The external flow field around transmission line under icing conditions was studied with using fluid numerical simulation software FLUENT based on finite volume method. The distribution characteristics of velocity field, temperature field and pressure field of the airflow around transmission line were analyzed. Then, the effects of wind speed, environment temperature, wire surface temperature, and wire radius on velocity field, temperature field and pressure field were researched. In fact, the windward of the transmission line is easy to freeze and the leeward of the transmission line is hard to freeze. The comprehensive analysis of the distribution characteristics of velocity field, temperature field and pressure field reveals the reason and mechanism of uneven distributed icing on the transmission line. And the analysis of the relevant parameters in icing shows why the wire with smaller radius is more easily covered in ice.
To set the reliability level of transmission line crossing high speed railway, the statistical parameters of the load and resistance of tower members in transmission line were analyzed and calculated. The reliability of tower members designed based on the current code were calibrated. It is indicated that the reliability indexes for strength of axially loaded members or the stability of axial compression members are 3.10 and 2.99, respectively, in the combination of permanent load and wind load； and are 3.35 and 3.20 respectively, in the combination of permanent load, wind load and ice load. The reliability of tower member in transmission lines in China is somewhat lower than that of building steel structures, in the combination of permanent load and wind load； but it is close to the reliability of tower members in US, and higher than that in Canada, in the combination of permanent load and wind load, or in the combination of permanent load, wind load and ice load.
To set the reliability level of transmission line crossing high speed railway, the statistical parameters of the load and resistance of insulators, fittings and ground wires were analyzed and determined. And the reliabilities of these members designed based on the current code were calibrate by using FOSM （first order second moment） method with considering the probability distribution type of basic variables. It is indicated that the reliability index of insulator string depends on the parallel number of strings and the number of insulator in one string. The reliability indexes of single and double insulator string with 50 insulators in one string are 3.45 and 3.55 respectively. The average reliability index of fittings is 3.55. The reliability index of ground wire at the sag’s lowest point or suspension point are 4.90 and 4.45respectively, in the combination of permanent load and wind load； and 4.45 and 4.15 respectively, in the combination of permanent load, wind load and ice load. The reliability indexes of insulators, fittings and ground wires are larger than that of transmission tower.
To check whether the reliability of tower structures designed based on the current design code of transmission lines could satisfy the reliability requirement of tower members in the transmission line crossing high speed railway, the reliability analysis was carried out for 500 kV typical angle steel tower and 220 kV typical steel tube tower. It is indicated that the reliability index of steel tube tower is lager than that of angle steel tower for the case studied in the paper. The reliability index of tower member may not meet the requirement of 3.7 for the transmission line crossing high speed railway, although it is larger than the minimum reliability index required in current design code. The reliability of tower members can be upgraded by increasing the importance factor of tower components, reducing the span of tangent tower or the angle of angle tower.
The transmission tower-line system is an important lifeline project as high voltage electric powers carrier. A four-step recursive calculation method of subsystem was proposed for the analysis on the system reliability of the transmission line crossing high speed railway, on ground of the safety requirements of high speed railway on transmission line. And then the system reliability of two crossing tension sections of transmission line, with angle steel tower structure or steel tube tower structure respectively, was analyzed. It is indicated that the proposed four-step recursive calculation method is effective. The system reliability of transmission line with steel tube tower structure, which is dominated by the reliability of tower members, is more than that with angle steel tower structure. The system reliability of a tension section in transmission line can be upgraded by increasing the importance factor of tower components, reducing the span of tangent tower or the angle of angle tower.
In order to enhance the shielding factor and reduce the PC volume of partial discharge （PD） in the PD test of power cable, this paper proposed the control system to improve the high voltage side filter performance of power frequency series resonance equipment, which could effectively improve the stability of the test, and remove the spectrum burr of PD. The integrated parallel reactive power compensation system, which was design by conductance algorithm based on Fryze-Buchholz-Dpenbrock method （FBD）, could enhance the following features of voltage and current, and achieve a good harmonic filter effect. Meanwhile, the parameters of capacitance and inductance in whole system were optimized, and the capacity of three-phase VSC converter was effectively tuned, which could not only make the control system achieve optimal compensation performance, but also make the capacity tuning of the converter be in the minimum state. The experimental simulation and the field PD test of power cable prove that the control system can significantly enhance the stability and adaptive ability of the power cables PD test.
The capacity of power grid can be enlarged by means of increasing pole transformers, which will greatly increase the improvement cost of the line in power network. With regards to this reason, the voltage regulation tests for low-voltage power line were carried out in the laboratory by means of the battery energy storage system consisting of electric vehicle battery in charge and replacement station provided by State Grid Corporation and self-made power conversion system （PCS）. The results show that the available battery capacity decreases with the increase of discharge power. The operating voltage of one battery box is in the range of 69-80 V at the discharge power of about 3 kW, therefore, five battery boxes in series can meet the needs of voltage range of 324-438 V on PCS DC side. The voltage of power line can be effectively improved when the battery energy storage system affords power supply during low-voltage hours. Compared with the method of increasing pole transformers, the voltage regulation equipment containing battery energy storage has advantages of simple installation, small space requirement, small investment, flexible mobility and reusable.
This paper described the battery swap station system for electric vehicle and the current status of key equipment management, and analyzed the architecture and functional requirements of monitoring system in the battery swap station system for electric vehicle. Based on IEC 61850, the modeling scheme was proposed for the battery swap station system of electric vehicle, and the information model of key equipments was established. With using abstract data modeling method, the information configuration model was built for the intelligent electronic device （IED） in battery swap station. The proposed modeling method of key equipments in battery swap station can solve the communication model standardization issues of the key equipments, which can promote the normalization and standardization of information exchange between battery swap device and system, and provide a unified information model support for the system integration of battery swap station.
Firstly, according to the project feasibility study report, the basic requirements of conductor selection were presented for power system and four conductors were initially selected for comparison. Secondly, the basic performance advantages and disadvantages of conductors were compared and analyzed in current-carrying capacity, sag, ice overload, line loss and etc. Then, a detailed analysis was carried out on the reliability of construction and operation, electromagnetic environment and so on. Finally, the life cycle costs and environmental benefits of conductors were compared, and the advantages and disadvantages of energy-saving soft aluminium conductors in reliability, social benefits, environmental benefits and other aspects were fully demonstrated.
Li-ion battery has been widely used in high-voltage large-capacity energy storage because of its good performance. However, the capacity of single Li-ion battery is too large to produce high temperature during the charging and discharging process, which may induce unsafe factors, so the Li-ion battery management system must be designed to maintain the safety operation of battery and prolong its cycle life. According to the characteristics of Li-ion battery in energy storage system, this paper proposed a new hierarchical management strategy of Li-ion battery for energy storage system, discussed the structure and function of each layer, and emphatically introduced the main function of Li-ion battery management system, especially the data acquisition function of single cell, the state estimation function and the equilibrium management function. Moreover, their experiment strategies had verified by experiments. The experimental results show that the management system can meet the need of the energy storage system, and realize the state estimation function with high precision and efficient state estimation function for Li-ion battery.
In order to establish stable power distribution network structure for combined system with seawater desalination device driven by wind power as an independent power supply, combined with the research and application status of wind power and seawater desalination united technologies, this paper analyzed the wind power characteristics and the load characteristic of seawater desalination process units, and proposed distribution scheme for the united technologies with off-grid wind power and seawater desalination. Then, the independent small micro-grid system was built including off-grid wind power generators, energy storage device and seawater desalination process system, which constituted a complete set of power distribution network structure for combined system. Meanwhile, as the boundary condition that ensured the stable operation of micro-grid system, the energy storage system was introduced to effectively solve the matching problem between off-grid wind power and seawater desalination load, which could open up new solutions and ideas for the local consumption of wind power and the industrial electricity of seawater desalination on isolated island.
A large area of overall dislocation, cover wear, holes plugging and inner core tube rupture occurred at bell-type air cap with large diameter used in circulating fluidized bed （CFB） boiler in a power plant, which caused poor resistance partitions and fluidization of air distribution plate, slag leakage, coking and other accidents, so that seriously affected the normal operation of the boiler. Site inspection results show that the improper installation and maintenance is the main cause of these problems. Combined with the operation situation of boiler, the retrofit scheme was designed for the air caps, and all the air caps were replaced by the new type ones. The running results after retrofit show that the new type air caps have the characteristics of novel structure, better resistance and easy maintenance.
Under the condition of strong wind, the combination of hot air recirculation and ‘intrusion’ phenomenon results in the reduction of heat transfer efficiency of air cooling condenser. In order to improve the impact of environmental wind on air cooling condenser, this paper proposed the scheme that installed the windbreak on the leeward side of air cooling island （in the dominant wind direction）. Taking a 600 MW direct air cooling unit as an example, the external flow field of air cooling island was numerically simulated with using CFD （computational fluid dynamics） software. The impact of windbreak on heat transfer efficiency of air cooling condenser with different wind speed in the dominant wind direction or the opposite direction was analyzed. The calculation results show that, in the dominant wind direction, the air flow of air cooling unit with windbreak significantly increases, and the heat transfer efficiency of air cooling condenser is improved； in the opposite direction, the installation of windbreak make the hot air recirculation occur on the leeward side of air cooling island and the heat transfer efficiency of air cooling condenser decrease, and the windbreak with certain height installed at horizontal baffle edges on leeward sid can improve the phenomenon of hot air recirculation.
Due to the influence of environmental wind on direct air-cooling unit with overground ventilation, the hot air recirculation and intrusion phenomenon occurred on the edge fan, which would cause the decrease of unit’s heat transfer efficiency and the increase of condenser pressure. Therefore, this paper proposed a cooling mode with single duct underground ventilation. The external flow field of air cooling island in a 600 MW unit was numerically simulated with using Fluent software. Then, the influence of environmental wind on fan ventilation, unit’s heat transfer efficiency and condenser pressure was analyzed under underground ventilation mode, and compared with that under overground ventilation mode. The experimental results show that the underground ventilation mode can greatly improve the heat exchanger efficiency of condenser, and make the condenser pressure maintain at low and stable state, which can ensure the safe and economic operation of units.
During the action on DEH （digital electro-hydraulic） control system of turbine using a fixed coefficient of quantity, the primary frequency regulation may overshoot or undershoot in the certain load segment, because of the influence of steam distribution characteristics, which seriously affects the qualified rate of primary frequency regulation. Inspired by the nozzle steam flow and work capacity of turbine, this paper presented a design method for primary frequency regulation based on alve point （valve points primary frequency regulation, VPPFR）, in which the action on DEH side was varied according to the correction function of valve point and main steam pressure. Through the practical application, it is showed that this method can obtain the satisfactory qualified rate of primary frequency regulation.
This paper first introduced the development background, technical principle and engineering application in China of the MGGH （media gas-gas heater） technology. Then, taking a 1 000 MW unit as an example, through the technical and economic comparison with the traditional RGGH （return gas-gas heater） technology, it is concluded that the MGGH technology can achieve zero leakage of flue gas, efficient desulfurization and surplus heat utilization, so as to improve units’ cycle thermal efficiency, reduce coal consumption for power generation and supply, improve the economic efficiency and environmental protection level of power plant as well. Therefore, the application of MGGH technology will be the future development direction of energy saving and consumption reduction of coal-fired power plant.
According to the characteristics of grid construction projects in regions without electricity: poor economic benefit, outstanding project benefits and social benefits, this paper selected 10 indicators from economic benefit, project benefit and social benefit, as well as determined each weight of index system with using entropy method. On this basis, the post-evaluation model of investment benefit was built for the grid construction projects in regions without electricity, with using the TOPSIS （technique for order preference by similarity to solution） improved by gray correlation degree. And then, this paper carried out empirical research on investment benefit according to the collected data. The result shows that the economic benefit of grid construction projects in regions without electricity is poor, but the project benefit and social benefit are higher than those of general grid construction projects. It is necessary to focus on the project benefit and social benefit during the investment benefit evaluation of grid construction projects in regions without electricity.
The operation economy of micro grid is the main obstacle of its commercial operation. An effective way to solve this problem is the evaluation and the cost reduction from the evaluation. Through the analysis on the operating cost of micro grid, this paper proposed the evaluation index of operation economy for the micro grids with different generating capacities, with considering the standby cost of grid, based on the economic operation of micro grid. On the basis of this evaluation index, the influence of energy storage capacity and price, electricity price and energy management strategy on the operation economy of micro grid was studied. Finally, the operation data from demonstration project was used to validate the effectiveness of evaluation method.
For direct air-cooling unit, the higher back pressure increases cold source loss and affects the thermal economy of unit. Make-up water through hot well had little affection on reducing cold source loss, so atomized make-up water was proposed for direct air-cooling unit, which changed make-up water method from entering hot well directly to entering hot well after it was atomized at the appropriate location within the exhaust pipe. This paper built the physical model and thermal economy model of atomized make-up water based on equivalent enthalpy drop method, and calculated the thermal economy of the two make-up water methods under different working conditions with taking NK600-24.2/566/566 as example. The result verifies the feasibility that atomized make-up water can improve the thermal economy of unit. Compared with hot well method, atomized make-up water can reduce cold source loss, improve thermal economy of unit and achieve the purpose of energy saving.
Aiming at the deficiencies in the post evaluation of the transformation of scientific and technological achievements in power grid enterprise, this paper established the post evaluation index system for the transformation of scientific and technological achievements. On this basis, according to the post evaluation characteristics of the transformation of scientific and technological achievements in power grid enterprise, this paper established the intuitionistic fuzzy analytic hierarchy process model with combining intuitionistic fuzzy sets and fuzzy analytic hierarchy process, which could provide support for the post evaluation of the transformation of scientific and technological achievements in power grid enterprise. Then, this paper discussed the degree of consistency of experts’ comment on transformation project by using ‘intuitionistic fuzzy distance’. Finally, combined with the survey data, the empirical analysis was carried out, the operating process of the evaluation model was elaborated, and the operability and usability of evaluation index and model were verified.
