• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1745-1750
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• 2017

Starting from the distribution transformer, the insulation oil for the oil immersed power transformer is being used to convert the vegetable oil from the existing mineral oil. Vegetable oil is better in temperature characteristics and insulation performance, is not toxic, and has better biodegradable characteristic than that of mineral oil. In order to investigate the corona inception voltage and dieclectic charateristics of the two insulating oils, three oil immersed transformers using mineral oil and vegetable oil were made and thermal cyclic aged. In this paper, the changes in the corona discharge inception voltage, chemical and electrical properties of the two sampled insulating oils from the transformers had been studied.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2002-2004
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• 2000

The discharge processes in electro-negative gases with non-uniform field gape are composed of the formation of pulsed streamer corona, the transition of the streamers into leader step, the temporal development of the leader channel, and the stepped propagation of leader through the gap. In this paper, the first corona inception characteristics in $SF_6$ gas and $SF_{6}-N_{2}$ mixtures, related to the propagation of loader and the space charge effect, were experimentally investigated with positive and negative transient impulse voltages.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.496-506
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• 2001

The effect of corona discharge on soot emission was experimentally investigated. Size and number concentrations of soot aggregates were measured and compared for various voltages. Regardless of the polarity of the applied voltage, the flame length decreased and the tip of flame spreaded with increasing voltage. For the experimental conditions selected, the flame was blown off toward the ground electrode by corona ionic wind. When the negative applied voltage was greater than 3kV(for electrode spacing = 3.5cm), soot particles in inception or growth region were affected by the corona discharge, resulting in the reduction of number concentration. The results show that the ionic wind favored soot oxidation and increased flame temperature. Number concentration and primary particle size greatly increased, when the corona electrodes were located the region of soot nucleation or growth(close to burner mouth).

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1702-1704
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• 1998

In order to establish the usefulness of ultrasonic techniques for detecting corona discharges in high-voltage power apparatus, it is first necessary to determine the relationship between electrical and ultrasonic signals of corona discharges in air. In this paper, various characteristics of ultrasonic signal detection for point-to-plane corona discharges using a 200[kHz] ultrasonic sensor are examined. In regard to the attenuation and directivity of ultrasonic signals, the signals were inversely proportional to the distance between corona sources and ultrasonic receiving sensors, and half attenuation angles were approximately 7.0 degree. Ultrasonic signals of positive polarities were first obserbed at corona inception voltages. and the signals were increased with increasing the applied voltages.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.258-262
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• 1988

Investigations were made on the effects of wire-shaped conducting particles in compressed gas chamber on breakdown voltage. The objective was to recognize the relationship between the length of wire-shaped conducting particles and a.c breakdown voltage. Also the influence of conducting particles on corona inception voltage and extinction voltage were investigated. The values of breakdown voltage and corona inception, extinction voltages were calculated by wire shaped-conducting particles lengths.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.25-29
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• 2004

Corona on polymer materials causes deterioration by the combined action of the discharge striking the surface and the action of certain chemical compounds that are formed by the discharges. In the design and manufacture of polymer insulators must be sufficiently large to avoid corona discharges, otherwise a shielding or corona ring (grading ring) needs to be installed on the insulator. To conduct this purpose, many researchers have investigated end-fitting of polymer insulator by voltage distribution simulation and electrical test. Grading rings are used to improve the performance of the insulator in multiple ways. They can reduce corona and associated audible noise and radio influence and television interference. The factors determining the uses of a grading ring are line voltage, geometry and dimensions of end fittings, geometry and dimensions of line hardware, and environmental conditions. In this paper, electrical property of polymer insulator with end-fitting design have been investigated by electrical field analysis, various end-fitting design, tracking wheel test, corona inception voltage and extinction voltage. Electrical field analysis is conducted by FEM program and various end-fitting is designed through this result. Designed end-fittings are manufactured and their performance is conducted by electrical performance test.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.27-34
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• 2002

In this paper, characteristics of the ac and dc flashover voltage in the horizontal air gap of a needle-needle electrode system were investigated when the combustion flame was present near the high-voltage electrode. In order to examine the flashover phenomena and the corona inception voltages caused by flame we measured the voltage and current waveforms when the corona and the flashover was occurred. We also observed, as increasing the applied voltages, the deflection or fluctuation phenomena in the shape of flames caused by the corona wind and the coulomb's force. As the results of an experimental investigation, we found that the reduction of flashover voltages, in comparison with the no-flame case, are 62.7[%] for k=1.0, 34.2[%] for h=5[cm], 27.3[%] for h=7[cm] and 21.4[%] for h=9[cm] when ac voltage is applied.

• Journal of ILASS-Korea
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• v.8 no.2
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• pp.24-30
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• 2003

An experimental study was performed to investigate the influence factors of drop formation in electrohydrodynamic atomization. The mode of electrohydrodynamic atomization depended on the various factors such as the flow rate of the liquid, the inner diameter of the nozzle, the distance between the nozzle tip and the ground electrode, the shape of the ground electrode. and the applied high voltage. This work was performed to investigate the experimental analysis for the flow pattern visualization of droplets, and the relationship between voltage application and the behavior of liquid atomization. Uniform drops of different sizes can be obtained at the inception of the spindle mode by charging the flow rate and the electric field. The drop size also decreased when the flow rate was raised for the spindle mode. The whipping motion occurred beyond 7kV and before the corona started to take effect.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1797-1799
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• 2003

In this paper, we measured partial discharge inception voltage(PDIV) and frequency spectra of UHF signal under following three cases, (1) a corona discharge due to a non uniform electric field for needle-plate electrode (2) a surface discharge caused by particles attached to a spacer in GIS, (3) free movements of particle in GIS. As a result of the experiment, it was revealed that the PDIV of Case (3) is higher than PDIVs of Case (1) and Case (2). It was also seem that UHF signal frequency spectra of one case are different from those of the other cases.