• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.216-221
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• 2000

This paper describes the analysis results on the PT ferroresonance at 154 kV GIS (gas Insulated substation by EMTP(Electro- magnetic Transient Program). We had simulated the PT ferroresonance between a potential transformer(PT) and an open circuit breaker's grading capacitance. The ferroresonance leads to very large power frequency overvoltages on PT bus and subsequent insulation failure. The large power can be supplied to the PT by the high voltage on the opened circuit due to the grading capacitance and equivalent capacitance of the buses during the ferroresonance. The damping circuit connected on the secondary winding were considered in the model. The actual countermeasure include a saturable inductor and a resistor series-mounted, but the 2 ohms of damping resistance was used in the computationl model.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2076-2079
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• 1999

This paper describes the analysis results on the PT ferroresonance at 154 kV GIS (gas Insulated substation by EMTP (Electro-magnetic Transient Program). We had simulated the PT ferroresonance between a potential transformer(PT) and an open circuit breaker's grading capacitance. The ferroresonance leads to very large power frequency overvoltages on PT bus and subsequent insulation failure. The large power can be supplied to the PT by the high voltage on the opened circuit due to the grading capacitance and equivalent capacitance of the buses during the ferroresonance. The damping circuit connected on the secondary winding were considered in the model. The actual countermeasure include a saturable inductor and a resistor series-mounted, but the 2 ohms of damping resistance was used in the computational model.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.234-234
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• 2013

The counter electrodes in dye-sensitized solar cells (DSSCs) play roles in not only collecting electrons from external circuit but also reducing I3- to I- in electrolytes. Generally, conventional counter electrodes for DSSCs are prepared from the high temperature treatment of the H2PtCl6 precursor solution at $400^{\circ}C$ However, the more simplified fabrication process of counter electrodes is required for the commercialization of DSSCs. In this work, we developed novel fabrication process of counter electrodes using nano-second pulsed laser. DSSCs employing counter electrodes prepared by laser process showed conversion efficiency of 6.75% with short-circuit current of 12.73 mA/cm2, open-circuit voltage of 0.74 V and fill factor of 0.72. Closer investigating of photovoltaic properties will be reported.

• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.69-74
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• 2010

Methodologies to improve photovoltaic performance of dye-sensitized solar cell (DSSC) are reviewed. DSSC is usually composed of a dye-adsorbed $TiO_2$ photoanode, a tri-iodide/iodide redox electrolyte and a Pt counter electrode. Among the photovoltaic parameters of short-circuit photocurrent density, open-circuit voltage and fill factor, short-circuit photocurrent density is the collective measure of light harvesting, charge separation and charge collection efficiencies. Internal quantum efficiency is known to reach almost 100%, which indicates that charge separation occurs without loss by recombination. Thus, light harvesting efficiency plays an important role in improvement of photocurrent. In this paper, technologies to improve light harvesting efficiency, including surface area improvement by nano-dispersion, size-dependent light scattering efficiency, bi-functional nano material, panchromatic absorption by selective positioning of three different dyes and transparent conductive oxide (TCO)-less DSSC, are introduced.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.11
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• pp.1434-1444
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• 1995

Current test has recently been known to be a promising testing method in CMOS VLSI because conventional voltage test can not make sure of the complete detection of bridging, gate-oxide shorts, stuck-open faults and etc. This paper presents a new BIC(built-in current sensor) for the internal current test in CMOS logic circuit. A single phase clock is used in the BIC to reduce the control circuitry of it and to perform a self- testing for a faulty current. The BIC is designed to detect the faulty current at the end of the clock period, so that it can test the CUT(circuit under test) with much longer critical propagation delay time and larger area than conventional BICs. The circuit is composed of 18 devices and verified by using the SPICE simulator.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.4
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• pp.30-35
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• 1983

Numerical calculations have been made about the phase differences of the short circuit current in a solar cell according to the variation of the modulation frequency. The phase differences in short circuit current of the solar cell exposed to the modulated light source is measured experimentally. From the above two results, the minority carrier lifetime has been determined. Also, minority carrier lifetime has been determined from the observed photo-induced open circuit voltage decay wave form that follows termination of the excitation.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.44-50
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• 1996

In this study, Selenium device was fabricated by vacuum evaporation method with the substrate temperature at room temperature and its electrical and optical properties were investigated to be used in optical device. The film properties largely depended on the transmittance and annealing time, and improved with aging owing to stress release. We found that the photocurrent of the films increase linearly with light illumination. As a result, Selenium device made by this method yielded a short circuit current density of 10.5mA/$\textrm{cm}^2$, an open circuit voltage of 39OmV.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.1
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• pp.23-29
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• 2005

This paper presents the characteristics of leakage currents flowing through ZinC Oxide(ZnO) surge arrester blocks under mixed direct and 60 Hz alternating voltages. A mixed voltage, in which an alternating voltage is superimposed upon a direct voltage, appears on the HVDC system network. The mixed direct and alternating voltage generator with a peak open-circuit of 10 kV was designed and fabricated. The leakage currents and V-I curves for the fine and used ZnO surge arrester blocks were measured as a function of the voltage ratio k, where the voltage ratio k is defined as the ratio of the peak of alternating voltage to the peak of the mixed voltages. The resistive component in the leakage current in the low conduction region is significantly increased with increasing the voltage ratio k. The V-I characteristic curves for the mixed voltages lies between the direct and alternating characteristics, and the cross-over phenomenon in the high conduction region was appeared.

• Proceedings of the KIEE Conference
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• summer
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• pp.205-207
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• 2004

This paper proposes a new SSHG(Sag/swell and Harmonic Generator) injecting voltage by using series inverter. The proposed SSHG composes series inverter, DC capacitor as energy storage, rectifier and voltage clamp circuit. This SSHG is designed to generate typical power disturbances, such as voltage sag/swell, over/under voltage and voltage flicker. Also it is designed to generate unexpected voltage phase jumping waveform by controlling the series inverter. In this paper, three kinds of control methods for the proposed 2MVA SSHG are given. Typical voltage sag and swell waveforms are implemented by adopting simple control method. Also the voltage flicker is generated by changing the amplitude of the injected voltage in random. Owing to the limited bandwith of the proposed SSHG, high frequency transient waveforms can be obtained by using the open loop control. The simulation and experimental results are given to verify the operation of the proposed SSHG, Finally, conclusions are given.

• Korean Journal of Materials Research
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• v.24 no.7
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• pp.375-380
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• 2014

Solar cells exhibit different power outputs in different climates. In this study, the temperature dependence of open-circuit voltage(V-oc), short-circuit current(I-sc), fill factor(FF) and the efficiency of screen-printed single-crystal silicon solar cells were studied. One group was fabricated with homogeneously-doped emitters and another group was fabricated with selectively-doped emitters. While varying the temperature (25, 40, 60 and $80^{\circ}C$), the current-voltage characteristics of the cells were measured and the leakage currents extracted from the current-voltage curve. As the temperature increased, both the homogeneously-doped and selectively-doped emitters showed a slight increase in I-sc and a rapid degradation of V-oc. The FF and efficiency also decreased as temperature increased in both groups. The temperature coefficient for each factor was calculated. From the current-voltage curve, we found that the main cause of V-oc degradation was an increase in the intrinsic carrier concentration. The temperature coefficients of the two groups were compared, leading to the idea that structural effects could also affect the temperature dependence of current-voltage characteristics.