• 조명전기설비학회논문지
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• 제24권5호
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• pp.37-43
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• 2010

넓은 범위의 주파수 스펙트럼을 포함하고 있는 낙뢰나 전력변환 기기들을 고려할 때 접지시스템의 성능은 접지임피던스에 의해 평가되어야 한다. 본 논문은 실규모의 수직 접지전극과 매설지선에 대한 접지임피던스의 주파수 의존성에 대한 측정결과를 나타낸다. 수직 접지전극과 매설지선의 접지임피던스는 접지전극의 길이와 토양의 대지저항률에 따라 용량성 또는 유도성 특성을 나타내었으며, 단순히 접지저항을 낮추기 위해 접지전극의 길이를 증가시키는 것은 비효율적이며 접지임피던스를 고려한 접지설계가 요구된다. 또한 매설지선의 접지임피던스를 저감시키기 위해 접지도선은 매설지선의 중앙에 접속되어야 하며, 봉상 접지전극을 매설지선과 병렬로 설치하는 것이 접지임피던스의 저감에 효과적인 것으로 나타났다.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 2002년도 추계 학술논문발표회 논문집
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• pp.281-285
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• 2002

Although DC ground resistance is a good index of performance for a grounding system, it does not reflect the grounding performance during the transient states. Besides, impulse ground impedance, which is defined by a ratio of the peak value of transient ground potential rise to the peak value of impulse current, cannot be an absolute performance index due to its dependence on impulse current shape. In this paper, a grounding performance of needle-typed ground rod has been compared with simple ground rod using HIFREQ[1], which is an engineering electro-magnetic code based on MoM (Method of Moment).

• 전기학회논문지
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• 제56권6호
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• pp.1099-1104
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• 2007

A 1:6 Unequal 2-way Wilkinson power divider is proposed. The required microstrip line with $207{\Omega}$ characteristic impedance for 1:6 power divider is realized by adding defected ground structure (DGS) to the standard microstrip line. The adopted DGS has the rectangular geometry which results in the increased characteristic impedance. The rectangular-shaped DGS produces the transmission line having much higher characteristic impedance due to the increased equivalent inductance. The measured performances of the fabricated 1:6 power divider show the expected S-parameters with a good agreement with the predicted ones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.619-621
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• 2004

This paper presents the rapid and accurate algorithm for fault discrimination in transmission lines. When faults occur in transmission lines, fault discrimination is very important. If high impedance faults occur in transmission lines, it cannot be detected by overcurrent relays. The method using current and voltage cannot discriminate high impedance fault. Because of this reason this paper uses voltage and zero sequence current, and the proposed algorithm uses fuzzy logic method. This algorithm uses voltage and zero sequence current per period in case of faults. Single line ground fault and three-phase fault can be detective using voltage. Two-line ground fault and line to line fault and high impedance can be detected using zero sequence current. To prove the performance of the algorithm, it test algorithm with signal obtained from ATPDraw simulation.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.417-422
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• 2005

Using the novel microstripline with periodically perforated ground metal, a miniaturized 1/4 ${\lambda}$ transformer was fabricated. The line width of the 1/4 ${\lambda}$ transformer was 20${\mu}m$ and the size of it was 0.0085$mm^2$, which is 1.2% of conventional one. The 1/4 ${\lambda}$ transformer exhibited good RF performances from 10 to 25GHz.

• Journal of electromagnetic engineering and science
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• 제11권3호
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• pp.192-200
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• 2011

This paper proposes a new modeling method for estimating the impedance of an on-chip power/ground meshed plane. Frequency dependent R, L, and C parameters are extracted based on the proposed method so that the model can be applied from DC to high frequencies. The meshed plane model is composed of two parts: coplanar multi strip (CMS) and conductor-backed CMS. The conformal mapping technique and the scaled conductivity concept are used for accurate modeling of the CMS. The developed microstrip approach is applied to model the conductor-backed CMS. The proposed modeling method has been successfully verified by comparing the impedance of RLC circuit based on extracted parameters and the simulated impedance using a 3D-field solver.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1487_1488
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• 2009

In these days, the common grounding systems are adapted in most large structures. In order to evaluate the performance of grounding system, it is needed to measure ground impedance. Measuring methods of ground impedance for a large scale grounding systems have not been yet presented in detail. In this paper, we analyze earth mutual resistance and mutual coupling of $15{\times}15m$ grounding grid in different arrangements of auxiliary electrode. As a results, the auxiliary electrodes are installed where the error rate due to earth mutual resistance is less than 5%. Also, the potential lead is installed at obtuse angle from the current lead and the overlapped length between potential lead and grounding grid are minimized.

• Corrosion Science and Technology
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• 제16권6호
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• pp.298-304
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• 2017

Coil spring steels from the automobile suspension part after field exposure for 10 years and those after anti-corrosion validation test in proving ground of 5,000 ~ 10,000 km were examined for corrosion damages. Partial loss of paint, accumulation of corrosion product, and cracking of paint and superficial material were observed. The surface and subsurface region of spring steels had compressive residual stress and high hardness by shot peening. The surface hardness values of the specimens were 620 ~ 670 Hv. They were 60 ~ 80 Hv higher than those of the samples taken from the middle part of the spring. The maximum compressive stress was -916 ~ -1208 MPa measured at depth of about $100{\mu}m$. Electrochemical impedance spectroscopy showed that the resistances of charge transfer and the paint layer of the spring steels ranged from several tens to millions ${\Omega}{\cdot}cm^2$. The resistance of the field samples was much higher than that of the proving ground samples used in this study, implying that the proving ground test condition would be more corrosive than the field environment.

• 전기학회논문지
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• 제59권6호
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• pp.1103-1108
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• 2010

A grounding electrode has the transient grounding impedance characteristics against lightning surges. So the performance of grounding electrodes should be evaluated as a grounding impedance as well as the ground resistance. The frequency-dependent grounding impedance is varied with the shape and size of grounding electrode and is divided into both inductive and capacitive behaviors. This paper presents a theoretical analysis for the grounding impedance determined by the size of grounding electrode using the distributed parameter circuit model. EMTP and Matlab programs were used in calculating the frequency-dependent grounding impedances of vertical grounding electrodes. It was found that the frequency-dependent grounding characteristics of vertical grounding electrodes are characterized by the distributed parameters which are changed in the dimension of grounding electrodes.

• 전기학회논문지P
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• 제61권3호
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• pp.149-152
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• 2012

In this paper, a wideband monopole antenna with ring loop by modified ground plane is presented. The proposed antenna consist of monopole antenna, ring loop by ground plane. This antenna is fed CPW-fed and wide slot antenna of a novel structure for broadband characteristics is proposed. To enhance the impedance bandwidth of the wide slot antenna, we proposed the wide slot structure with CPW-fed which is combined with four ${\lambda}/2$ rectangular radiation modified monopole and inductively coupled. The measured impedance bandwidth is about 2.5 GHz(3.65~6.15 GHz) then less -10 dB.