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불균등 분포정수회로모델을 이용한 접지그리드의 접지임피던스 모의
최종혁(Jong-Hyuk Choi),성창훈(Chang-Hoon Sung),이복희(Bok-Hee Lee),안창환(Chang-Hwan Ann) 한국조명·전기설비학회 2011 한국조명·전기설비학회 학술대회논문집 Vol.2011 No.11
This paper describes the simulation method of the ground grid using non-uniform distributed circuit parameter model. In this simulation method, the ground grid is divided into small segments and the resistive, capacitive, and inductive couplings between those segments are considered as if the segments are assumed like thin wires. The distributed circuit parameters are calculated by Matlab program and the circuit model is implemented by EMTP program. The simulated results of frequency-dependent grounding impedance of the ground grid is good agrement with the measured results and the data simulated by electromagnetic field theory.
수분의 저항률과 함유량에 따른 모래의 저항률과 비유전율의 주파수의존성
정윤석(Yun-Seok Jung),최종혁(Jong-Hyuk Choi),이규선(Kyu-Sun Lee),이복희(Bok-Hee Lee),안창환(Chang-hwan Ann) 한국조명·전기설비학회 2010 한국조명·전기설비학회 학술대회논문집 Vol.2010 No.5월
Grounding impedance is dependent on the resistivity and relative dielectric constant of the soil around the grounding electrode. Some researches give the frequency-dependent resistivity and relative dielectric constant of soil, In this paper, the frequency-dependent resistivity and relative dielectric constant of the sand as functions of the resistivity and content of water. As a result, the soil resistivities are independent of the frequency in the range of lower than 1㎒ and sharply decrease over higher than 1㎒. Also the relative dielectric constant is sharply decreased in the range of lower than 100㎑ and it is irrespective to the content and resistivity of water.
이복희(Bok-Hee Lee),이승훈(Seung Hoon Lee),최종혁(Jong-Hyuk Choi),김태기(Tae Ki Kim),안창환(Chang-hwan Ann) 한국조명·전기설비학회 2010 한국조명·전기설비학회 학술대회논문집 Vol.2010 No.9월
Ground resistance is determined by the shape of grounding electrode and soil resistivity near the buried ground rod. The soil resistivity is practically measured by Wenner four-point method or three-point method measuring the ground resistance of the driven test rod. In this paper, the measurement accuracy of soil resistivity and the relation between the test electrode spacing in four-point method and the length of the driven test rod in three-point method are evaluated. The results obtained from both measuring methods are dependent with the soil structure and measuring conditions. The soil resistivity measured with a specified length of the driven rod in three-point method was in agreement with the result measured with a specified electrode spacing in Wenner four-point method.
모래의 수분함유량에 따른 비저항 및 비유전율의 주파수 의존성
이복희(Bok-Hee Lee),차응석(Eung-Suk Cha),최종혁(Jong-Hyuk Choi),최영철(Young-Chul Choi),유양우(Yang-Woo Yoo),안창환(Chang-Hwan Ann) 한국조명·전기설비학회 2009 한국조명·전기설비학회 학술대회논문집 Vol.2009 No.5월
In order to evaluate the performance of a grounding system against lightning or fault currents including high frequency components, the grounding impedance should be considered rather than its ground resistance. Recently, some researches on the evaluation and modeling of the grounding impedances have been carried out, but the results have not been yet sufficient. This paper deals with the frequency dependence of the resistivity and relative dielectric constant of sand associated with water contents. As a result, the resistivity of sand is getting lower with increasing water content, and it is nearly independent on the frequency in the range of less than 1㎒, and is decreased over the frequency range of above 1㎒. Also, the relative dielectric constant is rapidly decreased with the frequency in the range of less than 10㎑, but it is nearly not dependent on the frequency over the frequency range of 10㎑. It was found from this work that the frequency dependance of resistivity and relative dielectric constant of soil should be considered in designing the grounding systems for protection against lightning or surges.