the boiler was solved successfully. Also, this method can be a reference for other types of boilers.

Online Dismantling and Installation of Unloading Valve for Hydraulic Servomotors in 1 036-MW Ultra-Supercritical Unit

CHEN Fan-fu, ZHU De-yong, FENG Ting-You, ZHANG Ze-xiong

2013, 46(5):  6-8.  DOI: 10.11930/j.issn.1004-9649.2013.5.6.2

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It happened to a1 036-MW ultra-supercritical unit that the oil drainage plug at the bottom of the oil cylinder piston was fallen off, which caused the governor valve to operated abnormally. Online repairing was made for this issue. In order to ensure the security of unit operation, simulation was conduction a same type outage unit. The technical scheme of online dismantling and installation of the unloading valve for the hydraulic servomotor is presented, including the measures to maintain the normal operation of the unit and the issues which need to pay attentions in online repairing, as well as the process to restart the servomotor after the repairing. The result showed that the adopted technical measures are adequate and an unnecessary unit outage was avoided.

Fine Adjustment of Turbine Axial Flow Passage Clearance

LI Bin, YANG Zhen-guo, LI Ying-jie, ZHOU Rong-gui, ZHANG Quan

2013, 46(5):  9-12.  DOI: 10.11930/j.issn.1004-9649.2013.5.9.3

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The adjustment of axial flow passage clearance is the major item in turbine maintenance. If the shaft of turbine moves in any direction, all the clearances between blades will be changed. It is difficult to figure out all abnormal data with traditional method due to the massive and complicated measurements. Therefore, it slows down the adjustment process and is difficult to determine the best position of the shaft. In this paper, a new computing graphics based method is proposed. The immediate approach can accelerate the data analysis effectively to figure out the best axial position of the turbine rotor. It is flexible, manageable and has vast importance to the maintenance of large steam turbines.

Several Measures of Improving the Efficiency and Reliability of FGD System in Power Plant

ZHANG Jun-mei

2013, 46(5):  13-17.  DOI: 10.11930/j.issn.1004-9649.2013.5.13.4

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With the promulgation and implementation of GB13223-2011《Emission standard of air pollutants for thermal power plants》,the requirements on the performance and reliability of power plant Flue Gas Desulphurization (FGD) system for performance and device reliability are further strict. Several key factors influencing the efficiency and reliability of the FGD system were particularly analyzed, including emergency cooling system, condensate treatment, absorber optimization and design as well as the reliability of common system, and a series of methods based on summarizing the previous design experience were also given in this paper to ensure the higher system reliability as well as the desulphurization efficiency.

Anti-freezing and Pre-heating Measures for Radiator in Indirect Air-Cooling Units in Cold Areas

LIU Pei-zhong, YANG Zhi-jun

2013, 46(5):  18-22.  DOI: 10.11930/j.issn.1004-9649.2013.5.18.4

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Radiator freezing is common in indirect air-cooling units in alpine regions. In order to improve the running security of the indirect air-cooling units in winter, in-depth analysis and research on freezing in sector radiator tubes are conducted, which concludes that the existing anti-freezing measures are inefficient in alpine regions. Therefore, a design for anti-freezing and pre-heating is proposed with anti-freezing measures and ice-melting methods for the radiator fin tube bundles presented. The new design can provide a safeguard for the secure and reliable operation of the indirect air-cooling units in alpine regions.

The Configuration Analysis of Firefighting Water Supply Facility of Taishan Nuclear Power Project Phase Ⅱ

XU Ren-tao, SUN Shi-min, LI Zhen-zhou, SUN Fang, PENG Yue

2013, 46(5):  23-27.  DOI: 10.11930/j.issn.1004-9649.2013.5.23.4

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Taishan nuclear power project phase Ⅱis under preparation, planning to adopt EPR technology. In order to reasonably configure firefighting water supply facility, an optimized engineering scheme for Taishan nuclear power project phase Ⅱis proposed ,with the configuration of firefighting water supply facility of Taishan nuclear power project phaseⅠand Lingao NPP project phase Ⅱ taken into account, and the impact on emergency water supply system and cooling & purification system of fuel pool posed by firefighting water supply facility analyzed, as well as the positioning and classification of the functions of firefighting water supply performed. Such scheme requires less resources and lower cost than the firefighting system configuration of Taishan nuclear power project phaseⅠ, complying with the precondition such as the firefighting design criteria for nuclear power plant(nuclear safety guideline HAD 102/11), EPR technical requirements and safeguarding the safe operation of nuclear power plant.

High-Voltage Trip-off Mechanism of Wind Power Generators in District Grids with Large-Scale Wind Power Integration

YANG Jin-gang, WU Lin-lin, LIU Hui, LIANG Yu-zhi, LI Qun-ju

2013, 46(5):  28-33.  DOI: 10.11930/j.issn.1004-9649.2013.5.28.5

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Integration of large scale wind farms to a weak power grid will decrease the margin of voltage stability and increase the difficulty of voltage control. The high-voltage formation mechanism in the process of long distance transmission of large scale wind power is discussed based on an actual event of high-voltage trip-off of wind power generators. An equivalent single-machine infinite-bus system model is established to simulate the wind farm connection with the power grid through long transmission line and derive the relationship of bus voltage with wind power level and reactive power compensation. It is pointed out that there will be a sharp increase in voltage after capacitor compensation at the limited operation point, which may cause a high voltage and then make wind generators trip-off. A real grid integrated with wind farms is simulated by using the DIgSILENT software to prove the conclusions above.

Study on Lightning Withstand Calculation Algorithm for Double Circuit Transmission EHV Line

GENG Hou-hua

2013, 46(5):  34-37.  DOI: 10.11930/j.issn.1004-9649.2013.5.34.3

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The electrical geometry model algorithm is a major one to analyse the lightning withstand level of transmission line in engineering. For the traditional algorithm, the interrelation among conductors are not considered. The calculating result for double circuit lines will have some error. The reason is studied firstly. Then, a new electrical geometry model is studied to consider the effect of conductors. Then, a new algorithm is studied for the new model. intersection coordinates of striking distance are obtained when lightning injects vertically to the ground. Secondly, coordinates and mapped to different geometrical space according to changing of lightning injection angle. At last, the lightning withstand level of double circuit EHV transmission line is calculated based on the new algorithm according to Huainan~Huxi 1 000 kV transmission line project. And the protection angle value is commended.

Lightning Protection Performance of 500 kV Compact Transmission Lines

ZHAO Yuan, LI Yu, DENG Chun, WANG Jian

2013, 46(5):  38-44.  DOI: 10.11930/j.issn.1004-9649.2013.5.38.6

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Lightning protection of compact transmission lines is very important for their safety operation. A statistic analysis of the lightning protection performance of compact lines in the north Hebei area indicates that the compact lines have obvious advantages over the conventional lines in lightning protection performance. Due to its special tower window structure, shorter air gap and lower lightning impulse flashover voltage, the compact line is higher than the conventional line in back striking trip-out rate.

Design and Full-scale Test for Cup-type Steel Tubular Tower of UHV Transmission Line in Heavy Icing Area

ZHANG Zi-fu, YANG Jing-bo, YANG Feng-li, LI Qing-hua

2013, 46(5):  45-50.  DOI: 10.11930/j.issn.1004-9649.2013.5.45.5

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The ZB1 cup-type steel tubular tower is firstly used for the single-circuit UHV transmission line in heavy icing area. Except for the ground supports, the steel tubulars are applied in the whole tower. The used tubular steel is Q345 and the plug-in boards and forging flanges are used for connection. Through the monographic study on the tower optimization, node structure, tower’s Eiffel effect and bending moment at the member end, the design of ZB1 cup-type steel tubular tower is improved. The full-scale test verifies the reliability in design and manufacture of cup-type steel tubular tower for UHV lines in heavy icing area. The research results of this paper can be widely applied in UHV transmission line projects.

Operation Analysis on the Reactive Power Compensation Devices of 500 kV Substations

LU Fei, MENG Yi, HU Dan-hui

2013, 46(5):  51-55.  DOI: 10.11930/j.issn.1004-9649.2013.5.51.4

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The low-voltage side reactive power compensation devices of the 500 kV substations in Hubei power grid were studied and a statistic analysis was made on the common problems and faults occurred in recent years. The analytical results show that the reactive power compensation devices that has been put into operation in Hubei power grid have such management and operative problems as divided standards for selecting capacity, rated current and rated voltage, being prone to heating, bulging and oil leakage. Some measures and recommendations were proposed for preventing the faults of reactive power compensation devices.

Operation Overvoltage Analysis of the Circuit Breakers with Closing Resistors in UHV Grids

HUANG Gang, LIU Yu-jun

2013, 46(5):  56-60.  DOI: 10.11930/j.issn.1004-9649.2013.5.56.4

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A summary was made of the circuit breaker explosion accidents happened in the past two decades in the ultra-high voltage (UHV) substations in China. In order to provide a technical basis for the operation and maintenance of circuit breakers with closing resistors in 500 kV transmission lines, the no-load switching tests were simulated through PSCAD on the backbone grid in west Sichuan province. The simulation results indicate that the circuit breakers can endure the operation overvoltage from both directions of the lines with the help of the both-side arresters and high-voltage reactors.

Accident Analysis and Dynamic Simulation of Smart Substation

LIANG Fu-bo, ZHENG Wei, ZHI Yong, ZHE Zhong-ming, LIANG Chen, QIAN Wei-jiang, LV Bin

2013, 46(5):  61-65.  DOI: 10.11930/j.issn.1004-9649.2013.5.61.4

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During the “12th Five-Year” period, smart grid will enter the construction phase. Smart substation is a key part of the smart grid, and its operation status directly affects the safety and stability of the smart grid. Attentions therefore should be paid to all aspects of smart substation commissioning. An analysis was conducted on a protection action accident of a smart substation, which was caused by the defects of merging units of lines resulted from bus equipment faults. The dynamic simulation reconstructed accident and verified the correctness of treatment measures. Systematic testing was conducted on the related equipment, and some suggestions are proposed for future smart substation equipment commissioning test.

Common Faults and Cause Analysis of XLPE Cables

WU Ming-xiang, OUYANG Ben-hong, LI Wen-jie

2013, 46(5):  66-70.  DOI: 10.11930/j.issn.1004-9649.2013.5.66.4

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The faults of 6 kV(and above) XLPE cables occurring in the State Grid during 2009-2011 is analyzed in terms of failure rate, failure location and failure causes and the typical failure types and characteristics are summarized. It can be concluded that, the failure rate of power cables has been decreasing year by year in recent years; the failure mainly occur in the cable itself; and in addition to construction, the main insulation aging, improper installation technology and overload are the main cable failure causes. Proposals are put forward to improve running reliability of power cables.

New Energy

Quasi-Directional Variation and Rollback Mutation Based Differential Evolution Algorithm for Reactive Power Compensation of Wind Farms

ZHENG Tai-yi, JIAO Shao-hua, ZHAO Hui-long, LIN Li

2013, 46(5):  71-76.  DOI: 10.11930/j.issn.1004-9649.2013.5.71.5

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Reactive power compensation of power grids is a kind of high-dimensional nonlinear optimization procedure that will become extremely complex with the integration of large-scale wind farms. Differential evolution algorithm is an effective method to solve the problem. To overcome its heavy dependence on the initial population and weak capability to approach to the optimization solution in the early process, a strategy based on quasi-directional variation and rollback mutation is presented to improve the performance of the algorithm. The sum of all bus voltage deviations is treated as the objective function and a computational model to design the compensation scheme is established. Compared with the ordinary differential evolution algorithm, the proposed algorithm is more efficient in searching for optimal solution with better convergence, such that the compensation scheme can be obtained with significant improvements in the area voltage profiles.

The Enlightenment of GHG MRV under US EPA and EU ETS for China Power Generation

ZHANG Li-xin, DUAN Zhi-jie, YAN Bai-qiang, CHEN Wei, ZHANG Li-xing

2013, 46(5):  77-82.  DOI: 10.11930/j.issn.1004-9649.2013.5.77.5

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The measurement、reporting and verification (MRV) of the GHG emissions are the fundamental work for the GHG management in each country. The power generation is the main source of GHG, and it is the key content of GHG management. This paper pays more attention on introducing the MRV methods applied to GHG emissions from electric enterprises by Mandatory Greenhouse Gas Reporting (GHGRP) of US Federal Government and European Union Emissions Trading Scheme (EU ETS). Through the analysis of the differences between GHGRP and EU ETS in controlled objects, GHG categories, GHG monitoring, reporting, verification, etc. This paper discusses the enlightenment from GHG management work in US and EU, especially towards the carbon emission management work in electric sector of China.

Comparative Study of Integrating Technique for Wind Power between China and Germany

DONG Cun, PEI Zhe-yi, HUANG Yue-hui

2013, 46(5):  83-89.  DOI: 10.11930/j.issn.1004-9649.2013.5.83.6

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Germany is the first country to conduct the research on wind power integrating techniques, technical standards and related policies, which make it at the leading position globally in wind power management. The comparison between Germany and China in respect of integration strategies, technical standards and certification systems is made to borrow the advanced experience from Germany and improve the integration techniques and social accommodation level in China.

Electric Power Economy

Study on Power Factor Reactive Power Charging Mechanism

ZHENG Hou-qing, GAO Xiao

2013, 46(5):  90-93.  DOI: 10.11930/j.issn.1004-9649.2013.5.90.3

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It is very important for improving the power supply level to strengthen the management of the reactive power and power factor tariff for power users and to reduce the reactive power flow in the grid. On account of the prominent problems in power-factor regulating tariff in China, and based on the British experiences in reactive power charges, the paper analyzed the necessity for China to implement the reactive power charging mechanism and proposed relevant calculation methods and policy recommendations.

EMD-SVM-Based Price Forecast Model for Grid Equipment

LU Yan-chao, WEN Wei-ning, ZHAO Biao, ZHENG Yan, SHI Xue-fei

2013, 46(5):  94-98.  DOI: 10.11930/j.issn.1004-9649.2013.5.94.4

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The equipment price of a grid project is nonlinear and non-stationary, and it is difficult to be estimated accurately. Therefore, the EMD-SVM model is built to divide the historical prices into smooth and periodically-fluctuating components with empirical mode decomposition(EMD). Take these components as input, their forecast values are obtained with support vector machine(SVM), and then these values are superimposed to gain the final forecast price. The comparison between the forecast price and the historical data of a 180-MVA transformer and the error analysis are carried out, which indicates that the EMD-SVM-based forecastion can effectively improve the accuracy of the equipment price forecast and is helpful for project cost control and equipment bidding.

Comprehensive Evaluation of the Ways to Pay Electric Bills Based on TOPSIS

ZHOU Ling-fang, Liu Yang-yang, JIANG Yuan, GUO Hong-zhen

2013, 46(5):  99-105.  DOI: 10.11930/j.issn.1004-9649.2013.5.99.6

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The recycling of electric bills directly affects the operation of electric power companies, and the construction and operation of the bulk power marketing system. The ways to pay electric bills play an important role in the electricity market and social development. The self-operated and partner-involving ways to pay electric bills were analyzed with TOPSIS in this paper, and a comprehensive evaluation system was established in view of the electricity companies and the users as well as the partners. Based on the combination weighting method of all levels of indicators, the ways to pay electric bills were compared comprehensively and scientifically. By taking a city as an example, three self-operated ways and six partner-involving ways were analyzed, and the result indicates that the power self-payment terminals is the worthiest way for promotion in the three self-operated ways, while the Yingda recharge card has large potential, and the electric bills deducted by banks is a good way in the six partner-involving ways.

Application of Reliability Cost-Benefit Analytical Method in Power Grid

XIE Chu, ZHANG Yan, HUANG Yi-chao

2013, 46(5):  106-110.  DOI: 10.11930/j.issn.1004-9649.2013.5.106.4

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The reliability cost-benefit analytical method can be used to well deal with the relationship between power supply reliability and the economy of network construction. The composition and calculation method of reliability costs and reliability benefits are described in this paper. On the basis of a quantitative evaluation of the power supply reliability, the reliability cost-benefit analytical method has been applied to the power grid. An analysis is made on the 220 kV and 500 kV network planning schemes of one certain area in East China of the year 2005, 2010 and 2015. By using the improved ratio of output value to unit electricity consumption method. each year’s unserved energy costs are estimated, and the difference in power supply reliability and cost/benefit are compared after power grid expansion. The result can provide references for network planning and construction.