• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1869-1871
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• 2004

The primary role of ZnO arresters is to protect transmission and distribution equipments against lightning surges. The extremely nonlinear V-I characteristics of the ZnO arrester obviates the need for isolation gaps and consequently it is continuously connected to line voltage. For this reason, ZnO arresters are degraded with increasing with time in actual power systems. In this work, the characteristics of the luminous events between the ZnO block and electrodes were investigated. As a result, the luminous events were effected by the impulse and the near polarity of the luminous event was intense near the grounded electrode. Also the luminous event may cause the degradation of ZnO arrester block.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1337-1340
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• 1995

For the purpose of rational design of air insulation, it is need to experiment with similar to real shape test object and conform the characterisics. But basic distances of air insulation of transmission line, tower, etc. can be acquired from flashover characteristic of rod-rod, rod-plane electrodes. In this paper, before field test of 765kV transmission line for determination of distances of phase to ground insulation, we execute lightning, switching impulse test with test electrod(rod-rod, rod-plane) against clearances of air insulation. Each tests use up-down method and consist of 30 times flashover test. Flashover data treatment program and air correction program following IEC 60-1(1987) standard were completely builted.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1521-1522
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• 2011

뇌임펄스에 의한 절연유체 내 절연파괴 현상은 스트리머 채널에서의 유체유동과 기체유동이 동시에 발생한다. 스트리머 개시와 동시에 발생하는 기포들은 절연파괴에 직접적인 영향을 미치며 이를 모의해석하기위해서 2상유동이 고려되어야한다. 2상유동이 고려된 뇌임펄스 응답 유한요소해석은 전계에 의한 푸아송 방정식과 전자, 양이온, 음이온에 대한 전하연속방정식으로 구성되며 전계 방출과 열전자 방출효과를 경계조건으로 부여하였다. 기체 전리현상은 타운젠트 이론을 도입하였으며, 유체 전리현상은 제너 이온화 모델을 도입하여 수학적 모델링을 통한 2상유동으로 결합하였다. IEC standard #60897의 표준규격에 따라 침-구형 전극을 설계하였고 2차원 축대칭 간략화모델에 적용하여 실험적 결과와 비교분석함으로써 신뢰할 수 있는 수치해석기법이 제시되었다.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.131-132
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• 2008

This paper describes a method to estimate the thermal lifetime of coil used in the dry-type molded transformer which is widely used in the domestic distribution system. In order to reduce the testing time, temperature accelerated aging test is planned. Finally, the thermal lifetime estimation method is composed of a temperature aging test and a cyclic test of temperature, humidly and lightning impulse voltage withstand test.

• Progress in Superconductivity and Cryogenics
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• v.13 no.3
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• pp.5-9
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• 2011

DC high-temperature superconducting(HTS) cable system has attracted a great deal of interest from the view point of low loss, dense structure and large capacity. A HTS cable system is made of cable and termination. The insulating materials and insulation technology must be solved for the long life, reliability and compact of cable system. In this paper, we will report on the dielectric breakdown characteristics of insulating materials for HTS cable and termination. The AC, DC and lightning impulse breakdown strength of laminated polypropylene paper(PPLP) and glass fiber reinforced plastic(GFRP) have been measured under nitrogen pressures in the range of 0.l-0.4MPa. PPLP and GFRP are found to have a significantly higher DC breakdown strength. Also, DC surface flashover voltage of negative polarity is slightly higher than that of positive polarity in GFRP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.49-49
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• 2010

In this paper, a full scaled gas discharge chamber was designed and fabricated for evaluating the dielectric performance of SF6/N2 mixture gases. And it describes work on AC and lightning impulse dielectric characteristics of SF6/N2 mixture insulation gas from experiments and full scale models.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.175-178
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• 2004

The microstructure, electrical, and clamping voltage characteristics of ZPCCD-based varistors were investigated at sintering time of 2 and 3 h. The average grain size and density of varistor were increased from 15.2 to 19.0 and from 5.5 to 5.6 $g/cm^3$ with sintering time, respectively. The nonlinear exponent was 65.4 for 2 h and 37.4 for 3 h, and leakage current was 0.54 ${\mu}A$ for 2 h and 0.67 ${\mu}A$ for 3 h. The dissipation factor was 0.0397 for 2 h and 0.0457 for 3 h. The clamping voltage ratio at surge current($8/20{\mu}s$) of 10~300 A was increased in the range of 1.56~2.17.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1917-1919
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• 1996

This paper aims to extract the air clearance in 22.9KV the metal enclosed switchgear. First, we investigated the actual conditions on the clearance in the metal enclosed switchgear which has been used in domestic. The test model and 9 test electrodes for the air insulation strength tests have been designed and manufactured based on the investigation results. To find optimal clearance in the metal enclosed switchgear, we performed 50% flash-over test by the up and down method and lightning impulse withstand voltage test. And we obtained results that the clearance or phase-to-phase is 230 [mm] and clearance or phase-to-earth is 210[mm].

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.305-308
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• 2008

This paper presents characteristics of soil ionization when high currents such as lightning and switching surge currents are injected into a grounding rod. Soil ionization phenomena are investigated by using both voltage and current signals recorded by oscilloscope. As a result, a critical electric field intensity($E_C$) for ionization is decreased with reduction of grain size. The pre-ionization resistance($R_1$) and post-ionization resistance($R_2$) at the sand with fine grain size are getting lower with increasing current magnitude. Finally, the time to ionization($t_1$) and ionization current peak($t_2$) of fine grain size are significantly shorter than those of medium grain size.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1161-1165
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• 2005

Due to the miniaturization of electrical components and assembles on signal circuits, transient overvoltages caused by switching operation or lightning surges have become more interesting concern to the field of electrical engineering. In this paper, the development of surge protective devices(SPDs) that can protect sensitive signal device on shipboard from overvoltages are described. Two kinds of SPDs are designed and tested by using a combination surge generator which can produce the standard impulse current of 8/20${\mu}s$ 2.1kA according to the IEC 61000-4-5 standard. From the simulation and experimental results, it is confirmed that the proposed SPDs have an enough protection performance with a low insertion loss and a low clamping voltage.