• 조명전기설비학회논문지
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• 제24권12호
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• pp.164-170
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• 2010

For the surge currents like lightning or ground fault currents containing high frequency components which cause the electromagnetic interferences for the electronic devices and communication equipment, the grounding impedances give the significantly composite characteristics which are dependent on the frequency of surge currents. In this paper, the analytical model and method for determining the optimal length of the newly developed coaxial type carbon ground electrode which has a little fluctuation in grounding impedance with frequency. The length of minimizing the fluctuation of grounding impedance by changing frequency from 100[Hz] to 1[MHz] was determined, and the validity of this proposed method was confirmed by comparing with the simulated and measured data.

• 조명전기설비학회논문지
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• 제25권6호
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• pp.49-56
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• 2011

Grounding system insures a reference potential point for electric devices and also provides a low impedance path for fault currents or transient currents in the earth. The ground impedance as function of frequency is necessary for determining its performance since fault currents could contain a wide range of frequencies. In this paper, the grounding resistance, grounding impedance and transient grounding impedance are measured by using 3-point fall-of-potential method in order to analyse grounding characteristics of the copper and concrete rod grounding electrodes. An equivalent transfer function model of the ground impedance and transient grounding impedance are identified from the measured values by using ARMA method and evaluated by comparing the conventional grounding impedance.

• 조명전기설비학회논문지
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• 제24권2호
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• pp.133-141
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• 2010

접지시스템은 전기설비의 기준 전위점을 확보할 뿐만 아니라 대지에 낮은 저항으로 고장전류나 과도전류를 흐르게 한다. 주파수에 대한 함수로 접지임피던스는 고장이나 과도전류가 넓은 범위의 주파수 성분을 포함하기 때문에 접지성능을 평가하는데 중요한 역할을 한다. 동봉과 콘크리트봉은 배전계통에서 가장 많이 쓰이고 있는 접지전극이다. 본 논문에서는, 주파수영역과 시간영역의 특성시험으로 동봉과 콘크리트봉의 접지임피던스를 측정하였다. 접지임피던스의 등가 전달함수 모델은 측정된 데이터를 이용하여 ARMA 기법으로 모델링 되었고, 규약 접지임피던스로 비교하여 평가하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 추계학술대회 논문집
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• pp.47-50
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• 2009

When the lightning currents flow through the ground electrode, the grounding system should be evaluated by the grounding impedance rather than the ground resistance because a grounding system shows the transient impedance characteristic by the inductance of the ground electrode and the capacitance of the soil. The ratio of the peak values of electric potential and currents is the conventional impedance that shows the transient characteristic about impulse currents of the grounding system in a roundabout way. The grounding system having low conventional impedance is a fine grounding system with low electric potential when the lightning currents flow. In this paper the conventional impedance of the counterpoise is calculated by using the distributed parameter circuit model and embodied the distributed parameter circuit model by using the EMTP program The adequacy of the distributed parameter model is examined by comparing the simulated and the measured results. The conventional impedance of the counterpoise is analyzed for first short stroke and subsequent short stroke currents.

• 조명전기설비학회논문지
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• 제26권1호
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• pp.54-60
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• 2012

When the transient current with high frequency components such as lightning surges are injected the grounding electrodes, the performance of grounding electrodes should be evaluated as grounding impedance. It is restricted to analyze the grounding impedance by measurement approach since the grounding impedance is very different with the shape and size of grounding electrodes, resistivity and relative permittivity of soil and the frequency component of the injected current. So a variety of simulation approaches have been developed. Typically, the soil resistivity measured with low frequency and relative permittivity between 1 and 80 are used for simulation of the grounding impedance. However, the resistivity and relative permittivity of soil are changed with frequency of injected current. In this paper, the frequency-dependent resistivity and relative permittivity of soil are measured and these parameters are reflected in the simulation of the grounding impedance of a ground rod. The simulated results are compared with the measured results. As a result, the simulated results with frequency-dependent soil parameters show capacitive aspect like measured results in the frequency of lower than 100[kHz] and they are more consistent with the measured results in wide frequency range.

• 한국철도학회논문집
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• 제18권4호
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• pp.289-300
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• 2015

철도 전동 소음은 철도에서 발생하는 대표적인 소음으로서 차륜과 레일의 음향 조도에 의해 가진 된 차륜 및 레일의 진동으로부터 발생한다. 철도 전동 소음 해석 시 레일 방사 소음은 자유 공간에 놓인 레일의 음향 방사 파워를 이용해 원거리에서 계산하므로, 일반적으로 소음원 모델에 지면 반사를 고려하지 않는다. 그러나 레일 주위의 근접 음장을 해석하고 저감 대책을 적용하기 위해서는 지면에 의한 음파의 반사를 고려해야 한다. 본 논문에서는 파수유한요소/경계요소법을 이용해 지면에 의해 발생하는 레일 소음의 변화와 그 특성을 살펴보았다. 해석은 먼저 레일이 강체 지면에 부착된 경우와 레일 패드 높이만큼 강체 지면에서 이격된 경우에 대해 방사효율을 구하고 그 결과를 비교하였다. 이를 통해 레일과 강체 지면의 이격 여부에 따라 레일 방사 소음에 크게 변화함을 확인하였다. 둘째로는 지면에 임피던스 경계조건을 부여하고 레일에서 방사되는 음향 파워 및 지향 특성의 변화를 살펴보았다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1348-1349
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• 2008

Grounding impedance depends on the frequency of current flowing into a grounding system. Especially, the lightning gives a broad frequency spectrum from low frequency up to 1 MHz. So the grounding impedance related to high frequency current like lightning should be measured with high frequency source. In this paper, we described the grounding impedances of deeply-driven ground rods of 10 $\sim$ 48 m long with respect to the frequency of injected currents. For the experiments, we used the wideband power amplifier which can produce sinusoidal voltages with the frequency ranges of DC $\sim$ 250 MHz. As a result, the longer the ground rod is, the lower the ground resistance is. However the grounding impedance of deeply-driven ground rod in the range of higher frequency is significantly increased. As a consequence, it is important to evaluate the high frequency performance of grounding systems for lightning protection.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.70-73
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• 2008

Grounding impedance depends on the frequency of current flowing into a grounding system. Especially, the lightning gives a broad frequency spectrum from low frequency up to 1 MHz. So the grounding impedance related to high frequency current like lightning should be measured with high frequency source. In this paper, we described the grounding impedances of deeply-driven ground rods of 10 ${\sim}$ 48 m long with respect to the frequency of injected currents and the feed point. For the experiments, we used the wideband power amplifier which can produce sinusoidal voltages with the frequency ranges of DC ${\sim}$ 250 MHz. As a result, the longer the ground rod is, the lower the ground resistance is. However the grounding impedance of deeply-driven ground rod in the range of higher frequency is significantly increased. As a consequence, it is important to evaluate the high frequency performance of grounding systems for lightning protection.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.88-91
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• 2009

For lightning currents, a grounding system shows the transient grounding impedance characteristics. A grounding system for protection against lightning should be evaluated by the transient grounding impedance, not it's ground resistance. The transient grounding impedance varies with the shape of ground electrode and earth characteristics as well as the waveform of lightning surge current. For the analysis and practical use of transient grounding impedance, the characteristics of transient grounding impedance should be analyzed theoretically and this paper suggests the theoretical analysis for the transient grounding impedance of counterpoise by using the distributed parameter circuit model. EMTP and Matlab are used to simulate the distributed parameter circuit model of counterpoise and the adequacy of the distributed parameter model of counterpoise is examined by comparing the simulated results with the measured results.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.367-370
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• 2008

In this paper, the effects of the position and the angle of the auxiliary probes on the measurements of the low frequency ground impedance with the fall-of-potential method are described iud the testing techniques to minimize the measuring errors are proposed. The fall-of-pot ential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position and angle of auxiliary probes. In order to analyze the characteristics of ground impedance due to the location of the potential probe, ground impedances were measured in case that the distance of current probe was fixed at 50[m] and the distance of potential probe was located from 10[m] to 50[m]. Also, the potential robe was located at 30[$^{\circ}$], 40[$^{\circ}$], 60[$^{\circ}$], 90[$^{\circ}$], and 180[$^{\circ}$]. The results could be help to determine the location of potential probe when the ground impedance was measured at grounding system.