• 대한전기학회논문지:전력기술부문A
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• 제52권7호
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• pp.421-428
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• 2003

After the cable is installed, many geometric factors, such as bowing types of the cable and the length difference of the cable between each minor section will cause the impedance unbalance between cables. The impedance unbalance will increase or decrease the sheath circulating currents, which are critical to human safety and sustaining the capabilities of electric power. Accordingly, in this paper, a new method is also proposed to reduce the sheath circulating currents and an reduction equipment according to the theory of the new method is developed. The reduction equipment is tested when the cable is on service. The test results show that it can reduce the sheath circulating currents by up to 97.8［%］. This confirms the validation of the new method and the reduction equipment, and assures the safe operation of the transmission cables. In order to illustrate the safe operation of the cable with new current reduction equipment at transient state due to lightning and single line-to-ground fault, extensive simulations have been made. Then the protection scheme of sheath circulating currents reduction equipment is proposed by adopting the new device of RDP(Reduction Device Protector).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.63-65
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• 2004

The recent advancement in the power electronic technique has increased the use of induction motor fed by inverter using high-frequency switching devices. Also the tendency is toward larger size and higher voltage. Therefore, The IGBT (Insulated-Gate Bipolar Transistor) that is high switching frequency element has been using increase. But, The switching surge voltage was occurred by high switching frequency of inverter has appeared a voltage doubling in the motor input terminal due to mismatching of cable characteristic impedance and motor characteristic impedance. Actually, The Switching surge voltage became the major cause to occur the insulation failure by serious voltage stress in the stator winding of induction motor. The short during rise time of switching surge and cable length is increased, the maximum transient voltage seen at the motor terminals increases. In this paper, Analyzed switching surge transient voltage of power cable pulling is used EMTP(Electromagnetic Transient Program) at the induction motor terminal and in cable.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.1047-1051
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• 2004

Charge amplifier systems benefit from the very wide dynamic range of PE accelerometers by offering flexibility in adjusting the electrical output characteristics such as sensitivity and range. They are well suited for operation at high temperatures. Modern charge systems feature improved low noise operation, simplified digital controls, and dual mode operation for operation with charge or IEPE voltage mode sensors. high impedance circuitry is not well suited for operation in adverse field or factory environments. The resolution of a PE accelerometer may not be specified or known since noise is a system consideration determined by cable length and amplifier gain. IEPE accelerometrs operate from a constant current power source, provide a high-voltage, low-impedance, fixed mV/g output. They operate through long, ordinary, coaxial cable in adverse environments without degradation of signal quality. They have limited high temperature range. IEPE sensors are simple to operate. Both resolution and operating range are defined specifications. Cost perchannel is lower compared to PE systems since low-noise cable and charge amplifiers are not required.

• 산업기술연구
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• 제27권A호
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• pp.169-175
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• 2007

In High-Speed DSP systems, crosstalk between transmission lines of multi-channel can degrade the performance of equipment operations. This paper presents a microwave board to measure multi-channel coaxial cable assembly. The designed board has good performances from DC to 3 GHz, which have improved characteristic impedance, reduced crosstalk by using via fence, and low transmission loss. Using the designed board, we can measure characteristics of DUT(Device Under Test) such as return loss, insertion loss, crosstalk phase delay, and characteristic impedance. The measured results are used to improve performances of a produced coaxial cable assembly.

• 한국전자파학회논문지
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• 제11권6호
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• pp.886-892
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• 2000

본 논문에서는 IEC(International Electrotechnical Commission) Standard 96-1에 규정된 RF 케이블의 표현전달 임피던스 측정법을 설명하고, 1 MHz ~ 30MHz 동작주파수범위에서 설계 제작된 triaxial fixture를 사용해 전압 및 산란계수를 측정하여 상용 RF 케이블의 표면전달 임피던스를 얻었다.

• 한국강구조학회 논문집
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• 제22권1호
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• pp.21-31
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• 2010

본 연구에서는 구조 케이블의 인장력 모니터링을 위한 무선 임피던스 센서노드를 개발하였다. 이를 위해 다음과 같은 연구가 수행되었다. 첫째, 경제적이고 자동화된 구조 케이블의 인장력 모니터링을 위한 무선임피던스 센서노드를 설계/제작 하였다. 둘째, 자동화된 인장력 모니터링을 위해 임피던스 기반 모니터링 기법을 무선 센서노드에 내장하였다. 셋째, 측정 범위가 제한적인 무선임피던스 센서노드의 한계점을 극복하기 위하여 인터페이스 와셔를 이용하는 구조케이블 인장력 모니터링 기법을 제안하였다. 마지막으로 내장형/외장형 텐던을 가지는 모형 프리스트레스트 콘크리트 거더에 대하여 무선임피던스 센서노드와 인터페이스 와셔를 이용하는 모니터링 기법의 적용성을 평가하였다.

• 전기학회논문지
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• 제63권10호
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• pp.1364-1370
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• 2014

Power system fault analysis has been based on symmetrical component method, which describes power system elements by positive, negative and zero sequence impedance. Obtaining accurate line impedances as possible are very important for estimating fault current magnitude and setting distance relay accurately. Especially, accurate calculation of zero sequence impedance is important because most of transmission line faults are line-to-ground faults, not balanced three-phase fault. Since KEPCO has started measuring of transmission line impedance at 2005, it has been revealed that the measured and calculated line impedances are well agreed within reasonable accuracy. In case of underground transmission lines, however, large discrepancies in zero sequence impedance were observed occasionally. Since zero sequence impedance is an important input data for distance relay to locate faulted point correctly, it is urgently required to analyze, detect and consider countermeasures to the source of these discrepancies. In this paper, development of pre/post processor to ATP (Alternative Transient Program) version of EMTP (Electro-Magnetic Transient Program) for sequence impedance calculation was described. With the developed processor ATP-cable, effects of ground resistance and ECC (Earth Continuity Conductor) on sequence impedance were analyzed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.394-396
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• 2004

In order to reduce the sheath circulating current, same arrangement and balanced length of cable are required for the underground cable system. But practically, changing the whole arrange of cable which is already constructed is impossible. Therefore, It is necessary to apply the restraining-unit of sheath circulating current at the cross-bonding wire of insulated joint because the impedance of restraining-unit is able to reduce sheath circulating current at a normal condition. Even at a transient state, the restraining-unit must maintain electrical and mechanical characteristics. In this paper, the features of restraining-unit developed by LG Cable as well as the electrical test results are described. It proves that the restraining-unit is applicable to the underground cable system where sheath circulating current rises.

• 한국해양공학회지
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• 제3권2호
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• pp.526-526
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• 1989

• 한국전자파학회지:전자파기술
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• 제4권2호
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• pp.24-33
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• 1993

본 논문에서는 터널, 지하철 등 지하 공간에서의 무선통신을 가능하게 하는 주기적인 슬롯을 갖는 누설동축케이블의 전자파 특성을 해석하였다. 주기적인 구조를 해석하기 위해 Floquet 정리를 사용하여 동축 케이블의 표면파 특성을 해석하였고, 전파상수 및 필드의 진폭을 구하기 위하여 다변수 Newton Raphson법을 사용하여 식을 전개하였다. 이 값으로 부터 총축 케이블의 필드 분포, 표면 전송 임피던스(surface transfer impedance), 전류분포, 전파상수 등을 구하였다.