• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
• /
• pp.2286-2288
• /
• 2005

This paper describes impulse grounding impedance and touch voltage when impulse current is injected to grounding systems for distribution concrete pole. Impulse grounding impedance is a significant factor in analyzing transient grounding impedance. The touch voltage is measured in four directions. The maximum touch voltage was 520V and the minimum touch voltage was 47.3V when the input current was 100A.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 E
• /
• pp.1578-1582
• /
• 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 $15{\sim}20m$.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 E
• /
• pp.1843-1846
• /
• 1997

This paper describes the fault reducing effects of the 154 kV transmission tower by auxiliary grounding from the top of the tower to ground. The grounding surge impedance of the auxiliary grounding system is calculated by CDEGS(:Current Distribution Electromagnetic Interference Grounding and Soil Structure Analysis), and the critical lightning back flashover current and arcing horn dynamic characteristics are simulated by EMTP/TACS(:Electromagnetic Transient Program/Transient Analysis of Control Systems). The calculated results of total LFOR(Lightning Flashover Rate) shows that the LFOR can be reduced from 5.2(count/100km. year) to 3.4 by auxiliary grounding on the 154 kV transmission tower with one ground wire shielding system.

• 조명전기설비학회논문지
• /
• 제27권3호
• /
• pp.36-42
• /
• 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.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
• /
• pp.451-455
• /
• 2004

Although DC ground resistance is a good index of performance for a grounding system, it does not reflect the grounding performance during the transient states. Besides, impulse ground impedance, which is defined by a ratio of the peak value of transient ground potential rise to the peak value of impulse current, cannot be an absolute performance index due to its dependence on impulse current shape. In this paper, a grounding performance of needle-typed ground rod has been compared with simple ground rod.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
• /
• pp.565-569
• /
• 2004

This paper deals with the characteristics of potential rise and effective impulse impedance of deep-driven ground rods that are used in high resistivity soil or in confined places such as downtown. Also the effects of the impulse and fault currents on the deep-driven ground rods combined with different type grounding electrodes like as mesh grids and counterpoises are described. The $8/20{\mu}s$ impulse current and other wave currents with different rise times are injected into the test ground rod and the effective impedances are examined. The most effective way to obtain the fine transient impedance behaviors of deep-driven ground rods is to reduce the inductive component of grounding electrode systems combined with other ground electrodes.

• 조명전기설비학회논문지
• /
• 제22권12호
• /
• pp.87-94
• /
• 2008

이 논문은 뇌 임펄스전류에 의한 접지시스템의 과도적 특성에 관련된 토양의 이온화 현상과 파라미터를 기술하였다. 몇 가지 토양에서 발생하는 이온화 특성을 실험적으로 조사하였다. 절연파괴 임계전계강도와 이온화 반경을 용이하게 분석하기 위하여 원주형 실험기를 사용하였다. 전압과 전류 파형을 기초로 토양의 절연파괴 임계전계강도, 임피던스의 임펄스 전류 크기에 대한 의존성, V-I곡선과 과도임피던스를 검토하였다. 이온화 과정과 비선형 특성은 토양 종류에 매우 의존적이며, 포장용수량의 토양에서 2개의 전류피크는 나타나지 않았다. 본 연구 결과는 토양의 이온화를 고려하여 임펄스전류의 영향을 받는 접지시스템의 과도적 성능의 향상에 유용한 정보가 될 것이다.

• 조명전기설비학회논문지
• /
• 제19권1호
• /
• pp.94-100
• /
• 2005

본 논문은 전류유입위치에 따른 봉상접지전극의 과도 및 실효임펄스임피던스의 특성에 관한 것으로 뇌격전류를 인가하여 실규모 접지봉에 대한 시간영역에서의 성능을 평가하였다. 임펄스전류가 가해진 봉상접지전극의 과도 접지임피던스는 접지저항보다 높게 나타났으며, 접지전극의 길이가 길어짐에 따라 접지저항과 실효임펄스접지임피던스는 감소되었다. 또한 실효임펄스접지임피던스는 짧은 시간범위에서는 급격하게 증가하였다. 접지저항의 저감은 접지시스템의 임펄스임피던스 특성의 개선에 결정적인 역할을 한다. 임펄스전류를 접지봉의 하단에 인가하였을 때 접지봉 전위의 파두부에 고주파의 진동 파형이 포함되고 실효임펄스임피던스는 다른 경우보다 높게 나타났다.

• 조명전기설비학회논문지
• /
• 제25권4호
• /
• pp.117-123
• /
• 2011

Lightning and switching surges propagating through the grounding conductors lead to transient overvoltages, and electronic circuits in information technology systems are very susceptible to damage or malfunction from the electrical surges. Surge damages or malfunctions of electrical and electronic equipment may be caused by potential rises. To solve these problems, it is very important to evaluate the ground surface potential rises and hazardous voltages such as touch and step voltages at or near the grounding systems energized by electrical surges. In this paper, the performance of grounding systems against the surge current containing high frequency components on the basis of the actual-sized tests is presented. The ground surface potential rises and hazardous voltages depending on impulse currents for vertical or horizontal grounding electrodes are measured and analyzed. Also the touch and step voltages caused by the impulse currents are investigated. As a result, the ground surface potential rises, the touch and step voltages near the grounding electrodes are raised and the conventional grounding impedances are increased as the front time of the injected impulse currents is getting faster.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.612-613
• /
• 2007

The line impedance is important data that are applied in all analysis fields of electric power system such as power flow, fault current, stability and relay calculation etc. Usually, the impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, the impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and earth resistances. Therefore, if there is a fault in cable system, these terms will severely be caused many errors for calculating impedance. In this paper, the line impedance is measured in a power system of underground cables, and is analyzed by a generalized circuit analysis program, EMTP(Electromagnetic Transient Program), for comparison with the measured value. These analysis results are considered to become foundation of impedance calculation for underground cables.