• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1856-1858
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• 2000

This paper describes the principles of reignition system which has newly been developed and used as KERI's high power testing facilities. Synthetic short-circuit testing method is generally adopted to perform the short-circuit test of the ultra high-voltage circuit breakers, which consists of two separated sources such as the current source from short-circuit generator and the voltage source from charged energy in capacitor. And, in case of synthetic short-circuit test, it will be necessary to use the reignition system in order to extending the arcing time of the circuit breaker and provide the arc energy equivalent to the direct testing method.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2006년도 춘계 학술발표회 논문집 제3권1호(통권3호)
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• pp.142-152
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• 2006

The purpose of this study is to explore an inquisitive and innovative approach to structure and form, Calatrava's morphogenetic mechanism and to trace the ideas behind his working methods and his theoretical preoccupations. The bridges and buildings of S. Calatrava possess a breathtaking rhythm and of them some are designed to expand and contract like living organisms. The analogy Calatrava has used as a creative tool to mutate human bodies into arcing roof forms and bridge suspensions is introduced to illustrate the morphogenetic process. At the same time, the analysis used developing how to design frame structures foldable with brilliant mathematical solution is also investigated. Consequently, the potentialities of Calatrava's morphogenetic mechanism to invent new systems are generated by methodological hypothesis; analysis and analogy.

• Journal of Welding and Joining
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• 제24권3호
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• pp.42-48
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• 2006

Since the voids occur at the CD stud welds, the mechanism of void formation and void reduction method are investigated in this work. It is speculated that the voids are formed because of high short-circuit current above 1000A. When the simple flow model is used to estimate the void trapping condition, the most voids are trapped at the weld mainly due to fast cooling rate of the CD stud weld. Since it is almost impossible to remove the voids completely, a method is proposed to reduce the void by decreasing the short-circuit current at the end of the arcing time. The experimental results show that the void is reduced by decreasing the short-circuit current to 1000A.

• 전기학회논문지
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• 제62권4호
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• pp.573-576
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• 2013

In this paper, analysis method for current collection performance based on real-time current of catenary system is proposed. An innovative method based on track-side of railway system is used for measurement of currents for overhead contact line during the collection with pantograph. The evaluation of a qualitative ratio for current collection performance were conducted using proposed algorithm under various conditions such as laboratory and track-side. To check the validity of our approach, we compared between calculation results from current of contact wire and measurement results from arcing of pantograph using simulator in laboratory conditions. The results show that the behavior of current collection performance were analysis from currents of overhead contact line in AC electric railway system.

• 전기학회논문지
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• 제67권7호
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• pp.981-986
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• 2018

AC(alternating current) CB(circuit breaker) at the fault occurred in the existing AC distribution system is limiting the fault current through zero cross-point. However, DC(direct current) CB does not have zero cross-point. Therefore, arc occurred by on-off operation of DC CB is very huge. Nowadays, many research team are studying the way to decrease breaking time, which is one of the essential conditions in DC CB. We suggested novel arc-induction type DC CB in this paper. The proposed arc-induction type DC CB is composed of the mechanical Arc ring and DC CB. We confirmed the operation of arc-induction type DC CB through the HFSS(High Frequency Structure Simulator) 3D simulation program and performed the experiment for operation characteristics. Results showed that arcing time of the arc-induction type DC CB by using induction ring was faster than existing mechanical DC CB. On the transient system, we confirmed stable operation characteristics of the arc-induction type DC CB through the simulation and experimental results. We expect that the proposed arc-induction type DC CB technology is will go to stay ahead of the existing DC CB technology.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.283-285
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• 2005

This paper presents a new two-terminal numerical algorithm for fault location estimation and for faults recognition using the synchronized phasor in time-domain. The proposed algorithm is also based on the synchronized voltage and current phasor measured from the PMUs(Phasor Measurement Units) installed at both ends of the transmission lines. Also the arc voltage wave shape is modeled numerically on the basis of a great number of arc voltage records obtained by transient recorder. From the calculated arc voltage amplitude it can make a decision whether the fault is permanent or transient. In this paper the algorithm is given and estimated using DFT(Discrete Fourier Transform) and the LES(Least Error Squares Method). The algorithm uses a very short data window and enables fast fault detection and classification for real-time transmission line protection. To test the validity of the proposed algorithm, the Electro-Magnetic Transient Program(EMTP/ATP) and MATLAB is used.

• Journal of Welding and Joining
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• 제17권3호
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• pp.36-43
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• 1999

The effect of Si content in welding wires on spattering characteristics and droplet transfer phenomena was studied. In MAG welding using 80% Ar-20% $CO_2$ shielding gas, spattering characteristics and droplet transfer phenomena were varied with Si content of wire. With increasing Si content, the spattering ratio and the ratio of large size spatter $(d\geq1.0mm)$ were increased. The increase of Si content in molten metal made surface tension increase due to reduction of oxygen content, which resulted from deoxidizing action of silicon. The increase of surface tension resulted in unstable transfer phenomena and arc instability in both short circuit and spray region. With changing Si content of wire, spattering characteristics and droplet transfer phenomena was directly influenced by the variation of surface tension, compared with the effect of arc stability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1422-1423
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• 2006

In our study, the PTFE nozzle ablation in the high-voltage self-blast type $SF_6$ gas circuit breaker was investigated. The test circuit breaker has the structure that the pin electrode is moving and the pressure reservoir volume and the dimension is almost same as commercial 145kv 40kA circuit breaker for similar result in real circuit breaker. The variation of current and arcing time was the range of $36kA_{rms}$(symmetry) - $40kA_{rms}$(asymmetry) and 10-16 ms. From the measured data the tendecy of the mass loss of the nozzle to current load and arc energy was estimated. In this process, the distance from the arc to nozzle(PTFE) surface, area which was exposed to arc and stroke contour was considered. These results will be used to enhance the accuracy of the computational fluid dynamics analysis in circuit breaker and estimate the residual life time of a circuit breaker.

• 한국광물학회지
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• 제27권2호
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• pp.73-83
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• 2014

마이크로웨이브 가열에 의하여 선택적으로 상변환을 일으키는 Au를 함유하는 황화광물을 조사하기 위하여 현미경과 SEM-EDS 분석을 수행하였으며 그리고 이에 따른 최대 Au 용출인자를 결정하기 위하여 티오시안산염 용출실험을 수행하였다. 비-가시성 Au를 함유하는 황화광물을 마이크로웨이브에 노출시킨 결과, 노출시간이 증가할수록 온도와 무게감소가 증가하였다. 이 황화광물 중 마이크로웨이브 가열에 가장 빠르게 선택적으로 상변환 된 광물은 황비철석이었다. 황비철석이 적철석으로 상변환되었으며, 상변환은 동심원적과 가장자리구조로 형성되었다. 또한 상변환 된 부분에서 O와 C가 검출되었으며, 일정하게 Fe 함량은 높게 그리고 As 함량은 낮게 나타났다. 이와 같은 결과는 마이크로웨이브 가열에 의한 arcing과 산화작용이 일어났기 때문이다. 마이크로웨이브에 35분 노출시킨 시료를 티오시안산염 용출실험에 적용하여 Au가 최대로 용출되는 조건은 0.5 g의 티오시안산나트륨 농도, 2.0 M의 염산 농도, 0.3 M의 황산구리 농도 그리고 용출온도$60^{\circ}C$에서였다. 최대 Au 용출 조건을 마이크로웨이브 처리 시료에 적용했을 때 Au 용출률이 59%에서 96.96%로 나타났지만 마이크로웨이브에 처리하지 않은 시료에서는 겨우 24.53%에서 92%로 나타났다.

• 조명전기설비학회논문지
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• 제28권9호
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• pp.8-13
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• 2014

Currently it is major problem of electric railway with increasing drive speed such as the arc generated by the pantograph detachment and the distortion current in the motor-block high speed switching. When physical contact between the pantograph and the catenary line is separated, the pantograph detachment arcing occurs and it makes up the conductive noise to the return feeder. We made the EMTP modeling of the railway traction system and the pantograph arc by circuit elements and switches. The influence of pantograph detachment frequency is investigated by changing some frequencies. The over-current occurs in each detachment and it oscillates some time at beginning and stabilizes gradually. The magnitude of over-current is decided by instantaneous value of existing traction return current. If the detachment occurs at a point of peak value or distortion current, the over-current will be more harmful to the power systems connected with the return feeder and will become to arise with increasing detachment frequency.