Applied Mechanics and Materials Vols. 448-453

Abstract: A common field distortion triggered spark gap utilizing geometric field enhancement at sharp edges usury operates in a cascade mode via the trigger electrode. A new trigger concept is propos this research allowing strong non-uniform electric field enhancement with output precision voltage by holding-off DC voltage ranging from 1 to 135 kV and direct breakdown between the two main electrodes. A test setup was designed to testing with four modes of operation as mode A, B, C and D to prove the feasibility on this concept. Were result experimental r the recommended mode of operation is mode A and mode D considered to be unsatisfied to most applications. The best results achieved by using the triggering with mode A at a wide precision designed breakdown voltage range 1-120kV with a minimum percentage ratio of Fire/Self-fire Voltage lower to 36-47%

Abstract: This paper describes the modern Type D double-ended location principles and the wavelet modulus maxima theory and presents a principle and a scheme which bases on wavelet transform of the Type D double-ended traveling-wave distance protection for HVDC traveling line. Then set up a monopolar HVDC system and simulate it by PSCAD/EMTDC and Matlab. Simulation shows that this protection principle and scheme is right and feasible.

Abstract: Multi-terminal HVDC transmission system based on voltage source converter is a promising topology for the integration of the renewable energy sources. The fault characteristics of VSC-MTDC system under DC side faults was analyzed in this paper, as well as the particular requirements for the protection strategy. On the basis of the work metioned above, a four-terminal DC connected transmission system model was built in PSCAD/EMTDC. The boundary protection algorithm was proposed and the wavelet analysis was introduced. The protection scheme for VSC-MTDC transmission lines is based on the attenuation characteristics of line boundary for high frequency transient signals, which constitutes the operation criteria of the boundary protection. The protection scheme puts forward an effective method for the protection selectivity of the VSC-MTDC transmission system.

Abstract: Critical construction process parameters and necessity of experimental study concerning tension stringing of large-section conductor are elaborated in this paper and in addition, test details related to critical process parameters of tension stringing construction is researched by citing the example of 1250mm² large-section conductor, according to which test plan is worked out and test rack is designed.

Abstract: As a basic auxiliary service, primary frequency regulation (PFR) is provided with significant effect in secure and stable operation for grids. Thermal power plants undertake important task in PFR by virtue of it is main type in grid-connected power plants. However, some problems such as slow response, inadequate load variable quantity, or even reverse regulating effect exist in actual PFR process. In PFR relative control logic, PFR command, load variable quantity command and main steam pressures influence must be taken into consideration. Regulating valves flow characteristics and adjustment of overlap degree can result in imbalance of load regulating under different working point. Frequency data utilized by grid dispatching center and power plant are inconsistent so that PFR evaluation may be affected. On the premise of safe operation in power plant, energy storage can improve units load in a fast time. A series of optimization measurements are put forward on the basis of the above four influence factors. In accordance with respective influence characteristics, these measurements possess a certain reference significance to improve performance index of PFR.

Abstract: Choosing LW15-550Y porcelain high voltage SF6 circuit breaker as the research subject, we designed the lead laminated rubber bearing (LRB) seismic isolation device for LW15-550Y circuit breaker. We finally gets the results that the LRB isolation system increases the flexibility of the breaker structure and improves the seismic performance of the high voltage circuit breaker structure.

Abstract: Based on PSCAD/EMTDC simulation platform, this paper analyses the harmonics caused by the process of rectifier and inverter and DC bias of transformer in Yindong ±660kV HVDC transmission system. The results indicate that, characteristic harmonics of 660kV HVDC system AC bus give priority to 12k±1 time harmonics and bring serious influence to the AC system of the rectifier and converter station; the characteristic harmonics of DC lines are mainly about 12k time and the voltage ripple factor is in the specified scope; both the odd and even harmonic components are increasing significantly under DC bias than that without DC bias,which thereby makes the power transformers become the severe harmonic sources.

Abstract: Polymer electrolyte organic polymer as the main matrix, poor mechanical properties, in addition, the ion transfer is mainly in the amorphous regions completed and the polymer electrolyte composite polymer generally has a strong ability to crystallize, thus greatly suppressed ion transmission. People try by the incorporation of different types and contents of the filler to improve the mechanical properties of the polymer electrolyte, lower crystallinity and increase the ionic conductivity. Various inorganic nanoparticles are the most common type of doping filler.

Abstract: Based on low temperature superconducting (LTS) & high temperature superconducting (HTS) material classification, the superconducting generators can be divided into LTS generators and HTS generators. The research status and characteristics of superconducting generators are summarized; and several topological structures of superconducting generators are introduced. Compared and studied traditional rotating machine with superconducting rotating machine, pointing out the present superconducting generators bottleneck problems. Finally, the prospects of the development of superconducting generators are described.

Abstract: Using wavelet analysis for non-stationary signal de-noising of electro-mechanical system is considered to be the best approach, and wavelet threshold de-noising method is the most simple method that needs the minimum amount of calculation. But this method in selecting threshold functions needs to be improved. Based on different domestic and foreign methods of improving threshold function, propose an improved bivariate threshold function. According to the simulation of non-stationary signal de-noising, the results show that the optimal de-noising results of different signals exist by taking different parameters. Compared with all the de-noising effects, application of the bivariate threshold function considering signal-to-noise ratio and mean square error is superior to the traditional soft and hard threshold functions. At the same time, it can significantly improve the filtering precision, and reserve the main signal details while effectively removing the noise well.