• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권9호
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• pp.522-529
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• 2002

In this paper, computer simulations of the physical Phenomena occurring in the arc region before and after current zero were carried out to evaluate the thermal recovery characteristics of a Laval nozzle. A commercial CFD program "PHOENICS" is used for the simulation and the user-coded subroutines to consider the arcing phenomena were added to this program by the authors. The computed results were verified by the comparison with the test results presented by the research group of GE Co.(General Electric Company). In order to investigate the state of the arc region after current zero, the simulation was carried out with three steps. They are steady state arc simulation, transient arc simulation before current zero, and transient hot-gas flow simulation after current zero. The semi-experimental arc radiation model is adapted to consider the radiation energy transport and Prandtl's mixing length model is employed as the turbulence model. The electric field and the magnetic field were calculated with the same grid structure used for the simulation of the flow field. The post-arc current was calculated to evaluate the thermal recovery characteristics after current zero. Compared with the results obtained by GE Co., it has been found that the critical RRRV(ratio of rise of recovery voltage) will be determined previously by this study.his study.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권2호
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• pp.76-82
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• 2005

In this paper, a method for analyzing the thermal recovery characteristics of the nozzle of gas circuit breaker was described. In order to obtain thermal recovery characteristics, the transient simulation of SF6 arc plasma within the nozzle was carried out. In particular, the nozzle ablation was taken into account by simultaneously solving the PTFE concentration equation with the governing equations such as continuity, momentum and energy equation. After that, post arc current calculation was performed with the rate of rise of recovery voltage changed. From the calculated post arc current, it was possible to suggest the thermal recovery characteristics of the nozzle of gas circuit breaker.

• 전력전자학회논문지
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• 제3권3호
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• pp.222-230
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• 1998

본 논문에서는 스너버 회로를 사용하지 않고 턴-온시 역회복 전류의 영향과 턴-오프 시 구동되는 IGBT에 발생하는 과전압을 제한할 수 있는 새로운 IGBT 게이트 구동회로를 제안한다. 제안하는 턴-온 게이트 구동기법은 턴-온 지연 시간을 증가시키지 않고 게이트-에이터 전압이 문턱전압 이상이 되면 IGBT의 입력 커패시턴스를 증가시킴으로써 게이트-에이터 전압의 증가율을 감소시키는 특징을 갖는다. 제안하는 턴-오프 게이트 구동기법은 전류의 크기에 따라 과전압을 제한하여 단락사고와 같은 대전류가 흐르는 경우 더욱 효과적으로 과전압을 제한하는 특징을 가진다. 또한, 여러 가지 조건에서 실험을 수행하여 제안한 IGBT 게이트 구동회로의 타당성을 검증한다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.361-365
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• 2004

This paper describes the various characteristics of voltage sags which can affect the functions of three-phase induction motors that are mostly used in the power distribution systems. These assorted characteristics include motor speed losses, voltage recovery, motor reacceleration, and transient characteristics. An experimental study on the induction motor behaviors was also carried out to confirm these impacts. In addition sequential voltage sags with short durations were considered and investigated. The results show that the occurrence of the second voltage sag after the first one may affects the induction motor adversely.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.106-109
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• 2003

This paper describes the various characteristics of voltage sags and temporary interruptions which can affect the functions of 3-phase induction motors. These assorted characteristics include motor speed loss, voltage recovery, motor reacceleration, and transient characteristics. An experimental study on induction motor behavior was also carried out to confirm these impacts. Besides, sequential voltage sags of short duration were considered for this paper. The results show that the occurrence of the second voltage sag after the first one may affects the induction motor adversely.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.45-47
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• 2004

This paper describes the various characteristics of voltage sags which can affect the functions of three-phase induction motors that are mostly used in the power distribution systems. These assorted characteristics include motor speed losses, voltage recovery, motor reacceleration, and transient characteristics. An experimental study on the induction motor behaviors was also carried out to confirm these impacts. In addition, sequential voltage sags with short durations were considered and investigated. The results show that the occurrence of the second voltage sag after the first one may affects the induction motor adversely.

• 한국태양에너지학회 논문집
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• 제23권3호
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• pp.29-35
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• 2003

Generator for wind power can be either synchronous or asynchronous (induction) types. Induction and synchronous generators behave in a different way when subjected to severe faults. Induction generators does not have an angle stability limit and short circuit in the neighborhood of an Induction generator causes the demagnetization of the machine when the fault is cleared, the voltage raises slowly, while the grid contributes with reactive power to the generator and the magnetic flux recovers. On the other hand in the synchronous generators the recovery of the voltage is immediate, since the excitation of the rotor angle comes from an independent circuit. This paper shows the result of the transient state analysis in the network connected to wind generation system Several case studies have been conducted to determine the effect of the clearing time of a fault on the network stability. It has been found that the critical clearing time can be as low as 61ms in the case of induction generator compared to 370ms in the case of synchronous generator.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1350-1352
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• 1995

This paper discribed the characteristic of I-t cross-over-point between current limited-fuse and explusion fuse(Bay-O-Net Fuse) and fuse protection in pad-mounted transformer that was generated internal faults and the short circuit of secondary side(load side). In the I-t cross-over-point, current limited fuse was melted when transient recovery voltage was raised rapidly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.236-240
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• 1988

The simplified equivalent by using the short circuit impedance has been used for analyzing the prospective transient recovery voltage of the large power system. But it sometimes generates untorelable error in the rate-of-rise of TRV when using the Thevenin equivalent source. This paper provides the new equivalent by using the multi-port theory. The application of the new method to the sample system gives satisfactory accuracy compared with the short-circuit equivalent.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.369-371
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• 1999

The post-arc current in VCB(Vacuum Circuit Breaker) was calculated from the transient recovery voltage. A differential equation for the post-arc current was derived from the equivalent circuit of the test circuit. And it's results were showed.