To address the measurement deviation of primary air flow rate at vertical-shaft mill entrance in direct-fired system for coal-fired power plant, the computational fluid dynamics (CFD) software is used to simulate the flow field in primary air duct. The computed flow rate is compared with the measured values, which indicates that the small aperture of symmetrical damper will produce flat fluidic wall-attachment phenomena and makes downstream flow field uncertain and badly stratified, so random arrangement of measuring points cannot reflect the actual flow reasonably. It is proposed to choose the appropriate position for flow measurement based on the CFD simulated results.
The key for dynamic calculation of fan bridge of direct air-cooling system of coal-fired power plants is to determine the oscillation force of fan bridge. Based on measurement of the strain of fan shaft during fan operation, the strain curves of the fan shaft are obtained. According to the measured strain curves, the oscillation force characteristics of the fan bridge is analyzed and the calculation method of oscillation force is proposed, which can be used as a reference for . self-design of direct air-cooling system in China.
On the background of Xulian Transmission lines in the mining subsidence region, the coal mining status under these subsidence areas was analyzed. The support displacement of the transmission towers because of typical bars’ stability failure was set to be the safety criterion. And the ultimate deformation of the tower attained through analysis was considered as the deformation limit of the tower. According to the expected results of the surface deformation in subsidence area, the reliabil-ity of the transmission lines across the subsidence area was assessed. Analysis shows that the surface deformation of the old mined-out area has little impact on the safety of the transmission tower. However, when coal mining is end, it is necessary to adopt composite foundation, that's because the composite foundation's anti-deformation capability is enough to withstand the impact of the surface deformation. As to the large inclination and the surface subsidence, appropriate technical measures are needed. Currently transmission lines and towers in the subsidence areas were found run-ning in good condition without abnormalities.
Communication systems provide important support for smart grid. But there has been a bottleneck in the field of distribution and communication network due to the absence of effective communication methods. This paper first introduce the characteristics and information requirement of smart distribution network, then gives an introduction and comparison on the communication technology such as passive optical network （PON）, world interoperability for microwave access（WiMAX）and power line carrier（PLC）.Finally, based on an economic and technical comparison, a technological application scheme and a system structure for distribution and communication network were presented. KEYWORDS: smart grid；passive optical network（PON）；world interoperability for microwave access（WiMAX）；power line carrier（PLC）；communication network；networking technology
With the construction of UHV power grid, influences of bus arrangement systems applied in UHV substations on the reliability of the entire power grid have become more and more important. Therefore, the coordinated development between bus arrangement and power grid is a key to the design of UHV substations. This paper comprehensively analyzed the interplay between bus arrangement and power grid in terms of various network structures such as single-chain type, single-loop type and grid type; various locations of substations such as source end, receiving end and hub; and point-to-grid and point-to-point connection methods from UHV substations to the 500 kV power grid. Finally, design principles for UHV substations were proposed based on the analytical results, which is helpful to the selection of suitable bus arrangement systems for UHV substations.
With the foundation resistance coefficient method, it gives mechanics analysis for the new digged foundation with wing plates when loaded laterally, and offers corrected formulas by modifying the average stress on the wing plate. Then the average stress on the wing plate is not simply equal to midpoint stress, but the average value of three points, including the upper edge point, the middle point and the lower edge point on the wing plate. At last a project example is analyzed and discussed. The results show that, the new digged foundation can reduce the top horizontal displacement and bear a heavier lateral load; corrected formulas have wider applicability in power transmission projects, and can indicate the effect of the wing plates to the lateral deformation; the new digged foundation with wide-shallow wing plates can get better results than that with narrow-deep wing plates, and is recommended for power transmission projects.
In allusion to the frequent accidents occurred in the 110 kV Dangxiong-Naqu-Anduo transmission line in Tibet, reasons for line trip were researched. It was analyzed that changes of atmosphere density and atmosphere pressure can affect the safety and stability of over-head power transmission lines’operation. On the basis of maintaining safe operation at a reasonable project cost, the algorithms for the external insulation design of newly-constructed over-head transmission lines, and the air gap of transmission towers in high altitude areas were deduced, which can effectively solve problems in this regard.
The seabed-scour depth and the seabed elevation around the foundation of the offshore transmission tower are of great importance to the design of transmission towers and poles. Based on the Zhoushan long span power transmission project, this paper analyses natural scour according to measured submarine topography data, and researches on commonly scour and local scour around the foundation of the offshore transmission tower with a channel test under normal model. The study proves that the seabed condition is steady; the maximum amplitude of scour and silting for many years is 0.8 m, and the maximum local scour depth around the foundation of the offshore transmission tower is 7.5 m. On this basis, the total scour and the design elevation can be got, which provides reference for similar long span projects.
After the practice of several HVDC transmission projects, the HVDC technique of China has been improved rapidly. In this paper, the protections of AC filters used in Tian-Guang、Gui-Guang I、II and ±800kV Yun-Guang HVDC transmission system are introduced. With the comparison of the protection used in each HVDC system, the course of development and the localization of the AC filters protection used in HVDC systems of CSG have been discussed.
When a chimney reaches over 210 m in height, significant errors will occur if the even curvature method is used to calculate additional bending moments. A method is proposed for precise calculation of the additional bending moments of the chimney, which is based on the theory of conjugate beam, along with the chimney stiffness being reduced. By taking a chimney project as a case study, the method is used to calculate the additional bending moments and the lateral deflections under the lateral wind loads. In order to verify the calculation results by this method, the ANSYS software is used to make a comparison, which has proved the reliability of this method.
In order to evaluate characteristics of VFTO and its harm to the main electrical equipment, we have done a great quantity of emulational calculations integrating with a certain 750kV GIS Substation in Northwest Power Grid of China. In the process, preliminarily, we have mastered the distribution of VFTO on main parts inside and outside of GIS and made a conclusion that the VFTO amplitude limit is in withstand capability of the relative equipment of this substation. We performed measurement on site based on the calculations, mastered important characteristic parameters, such as actual amplitude, wave shape, frequency and so on of VFTO in 750kV GIS substation. The measured results on site have instructive significance for the switching operation of disconnector of 750kV GIS, meanwhile, it made us accumulate valuable experience and data for actual measurement of VFTO and switching operation of UHV 1 100kV GIS.
On ±660kV Ningdong-Shandong DC power transmission demonstration project general line, it uses JL/G3A-1000/45 large section ACSR and installs dampers to reduce aeolian vibration. According to the characteristics of the project and the conductor, the vibration frequency of 5Hz～45Hz shall be prevented with the damper for JL/G3A-1000/45. The author designed reasonable damper head through massive calculations and selected stranded galvanized steel wires that are suitable to the head, in order to make the measured resonance frequency dovetail into the theoretical calculated value basically. Frequency 1 of FDY-8 type damper is about 8.5Hz, while frequency 2 is 36Hz, and when the energy consumption is high, it may realize large protection span for JL/G3A-1000/45.
It is worthy to study the effective cost control since the State Grid Corporation has vigorously implemented the engineering volume management. Based on the previous concept of constructing budget drawings, the concept of constructing drawings management budget has been proposed in this paper. By deep analyzing the construction drawings budget of amount difference, the real-time monitoring of the amount of construction, materials and costs in the construction had been enhanced in order to improve the management level in engineering. The case study shows that the application effect of the construction drawings management budget is significantly, and it is strongly operational and applicable, which can provide a decision-making support for the power transmission project management.
Based on the investment optimal theory and process analysis, the management method and its application in investment optimization for grid projects are studied. With comprehensive considerations of economy, reliability, sociality, the optimal model of grid project portfolio is constructed which transforms the capital constraints into a penalty function and takes achieving the maximum profits as its target. The model and genetic algorithm are proved practical and correct through calculation examples.
The terrain condition for the 330 kV power transmission project of Jishixia hydropower station is complex and the construction environment is bad. It is analyzed that this project has suffered from a series of problems such as conductor upward, big enveloping angle of conductors, and over load of the connecting pipe under pressure or its protecting steel armor when passing the pulley. On this basis, this paper proposed relevant solutions and schemes. The implemented construction proved the feasibility of the proposed scheme, which can provide reference for tension stringing projects in mountainous areas.
