• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.361-364
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• 2008

This paper deals with assessment of electrical safety for grounding system of buildings by investigation on the spot at construction site. The investigation was carried out for grounding method, grounding type, shape of grounding electrode, grounding for lightning protection system, continuity of steelwork in reinforced concrete structure and so on. The investigation on the spot was performed by researcher, engineer with over fifteen years of industry experience all over the country. As a result of investigation on the spot to 13 buildings, common grounding method was dominant. A new grounding system based on international standards includes unity grounding system, structure grounding utilizing steel reinforced concrete, equipotential bonding. use of surge protective device.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.53-58
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• 2002

Sheath circulating current is increased as the change of sheath mutual impedance which is caused by imbalance of cable system, and different section length between joint box. If excessive current flows in sheath. sheath loss will be increased and then transmission capacity of underground transmission system is reduced. Accordingly, This paper proposed sheath current reduction device using resistor and reactor and proved the reduction effect of that device using EMTP/ATP. And also in this paper, when transients are occurred at the underground system with reduction device by ground fault and lightning surge. we analyzes transient effect of system variously. From this result. authors establish the protection methods of sheath circulating current reduction device.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.468-468
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• 2000

In our laboratory, the control aspects are investigated in the photovoltaic power generation systems (PV systems). The PV system is very good for earth environment, but if it connects to power network system, many problems are raised (protection, voltage, harmonics etc.). In this paper, we present the result of the basic studies for the building of the PV system that amplifies the electric energy obtained from the solar cell. We consider electronic circuits in order to protect the PV system from power surge induced by lightning and also design an electronic circuit in order to detect defaults in the power network system. We would like to integrate these circuits into the PV system by considering its control equipment build by 8-bit microcomputer using various control theory (fuzzy, neural network etc.).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2296-2298
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• 1999

The stationary ground resistance and the transient ground impedance of grounding system are very important parameters in the field of lightning and surge protection. But, it is very difficult to obtain correct values of them in large-scale grounding system. In this paper, the stationary and transient ground impedances of a large-scale grounding system have been measured and analyzed under impulse currents. In order to obtain correct values of them, we have described Z-v(impedance vs ground potential rise) distributions and Z-t waveforms. The transient ground impedance of 36 [m] long three-parallel grounding piles have showed the inductive aspects and the hysterisis region under impulse currents.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1578-1582
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• 1998

The ground potential rise generated by the switching surge or lightning stroke may be dangerous to personnel and cause damage to electronic control parts. For a first step to the transient performance analysis. high frequency impedances of grounding grids have been calculated and discussed. Grounding grids include 7 square grids from $10m{\times}10m$ to $80m{\times}80m$. The high frequency current was injected into the center and a corner of the grounding grid. The calculation results indicate that the impedance of the grounding grid is significantly influenced by frequency and the point of injection of the current. and the effective radius of a large grounding grid may be represented in $15{\sim}20m$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1770-1772
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• 1997

In this paper, Voltage-time characteristics of lightning impulse and switching surge breakdown in SF6 is studied on the gap and various pressure. The characteristics is categorized into three pattern depending on the configuration of the gap and gas pressure. The properties of the voltage-time characteristics in these patterns are generalized as semi-empirical formula which will be useful in the quantitation voltage evaluation of insulation coordination and the abnormal voltage protection of SF6 insulated power equipment.

• 조명전기설비학회논문지
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• 제22권1호
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• pp.50-57
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• 2008

철도 정거장 구내에서는 본선으로부터 측선으로 진로를 바꾸기 위하여, 즉 다른 선로로 분기하기 위하여 분기지점에 설치한 궤도설비를 분기기라 하며, 분기기의 방향을 전환시키는 장치를 선로전환기라 하는데, 이 장치에 문제가 발생하면 심각한 상황이 초래될 수 있다. 이 장치에는 정밀한 기기와 센서가 설치되어 사용되는데, 장애가 많이 발생하며 열차 탈선이라는 극한의 상황까지 이를 수 있다. 본 논문에서는 사용중인 안전장치들을 장애와 사고를 정밀 분석하고 이를 대체할 수 있는 장치를 개발하였다. 이 장치는 낙뢰에 의한 과전압의 영향을 받지 않도록 설계되어서 열차운행이 원활하게 된다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.546-549
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• 2004

This paper describes the electrical characteristics of the polymer lightning arresters(L.As) used to protect distribution lines and power facilities from surge. For the relative comparison, the characteristics assessment was done for 2 states of L.As before and after water immersion treatment. The L.As for the comparative test were immersed with water of $95[^{\circ}C]$ considered a severe condition. After the immersion treatment, the assessment was carried out for material analyses in chemical structure(FTIR : fourier transform infrared spectrophotometer). Electrical performance measured insulation resistance measurement, leakage current measurement, critical operation voltage measurement etc.. In addition to, the results were compared with those for the L.As deteriorated in the field. Thus, the accelerative deterioration degree of polymer materials by immersion treatment was evaluated, by which the structural defects of the polymer L.As could be inferred.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.16-21
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• 2002

Most adjustable-speed drives(ASDs) designed to operate 220[V] induction motors incorporate voltage-source inverters (VSIs), which create motor voltages at high switching frequencies. The motor leads used to connect an ASD to a motor can behave like transmission lines for voltage pulses, which can be amplified (reflected) at the motor terminals. The resulting oscillatory transient, known as the long-lead effect, can stress and consequently degrade the statorinsulation system of a motor. This Brief describes the results of tests to 1) determine the correlation between peak motor voltage and the length of motor leads and 2) determine the correlation between peak motor voltage and the switching frequency of the ASD Insulation failures like this usually are caused by voltage surges. Voltage surges are often the result of switching power circuits, lightning strikes, capacitor discharges and solid-state power devices.