논단 2-전자기기의 뇌써-지 대책

이복희,Lee, Bok-Hui 한국전기산업진흥회 1996 電氣産業 Vol.7 No.1

여대생의 진로결정 변인에 관한 연구

이복희 백석대학교 유관순연구소 2008 유관순 연구 Vol.13 No.-

다중 낙뢰에 의해서 발생한 전장 파형의 특성

이복희,정동철,이동문 대한전기학회 2004 전기학회논문지C Vol.53 No.6(C)

In this work, in order to obtain the detailed information about lightning electromagnetic pulses, the electric fields radiated from multiple lightning return strokes were measured and analyzed statistically. The electric field measuring system consists of a hemisphere antenna of 30 ㎝ in diameter, integrator and data acquisition device, and its frequency bandwidth ranges from 200 ㎐ to 1.56 ㎒, and the sensitivity is 0.96 ㎷/V/m. The electric field signals are digitized every 200 ns with the transient signal analyzer having the resolution of 12-bit and the recording length of 5 kilowords and are registered at personal computer. As a result, the electric fields produced by the first return stroke begin with a slow initial part or front, which starts just after or during the last stepped leader. On the average the rise times of the electric fields for the positive first, second and third strokes are 4.21 ㎲, 3.94 ㎲ and 2.75 ㎲, respectively, and those for the negative first, second and third strokes are 3.46 ㎲, 3.15 ㎲ and 2.79 ㎲, respectively. The zero-crossing times of the electric fields for first return strokes range from about 10 to 80 ㎲. The mean zero-crossing times for subsequent return strokes are shorter than those for first lightning return strokes.

낙뢰에 의해 방사된 전계와 자계 파형의 파라미터

이복희,백영환,이우철,Lee, Bok-Hee,Baek, Young-Hwan,Lee, Woo-Chul 한국조명전기설비학회 2006 조명·전기설비학회논문지 Vol.20 No.5

본 논문은 낙뢰에 의해서 방사된 전계와 자계 파형의 물리적 특성과 파라미터분석에 대한 것으로 낙뢰에 의한 전계와 자계 파형은 각각 평판형 전계센서와 루프형 자계센서로 검출되고, 측정된 신호는 12 비트의 해상도, 10[MS/s] 샘플링, 10[ms]의 기록시간을 가지는 데이터취득시스템으로 기록하였다. 낙뢰에 의해 발생한 전계와 자계 파형의 극성의존성은 거의 없었으며, 상승시간은 $13[{\mu}s]$이내이고 정 부극성의 평균값은 각각 $4.1[{\mu}s],\;4.2[{\mu}s]$이었다. 정 부각성의 영점교차시간은 각각 $65.2[{\mu}s],\;67.0[{\mu}s]$이고, 반전딥의 깊이는 38.0[%], 40.3[%]이었다. This paper deals with the physical properties and statistical analysis of waveform parameters of electric and magnetic folds radiated from lightning return strokes. The lightning electric and magnetic fields were detected by an plate-type electric field sensor and a loop-type magnetic field sensor respectively, and they were recorded by a data acquisition system having a resolution of 12bits, a sampling rate of 10[MS/s] and recording length of 10[ms]. As a result, a little difference between the parameters of electric and magnetic fields for positive and negative polarities was observed. The rise times of electric and magnetic fields were within the range of less than $13[{\mu}s]$ and the average values for positive and negative polarities were $4.1[{\mu}s]\;and\;4.2[{\mu}s]$, respectively. The average values of the zero-to zero crossing times were $65.2[{\mu}s]\;and\;67.0[{\mu}s]$, and the average depths of the dip to opposite polarity were 38.0[%] and 40.3[%], for positive and negative polarities, respectively.

가변주파수 인버터를 이용한 접지임피던스의 새로운 측정기법

이복희,엄주홍 대한전기학회 2004 전기학회논문지C Vol.53 No.5(C)

In order to analyze the frequency dependance of ground impedance in grounding grids for lightning and surge protection, a novel method for measuring the ground impedance as a function of frequency were experimentally investigated. The experiments were carried out in rectangular grounding grids with 6×8 conductors of 22 mm2 buried at a depth of 0.5 m. The test current was injected by the variable frequency inverter whose frequency is linearly controlled for the established period in the range of 5~500 kHz. The amplitude and phase of ground impedance were calculated from the waveforms of the test current and ground potential rise measured by the band-pass filter tuned in a specific frequency. The frequency dependence of ground impedance was mainly caused by the inductive current flowing through grounding conductors over the frequency of 100 kHz. The proposed measurement method of ground impedance would be applicable to evaluate the transient response characteristics in lightning protection grounding systems.

운방전에 의해 발생되는 자장의 계측과 통계적 분석

이복희,길형준,조성철,심응보,우정욱 대한전기학회 2005 전기학회논문지C Vol.54 No.6(C)

In this work, to obtain the detailed information about lightning electromagnetic field waveforms, the LabVIEW based-measurement system of time-changing magnetic fields was designed and constructed. The frequency bandwidth of the magnetic field measuring system ranges from 300 [Hz] to 1 [MHz], and the response sensitivity is 2.78 [mV/nT]. Data acquisition system with the resolution of 12 bits and memory capacity of 32 [Mbyte] was triggered by the magnetic field to be measured. The properties and parameters of the magnetic fields produced by cloud discharges were statistically investigated. The magnetic field waveforms radiated from cloud lightning discharges tend to be bipolar, with two or more narrow and several pulses superimposed on the initial front part. The recording length of the magnetic field measurement system is about 10 [ms]. The mean duration of cloud discharges is 1.3 [ms], and the number of outburst pulses for the period is 8 in average. The front times of the magnetic fields are 6.15 [㎲] in average. The the zero-to-zero crossing times that is the initial half-cycle duration is widely dispersed and the mean value is 9.61 [㎲], and the mean value of percentage depth of dip to opposite polarity is 41.1 [%].

직류와 60 Hz 교류가 중첩된 전압에 대한 산화아연 피뢰기 소자의 누설전류 특성

이복희,강성만,박건영 대한전기학회 2005 전기학회논문지C Vol.54 No.1(C)

This paper presents the characteristics of leakage currents flowing through ZinC Oxide(ZnO) surge arrester blocks under mixed direct and 60 ㎐ alternating voltages. A mixed voltage, in which an alternating voltage is superimposed upon a direct voltage, appears on the HVDC system network. The mixed direct and alternating voltage generator with a peak open-circuit of 10 ㎸ was designed and fabricated. The leakage currents and V-I curves for the fine and used ZnO surge arrester blocks were measured as a function of the voltage ratio k, where the voltage ratio k is defined as the ratio of the peak of alternating voltage to the peak of the mixed voltages. The resistive component in the leakage current in the low conduction region is significantly increased with increasing the voltage ratio k. The V-I characteristic curves for the mixed voltages lies between the direct and alternating characteristics, and the cross-over phenomenon in the high conduction region was appeared.

가정용 전기기구의 효과적인 뇌서지 보호기법

이복희,강성만,엄주홍,이수봉,길형준,구본완,안창환 대한전기학회 2004 전기학회논문지C Vol.53 No.3(C)

This paper deals with the effective protection method for the household electric appliances against lightning surges invading from the power lines. Direct or induced lightning is the main cause of the breakdown of household electric appliance. The most effective protection method is to install SPDs(surge protective devices) at household electric appliances. If SPDs were not installed at most household electric appliances, it is necessary to install SPDs on the mains. Therefore the propagation aspect and protection methods of lighting surges coming into household electric appliances through the mains was experimentally investigated. The in actual-sized test circuits results of protection method for 8 household electric appliances including computer monitors and TV set could be summarized as follows: The breakdown characteristics of household electric appliances from lightning surges were significantly changed with the their input impedance. Namely, the types of input impedance are classified into infinite, resistive or inductive impedances. Especially, the monitor for computer with inductive input impedance from lightning surges was relatively weak against lightning surges. It was confirmed that the self inductance of branch circuits on the mains have protection effect for household electric appliances against lightning surges invading from the power lines. Also the varistors installed at cabinet panel or circuit-breaker were more effective than multi-tap outlet with varistors. When installed varistors in cabinet panel and multi-tap outlet together, the surge protection effect is much more excellent in technical and economical aspects.

봉상접지전극의 접지임피던스의 주파수의존성의 분석

이복희,엄주홍 대한전기학회 2004 전기학회논문지C Vol.53 No.8(C)

This paper presents a systematic approach of measurement, modeling and analysis of grounding system impedance in the field of lightning protection system and intelligent power equipments. The measurement and analysis system of ground impedance is based on a computer aided technique. The magnitude and phase of ground impedance were determined by the novel measurement and analysis using the revised fall-of-potential method. The ground impedances of the ground rod of 50 m long are considerably dependent on the frequency. The ground impedance is mainly resistive in the frequency range of 3-20 kHz. At higher frequencies, the reactive components of the ground impedances are no longer negligible and the inductance of the ground rod was found to be the core factor deciding the ground impedance. Although the steady-state ground resistance of the ground rod of 50 m was less than that of the ground rod of 10 m, the ground impedances of the ground rod of 50 m over the frequency range of more than 60 kHz were much greater than those of the ground rod of 10 m. Furthermore, the equivalent circuit model based on the measured data was proposed, and the calculated results were in approximately agreement with the measured data.

Ranking Forward-Looking Centers and Discourse structure

이복희 한국영미어문학회 2002 영미어문학 Vol.- No.66