• ETRI Journal
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• v.44 no.2
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• pp.339-345
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• 2022

This article presents an investigation of the effects on a grounding system of wireless power transfer (WPT) when transmitting over relatively far distances, that is, up to 1.25 m. Conventional two-coil WPT systems are sufficiently commercialized in strong coupling range, but it is important to accomplish the long-range WPT in weak coupling range for further various applications. This system depends on the coupling effect between the two coils that the grounds of the transmitting and receiving coils should be completely separated. However, when evaluating the performance of two-coil systems with the instrument consisting of two ports and one common ground, undesirable problems occur in weak coupling ranges, for example, obtaining disagreeable transmission efficiency and degrading system stability/reliability. We investigate the problems of the leakage power from common ground systems and provide a practical solution to obtain a reliable WPT system by using an isolation transformer. The usefulness of this approach is that it is possible to achieve the stability of the system with relatively far transmitting distances and to determine the exact transmission efficiency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.55-62
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• 2005

There are many risk factors of electrical shock caused by a minimum of protective devices, loose working environments, deterioration of installations at temporary power installations of construction sites. An insulation cover for instrument transformer(MOF) used in 22.9[kV] class power receiving system hasn't shown good performance in terms of electrical safety because of short clearance between insulation cover and each input and output wire junction part. The insulation cover is easily moved by outside environment as wind or rain because of different size between insulation cover and busing, also can be leaded to breakdown by tracking. Therefore, we have proposed the insulation cover which effectively can prevent from electrical disaster in this paper, and a utility model patent had been registered already. To decrease the electric field concentrated on specific part, we had roundly designed the shape of insulation cover and the clearance between cover and live part was adjusted to be longer than the existing thing. The proposed insulation cover was evaluated by using the electric field solution program.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.570-573
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• 2022

This paper presents the identification of void diameters for a cast-resin transformer using an artificial neural network (ANN) model. A PD signal was measured by the Rogowski coil sensor which has the planar and thin structures fabricated on a printed circuit board (PCB), and the PD electrode system was fabricated to simulate a PD defect by a void. In addition, void samples with different diameters were fabricated by injecting air in a cylindrical aluminum frame using a syringe during the epoxy curing process. To identify the diameter of void defects, PD characteristics such as the discharge magnitude, pulse count, and phase angle were extracted and back propagation algorithm (BPA) was designed using virtual instrument (VI) based on the Labview program. From the experimental results, the BPA algorithm proposed in this paper has over 90% accurate rate to identify the diameter of void defects and is expected to use reference data of maintenance and replacement of insulation for cast-resin transformers in the on-site PD measurement.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2021_2022
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• 2009

Partial discharges(PD) is a important factor to evaluate the insulation state in high voltage electric machinery. However, measuring PD under the circumstances of power plant is occasionally impossible due to the relatively high magnitude of noise which is emanated from the operating machinery. In some case, the instrument measuring PD can not even perform a calibration that initializes tools and enhance the accuracy. This paper presents that we devised a noise reduction method and demonstrated the usefulness in acquiring reliable PD signals. We attached a series of filter and transformer at the input of power source of the instruments which refrains high noise signals from incoming to the instruments. We experimented the efficiency of noise reduction applying the device into the Dangjin Power Plant and Factory. As a result of testing with the filter and transformer, we can easily calibrate the PD signal compared to the case without the device. Additionally, we can detect the small PD signal which was unperceived with a normal device.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.266-271
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• 2014

The Electromagnetic Interference(EMI) generating from corona discharge of transformer area can interference the digital Instrument and Control(I&C) systems located nearby transformers. When the potential gradient of the electric field around the conductor is high enough to form a conductive region but not high enough to cause electrical breakdown to nearby objects, the EMI of corona discharge emits with the conducted and radiated noise and it interferences the signals of the I&C systems. Since digital I&C systems have an efficiency and competitive price, the analog I&C systems have been upgraded and displaced with the digital I&C systems but which have less EMI Immunity. There was no assessment to I&C systems by EMI generating corona discharge nearby transformers. When the safety-related I&C systems are installed in plants, the verification of equipment EMI should be done not in site-specific test but in test facilities. There are the need to do the site-specific EMI evaluation of corona discharge nearby transformers. This paper assesses the margin between plant emission limits and the highest composite plant emission of corona. When the non safety-related I&C systems are placed in transformer area, it suggests the appropriate radiated susceptibility level to EMI of corona discharge.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.456-457
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• 2006

We have carried out the construction of the 154kV intelligent substation with KEPRI. The Intelligent substation is built in Gochang testing facility of KEPCO and consists of electronic instruments for GIS(gas insulated switchgear), digital control panel, remote monitoring and diagnosis system, and digital relay system. Rogowski coil type CT(RCT) and capacitive voltage divider(CVD) are introduced compared with the instrument transformer of conventional type. Digital control Panel(DCP) replaces the LCP(local control panel) which is drived for mechanical operation. For the monitoring of the condition of GIS and TR, various sensors are used. In this Paper, we mention the synopsis and report the progress state of project.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.33-35
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• 2005

We perform intelligent substation construction of 154kV class with KEPRI. The intelligent substation is build in Gochang 765kV testing facility and consists of electronic instruments, digital control panel, remote monitoring and diagnosis system and digital relay system. Rogowski coil type CT(RCT) and capacitive voltage divider(CVD) are applicable for instrument transformer of conventional type. Digital control panel(DCP) replaces local panel which is drived by mechanical operation. For monitoring condition of GIS and TR, various sensors are used. In this paper, we report the synopsis and the progress state of project.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.129-130
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• 2005

We perform intelligent substation construction of 154kV class with KEPRI. The intelligent substation is build in Gochang 765kV testing facility and consists of electronic instruments, digital control panel, remote monitoring and diagnosis system, and digital relay system. Rogowski coil type CT(RCT) and capacitive voltage divider(CVD) are applicable for instrument transformer of conventional type. Digital control panel(DCP) replaces local panel which is drived by mechanical operation. For monitoring rendition of GIS and TR, various sensors are used. In this paper, we report the synopsis and the progress state of project.

• Proceedings of the KIEE Conference
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• summer
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• pp.524-526
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• 2004

We perform intelligent substation construction of 154kV class with KEPRI. The intelligent substation is build in Gochang 765kV testing facility and consists of electronic instruments, digital control panel, remote monitoring and diagnosis system, and digital relay system. Rogowski coil type CT(RCT) and capacitive voltage divider(CVD) are applicable for instrument transformer of conventional type. Digital control panel(UP) replaces local panel which is drived by mechanical operation. For monitoring condition of GIS and TR, various sensors are used. In this paper, we report the synopsis and the progress state of project.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.459-460
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• 2006

Electron beam manufacturing system can be used to make patterns that are smaller than can a photolithography. In this system, High voltage generator is a fundamental element for stable beam. We used high voltage with transformer. However, this instrument has several problems (for examples, dimensions, buying parts, simplicity of control circuit). For solving these problems, a commercial product is considered. This is developed for SEM(Scanning Electron Microscope). In this paper, we designed a control circuit for a commercial product and analyzed performance.