• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1394-1397
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• 1995

In the hazardous areas where explosive gases, vapor or mists exist, electrical apparatus and installations must be of explosion-proof construction to prevent or limit the danger of the ignition of potentially explosive atmosphere. In Korea, nine types of protection have been specified in the government regulations at present: flameproof enclosure, pressurization, oil immersion, increased safety, intrinsic safety, non-incendive, sand filling, encapsulation, and special types. Among these types, the intrinsic safety has the construction which limit or by-pass igniting the electric energy using electronic devices. This type has lots of merits but at the same time requires a high-degree of technology. In this paper, we investigated several dominating factors which affect the minimum ignition energy: this energy plays a very important role in design and evaluation of the intrinsic safety type electrical apparatus. Eletrode material, which is one of the most important factors, was intensively studied for the five sorts of material(Al, Cd, Mg, Sn, and Zn) with performing experiment in a low-voltage inductive circuit using IEC-type spark apparatus. The experimental results show that the minimum ignition energy of electrode material is varied: highest in Cd and lowest in Sn. We also confirmed the effect of eletrode make-and-break speed and magnetic field magnitude.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1620-1622
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• 2003

Recently, as the technology for the development of high voltage power apparatus using SF6 gas has made remarkable progress, it became possible to develop more compact power apparatus adopting single body substation system. In these gas insulated power apparatus, it is impossible to achieve perfect and safe insulation using only SF6 gas, because some solid insulation parts should be installed to support current-carrying conductor parts for electrical and mechanical safety. When spacers were installed in SF6 gas insulation system, they were exposed to severe electrical intensification which could reduce system insulation performance and restrict the rated operating voltage So, it is necessary to clarify the dielectric characteristics of spacers by analytically and experimentally, in order to design and develop more compact and optimum gas insulated systems. In this paper, the field distribution of three-phase spacers were investigated using three dimensional electrostatic field analysis tool adopting BEM method. And the obtained results were compared to the conventional two dimensional computations. According to these three dimensional calculations, it was possible to find out weak points in the spacer more clearly and these results could be applied to design more compact and optimum three phase spacer developments.

• International Journal of Safety
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• v.4 no.2
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• pp.18-23
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• 2005

There are many electrical connections in the electric apparatus and most fires due to a fault contact result from a failure or misuse of electric apparatus and installation. The fault contact happens between electrical connections by the loose and the mechanical vibration. In this paper, we have investigated thermal and electrical properties of screwed electric contacts due to the mechanical vibration. The exciter was connected to a signal generator and power amplifier that provided the vibration frequency and amplitude. The vibration, temperature and voltage data were sent to a data acquisition system (DAQ). In the case that fault contact took place, the arc happened between the screwed electric contact and electric wire, heat due to the arc was transmitted to the adjacent insulators, for which the oxide could be generated more. In addition, a spark was generated and the insulator began to melt. Thus, the possibility of electrical fire became the highest in this case. Finally, when the fault contact takes place due to vibration, the hazard of an electric accident is very high.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.224-231
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• 2019

Recently, the pollution of groundwater has become serious. In particular, the contamination of groundwater near livestock farms is becoming increasingly severe and it is difficult to drink with drinking water. In this paper, a groundwater purifier apparatus that can be installed in a community well was designed. The designed groundwater purifier apparatus enables a RO membrane filter and UV sterilization to remove pollutants, such as heavy metals, bacteria, and organic compounds. In addition, electrical conductivity, pressure, and flow sensors were added for remote monitoring. Remote monitoring of the system can determine the level of fouling and contamination of RO membrane filters through pressure and flow sensor data, and can record changes in the contamination and condition of groundwater through the electrical conductivity of the feed water. The designed groundwater purifier apparatus was installed at a farmhouse and remote monitoring. The result after 15 days of operating a groundwater purifier apparatus and analyzing the monitoring data revealed an average permeate water flow rate of 2.67L/min and an average water pressure of 7.09kgf/㎠, indicating that the RO Membrane filtered without fouling and clogging. The average electrical conductivity was 796.6 S/㎠ of the feed water and 55.6 S/㎠ of permeate water, which is similar to that of general tap water. Through this, it was confirmed that no pollutant occurred in the surroundings. Therefore, the designed groundwater purifier apparatus can confirm the replacement time of the RO membrane filter in advance through remote monitoring, and check the pollution state of the groundwater.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.114-120
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• 2014

In this paper, a method for multi-physics analysis of the temperature-dependent properties of an oil-immersed transformer is discussed. To couple thermal fields with electromagnetic and fluid fields, an algorithm employing a user defined function (UDF) is proposed. Using electromagnetic analysis, electric power loss dependent on temperature rise is calculated; these are used as input data for multi-physics analysis in order to predict the temperature rise. A heat transfer coefficient is applied only at the outermost boundary between transformer and the atmosphere in order to reduce the analysis region. To verify the validity of the proposed method, the predicted temperature rises in high-voltage (HV) and low-voltage (LV) windings and radiators were compared with the experimental values.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.493-494
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• 2008

During the last years hollow core insulators started their success story in the field of high voltage engineering for electrical apparatus, substituting porcelain insulators. The termination, also named top and bottom fittings are used for the connection to the rest of the electrical apparatus. The top and bottom flange are attached to the composite to transmit mechanical load and also ensure the gas tightness. They are bonded by epoxy glue with a glass transition temperature of about $130^{\circ}C$-$150^{\circ}C$ the glass reinforced epoxy tube of filament winding. This paper describes the results of a study on the bonded joints of fiber reinforced epoxy tube and cast aluminum. This suggests that surface roughness and glue types play an important role in evaluating of gas sealing capability on the flange and fiber reinforced epoxy tube in the composite hollow bushing.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.37-42
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• 1990

In order to obtain optimal design criteria and operating parameters, a Single-sided Linear Induction Motor (SLIM) is analysed by using a 2-D finite element method with magnetic and current vector potential. In the analysing procedures, the governing equation is derived from Maxwell's equation combined with the magnetic vector potential. As a forcing term, 3-phase voltage source is employed using the Kirchhoff's voltage law in order to look into effects of the unbalanced 3-phase currents and air gap flux density. Also, 2ndary eddy current distribution, longitudinal end and transverse edge effects are in turns visualized by flux lines in 3 different analysing planes as functions of frequency and input power.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.106-109
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• 1991

A magnet is designed and analysed using a finite element method program (FLUX2D), which will be employed to the 2-module MAGLEV test vehicle for developing of DAE JEON EXPO '93 Magnetic Levitation System. Levitation force. guidance force and thermal characteristics are examined according to the variation of parameters of the magnet ie. pole width, window area, rail configuration, input current and so on. An optimal geometry of the magnet are provided.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.59-61
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• 2003

The natural element method is a kind of meshless Galerkin method. The shape function is derived from the natural neighbor coordinates interpolation scheme. Natural neighbor shape functions are $C^0$ everywhere, except the nodes where they are $C^0$. The numerical integration is carried out using the Delaunay triangles as the background cells. The method is applied to the test problems and simulation results show that the natural element method can give accurate solutions for the electromagnetic field problems.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.395-397
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• 2002

Recently, electric heating using midnight power has brought a rapid increase. Therefore, the increase of midnight power use has much influenced on midnight load pattern and share more than 20% of total midnight electricity consumption. Hence, the distortion of load by using midnight power apparatus is severe and made the usage pattern ineffective electricity usage pattern. This paper analyze the load pattern of midnight power apparatus and policies that can effectively build midnight load. In addition, it provides policies on shifting midnight power apparatus load.