• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.8
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• pp.1560-1565
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• 2011

The environmental pollution caused by green-house gases such as $CO_2$ and $SF_6$ has been becoming the main issue of industrial society. Many developed countries are making efforts to minimize the amount of $CO_2$ emission come from the operation of high voltage electrical apparatuses. As a part of these efforts, 180 countries signed the Kyoto Protocol in 1997 to cut back on their green-house gas emissions. Nowadays, the study on the development of dry air insulated switchgear (DAIS) which is known as an eco-friendly electrical apparatus is in progress. A DAIS is advantageous for minimizing the effect of impurities and enhancing the dielectric characteristics over an air insulated switchgear (AIS) by applying constant pressure to an enclosed cubicle. Therefore, a study on the electrical insulation performance of dry air as a gaseous insulation medium is conducted in this paper to substitute a gas insulated switchgear (GIS) for DAIS. As results, it is verified that the AC dielectric characteristics of dry air are similar to those of air and the lightning impulse dielectric characteristics of dry air are superior to those of air at 1bar pressure condition. However, dry air is of inferior dielectric characteristics to $SF_6$ at 4bar pressure condition. Finally, it is suggested that the internal pressure of DAIS should be over 4bar pressure to develop a high voltage switchgear which has similar electrical performance to a conventional GIS. Also, the empirical formulae on calculating the maximum electric field intensity at sparkover of dry air are deduced by experiments according to pressures. It is expected that these results are helpful to design and develop a high voltage electrical apparatus.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1473_1474
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• 2009

To develop electrically reliable high voltage apparatuses, the experimental study on the electrical breakdown field strength is needed, as well as theoretical approach. In this paper, lightning impulse breakdown characteristics considering utilization factors are investigated for the establishment of insulation design criteria of an high voltage apparatus. The utilization factors are represented as the ratio of mean electric field to maximum electric field. Dielectric experiments are performed by using five kinds of sphere-plane electrode systems made of stainless steel. As a result, it is found that dielectric characteristics are affected by not only gap length but also utilization factor of electrode systems. The results are expected to be applicable to the design of high voltage apparatuses.

• Journal of radiological science and technology
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• v.15 no.1
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• pp.107-113
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• 1992

Inverter type X-ray apparatus has been introduced and used several hospitals. Principle of inverter type X-ray generators are such as to convert the frequency of commercial power supply to high frequency and to control the high voltages for X-ray tube. Inverter generators are now on the way for futher development to elliminate single phase generators and three phase generators. We compared inverter type X-ray apparatus with conventional single phase 2 peak and three phase 12 peak, apparatus in the following aspects X-ray out put to tube voltage, linearity of X-ray out put to mA, HVL according to mA contrast to kV.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.12
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• pp.777-784
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• 1999

Since the ultra-high voltage power apparatus are recommended to withstand switching surge generated from the electric power system, the switching impulse voltage is generally used to verify this requirement at the testing laboratories. Recently, the international standard(IEC 60060-2) related to the high voltage measurement techniques is revised requiring a traceability of measuring system for high voltage measurements. In this paper, a reference divider for switching impulse voltage is developed satisfying the revised. IEC standard and the possibility of applications has been investigated. Therefore, the characteristics of the high and low voltage side resistor and the shielding ring have been analyzed including the step response characteristics of the prototype divider. Throughout various efforts, it is confirmed that our measuring device has shown compatible characteristics as a reference divider.

• Journal of electromagnetic engineering and science
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• v.9 no.4
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• pp.175-181
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• 2009

The measurements were performed to verify experimentally that the voltage arising on a telecommunication line by a power line is due to the induction phenomena because there has been an opinion that the arising voltage on a telecommunication line is not by induction, but by other causality. The voltage appeared on the telecommunication line by way of an electric field or magnetic field generated by the source apparatus that had been artificially made to provide intentional constant high-voltage or current in ELF, that is, 60 Hz as an emulated commercial power.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.29-34
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• 2007

The input and output impedances in a low voltage distribution system is one of the most important matters for power line communication because from the viewpoint of communication, the attenuation characteristic of the high frequency signals is greatly caused by impedance mismatch during sending and receiving. The frequency range is from 1MHz to 30MHz. Therefore, this paper investigates the input and output impedances in order to understand the characteristic of high frequency signals in the low voltage distribution system between a pole transformer and an end user. For power line communication, the model of Korea's low voltage distribution system is proposed in a residential area and then the low voltage distribution system is set up in a laboratory. In the low voltage distribution system, S parameters are measured by using a network analyzer. Finally, input and output impedances are calculated using S parameters.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.700-702
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• 2005

The most electrical apparatus should be able to withstand short-time current and peak current during a specified short time until circuit breakers have interrupted fault current. It defines the short-time withstand ability of electric a apparatus to be remain for a time interval under high fault current conditions. It is specified by both dynamic ability and thermal capability. KERI(Korea Electrotechlology Research Institute) recently constructed the new short-time current and low voltage short circuit testing facilities. This paper shows short- circuit calculation of transformer and describes high current measuring system, and evaluate the result of short-time withstand test used in $3{\phi}$ 90MVA short-time current testing facilities.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.52-55
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• 2003

For the dielectric insulation design of any high temperature superconducting (HTS) apparatus in the electrical power systems, the breakdown properties of cryogenic coolants such as $LN_2$ are an important factor of the insulating engineering. Therefore, this paper presented an experimental investigation of breakdown phenomena in $LN_2$ under AC voltage. And we studied the breakdown properties of LN2 with decreasing temperature. Also, the Weibull plots of the breakdown voltage of subcooled $LN_2$ at 65 K for the needle-plane electrode with electrode distance d= 10 mm are studied. The dependence of breakdown voltage for needle-plane and pancake coil-pancake coil electrode on temperature is illustrated. The experimental data suggested that the breakdown voltage of L$N_2$ depend strongly on the temperature of $LN_2$. The breakdown characteristics of $LN_2$ under quasi-uniform and non-uniform electrical field for temperature ranging from 77 K to 65 K were clarified.

• Journal of IKEEE
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• v.20 no.3
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• pp.310-313
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• 2016

In this paper, we propose the tester apparatus for 48 channel GM Tube sensor. The proposed apparatus can test up to 48 channel GM tube simultaneously to detect the defect and analyze the sensor characteristic. 300-1000V variable high voltage generation circuit is utilized for the apparatus suitable for the sensor characteristic. Thus, the proposed system is useful for various GM Tube sensor characteristic analysis. Multiple sensor testing environment is established for the early detection of the defect and the analysis to reduce the costs for manufacturing and rework. Developed 48 channel GM Tube sensor test is evaluated with certified testing equipment and shows excellent performance with respect to the uncertainty of the sensor test results.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.435-437
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• 2003

Recently, as the road capacity reaches the limit and environmental problems becomes serious, there is gradually increased a need for railroad vehicles that are environment-friendly and have time regularity, reliability and safety. Accordingly, in addition to conventional railroad vehicles, lots of vehicles are being newly developed. We developed the hardware and software of the measurement system for on-line test and evaluation of korean hish speed train. The software controls the hardware of the measurement data and acts as interface between users and the system hardware. In this paper, we is studied for electric apparatus performance of railway vehicle using sensor. In order to this test is developed signal conversion system. Using this system, we obtained important result for pantograph voltage, battery voltage, axle speed, and running speed.