• 한국철도학회논문집
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• 제10권2호
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• pp.117-123
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• 2007

In this study, a ubiquitous sensor for condition monitoring of insulators and lightning arresters installed in power distribution lines and electric traction vehicles is presented. The sensor consists of two parts; a leakage current measurement and a lightning surge detection. Measured data are transmitted to a supervisory computer through ZigBee protocol based on IEEE 802.15.4. To detect leakage current, a window type Mn-ZCT is used and a low-noise amplifier with a gain of 60dB is designed, and this can measure leakage current in ranges of $100{\mu}A{\sim}5mA$. A sample-hold (S/H) and a Rogowski coil are injected to analyze the magnitude of surge current in ranges from 100A to 10kA with $8/20{\mu}s$-waveform.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1416_1417
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• 2009

This paper shows the characteristic of wave tail according to inductance values in 10/$350{\mu}s$ impulse circuit with crowbar switch. The PSpice was used to simulate the 10/$350{\mu}s$ current waveform and lightning current impulse generator was used to generate real current waveform. As a capacitor of condenser bank increases, a virtual front time increases and a time to half-value decreases. To get a perfect 10/$350{\mu}s$ current waveform, we should consider the combination of circuit values of the inductance, capacitance, time difference between trigger pulses and charged voltage of capacitor bank.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.907-909
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• 1998

This paper describes the effect of impulse current on degradation of ZnO blocks. In this study, an impulse current generator which can produce 8/20 [${\mu}s$], 3 [kA] and 4/10 [${\mu}s$], 5 [kA] waveform is designed and fabricated to simulate the lightning impulse current. The residual voltage, reference voltage, and leakage current flowing to the ZnO blocks are observed. The experimental results show that the leakage current increases continuously with the number of applied impulse current, but no significant changes in residual voltage and in operating voltage are observed until the ZnO block is destroyed. Also, it is confirmed that the main factor on degradation of ZnO blocks is rather the total energy applied to ZnO blocks than the peak value of the impulse current.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.144-150
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• 2008

In this paper, the safety for passengers of composite car-body against lightning strikes was analyzed by the application of an impulse generator which can produce impulse current up to 50 [kA] with 8/20 [us] waveform. Potential difference on inside surface of the car-body was measured as a safety parameter for the passengers against lightning strikes. The potential difference between 20 [cm] distant was 175 [V] at 37.67 [kA], and it corresponded to 875 [V] between 1 [m] distant. The amount of charge flowing a passenger at 100 [kA] impulse current can be estimated to 0.31 [mA s]. This is much less than the limit amount of charge for human body, 30 [mA s] which is presented by Koeppen and Osypka.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권10호
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• pp.469-475
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• 2003

Resistive leakage current flowing ZnO blocks increases with its ages, which is an important indicator of arrester deterioration. However, a complicated circuitry is essential to measure the resistive leakage current included in the total leakage current, and the difficult handling of the measurement makes few applications to the fields. In this paper, we propose a resistive leakage current measurement device which is composed of a current detection circuit and an analysis program operated on a microprocessor. The device samples the input leakage current waveform digitally, and discriminate the zero-cross and the peak point of the waveform to analyze the current amplitude vs. phase. The capacitive leakage current is then eliminated from the total leakage current by using an algorithm to extract the resistive leakage current only. Also, the device can be operated automatically and manually to analyze the resistive leakage current even when the leakage current waveform is distorted due to various types of arrester deterioration. To estimate the performance of the device, we carried out a test on ZnO blocks and lightning arresters. From the results, it is confirmed that the device could analyze most parameters needed for the arrester diagnostics such as total leakage current. resistive leakage current, and the $3^rd$ harmonic leakage current.

• 한국전기전자재료학회논문지
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• 제22권6호
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• pp.526-531
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• 2009

In this paper, the safety for passengers of composite car-body against lightning strikes was analyzed by the application of an impulse generator which can produce impulse current up to 50 kA with 8/$20{\mu}s$ waveform. Potential difference on inside surface of the car-body was measured as a safety parameter for the passengers against lightning strikes. The potential difference between 20 em distant was 175 V at 37.67 kA, and it corresponds to 875 V between 1 m distant. The amount of charge flowing a passenger at 100 kA impulse current can be estimated to $0.31\;mA{\cdot}s$. This is much less than the limit amount of charge for human body, $30\;mA{\cdot}s$ which is presented by Koeppen and Osypka.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.233-235
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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 significantly increased. This paper presents how the impulse current works on the long vertical ground rods with a different length. As a result, it can be estimated what the waveform is composed of and how the GPR is affected by the rate of current change.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.736-741
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• 2006

In this study, a ubiquitous sensor for condition monitoring of insulators and lightning arresters installed in power distribution lines and electric traction vehicles is presented. The sensor consists of two parts; a leakage current measurement and a lightning surge detection. Measured data are transmitted to a supervisory computer through ZigBee protocol based on IEEE 802.15.4. To detect leakage current, a window type Mn-ZCT is used and a low-noise amplifier with a gain of 60dB is designed, and this can measure leakage current in ranges of $100{\mu}A{\sim}5mA$. A sample-hold(S/H) and a Rogowski coil are injected to analyze the magnitude of surge current in ranges from 500A to 10kA with $8/20{\mu}s$-waveform.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.717-723
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• 1999

The transient characteristics of grounding systems play a major role in the protection of power equipments, electronic circuits and info-communication facilities against surges which arise from lightning or ground faults. Electronic devices are very weak against lightning surges injected from grounding systems and can be damaged. The malfunction and damage of electronic circuits bring about bad operation performances, a lot of economical losses, and etc. Therefore, in order to obtain the effective protection measure of electronic devices from overvoltages and lightning surges, the analysis of the transient grounding impedances in essential. One of this work is to examine the transient behaviors of grounding impedances under steplike currents for various grounding systems. And the other of this work is to evaluate the transient behaviors of a grid with rods under impulse currents and to investigate the effect of grounding lead wire. Transient grounding impedances of a grid with rods under impulse current waves have been measured as a parameter of the length of the grounding leads. Z-t, Z-i and V-i curves of transient grounding impedance under impulse current waveforms have been measured and analyzed. It was found that the grounding impedance gives the inductive, resistive and capacitive aspects under steplike current. Transient grounding impedance characteristics were very different with shapes, geometries of ground electrodes. Also, they were dependent on the waveform and magnitude of impulse current.

• 한국항공우주학회지
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• 제44권12호
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• pp.1071-1086
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• 2016

항공기는 결빙, 난기류, 낙뢰 등 환경적 요인에 의해 안전성을 위협받는다. 그 중 낙뢰는 항공기에 강한 전류와 전압을 유입시켜 고온의 열과 자기장을 발생시키므로 항공기 안정성에 큰 위협이 된다. 본 연구에서는 낙뢰의 발생원리 및 항공기 낙뢰 피격 메카니즘을 설명하고 항공기에 대한 낙뢰의 직접, 간접 영향성을 다룬다. 먼저 항공기 낙뢰 지침서인 ARP를 분석하여 항공기 낙뢰모사와 부착위치에 대한 분석을 진행하였으며, 이를 전산 시뮬레이션에 적용하였다. 또한 ABAQUS 소프트웨어를 활용한 열적, 전기적 시뮬레이션을 통해 연료탱크의 낙뢰 영향성 분석 및 낙뢰보호시스템 설계를 진행하였다. 그리고 Maxwell 방정식에 기초한 EMA3D 소프트웨어를 활용하여 항공기 전기체의 전류 흐름에 대한 전산수치해석을 진행하였다.