• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.26-26
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• 2010

Line to ground faults or lightning strikes in electrical power systems produce high frequency overvoltages. With this reason, a wide band analysis of the ground impedance is necessary. In the paper, design of a wideband ground impedance meter which can measure the ground impedance in ranges from 65 Hz to 1.5 MHz is described. Also, a noise elimination method by a digital band-pass filter during measurement is proposed. The maximum measurement error of the meter is estimated 3 % in full ranges.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.289-292
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• 2009

This paper describes the analysis for ground impedance measurement influenced by 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[Hz], 128[Hz], 342[Hz], and 513[Hz]. The results could be help to determine the position of current probe when the ground impedance was measured at grounding system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.369-371
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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 fell-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.

• 조명전기설비학회논문지
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• 제23권6호
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• pp.78-84
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• 2009

본 논문은 토양의 방전 영역에서 소규모 접지전극의 과도접지임피던스의 측정결과를 제시한다. 접지전극 주변에서 이온화 특성을 사실적으르 분석하기 위해서 세 가지 형상의 접지전극을 실외에 설치하고, 고전압 임펄스 발생기를 사용하여 시험전류를 인가하였다. 정지전극에서 대지로 흐르는 전류와 응답 전압을 분석한 결과, 접지전극 주변의 이온화는 높은 대지저항률률의 토양에서 접지임피던스 감소에 기여하며 대지전위상승을 효과적으로 제한하는 것이 확인된다. 하지만 낮은 대지저항률의 토양에서는 이온화 임계전계강도가 작아서 전극 형상이 과도접지임피던스에 거의 영향을 주지 못한다. 그리고 전극형상에 따른 실험결과, 판전극보다 침부봉전극이 이온화 영역 전압범위 내에서 과도접지임피던스 저감에 보다 효과적이다.

• 조명전기설비학회논문지
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• 제25권4호
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• pp.97-103
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• 2011

The most important object of grounding systems is to protect human being from electric shock. Touch and step voltages are measured to evaluate the performances of grounding systems. Dangerous voltages have been largely studied by the power frequency fault currents, on the other hand, the ground current containing the high frequency components and surge currents haven't been considered. Many attempts about the grounding impedances reported in these days show that the performance of the grounding systems in high frequency range is very different with the ground resistance. It is necessary to analyze the dangerous voltages formed by the ground currents containing high frequency components. In this paper, the ground surface potential rises near the vertical and horizontal grounding electrodes are measured at the frequency of 100[Hz], 30[kHz], and 100[kHz]. Dangerous voltages are investigated with the frequency-dependent grounding impedance. As a result, the ground surface potential rise is increased as the grounding impedance increases. Touch and step voltages near the grounding electrode whose impedance increases with the frequency are sharply raised.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1248-1256
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• 2008

In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by $0.1{\sim}0.2\;dB$ than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that {\lambda}/4$ impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10 {\Omega}$, the line width and length were 20 and $500\;{\mu}m$, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.

• 조명전기설비학회논문지
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• 제19권6호
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• pp.67-74
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• 2005

접지 시스템은 전기설비의 기준 전위점을 확보할 뿐만 아니라, 대지에 낮은 저항으로 고장 전류를 흐르게 한다. 고장전류는 넓은 범위의 주파수를 포함하기 때문에 접지의 성능을 평가하기 위해선 주파수에 대한 함수로 접지임피던스에 대한 특성의 분석이 필요하다. 본 논문에서는 상용화된 접지봉(매직봉)의 접지임피던스를 0[Hz]에서 100[kHz] 범위까지 측정하였고, 접지임피던스를 회로 모델과 전달함수 모델로 구하여 측정된 값과 비교 검토하였다.

• 조명전기설비학회논문지
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• 제19권6호
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• pp.46-51
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• 2005

접지 시스템은 전기설비의 기준 전위점을 확보할 뿐만 아니라 대지에 낮은 저항으로 고장 전류를 흐르게 한다. 주파수에 대한 함수로 접지임피던스는 고장전류가 넓은 범위의 주파수를 포함하기 때문에 접지 성능을 평가하는데 필요하다. 동봉은 배전계통에서 가장 많이 쓰이는 접지 전극이다. 본 논문에서는 동봉의 접지임피던스를 주파수 60[Hz]에서 100[kHz] 범위까지 측정하였고, 접지임피던스를 회로 모델과 전달함수 모델로 구하여 측정된 값과 비교 검토하였다.

• 전기학회논문지
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• 제60권10호
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• pp.1984-1991
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• 2011

Among ground impedance measurement methods, the fall-of-potential method is the most thorough and reliable method. In the fall-of-potential method, ground electrode and auxiliary probes are placed in a straight line, and then, auxiliary potential probe is moved away from the ground electrode. The point at which plotted resistance curve flattens out is taken as right position of auxiliary potential probe. However, in some cases, it is hard to place ground electrode and auxiliary probes in a straight line. Therefore, we provided alternative placement method in this research. The method can be easily applicable to placing auxiliary probes. Also, this paper analyzed and compared ground impedance measurement standards of large grounding systems. Based on the analysis, practical measurement method using an earth tester was proposed. The proposed methods presented in this paper will be useful when determining locations of auxiliary probes in alternative positions, and the methods can be applied practically and easily.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2235-2237
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• 2005

This paper presents the transient impedance behaviors of grounding systems to lightning impulse current. The potential rise and effective impulse ground impedance of the test grounding electrodes were measured as a function of the rise time of impulse currents and lengths of down conductor. The transient ground impedances strongly depend on the configuration and size of grounding electrodes, the impulse current shapes and lengths of down conductor, and the inductance of reduce of grounding electrode inductance is an important factor to improve the transient ground impedance.