Advanced Materials Research Vols. 516-517

Abstract: Nano-porous monolithic SiO₂ aerogel as insulation material was prepared from silicon alkoxide as the precursor materials, followed by ethanol supercritical drying in this paper. In order to improve the mechanical properties of silica aerogel monoliths, the ceramic fibers were mixed in the pure aerogel, or integrating inorganic fiber materials as skeleton materials with low thermal conductivity supporting. Instron 5566, 5500R Material Testing Machine was used to measure the mechanical intensity. SEM was used to characterize the morphology of the silica aerogel monoliths. The thermal properties of the silica aerogels were determined by using the Hot Disk device. The results show that new type composite materials had a low effect on the thermal conductivities of the silica aerogel monoliths, but improved the mechanical intensity clearly. It made a great progress in the practical application of the SiO₂ aerogel monoliths.

Abstract: Based on the study of equipment condition monitoring problem in smart grid. Make an improvement to traditional wireless temperature measurement system within high voltage switchgear, according to electromagnetic shielding problem within switchgear and energy wastage problem of AD sampling method, proposes a new type of wireless network communication mode group and RC circuit temperature measurement method. Testing results in laboratory shows a promotion in terms of data accuracy and communication reliability, and a significantly energy-saving effect relative to traditional methods.

Abstract: This article researches the variable frequency technology of the power plant boiler induced draft fan, and to explain the conversion principle of the high voltage inverter frequency, through the analysis and calculation, it is known that the high voltage inverter power saving rate has reached 60%, and both save energy and reduce the loss.

Abstract: The polytetrafluoroethylene (PTFE) with the good dielectric property is a kind of nonpolar material. Made from the PTFE, the cannula has the high electrical insulation performance. This cannula can be applied to the equipment which requires for the high electrical insulation. There are 3 kinds of power-frequency voltage resistant experiments on PTFE cannulas with the inner diameter and outer diameter of 0.55/1.35, 0.7/1.5, 0.96/1.6, 0.46/0.96, 1.5/3.0 in the 1970m elevation. The PTFE cannulas are tested at the 85kV power-frequency voltage with the pure condition, the humidity condition, and the polluted condition separately in 1 minute. The result induced that the PTFE cannula did not be destroyed in all of the above experiments with no puncture sound, no smoke, no flashover and no burning. The insulating quality of the PTFE cannula is satisfied with the insulation requirement of the 85kV, i.e., the pollution level I.

Abstract: In the injecting steam wellbore, insulated tubings are connected with couplings. The coupling is short, but its insulation performance is poor. There are two different coupling types: couplings with insulation bushing and couplings without insulation bushing. By combining on-site experiments and fluent simulation, thermal insulation performance of coupling with insulation bushing and without insulation bushing were discussed. The results showed that the apparent heat conductivity of the coupling with insulation bushing is about 0.4W/(m•K), the apparent heat conductivity of the coupling without insulation bushing is about 3.6 W/(m•K). Insulation bushings promote insulation performance of vacuum insulated tubing coupling significantly.

Abstract: The construction of UHV (ultra-high voltage) transmission lines has become an important part of the planning of “smart grid" and “solid grid” in China. This article elaborated in recent years the UHV transmission lines construction status and possible problems, has made a comparative analysis on the angle of environmental carrying capacity, and put forward three effective suggestions, in order to improve the construction efficiency of UHV transmission lines engineering.

Abstract: A number of induction machine is widely used in people's daily life and agriculture manufacture, and the chance to meet all kinds of breakdown is large. Electrical machine's breakdown not only damage electrical machine itself ，but also make electrical machine suddenly break down and product line breakdown, result in great economy's loss and fatal result. So, research on electrical machine's fault diagnosis' technology, Possess significant theory's meaning and society economic benefit. Texts according to induction drive motor's common breakdown's feature, Directing to the past research settle electrical machine's breakdown's means's fault , Bring up base on improve the smallest two ride stand by vector machine (LS- SVM) de induction drive motor's fault diagnosis' means. Adopt muddleheaded optimization algorithm, Seek come out possess compare strong popularize ability de parameter. Combine induction machine's structural parameter with performance export model de build mold example, with cross validation techniques to compare confirm research means be used for motor fault diagnosis de validity.

Abstract: Cascade Speed Regulation System has the nonlinear characteristics and whose structure parameters are variable easily. Fuzzy control theory which based on conventional Cascade Speed Regulation System is introduced into such system. An asynchronous motor model is built, and a fuzzy parameter self-tuning controller is designed in this paper, the controller is simulated in Matlab, The simulation result shows the difference between the conventional PI controller and the fuzzy parameter self-tuning PI controller. From these simulation results, all performance indexes of the fuzzy PI controller with parameters self-tuning are vastly superior to those of the conventional PI controller.

Abstract: Basing on analysis the principle and mathematical model of the brushless DC motor, the paper proposes a control model on the basis of speed loop and current loop, fuzzy PI control model is adopted in the speed loop, and traditional PID control model is used in the current loop. It is showed that when the load or parameters vary, comparing to traditional PID control model, the fuzzy PI control model gets less fluctuation and better robustness.

Abstract: The AutoCAD, Gambit and ANSYS software are used to establish transformer oil flow-temperature rise model and mesh generation based on finite volume method, fluid mechanics and numerical heat transfer. A method that calculates temperature rise distribution of transformer winding regional wire and oil by FLUENT software, and a numerical example is given for an actual transformer.