Applied Mechanics and Materials Vols. 668-669

Abstract: Time delay estimation plays an important role in accuracy of leakage location in industrial boiler furnace. Considering about interference, like strong background noise, reverberation and so on, in boiler furnace, the LMS (least mean square) adaptive filter algorithm should be improved to meet certain environment above .In order to makes the LMS algorithm have the characteristic of fast convergence and small steady state error, an improved, power-normalized and variable step-size discrete cosine transform LMS algorithm is proposed, which combines the power-normalized discrete cosine transform LMS algorithm with the variable step size LMS algorithm that uses sliding forgetting-weighted window . The time delay estimation simulation in the strong-noise environment verifies the improved DCT-MVSS LMS algorithm can achieve good performance.

Abstract: Analytically describing the relationship among steady-state power flow numerical values is a significant proposition. Because the block diagram has the ability to describe the signal transmission analytically, we choose this method to study the steady-state grid’s power transmission rule. Each node or branch is chosen as a basic power transmission unit, and the ratio between the unit’s output power and input power is defined as power transmission gain. The power transmission relationship of each unit can be established according to the circuit analysis, and then the block diagram of each unit can be built on the basis of above relationship. Finally, a block of the whole power grid can be drawn according to the basic units’ connection relationships. The transmission relationship of the whole power grid was analytically expressed by the block diagram simplification method.

Abstract: The concept of Units and Grid Coordination (UGC) is introduced. Problems about UGC are drawn from some power interruptions. Some attentive issues are present in excitation selection and design in future power system such as reliable operation of PSS, coordination between excitation limiters and protections, operation mode of excitation control in running stage. Special attention should be paid to the selection of excitation type, parameters design of 1000MW class generator unit in planning stage.

Abstract: Distribution network is an important part of power system, the biggest feature of the structure is that the end of power network is directly connected to the users, demanding for safety and quality. This article introduces the low voltage distribution network operation theory, designs a low-voltage wiring mode, and by analyzing the disadvantages of this kind of connection, the optimal switching looped network operation is put forward; at the end of the low voltage distribution network flow calculation, by comparing the results of the loop closing operation with the open loop operation, the feasibility and advantages of loop operation is proved.

Abstract: This paper presents a novel method for optimal location of multiple-type power quality improving devices in distribution network through lots of simulations in IEEE 30 bus system. Three type devices have been considered, active power filter (APF), dynamic voltage restorer (DVR) and static synchronous compensator (D-STATCOM). Using proposed method, configuration is fulfilled according to a certain order and their own law. Results show this strategy is an effective method to find optimal locations for power quality improving devices with lower cost.

Abstract: Momentum BP neural network is used to diagnose the fault of high voltage electric power metering system according to the advantage of strong self-adaptation. First of all, the information of 7 operation parameters of metering system is extracted as input values of the neural network, secondly, we collect samples to train and test BP network and use 4-bit binary number to represent the normal circumstance and 7 main fault types, The results show that the momentum BP network model is effective in the fault diagnosis of high voltage electric power metering system.

Abstract: Taking the G4-73№8D centrifugal fan as research object and utilizing the software of NUMECA to simulate flow fields of volutes with different radial relative positions, the optimum central location of the fan impeller was obtained. The contrastive analysis of internal flow field which of the original and impeller center location optimization fan was under the rated and variable condition, showed that the optimized fan enhanced impeller and volute casing radial adaptive and the efficiency and export static pressure of optimized fan were improved.

Abstract: According to the structural characteristic of LNG cryogenic storage tank concrete prestressed wall and heat transfer theory, the paper obtain the calculation formula of the temperature field distribution, emphasis studying the heat flux distribution along the radial and axial and node temperature distribution of the section nodes for a 160,000 m³ capacity LNG cryogenic tank by ABAQUS. The paper also establish a set of method which is suitable for the temperature field analysis, proof the feasibility of finite element analysis technique in the analysis of the LNG cryogenic storage tank, and have a certain reference for the prestressed concrete walls and insulation layer design of the large LNG storage tank.

Abstract: Gas insulated switchgears (GIS) occupy an important position in the power system. Feature extraction is the key to GIS partial discharge pattern recognition, but the dimension of feature space is high, based on this, the article introduce the principal component sparse thoughts, firstly, through the 252 kV GIS partial discharge simulation experiment platform, set up the typical GIS partial discharge models, and uses AE method to obtain the signals, and through the principal component contribution rate to decide the degree of sparse, and according to the sparse component and the number of original features to decide the characteristics of related components, the results show that using this method can realize effective extraction of characteristic, and enhance the clustering results.

Abstract: Short circuit protection of high-voltage power lines in coal mine cannot realize selectivity with existing protection systems. To solve this problem, a scheme of protection and monitor underground based on PROFINET was proposed. The system is mainly composed of PROFINET network, monitor, controller, and integrated protector with PROFINET IO interface circuit. The system achieves protection and power monitoring network integration, completes the selectivity of short circuit protection, and can determine fault position quickly. Thus the troubleshooting time is cut and reliability of power supply network is improved. The simulation results show that the POROFINET real-time meets the requirement of protection and the system can realize short-circuit protection and power monitor function.