• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.73-80
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• 2010

The grounding impedance is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode which shows the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical Length. In this paper, a new distributed parameter circuit model considering the condition of the multi-layered soil structures was proposed, and the grounding impedance and critical length of the vertical grounding electrode were analyzed by using the newly proposed simulation model and the MATLAB program. As a consequence, it was found that the effect of the soil structure on the frequency-dependent grounding impedance and critical length of the vertical grounding electrode is significant. It is desirable to consider the soil structure in optimal design of the grounding system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1572-1573
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• 2011

접지 저항을 줄이기 위해서 접지전극을 병렬로 시공할 경우 보다 쉽게 원하는 접지저항을 얻을 수 있다. 그러나 근접된 접지전극이 병렬로 매설되어 있을 경우 전위간섭의 영향으로 인해 합성 접지저항은 크게 감소하지 않는다. 현재의 전위간섭을 고려한 병렬접지전극의 합성 접지저항 및 합성 접지임피던스에 관한 연구는 많이 이루어지지 않았다. 본 논문에서 수직 접지전극을 정4각배열로 매설하였을 경우에 모의해석 방법을 제안하였으며 그 정확도를 평가하기 위해 실측값과 비교하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.231-231
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• 2011

바늘침 전극을 사용한 대기압 플라즈마 제트의 전기적 특성을 조사하였다. 접지 전극 위치, 안정 커패시터 크기 등 변수에 따라서 플라즈마 제트 방전 특성의 변화를 조사한다. 각 실험조건의 등가회로를 통해서, 플라즈마 방전 특성(IV-curve)을 분석한다. 등가회로에서 안정 커패시터 Cp, 유리관 내부 플라즈마 저항 RP, 접지측 유리층 커패시턴스 CG, 대기 접지 RA, 등의 각 변수들을 검토한다. Rp 및 Rj는 방전이 강해질수록 작아진다. 특히 타운젠트 방전 후 Rp 및 Rj는 약 수십 $k{\Omega}$으로 작아진다, 회로 전체 임피던스와 비교하면 아주 작은 값이다. 안정 커패시터 와 접지 측 유리 층의 임피던스는 수백 $k{\Omega}$으로 아주 크다. 방전이 진행되면서 플라즈마 저항 Rp 및 Rj가 급감하여도 Cp 및 CG의 역할로 회로전체 임피던스가 일정한 값을 유지할 수 있어서 전류가 급증 하는 것을 방지할 수 있다. 대기 접지 RA는 $M{\Omega}$으로, 접지 전극이 없을 때 방전 개시전압도 높아진다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.122-128
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• 2010

This paper presents the characteristics for ground impedance of combined three rods according to distance of current probe and frequency using the fall-of-potential method and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position of auxiliary probes. In order to analyze the effects of ground impedance due to the distance of the current probe and frequency, ground impedances were measured in case that the distance of current probe was located from 5[m] to 20[m] and the measuring frequency was ranged in 55~513[Hz]. The results could be help to determine the position of current probe and the measuring frequency when the ground impedance was measured at grounding system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.181-187
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• 2004

With the proliferation of nonlinear loads, high neutral harmonic currents in three-phase four-wire distribution system have been observed. It has been known that the ground impedance has an effect on the neutral currents of a system which operates with harmonics present. On-site measurements of harmonic currents and voltages according to the fall-of-potential method under case study system were made and the ground impedance modeling using the pattern search method for the harmonic analysis was developed The ground impedance model obtained by the proposed method was compared with the frequency characteristics by field tests and has shown appropriate results, and would be applicable to evaluate the harmonic and transient response characteristics of the ground system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.86-92
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• 2009

In order to minimize ac mutual coupling, the auxiliary electrode are located at a right angle in measuring ground impedance. In case that the measurement space is limited, the alternative method is employed. At that time, it is necessary to investigate the measurement errors due to ac mutual coupling and earth mutual resistance in measuring the ground impedances. 'This paper presents the measurement accuracy according to the location of the current and potential auxiliary electrodes in measuring ground impedance of vertically or horizontally buried ground electrode. The measurement errors due to ac mutual coupling were evaluated Consequently, the effect of ac mutual coupling on the measurement accuracy for horizontally buried ground electrode is greater than that for vertically buried ground electrode. Measurement errors due to ac mutual coupling is the largest when the current and potential auxiliary electrodes are located in parallel. The 61.8[%] rule is inappropriate in measuring ground measurement. Theoretically, in case that the angle between the current and potential auxiliary electrodes is 90$[^{\circ}]$, there is no ac mutual coupling. If it is not possible to route the current and potential auxiliary electrodes at a right angle with limitation of measurement space, the location of these electrodes with an obtuse angle is preferred to that with an acute angle in reducing the measurement errors due to ac mutual coupling.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.245-251
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• 2013

An impedance of ground electrode for information and communication facilities has a significant relationship with the electrical characteristics of soil where the ground electrode is buried. Especially, the impedance of ground electrode is directly affected by the characteristics of permittivity and conductivity in soil as a function of a frequency of an applied electric field. The program based on the electromagnetic field model was developed in MATLAB. Because both permittivity and conductivity can not be modified in commercial programs. The permittivity of soil was applied with the Debye equation which is a model of dielectric relaxation. And the empirical equation of the conductivity in soil was quoted in other paper. In order to confirm the reliability of proposed program, the impedance measurement of ground electrode was carried out, which were compared with the results of simulation in commercial program. In result, it was confirmed that the impedance and phase different simulated by appling the characteristics of permittivity and conductivity in soil are in good agreement with the measured values than results of NEC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.9
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• pp.67-74
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• 2009

For the surge currents like lightning currents containing high frequency components and the abnormal currents having high frequencies which cause the EMI(Electromagnetic interference) problems for the electronic devices and communication instruments, the linear grounding electrodes have the significantly composite impedance characteristics which are dependent on the frequency of the applied current. The impedance of a grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode having the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertically and horizontally-buried grounding electrodes are calculated by using the distributed parameter circuit model. The propriety of the simulations has been confirmed by comparing the simulated results with the measured results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.146-153
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• 2009

Recently, the common grounding systems are adapted in most large structures. Since the ground resistance is insufficient to evaluate the performance of grounding systems, it is needed to measure grounding impedance. Even though the methods of measuring grounding impedance of large grounding systems are presented in IEEE standard 81.2, but they have not been described in detail. In this paper, we present the accurate method of measuring grounding impedance based on the revised fall-of-potential method and measurement errors due to earth mutual resistance and ac mutual coupling depending on locating test electrodes at remote earth were examined for the 15[m]$\times$15[m] grounding grid. As a result, the measurement error due to earth mutual resistance is decreased when the distance to auxiliary electrodes increased. To get rid of measurement errors due to mutual coupling, the potential lead should be installed at a right angle to the current lead. When the angle between the potential and the current leads is an acute angle or an obtuse angle, the mutual couple voltage is positive or negative, respectively. Generally, the measurement errors due to mutual coupling with an obtuse angle route are lower than those with an acute angle route.

• JOURNAL OF ELECTRICAL WORLD
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• no.9 s.105
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• pp.92-95
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• 1985

OA기기에서의 접지기술은 어디라든지 그랜드라는 용어를 목적에 따라 구분, 사용하거나 포함하고 있는데 기본적인 목적은 네가지의 경우로 대별된다. 즉 (1)안전면에서 본 감전방지 (2)전자회로에서의 전자방해의 억제는 임피던스를 가진 접지이며 본질적인 문제는 여기에 있다. 한편 OA기기를 설치하는 환경은 대지 접지를 할 수 없는 케이스가 증가되고 있으며 EH 다른 문제가 부상되고 있다. 이같은 시점에서 OA기기에서의 접지기술의 현상과 문제점의 일단을 설명한다.