• Membrane Journal
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• v.32 no.5
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• pp.336-347
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• 2022

Reverse electrodialysis (RED) is one of the promising eco-friendly renewable energy technologies which can generate electricity from the concentration difference between seawater and freshwater by using ion-exchange membranes as a diaphragm. The ion-exchange membrane is a key component that determines the performance of RED, and must satisfy requirements such as low electrical resistance, high permselectivity, excellent durability, and low manufacturing cost. In this study, pore-filled anion-exchange membranes were fabricated using porous polymer substrates having various thicknesses and porosity, and the effects of ion-exchange polymer composition and membrane thickness on the power generation performance of RED were investigated. When the electrical resistance of the ion-exchange membrane is sufficiently low, it can be confirmed that the RED power generation performance is mainly influenced by the apparent permselectivity of the membrane. In addition, it was confirmed that the apparent permselectivity of the membranes can be improved through IEC, crosslinking degree, membrane thickness, surface modification, etc., and the optimum condition must be found in consideration of the trade-off relationship with electrical resistance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.349-356
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• 2002

For two kinds of 25Cr-20Ni stainless steels, STS310J1TB and STS310S with and without a small amount of Nb and N, creep behavior has been studied in a stress and temperature range from 147 to 392 MPa and from 923 to 773 K with a special reference to tertiary creep. The average creep life of STS310J1TB was about 100 times longer than that of the STS310S. The apparent activation energy for the initial creep rate was 330 kJ/mol in STS310J1TB, while that of the STS310S was 274kJ/mol in a power law creep region and 478 kJ/mol in a region of power law breakdown (PLB). The activation energy for STS310S below PLB is close to the for self-diffusion. When compensating for the temperature dependence of the Young's modulus and the omega value, it was found that the apparent activation energy for STS310J1TB was reduced to the activation energy for diffusion of chromium atom in gamma steel. The stress exponent of STS310S was about 12.3 above PLB and 5.1 in a power law creep region. Notwithstanding that the creep condition for STS310J1TB was in a power law creep region, its stress exponent was 7.9 larger than that of STS310S corresponding to the same creep conditions. This was ascribed to the presence of fine precipitates in STS310J1TB.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.117-122
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• 2001

For two kinds of 25Cr-20Ni stainless steels, SUS310J1TB TB and SUS310S with and without a small amount of Nb and N, creep behavior has been studied in a stress and temperature range from 147 to 392MPa and from 923 to 973K with a special reference to tertiary creep. The average creep life of SUS310J1TB was about 100 times longer than that of the SUS310S. The apparent activation energy for the initial creep rate was 330 kJ/mol in SUS310J1TB, while that of the SUS310S was 274 kJ/mol in a power law creep region and 478 kJ/mol in a region of power law breakdown (PLB). The activation energy for SUS310S below PLB is close to the that for self-diffusion. When compensating for the temperature dependence of the Young's modulus and the omega value, it was found that the apparent activation energy for SUS310J1TB was reduced to the activation energy for diffusion of chromium atom in a gamma steel. The stress exponent of SUS310S was about 12 above PLB and 5.1 in a power law creep region. Notwithstanding that the creep condition for SUS310J1TB was in a power law creep region, its stress exponent was 8.3 larger than that of SUS310S corresponding to the same creep conditions. This was ascribed to the presence of fine precipitates in SUS310J1TB.

• Proceedings of the KIEE Conference
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• summer
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• pp.220-223
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• 2004

This paper presents the new concept in ac power theory with non-sinusoidal waveform. It will be shown that there is discrepancy in the definition of active and complex power in the time and frequency domains when the conventional power theory is considered It will also be shown that the new power theory consistently defines the power quantifies in the time domains.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.4
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• pp.589-595
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• 2014

The error of instrument transformers is measured by connecting the external burden with the secondary terminal of the instrument transformers. Because the error of transformer is affected by the apparent power and power factor of the external burden, an accurate measurement of burden is important for transformer evaluation. We have developed the burden evaluation equipment for both potential transformer and current transformer by employing the series resistor in the range of $20m{\Omega}{\sim}5{\Omega}$ and the parallel resistor in the range of $1M{\Omega}{\sim}500{\Omega}$, respectively, together with visual basic program. We could reduce testing time more than 5 times by employing method developed in this study, compared with that developed in past. This method shows more better reliability by analyzing the evaluation results and fitting graphs of burden measurements. The test results of the developed system is compared with those obtained in the power meter analyzer to verify the validity.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.192-199
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• 2016

With changes in insulated defects, the environment, and so on, new partial discharge (PD) data are highly different from the original samples. It leads to a decrease in on-line recognition rate. The UHF signal and pulse current signal of four kinds of typical artificial defect models in gas insulated switchgear (GIS) are obtained simultaneously by experiment. The relationship map of ultra-high frequency (UHF) cumulative energy and its corresponding apparent discharge of four kinds of typical artificial defect models are plotted. UHF cumulative energy and its corresponding apparent discharge are used as inputs. The support vector machine (SVM) incremental method is constructed. Examples show that the PD SVM incremental method based on simulated annealing (SA) effectively speeds up the data update rate and improves the adaptability of the classifier compared with the original method, in that the total sample is constituted by the old and new data. The PD SVM incremental method is a better pattern recognition technology for PD on-line monitoring.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.290-293
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• 2001

This paper presents the reach accuracy of a distance relay for protection of transmission line according to power system conditions. The apparent impedance of distance relay is considerably affected by source impedance, load current, power factor, fault point and resistance etc. For protective coordination on the variables power system parameters, trip characteristics of distance relay at sending and receiving terminal are discussed.

• 연구논문집
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• s.30
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• pp.93-99
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• 2000

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. The electrical and rheological properties of zeolite based the ER fluids were reported. The electric field dependent yield stress are obtained from experimental investigation on the Bingham property of the ER fluid. Using ER fluids, it is possible to directly interface between electric drop and flow rate of the ER fluid was hydraulic control valve measured under application of an electric field. The purpose of the present study is pressure drop measurement of an ER valve by using strain gage. The performance characteristics of the valve system are evalusted in terms of pressrue fixed with respect to the intensity of employed electric fields and flow rates. As a result, it is esperimentally confirmed that pressure control valve using ER fluids applicable to use in hydraulic power systems.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.305-307
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• 2003

This paper presents an apparent impedance calculation procedure for distance relaying of transmission line involving FACTS (Flexible AC Transmission System) devices, particularly the UPFC (Unified Power Flow Controller), between Kangjin and Jangheung in Korea. With the changes of UPFC's parameters, the measurement and protective range (trip boundaries) of the adaptive distance relay can also be changed. So, it is the most important part in the field of system protection to analyze the operating characteristic of relaying system. The presence of UPFC significantly affects the trip boundaries which are also adversely affected by fault resistance combined with remote end infeed. This paper presents the apparent impedance calculations and the distance relay setting characteristics for faults involving the UPFC in the KEPCO system.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.363-372
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• 2008

In this paper, knowledge-based approach using Support Vector Machines (SVMs) are used for estimating the coordinated zonal settings of a distance relay. The approach depends on the detailed simulation studies of apparent impedance loci as seen by distance relay during disturbance, considering various operating conditions including fault resistance. In a distance relay, the impedance loci given at the relay location is obtained from extensive transient stability studies. SVMs are used as a pattern classifier for obtaining distance relay co-ordination. The scheme utilizes the apparent impedance values observed during a fault as inputs. An improved performance with the use of SVMs, keeping the reach when faced with different fault conditions as well as system power flow changes, are illustrated with an equivalent 265 bus system of a practical Indian Western Grid.