• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1759-1764
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• 2015

Glow corona is a kind of streamer-free corona that can suppress upward leaders in transmission lines. Thus, it has good application potential in lightning protection. This paper investigates its corona characteristics. The suppression characteristic of glow corona on streamer is studied in air gap under negative DC voltage by wrapping thin wires on the electrode. The effect of thin wire winding patterns on the gap breakdown voltage is analyzed. Results are considered to be attributed to the inception condition of glow corona. Thus an inception test of glow corona is also conducted, and the inception voltage is obtained. Results show that the inception voltage decreases with short winding pitch. Thus an investigation on the inception of glow corona influenced by thin wire is conducted, and an influential factor is proposed to evaluate the influence. The inception regular of thin wire glow corona presented in this paper has certain reference value for the application of glow corona in transmission lines.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.226-244
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• 1998

The relationship between the transport of eggs and larvae of Anchovy (Engraulis japonica) and the oceanic condition in the southern sea of Korea was examined on August and November 1996. In summer (August), when the Tsushima Warm Current is strong near to the coast, the warm waters such as warm streamers from the Tsushima Warm Current intrude into the coastal area, and cyclonic circulations are formed. The warm water intrusions also generate wakes around Komun Island, Sori Island and Koje Island. In the coastal area where the warm water intrusions occur, the nutrients, dissolved oxygen, suspended solid and chlorophyll are concentrated in probably relation to the upwelling concerned with this warm streamer and/or the wakes. Anchovy eggs and larvae are transported to the coastal area by the cyclonic circulations. The hatching and growth of anchovy larvae are increased because of high primary production in the cyclonic circulations. However, as the amount of Copepods which are a main food for anchovy larvae decrease in the coastal area, anchovy larvae seem to move to the Isushima Warm Water area for seeking a prey. In autumn (November), the Tsushima Warm Current is far away from the coast. In this season the warm water intrusions almost disappear, and the small scaled frontal eddies are formed between the coastal water and the Tsushima Warm Water. As the surface water moves towards offshore, few anchovy eggs and larvae were sampled in the survey area. Chemical and biological substances are concentrated in the leftdown sides of the small scaled frontal eddies because of eddy formation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.989-993
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• 2009

Triple junction which consists of three media(electrode, insulator, and gas) should be considered in designing of high voltage equipments due to the electric field enhancement. In this paper, positive lightning impulse breakdown voltage is predicted based on the streamer theory for simplified insulator models and 72.5kV spacer with varying the triple junction geometry and gas pressure, and the results are compared to the experimental results. The electric field coefficient concept is also applied in order to evaluate the partial discharge inception voltage and the surface flashover voltage from the streamer inception voltage. The application of this method using the constant electric field coefficient of 1.3 and 0.66 is possible for evaluating the triple-junction insulation of the simplified insulator and the 72.5kV spacer respectively. The error rate is under 10%.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.254-255
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• 2007

This paper describes underwater discharge phenomena which are less studied than gas, solid and dielectric liquid. Since discharge phenomena were affected by various factors, we investigated the effect of water resistivity in point-plane gap by impulse voltage. In discharge photograph, it is hard to discover the streamer development in positive polarity at high reisistivity. On the other hand, the streamer originated at the tip of rod and developed toward the plane with increasing voltage. It is found that the breakdown voltage of both polarities in lower resistivity are lower than that of high resistivity. High current flowing in lower resistivity before the breakdown induce more streamer and enhance the probability of breakdown.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.129-139
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• 2022

Analog-based streamers for ultra-high-resolution seismic surveys are capable of additional noise ingress in water, but the specifications cannot be expanded through interconnections. Foreign-produced digital streamers have been introduced and used primarily at domestic research institutes; however, the cost is high and smooth maintenance is challenging. This study investigates the localization of ultra-high-resolution digital streamers capable of high-resolution imaging of a geological structure. A digital streamer capable of 24-bit, 10 kHz digital sampling of up to 64 channel data was developed through research and development. Various quantitative specifications of the system were designed and developed close to the benchmark model, Geometrics' GeoEel streamer, and the number of modules that make up the system was drastically reduced, reducing development costs and making it easier to use. The field applicability of the developed streamer system was evaluated in an in situ experiment conducted in the waters around the Port of Yeong-il Bay in Pohang in April 2022.

• 전기의세계
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• v.27 no.2
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• pp.64-68
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• 1978

By applying the streamer breamer breakdown criterion and the surface roughness factor, the effet of field distortion due to conductor surface roughness on breakdown is investigated theoretically in a uniform-field of compressed SF$_{6}$. It has been shown that the streamer constant has a significant influence on the threshold of breakdown and different shapes of protrusions do not result in different thresholds of breakdowns. Moreover, uniform-field tests can give results which apply to e-ratio coaxial-electrode systems of practical dimensions, and may offer some advantages compared with coaxial-electrode tests.s.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.160-168
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• 2010

This paper tried to find out NO generation and removal mechanisms in the space of the atmospheric pulsed barrier discharge using laser induced fluorescence method, which is a very effective approach to the measurement of spatio-temporal density of specific molecules. The propagation velocity of the primary streamer reaches about $2.7{\times}10^6$[m/s] and the secondary streamer is produced in the vicinity of positive electrode after the primary streamer finished. In this work, pulse Nd:Yag and Dye lasers are used for generating the specific wavelength of 226[nm], which is possible to excite NO molecules into $A^2{\Sigma}^+{\rightarrow}X^2{\prod}$(0,0) and fluorescence signals as the transition of $A^2{\Sigma}^+{\leftarrow}X^2$(0,2) is measured. For the effective removal of NO molecules in the plasma discharge process, the lower oxygen contents are needed and the influence of secondary streamer for the reduction mechanism of NO molecules is important

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1663-1672
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• 2018

In recent times, gas insulated medium voltage (MV) circuit breakers (CB) form a vital component in power system network, considering its advantages such as reduced size and safety margins. Gas insulation characteristics of circuit breakers are generally measured by lightning impulse (LI) test according to IEC standard 60060-1 as a factory routine test. Considering the environmental issues of $SF_6$ gas, many research works are being carried out towards the mixture of $SF_6$ gases for high voltage insulation applications. However, few reports are only available regarding the LI withstand and streamer propagation characteristics (at both positive and negative polarity of waveform) of $SF_6/N_2$ gas mixture insulated medium voltage circuit breakers. In this paper, positive and negative polarity LI tests are carried out on 22 kV medium voltage circuit breaker filled with $SF_6/N_2$ gas mixture at different gas pressures (1-5 bar) and at different gas mixture ratios. Important LI parameters such as breakdown voltage, streamer velocity, time to breakdown and acceleration voltage are evaluated with IEC standard LI ($1.2/50{\mu}s$) waveform. Weibull distribution analysis of LI breakdown voltage data is carried out and 50% probability breakdown voltage, scale parameter and shape parameter are evaluated. Results illustrate that the $25%SF_6+75%N_2$ gas filled insulation considerably enhances the LI withstand and breakdown strength of MV circuit breakers. LI breakdown voltage of circuit breaker under negative polarity shows higher value when compared with positive polarity. Results show that maintaining the gas pressure at 0.3 MPa (3 bar) with 10% $SF_6$ gas mixed with 90% $N_2$ will give optimum lighting impulse withstand performance of 22 kV MV circuit breaker.

• Geophysics and Geophysical Exploration
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• v.26 no.2
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• pp.52-61
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• 2023

The use of ultra-high-resolution (UHR) seismic surveys to preceisly characterize coastal and shallow structures have increased recently. UHR surveys derive a spatial resolution of 3.125 m using a high-frequency source (80 Hz to 1 kHz). A digital streamer system is an essential module for acquiring high-quality UHR seismic data. Localization studies have focused on reducing purchase costs and decreasing maintenance periods. Basic performance verification and application tests of the developed streamer have been successfully carried out; however, a comparative analysis with the existing benchmark model was not conducted. In this study, we characterized data obtained by using a developed streamer and a benchmark model simultaneously. Tamhae 2 and auxiliary equipment of the Korea Institute of Geoscience and Mineral Resources were used to acquire 2D seismic data, which were analyzed from different perspectives. The data obtained using the developed streamer differed in sensitivity from that obtained using benchmark model by frequency band.However, both type of data had a very high level of similarity in the range corresponding to the central frequency band of the seismic source. However, in the low frequency band below 60 Hz, data obtained using the developed streamer showed a lower signal-to-noise ratio than that obtained using the benchmark model.This lower ratio can hinder the quality in data acquisition using low-frequency sound sources such as cluster air guns. Three causes for this difference were, and streamers developed in future will attempt to reflect on these improvements.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1571-1576
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• 2016

A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla in 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity. Tesla coil can generate a long streamer with several million volts of electricity as a high voltage device. It is basically consists of a voltage transformer, high voltage capacitor, spark gap, primary coil, secondary coil and toroid. It is difficult to appear in the output size of the streamer is controlled by the spark gap. The general decision method of the length of streamer is to display the electric output in accordance with the design specifications in initial development plan. Design specifications and the electric output is determined by the application of facilities. In this paper the spark gap is replaced with periodic switching semiconductor device to control output voltage easily in order to apply overvoltage protective circuit due to a secondary coil and a performance test. In these days, their main use is for entertainment and educational displays of the museum, although small coils are still used as leak detectors for high vacuum systems.