Taking eight-span 500 kV transmission lines as research object, this paper constructed the finite element model for eight-span conductors in strain section, with considering influence factors, such as the relative height difference of supporter, the length of insulator string, geometric nonlinear effect, wind-induced aerodynamic damping, etc. The harmonic wave superstition method was used to simulate the turbulent wind velocity along the conductor and study the response of conductor swinging in multi-span lines, with considering spatial correlation. Through the analysis on the power spectrum of wind-induced oscillation at insulator suspension point, this paper discussed the impact of turbulent wind velocity on the wind-induced dynamic amplification effect from aspects of background component and resonant component, and compared the conductor swinging calculation results between the multi-span finite element model and the static single pendulum model. The results show that the static rotation angle calculated by the static single pendulum model is larger than that calculated by the continuous multi-span model； when taking aerodynamic damping effect into consideration, the background component is the main body in wind dynamic response, and the resonance component can be ignored； the dynamic magnification factor is about 1.1~1.3.
Aiming at the problem of high harmonic content of three-phase magnetically controlled reactor （MCR）, a novel three-phase MCR with separating two-stage magnetic valve structure was proposed, which was composed of two-stage iron cores with different area and length. In the dynamic process of adjustment, due to different magnetic saturation of the two-stage magnetic valve, it could produce different phase harmonic current, which could be mutual compensated, so the output harmonic current of MCR could be reduced. Taking the suppression of the 5 and 7 harmonics of three-phase MCR as study target, a mathematical model of the harmonic characteristics was established, which used two section areas and lengths as main parameters, and the parameters were designed and optimized. The results show that: the 5 and 7 harmonics peak in new three-phase MCR can do not exceed the rated output current of 0.77% and 0.6% in theory. Finally, the simulation model was established, and the simulation waveform was the same as the theoretical waveform, which could verify the effectiveness of harmonic suppression.
With the rapid and sequential implementation of the 13th Five Year Plan, the current 500 kV power grid framework of MengdongNortheast cant meet the output requirement of Hulunbeir sendingend system. In order to study the harmonious optimization between safety and economical efficiency of new frameworks, this paper used PSASP simulation software to analyze the power flow and the transient stability test of N－1 for two architecture planning schemes based on prediction data of winter heavy load in 2015 in Northeast power grid, as well as presented the corresponding security and stability control strategies. The scheme took into consideration the influence with or without series compensation and the situations where related lines were put into operation or not. At the same time, quantitative indexes were proposed on the basis of risk viewpoint, and the economic risk of new frameworks was evaluated accordingly. Then the optimal scheme was determined based on comprehensive factors above. The simulation results verify the feasibility and effectiveness of the scheme, which can provide a reference for related management and dispatching departments.
This paper established a risk assessment model for power system in storm climate, to make up the weakness of traditional risk assessment that the model ignored the climate impact of wind and rain so that assessment results were too optimistic. The optimal AC power flow model was used to calculate the system load shedding, obtain the minimum load shedding and assess the low voltage risk of system, which could effectively improve the problem in traditional DC power flow model that the low voltage risk of nodes could not be directly assessed. The system load shedding was obtained with using optimal power flow, which could effectively improve the problem that the power flow calculation did not converge so that the load shedding could not be obtained or the calculation of the load shedding was inaccurate. Finally, this method was used to calculate the modified IEEE-RT79 system. The results show that the proposed method is effective and feasible. Meanwhile, the overload risk and low voltage risk of modified system were assessed, whose results could provide a reference basis for the planning and operation of power grid in storm climate.
A durable life prediction model was constructed for transmission line foundation under Cl- diffusion erosion, based on the Ficks Second Law. Then the durable life limit-state equation of foundation was established with using probabilistic method, physical random variables were transformed to independent standard normal variables with using the Nataf model, and the target reliability calculation of durable life with Breitungs formulations was achieved, based on Second Order Reliability Method （SORM）. Finally, taking ±800 kV UHV DC transmission lines from south of Hami to Zhengzhou as background, this paper studied the influence of statistical parameters on the durability failure probability distribution of foundation, such as protective layer thickness, water-binder ratio, critical Cl- concentration, curing time, annual average temperature and so on. The results show that the reliability index of foundations durable life calculated by probabilistic method can satisfy the minimum reliability index requirement of 1.5, which can provide a basis for the design of durability and the durable life prediction in transmission lines foundation engineering.
Taking the conductor selection of ±800 kV UHV DC transmission line as research object, the 6-bundle conductor was determined according to the electrical performance comparison of conductors, and five types of conductors cross section were chosen from 720 mm2 to 1 520 mm2. Single factor and multi-factor sensitivity analysis were carried out on the selected conductor scheme from aspects of loss time, electric price, rated current and discounted present rate. The results show that the power loss cost increases with the increase of loss time, electric price, rated current and discounted present rate. Meanwhile, the economic of each conductor scheme was analyzed with using investment increment equilibrium analysis method, and the cross section scheme of the conductor used in typical engineering conditions was obtained. And then, 1 250 mm2 conductors of round wires and profile wires were compared. The results show that the comprehensive economic characteristic of profile wires is worse than that of round wires； the initial investment of aluminium conductor aluminium alloy reinforced is less and its comprehensive economic characteristic is better； the initial investment of medium strength aluminium alloy conductor is higher； and its comprehensive economic characteristic is better when loss time and electric price keep high level.
According to the status of single micro control unit （MCU） of vacuum circuit breaker controller with permanent magnetic actuator： many processing tasks, slow running speed, higher failure rate and so on, this paper designed a new type of smart controller for 10 kV vacuum circuit breaker with permanent magnetic actuator. The controller was divided into three modules： power, protection and communication, and each had MCU respectively to achieve corresponding functions. In terms of hardware, the protection unit used STM32f407 MCU as microprocessor, which could achieve the functions of signal acquisition, processing, protection and so on； two STM32f103 MCUs were used as the core hardware of power management, communications and human-computer interaction. In terms of software, μC/OS-II real-time operating system （RTOS） and TCP/IP protocol were ported to the system, which could have a high degree of stability and real-time. The test results show that the reliability, computing speed and accuracy of the new controller have been greatly improved, and at the same time, the fault rate is reduced.
If the power flow of transmission section exceeds the control limits, it will restrict the transmission capacity of power grid, using liaison channel to transfer power load between substations is a common way to solve this problem in actual power system. This paper introduced the relevance characteristics of loads between substations base on field operating experience, systematically discussed the basic principles that the load transfer method was used to improve grid transmission capacity, deduced the sensitivity coefficients calculation formula of load transfer between substations in a simplify form and proposed the control strategy of load transfer method with heuristic searching algorithms. The actual examples show that the proposed load transfer method has advantages of fast calculation, simple and practical operation, etc., and can effectively solve the over-limit problem during power flow control process, which can enhances the transmission capacity of power grid.
Two-out-of-three （2 of 3） logic is widely used in DC protection system of converter stations, because of its lower malfunction and rejection rate. There are different methods to implement two-out-of-three logic, according to different devices. Taking the DC system protection of Zhongzhou converter station and the non-electrical protection of converter transformer as research objects, this paper comprehensively analyzed the two-out-of-three logic of DC protection in Zhongzhou converter station, including analog value acquisition circuit, digital value acquisition circuit and trip circuit, combined with the realization way of two-out-of-three logic of DC protection in previous projects. Finally, the problems were found, and some improvement suggestions were proposed, which could provide some basis for the design of follow-up projects.
Special field test has very important sense to enhance the grid detection level of power equipment and the quality, efficiency of UHVDC transmission project. Combined with ±800 kV Yunguang and Puqiao DC transmission project, this paper compared and analysed the characteristics and application range of series resonance and parallel resonance. Combined with the long-duration induced AC voltage （ACLD） test and AC applied test of converter transformer, the application method and key technology of resonance test apparatus in UHVDC transmission project construction had been studied, which had reference and guiding significance for the special field tests of subsequent UHVDC transmission project.
The mathematical model of transmission lines is widely used in the analysis and calculation of power system； and the accuracy of its parameters is closely related to the safe and stable operation of power grid. The development of wide area measurement system （WAMS） supplies a new way to obtain the parameters of transmission lines. According to the status that there were few studies on the influence of measurement error on the results of parameter identification algorithm, this paper proposed a parameter identification algorithm for transmission lines based on robust least mean squares. The algorithm was introduced the robust criterion function instead of mean square error in traditional minimum mean square estimation algorithm, and adjusted the threshold value through adaptive thresholding method, which could make it have strong adaptability of noise resistance. Meanwhile, kernel density estimation method and point estimation method were used to extract the statistical feature of calculation results at different time. Finally, the comparison between simulation analysis and measured data verifies the effectiveness of proposed algorithm.
As the high voltage is obtained by the way of frequency-regulating resonance method in EUV electrical equipment AC voltage withstand test, the corona loss is the main loss in this circuit, which can be reduced significantly by using extended diameter aluminum foil conductor. The extended diameter aluminum foil conductor has the defects of big wind deviation angle and excessive vibration when applied in the bad weather. Therefore, a new windproof and corona prevented conductor was proposed for the AC voltage withstand test of EHV electrical equipment, whose mechanical and electrical properties were also studied. Finally, field test results prove that the new conductor has better characteristics in windbreak weather and reducing corona.
To achieve optimal adjustment for various operating conditions of the co-combustion process of waste and cotton stalks, an accurate model of the co-combustion is needed. But if all the factors are equally used as model inputs, the complexity and computation run time of the model will be increased, so the accuracy will be impacted. To solve this problem, combined with examples, through data preprocessing and gray correlation analysis the weight coefficient of each factor was determined, and a least square support vector machine model was established for the waste and cotton stalks co-combustion process. The results show that this model has better fitting result and generalization ability compared with the simple least square support vector machine model, which can effectively improve the accuracy and stability of the co-combustion process model of waste and cotton stalks.
The feasibility study of a 2×1 200 MW ultra-supercritical unit in a power plant in coastal area was completed to further promote the development of 1 200 MW units, from the aspects of the main equipment capacity, main equipment parameters, specifications for main equipment, main system configuration and thermal economy, and so on. The results show that, 1 200 MW ultra-supercritical unit is feasible and reliable, which can be applied in our country. Compared with 1 000 MW units, 1 200 MW ultra-supercritical unit has a lesser unit occupation area, a larger annual power supply, and a better economic profit. The 1 200 MW ultra-supercritical unit has a 46.20% thermal efficiency, a 266.25 g/（kW·h） gross coal consumption rate and a 277.34 g/（kW·h） net coal consumption rate, and is advanced in China. The 1 200 MW ultra-supercritical unit is the latest trends of bigger capacity units.
Security investment prediction for power supply enterprises is always complex and difficult, for and the traditional methods are not able to meet the characteristics of safety investment for power supply enterprises. Based on the analysis on the characteristics of safety investment, the grey multivariate MGM （1, m） model was introduced into the security investment prediction for power supply enterprises, and three interrelated factors were selected to predict the safety investment for power supply enterprise: the safety investment, the annual earnings and the annual profit. Finally, the model was verified through the instance. The results show that the model based on the grey multivariate MGM （1, m） is effective in the prediction of safety investment for power supply enterprises. The research plays a guiding role in the safety investment decision for power supply enterprises
Power industry has been required to develop in a low-carbon way to meet the challenge of global climate change and energy crisis. Based on the research status of low-carbon power grid, the low-carbon development level of Shandong power grid was comprehensively analyzed. The transmission loss and utilization condition of Shandong power grid were analyzed from the perspective of different areas and different power transmission and transformation equipment. And then the historical development trajectory of the low-carbon benefits of Shandong power grid was evaluated. Moreover, the non-fossil energy consumption ratio of Shandong power grid to our country was calculated, as well as the contribution ratio of carbon emission reduction intensity for each unit of GDP of Shandong power grid.
