접지침봉에 의한 접지임피던스를 낮추는 방안 연구

박성렬 한국재난정보학회 2022 한국재난정보학회 논문집 Vol.18 No.1

Purpose: One of the methods for preventing disasters such as fire, explosion, and electric shock caused by electricity is to perform grounding. In case of the grounding current includes a frequency component having a high, it is preferable to measure grounding impedance rather than grounding resistance. This study proposes countermeasures to reduce grounding impedance to suppress an ground potential rise due to a grounding current having a frequency component of several kHz or more. Method: General grounding rods and needles-typed grounding rods were buried in the ground, and grounding resistance and grounding impedance were measured, respectively. The characteristics of grounding impedance according to frequency were identified. Result: There was little difference in the measurement results of the grounding resistance between general grounding rods and needles-typed grounding rods. In a frequency range lower than 62.5[kHz], there was little difference in the measurement results of the grounding resistance between general grounding rods and needles-typed grounding rods. In a frequency range higher than 62.5[kHz], the grounding impedance of needles-typed grounding rods was reduced by about 15% than the grounding impedance of general grounding rods. Conclusion: In the commercial frequency domain, it is effective to connect several grounding rods(common grounding) to lower the grounding resistance value. In the frequency domain of several kHz or more, it is expected that needles-typed grounding rods can effectively reduce the ground potential rise due to the grounding current. 연구목적: 전기로 인한 화재·폭발·감전 등의 재해를 예방하기 위한 방법 중의 하나가 접지를 시행하는 것이다. 접지전류가 높은 주파수 성분을 포함하는 경우에는 접지저항보다는 접지임피던스를 측정하는 것이 바람직하다. 본 연구에서는 수 kHz 이상의 주파수 성분을 가지는 접지전류에 의한 대지전위상승을 억제하기 위한 접지임피던스를 줄이는 방안을 제시하고자 한다. 연구방법: 대지에 접지동봉과 접지침봉을 매설하여 각각 접지저항과 접지임피던스를 측정하였고, 주파수에 따른 접지임피던스의 특성을 파악하였다. 연구결과: 접지동봉과 접지침봉의 접지저항 측정 결과는 거의 차이가 없었다. 62.5[kHz] 보다 낮은 주파수 영역에서는 접지동봉이나 접지침봉의 접지임피던스 측정 결과는 거의 차이가 없었으며, 62.5[kHz] 보다 높은 주파수 영역에서는 접지침봉의 접지임피던스가 접지동봉의 접지임피던스보다 약 15% 정도의 저감효과가 있었다. 결론: 상용주파수 영역에서 접지저항 값을 낮추기 위하여 다수의 접지극을 공통으로 접지하는 것이 효과적이고, 접지임피던스가 낮은 접지침봉을 설치하는 경우 수 kHz 이상의 주파수 성분을 가지는 접지전류에 의한 대지전위상승을 효과적으로 억제할 수 있을 것으로 보인다.

서지방호장치의 접지도체에 유도되는 전압이 방호성능에 미치는 영향

이복희,유양우,김유하 한국조명.전기설비학회 2019 조명·전기설비학회논문지 Vol.33 No.4

Surge protective device(SPD) is installed to discharge surge voltages and currents invaded to communication or power lines to the ground. The protective performance of SPDs depend on methods of connecting the grounding conductors of SPDs and equipment to be protected. This paper presents experimental results of effects of induction voltage from grounding conductors of SPDs on their protective performance. The protective effects of SPDs were investigated in cases where the grounding conductor is connected to the grounding terminal close to SPD or equipment. Also electrostatic and electromagnetic induction voltages to communication or power lines from grounding conductor of SPDs were examined. As a result, the residual voltage between the power line and grounding terminal of equipment to be protected is significantly higher than the clamping voltage of SPD when the grounding conductor of SPD is connected to the grounding terminal close to the equipment due to the induction of grounding conductor. However, the residual voltage is minimized when the grounding conductor and communication or power lines are installed very close to each other. The impulse voltages caused by electrostatic and electromagnetic induction to communication or power lines from the grounding conductor of SPDs were decreased with increasing the distance between the grounding conductor and communication or power lines.

LVDC 2선식 전원계통의 고저항 중간점 접지방식 특성 분석

임대식,이기연,김동우,채동주,임승택,문재현 대한전기학회 2021 전기학회논문지 Vol.70 No.6

It is very important to prevent electrical accident, especially the electric shock when it comes to LVDC system as it is widely used in public. Commonly, the mid-point grounding is used in voltage above 200 V (Line-to-Ground) in some countries like USA and Japan. In IEC regulation 60364, there are many theories of grounding in AC and DC system with their own special use. Also, grounding in DC system can be varied as there can be many combination of grounding points including positive/negative electrodes, mid-point wire and mid-point grounding. The purpose of this study is to analyze characteristics of advanced grounding in residence DC system in view of grounding and protection through reviewing the standard IT grounding system, body-current-paths of high-resistance mid-point grounding and impact from electrolytic corrosion of earth electrodes.

Hazard identification and scenario selection of ship grounding accidents

Youssef, Samy Adly Mansour,Paik, Jeom Kee Elsevier 2018 Ocean engineering Vol.153 No.-

<P><B>Abstract</B></P> <P>The objectives of the present paper are to identify the hazard of ship grounding; where a ship runs on a rock with a forward speed, and to select a set of credible scenarios with a limited number that can still represent all possible situations of the accidents. For this purpose, the statistics of ship grounding accidents recorded by authorities for the period of 46 years during 1970–2016 are collated. An extensive analysis is undertaken to examine the statistical characteristics in association with random variables influencing the consequence of grounding. A total of six parameters, namely ship's forward speed, ship's trim angle, rock tip eccentricity, rock length, rock width and rock height are considered as random variables where the displacement or mass of the grounded ship is fixed. Each of the random variables is then formulated with a probability density function. A sampling technique is applied to the probabilistic selection of the grounding scenarios which are to be used for the consequence analysis within the framework of quantitative risk assessment. Important insights developed from the present study are discussed. Details of the analyses are documented.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This article aims to identify the hazard of ship grounding to select a set of scenarios represent all possible situations. </LI> <LI> Statistics of ship grounding accidents recorded by authorities are collated. </LI> <LI> Extensive analyses are performed to examine the statistical characteristics with random variables of grounding. </LI> <LI> A sampling technique is applied to the probabilistic selection of the grounding scenarios. </LI> <LI> Selected credible scenarios are essential within the framework of quantitative grounding risk assessment and management. </LI> </UL> </P>

접지시스템 최적 설계 사례 연구

이강완,양정욱,최종기,신정훈 대한전기학회 2022 전기학회논문지 Vol.71 No.5

The grounding system is a power system facility that establishes safety in the work place by decreasing the induced voltage by burying ground conductors and electrodes in the ground. The most important variable affecting the type and size of the grounding system is the soil resistivity. In order to obtain resonable and effective soil resistivity, necessary and sufficient field measurements as well as selection of a suitable soil model are essentially required. The grounding system is implemented in various ways, such as the selection of ground conductors and electrodes, as well as the mesh configuration of a ground grid and its burial depth. Economical factors such as material cost and construction cost of the grounding system are also required as variables for optimization. This paper is a case study of designing and reviewing a grounding system that reflects efficiency and economic feasibility using the grounding grid design and analysis software.

다중 접지계 GPR 수치 해석을 위한 최적 모델링 기법

이재복,장석훈,명성호,조연규,Lee, Jae-Bok,Chang, Sug-Hun,Myung, Sung-Ho,Cho, Yeon-Gyu 한국전자파학회 2006 한국전자파학회논문지 Vol.17 No.11

본 연구는 combined integration/matrix method에 의해 다양한 접지 시스템의 특성을 모의할 수 있는 수치 해석 기법에 관한 연구이다. Combined integration/matrix method는 접지 시스템을 일정한 길이의 요소로 분할하여 미리 적분을 한 후 적분된 길이 요소 기법에 대해 matrix method를 사용하는 방법으로 연산 시간 및 해석시 에러 발생을 줄일 수 있다. 이를 위해 본 연구에서는 수치 해석시 분할 요소 길이에 대한 오차 분석을 통해 최적의 요소길이 산정 방법을 제시하였으며 이를 통해 실규모 접지 시스템의 다양한 형태의 접지 시스템의 성능 분석이 가능하도록 하였다. 오차 분석을 토대로 접지 전극의 길이와 매설 깊이에 따라 적절하게 요소의 길이를 도출한 결과 분할하고자 하는 요소의 길이는 매설 깊이와 접지 도체의 길이에 주요한 상관 관계가 있음을 알 수 있었으며 본 연구에서 제시한 수치 해석 모델링 방법에 따라 3 % 이내의 해석 정확도를 얻을 수 있었다. 또한, 이를 다중 접지계 해석에 적용하여 현재 산업 플랜트 접지 방식에서 가장 논란이 되고 있는 전원 접지계와 신호/통신 접지계의 공통 접지 및 분리 접지의 영향 평가 등에 활용될 수 있음을 보여주었다. This paper describes the numerical analysis techniques using the Combined Integration/Matrix Method to calculate ground potential rise which can be occurred in the various grounding systems. Combined Integration/Matrix Method is used to reduce the error and computation time with the analytical integration equation and the proper segmentaion of earth embedded conductor. To do it, optimal segmentaion method for the buried conductors is presented through error analysis which is capable of applying the practical scaled various grounding systems. The optimum length of segmented element is much co-related with the buried depth of grounding electrode and the maximum length of buried electrode. As a result, less 3 precent errors was obtained by proposed model. The proposed model is applied to verify an effect of multi-grounding problems which was aroused much controversy with separated or common grounding between the high power grounding system and low power grounding system such as signal and telecommunication grounding.

대규모 그리드 접지전극의 과도접지임피던스의 측정

전병욱(Byung-Wook Jeon),이수봉(Su-Bong Lee),이봉(Feng Li),이승주(Seung-Ju Lee),정동철(Dong-Cheol Jung),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2008 한국조명·전기설비학회 학술대회논문집 Vol.2008 No.10월

This paper presents the transient and conventional grounding impedance behaviors of large grid grounding system associated with the injection point of impulse current The measurement methods consider two possible errors in the grounding-system impedances: (1) ground mutual resistance due to current flow through ground from the ground electrode to be measured to the current auxiliary, (2) ac mutual coupling between the current test lead and the potential test lead. The test circuit was set to reduce the error factors. The transient grounding impedance depends on the rise time and injection point of impulse current It is effective that grounding conductor is connected to the center of the large grid grounding system.

낙뢰 Surge 방호를 위한, 독립접지를 공통접지로 개선하는 효율적인 방법에 대한 연구

우제욱 한국항해항만학회 2013 한국항해항만학회 학술대회논문집 Vol.2013 No.추계

본 논문은 낙뢰 Surge 방호를 위하여 독립접지를 공통접지로 개선하는 효율적인 방법을 제안하였다. 낙뢰 Surge 방호를 위해서는 등전위 이론에 근거하는 공통접지방식이 적합하고, 중성선이 있는 전원계통에서는 공통접지방식을 사용하는 것이 국제적으로 통용되는 기술규격이다. 따라서 낙뢰 Surge에 취약한 문제점을 갖고 있는 기존의 중성선이 없는 전원계통의 독립접지방식을 중성선이 있는 전원계통의 공통접지방식으로 개선을 하고, 정전압소자를 이용하여 낙뢰 Surge를 방호하는 효율적인 등전위 시스템 구축 방법을 제안한다. This paper proposes the effective method to improve the protection from induced lightning surge by making common grounding from individual grounding. Common grounding under equipotential principle is more effective than individual grounding for lightning surge protection, and so common grounding is indicated as international technical standard under the AC power supply system with neutral line. So, this paper is to propose the effective way of induced lightning surge protection method for currently installed power supply system which has no neutral grounded line and individual grounding which are weak for lightning surge protection. This proposal can improve the power supply system as has neutral line, and improve the grounding system to common grounding system. And also this paper proposes to make effective equipotential system with voltage variable shunting devices for lightning surge protection.

낙뢰 시 태양광발전소의 개별접지 및 통합접지에 따른 낙뢰 유도 과전압 비교 분석

이창욱,김재철 한국조명.전기설비학회 2019 조명·전기설비학회논문지 Vol.33 No.3

Photovoltaic Power Plant(PV Plant) facilities have been steadily growing not only in Korea but also in the world. As the demand for PV Plant installation is continuously increasing, damages to the PV Plant are also increasing due to the lightning induced overvoltage caused by the lightning stroke. In this paper, the maximum lightning induced overvoltages at the critical facility for the 100kW PV Plant, (such as connection panel, inverter and distribution panel) in lightning strikes are compared by grounding systems(Isolation Grounding/Common Grounding) with simulation utilizing CDEGS. Simulation results show that the maximum lightning induced overvoltage generated in the critical facility for 100kW PV Plant is approximately 68kV lower in common grounding than in isolation grounding when a lightning current is applied to a point closest to a critical facility. In case of lightning, this paper concludes that common grounding is safer than isolated grounding in order to protect the critical facility for 100kW PV Plant from lightning induced overvoltage.

현대 중국어 사건의 고정화와 상(aspect)

최규발 ( Kyu Bal Choi ),정지수 ( Jie Su Jeong ) 고려대학교 중국학연구소 2010 中國學論叢 Vol.28 No.-

This paper analyzed the aspectual composition elements from the viewpoint of grounding. Grounding is the process of instantiation whereby linguistic expressions are linked to the spatiotemporal entities. A sentence can denote an Event as a partiular in the time and space by the grounding process. Chinese is an aspect prominent language, so viewpoint aspect particles(-le, -zhe, -guo, zai-) can be viewed as grounding predications. In addition, situation aspect elements(e.g. internal arguments, situation type of verbs, event modifying adverb phrases, verbal complements ect.) also function as grounding elements.