• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
• /
• pp.357-364
• /
• 1997

In this experiment high-strength concrete of good workability is made by means of either replacing unit cement quantity to fly-ash by 20% or using low heat cement to reduce the internal hydration heat suggested as the fault of concrete. Concrete is poured through ready mixed concrete to test the ability of applying to the substantial works and is carried out the test of flowing and core strength and record of temperature of imitating specimens. It is capable to apply high-strength concrete replaced to fly-adh 20% to the substantial works through the experiment

• 대한전기학회논문지:전력기술부문A
• /
• 제49권9호
• /
• pp.446-450
• /
• 2000

A conventional variable percentage current differential relaying algorithm for bus protection may misoperate for external faults with severe CT saturation and internal faults with high impedance. This paper proposes a percentage differential current relaying algorithm for bus protection combined with a compensating algorithm of secondary currents of CTs. Even though CTs are saturated and their secondary currents are severely distorted, the proposed relaying algorithm does not only misoperate for external faults with CT saturation but also detects the internal faults with high fault impedance. Thus, the method improves the sensitivity of the relays and does not require any counterplan for CT saturation.

• 전자통신동향분석
• /
• 제8권3호
• /
• pp.39-52
• /
• 1993

This study involves a Common Cause Failure (CCF) problem on the ultra-high reliability required system development such as war game operations, nuclear power control, air traffic control, space shuttle missions, and large scale network communication system. The system situation problems are defined according to CCF, reliability and system fault identifications for the development cast verifications in the multi-version redundant software system. Then, CCF analysis of redundant system, system principles and statistical dependence are also described. This validation oh the CCF in the human software interaction system will notify software engineers to conceive what really is CCF contribution factor, not only the internal but the external ones.

• 한국전기전자재료학회논문지
• /
• 제14권7호
• /
• pp.578-583
• /
• 2001

The bushing for high voltage and large and power should endure weight of itself and force of pushing from contact with circuit breaker. Like this, epoxy mold bushing has to be strong without fault. However, the external circumstances and internal factors was caused by partial discharge, flashover and dielectric breakdown. Therefore, to remove external factor of defect and to prevent the internal cracks and cavity generated from the contraction on interface of Cu-Epoxy, we should form semi-conductive layer on Cu bar by carbon. Then, the PD properties and the insulation qualities of epoxy mold type bushing was able to improved by roles of cushions for the direction of diameter and by effects fo natural sliding like as separated from conductor for the direction of length. So, in this work, we could prove the method of semi-conductive layer in making the long conductor.

• 한국지능시스템학회논문지
• /
• 제8권5호
• /
• pp.72-82
• /
• 1998

Power transformer protective relay should block the tripping during magnetizing imrush and rapidly operate the tripping during internal faults. But traditional approaches maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmounic component. To enhance the fault detection sensitivities of conventional technuques, flux-differential current derivative curve by fuzzy theory approaches is used. This paper deals with fuzzy logic based protective relaying for power transformer. The proposed fuzzy based relaying algorithm consisits of flux-differential current derivative curve, harmonics restraint, and precentage differential characteristic curv. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.

• KIEE International Transactions on Power Engineering
• /
• 제2A권4호
• /
• pp.153-159
• /
• 2002

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. Recently, the frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. And then, traditional approaches will likely be maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from EMTP simulation package and showed a fast and accurate trip operation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 하계학술대회 논문집 B
• /
• pp.606-609
• /
• 1995

This paper presents discriminate between magnetizing inrush and internal faults of power transformer by artificial neural networks trained with preprocessing of fault discriminant. The proposed neural networks contain multi-layer perceptron using back-propagation learning algorithm with logistic sigmoid activation function. For this training and test, we used the relaying signals obtained from the EMTP simulation of model power system. It is shown that the proposed transformer protection system by neural networks never misoperated.

• 대한전기학회논문지:전력기술부문A
• /
• 제50권4호
• /
• pp.157-165
• /
• 2001

The two criteria to identify the disturbances of the power transformer has been reported in this paper. They have been derived through EMTP simulations of internal faults, inrush and overexcitation for the model of 154/22.9[kV], 40[MVA], Y-Y three-phase power transformer. We propose the crisp algorithm which uses two criteria. A series of test results clearly indicate that the method can identify not only an internal fault but also the other transients. The average of relay operation times is about 7.2[ms]. The proposed algorithm immunes to the transient state.

• 조명전기설비학회논문지
• /
• 제23권1호
• /
• pp.85-91
• /
• 2009

본 논문에서는 배전계통에 사용되는 케이블 권선형 변압기에 전력계통에서 발생되는 서지나 고장전류에 의해서 변압기의 고압측 코일에 유도되는 전자력의 크기를 유한요소 전자계해석 프로그램(FLUX2D)을 이용하여 해석하고, 기계진동방정식을 이용하여 케이블형 권선의 고유진동주파수를 분석하였다. 변압기모델로서 1(MVA), 22,900/220([V]) 단상 외철형 Cable형을 선정하여, 권선의 각방향의 전자력을 분석하고, 고유진동 mode를 Transfer Matrix Method를 이용하여 계산하고 상용 프로그램(ANSYS)을 이용하여 분석한 결과와 비교하였다. 진동모드의 분석한 결과 제시한 수치해석 방법은 공학적인 오차범위 안에서 충분히 수용할 정도의 정확도를 보여주었다. 변압기 권선의 전자력과 진동모드 분석결과는 변압기의 절연설계 및 단락기계력에 의한 절연 구조 설계를 위한 유용한 자료로 활용될 수 있다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
• /
• pp.1203-1204
• /
• 2006

Recently, utility network is getting more and more complicated and huge. In addition to, demands of power conversion devices which have non-linear switching devices are getting more and more increased. Consequently, according to the non-linear power semiconductor devices, current harmonics are unavoidable. Those current harmonics flow back to utility network and become one of the reasons which make the voltage distortion. On the other hands, voltage sag from sudden increasing loads is also one of the terrible problems inside of utility network. In order to compensate the current harmonics and voltage sag problem, AF(Active Filter) systems could be a good solution method and SMES(Superconducting Magnetic Energy Storage) system is a very good promising source due to the high response time of charge and discharge. Therefore, the combined system of AF and SMES is a wonderful device to compensate both harmonics current and voltage sag. However, unfortunately SMES needs a superconducting magnetic coil. Because of the introduction of superconducting magnetic coil, quench problem caused by unexpected reasons is always existed. In case of discharge operation, quench is a significantly harmful factor according as it decreases the energy capacity of SMES. Therefore, this paper presents a decision method of the specification of the AF-SMES system considering internal fault condition. Especially, authors analyzed the change of the original energy capacity of SMES regarding to the size of resistance caused by quench of superconducting magnetic coil. Finally, based on this simulation, authors manufactured actual Active Filter System using DSP.