Table of Content

25 December 2012, Volume 45 Issue 12

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Special Conlribulion

Key Issues for Development of China’s Power Market Considering Large-Scale Renewables Integration

J. Charles Smith

2012, 45(12):  1-3.  DOI: 10.11930/j.issn.1004-9649.2012.12.1.2

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A large proportion of variable generation like wind and solar energy introduces a higher level of variability and uncertainty into power system operation than the traditional fossil, nuclear and hydro generation. Successful integration of these new energy resources requires that traditional market structures and associated transmission planning and market operation practices be re-examined in light of the different characteristics and requirements of these new energy sources. This article examines the underlying transmission planning structure needed to support the power market evolution, and a number of critical developments within the power market with respect to control area size, reserve requirements, unit commitment and economic dispatch practices, needed to enable reliable system operation with increasing penetration of variable generation.

Generalion Technology

Cause Analysis and Countermeasures of Malfunction of 1 000-MW Turbine Pad Vibration Protection

ZHANG Qiu-sheng, FAN Yong-sheng, SHI Wen-tao, HU Xiao-hua, DING Jun-hong, GAO Ai-min

2012, 45(12):  7-11.  DOI: 10.11930/j.issn.1004-9649.2012.12.7.4

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Focusing on the malfunction of 1 000-MW ultra-supercritical turbine bearing pad vibration protection in combination with the investigation into turbine bearing pad vibration protection of 29 1 000-MW turbines adopting Siemens technologies in 21 power plants, the mechanism of VM600 NOT OK signals and the causes for the malfunction are analyzed. Due to the high sensitivity of the probe, whenever there is nonstandard cable grounding, high induced voltage or improper installation of moving cables and probes, the NOT OK signals will be issued incorrectly. In addition, this signal in VM600 is extended to 10 seconds, which amplifies the influence of this mistake. By modifying the program of VM600, enhancing shielding and grounding to ensure the accuracy of the measurement, power plants using Siemens turbine technology can operate safely if they abide by the protection logic of the original design.

Experimental Research & Application of Sliding Pressure Optimization for 1 000-MW Steam Turbines

BAO Jin-song, SUN Yong-ping

2012, 45(12):  12-15.  DOI: 10.11930/j.issn.1004-9649.2012.12.12.3

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Sliding pressure operation with full arc admission is designed as the usual operating mode for STC-Siemens 1 000-MW steam turbines. To meet the requirements of the AGC fast load response, a wide margin is usually left by the turbine control valves for load regulation, which causes considerable throttling losses to the valves, unfavorable for the unit’s economic operation during load variation. This paper describes the method of optimizing the sliding pressure operating mode for the STC-Siemens 1 000-MW steam turbines by means of high precision tests. A sliding pressure curve taking account of both economic efficiency and controllability is obtained and the affecting parameters are analyzed. Meanwhile a practicable method of correcting the sliding pressure curve is put forward, which could be a reference for operation optimization for the same type of turbines.

Research on Variable Pressure Operating Characteristics of Throttling Units with Additional Supplying Steam at Overload

WAN Zhong-hai, LU Jin, CHEN Wen, YAN Tao, WU Yang-hui

2012, 45(12):  16-20.  DOI: 10.11930/j.issn.1004-9649.2012.12.16.4

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For the operation curve of the coordinated control system of the supercritical throttling steam turbine with additional supplying steam at overload in practical application, the primary and secondary frequency regulation is limited and abnormal low-load jump coordination happens, which endanger the security of power stations and grids. Through changing the main steam pressure continuously with small steps, using the model for variable pressure operation quantitative calculation and taking full account of the mutual coupling between the main variables of the thermodynamic system, the overall dynamic optimization of the unit heat rate is realized in the same load sliding pressure operation range and the trend of the heat consumption is obtained, which becomes a guideline for the safe and efficient operation of the unit.

Cause Analysis for Low Reheat Steam Temperature and Transformations of 300-MW Boilers

ZHAO Zhen-ning, WANG Jing-jing, XU Li-wei, YAO Wan-ye, TONG Jia-lin

2012, 45(12):  21-25.  DOI: 10.11930/j.issn.1004-9649.2012.12.21.4

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For the 300-MW subcritical boiler in a power plant, the steam temperature at the outlet of the reheater has always been lower than the designed value after the turbine through-flow transformation. Through the analysis on the data from the reheat steam temperature adjustment test, it is observed that the steam temperature at the inlet of the reheater is much lower than the designed value. Based on the thermal balance calculation, three schemes for increasing the capacity of the reheater are proposed. After comparison, the most reasonable one is selected and put into practice. The performance test after the transformation indicates that the reheat steam temperature at the outlet of the reheater is improved significantly, reaching the designed value of 541 ℃ with the economic efficiency of the plant also improved greatly.

Elimination of Gypsum Rain with Admixing and Heating Cleaned Flue Gas

WU Ju, ZOU Tian-shu, LENG Jie, QU Ying-jun, XU Xiao-chu

2012, 45(12):  26-30.  DOI: 10.11930/j.issn.1004-9649.2012.12.26.4

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A large number of raindrops, so-called gypsum rain are found frequently around the smoke stack of large thermal power plants with no GGH installedin the wet FGD system in China. , which seriously affects the environment and the living of people around the plant. It is mainly attributed to the lowe temperature and high humidity of the cleaned flue. Therefore, heating the cleaned flue gas by hot secondary air from boiler island, i. e. admixing and heating the cleaned flue gas(AHG) is designed and applied to eliminate the gypsum rain. Based on the practice in a cogeneration power plant in Fushun, the principle, implementing measure and main designed parameters of AHG are introduced. The technical and economic analysis is carried out with the test data, such as boiler efficiency, auxiliary power consumption and net coal consumption. Taking a 300-MW unit for example, the economics and the safety are compared among AHG, medium GGH and rotation GGH. Significant economic and social benefits are observed from the practice in which the gypsum rain is eliminated by AGH with low investment and annual cost, no corrosion or blocking compared with GGH.

Power Syslem

Quality Management on GIS Installation in High Altitude Areas with Desertificated and Saline Soil

ZHANG Ling-li, WU Xing-bo, WU Jian-ping

2012, 45(12):  31-33.  DOI: 10.11930/j.issn.1004-9649.2012.12.31.2

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There is no corresponding technical data and standards to guide constructions of gas insulated switchgears(GISs) with super-long size and 750 kV voltage in high altitude areas with desertificated and saline soil. An introduction of this kind of GIS assembly practices in a 750 kV power transmission project is presented. Considering sandstorm weather as well as salt particles in air, many measures were used, such as dust-preventing covers for equipment, clearing elements and blowing-off dust on workers who are going into the resembling room. An integrated schedule for equipment delivery, installation and tests in field was designed and implemented for the quality control of GIS installation in conditions mentioned above, by which the safety and reliable operation of GISs can be ensured. This research and practice can be references for similar projects.

Principal Problems and Solutions of the Foundation Engineering in the High-Attitude Permafrost Region

YAN Fu-zhang, LI Peng, CHENG Dong-xin

2012, 45(12):  34-41.  DOI: 10.11930/j.issn.1004-9649.2012.12.34.7

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Qinghai-Tibet direct-current interconnection project is the largest transmission project constructed up to now in the paramos region of highest attitude in the world. It is also the longest project that traverses the permafrost region. The permafrost,characterized by being poor in thermal stability, rich in underground ice, very sensitive to the climate warming, and strong in water-thermal activity, causes great challenges to the tower foundation construction, which include tower foundation type selection and design, permafrost protection in the process of foundation construction and long-term foundation stability. On the basis of a study of the engineering geological conditions and principal engineering geological problems of the project, a systematic analysis is carried out on the principal engineering problems of transmission tower foundations in the permafrost region and an introduction is made to the main solutions to the problems in the process of project construction.

Loading Test of the Assembly Foundation in Frozen Soil of the Qinghai-Tibet AC and DC Interconnection Project

DING Shi-jun, LU Xian-long, CHENG Yong-feng, HU Zhi-yi, YANG Wen-zhi

2012, 45(12):  42-47.  DOI: 10.11930/j.issn.1004-9649.2012.12.42.5

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To analyze the safety and stability of tower foundation for the Qinghai-Tibet AC and DC Network Project, loading tests were carried out on an assembly prototype foundations in the frozen soil under vertical and horizontal loads in the Tibetan Plateau Wudaoliang area. The principle adopted for the prototype test was to keep consistence between the prototype test and the tower foundation construction in foundation dimensions, construction technique and construction time. According to the test results, the limit and destruction state of the foundation were analyzed, and the characteristics of load vs. displacement curves and the bearing properties were studied. The bearing capacity of the test foundations and uplift angle value were obtained. The test results show that the assembly foundations in coarse-grained frozen soil failed in stability due to large horizontal displacement under test loads, and the load vs. displacement curves are of non-steep-drop type, and the soil strength and foundation's bearing capacity with the active zone in frozen state are better than that with the active zone in melt state, and uplift angle of coarse-grained soil is greater than 13 degrees, and bearing capacity of assembly foundation meets the design requirements.

Analysis on the Impact of Hami-Zhengzhou Ultra-High Voltage DC Project on the Power Grid

GUAN Hong-hao, ZHANG Feng, SUN Yi-qian, YAO Xiu-ping

2012, 45(12):  48-51.  DOI: 10.11930/j.issn.1004-9649.2012.12.48.3

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The Hami-Zhengzhou ±800 kV UHV DC project is the first DC project under construction in Xinjiang autonomous region and is planned to be put into operation in 2013. The influence of the project on the power grid stability in its commencement period is discussed and the impact of the project′s possible fault on the 750 kV AC connection project between Xinjiang and Northwestern power grid is checked. Based on the maximum power load of the Xinjiang power grid in the Winter period, a power flow and transient stability simulation analysis is conducted on the stability features of the power grid under the condition of monopole or bipolar lockout of the DC transmission lines and at the fault of the 750 kV AC transmission lines, and on the power grid stability variation with switch off measures of generators. Through simulation, the maximum transmission power of the AC section is determined under the condition of monopole lockout of DC system with different switch off measures of generators, and the effectiveness of generator switch off measures to increase the transmission capacity of AC power system is also verified. The conclusions obtained from this paper may provide a reference to the construction and security control strategy formulation of the Hami-Zhengzhou DC project.

Discussion on the Auxiliary Limiting Characteristics and Technical Indicators of Automatic Voltage Regulators

SU Wei-min, XIE Huan, WU Tao, SHI Yang, ZHAO Yan

2012, 45(12):  52-56.  DOI: 10.11930/j.issn.1004-9649.2012.12.52.4

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The automatic voltage regulator (AVR) plays an important role in maintaining generator terminal voltages and ensuring the power system stability. However, the auxiliary limiting characteristics of digital AVRs made by various manufactures are quite different, which has affected the safety of generator apparatus and stability of power grids, but enough attention has not been paid to for a long time. Based on the performance testing of AVRs and generator running power diagram, the differences in auxiliary limiting characteristics of various AVRs were analyzed and their possible impact on the safety of generator apparatus and stability of power grids were determined. Some proposals were put forward for testing analysis of the auxiliary limiting technical indicators of AVRs according to statistical data from experimental tests. The results can be used as a reference for strengthening management of the excitation system.

Effects of Generator’s Under-Excited Operation on Power System Low-Frequency Oscillation

XU Qian, WANG Zheng-feng, PAN Xue-ping

2012, 45(12):  57-60.  DOI: 10.11930/j.issn.1004-9649.2012.12.57.3

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The wavelet method is applied to identify the time-dependent frequency and damping ratio based on the PMU recorded data during Pingwei generator’s under-excited operation, and to analyze the relation of oscillation frequency and damping ratio with the variation of reactive power. Furthermore, the damping torque is used to analyze the reasons for the power system’s easy oscillation during generator’s leading phase operation with an OMIB system. Furthermore the effects of connection line’s reactive power variation in magnitude and direction resulted from multi-generator’s leading phase operation on regional oscillation damping were also studied and verified by simulating the Anhui network.

Reflection on a Multiple Power Grid Fault Caused by Inclement Weather

PANG Wei, ZHANG Sheng-nan, LI Xiang-xin

2012, 45(12):  61-65.  DOI: 10.11930/j.issn.1004-9649.2012.12.61.4

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A multiple power grid accident caused by inclement weather is analyzed, and some experiences are introduced. Dispatcher should deal with the incidents in order of importance and urgency; protect the grid structure as far as possible to prevent accidents from expansion under inclement weather; make full use of the online system to obtain information to assist decision-making in treating the incidents. The choices and risks that dispatchers are facing in dealing with and pre-controlling power grid accident are also introduced. In dealing with the accident, the fault equipment can be trial operated several times to prevent the accident from expansion, but it may repeatedly shock or even damage the power grid; In pre-controlling accident, a dilemma has to be faced, that is to operate the grid in ultimate state for power supply or by limiting some power load for safety margins. Some proposals are therefore proposed. First, study of the operating environment and operation level of transmission and distribution equipment should be carried out by relevant departments to build quantitative indicators for assessing the harshness of environment and the operational capability of equipment, and appropriate systems for real-time monitoring and analysis be developed to guide the dispatchers to handle incidents. Second, relevant provisions for pre-controlling accident should be formulated for dispatchers in their daily work. Finally, the monitoring system and remote operation function in control station should be further improved.

Analysis on a Transformer Lightning Accident

WANG Cheng-liang, WANG Guang-liang, BAO Yu-shu

2012, 45(12):  66-70.  DOI: 10.11930/j.issn.1004-9649.2012.12.66.4

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In order to investigate the causes for generator outage after a high-voltage auxiliary power transformer of a power plant experienced a lightning, the fault wave record was analyzed and tests were conducted on the oil chromatogram, insulation resistance, DC resistance, DC leakage, dielectric loss, low voltage short circuit impedance and AC voltage endurance. It was judged from the test results that the transformer worked normally after experiencing a large short-circuit current and the fault was caused by two-phase short-circuit and subsequent three-phase short-circuit. Based on the investigation of lightning protection grounding layout, with consideration of the condition of soil and thunder arc, the fault process is calculated and inferred that the lightning overvoltage firstly caused insulation flashover, and then continuous arc-discharge occurred under power frequency voltage, which in turn caused the two-phase and three phase short-circuit of the transformer’s low voltage side bus. Analysis indicates that the cause for the fault is that the layout of lightning arrester’s grounding wiring on the transformer’s wall area failed to meet the standard provisions. In the end, several countermeasures are put forward, which can provide an important reference for similar lightning fault analysis.

Experimental Studies on Electrical Insulation Performances of SF₆ /N₂ Gas Mixtures

SUN Peng-cheng, WANG Bang-tian, HONG Wen-fang, WANG Qi-zhong

2012, 45(12):  71-75.  DOI: 10.11930/j.issn.1004-9649.2012.12.71.4

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SF₆ gas is widely used for gas-insulated switchgear(GIS), which has led to public concerns about environmental pollutions. It is urgently required to reduce or eliminate the use of SF₆ gas in GISs so as to reduce the environmental pollutions. Various experiments were conducted to study the electrical breakdown characteristics of SF₆ gas and N₂/SF₆ gas mixtures under different mixing ratios and working pressures and in different electric-field structures. The testing results indicate that the N₂/SF₆ gas mixture, when 20%~30% of SF₆-gas is inputted in N₂, can attain 80% of pure SF₆ gas in electrical strength, but will have no significant increase in the strength with further increase of SF₆-gas ratio. Moreover, it was found that the extremely uneven structure of electric field will significantly reduce the electrical strength of the gas. The testing results has verified the feasibility of SF₆/N₂ gas mixture in substituting pure SF₆ gas.

Key Techniques for Electromagnetic Transient Simulation of Large-Scale AC/DC Power System

CHEN Xin-qi, GU Yi-lei, QIU Peng, LIU Zheng-fu, WENG Hua, XU Zheng

2012, 45(12):  76-80.  DOI: 10.11930/j.issn.1004-9649.2012.12.76.4

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To study the detail interactions between the AC and DC systems, it is necessary to adopt the electromagnetic transient simulation method. A fast data conversion approach for large-scale AC/DC power systems is presented in this paper, which can convert electromechanical transient simulation models of large-scale AC/DC power systems to the corresponding electromagnetic transient simulation models. Firstly, the large-scale AC/DC power system is reduced in PSS/E; and then the reduced system in PSS/E is quickly converted to the electromagnetic transient simulation models in PSCAD through programming methods; and finally, the detail electromagnetic transient simulation models of the large-scale AC/DC power systems is established. The steady-state verification and transient simulation under 3-phase symmetric faults are done based on the established electromagnetic transient simulation models of a real power system, and the simulation results demonstrate the consistent responses of the simulation models in PSCAD and in PSS/E, which shows that the proposed fast data conversion approach is valid.

Smart Grid

Comprehensive Assessment on Development Patterns of Smart Grid in China

YANG Fang, WANG Wen-di, GE Xu-bo, ZHANG Yi-bin

2012, 45(12):  81-85.  DOI: 10.11930/j.issn.1004-9649.2012.12.81.4

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Construction of smart grid in China is a complex systematic project, which needs the governments, power grid companies, power generation companies, equipment suppliers and various other stakeholders to make efforts together. Based on the stakeholder theory, and by combining multi-level fuzzy comprehensive evaluation method with dynamic matrix analysis, an index system and assessment method is presented for assessing the influence and interest level of China’s smart grid stakeholders in the industry development, which can realize the visual description of the relationship characteristics of various stakeholders and industrial development patterns of smart grid, and can also provide a support for policy formulation and strategic decision-making.

Wind Power Integrated Operation and Anti-Accident Measures in the Northern China in 2011

FAN Gao-feng, PEI Zhe-yi

2012, 45(12):  86-90.  DOI: 10.11930/j.issn.1004-9649.2012.12.86.4

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Wind power in China has been developing fast within the past couple of years and has become an important type of power supply. In order to understand the operation characteristics of wind power integrated with main grids, large amounts of data from wind farms in the Northern China(i.e. North China, Northeast China and Northwest China) are analyzed, which reveals that wind power in China is characterized by large scale, concentrated integration and long transmission distance with complicate intermittence in power balance. Based on the analysis on the main accidents of disconnection and the major technical points of the countermeasures against these accidents in 2011, some suggestions for anti-accident measures in the future are given.

Application of PON Technology to Overhead Transmission Line Monitoring

DING Jia-wen, TANG Jun, HU Bao-min

2012, 45(12):  91-95.  DOI: 10.11930/j.issn.1004-9649.2012.12.91.4

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Based on the transmission line monitoring problems such as increasing band width requirement and instable wireless transmission, a device was designed by using the Passive Optical Network technology(PON) to monitor HV transmission lines and towers, which, powered by inducted energy, transmits the acquired data based on the chain topology in PON system. By analyzing the models of transmission scenarios, the monitor function and power module were designed separately so as to provide the external monitoring device with transmission channel and power, which can integrate the existing monitoring resources of transmission lines, reduce the operation cost, and improve transmission quality.

Energy Conservation ang Environmental Protection

Test Research on NO_x Emission Characteristics of Baorixile Dried Lignite

XIE Jian-wen, FAN Wei-dong, NA Er-su, DONG Kun, LI Ying

2012, 45(12):  99-102.  DOI: 10.11930/j.issn.1004-9649.2012.12.99.3

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Lignite resources are rich in China. The advanced drying technology makes their large-scale utilization possible. The firing tests for four kinds of Baorixile dried lignite with different water contents are carried out under different proportions of staged air, different inlet positions of burnout air and different pulverized coal fineness in a one-dimension boiler with multipath air inlet. The results indicate that first, air-staged combustion can lower the NO_x emissions of the lignite substantially; second, to achieve the best result of NO_x emission control, the water content of the lignite is recommended as 0.9% to be the most adequate; third, through combustion adjustment and optimization, the NO_x emission level from the combustion of the lignite can be reduced to 250-300 mg/m³; and fourth, when designing a boiler firing dried lignite, attentions should not only be paid to the proportions of staged air and the positions of burnout air, but also to the coal powder fineness and the water content.

Assessment Model on Low-Carbon Benefits of Power Load Wave Reshape

CAI Tao1, SONG Bin-bin2, WEI Zhe1

2012, 45(12):  103-108.  DOI: 10.11930/j.issn.1004-9649.2012.12.103.5

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The thermal power generator’s coal consumption and emission is directly influenced by power load, and can be lowered by reshaping the electric load wave, and as a result, carbon emission reduction can be realized. The power grid's capacity for reshaping the electric power waves is discussed in the paper from the perspective of the effects of electric mobile, the development of energy storage technique, power peak reduction and energy conservation by cooperation with users. Based on this, the assessment model on low-carbon effects of electric load wave’s reshape is proposed. The amounts of carbon emission reduction from 2011 to 2020 are calculated with this model.