• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.2
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• pp.78-85
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• 2012

Low-Voltage power lines should equip surge protection devices which protect electronic equipments and human lives against lightning and abnormal voltages. Data transmission capacity of the power line is determined by frequency characteristics of the surge protective devices. To analyze the effects of surge protective devices on the data transmission performance, various combinations of installation methods are tested which include ZnO varistor elements that is compatible with class I, class II and class III. The result claims that ZnO varistor for class III is found to be one of the main factors that deteriorates the transmission performance. To overcome this problem a serial connection methed between Gap type SPD and ZnO varistor is proposed. With the proposed scheme, laboratory experimental results show that the data transmission performance can be improved up to 91.9[%] with proper SPD combination.

• Proceedings of the KIEE Conference
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• summer
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• pp.610-612
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• 2004

Because the overhead transmission lines are exposed to the outdoor weather, the faults of the transmission lines are due to natural conditions, and among these faults, the outage rate by lightning is about $50\%$. Therefore, the insulation design is important to decrease the damage of the facility and to increase the reliability of electric power system. This paper describes the protective method of substation equipments using the Underbuilt Ground Wire and the Guy Wire. This would not only reduce backflashover possibility but also minimize crest and duration of surges entering the substation. EMTP is used to analyze the efficiency of the proposed methods.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.347-348
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• 2008

This paper presents the use of Line Surge Arresters on 154kV double circuit lines. The ouatge rate which is highly related to the tower footing resistance is showed during the last a few year. The general methods that have been adopted at lines also are introduced. Lightning performance of lines without and with line surge arrester is studied and compared. The characteristics between air-gap type and gapless type LSA also compared. Line surge arrester installation strategy is presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.7
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• pp.92-98
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• 2012

It is made compulsory to install SPD for the purpose of protecting electric and electronic devices when an abnormal voltage such as lightning occurs to power line using power frequency of 60Hz. Recently, the high speed communication technology utilizing power line is receiving attention again as a communication technology for smart grid. The SPD influences the performances of power line communication when using SPD and power line communication system together. In order to improve the performance of power line communication, a proposed scheme for series connection of gas discharge tube to ZnO varistor was presented. This paper measured the impacts of series connection of GDT to SPD using ZnO varistor on the limit voltage of Class III SPD. This paper also presented the DC operating voltage of GDT which satisfies the limit voltage of power line communication system and SPD simultaneously.

• Journal of Korea Multimedia Society
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• v.17 no.5
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• pp.547-555
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• 2014

This paper presents a method for hand segmentation using depth information, and adaptive threshold by means of histogram analysis and color clustering in HSV color model. We consider hand area as a nearer object to the camera than background on depth information. And the threshold of hand color is adaptively determined by clustering using the matching of color values on the input image with one of the regions of hue histogram. Experimental results demonstrate 95% accuracy rate. Thus, we confirmed that the proposed method is effective for hand segmentation in variations of hand color, scale, rotation, pose, different lightning conditions and any colored background.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2377-2379
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• 1999

In order to analyze failure rates of underground transmission power cable systems in Korea, the survey has been performed for the failure cases of cables, joints, and terminations in CV, OF and POF cable systems which occurred from 1983 to 1998. During 16 years, the failure cases due to trips of the systems were 47 among the total 108 cases, These 47 cases could be divided into internal reasons(manufacture/installation, corrosion and degradation) of 16 cases and external reasons (external mechanical damages, lightning, fire. etc.) of 31 cases. For the 154 kV cable systems during 12 years from 1987 to 1998, total failure rate was 0.0057 [case/100C-km/year] and internal reason failure rate was 0.0020 [case/100C-km/Year], which is similar to those of foreign countries. Also, the many cases of internal reason failures occurred in the early stage after the operations due to incorrect installations. This implies that the installation process is very important and some diagnostic tests such as PD measurement are needed besides after laying test.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.589-595
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• 2012

When surges and electromagnetic pulses from lightning or power conversion devices are considered, it is desirable to evaluate grounding system performance as grounding impedance. In the case of large-sized grounding electrodes or long counterpoises, the grounding impedance is increased with increasing the frequency of injected current. The grounding impedance is increased by the inductance of grounding electrodes. This paper presents the measured results of frequency-dependent grounding impedance and impedance phase as a function of the length of counterpoises. In order to analyze the frequency-dependent grounding impedance of the counterpoises, the frequency-dependent current dissipation rates were measured and simulated by the distributed parameter circuit model reflecting the frequency-dependent relative resistivity and permittivity of soil. As a result, the ground current dissipation rate is proportional to the soil resistivity near the counterpoises in a low frequency. On the other hand, the ground current dissipation near the injection point is increased as the frequency of injected current increases. Since the high frequency ground current cannot reach the far end of long counterpoise, the grounding impedance of long counterpoise approaches that of the short one in the high frequency. The results obtained from this work could be applied in design of grounding systems.