• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.515-516
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• 2011

송 배전 및 정보통신 설비, 건축물 등 모든 분야의 설비 및 인명 보호를 위해서는 반드시 필요하고 중요한 것이 접지이며, 접지 설계 시 대상 부지의 정확한 대지고유저항을 측정, 분석하는 것은 가장 중요하다고 할 수 있다. 본 대지고유저항 분석시스템은 이렇듯 중요한 대지고유저항을 기존의 수작업 분석방법이 아닌 시스템 반복계산에 의한 최적 curve 분석방법을 도입, 측정값의 신뢰도 평가 등을 이용한 측정값 분석으로, 분석값의 정확성을 높이고 분석시간을 단축함으로서 보다 정확하고 신속한 접지설계를 가능하도록 한다.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.90-95
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• 2015

This paper describes IEC 61727 standard of Photovoltaic (PV) systems -Characteristics of the utility interface. IEC 61727 standard tests include utility compatibility and personnel safety and equipment protection of PV inverter performance functions. Especially utility compatibility part includes test items of 1) voltage, current and frequency, 2) normal voltage operating range, 3) flicker, 4) DC injection, 5) normal frequency operating range, 6) harmonics and 7) waveform distortion, 8) power factor of PV inverter. Also personnel safety and equipment protection part includes test items 1)loss of utility voltage, 2)over/under voltage and frequency, 3)Islanding protection, 4)response to utility recovery, 5)earthing, 6)short circuit protection, 7)Isolation and switching of PV inverter. In this paper, each item of IEC 61727 standard test is studied and analyzed and finally full tested by PV inverter performance function.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1111-1116
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• 2011

Power distribution systems onboard vessels are typically configured without any live line connected to hulls for earthing purpose, where the line to hull voltages are affected and deformed depending on the impedances consisting of insulation resistances and distributed capacitances between power lines and hull. An insulation fault at power lines causes the line to hull voltages to increase to a higher level which brings more possibilities to electric shock and deterioration of insulation material. This study focuses on how to configure a module which enables to continuously monitor the voltages between power line and hull based on the vector diagram by analyzing the neutral point of 3 phase voltages and the algorithm for plotting method on the PC monitors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.983-988
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• 2009

This paper analyzed the induced voltages on a telecommunication line due to high-speed a.c. electrified railway system. The induced voltages were measured by domestic regulation, 2 test lines with 2 km length were installed near railway in parallel to compare the influence for distance from disturbing line. The analysis was made on the induced voltages with the distance from railway, line length, and the different earthing point, and also on the waveform and spectrum distributions. The statistical induced voltages for the time for a day and dates was analyzed.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1864-1866
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• 1996

Grounding is the art of making an electrical connection to the earth. In order to protect man, electrical and/or electric equipments from the lightning strokes, all the energy of lightning strokes must be diverted via a safe path to earth. It is essential to the transient grounding resistance against lightning strokes. In this paper, measurements and analyses of grounding surge impedance have been investigated. For measurements of grounding surge impedance the pulse generator was designed and fabricated. The pulse generator has rise time of 22.4 ns and pulse duration of $8\;{\mu}s$. The transient grounding resistance has been measuring by injecting low power and step current between the earthing system under test and a remote reference earth and measuring the potential rise caused by this current. As a result, the transient grounding resistance against lightning surge in the short time domain is much higher than steady state grounding resistance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.487-495
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• 2021

The voltages mainly used in ships are 450 [V], 6.6 [kV], and 11 [kV], and an earthed system is applied to ensure the stability of the power distribution system. In general, low-voltage ships using 450 [V] apply an unearthed system, while high-voltage ships using 6.6 [kV] or 11 [kV] use a high-resistance earthed system. When an earth fault occurs in a ship's power distribution system, the voltage of the healthy phase increases to the line-to-line voltage or higher, which causes an excessive impact on the insulation of the cable. Thus, analyzing this behavior is very important. In this paper, we investigate the characteristics of the line-to-earth voltage variation according to earth faults and a recognition procedure of a faulty phase using the symmetrical coordinate method for a high-resistance earthed system and unearthed system. A mathematical model of the line-to-earth voltage was derived through the symmetric coordinate method, and the ship voltage for simulations was selected as 6.6 [kV] and 450 [V]. A MATLAB simulation proved that this method can determine the highest increase of the line-to-earth voltage, which leads by 120° on the faulty phase, and it accurately judges the faulty phase in both earthed systems.

• Korean Journal of Plant Resources
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• v.30 no.5
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• pp.556-564
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• 2017

Appropriate soil temperature and early planting of potato is very important for the successful potato-soybean cropping system in central region of South Korea. This experiment was carried out to determine the effect of mulching materials on the growth and yield of potato (Solanum tuberosum L.). Five different mulch treatments were had been applied on an upland soil as follows ; no mulch (NM), transparent film (TF), transparent film + additional transparent film (TF + ATF), black film (BF), and black film + additional transparent film (ATF). In the period of sowing time to removing additional films, mean soil temperature of the treatments was in the order of TF+ATF > TF > BR+ATF > BF as $20.3^{\circ}C$ > $18.5^{\circ}C$ > $16.1^{\circ}C$ > $15.4^{\circ}C$, respectively and that of NM was $13.8^{\circ}C$. The accumulated soil temperature was TF > NM > BF during the removing additional films to earthing at inter-tillage. On the changes in the soil temperature during a whole day, the temperature in the BF was lower than NM during around 18:00 PM to 12:00 NM, while NM was higher than BF in the time period of 10:00AM to 21:00PM. The sequence of potato sprout emergence was 15 > 18 > 20 > 22 days of TF+ATF, TF, BF+ATF, and BF, respectively and that of NM was 24 days. Comparing to the NM, potato sprout emergence was observed on the TF+ATF treated plot as early as 9 days. At 10 days before harvest, the significant difference in the tuber dry weight had been observed and the sequence tuber weight was in the order of TF > TF+ATF > BF+ATF > BF > NM. The potato yields of TF, TF+ATF, and BF+ATF were increased of 40.7, 37.3, and 22% as compared to NM ($2,805kg\;10a^{-1}$), but almost same yield in the BF. The differences of tuber dry weight and potato yields was co-related with the temperature rise of soil by the application of mulching materials on soil. Based on these results, application of mulching film had been very effective to increase the tuber size and the yield of potato by the temperature rise during seedling stage of potato. Transparent mulching was better than black mulching especially for the emergence of sprout of potato in relation to minimizing cooling injury.