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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Transactions of the Korean Institute of Electrical Engineers P
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Journal DOI :
The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 57, Issue 4 - Dec 2008
Volume 57, Issue 3 - Sep 2008
Volume 57, Issue 2 - Jun 2008
Volume 57, Issue 1 - Mar 2008
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Measurement Range Extension of AC High Voltage using two 200 kV Capacitive Dividers
Jung, Jae-Kap ; Lee, Sang-Hwa ; Kang, Jeon-Hong ; Kim, Myung-Soo ; Kim, Yoon-Hyoung ; Han, Sang-Gil ; Jeong, Jin-Hye ; Han, Sang-Ok ; Joung, Jong-Man ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 1~5
The output voltage value of AC high voltage source has been usually obtained by multiplying low voltage value measured at both terminals of low voltage resistor by the dividing ratio of the high voltage capacitive divider. From the dividing ratio determined of each 200 kV capacitive divider, we have developed step-up method for measuring the output voltage up to 400 kV using two same type of 200 kV capacitive dividers connected in series. The theoretical dividing ratio of 400 kV capacitive dividers connected in series coincides with that of manufacturer's certification within measurement uncertainty. Thus, this developed step-up method makes it possible to extend the range of output voltage from 200 kV to 400 kV. Furthermore, The dividing ratio of divider under test obtained using this step-up method is consistent with that obtained using one 200 kV high voltage divider within corresponding uncertainties.
Establishment of National Standard System for 20.000 A Current Transformer
Jung, Jae-Kap ; Lee, Sang-Hwa ; Kang, Jean-Hong ; Kim, Myung-Soo ; Kim, Yoon-Hyoung ; Han, Sang-Gil ; Han, Sang-Ok ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 6~13
National standard system for calibrating current transformer(CT) up to primary current of 20,000A have been established. The system consists of 20,000 A AC high current source, CT comparator, standard CT, CT under test and CT burden. An AC high current is applied tn the primary windings of both the standard CT and the CT under test, and then the CT comparator measures the ratio error and the phase displacement by comparing the secondary currents of the two transformers. As a validity check for 20,000 A CT calibration system, the comparison with the two national standard institutes(NMIs) has been performed using same CTs. The comparison results of the CTs are consistent with those measured at two NMIs within 0.004 % for ratio error and 0.1 min for phase displacement in the primary current ranges of Ip = 10 - 20,000 A with a secondary current of Is = 5 A.
An Adaptive Contrast Enhancement Method using Dynamic Range Segmentation for Brightness Preservation
Park, Gyu-Hee ; Cho, Hwa-Hyun ; Lee, Seung-Jun ; Yun, Jong-Ho ; Chon, Myung-Ryul ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 14~21
In this paper, we propose an adaptive contrast enhancement method using dynamic range segmentation. Histogram Equalization (HE) method is widely used for contrast enhancement. However, histogram equalization method is not suitable for commercial display because it may cause undesirable artifacts due to the significant change in brightness. The proposed algorithm segments the dynamic range of the histogram and redistributes the pixel intensities by the segment area ratio. The proposed method may cause over compressed effect when intensity distribution of an original image is concentrated in specific narrow region. In order to overcome this problem, we introduce an adaptive scale factor. The experimental results show that the proposed algorithm suppresses the significant change in brightness and provides wide histogram distribution compared with histogram equalization.
An Adaptive Color Enhancement Algorithm using the Preferred Color Reconstruction
Yang, Kyoung-Ok ; Hwang, Bo-Hyun ; Lee, Seung-Jun ; Yun, Jong-Ho ; Chon, Myung-Ryul ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 22~29
In this paper, we propose an adaptive color enhancement algorithm. It is used for the flat panel displays (FPDs) such as LCD, PDP, and so on. The proposed algorithm consists of an adaptive linear approximation CDF(Cumulative Density Function) algorithm and an adaptive saturation enhancement algorithm. The one is for contrast enhancement which prevents an image from the distortion by luminance transient of an input image. The other is the algorithm which improves the saturation without the contour artifact and over-saturation, whose problems are generated during the enhancing saturation. In addition, it allows to achieve the high quality image using the saturation enhancement method for a preferred color of original image. Visual test and standard deviation of their histograms have been applied to evaluate the resultant output images of the proposed algorithm.
The Study of Distributed Disturbance Recording System
Park, Jong-Chan ; Lee, Se-In ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 30~35
In this paper, the application of power Quality monitoring based on Sampled Value(SV) which is introduced in the IEC61850 International Standard for substation communication are discussed. Firstly, while Merging Unit(MU) is designed as a process level device transmitting sensor data, the practical problems such as time delay compensation and optical fiber communication are encountered. Secondly, the Sampled Value message which is proper to a power quality monitoring system is presented. Because the power quality monitoring system requests less time-critical service compared to protection and control applications, the Sampled Value service message structure is introduced to improve efficiency. Lastly, the power quality monitoring server having various power quality analysis functions is suggested to verify the performance of Merging Unit With the diverse experiments, it is proved that the process bus distributed solution is flexible and economic for the power quality monitoring.
A Study on the Characteristics for Power Capacitor under the Voltage Unbalance Operation
Kim, Il-Jung ; Kim, Jong-Gyeum ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 36~40
Most of the low-voltage feeder are designed with approximately balanced and connected at the three phase four wire systems. However, Most of the power distribution systems' load which is composed of single or three phase are unbalanced by generating load unbalance. Unbalanced current will draw a highly unbalanced voltage. The power factor of an induction motor at rated operation is between 25 and 90%, depending on the size and speed of the motor. However, many induction motors operate below the nominal rating, resulting in poor power factor. This condition needs power factor improvement. Addition of power capacitor at the motor terminal may draw to stress due to voltage unbalance. This paper presents operation characteristics on steady states of a three-phase induction motor under unbalanced voltages with power capacitor. The existence of voltage unbalance have an effect on stress of power capacitor.
Determination of Phase Converter Reactances for Monocyclic-start Induction Motor
Kim, Do-Jin ; Jwa, Chong-Keun ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 41~45
This paper describes a simple and straightforward method to determine phase converter reactances for the monocyclic start induction motor which have two different phase converters. In order to determine two reactances, two kinds of simultaneous equations with two unknown reactances at a specified speed are set up by the condition of balance operation. From these equation, these unknown reactances can be solved directly using the application software without any algebraic calculation. The applicability of this method is investigated by comparing with the known method by using the computed results at the starting and rated speed, and the results show good agreement each other. Using these results, the performance characteristics of this motor are computed and compared with three phase balance operation of induction motor.
A Study on the Design of the Bay Controller for Generator Protection and Control
Jang, Nak-Won ; Woo, Chun-Hee ; Lee, Sung-Hwan ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 46~55
In this paper, we designed the bay control unit that is based on the microprocessors and integrates with the new technology of electrical, electronic, and mechanical fields. Nowadays the customers have required much more integrated multi-protection relay, monitoring, control devices and power management for better and easier maintenance, performance, electrical system analysis and communication according to new trend of switchboard This bay controller supplies those requirements of customers with easy handling and operation. This bay controller provides a graphic display with rear-lit liquid crystal LCD and push buttons as kinds of HMI(Human Machine Interface). This bay controller provides the parameter setting program, control setting program, various editors and fault recording and analysis program on Windows/95/98/NT/2000/XP for HMI. In addition, this bay controller can be set manually and this manual setting function helps user to interface easily.
Signal Characteristics of Ultra-high Frequency Radiation from Partial Discharge in Insulation Oil
Ju, Hyoung-Jun ; Goo, Sun-Geun ; Park, Ki-Jun ; Han, Ki-Seun ; Yoon, Jin-Yul ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 56~59
We have designed 4 types(void in insulation paper, protrusion electrode, floating electrode, surface discharge) of partial discharge(PD) defect to simulate typical faults found in oil filled power transformers. Ultra-high frequency(UHF) radiation due to PD was measured using a UHF measuring system and a conventional PD measuring system, simultaneously. Electromagnetic radiation spectra of these defects show UHF radiation up to about 1.5-2 GHz range. The phase resolved partial discharge(PRPD) patterns of UHF radiation from the PD defects were also measured and the pattern reveals distinct feature for each defect types. The UHF measuring could be used to detect PDs in oil filled transformers and analysis of the PRPD pattern should provide useful information on origin of PD signal.
On-line Insulation Diagnostic by PD Monitoring
Choi, Yang-Sung ; Oh, Yong ; Kim, Hyang-Kon ; Choi, Chung-Seog ; Lee, Kyung-Sup ;
The Transactions of the Korean Institute of Electrical Engineers P, volume 57, issue 1, 2008, Pages 60~64
The paper considers the relation between on-line monitoring and diagnostics on the one hand and high-voltage (HV) withstand and partial discharge (PD) on-site testing on the other. HV testing supplies the basic data (fingerprints) for diagnostics. In case of warnings by on-line diagnostic systems, off-line withstand and PD testing delivers the best possible information about defects and enables the classification of the risk. Because alternating voltage (AC) is the most important test voltage, the AC generation on site is considered. Frequency tuned resonant (ACRF) test systems are best adapted to on-site conditions. They can be simply combined with PD measuring equipment. The available ACRF test systems and their application to electric power equipment -from cable systems to power transformers - is described.