The orthogonal frequency division multiplexing（OFDM)， technology combining with frequency hopping(FH) technology will increase system capacity, improve transmission rate, and effectively resist multi-path fading and interference. Therefore, FH-OFDM technology is applicable in high speed communication of the power line. Based on the characteristics analysis of low voltage power line channel, the design scheme of a FH-OFDM system is presented. The system is simulated by MATLAB. It is shown that the bit error rate(BER) performance of the FH-OFDM system is better than that of the traditional OFDM and FH system.
The power supply system of metro light rail, applying DC traction and three-level inverter technology, is of strong volatility and abundant system harmonic, tending to affect the safe and stable operation of the power system. In the paper, the effects of the power supply system of metro light rail on the power quality of the public electricity grid are investigated under various operation conditions. According to the actual parameters of the locomotive, the tractive power supply system and the public electricity grid, a complete model including traction motor and public power system is established and verified by the on-site measurement data. Based on the model, it is concluded that the harmonic injection in the public electricity grid by the power supply system is the characteristic harmonics induced by the 24-pulse rectification and inverter working, however, both the negative sequence and the voltage flicker value meet the national standards. By changing the operational status and numbers of the train, the total harmonics can even reach 17% at the startup of traction motor. With the increasing numbers of the train, though the voltage decreases sharply, it accords with the standard.
With the speeding up of transmission project settlement in State Grid Corporation, improving settlement efficiency and reducing audit risk are of importance in order to achieve the time node requirements and the settlement depth. In this paper, a mode of delegating a third party to settle the account is introduced, and the detailed flow chart of entrust settlement also presented, where the settlement time is shortened. The incentives for the cost advisory unit is discussed based on the principal-agent theory in the game theory, as a result that the fixed payment model and the absolute performance incentive model as well as their solution methods are presented, providing theoretical support for calculating the settlement of consulting fees. It is shown from the examples that the model established in this paper is very useful, which could provide basis for the calculation of consulting fees and also inspire the healthy development of settlement patterns of the power transmission project in China.
The NOx emissions of the double tangential firing boiler in 1 000 MW ultra-supercritical unit are systematically investigated based on on-site combustion tuning tests, on which the effects of excess oxygen level, boiler load, quantities of over-fired airs, burner air amount and distribution of the main combustion zone, mill groups in service, burner tilting angle, and coal property are studied. For the boiler equipped with advanced low-NOx combustion system, it is shown from the tests that the coal property, excess oxygen level and boiler load are important factors affecting NOx emission. The NOx emission increases linearly with increasing oxygen level. However, the burner air amount and distribution of the main combustion zone have weak influences on NOx emission concentration when multi-level combustion is achieved by keeping large quantity of over-fired airs. Based on this, the empirical correlations between NOx emission concentration and main operation factors are established by multiple linear regression, which can be applied to predict the boiler NOx emissions and guide NOx combustion control during operation.
Based on the grid-connection engineering design and practice of several regional PV(photovoltaic) power plants in He-xi area of Gansu province, a bundled grid-connection scheme with good economy, reasonability and operability is presented. In this scheme, some important problems, such as transient characteristics, dynamic reactive power compensation configuration, harmonic analysis and suppression for grid connection point, are studied by PSASP(power system analysis software package) simulation, as a result that a new connected mode with several PV power plants bundled is formed, and its benefit to similar projects as references.
According to characteristics of tower foundation on sloping groud, four kind of solutions are proposed to match up between the base and the tower structure of transmission line. The four proposals are introduced respectively as, equal tower leg length with equal foundation, equal tower leg length with unequal embedded foundation, unequal tower leg length with equal foundation, and unequal tower leg length with unequal foundation. The match up principles are also given. The effective uplift resistance depth was supposed to reflect the bearing capacity of foundations on sloping ground.
This paper introduces the noise control method in Fengxian ±800 kV UHVDC converter station. Based on the technical characteristics of UHVDC converter station ,the mobile Box-in noise reduction structure is proposed , and thedesign principles and design procedure is introduced. Moreover, the structural design characteristics and its optimum solution are given as well. The solution could provide reference for future design of mobile Box-in noise reduction structure for UHVDC converter station.
The evaluation of power plant grid-connected operation and auxiliary services has realized the unified and flexible management of grid-connected operation assessment and auxiliary services compensation through the establishment of evaluation model. The evaluation system has enhanced the fair, just and open management for power plant via economic means and improved the accuracy and intelligence of power grid dispatching. Functions are realized in the system of assessment management, auxiliary services, model management, billing management, data integration, information distribution, and system management etc. The system adopts intelligent fault-tolerant and correction technology to automatically identify and process the bad data during massive data calculation and solves the problems of large amount of data and messy types.
The first application of 1 500 MVA transformer in 500 kV load-center substation is introduced in this paper. Based on the analysis of the power distribution equipment at all levels with the increasing substation capacity, the application of new technology and new equipments, such as high-impendance transformer，220 kV equipment with large capacity and 66 kV large-capacity capacitor bank etc, are presented, providing references for the related technicians.
Yunnan-Guangdong UHVDC project is the first ultra high voltage DC transmission project with ±800 kV in the world. In this paper, the voltage calculation formulas are presented of single valve group and double valve groups with and without DC line in the open line test (OLT). Taking the open line test of single valve group and double valve groups in Suidong converter station as an example, the relationship and the error between the measured and the calculated results of open circuit voltage are analyzed. It is concluded that the voltage protection should not be applied in open line test.
The lighting accidents of distribution transformer in qinzhou of Guangxi occur seriously so that it is required to reform the lighting protection. Based on the field investigation and experiments of measuring the earth resistance, it is proposed by relevant theory that the distribution transformers suffering lighting strike is due to the defective lighting protection, including unequipped low voltage arresters,problematic earth device and earth resistance beyond standard value. Based on the analysis, some measures are proposed such as installing low voltage arresters, connecting the coilout at low voltage side with cable and overhead line, reforming earth device and reducing the ground resistance.
The overvoltage and insulation coordination are the key technologies in the Ningdong-Shandong ±660 kV HVDC transmission project, and have great influence on the feasibility, reliability, economy of the project. In this paper, combined with the insulation coordination features of the project, the power frequency, harmonic vibration, operation and lightning overvoltage level are analyzed by the overvoltage electromagnetic transient simulation. Based on the simulated results, the insulation level of equipment in converter station is determined, providing references for the matching of the engineering equipments.
Control strategy of voltage source converter (VSC) based multi-terminal HVDC transmission system is investigated in this paper. DC voltage feed-forward compensation and controller configuration of double closed loop based on linearized feedback of input and output are applied in controller design of the converter. This approach can realize decoupled control of active and reactive power. Meanwhile, it can improve the voltage and current waveforms at AC side of the converter. Multi-point DC voltage control strategy is proposed for stability control of the multi-terminal HVDC system, which is able to improve power balance ability of the multi-terminal DC(MTDC) system and enhance reliability and economy of system operation. Simulation is performed on a VSC-MTDC system with five terminals and the results show that the proposed control strategy with good dynamic characteristics is suitable for integration of distributed generation system and power system.
Wind energy is widely developed and applied as one of the most commercial prospect renewable energy, as a result that significant advancement of wind power generation and its relative technology are achieved. In the paper, the wind power generation and its relative technology are reviewed, including the types of wind power generation system, performance and feature of generators applied in wind power generation system, and development tendency of future wind power generation technology, which providing references for well learning about the present status and development tendency of wind power generation at home and abroad.
The thermal power plant in Linfen of Shanxi province firstly applies the technology in China that the feedwater pump turbine directly exhausts into the air cooling system of the main steam turbine. In the paper, the corresponding technical characteristics, design scheme and control method are introduced, providing references for similar projects.
The mistrip of high-voltage side circuit breaker of generator-transformer unit occurs and is induced by 220 kV line-to-ground fault in Huaneng Power Plant of Chaohu. In the paper, the causes of the accident are analyzed by constructing models, that the high frequency components invade into the trip circuit by the distributed capacitance of secondary cable, providing references for similar malfunction.
Based on the construct proportion，system accessing conditions and the main electrical connection requirements of the second power station in Pingdingshan，the paper proposes 4 main electrical connection programs of the first stage project. By comparing from the technology aspect and the economy aspect，the paper recommends that the project uses one and a half circuit breakers connection program.
The load-rejection test of a 705 t/h CFB(circulating fluidized bed) boiler is introduced in this paper. Considering the large thermal inertia of CFB boiler, the combustion and the bed temperature could been maintained in normal operation conditions by adjusting the coal feeding and the primary/secondary air flow. The parameter control methods of steam temperature and pressure are also discussed. During the period of load rejection, the parameters of bed temperature, differential pressure of furnace, the steam temperature and pressure are analyzed systematically, as a result that the unit could be synchronized and reloaded rapidly after load-rejection, and the test costs and recovery time distinctly decrease. The experiences can provide references for the load-rejection and quick load change of the same type unit.
Combined with the advanced flue gas desulfurization(FGD) technology at home and abroad at present, the technical and economic comparisons and optimization proposals are implemented of seawater desulfurization plan for two 350 MW and two 50 MW units in the thermal power plant, including ensuring the safe and reliable operation of the plants, optimizing SWFGD(seawater FGD) system and general layout, saving the project investments and lowering operating costs, The preferred plan of SWFGD system for this kind of project is recommended.
By surveying anti-corrosion situation of the flue gas esulfurization(FGD) chimney in the coal-fired power plants, and combined with the engineering practice of Pingdingshan Yaomeng Power Co., Ltd., a composite anti-corrosion plan about light weight vitrified ceramic tile for 1#& 2# unit chimneys is presented and implemented with good results. In the end, some suggestions are proposed about the anti-corrosion of FGD chimney.
Influence of electrical joint compound on anticorrosion property of electrical contact is studied in this paper. Three metal connection samples including Al-Al, Cu-Al, Cu-Cu are selection to conduct the salt spray test. The test result shows that the anti-corrosion property of metal is improved remarkably when the electrical contact is employed, especially in Al-Al and Cu-Al contacts. Meanwhile, the contact resistance is reduced, which highly improves the reliability and the stability of the electrical contact.
The application of web geographic information system(Web GIS) in power transmission and distribution projects is introduced in the paper, taking the management information system for power transmission and distribution as an example. By using spacial basic data and related design products, the management information system visualizedly provides a spacially collaborative management platform for the owners, developers, construction organization and supervision units. By showing the spacial position, work process and other real-time data visually, accurately and entirely, the system provides an advanced and assistant technical support for project construction, and presents electronic documents with entire spacial position information for production and operation department. The application of the system obtains good results in the field management of power transmission and distribution projects.
There are many problems in the secondary wiring and logic design of GE generator-transformer unit protection since the four units successively putting into operation in Huaneng Yuhuan Power Plant. It is analyzed and improved about the generator-transformer unit protection, such as starting fast cut back of auxiliary power, zero-power triping of the line section, overexcitation protection of generator, secondary circuit wiring and logic design. It is shown that the protection functions are more perfect, effectively ensuring the safety of power system.
The Zhoushan-mainland transmission project over Luotou water channel is the project with the largest crossing in the world. The 370-meter high tower is complicated and located in the island, of which the construction is difficult. In this paper, the construction technologies of the tower are summarized in detail, including the overall program, pole structure, the specific construction and etc, providing references for similar projects.
Zhoushan-mainland transmission line locates in the international waterway, therefore some technical problems such as intensive tension, strong wind and non-closure of navigation need to be solved during the construction. In the paper, the installation scheme of overhead conductor and ground wire are introduced including the determination of key technical parameters, selection of rope pulling methods, and extension of primary and transition guide rope. Furthermore, the measures and strategies for solving the vital technical problems are provided so that the installation scheme is optimized and the successful implements of large-crossing stringing ensured.
The inner guy wire is an important component for the gin pole used in the erection of 370-meter high tower. Due to the large leg span and heavy single component of the high tower, the high speed wind environment throughout the year caused by the high towers location in island and high operating height of the gin pole, it is shown from the analysis and the calculation that setting the inner guy wires with four groups will cause the inner guy wires bearing excessive force which lead to a great difficulty in the construction, low anti-twist characteristics and serious deflection of the gin pole. Therefore, the anti-twist inner guy wires with 12 groups are innovatively used in the tower erection based on the finite element analysis and tests of the gin pole. The successful application of this new method in the erection of Zhoushan 370-meter high tower provides a new way to set inner guy wires for similar projects.
Due to the complication of the smoke duct welding of the No.1 unit in China Power Investment Corporation, Sichuan Fuxi Power Plant, the CO2 shielded arc welding technology is used. This paper introduce the feature and measurement of CO2 shielded arc welding technology. The techno-economic analysis is conducted comparing with traditional hand welding technology. The results show that CO2 shielded arc welding technology improves welding quality, and saves costs.
