• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.353-356
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• 2015

Due to high oil prices, environmental pollution, the study of electric vehicles have been actively promoted. Charger for the electric vehicle is being developed using wireless rather than cable options. In this paper, we got more efficiency from using a superconducting transmission coil compared to using a normal coil. We implemented a wireless power transmission system using a magnetic induction at a frequency of 63.1 kHz. For comparison, a transmitter was designed using a superconducting coil and a normal coil. In addition, a receiver used a normal coil to apply for electric vehicles. The applied voltage and current were12 V and 5 A. Efficiency at a distance of 40 ~ 80 mm was measured. As a result, the superconducting transmission coil had a higher efficiency than the normal transmission coil. However, the receiving coil should be normal conductor for stable operation considering that it was put in moving electric vehicle. The efficiency was increased to 44 % at a distance of 40 mm when the diameter of normal receiving coil was 120 mm.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.337-338
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• 2008

KEPCO has built, for the first time in the world, 765㎸ double circuit transmission lines which use vertically arranged phase conductor, while 765㎸ transmission lines in other countries are single circuit lines and use horizontally arranged phase conductor. System operating voltage, switching overvoltage, and lightning overvoltage were considered in determining the air gap. Recently, however, lightning outage rate of some 765㎸ transmission lines in KOREA shows that it is more than what is expected. Lightning fault of 765㎸ transmission lines is mostly single phase grounding fault which can be reclosed. But it still needs to be carefully managed, for the bulk system like 765㎸ transmission lines have huge effects on whole power system. This paper introduces analysis and countermeasure of KEPCO's 765㎸ transmission line lightning outage.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2020-2022
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• 2000

The cross-linked polyethylene(herein after XLPE) insulated power cable emit the methane($CH_4$)gas in the course of chemical cross-linking process. The general stranded conductor easily discharge this methane gas through the gap of each stranded wires. But the special stranded conductor that filled with semi-conducting rubber compound to prevent water penetration which is applied to water proof type of cable(22.9kV CN/CV-W), disturb the methane gas emission. The pre-mold type cable joint shall be expanded gradually by emit of gas left in XLPE insulation. For example, sometimes the corona problem outbreak on a new power distribution line, resulted from the gap between the sleeve and semi-conductive layer of cable joint. If above mentioned problem especially happened on the way of operating. We have to shut down the line and try to discharge the methane gas in cable joint. In this point, we would like to explain the mechanism of methane gas & cable joint and our test result briefly. At last, we are pleased to introduce the solution for preventing reoccurrence of this problem.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.976-978
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• 2003

Quench characteristics of HTS tapes, which are applied over-current were investigated. When the applied current exceeds the critical current of HTS tapes, the superconductor of HTS tape comes to be changed into normal conductor so that the current begins to flow through the metal sheath, which is made of good electrical conductor. In this study, the current, corresponds to 10 times $I_c$ was fed to HTS tapes. Using the V-I curves and resistance with temperature variation of HTS tapes, the distribution of the applied current between superconductor and metal sheath was analyzed. As the results, we could acquire the duration and magnitude of current to reach to thermal quench.

• Transactions on Electrical and Electronic Materials
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• v.9 no.2
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• pp.84-88
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• 2008

In this paper, we analyze the errors associated with electric field interference for fiber-optic voltage sensors working in a three-phase electric system. For many practical conductor arrangements, the electric filed interference may cause errors unacceptable for the accuracy requirements of the sensors. We devised a real time compensation method for the interference by introducing geometric and weight factors. We realized the method using simple electronic circuits and obtained the real time compensated outputs with errors of 1 %.

• JOURNAL OF ELECTRICAL WORLD
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• no.5 s.89
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• pp.8-10
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• 1984

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.5-5
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• 2004

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.16-20
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• 2010

For large scale power applications of HTS conductor, it is getting more important to have a stacked HTS coated conductor with low loss and large current capacity. But it was not easy to measure some electric properties. Stabilizer free YBCO CC for striated/ stacked conductors is easily burned out during the measurement of the critical current density because it has no stabilizer and it is difficult to set-up the current lead and voltage taps because it has many pieces of YBCO CC in a conductor. Instead of direct measuring the critical current of a stacked HTS coated conductor, indirect estimation from measuring a magnetization loss of HTS coated conductor could be useful for practical estimation of the critical current. The magnetization loss of a superconductor is supposed to be affected by a full penetrating magnetic field, and it tends to show an inflection point at the full penetrating magnetic field when we generate the graph of magnetization loss vs. external magnetic field. The full penetrating magnetic field depends on the shape of the conductor and its critical current density, so we can estimate the effective critical current density from measuring the magnetization loss. In this paper, to prove the effectiveness of this indirect estimation of the critical current, we prepared several different kinds of YBCO CC(coated conductor) including a stacked conductor short samples and measured the magnetization losses and the critical currents of each sample by using linked pick up coils and direct voltage measurement with transport current respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.35-42
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• 2010

We use conformal mapping method to derive the analytical expressions for calculating electrostatic fields and electric potentials surrounding the conductor-backed coupled coplanar waveguide(CBCCPW) structure. Using the derived expressions, the electrostatic fields and potentials are computed at various points of the CBCCPW's geometry and the field and potential distributions are analyzed. The proposed method provides a faster and simpler calculation of the field distributions than the full-wave analysis method because no iterations are required. This method can be widely applied to the analysis of microwave integrated circuits using coupled line, such as coupler, filter, and microstrip antenna.

• Journal of Information Processing Systems
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• v.14 no.5
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• pp.1136-1149
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• 2018

With the increasing of urban electricity demand, making the most use of the power cable carrying capacity has become an important task in power grid system. Contrary to the rated ampacity obtained under extremely conservative conditions, this paper presents the various steady value of cable ampacity by using the changing surrounding parameters under operation, which is based on cable ampacity calculation equation under the IEC-60287 standard. To some degree, the cable ampacity analysis of actual surroundings improves the transmission capacity of cables. This paper reveals the factors that influence cable ampacity such as insulating layer thickness, allowable long-term conductor temperature, the ambient temperature, soil thermal resistance coefficient, and so on, then gives the class of the influence of these parameters on the ampacity, which plays a great role in accurately calculating the real-time ampacity and improving the utilization rate of cable in the complex external environment condition. Furthermore, the transient thermal rating of the cable is analyzed in this paper, and temperature variation of the conductor under different overload conditions is discussed, which provides effective information for the operation and control of the system.