• Journal of Electrical Engineering and Technology
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• 제6권1호
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• pp.111-118
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• 2011

In recent years, various types of partial discharge (PD) methods such as capacitive, inductive, electromagnetic, and acoustic coupling techniques have been developed for diagnosing rotating machines. An electromagnetic (EM) probe, which is an inductively coupled type of sensor, is required for detecting corona and internal discharges during off-line tests. In this study, a new technique for enhancing the measurement sensitivities for corona and internal discharge based on an EM inductive position sensor is proposed. An EM probe that winds wires around horseshoe-shaped and cylindershaped ferrites as helices is designed and optimized for the implementation of off-line PD monitoring of the stator winding of a rotating machine. The measurement system based on this design is implemented, and it is verified from the results of the experiment performed in this study that the probe provides similar performance as existing commercial products.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.39-43
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• 2013

To reduce the magnetization loss of a coated conductor, the striation and the transposition have to be accomplished for magnetic decoupling. The loss reduction effect in incomplete as well as complete striated YBCO CCs was reported in previous research. At the case of the incomplete striated sample, the end region of the sample is non-striated. So, it is not jointed with each other. In power applications, the joint is needed because current leads must be connected with HTS coils. In this research, the influence of end-joint methods with copper and superconducting joint on magnetization loss in striated YBCO CC and spiral winding samples are presented and compared with non-striated measured result.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.172-177
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• 2006

During normal machine operation, partial discharge(PD) tests were performed with partial discharge analyzer(PDA) in two hydrogenerators. Six cable couplers were installed in circuit ring bus and endwinding of three phases. PDA showed that the normalized quantity number(NQN) and the partial discharge magnitude$(Q_m)$ were very low in hydrogenerator #1 and #2, respectively. The trend analyses of NQN and $Q_m$ value are available for monitoring of the insulation condition in hydrogenerator stator windings. The insulation condition of stator winding can be assessed. Discharge at conductor surface was discovered in B phase(C2 coupler) of hydrogenerator #1. Internal discharges were generated in A and C phases(C2 coupler) of hydrogenerator #1 and in A, Band C phases(C1 and C2 couplers) of hydrogenerator #2. Slot discharges occurred in A, Band C phases(C1 coupler) of hydrogenerator #1. The stator windings of two hydrogenerators were in good condition.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.274-277
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• 2003

Critical current(Ic) degradation of HTS tapes after bending is one of the hottest issues in HTS development and application studies. Many people are measuring Ic degradations for effect of bending radius. However even if the bending radius is larger than the breaking radius a HTS tapes can be damaged by repetitive bending, which is unavoidable in the winding processes. Therefore, We studied the Ic degradation after repetitive bending. at 77K with self-field, of Bi-2223 tapes processed by "Powder-in-Tube" technique, which was made by America Superconductor Corporation(AMSC) and superconductiing tapes that strain is imposed measured critical current by temperature difference of L$N_2$ and normal temperature. Like this, critical current could measure that degradation about 1~3％ by temperature difference. These results will amount the most important basis data in power electric machine of superconductivity cable, magnet, etc that winding work is require.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.17-20
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• 2002

In this paper voltage distribution in stator windings of induction motor driven by IGBT PWM inverter is studied. To analyze the irregular voltage of stator winding, equivalent circuit model of inverter-cable-motor was proposed and high frequency parameter is computed by using finite element method (FEM). Electro-magnetic transient program (EMTP) analysis of the whole system for induction motor and PWM inverter is proposed. Induction motor, 50[HP], and a switching surge generator was built to consider the voltage distribution. The results of EMTP analysis compared with experimental results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1445-1450
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• 2007

Induction motors are the main driving force of electric vehicles and operated by pulse width modulation (PWM) inverters in speed control. Contrary to full-voltage operation of induction motors, inverter-fed induction motors (IFM) generates transient overvoltages up to 10 kV/us and transient overvoltages accelerate the deterioration of winding insulation. We investigated transient overvoltages produced by the operation of IFM and analyzed its peak value and dv/dt depending on power cable length and operation frequency. The experimental results showed that transient overvoltages measured at the motor terminal increased with the cable length between inverter and motor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.72-75
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• 2001

전력케이블 선로에 가해지는 전압은 상시교류전압이외에 지락 등에 의한 사용주파과전압과 뇌써지와 같은 써지성 과전압이 있다. 써지성 과전압이 케이블 심선에 침입할 경우 종단접속부나 절연접속함의 접속점은 절연통 양단 및 시스와 대지간에 고전압이 발생하여 케이블심선-시스간 시스-대지간의 써지임피던스 비에 따라 과전압이 발생하며, 이와 같이 써지성 과전압이 방식층의 충격내전압치를 초과할 경우 방식층을 보호하기 위한 대책이 필요하며 그 보호장치로 절연통 보호장치를 사용하는 것이 일반적이다. 절연통에 대한 보호대책과, 설계 제작된 절연통 보호장치에 대한 주요시험항목을 실시하여 항목별 그 특성을 검토하고 절연통 보호장치의 지중송전선로에서 사용되는 조건인 열적내량을 검증하는 충격전류시험과 침수에 의한 기밀성능을 검증하는 내수성능시험을 실시함으로써 그 중요성을 인식할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.91-92
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• 2007

본 연구에서는 전력계통에서 발생되는 surge나 고장전류에 의해서 변압기의 고압측 코일에 유도되는 전자력의 크기를 유한요소 전자계해석 프로그램(FLUX2D)의 축대칭FEM을 이용하여 해석하였다. 1MVA, 22900/220(V) 단상 외철형 Cable형 변압기의 권선의 각방향의 전자력을 분석하고, 변압기 권선의 고유진동mode를 Transfer Matrix Method를 이용하여 Cable형권선의 고유진동주파수를 파악하고 ANSYS와 비교하였다. 변압기 권선의 전자력과 진동mode 분석결과는 변압기의 절연설계 및 단락기계력에 대한 프레임 구조 설계를 위한 자료로 활용될 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.604-607
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• 2000

뇌써지가 케이블 심선에 침입할 경우 케이블심선-시스간과 시스와 대지간의 써지임피던스 비에 따라 과 전압이 발생하며, 이와 같이 써지성 과전압이 방식층의 충격내전압치륵 초과할 경우 방식층을 보호하기 위 한 대책이 필요하며 그 보호장치로 절연통 보호장치를 사용하는 것이 일반적이다. 설계, 제작된 절연통 보호장치에 대해 절연저항시험, 동작개시전압시험, 뇌충격제한전압시험, 충격전류시험, 방전하에서 교류내전압시험, 절연성능시험 및 내수성능시험을 실시하여 내수성능시험을 제외한 모든 시험항목에서는 그 결과가 양호하나, 내수성능시험에서는 미세한 홈으로 물이 침투되어 불량이 발생함에 따라 절연통 보호장치는 지 중송전선로에 사용되는 보호장치로서 지중조건에서의 수밀 및 기밀특성 더욱 우수해야 하므로 내수성능시험의 중요성을 인식할 수 있었다.

• 한국안전학회지
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• 제33권3호
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• pp.15-20
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• 2018

There have been a number of major fatal fire accidents in Korea recently. The number of fires in 2017 were 44,178, which is not only increasing number of fires but also increasing in casualties. Particularly, the fire at Jecheon Sports Center, which suffered many casualties, is expected to have a huge impact. The cause of the fire has not been determined yet, but heat waves on the ceiling have also been pointed out. As such, the copper heating waves, which are used as a preventive measure against damage of pipes due to freezing of pipes, etc., always have a fire hazard. To determine the possibility of a flame-resistant heated fire, a positive electric cable product was used to artificially ignite and analyze the results. In case of a short circuit, the external covering of the positive electric cable is damaged, but not short circuit unless the heating material surrounding the wire is damaged. Due to the characteristics of heating cable for preventing copper waves, the chances of insulation becoming more severe due to moisture and temperature changes are higher than normal wires. If the internal heating system is carbonized by insulating deterioration without damage to the outer coating, it is likely to cause trekking, to form a winding loop in the heating materials, and to cause short circuit in the heated materials. For the positive temperature line, if the middle is shorted, the current continues to flow to the short circuit unless the breaker disconnects. Consequently, a heated fire that does not cut off the power immediately may leave multiple marks or cuts.