In order to improve the calculation accuracy of theoretical line loss for distribution system, a novel calculation method based on hybrid learning algorithm(HLA), which is composed by generalized regression neural network(GRNN) and particle swarm optimization(PSO), is proposed. The theoretical line loss calculation is abstracted into the multi regression problem (MRP), of which the input and output vector are selected as various impact factors and theoretical line loss values. The sample set is constructed for HLA training. In GRNN training process, the method can overcome the difficulty for selecting optimal training parameters by PSO. The experiments show that, the HLA method has better performance compared with the traditional one.
The change of voltage and reactive power in stable system caused by tap changing of different on-load tap changers (OLTC) has the nature of nearly linear superposition. Based on this, the strategy of changing the tap of OLTC is proposed in this paper, for satisfying the requirements of reactive power control. The step changes of voltage and reactive of all network nodes in power system caused by tap change of OLTC are calculated in initial power flow, which is defined as voltage effect per tap(VPT) and reactive effect per tap(QPT). The optimal strategy is obtained, by minimizing both taps changes(steps) and reactive power changes as the objective function, restraining the voltage of whole network buses to the control range, and optimizing the combination of transformer taps. The actual calculating example shows that the method is simple and practical.
By analyzing the basic requirements for selecting voltage sequence, every possible configuration of voltage sequence is presented. Combined with development status of China’s power grid, the emphasis on optimization and selection of voltage sequence is discussed. On this basis, evaluation indexes of voltage sequence are proposed from technical, economic, social and other aspects. The evaluation index system is further established to guide selection of voltage sequence.
When p-y curve is applied to mechanical analysis of group piles, the pile-top displacement is not sum of displacements induced by force and moment. Therefore, the finite difference method is firstly employed to get modulus of foundation support of each point. The stiffness coefficient of each pile-head is then determined by the transfer matrix. Finally, the iterative circulation calculation is processed by p-y curve method based on the above two steps. It is shown that the results obtained by the method mentioned in this paper agree with those by finite difference method. In addition, by comparing with the method mentioned, the displacement and the internal force obtained by the “m” method is not safe.
In present calculation of electric distance for overhead transmission line, the accuracy is low and the calculation efficiency cannot meet the design requirement. Therefore, three-dimensional calibration system of electric distance for overhead transmission line is developed based on catenary calculation method, space coordinate transform and OpenGL library. In the system, the three-dimensional electric distance calibration is implemented between phases on the same and different circuit in transmission lines with single-, double-and multi-circuit on the same tower. In addition, three-dimensional models and dynamic interactive of tower, insulator and catenary are displayed. The swing angle of insulator and tension of catenary can be automatically calculated under different design conditions. The system is very practical in improving the efficiency and reducing labor intensity of designer, and provides technical references for path selection, layout and locating calibration of towers in transmission lines.
The cage type jumper and tubular jumper are widely used in tension towers of ±800 kV UHV DC transmission line, for restraining the partial string wire and reducing jumper swinging. However, the jumpers have complex structures, and are expensive and difficult for transportation and installation. By wind deflection calculation, tower design and comprehensive technical and economic comparison, the advantages & disadvantages and applicable conditions of jumper types are discussed, including single/double string, I/V string, soft/hard jumper etc. The results provide references for further design of ±800 kV DC tension towers.
The finite element method(FEM) and analytical method used for the form-finding of overhead transmission line is introduced in this paper. The ANSYS software is used to research on the form-finding of a transmission line, and the program is written by APDL language. The relevant parameters are compared with the theoretical values, verifiying the accuracy of FEM used for the form-finding. The results provide conditions for the dynamic analysis of overhead transmission line.
In Chuxiong and Suidong converter station of ±800 kV UHVDC transmission lines from Yunnan to Guangdong, electromagnetic disturbance occurs. The principles of fundamental electromagnetic disturbance are analyzed. According to station layouts, the electromagnetic disturbances are investigated quantitatively, the shielding requirements for valve halls and control buildings are proposed, and the corresponding shielding measurements are presented.
The ultimate bearing capacity of transmission towers with steel tube and angle steel combined is analyzed by the finite element software of ANSYS in the conditions of ground motion. The ultimate bearing capacity calculated by displacement loading method shows that one support of transmission tower sinks deeply. In order to improve torsion resistance of the tower, both the steel bars near the supports and transverse bars near the changing slope should be strengthened, and some foundation treatment schemes are proposed in this paper.
According to the requirement and features of fieldbus electric control system (FECS) in power station, an ARM based Profibus-DP V1 slave station is investigated with CSC-831 function of low voltage measurement and control. The typical sub-system of FECS is built and the communication capacity is tested by networking test. The acceptable communication speed for FECS and some applicable problems are discussed as well. Both the main station and the salve station which are designed independently have the lower price and better EMC performance than other special profibus devices.
PM2.5 particle in atmosphere, which is harmful to the people’s health, has been drawing more and more attention. The emission amount of PM2.5 from thermal power plants covers about 10% of total output by human activities. Bag filter has high capture efficiency for PM2.5, and electrostatic precipitator(ESP) could increase its collecting efficiency for PM2.5 by selecting proper power facilities and specific collecting area. It is shown by laboratory tests that the capture efficiency for two types of dust collector could be up to 90%. Besides of using high-efficient dust collector, measurements such as decreasing emission of NOx and SO2 are effective and necessary to reduce PM2.5 output from power plant.
The all volatile treatment (oxidation)(AVT(O)) instead of all volatile treatment(reduction) (AVT(R)) has been applied to 600 MW once-through supercritical units with high deposition rate, where the iron content decreases at the economizer inlet, no obvious increase of pressure drops is found at the feedwater pumps and control stage of turbines, and the safe operation of the units is improved. The selection and characteristics of the feed water treatments are analyzed. In addition, the control conditions and iron content determination methods are discussed based on AVT(O) method. It is concluded that AVT(O) can be applied instead of AVT(R) for supercritical once-through units with high deposition rate when oxygenated treatment(OT) is not qualified.
After ultra supercritical(USC) boiler unit is put into commercial operation, some problems often occur including welded joint fracture, heating surface explosion, oxide coating tube-blockage and so on. By comparing the heat load and corresponding materials of various boilers, the early failure and oxide coating exfoliation are analyzed of new type of heat-resistant steels such as T23, T/P92, SUP304H, HR3C, etc. In addition, the countermeasures are proposed, providing references for improving the safety and reliability in manufacture, installation and operation of the USC boilers.
In combination with the requirement of seismic design, the structure selection of side bunker is discussed in the 8 degree seismic intensity region with site Ⅲ. By comprehensively analyzing the performances of steel structure, it is found that steel reinforced concrete is conformable to the side bunker in a high-intensity seismic area. In the steel reinforced concrete structure, the high compressive strength and high durability of the concrete are well employed, and the shape steel is set to improve the seismic behavior of structure, avoiding the brittleness breakage of high strength concrete structure.
At present, a large amount of regulations and technical requirements of ASME standards are applied in the domestic supercritical boiler manufacturing technology. However, some flexible provisions in ASME standards are adopted for installing safety valve to the boiler without fixed soda division, which conflicts with the GB and industry regulations of safety valve. In view of engineering application problems of safety valve in supercritical boiler superheater, the set pressure, blowdown of a safety valve, field test, capacity allocation, position setting of safety valve are analyzed by comparing the national standards, industrial standards and ASME standards. It is shown that the regulations of safety valves in GB and industrial standards are unable to meet the need of practical engineering, and should be improved for effectively guiding the engineering application.
基于多个SCAL型间接空冷系统的工程设计，分析了初始温差（initial temperature difference，ITD）、迎面风速、散热器高度、塔形尺寸等设计参数对空冷系统规模的影响。进行了SCAL型间接空冷系统设计规模的优化计算，包括ITD值的优化、散热器高度的优化、迎面风速的优化计算，讨论了其他设计参数的选取，提出空冷电厂年运行费用的计算方法，给出指导SCAL型间接空冷系统设计参数优化的原则。
The steam blowing system of thermal power plants is controlled by DCS(distributed control system), of which the control logic is constructed by traditional sequence control module of DCS. However, the traditional control mode has many disadvantages. Therefore, a new serialization code sequence control(SCSC) mode is introduced, which is clear in structure, simple in maintenance and convenient in use. By the application in a 1 000 MW ultra supercritical unit, it is proved that the SCSC mode is suitable for many control objects, and can be used in many fields.
The material and structure of aluminum conductor with carbon fiber composite core(ACCC) are different from those of common aluminum cable steel reinforced(ACSR). ACCC has obvious advantages in stress, sag characters, transmission capacity, and energy loss etc. Some typical data are extracted from more than 10,000 data for sag calculation of conductor stress under various design conditions, for analyzing the application of ACCC in new transmission lines and capacity expansion transformation. As a result, the applicability and economy of ACCC is illustrated.
The structural load for transmission lines continually increases and application of large angle steels in UHV tower will become inevitable. The paper analyses the feasibility technically and economically for large angle steels replacing normal ones. In addition, the effects of purchase price variances between large angle steels and normal ones on the economy of transmission lines are discussed. Combined with the construction scale of power grid during the 12th Five-Year-Plan period, the factors affecting the large angle steel application, the applicable amount and economic-social benefits are demonstrated in the next five years.
The demonstration project of UHV AC transmission, with high voltage level and relatively complicated equipments, has been put into commercial operation, where the online monitoring systems are applied to the preliminary main equipments in order to understand the operation state of equipments and avoid the failure of preliminary equipments. The construction of the system is introduced, and the operation experiences are summarized based on the practical application.
Frequent breakdown occurs for control contactor in 500 kV disconnecter, due to the transient arc surge appearing in the coil circuit at the moment of excitation return, by analyzing the voltage and current waveforms during the operation of control contactor. Therefore, the anti-accident measures are proposed by applying the arc suppression circuit to the control contactor coil. By comparing the effect of two kinds of arc suppression circuit, an arc suppression circuit with the diode and series resistance is selected.
In this paper, a relay protection and fault information management system for power plant is designed. Aiming at the features of relay protection in power plant, the data of relay protection are collected in real time, classified and diagnosed rapidly and accurately, providing effective means for safe and economic operation of power plant. The system not only promotes the intelligent level of relay protection system, but also improves the safety and reliability of power plant, of which the effectiveness is proved by practical application.
The installation and operation of continuous emission monitoring system(CEMS) for flue gas provide effective means for understanding concentration and amount of pollutant discharged, and are good for safety operation and management in thermal power plant. According to the calibration of 107 sets of CEMS for flue gas in thermal power plants of Henan Province, the qualified rate of accuracy for each calibration project and common problems existed in the operation of CEMS are analyzed and summarized, and the corresponding suggestions are proposed.
Modular construction is widely used in third generation nuclear power plants, which shortens the construction period but increases difficulty of construction. In order to make structural module lift safely and accurately, the maximum deformation and stress for lifting modules are determined by finite element analysis. In addition, the components are evaluated standardly, showing that the modules could satisfy the lifting requirement. Results of finite element analysis provide a strong theoretical support for structural module lifting.
In the assembly of steam turboset, the vibration control of turbine shaft is the key problem of installation. In this paper, the vibration control strategy of turbine is proposed by outgoing quality control, base grouting control, contact control between bearing and its pillow, gap control between the dynamic and static parts of turbine, rotor alignment control, field quality control of rotating parts, flutter variation control before and after coupling connection, isolation control of turbine island site with architecture around, and etc. As a result, the turboset is successfully started at one time and the bearing vibration is on good level.
