By now Dalian VSC-HVDC Crossing-Sea Project has the highest voltage level and the largest power transmitting capacity in the world. In the design of VSC-HVDC power system, the main circuits scheme, control strategy, the technical parameters of main circuits and main equipment, insulation coordination scheme and equipment insulation level are proposed for its converter station. Thus the overall VSC-HVDC technical scheme has been formed, which could provide completed design method and ideas for the system design of similar projects, and has special significance for the progress and engineering application of VSC-HVDC technology in China. Moreover, the system design of VSC-HVDC power transmission project has attached significant importance for the development of VSC-HVDC technology, the research of VSC-HVDC equipment and the engineering construction in China.
In order to simply and accurately analyze the transient stability of synchronous generator (SG), combined the time domain simulation results, a hybrid evaluation method for critical clearing time (CCT) of SG is proposed according to the intersection of the two lines, which are the linear of fault clearing time and minimum kinetic energy after clearing fault when SG is stable or unstable, respectively. In the two cases of considering the SG models with damping and without damping, the CCT is calculated respectively by the hybrid evaluation method of transient stability, which is based on post-fault trajectories of the minimum kinetic energy, and the results are compared with the traditional post-fault trajectories method of minimum kinetic energy and the time domain simulation method. The comparison results show that the calculation accuracy of proposed hybrid method is better than the traditional post-fault trajectories method of minimum kinetic energy, and its calculation is simpler than the time domain simulation method.
In recent years, equipment and material prices of power grid projects have been varied a lot, especially for AC transformers that have large influence on substation project costs, which makes the cost control of grid projects more difficult. Based on the principle that input parameters are measurable, available and open, and since price is determined by value and changed with cost, the price constitution of transformers are studied to build a cost analysis model of AC transformer. Thus it will be realized that with giving some industrial public data of main raw material prices and basic financial data, the cost of AC transformer can be estimated quickly, which can provide scientific support for the bidding bull’s-eye prices and price forecasting in power grid enterprises, as well as improve the accuracy of equipment price estimation in substation project budget.
Taking column foundation with undisturbed soil on loess as a research object, the site full-size water immersion static load test was carried out at Gangu substation of 750 kV Lanzhou-Tianshui-Baoji power transmission line project. The load-displacement of top foundation with water immersion was measured under uplift load combined with horizontal load and compressive load combined with horizontal load on the basis. Through the analysis on Q－S curves of test foundation, the ultimate uplift, and compressive bearing capacity of foundation were obtained. On this basis, the economic comparison between column foundation and spread foundation under the same design condition was carried out to further discuss the safety and economy of this kind of foundation. The research results could provide a theoretical basis for the optimization design and safety construction of 750 kV Lanzhou-Tianshui-Baoji power transmission line.
With the increase of overseas design project, it is necessary for designers to comprehend and master the similarities and differences between domestic and foreign standards. The transmission line standard in China is compared with ASCE standard in U.S., JEC standard in Japan, EN standard in EU, and international standard IEC, the calculated values of relative parameters including height variation coefficient of wind pressure, shape coefficient of wind load, adjustment coefficient of wind load (wind vibration coefficient), et al are emphatically analyzed. The results show that domestic and foreign standards are different in some calculation methods, such as basic wind speed, height variation coefficient of wind pressure, shape coefficient of wind load, adjustment coefficient of wind load (wind vibration coefficient), and yawed wind load, which can provide references for the designers in power transmission projects.
In order to study the impact of heat-resistant conductor operating temperature on the safety distance of live working on power transmission line, the temperature distribution of the heat-resistant conductor was obtained at 180 ℃of the temperature of conductor，and the switching impulse discharge characteristics of 1.0~1.5 m air gap between simulated conductor and tower were gained when the temperature of conductor was between 160 ℃ and 240 ℃. And the influence of heat-resistant conductor operating temperature on the discharge characteristics of the simulated air gap between conductor and tower was analyzed by theoretical calculation, whose results had good consistency with the experimental results. The results show that, when the operating temperature of heat-resistant conductor is 240 ℃, the influence range of high temperature conductor on ambient air temperature is no more than 10 cm range, and the influence on the switching impulse discharge voltage of 1.0~1.5 m air gap is about 2 %. Therefore, the influence of heat-resistant conductor operating temperature on the safety distance can be ignored in the live working of power transmission line.
In the scheme comparison and optimization design of power transmission line, it is necessary to use the tower charges (weights) in different schemes. The conventional estimation method of tower weight is to calculate one kind of height based on tower weight existed in an actual construction design. While the towers’ weight at other heights and under other loads are estimated approximately with formulas, which makes bigger error and trouble work, so a simple, practical estimation model of tower weight is required. Taking the type and weight of tower in "±800 kV tower typical design" as the data samples, amathematical mode based on nonlinear multiple regression analysis was established, the sample data were calculated and analyzed with simulation software Matlab, thus the mathematical relationship between tower weight and tower height, loading condition were obtained. Compared with the data of typical design and actual Hazheng construction design, the error of tower weight estimated by the estimation mode is small, while its accuracy is high, which indicates that the estimation mode is practical, effective, and suitable for the scheme comparison and optimization design.
A calculation model of V-type guyed tower was established by nonlinear finite element software tower. In order to reduce the tower weight, optimization analysis was carried out from aspects of conductor hanging way, tower head type, cable setting scheme and main column section, as well as the tower’s technology and economy were compared with those of self-standing tower. The results showed that the optimal design of V-type guyed tower could achieve significant economic effect, and its optimization measures could provide references for V-type guyed tower design in relevant projects in the future.
Organic Rankine Cycle (ORC) is one of the important ways to generate electricity with geothermal resource, and the physical property of organic working fluid is the main factor that influences the efficiency of ORC power generation. According to the characteristics of geothermal water, 6 kinds of organic working fluids, such as R134a and R245fa were selected, and the waste heat power generation system with each selected fluids were calculated repectively. Through the comprehensive analysis of system’s thermal efficiency, irreversible loss, pressure level and environmental protection, R245fa is found suitable organic working fluid for ORC power generation system with low temperature geothermal water.
Based on the practical anti-freezing problems of indirect air-cooling system in several domestic power plants, the freezing phenomenon occurred in air-cooled radiator tube was analyzed from the aspects of equipment selection, control system and actual operation. Combined with the meteorological features in north China, northeast China and northwest China regions, some anti-freezing measures were proposed for the design and operation of SCAL indirect air-cooling system, which could provide technical supports for the application of SCAL indirect air-cooling system in north China, northeast China and northwest China regions.
Because there is a time lag among power grid construction, power sources construction, and load development, the existing power grid structure and regional power consumption load may not meet the demands of outward power transmission by some new large-scale power plants. In order to solve this problem, a parameters optimization scheme of power system stabilizer (PSS) was presented. Based on the comprehensive consideration of the grid demands and generator stability, the frequency characteristic of PSS has been improved through adding a lead-lag link in compensation section, founding out the oscillation mode which restricted the ability of power transmission, as well as particularly implementing phase compensation for unit’ s excitation system under this oscillation mode. The optimized PSS has better frequency characteristic and larger gain. Through time-domain simulation and field testing, it has been verified that the ultimate power during the station starting up process can be increased from 1 765 MW to 2 900 MW in the wet season in 2010 summer, based on the power system analysis software package (PSASP). The research results show that parameters optimization of grid-connected unit’s PSS can improve the dynamic stability level of system and enhance the capacity of power transmission .
3-demension flow field in inlet box of G47-3 No.8D fan were studied numerically by using CFD, which showed that there was a small and a pressure loss region formatted by strong eddy current and reflux. According to the distribution of flow field, reformation and simulation were carried out on the inlet box. The results show that the big eddy current in old model has changed into two eddy current which are small in strength and size, the small eddy current in the old model has disappeared, as well as the reflux has been suppressed to some extent.
This paper introduces the layout and structure characteristics of stop valves and control valves of No.1 steam turbine in Hongyanhe Nuclear Power Plant, as well as the valves’ commissioning process, including setting of valve position feedback, the adjustment and calibration of valve switching time, step response test. Finally, some important technical indexes were analyzed to give adjustment methods, which could provide references for similar projects’ commissioning.
Pile group foundations with elevated piles will be one of the most popular foundation types on soft clay for offshore wind turbines in the next few years in China. The calculation of complex load, the analysis on foundations’ mechanical behaviors and deformation mechanisms, as well as the determination of foundation bearing capacity under complex load are the key problems that should be solved urgently for the design of pile group foundations of offshore wind turbine. Aimed to the common deep soft clay in the offshore area in China, the most unfavorable typical load combination for pile group foundations of offshore wind turbine was analyzed. By using new hyperbolic p－y curve model of pile foundation in soft clay, t－z curve model and q－z curve model in API code, an internal force and deformation analytical model on elevated piles was established under three-direction complex load. Then, optimization analysis on the main parameters, i.e. embedment and diameter of pile, circle diameter of pile cap and inclination of pile, was investigated. The results show that the effect of pile length on internal force and deformation of pile group is not significant but it is benefit to increase the inclination of pile when the pile’ uplift resistance and compression capacity meet the requirements; though the influence of pile group’s circle diameter increase on pile deformation controlling is little, it can effectively reduce the pile axial force.
The stress inside and outside the traditional cross-section combined angle steel of power transmission lines are uneven, which results in the deviation between the actual carrying capacity and theoretical design value. The double-angle steel splicing is proposed to improve the mechanical behavior of cross-section combined angle steel. Stress analysis on two splicing forms of cross-section combined angle steel was carried out with finite element simulation, so as to compare two different forms’ the coordination of component displacement, stress evenness, and stress status of the maximum stress control section. The results show that the displacement compatibility and the bearing capacity in double-angle steel splicing form are better than those in the single-angle steel splicing form, especially for towers with different height legs, in which the maximum stress of the main material of two splicing forms on the control section is 4.7% and 13.7%, respectively.
In order to evaluate the anti-disaster capability of power transmission tower under strong earthquake, the direct dynamic method was used to analyze the load bearing capacity under earthquake for a typical power transmission tower of 500 kV double-circuit lines by taking real earthquake record as the seismic input. The results show that the load impact on tower with the basic fortification intensity under earthquake is generally smaller than that of non-seismic actions, which means tower has good anti-seismic capability. However, the seismic impact of rare strong earthquake exceeds the load bearing and deformation capacity of typical towers. So, it is suggested that the power transmission towers, such as those for large-crossings, which demand highly for anti-disaster capability, should impose higher anti-seismic requirements and consider anti-seismic design under strong earthquake. Meanwhile, the impact of vertical earthquake should be considered in the seismic checking calculation of tower with long cross-arm cantilever.
Combined angle steel connected with bolts is a common structure in power transmission line project, the calculation contents of which include: the overall stability of combination section around virtual axis, the connecting bolt shear, buckling and bending of component angle, strength of battens on star-battened angle member. However, the current code GB 50017—2003 (“Code for design of steel structures”) has not given the calculation formula, in which the battens distance is more suitable for welded or riveted combination section. The steel structure code in Europe also has not given the calculation formula of connecting bolt shear. Aimed to the decrease of bearing capacity caused by the sliding of ordinary bolt connection, and the small shear deformation of combined angle steel on the empty axis, the pads thickness caused by the increases of virtual axis’ gyration radius can be not considered. But for the star-battened combined angle steel around virtual axis with large shear deformation, the equivalent slenderness ratio should be corrected and amplified to calculate its overall stability, according to the combination principle of battened member with lattice type axis compression; the calculate formulas of connecting bolt’s shear and component angle’s bearing capacity are proposed, according to the flexural deformation.
Aimed to the vibration fault of air-cooling fan in 330 MW direct air-cooling units in Shanxi Youyu Power Plant, the vibration rule of fan, reducer and fan bridge is gained through a series of analyses and tests on fan. The vibration fault of air-cooling fan could be eliminated by some measures, such as the reinforcement of fan bridge, and changing the fan blade number from 5 to 6. These vibration fault treatments and test results could provide references for fan’s design and construction.
In order to ensure safely and smoothly coming down to safe load for 1 000 MW supercritical units when auxiliary equipment tripping occurs, it is important to carry out RUN BACK (RB) tests during debugging process. Taking 2×1 000 MW supercritical units in a power plant as examples, the RB control strategy is studied and optimized in this paper, such as coordination control, fuel control, air volume control and feed water control, according to the units characteristics and previous experience. The RB testing results show that the equipments act correctly, the parameters are controlled within a reasonable range, the function of RB control strategy is perfect, as well as the automatic control effect is good.
A new fault location method with using frequency domain analysis of transient signals was proposed based on traveling wave characteristic frequency. Mother wavelet function was constructed to improve the characteristic frequency extraction of wavelet function, which could increase the extraction accuracy of fault characteristic frequency. Finally, this method was used to simulate a simple topology by using the software PSCAD/EMTDC, which has verified the high accuracy of this method .
In order to discuss the impact of different wind turbine types on grid-side power quality, some power quality problems caused by different wind turbine types are studied, such as grid-side voltage deviation, voltage fluctuation and harmonic. Based on PSCAD/EMTDC, the grid-side power quality simulation models were built respectively for the fixed-speed wind turbine which could switch reactive power compensation device, as well as for the variable-speed wind turbine which could operate under constant power factor or given reactive power. The simulation analysis of grid-side voltage deviation, voltage fluctuations and harmonic characteristics shows that, the wind farm with fixed-speed wind turbine has more significant effect on grid-side voltage deviation and voltage fluctuation than that with variable-speed wind turbine, but could cause serious harmonic pollution. The research results can provide a theoretical basis for the power quality management strategy according to different kinds of wind farms in China and the power quality management for regional power grids.
It is crucial to choose the appropriate way in live-wire crossing construction. Closely centered on the issue of live-wire crossing method selection, three scale methods of 1-9, 10/10-18/2 and 9/9-9/1 in analytic hierarchy process (AHP) are compared, whose results showed that the scale method of 10/10-18/2 is better. Based on the improved AHP, the hierarchy model for live-wire crossing method was constructed. Finally, three live-wire crossing methods were comprehensive evaluated and calculated by taking a power transmission line construction as an example, which showed that the cableway crossing is the best.
Aimed to the long installation cycle of boiler equipments in power plant during the construction stage or the situation that boiler equipments could not be installed in time after being transported to the construction site, the long-term storage and protection schemes and storage environment for main boiler equipments are introduced and studied, in order to make sure that the boiler body and other equipments could be kept in good condition, so that discard and failure caused by corrosion or other damages could be avoided. The main protection technologies includes the anticorrosion scheme for boiler parts, the storehouse environment requirements, the boiler parts stacking requirements, the periodic inspection measures and so on.
