• 전기학회논문지
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• 제62권6호
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• pp.737-743
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• 2013

This paper describes the overvoltage through lightning surge analysis on underground system in DC combined distribution systems. It is considered that operating micro grid including distributed generation with smart grid can make possibility of composing new distribution system different from existing one. However, there are many papers about low voltage DC distribution in grids or buildings but not many about replacement or distributing 22.9kV AC distribution system to DC system. Among many research need for DC system development, overvoltage is studied in this paper. Overvoltage is simulated on DC cable when lightning strikes to overhead grounding wire which is installed at the nearest location from power cable section. Analysis as well as modeling is performed in EMTP/ATPDraw. It is evaluated that analysis results can be used to design of DC underground distribution power cable system.

• 전기학회논문지
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• 제59권11호
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• pp.1949-1955
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• 2010

This paper describes the characteristic and effectiveness of combined GIL transmission line through lightning surge analysis. In addition the XLPE cable is analyzed in the same condition to compare with GIL. Lighting surge analysis is carried out by EMTP/ATP-Draw to obtain overvoltage of GIL and XLPE cable at service-point and load-out area of underground line. Propagation velocity is calculated in combined transmission lines with GIL and XLPE cable. The overvoltage is also analyzed on GIL and XLPE cable with or without arrester operation. The Analysis results show that overvoltage of GIL is occurred higher than XLPE cable at the same condition. Therefore it is evaluated that the application of GIL at the field should be considered cautiously when more detailed transient analysis, another electrical testes and economic evaluations are implemented.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.628-634
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• 2014

This paper investigates the transient characteristics of grounding systems used in under-ground distribution power cables. Recently, two kinds of grounding system are used for underground distribution cables in Korea. The first one is conventional multi-point grounding system, the other is newly proposed non-bundled common grounding system. The non-bundled common grounding system has an advantage the decreasing the power loss due to decrease of the shield circulation current. In this paper, the lightning overvoltage induced in neutral wire (in case of non-bundled common grounding system, overvoltage between opened neural wires and grounding in each phase) of these two kinds of grounding systems are estimated and compared by field tests and EMTP simulations. The EMTP simulation methods are firstly verified by comparison of measurement and simulation. Finally, the insulation level against lightning is expected by EMTP simulation results using verified model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.279-281
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• 1998

This paper present overvoltage induced on distribution power line by lightning surge. It is important problem that overvoltage threatens credit and security of the power system. In this paper induced overvoltage was calculated. From the line being modeled in really actual practice. Also, the proper suppressing effects of a surge arrester against lightning induced voltages were suggested.

• 전기학회논문지
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• 제64권11호
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• pp.1543-1550
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• 2015

Ferroresonance is a non-linear vibrational phenomenon that is generated by the electrical interaction of the inductance component with the capacitor component of a certain capacitance as the device of the inductance component such as a transformer is saturated due to the degradation, the waveform distortion of current and voltage, and the oscillation of overcurrent and overvoltage in a system. Recently, ferroresonance was generated from the waveform distortion of current and voltage, or the overvoltage or undervoltage phenomenon caused by the nature of an electrical power system and design technology of the transformer in the three phase transformer system. Hence, in general, ferroresonance analyzed by converting to the LC equivalent circuit. However, in general, the aforementioned analytical method only applies to the resonance phenomenon that is generated by the interaction of the capacitance of bussbar and grounding, and switching as the capacitor component with PT and the transformer as the inductance component in a system. Subsequently, the condition where ferroresonance was generated since overvoltage was supplied as line voltage to the phase voltage and thus the iron core is saturated due to the interconnection between grounded and ungrounded systems could not be analyzed when single phase PT was connected in a ${\Delta}$/Y connection system. In this study, voltage swell in the configuration of grounded circuit of a step-up transformer with the ${\Delta}-{\Delta}$ connection linked to PT for control power and the ferroresonance generated by overvoltage when the line voltage of the ${\Delta}-{\Delta}$ connection was connected to the phase voltage of the grounded Y-Y connection were analyzed using PSCAD / EMTDC through the failure case of the transformer caused by ferroresonance in the system with the ${\Delta}-{\Delta}$/Y-Y connection, and subsequently, the preventive measure of ferroresonance was proposed.

• 전기학회논문지
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• 제60권5호
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• pp.999-1004
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• 2011

Nowadays, it is becoming difficult to secure a transmission line route when a new transmission line is constructed due to social environment and resident complaints. As existing urban areas are expanded and new cities are constructed, the necessity of high-capacity underground power transmission has been increasing because of load concentration in downtown areas. In North America, Europe and Japan, the research has been carried out for 2nd generation gas insulated transmission lines(GIL) which is more environmentally friendly and economical compared to previous GILs. The new GILs have been applied to real power systems from early 2000s. In South Korea, GIL is being considered as a possible solution for replacing 345kV high-capacity overhead transmission lines with underground transmission ones, so KEPCO is planning to develop and apply a new 362kV rated GIL underground transmission lines instead of overhead transmission lines. In this paper, the overvoltage generated at the combined transmission line adapting GIL was reviewed using EMTP.

• 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.

• 대한전기학회논문지:전력기술부문A
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• 제51권2호
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• pp.102-108
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• 2002

This paper describes the overvoltage analysis and reduction methods of insulation joint boxes in underground transmission power cables when direct lightning surge strikes to overhead transmission line. An actual 154kV combined transmission line with underground Power cables was modelled in ATPDraw for simulation. Simulations were performed to analyze the overvoltage between insulation joint boxes, sheath-to-ground voltage according to the distance between cable conductors, cable lengths, burying types, CCPU connection types. The most effective method to reduce the induced overvoltage of Insulation joint boxes was proposed. It is evaluated that the proposed reduction method riven from the detailed simulations can be effectively applied to the actual underground power cable systems.

• 전력전자학회논문지
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• 제14권6호
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• pp.514-521
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• 2009

본 논문은 다이오드 클램프형 3-레벨 IGBT 인버터에 적용 가능한 새로운 방식의 과전압 방지 스너버에 관한 것이다. 일반적으로 전력변환장치는 스위칭 소자에 발생하는 과전압을 감소시키기 위해 스너버 회로를 포함하고 있다. 하지만 다이오드 클램프형 멀티레벨 인버터는 스위칭 소자가 직렬로 연결되어 있기 때문에 과전압 방지 스너버를 구성하기 힘든 문제점이 있다. 본 논문에서는 스텝-다운 DC-DC 컨버터에 적용 가능한 과전압 방지 스너버의 특성을 이용하여 다이오드 클램프형 3-레벨 인버터에 과전압 방지 스너버를 구성하려 할 때 발생하는 문제점을 분석하고 분석 결과를 토대로 다이오드 클램프형 3-레벨 인버터에 적용할 수 있는 새로운 구조의 스너버를 제안하였다. 제안한 방식에 대한 특성을 해석하였고, 실험을 통하여 효용성을 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전력기술부문
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• pp.78-80
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• 2007

The residual flux in transformer's iron cores leads to a distortion of short-circuit current occasionally. And some considerable distortion may have effect on the validation of the test results. To avoid the substantial distortion, a suitable pretest is performed before the actual test. In case of applying this method there must be excessive overvoltage due to switching of an unloaded transformer and chopping of an excitation current. The purpose of this paper is estimate that the effect of the overvoltage results from this phenomenon on insulation performance of short-circuit transformer.