Applied Mechanics and Materials Vols. 494-495

Abstract: Transmission tower is a widely used higher order statically indeterminate spatial structure, as the pillar of power transmission, modern society are increasingly concerned about its safety and reliability. This paper establishes a large-scale three-dimensional space model of transmission tower by using the finite element method, calculate and analyse the first six vibration modes and frequencies of this transmission tower, study the characteristics of each order vibration mode. These research results provide some references of design for the large-scale transmission tower.

Abstract: This paper designs and discusses black-start scheme based on a gas-steam combined cycle power plant (CCPP) in Tianjin power grid of China. First, considering the structure characteristics and station service power connection mode of the gas-steam unit, the diesel generator is chosen as fast self-starting unit. Also two self-starting schemes of direct starting and variable frequency starting are designed. Second, the technical feasibility of two schemes is determined through first loading capability test and bus voltage level test. After investment estimation comparison, the scheme II is chosen as recommended scheme. The research process proposed in this paper has certain reference significance to power grid black-start.

Abstract: To help with the planning and design of distribution automation systems (DASs), the best amount of terminal units (TUs) mounted in a DAS is analyzed from the perspective of benefit/cost ratio first. From the perspective of reliability, the amount of various kinds of TUs in different situations is studied, that is only TUs with tele-control function, only TUs without tele-control function, a hybrid of TUs with tele-control function and TUs without tele-control function. Some circuit breakers with current protection mounted on some branches arc investigated at length. The following conclusions arc drawn that only one TU for each feeder is the best choice from the viewpoint of benefit/cost ratio, and that the demanded amount of various kinds of TUs depends on the reliability performance desired, the time of isolating the fault section by manual operation, the time of reparation, and the frequency of failure per-year. A DAS planning example with 220 feeders is given to illustrate the proposed methodology.

Abstract: An ultraviolet detecting system for electrical faults is designed and built to locate the fault precisely and classify its pattern level as few studies have been done on. Self-organizing feature extraction method devotes itself to fault state recognition approach in high-voltage discharge. The established system including the filter system, image collection system, image preprocessing system, feature extraction, and pattern recognition could identify and classify device faults and operation conditions accurately tested by simulation.

Abstract: According to the problem that traditional single objective network planning cant meet the demand of complex gird and key supply mission, using improved artificial fish swarm algorithm (AFSA) for multi-objective grid planning. The paper presents a method through selecting Pareto optimal compromise solution by calculating and comparing the degree of satisfaction of each planning scheme with the reference of scholar Paretos approach of striking a multi-objective optimal solution. This method can effectively balance weights between multiple targets and improve the reliability and economy of power grid. The experiment results show the good performance of the proposed method.

Abstract: In China,most of distribution system is neutral noneffectively grounded. And the single-phase fault often happens through cement pole. In this paper,firstly,the voltage of the fault phase and the current of cement pole are derived in 10kV neutral noneffectively grounded distribution systems when cement pole has single-phase ground fault.Secondly,the online fault location method is proposed based on voltage gradient of cement pole.Thirdly,the resistence characristic of cement pole is analyzed and the distance obtained from the gradient voltage of cement pole is given.Finally, the theoretical analysis and simulation experiments show that the method is feasible.

Abstract: With the coming of big data age, Internet, finance and other industries have launched in-depth studies on big data technology. They hope to grasp the opportunities that big data brings to enterprises. Smart gird construction generated massive and heterogeneous data in the process of electricity generation, electricity transmission and electricity consumption, thus electricity big data took shape. Based on the analysis of Big Data characteristics of Smart gird user-side, this paper describes the risks that big data reduces on smart gird user-side from the perspectives of demand forecasting, customer complaint and operation risk that grid peak valley load brings. Meanwhile, it also expounds the risks that big data brings to Smart gird user-side from the perspectives of technology and user information security. Hope to provide some relevant materials of the Smart gird user-side risk management for our country.

Abstract: The Smart Grid is the development trend of grid technology. For guiding the construction of smart grid scientifically, quantitative evaluation for the level of technology maturity of the Smart Grid construction is necessary. The evaluation results can be used for determining the stage of the current construction of Smart Grid and summarizing the problems which came up during the process of construction, also finding the gap between current satiation and individual goals to determine the direction and key job in next step. This paper take the characteristics and goals of domestic Smart Grid into account, build a maturity evaluation model which assess the smart grid maturity in three dimensionstime, production processes and technical features separately. By setting the primary and secondary parameter the model can be used for smart grid assessment in any time, scenes and region. The model make a comprehensive coverage of various aspects in the smart grid construction process and the results of evaluation can be analyzed from different dimension to find the short slab to guide the work in next step.

Abstract: According to the problems which are relay protection is difficult to adjust and when line fault occurs it will easily get override trip in the underground 6 kV power supply system in Gu Shu-yuan Coal Mine. This paper presents a centralized selective short circuit and leakage protection system. Which focuses on the analysis of the short circuit longitudinal differential protection, based on pattern recognition method of single-phase earth leakage protection principle, and completes the rapidity and selectivity of the leakage fault line selection . Through the simulation, experimental and field operation shows that the schemes can effectively improve the reliability and safety of high voltage power supply system in Gu Shu-yuan Coal Mine ,it also establishes the necessary foundation of the goal of "network relay protection" in high voltage power supply system for in China.

Abstract: In this paper, targeted at reheated steam temperatures large time delay and strong nonlinearity characteristics in power plant, a multi-model predictive control strategy is proposed in light of the nonlinear characteristics of steam temperature control. This strategy utilizes the linearized model of nonlinear process at multiple working points to divide the process into several subspaces. A relatively accurate fixed model can be found in each subspace. Based on this, a global approximation model of complex object could be obtained. Simulation and application results show no matter for stable or load varying process, reheated steam temperature can be maintained in the required control range. It is much superior to the traditional PID control method.