Applied Mechanics and Materials Vols. 284-287

Abstract: Due to the continuing renovation of the modern technology and the demand for the better consumer products, electricity has become one of the important factors that affect people’s life. The electrical switch is an important element of the electrical device and has been used intensively in industry and transportation devices, such as electrical bicycle, electrical motorcycle, winch etc. As the increasing usage of the electrical switch, the switch quality requirement increases as well. The important factors are contact point mass transferring loss, electric arc energy and contact point resistance and loss. Once the contact point fails to function, the whole electrical device ceases to function. However, regarding the electrical efficiency, in addition to the effect of the contact point materials, the structure is an important factor. In this study the structure of the electrical switch is studied and the effects of spring stiffness, guiding pin and ring to the switch lifespan are discussed. Taguchi method was used to design the experiment. L⁹(3₄) Orthogonal Array table was used to perform and discuss the effect of four factors to the desired characteristics; that is to minimize both the contact voltage-drop and the contact temperature increase. Four factors chosen are guiding pin material, compression spring, contact spring and buckle. Test results show that contact spring has the most effectiveness to the contact voltage-drop and temperature increase and is followed by compression spring. Guiding pin and ring type have minimum influence.

Abstract: Transformer is the main element of a power system. The insulation of transformer has to be maintained and do regular routine service in order to deliver power effectively. Recently dielectric measurement has been used for assessing the condition of oil/paper insulation. There are several nondestructive dielectric testing method for determining the conductivity and moisture content of insulation materials in a transformer. This research utilizes one of the dielectric methods which are Polarization and Depolarization Current (PDC) analysis in order to identify insulation condition of mineral oil. This paper presents the classifications of breakdown, overheating and partial discharge faults in mineral-oil insulated transformer by using PDC measurement data analysis. The classification is based on the data pattern and statistical analysis. The samples data was obtained from laboratory and from site testing. An analysis result shows that different type of faults will give different outcome to the PDC pattern and as well as statistical data. Based on the result, these three types of faults can be used to identify the insulation condition by using PDC measurement data analysis. Introduction

Abstract: This paper proposes an algorithm to search the suitable site for the installation of the High temperature Superconducting (HTS) cable. The HTS cable is able to transmit a large amount of electricity without additional power transmission facilities. However, it is not desirable to install the HTS cable anywhere because the HTS cable is the high price facility. The best location for the installation of the HTS cable is the place that congestion of transmission line is occurred in. If the HTS cable is used in congestion area, an additional transmission facility is not necessary for stable operation of power system. The technology level of the HTS cable has been improved consistently so the installation of the HTS is possible to use in the limited part of power system. In this paper, an algorithm is suggested to search the proper place for the HTS cable and verified by case study in the power system.

Abstract: It has been acknowledged that the insulation of the power transformers is the main cause of their failures. This can easily be attributed to the fact that all power transformers connected to electrical power networks bears loads and the load causes temperature rise and degradation of the cellulose paper. The by-product of the degradation includes moisture. The high temperature and moisture combine to accelerate the rate of insulation breakdown by increasing the material conductivity, σ and also increase the aging rate of the transformer. This paper has reviewed some transformer assessments and tests as sample data to study the effects of temperature and moisture on power transformer insulation conductivity. The results from the tests and measurements were analyzed and presented accordingly. The analyses of results found that irrespective of the assessment technique used, be it FDS, PDC or RVM, conductivity of the transformer insulating materials increases with any increase in both temperature and moisture content.

Abstract: Polarization and Depolarization Current (PDC) testing is a non-destructive dielectric testing method to determine the conductivity and moisture content of the insulator. This paper presents the application of microprocessor in HVDC (High Voltage Direct Current) switch to switch “ON” and “OFF” the PDC measurement circuit. This paper also reviewed the involvement and also the function of microprocessor to control the switching circuit and also the function of auxiliary circuit in controlling the voltage balancing of each device in the IGBT (Insulated Gate Bipolar Transistor) circuit. A simple and reliable technique of voltage-balancing circuit for the series operation of devices is presented to overcome the unbalance load and it is well controlled by the microprocessor circuit. The operation principle and analysis are presented and tested on 2 series-connected of 600-V/5-A insulated gate bipolar transistors to handle 1-kV/400-A switching for 10,000 seconds.

Abstract: In this paper, a series resonant converter with high-frequency high-voltage transformer for plasma generator is presented. The high-frequency, high-voltage electric source is designed by employing a series load-resonant converter with the plasma generator as part of the electric circuit. The equivalent circuit of this high-frequency transformer modeled by the introduction of the stray capacitance is proposed and the circuit model of the high-voltage plasma generator is conducted as well. Thus, the overall model of the high-voltage plasma generator is built and the designing procedures for appropriate selections of the corresponding resonant-circuit parameters can be established. Finally, a high-voltage plasma generator with 220V, 60Hz, and 1kW input, plus a 22 kHz and over 8kV power converter output, is realized and implemented.

Abstract: This paper presents research motivated by industrial demand for energy storage system for city transport vehicles. The kinetic energy is accumulated into the supercapacitor during vehicle braking. This energy can be used to accelerating in next time. It is important to save the energy in the vehicles, which accelerate very often.

Abstract: Lungmen nuclear power plant (NPP) is the first ABWR (Advanced Boiling Water Reactor) in Taiwan and still under construction. It has two identical units with 3,926 MWt rated thermal power each and 52.2×10⁶ kg/hr rated core flow. The core has 872 bundles of GE14 fuel, and the steam flow is 7.637×10⁶ kg/hr at rated power. According to the chapter 4 of Lungmen NPP FSAR (Final Safety Analysis Report), the design features of Lungmen NPP improve the core stability performance and assure that it is more stable than the current BWR (Boiling Water Reactor) NPP in the normal operating regions. In this research, the LAPUR6 stability analysis of Lungmen NPP is performed in order to versify the design features of Lungmen NPP which causes the more stable than the current BWR NPPs. The analysis results of LAPUR6 indicate that the design features of Lungmen NPP can improve the core stability performance effectively and result in the more stable than the current BWR NPPs.

Abstract: The objective of this study is to utilize TRACE (TRAC/RELAP Advanced Computational Engine) code to analyze the reactor coolant system (RCS) pressure transients under ATWS (Anticipated Transient Without Scram) for Maanshan PWR (Pressurized Water Reactor) in various MTC (Moderator Temperature Coefficient) conditions. TRACE is an advanced thermal hydraulic code for nuclear power plant safety analysis, which is currently under development by the United States Nuclear Regulatory Commission (USNRC). A graphic user interface program named SNAP (Symbolic Nuclear Analysis Package), which processes inputs and outputs for TRACE is also under development. Maanshan nuclear power plant (NPP) is the only Westinghouse PWR in Taiwan. The rated core thermal power of Maanshan with MUR (Measurement Uncertainty Recapture) is 2822 MWt. In document SECY-83-293, all initializing events were classified as either turbine trip or non-turbine trip events and their ATWS risks were also evaluated according to these two events. Loss of condenser vacuum (LOCV) and Loss of normal feedwater (LONF) ATWS were identified as limiting transients of turbine trip and non-turbine trip events in this study. According to ASME Code Level C service limit criteria, the RCS pressure for Maanshan NPP must be under 22.06 MPa. Furthermore, we select the LOCV transient to analyze various MTC effects on RCS pressure variations.

Abstract: The number of Distributed generators is currently increasing, and the electrical industry is trending toward regional supply-and-demand and resource integration. Thus, a model that can forecast small-area peak electrical loads is an indispensable part of power infrastructures. This study constructs innovative model for forecasting small-area peak electrical loads. The main aspects considered were the accuracy of the forecasting model and the convenience of follow-up maintenance and management of the model and data. This study used yearly peak load value and total power data from substations to construct regression tree models. These acted as models for the small-region peak electrical load of substation districts in the Taipower distribution systems. The errors of these forecasting models were substantially smaller than those of the least squares model originally used by Taipower to forecast peak load. The addition of exogenous factors was unnecessary. Additionally, our results were superior regardless of whether once or incremental models were adopted for the data. This confirms the usability of our models.