Table of Content

05 April 2013, Volume 46 Issue 4

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Generation Technology

Design and Implementation of Online Vibration Monitoring System for Turbine-Generator Sets

FU Lei-yang, WANG Jiang, ZHU Jun, RAO Yuan

2013, 46(4):  1-5.  DOI: 10.11930/j.issn.1004-9649.2013.4.1.4

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Vibration is very harmful to large turbine-generator sets. It may cause the turbine to shut down, or even the shaft to break. Offline periodic monitoring cannot realize continuous monitoring. By contrast online monitoring and analyzing mainly focus on accident prevention and can discover faults early. An online real-time vibration monitoring and analyzing system based on Applet+JavaEE(MVC)+MySQL technology is developed, capable of displaying multi-window graphics on one webpage, and exchanging and messaging data as well. By integrating the power plant’s network with the Internet resources, end users can perform state monitoring and remote real-time monitoring in one Web browser. The system has more than one map and has the functions of making comparisons with historical data and data uploading, to meet the needs of users at different levels, such as power plants and groups.

Online Temperature Monitoring and Forecasting System for Evaporating Tube Wall in Supercritical Boilers

LIU Fu-guo, XIN Ben-quan, LENG Cheng-gang, ZHOU Xin-gang, LV Gui-cun, HU Zhi-hong, JIANG Bo

2013, 46(4):  6-10.  DOI: 10.11930/j.issn.1004-9649.2013.4.6.4

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Monitoring of evaporating tube wall temperature mainly relies on a certain number of thermocouples outside the furnace and it lacks effective methods inside the furnace. Through the modeling of wall heat transfer, furnace heat flux distribution and tube dimension as well as the simulation of forced convective boiling heat transfer in the wall tubes, online measurement of the whole-furnace evaporating wall temperatures and the firing coal calorific value is achieved with a monitoring and forecasting system successfully developed and applied for a 1 000-MW supercritical boiler. The performance tests on the system are carried out, which show that the difference between the on-line monitoring value and the value measured by the thermocouples ranges from -2.47% to +3.83% and the error of the on-line monitoring of the coal low calorific value on as-received basis ranges from -6.99% to +5.32%.

Research on Application of Tekla in Mechanical Module Design in Nuclear Power Plants

TANG Min-jing, LU Qin-wu, XIE Hua, WANG Zeng-chen

2013, 46(4):  11-15.  DOI: 10.11930/j.issn.1004-9649.2013.4.11.4

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At present, PDMS or PDS is widely used as the software in designing nuclear power projects. However, since the mechanical module consists of special cohesively-assembled items and its design needs good coordination among designers from different specialties, it is difficult to accomplish all the design work by using PDMS or PDS alone. For this reason, combined with the practical engineering design, the process for designing mechanical module and the advantages of Tekla in steel structure design are analyzed, resulting in that Tekla can be applied to mechanical design step by step in three stages. In-depth study on the working mode of adopting Tekla in module design is also conducted with relevant process schemes proposed, which can be a reference for improving the fitness of steel structure design for other special module design and boosting the working efficiency of module design.

Survey and Analysis on Thermal Control Regulation System for Coal-Fired Units in Electric Power Industry

SUN Chang-sheng, YIN Song, SU Ye, ZHANG Peng, DING Jun-hong

2013, 46(4):  16-20.  DOI: 10.11930/j.issn.1004-9649.2013.4.16.4

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In order to enhance the communication and exchange of the experience in improving the thermal control regulation system among power plants, explore the effects of the system optimization on energy conservation and promote the healthy development of the system, the Thermal Automation Technology Committee of the electric power industry conducts a survey on the operation of the system in the industry, analyzes the situation of the software optimization and its application in the system, and proposes the work to be carried out in the application of the process control system for power plants at present and in the future.

Experimental Research on Low-Oxygen Feedwater Treatment for Once-Through Boilers

FENG Li-kui, QIAN Zhou-hai, ZHOU Chen

2013, 46(4):  21-24.  DOI: 10.11930/j.issn.1004-9649.2013.4.21.3

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The oxygenated treatment experiments are carried out in the high-pressure feedwater system of the once-through boilers for 1 000-MW and 600-MW supercritical units to study the feasibility of inhibiting corrosion in the feedwater system by low-oxygen treatment (oxygen mass concentration <30 μg/L). The low-oxygen feedwater treatment experiments are conducted for the feedwater system separately when and after the passivation film is formed,. The results show that the amount of oxygen added to the feedwater must be kept at a higher levelduring the passivation film formation. Once the passivation film comes out, it can stay long and stable with the oxygen mass concentration ranging between 10 and 20 μg/L for the protection of the feedwater system. Aiming at inhibiting the corrosion of draining systems, the pH value of the feedwater should be maintained above 9.3 when the low-oxygen treatment is applied.

Analysis on Absorption Heat Pump in Heating Units

LI Jian-feng, MA Qing-zhong, HUANG Hai-tao, YAO Guo-fu

2013, 46(4):  25-27.  DOI: 10.11930/j.issn.1004-9649.2013.4.25.2

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In order to evaluate the effect of the absorption heat pump used in heating units, an energy-saving computing model of the absorption heat pump is established and the efficiency of the system with the absorption heat pump is calculated and analyzed for a 300-MW heat supply unit. The results show that the extraction steam from the unit can be saved substantially assuming the same heating load if the absorption heat pump is installed. Therefore, the benefit of installing the pump generally comes from the power generation increase of the steam turbine rather than the heat simply recovered.

Exploration of Adopting 623 ℃ Reheat Steam Temperature in 660-MW Ultra-Supercritical Type ∏ Boilers

ZHAI De-shuang

2013, 46(4):  28-31.  DOI: 10.11930/j.issn.1004-9649.2013.4.28.3

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The 623 ℃ reheat steam temperature will be adopted for two 660-MW ultra-supercritical units in phase II of a power plant project. This is the first case for type Π boilers in the world. The operation of the 660-MW ultra-supercritical units with 603 ℃ reheat steam temperature is introduced, and then the design of elevating the reheat steam temperature up to 623℃ is presented. Further, related economic analysis is conducted and security measures are proposed. Finally, some suggestions on the installation, debugging and operation of the two boilers are also included.

Power System

Study on Tower Types of 1 000 kV and 500 kV Four-Circuit AC Transmission Lines on One Tower

ZHANG Lu-qi, HAO Yang, ZHANG Xiao-li, WEN Fan, ZANG Guo-hua, WEI Peng

2013, 46(4):  32-36.  DOI: 10.11930/j.issn.1004-9649.2013.4.32.4

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Application of the four-circuit on one tower transmission technology is an effective way to solve the corridor shortage problems for transmission lines, and to improve transmission capacity and build the resource-saving power grids. Based on UHVAC-dedicated technological research results, a study was made through theoretical analysis and numerical calculation on the tower types of 1 000 kV and 500 kV four-circuit AC transmission lines on the same tower. Based on the experiences of EHV four-circuit AC transmission technology, two typical tower structures were analyzed in terms of electromagnetic environment, lighting performance, icing verification and economy. A reasonable tower type was selected, and the tower head layout scheme was proposed, which can provide a reference for tower design of 1 000 kV and 500 kV four-circuit AC transmission lines.

Contrast Study of Wind Load Characteristics for Transmission Towers Based Foreign Standards

PAN Feng, CHEN Jia-miao, NIE Jian-bo, GUO Yong, YING Jian-guo

2013, 46(4):  37-42.  DOI: 10.11930/j.issn.1004-9649.2013.4.37.5

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With the complex interaction between wind and structure, transmission towers belong to wind-sensitive structures and the wind load becomes the main problem in structure design. With the increase of transmission line projects undertaken abroad, to accurately understand the wind load specifications in foreign standards is a fundamental and key step for designing transmission towers. In this paper, an analysis is conducted on the calculation principles of wind load for towers in different international transmission line codes (including ASCE74-2009, IEC60826 and BS EN50341), and a calculation method for tower wind load was obtained. Based on a typical transmission tower, the wind loads of the tower body and cross-arm were calculated respectively in accordance with foreign standards. Meanwhile, the wind load distribution characteristics of structural layers were analyzed and compared with those calculated with Chinese standards. The wind load characteristics of transmission towers in foreign standards obtained in this study may be referred in the design of wind loads for transmission towers in foreign countries.

Calculation and Analysis on Electromagnetic Coupling Component of AC/DC Transmission Lines on the Same Tower Built in Same Corridor

WU Chi, ZHANG Long-wei, ZHU Jun, WU Guang-ning, SHI Chao-qun, WU Jing-wen

2013, 46(4):  43-47.  DOI: 10.11930/j.issn.1004-9649.2013.4.43.4

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To make full use of the overhead line corridor, development of AC/DC transmission lines on the same tower will be a future trend for power grid. It is therefore of great significance to study the electromagnetic coupling interference of AC/DC transmission lines on the same tower. The coupling model of double-circuit AC and single-circuit DC transmission lines was established based on PSCAD/EMTDC in this paper. The results show that the electromagnetic coupling component of DC lines are smaller when AC lines are arranged in inverted triangle and the phase conductors are arranged in ABC/ACB. The balance of electrical parameters are severely damaged by AC lines fault, leading to the increasing of electromagnetic coupling component of DC lines. The more the coupling ground wires are, the better the shielding effect is. The shielding effect tends to saturation when the number of coupling ground wires reaches a certain number.

Analysis of Partial Discharge in GIS under Impulse Voltage by Using Quadratic Short-time Fourier Transform

REN Zhong, DONG Ming, WU Li-yuan, REN Ming, SI Wen-rong

2013, 46(4):  48-53.  DOI: 10.11930/j.issn.1004-9649.2013.4.48.5

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In order to analyze the characteristics of signals of partial discharge(PD) in GIS under the impulse voltage, a kind of time- frequency transform theory called the quadratic short-time Fourier transform was applied in analysis of the PD pulse sequence to get the distribution of energy and variation law of signals in the time-frequency plane. In this research, the time-frequency transform of a kind of typical PD pulse sequence containing noise was simulated, which showed that PD pulse could be extracted efficiently. Besides, a kind of spikes defect model was installed in the bus segment of 220 kV GIS and the PD of GIS under impulse voltage was detected. By time- frequency analysis of experiment data, it can be found that the theory of quadratic short-time Fourier transform can be applied in analysis of PD signals efficiently and the variation law of time-frequency spectrogram was affected by the length of window function.

Influence of Common Grounding-pole on HVDC Transmission Control System

WANG Chun-cheng, SHI Shi-hong

2013, 46(4):  54-57.  DOI: 10.11930/j.issn.1004-9649.2013.4.54.3

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With the large scale construction of EHVDC/UHVDC transmission projects, common grounding-pole design of multi-circuit systems has become the trend for its land-and cost-saving. However, the common grounding-pole technology has not been studied comprehensively and systematically in terms of its influence on DC control system, such as, whether or not it has influences on the control system, how and in what extent if it has, etc. Therefore, based on the design parameters for Xiluodu HVDC project, the influences of the common grounding-pole on each circuit control system connected with the pole were analyzed systematically. Particularly, considering the situation that two circuits use a common converter substation together, its influences on the coordinative control between two circuits were studied. The results show that the influences of the common grounding-pole on Xiluodu HVDC transmission control system can be ignored.

An Improved Control Strategy of Load Distribution for a Microgrid in Islanded Operation

ZHAO Feng-xian, SUN Li-ying

2013, 46(4):  58-62.  DOI: 10.11930/j.issn.1004-9649.2013.4.58.4

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Considering an intensive coupling between the active and reactive power because of resistive line impedance in microgrids, the generation units adopting traditional V/f droop-control strategy can’t effectively achieve the distributed power source’s output power varies as the load power changes in island mode. The paper proposed a coordinate rotational transformation based on virtual power V/δ droop control strategy to achieving load distribution in islanded operation with distributed generation units. The strategy achieves the decoupled active and reactive power control through orthogonal transformation matrix, and the output power limiting measures feedback function and derivative function employs additional derivative terms with modified gain respectively, which guarantee stability and good transient response and load sharing in microgrid. The Matlab simulation results verify that the proposed control strategy is feasible for increasing or cutting load and cutting one distributed generator in islanded microgrids.

Mitigating Thermal Power’s SSR by Additional Damping Controller of DFIG

LEI Hong-yun, ZHENG Chao, YUE Xing-hua, XU Guang-nian, BAO Jian-fei

2013, 46(4):  63-68.  DOI: 10.11930/j.issn.1004-9649.2013.4.63.5

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Combined power delivery from thermal and wind power bases is the practical needs in China. Series compensators are usually installed in transmission channels to improve the capability of the delivery system, but may cause sub-synchronous resonance (SSR) on the thermal power units at the sending end. In order to solve the problem, the impact of wind power integration on the nearby thermal power units’ SSR is analyzed quantitatively by time-domain simulation and Prony damping ratio identification, in which the IEEE SSR first benchmark modified model with a wind farm is used, and an additional damping controller of wind turbine is designed according to principles of phase compensation, which can provide positive damping in sub-frequency domain and eliminate SSR by adjusting its reactive power dynamically. In the meanwhile, the active power outputs of doubly-fed induction generators (DFIGs) are improbably affected due to their decoupling control functions. The simulation results show that this control strategy can improve dynamic characteristics of combined power delivery system of high capacity with series compensation and increase the trans-region absorbing capacity of large scale wind power.

A Robust State Estimation Method Based on Exponential Weight Functions

CAI Ning-lu, YAO Li, LIN Ji-keng, WANG Gang, WANG Wen-jie, LUO Wei-hua, LIU Tao, WANG Xu-dong

2013, 46(4):  69-73.  DOI: 10.11930/j.issn.1004-9649.2013.4.69.4

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State estimation of power system is the basis of all the high level application and analysis for dispatch centers. Against the bad convergence of the WLAV(weighted least absolute value)-based state estimation method, a new robust state estimation method based on exponential weight function (E-LAV) is presented in the paper. This method uses an exponential weight function to replace the discontinues function of WLAV to improve the poor convergence. The results of the sample system of 4-node system and the IEEE 118-node system show that the E-LAV-based state estimation method not only owns the similar convergence as WLS-based method, and also owns a strong robustness. Through modifying the weight matrix of the least squares, the proposed new method has good prospects for application in practical engineering.

New Energy

Modeling and Simulation of AWS Based Wave Energy Conversion System

WU Feng, YANG Xin, JU Ping, ZHANG Xiao-ping

2013, 46(4):  74-78.  DOI: 10.11930/j.issn.1004-9649.2013.4.74.4

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Archimedes wave swing(AWS) based wave energy conversion(WEC) system is the first device to adopt the direct-drive power take-off technique, which leads to a simple energy conversion configuration with a higher efficiency. The AWS based WEC system consists of a floater and a linear permanent-magnet generator(LPMG). The model of the AWS based WEC system was built in this paper. The transformation between the abc and dq frames of reference for the model of a LPMG was conducted. The model of a LPMG in dq frame of reference is the base for its controller design. The model was implemented in Matlab simulation system, by which the effectiveness of the model was tested under no-load and R-C load conditions.

Operation Monitoring and Production Management System for Regional Wind Farms

BAO Da-en

2013, 46(4):  79-82.  DOI: 10.11930/j.issn.1004-9649.2013.4.79.3

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A lot of wind farms are usually scarted in areas abundant with wind energy resources and mounted with different kinds of supervisory control and data acquisition(SCADA) systems,which not only makes great difficulties to the wind power production management, but also causes a lot of problems to scheduling and safe operation of power grids. Therefore, an operation monitoring and production management system was developed for regional wind farms. This system realizes the SCADA function with WEB and integrates different data protocols to deal with data from different SCADA systems uniformly, which makes it possible to implement the centralized control and management of the wind farms and lays the foundation for “unattended production” of wind power.

Information and Communication

Video and Image Identification Management System for Transmission Lines

SUN Feng-jie, QI Jing-liang, LI Yuan-yuan, FAN Jie-qing, ZHANG Min

2013, 46(4):  83-88.  DOI: 10.11930/j.issn.1004-9649.2013.4.83.5

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A video and image identification management system for transmission lines is developed and implemented in this paper. The system has three modules, including remote monitoring module, fault identification module and information management module. The image processing technology is used in the fault identification module to realize two functions of ice thickness calculation and conductor galloping amplitude calculation. Different functions work in a coordinated way according to the identified faults. The information management module, which is based on the database, can manage the device information, alarm information and micro-meteorological information as well as identification results. In addition, the system sets certain micro-meteorological parameters as conditions to call the identification subprogram. Once the micro-meteorological conditions of the monitored sites reach the conditions, the identification program will be started, greatly improving the reliability and efficiency of the system.

Application of RFID Tag in Electric Power Asset Linkage

ZHANG Hong-zhan

2013, 46(4):  89-92.  DOI: 10.11930/j.issn.1004-9649.2013.4.89.3

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Emerging as an auto-discern technology in the 1990s and having gradually become matured, the radio frequency identification (RFID) technology has been applied to material management, asset management and intelligent checking and some other business in electric power industry. The application of RFID technology in automatic transfer of funds in power system was discussed. The RFID provided a technological support for the automatic transfer of funds and helped to preliminarily realize the linkage of the materials, equipment and assets on the ERP system and production management systems.

Energy Conservation and Environmental Protection

COS Hydrolysis Process of Desulfurization System for IGCC Power Plants

ZHANG Rui-xiang, GAO Jing-hui, LING Tong-tong, ZHU Sheng-bao

2013, 46(4):  93-97.  DOI: 10.11930/j.issn.1004-9649.2013.4.93.4

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The COS hydrolysis system of gas purification in one integrated gasification combined cycle(IGCC) power plant is introduced. Through the optimization of the startup modes and operating conditions of the COS hydrolysis system, the best operating condition is determined from experimental researches, i.e., 180 ℃ of the layer temperature of the COS hydrolysis, 1451 h^-1 of the space velocity, and the temperature of raw coal gas at the process gas cooler outlet between 50 and 60℃. Operated under this condition, the COS hydrolysis conversion rate can reach 92.5%. In addition, the common issues in the operation of the COS hydrolysis system are analyzed, which concludes that the oxygen and water vapor contents of the raw coal gas shall be strictly controlled.

Characteristic and Prevention of Spontaneous Combustion in Power Plant Coal Yard

HAN Hong-bin

2013, 46(4):  98-103.  DOI: 10.11930/j.issn.1004-9649.2013.4.98.5

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Combined with production practice, the spontaneous combustion process of coal in storage is described. The characteristics of coal yard spontaneous combustion, such as the coal qualities, yard locations and climate conditions are summarized. The effective measures to prevent the spontaneous combustion are also put forward, including choosing the coals of good stability as bed coal to pave the coal yard, tamping the coal pile bottom periphery, putting the coal of high-risk spontaneous combustion in storage in special areas or mixing it with high-ash content coal for storage, adopting the right way to extinguish the fire with water under different spontaneous combustion scenarios; reducing the windward side area with reasonable group piling ; prioritizing the high-risk coal for firing. After taking these measures, the frequency of coal yard spontaneous combustion in one power plant is gradually decreasing. So far no spontaneous combustion has ever taken place in a continuous long period.