• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.193-200
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• 2003

The use of underground transmission tables has continuously increased in densely inhabited urban and suburban area. Due to a increasing demand of underground cables, two or more circuits are installed in parallel for several kilometers. It, however, has not been realized that the sheath circulating current is generated in the system where a large number of cables are laid in the same route. In this paper, Author studied diversely the sheath circulating current on underground cables depending on the various length rate, the phase arrangement, and the grounding resistance of the sheath in the cross-bonded section. It was clear that very large circulating current is generated in cable systems due to unbalanced length rate and phase arrangement in the cross-bonded section.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1849-1851
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• 2003

To obtain a low ground resistance in high resistivity soil, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flow into the grounding system, the ground impedance is significantly increased because of the inductive behavior. This paper presents how the impulse current works on the long vertical ground electrodes. The different shape of current was impressed between ground rods and auxiliary electrode by using impulse generator and the ground impedance was calculated from the ground potential rise.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.66-72
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• 2004

본 연구는 접지저감제의 성분으로 수용성 고분자의 유기물과 층상형 점토의 무기재료를 주재료하여 새롭게 개발한 새로운 형태의 접지저감제의 성능비교에 관한 것이다. 신개발의 접지저감제는 수분을 흡습하여 수분에 용해된 수용성고분자가 수분과 함께 층상형점토의 층으로 삽입되어 접지저감 성능을 발휘하게 된다. 본 연구의 유 무기 복합재료형 접지저감제는 함수율과 팽창률이 매우 우수할 뿐 아니라 300wt%의 수분을 공급 후 측정한 전기전도도도 매우 뛰어나다. 또한 환경친화적인 천연재료들이므로 인체나 환경에 매우 안전하며, 접지전극의 부식과 전식을 방지하는 기능이 매우 뛰어나 염해나 화학적으로 부식성이 높은 토양에서 큰 장점을 갖는다. 본 논문에서는 신개발의 접지저감제와 기존의 여러 접지저감의 성능을 비교 분석하였다. 이를 위해 현장의 대지저항율을 측정 분석하여 각각의 접지저감제의 접지설계에 적용하여 시뮬레이션하였으며, 시뮬레이션 결과와 현장에서 실제 시공한 측정 결과와 비교 분석하였다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.37-45
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• 2007

Recently, there has been an increase of the use of ground system for lightning protection called deeply driven grounding electrode. In the case of deeply driven grounding electrode, the rod electrode is equipped perpendicularly and deeply, therefore, it has a benefit to have less restriction of place compared to mesh grid electrode. However, ground impedance is largely changed by the local earth resistivity, so it requires a detailed analysis of the ground structure when planning. The measurement of earth resistivity by existing Wenner's method has been widely used, however, this method can not find out a change in the local ground resistance and it shows the result outwardly to be difficult to estimate exact depth. Therefore, this study analyzed the ground structure as 2-D image using 96 channels measurement facility and tried to analyze change in the local ground resistance and depth of the ground in order to design a deeply driven electrode effectively for lightning protection. It used Wenner alpha method dipole-dipole method and Schlumberger method for 2-D image analysis of the ground resistivity ma based on, it the result was compared with the ground structure analyzed with the result using the CDEGS and Wenner 1-D method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.169-173
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• 2015

This study is to predict the life exponent by measuring, over 7 years, the insulation resistance of high-voltage cables in 22 kV operation for 13 years. We found out the lifetime index in order to determine the time-dependent trend of deteriorating performance of power cables. The insulation resistances decreased according to elapsed time. We found that: the initial measurements of the cable systems were in agreement with the deterioration properties of the Arrhenius Law. By analyzing the life curve of the cable system, we also verified that the value of the life exponent (n) in the v-t characteristics defined by Weibull distribution has values from 10 to 11. When designing the cable system, the initial value of life exponent was chosen as 9 without any grounding. We have verified that the theoretical grounding based on the design safety of n=9 was actually the best one available. In the short term, we apply our research result to the diagnosis and evaluation of the power cables. In the long run, however, we plan to reduce the cost of the installation and management of cable systems in operation at power stations.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.259-262
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• 2005

Ground resistance measurement is an elementary technique for the evaluation of grounding system. There are main environmental factors to consider for correct measurement but the problem is that it is practically most cases to measure ground resistance unable to know the factors. This paper presents a methodology toward true value of resistance in the unknown circumstances, utilizing the defined term 'variation rate' of potential difference curve appearing in the distance to a current probe as in the three point fall-of-potential method which comprises the characteristics of environmental factors. This methodology is a induced result from the previous demostrated studies.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.336-337
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• 2011

접지시스템 구축의 근본 목적은 인체의 안전(Safety)과 설비의 안정(Stability)을 목적으로 하며, 보호목적에 따라 전력설비용 접지와 약전용 접지로 크게 나눌 수 있다. 전력설비용접지(Frame Earth)는 감전이나 설비의 피해를 방지하기 위한 것으로서 주로 보안용접지에 속하며 평상시에는 접지선에 전류가 흐르지 않는 것이 일반적이다. 이에 반하여 약전용접지(Signal Earth)는 전자통신 회로의 안정된 동작을 확보하기 위한 것으로 평상시에도 전류가 흐르는 것이 일반적이다. 이와 같이 접지시스템은 인축의 안전과 설비의 안정적 가동확보를 위해 대단히 중요한 설비이며, 특히 전력설비용 접지의 목적은 대지면의 국부적 전위상승에 따른 인체의 감전사고방지와 1선지락사고시 전위상승억제 및 보호계전기의 확실한 동작을 도모하기 위하여 실시한다. 본 연구에서는 2011. 10월 준공예정인 시화조력발전소의 전력설비용 접지시스템을 대상으로 IEEE에서 제시하는 목표접지저항값 유지여부를 평가하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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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.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1489_1490
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• 2009

Ground impedance is changed according to frequency of the current injected into the grounding system. Because the lightning surge gives a broad frequency spectrum from some ten Hz to a few MHz, frequency dependance of ground impedance must be evaluated. In this paper, we have constructed 10m, 30m, 50m counterpoise and evaluated frequency dependance of ground impedance. Also we have evaluated frequency dependance of ground impedance according to current injection point. As a result, long counterpoises have low ground resistance, but ground impedances of those are significantly increased in the range of high frequency. In the case that currents are injected into the center of counterpoise, the ground impedance is most lower than any other injection point. Also, additory ground rod of 1.8m long affect ground impedance decrease.