• Title, Summary, Keyword: grounding grids

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Reduction of the the Ground Surface Potential Gradients by Installing Auxiliary Grounding Grids (보조접지그리드의 시설에 의한 대지표면전위경도의 저감)

  • 이승칠;엄주홍;이복희;김효진
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.16 no.2
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    • pp.121-129
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    • 2002
  • The present paper describes a technique for installing an effective grounding grids, the major objective is forced on the experimental evaluation of the performance and characteristics with the arrangement and installation method for grounding grids consisting of the means to protect electric shock, electronics and computerized facilities against lightning, switching and ground fault surges. The study is oriented on two major areas: (1) the analysis of the ground surface potential gradient with the arrangement of grounding grids, (2) the control of the dangerous ground surface potential rise. The experiments wee carried out with the impulse currents as a function of the installation method or arrangement of grounding grids. An installation method of the inclined auxiliary grounding grid was proposed to overcome the drawbacks of equally spared grounding grids, i.e. an appropriate design concept far the installation of grounding grids was found out, It has been shown that the installation of the intwined auxiliary grounding grid can also result in a mere than 50% decrease in the maximum potential gradient on the ground surface and enhance the level of safety for persons and electronic equipments..

High Frequency Impedance Calculation of Grounding Meshes Installed at Power Substations (전력용 변전소에 설치된 메쉬 접지망의 고주파 임피던스 계산)

  • Han, Poong;Choi, Chang-Hyek
    • Proceedings of the KIEE Conference
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    • pp.1578-1582
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    • 1998
  • The ground potential rise generated by the switching surge or lightning stroke may be dangerous to personnel and cause damage to electronic control parts. For a first step to the transient performance analysis. high frequency impedances of grounding grids have been calculated and discussed. Grounding grids include 7 square grids from $10m{\times}10m$ to $80m{\times}80m$. The high frequency current was injected into the center and a corner of the grounding grid. The calculation results indicate that the impedance of the grounding grid is significantly influenced by frequency and the point of injection of the current. and the effective radius of a large grounding grid may be represented in $15{\sim}20m$.

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Ground Impedance and Frequency Response Characteristics of Large-scale Ground Rods (대형 봉상 접지전극의 접지임피던스와 주파수 응답특성)

  • Lee, Bok-Hee;Eom, Ju-Hong;Kim, Tai-Doo;Chung, Dong-Chul;Kil, Hyeong-Joon
    • Proceedings of the KIEE Conference
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    • pp.1791-1793
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    • 2003
  • In order to analyze the dynamic characteristics of ground impedance in large grounding system for lightning and surge protections, a novel method for measuring the ground impedance as a function of frequency was proposed. The experiments were carried out in the grounding system composed of ground rods and mesh grids. The test current was injected by the variable frequency inverter whose frequency is linearly controlled in the range of $5{\sim}500$kHz. The ground impedance and frequency response of the grounding system were mainly caused by the inductive current flowing through grounding conductors over the frequency of 2002. In the combined grounding system of rods and mesh grids, inductive component of ground impedance was significantly decreased. It was fumed out that the grounding system is effective for the surge protection.

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Analysis of the Ground Impedance of Ground Grids Combined with the Carbon Ground Electrodes (탄소접지극이 병설된 접지그리드의 접지임피던스의 해석)

  • Lee, Bok-Hee;Um, Sang-Hyun;Kim, You-Ha;Lee, Kang-Soo;Jeon, Byung-Wook;Choi, Jong-Hyuk
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.3
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    • pp.36-42
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    • 2013
  • This paper deals with the frequency-dependent ground impedance of ground grids combined with the carbon ground electrodes. Ground grids are generally valid for multipurpose grounding systems as well as lightning protection systems. The carbon ground electrodes may be supplementarily used to reduce the high frequency ground impedance and to improve the transient response to surge currents. The frequency-dependent ground impedances of ground grids combined with or without the carbon ground electrodes were measured and their simulations with due regard to frequency-dependent soil resistivity were implemented by using EMTP program and Matlab modeling. As a consequence, the ground impedance of ground grids combined with the carbon ground electrodes is significantly reduced when the test current is injected at the terminal of the carbon ground electrode. The measured and simulated data for the test ground grids fairly agree with each other. It was found that the proposed method of simulating the frequency-dependent ground impedance is distinguished. The simulation techniques of predicting accurately the ground impedances without actual measurements can be used in the design of grounding systems based on ground grids and the carbon ground electrodes.

A Novel Method for Measuring the Ground Impedance using Variable Frequency Inverter (가변주파수 인버터를 이용한 접지임피던스의 새로운 측정기법)

  • 이복희;엄주홍
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.53 no.5
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    • pp.253-257
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    • 2004
  • In order to analyze the frequency dependance of ground impedance in grounding grids for lightning and surge protection, a novel method for measuring the ground impedance as a function of frequency were experimentally investigated. The experiments were carried out in rectangular grounding grids with $6{\times}8$ conductors of 22 $mm^2$ buried at a depth of 0.5 m. The test current was injected by the variable frequency inverter whose frequency is linearly controlled for the established period in the range of 5∼500 KHz. The amplitude and phase of ground impedance were calculated from the waveforms of the test current and ground potential rise measured by the band-pass filter tuned in a specific frequency. The frequency dependence of ground impedance was mainly caused by the inductive current flowing through grounding conductors over the frequency of 100 KHz. The proposed measurement method of ground impedance would be applicable to evaluate the transient response characteristics in lightning protection grounding systems.

Improved Mesh Grounding Electrode Model by Changing Arrangements of Internal Conductors of the Mesh Grounding Electrode (메쉬접지극의 내부도체 배치에 따른 개선된 메쉬접지극 모델)

  • Shim, Yong-Sik;Choi, Hong-Kyoo;Kim, Tae-Hoon;Song, Young-Joo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.6
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    • pp.60-66
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    • 2010
  • Mesh grounding electrodes in Korea and abroad are designed as lattice-shaped equidistance grounding grids. In case of a lattice-shaped grounding Grid, however, there is a problem of higher touch voltage at the corner of the grid relative to the center. To overcome this problem, we used oblique-shaped equidistance grounding grid to reduce the area of the corner where mesh voltage occurs. As a result the mesh voltage was reduced. Therefore, this paper suggests the use of oblique-shaped grounding grid instead of the existing lattice-shaped ones. It applied the same grounding design dimensions for both lattice-shaped and oblique-shaped grounding grids, compared and analyzed mesh voltage, GPR, ground resistance, total length of grounding conductor, verified that oblique-shaped grounding grid is superior to the lattice-shaped.

Improvement of Transient Grounding Performance with Auxiliary Grounding Grid (보조접지망에 의한 과도접지성능의 개선)

  • Choi, Jong-Kee;Jung, Gil-Jo;Kim, Seon-Gu
    • Proceedings of the KIEE Conference
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    • pp.932-934
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    • 1998
  • In an electric substation, there are many sources of surge such as switching operations or lightning strokes. A grounding system submitted to such surge current presents very different behaviour from the observed under low frequency current. Especially, it has been reported that significant overvoltage occurs at the current feed-in point, and this may cause damages to other grounded components in the substation area. This paper describes the basic mechanism of improvement of grouding performance in transient state with auxiliary grounding grids.

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The Potential Interference of the Grounding Grids (격자형 접지전극의 전위간섭)

  • Lee, Bok-Hee;Lee, Tae-Hyung;Lee, Su-Bong;Jung, Hyun-Uk;Gil, Hyoung-Jun
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.261-263
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    • 2005
  • This paper presents the potential interferences between various grounding electrodes. The ground potential rise and potential interference coefficient between grounding grid and ground rod were calculated. The potential rise and potential interference coefficient strongly depend on the distance between grounding electrodes.

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A Novel Non-contact Measurement Method for the Detection of Current Flowing Through Concealed Conductors

  • Yang, Fan;Liu, Kai;Zhu, Liwei;Hu, Jiayuan;Wang, Xiaoyu;Shen, Xiaoming;Luo, Hanwu;Ammad, Jadoon
    • Journal of Magnetics
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    • v.22 no.1
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    • pp.43-48
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    • 2017
  • In order to detect the current flowing through concealed conductor, this paper proposes a new method based on derivative method. Firstly, this paper analyzes the main peak characteristic of the derivative function of magnetic field generated by a current-carrying conductor, and a relationship between the current flowing through the conductor and the main peak of the derivative function is obtained and applied to calculate the current. Then, the method is applied to detect the conductor current flowing through grounding grids of substations. Finally, the numerical experimental and field experiment verified the feasibility and accuracy of the method, and the computing results show that the method can effectively measure the conductor current of grounding grids with low error, and the error is within 5 %.

An Analysis of Potential Interference in the Vicinity of the Vertical Ground Rod (수직 접지전극 주변에서 전위간섭의 분석)

  • Lee, Bok-Hee;Lee, Kang-Soo;Seong, Chang-Hoon;Choi, Jong-Hyuk
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.5
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    • pp.85-91
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    • 2011
  • A grounding system is generally composed of several vertical, horizontal electrodes or grids. Excessive ground potential rises due to adjacent grounding electrodes can cause failures or misoperation of electronic devices and control systems. It is therefore necessary for computer-related and information-oriented equipment to be placed at a sufficient distance from the areas influenced by grounding electrodes. In this paper, in order to propose a method for evaluating the ground potential rise and interference in the vicinity of vertical grounding electrodes, the experimental and theoretical results on the potential interference between vertical grounding electrodes and its frequency dependence were described. The ground potential rise is sharply decreased with increasing the distance between grounding electrodes. In case that the separation of vertical grounding electrodes is less than 1.5[m], the potential interference coefficient was greater than 0.1 and linearly increased with the frequency of the test current within the frequency of 1[MHz].