• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.645-649
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• 2007

Ground systems flow fault currents into the ground, and suppress Ground Potential Rise (GPR) by the current. In this paper, we designed and fabricated a surge impedance meter to analyze the ground impedance in wide frequency ranges. The meter consists of a surge generator, a high speed sample/hold (S/H) circuit and an associated electronics. The surge generator produces surge voltage up to 5kV in ranges of $50\sim500ns$. Field tests were carried out to evaluate the surge impedance meter at a driven-rod ground system. The results showed that surge impedance of ground systems should be measured by various fast surge waveforms, since the impedance increases as the rise time of applied voltage increases.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.10a
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• pp.67-67
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• 2011

본 논문에서는 접지시스템의 성능을 평가하기 위한 광대역 접지임피던스 분석기에 대하여 기술하였다. 시제작 측정기는 65 Hz~1.28 MHz의 신호발생부와 이득 20 dB, 출력 임피던스가 $0.1{\Omega}$인 전류 증폭부, 전압 및 전류 측정부, 신호처리부, 표시부로 구성된다. 또한, 외부 노이즈로 인한 측정의 오차를 줄이기 위하여 디지털 대역통과 필터를 적용하였다.

• 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.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.364-368
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• 2007

현재 일반적으로 서지 발생장치를 이용하여 측정하는 서지임피던스 측정기는 측정시 측정의 경향성 및 재현성이 상당히 불량하여 측정값을 신뢰하기 힘들고 일반적인 접지저항 측정기로는 측정값이 정확하게 측정되지 않는 문제점이 있어 탑각의 누설전류를 이용한 활선철탑 접지저항 측정기에 의한 정확한 접지저항 측정을 하는 것에 이 연구의 목적이 있음

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.26-26
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• 2010

Line to ground faults or lightning strikes in electrical power systems produce high frequency overvoltages. With this reason, a wide band analysis of the ground impedance is necessary. In the paper, design of a wideband ground impedance meter which can measure the ground impedance in ranges from 65 Hz to 1.5 MHz is described. Also, a noise elimination method by a digital band-pass filter during measurement is proposed. The maximum measurement error of the meter is estimated 3 % in full ranges.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.194-195
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• 2006

This study evaluated the impedance characteristics of earth termination system and developed a variable frequency-typed inverter (measuring tool) for the utilization in ground design for lightning protection. The variable-frequency-typed inverter were composed of rectification part, voltage adjuster, IGBT controller and measuring part. Meanwhile, the square wave signal of variable frequency converted its frequency up to lightning surge band by using an IGBT after rectifying an alternating current (AC). It conducted performance evaluation of ground impedance of actual earth termination system by using the developed measuring tool for ground impedance and confirmed that such impedance-oriented performance evaluation was effective in the design of lightning protection.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.298-299
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• 2007

매설배관은 관련법규에 따라 방식(anticorrosion)상태나 배관의 효율적인 유지관리를 위하여 배관의 방식전위를 관로를 따라 주기적으로 측정하여 전철의 영향이나 타 배설배관 및 방식시스템의 상황이 파악되어야 한다. 일반적인 방식전위측정기는 토양비저항이 30 내지 40 $M{\Omega}$ 이상의 높은 지역에서의 방식전위측정 시 전위왜곡이 발생하여 정확한 방식상태를 판단하기 곤란한 경우가 있다. 이러한 장애를 극복하고자 입력임피던스를 100$M{\Omega}$으로 설계하여 방식전위 측정시의 왜곡을 개선 및 정확도를 높이고 방식유지관리에 반드시 필요한 직류 및 교류 전압, 전류, 접지저항, 주파수 등을 측정할 수 있는 방식전용 다기능 계측기를 개발하였으며, 이는 측정 및 휴대가 용이하여 현장에 도움을 주고 있다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.793-797
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• 2010

The basic performance of the ground system is evaluated as the ground resistance by applying low frequency current below 1 kHz. However, characteristics of the ground system should be analyzed by high frequency current up to 1 MHz since transient currents having a few hundred kHz component flow during a line-to-ground fault and/or a lightning strike. This paper deals with the design and fabrication of a wideband ground impedance meter (WGIM) which measures the impedance of ground systems in ranges from 65 Hz to 1.28 MHz. Also, a noise elimination algorithm using a digital bandpass filter is proposed. The maximum error of the WGIM is 4.91% in the measurement frequency range.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.19-24
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• 2016

One of key parameters on lightning protection system design of electric, information and communication system is grounding impedance. Earth impedance includes numerous information about earthing performance of grounding system. This paper suggests grounding impedance measuring device which is comprised of wideband current source, voltage and current measuring components. We used IQ Demodulation to measure more accurate phase difference of voltage and current. The range of frequency is up to 1 MHz that is IEEE defined as the range of lightning surge. We compared developed grounding impedance measuring device with existing one to test its performance, and we used grounding system while we implemented measurement and analysing by using fall of potential method IEEE Std.81 proposed.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.205-212
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• 1999

When we want to observe and record a patient's EEG in an operating room, the operation of electrosurgical unit(ESU) causes undesirable artifacts with high frequency and high voltage. These artifacts make the amplifiers of the conventional EEG system saturated and prevent the system from measuring the EEG signal. This paper describes a high-performance bipolar EEG amplifier for a CSA (compressed spectral array ) system with reduced ESU artifacts. The designed EEG amplifier uses a balanced filter to reduce the ESU artifacts, and isolates the power supply and the signal source of the preamplifier from the ground to cut off the current from the ESU to the amplifier ground. To cancel the common mode noise in high frequency, a high CMRR(common mode rejection ratio) diffferential amplifier is used. Since the developed bipolar EEG amplifier shows high gain, low noise, high CMRR, high input impedance, and low thermal drift, it is possible to observe and record more clean EEG signals in spite of ESU operation. Therefore the amplifier may be applicable to a high-fidelity CSA system.