• Proceedings of the KIEE Conference
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• 2000.07c
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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.

• Proceeding of KASS Symposium
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• 2006.05a
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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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• v.24 no.3
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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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.

• Proceedings of the KIEE Conference
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• 2005.11b
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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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• v.17 no.3
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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.

• Proceedings of the KIEE Conference
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• 2006.07c
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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.

• Journal of the Mineralogical Society of Korea
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• v.27 no.2
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• pp.73-83
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• 2014

In order to investigate selective phase transformations and to determine the maximum Au leaching factors from microwave treated Au-bearing complex sulfides, a microscope, SEM-EDS analysis, and thiocyanate leaching tests were performed. When the Au-bearing complex sulfides were exposed to microwave heating, increasing the microwave exposure time increased temperature and decreased weight. Arsenopyrite was first selectively transformed to hematite, which formed a concentric rim structure. In this hematite, oxygen and carbon was detected and always showed high iron content and low arsenic content due to arcing and oxidation from microwave heating. The results of the leaching test using microwave treated sample showed that the maximum Au leaching parameters was reached with 0.5 g concentration thiocyanate, 2.0 M hydrochloric acid, 0.3 M copper sulfate and leaching temperature at$60^{\circ}C$. Under the maximum Au leaching conditions, 59% to 96.69% of Au was leached from the microwave treated samples, whereas only 24.53% to 92% of the Au was leached from the untreated samples.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.9
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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.