Dong-Young Lim

A Study of Surface Discharge Characteristics for Dew-Point of Dry-Air and Materials or Shapes of Solid Insulator in Quasi-Uniform Field

This study investigates the surface discharge characteristics of solid insulators by varying their materials, their shapes, and the dew-point of dry-air. The methodology of this study is that a quasi-uniform field is first applied to a test chamber. Then, the chamber is filled with dry-air as an insulation gas which pressure is varied from 1 to 6atm while applying an AC voltage to the chamber. The used solid insulators are teflon, polycarbonate, and bakelite. As the dew-point is lower and the pressure of dry-air is higher, the flashover voltage of all solid insulators increases more. When each characteristic of the solid insulators is compared under the same gas pressure, the flashover voltage of teflon is the highest. Then, the flashover voltage of polycarbonate is higher than that of bakelite. Moreover, it is observed that the flashover voltage increases as the diameter and the thickness of each solid insulator become larger and thicker, respectively. However, the thickness of the solid insulators is more critical for increasing the flashover voltage than their diameter.

Surface Discharge Characteristics of Solid Dielectrics in N 2 /O 2 Mixture Gas for Eco-Friendly Insulation Design

In this paper, we deal with a surface discharge that caused an aggravation of the dielectric strength in the mixture gas, When composit dielectrics were formed from the use of a solid dielectric. It was found from this study that the surface discharge voltage was deeply involved in the mixture ratio of , the electrical property of the solid dielectric, kind of the solid dielectric, an electric field at the triple junction and a medium effect. These results expect basic data that will be used to transmission and distribution power system equipment using the mixture gas.

A Study on Characteristics of Insulation Breakdown and Surface Discharge by the Mixing Ratio of Dry Air/O 2 gas mixtures

This paper presents the discharge characteristics and economic feasibility of a Dry and a mixture gas in order to review alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry and the mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry and the mixture gas were discussed so that Dry mixture gaswas more suitable than mixture gas to the alternative.

Dynamic Thermal Model of a Lighting System and its Thermal Influence within a Low Energy Building

This paper focuses on the heat gain of a lighting system, one of the most-used appliances in buildings, and its thermal effect within a low energy building. In this study, a dynamic thermal model of a lighting system is first established based on the first principle of thermodynamics. Then, thermal parameters of this model are estimated by experiments and an optimization process. Afterward, the obtained model of the system is validated by comparing simulation results to experimental one. Finally it is integrated into a low energy building model in order to quantify its thermal influence within a low energy building. As a result, heat flux of the lighting system, indoor temperature and heating energy demands of the building are obtained and compared with the results obtained by the conventional model of a lighting system. This paper helps to understand thermal dynamics of a lighting system and to further apply lighting systems for energy management of low energy buildings.

A Study on the Surface Discharge Characteristics by Dielectric Constant and Diameter of Solid Dielectrics to Improve Surface Dielectric Strength in Eco-Friendly Insulation Gas

This paper studied surface discharge characteristics by a dielectric constant and diameter of solid dielectrics in mixture gas. Applied electric field strength at mixture gas was changed from the dielectric constant and diameter of the solid dielectrics, and insulation performance of the mixture gas determined surface discharge voltage. In each of the diameter at the solid dielectrics, the surface discharge voltage was increased by lengthening surface distance, whereas increasing rate of the surface discharge voltage was different from gas pressure. Thus, In this paper, main factors of surface discharge are as follows. 1) Insulation performance of mixture gas, 2) Dielectric constant of solid dielectrics, 3) Surface discharge path. It was clear that the surface discharge voltage depend on the main factors. These results will be applied to useful data for an eco-friendly composite insulation design.

The Insulation Evaluation of N 2 :O 2 Mixture Gas

With the improvement of industrial society, high quality electrical energy, simplification of operation and maintenance, and ensuring reliability are being required. Also we request an urgent change from SF? gas to an environment-friendly gas insulation material. In this paper, the experiments of breakdown characteristics by pressure and gap change of N₂/O₂ mixture gas through a GIS (Gas Insulated Switchgear) model were described. This paper reviews basic data of the surface discharge characteristics for Teflon resin in not only pure N2, N₂:O₂ mixture gas as being focused on environmentally-friendly insulating gas, but also SF?. Also, insulation characteristics by breakdown voltage and surface discharge voltage of N₂:O₂ mixture gas in the experimental chamber were studied.

Mechanism and Characteristics of the Surface Flashover on the Laminated Solid Dielectric in N 2 /O 2 Mixture Gas

This paper presents the surface flashover mechanism of a laminated solid dielectric and describes the surface flashover characteristics with the inherent capacitance of the laminated solid dielectric in a mixture gas (8:2) under an quasi uniform field. It was found that the electron emission at a cathode and the high-local electric field region around an anode were important factors to reasonably describe the surface flashover mechanism. The surface flashover voltage by the mechanism decreased with the inherent capacitance increase of the laminated solid dielectric. In addition to the surface flashover mechanism and its characteristics, the surface flashover voltage equations as a function of the inherent capacitance were derived by considering a gas pressure used in future eco-friendly GIS and the factors influencing the surface flashover.

Surface Flashover Characteristics on Poor Contact in N 2 /O 2 Mixture Gas under Non-Uniform Field

This paper presents the surface flashover characteristics to simulate the poor contact between an anode and a solid dielectric in a mixture gas (8/2) under a non-uniform field. The surface flashover voltage of the mixture gas revealed the irregular tendency that was not in accordance with the Paschens law with an increasing gap of the poor contact. In addition, the insulation performance of the mixture gas at 0.6MPa was comparable to that of gas of 0.1MPa based on the insulation performance on the poor contact. These results are able to apply the insulation design of eco-friendly gas insulation switchgear considering the internal faults.

Analysis of Breakdown Voltage Dispersion and Breakdown Process in Mineral Oil

This paper presents a breakdown voltage and a process of breakdown progress in mineral oil under an quasi-uniform field with decomposition products which occur after the oil discharge. The breakdown voltage in the oil revealed the characteristics of dispersion regardless of an electrode gap. The cumulative probability distribution was used to analyze the dispersion of the breakdown voltage. In addition, the process of breakdown progress in the oil can be reasonably described by the electron breakdown theory based on both electrons emitted from the cathode and ions by field-aided dissociation of the oil. The proposed breakdown process will be used for the basic data to explain the behavior pattern of the decomposition product to cause the dispersion of the breakdown voltage.