When multi-terminal HVDC system is used for long distance power transmission, DC line voltage drop and DC line power loss make significant impacts on the precision of voltage margin control, which makes the control of DC voltage unstable. Therefore, a precise voltage margin control method is proposed. In this paper a mathematical model in dq coordinate for VSC based multi-terminal DC power transmission system (VSC-MTDC). Then the value of voltage margin is calculated and revised in controller, with adequate consideration of the influence of line voltage drop and power loss on control reference value, based on power flow calculation for DC system. A simulation model of modular multilevel converter (MMC) based MTDC system in PSCAD/EMTDC is established to verify the correctness and validity of the proposed control method. The results show that with this method control characteristic deviations caused by unsuitable setting of voltage margin value could be avoided, and the control mode could be quickly switched under large power disturbance to improve the system stability.
A mixed integer non-linear programming (MINLP) model is built in this paper, which makes the construction of power distribution network as the target function, and is concerned with investment cost, power losses cost and operation cost of power distribution network, so as to guide the power grid planning for power companies. This model could use multiple discrete binary variables to optimize substation and its expansion plan, new transmission line. The accessing of distributed power sources to the distribution network is considered to maintain the radial operation structure of distribution network with the strict mathematical model. The point-branch and bound method is proposed to accurately solve the distribution network expansion planning model, which has been proved to be feasible.
The great earthquake of M_S 8.0 occurring in Wenchuan County, Sichuan Province on May 12, 2008 has made serious impact on the normal operation of Sichuan Power Grid, which damaged numerous substation equipments and led to outages of substations. On the basis of an investigation on the substation damages incurred by the earthquake, the damage causes of electrical equipments and structures of substations are analyzed and the main anti-seismic design principle and suggestions are proposed. The anti-seismic calculation of the main transformer in a 750 kV substation located in the intensity Ⅷ area shows that the main electrical equipments of substations in high seismic area are prone to be damaged. Therefore, it is proposed that the link mode between equipment and their foundation or supporting frames (cantilevers) should be determined by calculations, and the equipment with good anti-seismic capabilities should be choosed in advance according to the project’s practical needs, so as to improve the anti-seismic capability of substations and meet the requirement of no-damage under light earthquake and no-collapse under strong earthquake.
Through comparing the differences of parameter selecting in the basic wind speed, the uneven coefficient of wind pressure and the height variation coefficient of wind pressure at home and abroad, some conclusions are drawn in the design of suspension insulator strings. The results show that: in the aspect of basic wind speed choosing, there are great differences either in the wind speed conversion of observation density and time or in the return period between China and overseas countries; the selecting and the conversion method of wind pressure’s uneven coefficient have significant influence on conductor’s wind load; the different types of ground roughness have great influence on the values of height variation coefficient of wind presssure, which has not been defined explicitly in the transition area in domestic transmission line standard. So wind parameters should be observed on site for different terrains and heights, and these parameters can be optimized and improved through the accumulation of long-term observation data.
Owing to China’s special features in resources distribution, wind power on-grid mode, power composition and power grid structure, China shouldn’t simply draw on experience from developed countries like Europe and America. China should establish our own optimized power balance technology system in accordance with its own characteristics. Through analyzing the inherent characteristics of large-scale wind power, the main modeling methods for the fluctuation and uncertainty of wind power are concluded in this paper. The active power balance problems in the wind-coal-hydro mixed power grid are divided into several sub-problems: mid- and long-term and short-term unit commitment plan, rolling scheduling within one single day, real-time dispatching and so on. Finally, the research status and technical bottlenecks of those sub-problems are analyzed, respectively. The results have reference significance to the study and design of active power balance technology for the multi-time scale power system with large-scale wind power integration.
The control and protection system of converter valve is the core equipment of HVDC control and protection system, which is located in the lowest layer of layer distribution control and protection system. The working principle, on site test and operation condition of control and protection system for converter valve at Yulong Station pole Ⅱ low end in Jingping-Sunan ±800 kV UHV DC are presented. The equipment was put into operation for the first time with independent intellectual property.
A variety of signal cables are used in railway communication system to connect signal equipments, while HVDC power transmission lines in fault condition and DC side harmonics exert impact on railway communication lines. So the research on the influence degree of railway communication has practical significance to ensure railway transport efficiency. According to the principle of electromagnetic induction of power lines on weak current circuit, the theory and calculation methods of influence of HVDC power transmission lines on railway communication lines are introduced in this paper. Based on the limit of influence of HVDC transmission lines on communication lines in China, the induced voltage and disturbance voltage are calculated and simulated in PSCAD/EMTDC with the changes of different parameters, in which the influence degree of different parameters on induced voltage and disturbance voltage is obtained. Finally, some protective measures are suggested to restrain dangerous effects and interference effects.
With the rapid development of UHV power grid, the main electrical connection of UHV substation becomes more and more important to the safe and reliable operation of power grid. Therefore, the selection of suitable main electrical connection is a key work in the construction of UHV substations. According to the characteristics of Suzhou 1 000 kV UHV substation, he 500 kV main electrical connection scheme is analyzed in this paper. The techno-economic comparison between double-bus connection and two-thirds connection is carried out and the 500 kV main electrical connection of Suzhou UHV substation is suggested to adopt the double-bus connection, which not only could meet the requirements of the reliability of power grid, but also have some advantages of flexible scheduling, convenient expansion, small occupation of land and low investment.
In 750 kV Xinjiang-Northwest China No.2 channel power transmission and transformation project, controllable shunt reactor (CSR) devices should be installed in Shazhou 750 kV Substation, in order to solve 750 kV voltage control problems caused by wind flow variation. Taking the CSR in Shazhou 750 kV substation as an example, the CSR projects in service is summarized in order to optimize the design of the wiring and layout. The straightline-shape layout scheme for shunt reactor and control section is proposed, which has advantages of small occupation of land, low investment, easy operation and maintenance.
By focusing on the whole life cycle management of power plant and adopting advanced technologies in design, management and control, an intelligent, digital and visualized large power plant will be constructed, which represents the top level of integration system of management and control in the current power plants. In the development of digital power plant, it also experiences a process from part digitization to whole digitization. In the previous schemes of digital power plant, digitalization basically only means a part, or one function of the digital system. In this paper the panoramic architecture and scheme assumption of new digital power plant are proposed, based on the analysis of whole life-cycle management in power plant, and the definition, analysis and research of digital engineering system, digital control system and digital management system.
The waste heat of circulating water in power plant recovered by absorption heat pump and used for urban central heating is a new energy saving technology, but the standards for its performance acceptance test have not been drafted. In the heat pump performance acceptance test, the uncertainty evaluation method of COP, the direct and indirect measuring parameters are analyzed, as well as the corresponding calculation formula is proposed. Then taking the waste heat utilization project of circulating water in a 300 MW heating unit as an example, the uncertainty assessment is carried out for the COP test of heat pump. The uncertainty calculation results show that the availability of the test results can be effectively improved by reducing the parameters’ measurement uncertainty, such as the water flow in heating network, the condensate flow, the water temperature at inlet and outlet of heat network, and so on.
In order to improve the thermal economy of coal-fired units, the integration and optimization were implemented for the coupling mechanism of the parabolic trough solar collector and the regenerative system in conventional coal-fired units. Then the change of additional fuel specific consumption of equipments in 300 MW coal-fired units is analyzed in this paper before and after system integration, based on fuel specific consumption theory, to obtain the change trend under different solar radiation intensity. The results show that the additional fuel specific consumption of high pressure heaters and deaerators decrease with the increase in the solar radiation intensity, while those of condenser and middle/low pressure cylinders are exactly the opposite, and those of high pressure cylinders are essentially unchanged. The additional fuel specific consumption of steam turbine also increases with an increase in the solar radiation intensity, in which the additional fuel specific consumption of steam turbine increases 0.26 g/（kW·h）, and the saved coal reaches 11.26 g/（kW·h）, when the solar radiation intensity is 900 W/m2 in the integrated system design.
Combined with the construction of single pile foundation in overseas offshore wind farms, the geological and geomorphological conditions in the shallow water area in China are compared in this paper. The results show that single pile foundation is better than other types of foundation, which is more suitable for the wind power development in the shallow water area in China. Based on the construction experience of single pile foundation at the second stage of Rudong wind farm in Jiangsu Province, the feasibility and applicability of single pile foundation in the offshore wind power construction in China are discussed. Based on the load analysis, the design method, the manufacture ability of pile foundation, the comprehensive analysis of construction scheme, the feasibility of this type foundation applied in China is also discussed, which could provide references for future large-scale offshore wind power construction in China.
The feasibility that turbine-driven feed pump is used for the deep sliding parameter shutdown of supercritical steam turbine equipped with 100% turbine-driven feed pump is discussed, as well as the characteristics, operation and safety measures of deep sliding parameter shutdown are investigated. The results show that the deep sliding parameter shutdown is feasible, in which the descent speed of steam temperature, metal temperature, differential expansion and thermal expansion are uniform, and the bearing vibration is safe and controllable. The deep sliding parameter shutdown can reduce barring time by 4 days, save auxiliary power by 17.3×104 kW·h, and increase power generation by 10×104 kW·h
The arrangement of normal drain pipeline in high pressure (HP) heater in a large thermal power unit is unreasonable, which results the vibration of drain pipeline occurred repeatedly and endangers the safety of equipment. Some retrofits are carried out for the normal drain pipeline according to its arrangement in HP heater, such as excluding the water in normal drain pipe by using static pressure difference and condenser vacuum at the initial period of units’ start-up, which could completely eliminate the pipeline vibration, as well as prevent the equipment damage accident caused by vibration. New units could be optimized designed without low-point and U-tube, which could radically eliminate the pipeline vibration caused by small interstage differential pressure.
The frequent fluctuations of equipments and materials prices have serious influence on the investment and cost control in power grid project. In order to accurately grasp the trend of equipment prices and reasonably control the project cost, it has positive significance to research the influence factors on equipment prices. Combined with the equipment price and the bidding data, these factors are analyzed in this paper, which are divided into three types: policy factors, economic factors and enterprise behavior. The factors affected the equipment prices are mostly through two aspects: cost and profit. Finally, the factors influencing profits could be concluded in three aspects, supply-demand relationship, competition model and bidding strategy; while the cost is mainly concluded into raw material cost, labor cost, fixed cost, development cost and financing cost. The research could provide references for the reasonable control of project cost and the reduction of project investment risk.
Influence factors on the ultimate bearing capacity of steel tube tower’s joint are studied and explored. It reveals that the ultimate bearing capacity of the joint depends on the thickness and diameter of tubular, as well as the thickness and height of annular plate. The ultimate bearing capacity of annular plate joint of steel tube tower is researched by using test and finite element methods (FEM), and the test results have a good coincidence with FEM results. The formulas proposed through theoretical study are safe and reliable compared with other research results as well as Japanese standards, which can provide references for the determination and design of the ultimate bearing capacity of steel tube tower’s joint.
“Anhui Electricity Eastward Transmitting” project is the first 1 000 kV double-circuit UHV AC power transmission line adopting the design of steel tube tower in China, which has entered the stage of tower assembling and erecting. With the proceeding of UHV AC projects such as Huainan-Nanjing-Shanghai Project, Northern Zhejiang-Fuzhou Project and Ya’an-Wuhan Project, the design experience of steel tube tower in ’Anhui Electricity Eastward Transmitting’ project has great significance to the design work of future UHV AC projects. The achievements of standardized design in the power transmission project are summarized, the feedback on steel tube tower from construction and processing companies is collected and sorted out; as well as necessary improvements in future tower design are porposed. Finally, the typical node design plans for steel tube tower are concluded and the proper sizes of node configuration are suggested for the references to future UHV projects.
The control logic of AC system at convertor station directly affects the safe and stable operation of DC transmission system. By combining the test and operation of Suidong Converter Station in Yunnan-Guangdong ±800 kV UHV DC power transmission project, the problems of the control logic of AC system are analyzed in this paper, the improving measures are summarized and the problems still need to be improved are studied. The analysis on AC control system of convertor station could not only improve the operation and maintenance level of Yun-Guang UHV DC system, but will provide a good reference for other AC and DC power transmission projects as well.
A shut-down accident occurred in a power plant because of turbine’s partial frequency operation. The main reasons of frequent fluctuations of steam temperature behind high and low pressure bypass in HP casing exhaust lie in high metal temperature, which is caused by the closed non-return valve and the heavy turbine load. Meanwhile, the harm to turbines caused by the removal of high pressure cylinder under large load is analyzed. Finally, some suggestions on logical configuration of partial frequency protection, desuperheating water of low pressure bypass and non-return valve are proposed in HP casing exhaust. The operation practice show that the logical configuration scheme could avoid accidents and be safe and reliable.
Combined with the construction of remote control interactive system for 500 kV substation in Hunan power grid, the accessing scheme of newly installed data interactive system is analyzed in this paper based on the characteristics of integrated automation system in different manufacturers. The risk pre-control may occurred during the construction process and the system tests are discussed to provide references for similar project in the future.
The quad -bundle jumpers are commonly used in 500 kV power transmission lines. With the increasing restriction of transmission line corridors, transmission lines need to steer clear of the residential areas and buildings, which may result in the increase of tension angle towers in the lines’ design as well as the increase of loads in jumper installation and construction. At present, the on-tower capacity relation method is widely applied in the jumper installation, which has low efficiency and huge aerial operation workload. With several project practices, it shows that with the length accurately calculated in design process, the jumper is pressed and marked in material station, and transported to the site for suspension installation, which can greatly improve the efficiency of construction, reduce the aerial workload, as well as ensure the esthetics of process.
SF6 gas insulated switchgear (SF6 GIS) should be carried out AC voltage withstanding tests after installation and before operation. In this paper, the method of GIS AC voltage withstanding test is described, and its effectiveness of detecting internal abnormalities combined with the case is analyzed.
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