• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권8호
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• pp.426-432
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• 2004

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.

• 전기학회논문지
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• 제61권9호
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• pp.1374-1379
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• 2012

Urban rail transit tends to global grounding system in order to control ground potential rise and potential differences between electric equipments. In addition, global grounding system can discharge the large capacity surge current to the ground safely. Since some railway electric equipments are installed all section of line, the global grounding system connected with the connecting grounding wire is more effectively. However, if the fault occurred in the connecting grounding wire area, some dangerous voltage is generated. So, the installation of additional grounding rod will be required. In this study, the global grounding system is simulated using CDEGS program to analyze the divergence spacing of additional ground rod depending on dangerous electric potential characteristics. Grounding net of the each station is modelled in depending on the size of the platform, and the spacing of the connecting grounding rod are compared 50m, 100m, 250m and 400m. Simulation results considering of earth resistivity and underground condition of the connecting grounding wire, spacing of the connecting grounding rod is that less than 250m to spacing of the ground rod was appropriately confirmed.

• 조명전기설비학회논문지
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• 제23권1호
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• pp.92-99
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• 2009

심매설 접지봉의 경우 장마철에 빗물이나 지하수와 접촉하는 경우가 발생한다. 수중에 잠겨있는 접지극에 서지 전압이 인가되면 접지극 주변에서 이온화 현상이 발생하게 된다. 지중이나 수중에서의 이온화 현상은 접지 시스템의 에너지적인 특성에 의해 영향을 받는다. 이 논문의 목적은 축소된 전해 수조를 이용하여 임펄스 전압에 의한 접지시스템의 과도특성을 파악하는데 있다. 매틀랩 프로그램을 활용하여 이온화에 의한 전위저감과 방출된 에너지를 측정하여 정량적인 분석을 수행하였다. 접지극 끝단의 최대 전압은 물의 저항률과 Marx형 전압발생장치의 충전전압에 따라 다양하게 나타났다. 접지극 끝단의 전위는 절연파괴전압에 이르기 전 인가전압에서 대략 절반까지 감소하였다. 또한 절연파괴가 발생하기 전 인가된 에너지의 절반 이상의 에너지가 이온화에 의해 접지극을 통하여 방출되었다.

• 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).

• 조명전기설비학회논문지
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• 제25권12호
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• pp.107-112
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• 2011

Multiple ground rods are commonly used to obtain the low ground impedance, but they will not reduce the ground impedance unless the spacings between the ground rods are sufficient. This paper presents the experimental results of frequency-dependent resultant ground impedance of two ground rods in parallel. The resultant ground impedance of two ground rods in parallel were measured as functions of the spacing and length of ground rods and the frequency of test currents and were discussed based on the potential interferences. As a consequence, the frequency-dependent ground impedance of single ground rod and two combined ground rods give capacitive. It was found that the effect of potential interference on the ground impedance is directly associated with the frequency-dependent ground impedance and is strong in low frequency. Also, in order to reduce the increasing rate of resultant ground impedance of two ground rods due to potential interference to within 10(%), two ground rods in parallel will be placed over one rod length apart.

• 조명전기설비학회논문지
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• 제20권1호
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• pp.65-70
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• 2006

본 논문은 임펄스전류에 따른 접지시스템의 과도 특성에 관한 것으로 임펄스 전류를 심매설 봉상 접지전극과 그리드 접지전극에 인가하였을 때 나타나는 과도접지임피던스를 조사하였다. 과도접지임피던스는 인가전류의 상승시간과 접지전극의 크기 및 형태에 강하게 의존하며, 접지전극의 인덕턴스는 짧은 시간 영역에서 접지시스템의 과도 접지임피던스에 크게 영향을 미치는 것으로 나타났다. 또한 심매설 봉상접지전극은 짧은 시간영역에서 과도접지임피던스를 줄이는데 효과적이었다.

• 조명전기설비학회논문지
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• 제23권7호
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• pp.41-48
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• 2009

Grounding impedance depends on the frequency of current flowing into a grounding system lightning in particular has a broad frequency spectrum from some tens of Hz to a few MHz. So the grounding impedance related to transient currents such as lightning should be measured. In this paper, the grounding impedances of vertically-driven ground rods of 10, 30 and 48[m] long are measured and analyzed as functions of the frequency of injected current and the feeding point. As a result, the longer the ground rod is, the lower the steady-state ground resistance is. However the grounding impedance of a vertically-driven ground rod at a high frequency is significantly increased. It is not always true that low grounding impedance follows from a low steady-state ground resistance. It is important to evaluate the high frequency performance of grounding systems for protection against lightning.

• 전기학회논문지
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• 제65권9호
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• pp.1564-1570
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• 2016

This study proposes a newly modified form of existing ground electrodes in order to secure trust of grounding system for large current caused by a stroke of lightning. Proposed planar earth structure has a several needle electrodes around a circular rod and 4 plane electrodes in all directions. The plane electrodes are fused with the insulator on the linear rod, so that they're electrically isolated. The concept is to increase the discharge amount of earth structure using multiple discharge paths like needle and plane electrodes. To check the discharge efficiency of the suggested scheme, the discharge currents are compared with typically used two kinds of ground rods. To ensure accuracy in the measurement of the discharge current, the same material was used for the comparison model. Also, the ground resistance are simulated by CDEGS commercial software and the results are compared with measured data. Based on this kind of experimental study, the suggested ground rod can be used when designing a ground system or when constructing a ground system at the site.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2003년도 학술대회논문집
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• pp.369-372
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• 2003

To obtain a low ground resistance in high resistivity soil or in insufficient place such as downtown, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flows into the grounding system, the ground impedance is remarkedly increased. This paper presents how the impulse and fault current works on the long. vertical ground rods associated with incoming points. When the test current was injected at the bottom of ground rod, the potential waveform of ground rod includes the oscillation with high frequency.

• 조명전기설비학회논문지
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• 제22권10호
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• pp.62-68
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• 2008

본 논문은 임펄스전류의 인가위치에 따른 심매설 봉상 접지전극의 과도접지임피던스와 규약접지임피던스 특성에 관하여 기술하였다. 과도접지임피던스는 심매설 접지전극의 길이 및 임펄스전류의 상승시간과 인가위치에 강하게 의존하며, 접지전극의 자체 인덕턴스는 짧은 시간 영역에서 점지시스템의 과도접지임피던스에 크게 영향을 미치는 것으로 나타났다. 심매설 봉상 접지전극의 자체 인덕턴스의 저감은 과도접지임피던스 특성의 개선에 결정적인 역할을 한다. 접지도선의 길이는 최대한 짧게 하여 접지전극의 상단에 접속하는 것이 효과적이다.