• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1375-1384
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• 2014

Flashover of power transmission line insulators is a major threat to the reliable operation of power system. This paper deals with the flashover prediction of polymeric insulators used in power transmission line applications using the novel condition monitoring technique developed by PD signal time-frequency map and neural network technique. Laboratory experiments on polymeric insulators were carried out as per IEC 60507 under AC voltage, at different humidity and contamination levels using NaCl as a contaminant. Partial discharge signals were acquired using advanced ultra wide band detection system. Salient features from the Time-Frequency map and PRPD pattern at different pollution levels were extracted. The flashover prediction of polymeric insulators was automated using artificial neural network (ANN) with back propagation algorithm (BPA). From the results, it can be speculated that PD signal feature extraction along with back propagation classification is a well suited technique to predict flashover of polymeric insulators.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.603-609
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• 2015

Dry air is an excellent alternative to $SF_6$ gas and is used as an insulation gas in Eco-friendly Gas Insulated Switchgears (EGISs), which has gained popularity in industry. Solid insulators in EGIS play an important role in electrical insulation. On the other hand, surface discharge can occur easily when solid insulators are used. This paper explored the surface discharge characteristics on the structure of three-layered laminated solid insulators to elevate the flashover voltage. A laminated solid insulator was inserted after the quasi-uniform electric field was formed in the test chamber. Dry air was then injected to set the internal pressure to 1 ~ 6 atm, and the AC voltage was applied. When identical solid insulators were stacked, the surface discharge characteristics were similar to those of a single solid insulator. On the other hand, the flashover voltage rose when the middle part was thicker and had lower permittivity than the top and bottom parts in the laminated solid insulator. Based on experimental results, when stacking a solid insulator in three layers, the middle part of the solid insulator should be at least four times as thick as the top and bottom parts and have lower permittivity than the others. In addition, the flashover voltage increased with increasing gas pressure on the surface of the laminated solid insulator due to the gas effect. This study may allow insulation design engineers to have useful information when using dry air for the insulation gas where the surface discharge can occur.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.472-473
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• 2007

This study evaluated electrical characteristics of the manufactured arcing horn whose rated voltage and nominal discharge current were 18kV and 2.5kA, respectively. In this study, residual voltage and lightning impulse flashover voltage were examined. The arcing horn showed excellent electrical characteristics that residual voltage and lightning impulse flashover voltage were 55kV below and 121kV at 115mm, respectively. Therefore the manufactured arcing Horn is considered that it would show good performance for protecting electrical wires and line post insulators from lightning impulse, if it were applied to real fields.

• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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• pp.10-13
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• 2011

For the operation of high temperature superconducting (HTS) power equipments, it is necessary to develop insulating materials and high voltage (HV) insulation technology at cryogenic temperature of bushing. In this paper, the surface flashover characteristics of various insulating materials in $LN_2$ are studied. These results are studied at both AC and impulse voltage under a non-uniform field. The negative impulse breakdown voltage of GFRP is slightly higher than the positive impulse breakdown voltage. The use of glass fiber reinforced plastic (GFRP) and polytetrafluoroethylene (PTFE, Teflon) as insulation body for HTS bushing should be much desirable. Especially, GFRP is excellent material not only surface flashover characteristics but also mechanical characteristics at cryogenic temperature. The surface flashover is most serious problem for the shed design in $LN_2$ and operation of superconducting equipment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.41-46
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• 2015

This study was conducted to discover a substitute of $SF_6$ gas. $SF_6$ gas is widely used across the industries. Thanks to superior electrical properties, in particular, it has been commonly used in electrical industry. However, there have been a lot of studies on its serious effect on global warming. As a substitute of this synthetic gas, a mixture of dry air and $N_2/O_2$ was chosen in this study. In case of $N_2/O_2$, dielectric strength differs depending on the mixing ratio. This study examined dielectric breakdown and flashover after adjusting oxygen percentage in the dry air. This test was conducted in a quasi-uniform electric field depending on pressure, oxygen concentration and gas mixtures. The test results found that dielectric voltage and flashover voltage were the highest at a certain oxygen concentration. It is the results of this photoionization and electron attachment of oxygen.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.73-82
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• 2004

This paper investigates a lightning multi-phase flashover on extra high voltage transmission line, which has influence on power systems very much, by the use of ATP. Especially we validated an arcing horn model represented by the nonlinear inductance and resistance which is the most important on the simulation for a multi-phase flashover. We also study relationships between lightning parameters and flashover phases in 765(㎸) double circuit transmission system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.58-65
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• 2009

A forest fire in the area of power line installations may be caused by flashover disturbances in power systems. In this study, experiments were conducted so as to investigate the reduction in dielectric strength caused by combustion flame, and flashover characteristics in the simulated condition of vertical-type model power lines were examined by making shorter and longer the horizontal distance(s) between combustion flame and high-voltage conductors under the application of 60[Hz] a.c. and d.c. high-voltages. As the results of the experimental investigation it is demonstrated that flame can reduce flashover voltages of the model air-gap in shorter range of the horizontal distance(s). Relative air density is considered in order to analyze the reduction causes of the flashover voltages, and it can be seen that the relative air density has a great influence on the flashover characteristics under the presence of combustion flame.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.82-87
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• 2012

In this paper, flashover characteristics of air in the vertical arrangement of cylinder-shaped rod and plane gap in the case of combustion flame on the plane electrode were examined under the application of a.c. and d.c. high-voltages. In order to investigate the effect of propane flame on the flashover characteristics of air, flashover voltages in accordance with the variation of the gap length and the horizontal distance between the flame and the high-voltage rod electrode were measured. As the result of the experiment, flashover voltages in the presence of the flame were substantially lowered than those in the absence of flame, and the polarity effects with the d.c. voltages on appeared owing to the flame. Flashover voltages of air were increased in the proportion of the gap length and the horizontal distance in the case of both a.c. and d.c. voltages, but the flame was extinguished by such corona wind that was produced from the rod electrode when the gap length and the horizontal distance reached to a certain degree.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.387-390
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• 2001

The experiments were performed in model conductors under the application of ac and dc high-voltages. The results of an experimental investigation into the flashover characteristics of air dielectric strength in the presence of oil/gas flame are reported. It is demonstrated that flame can reduce by more than half, 80% in maximum the breakdown voltage of a model line. Taking a horizontal model line with a k=0.5, it can be seen from the results that the reduction of flashover levels, in comparison with the no-flame case, are 78.7[%] for h=0[cm], 59.6[%] for h=3[cm], 46.4[%] for h=6[cm], 40.4[%] for h=9[cm] and 23.2[%] for h=12[cm] when ac voltage is applied.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2386-2388
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• 1999

This paper describes the surface discharge characteristics which can be used as data to determine the optimumal length in margin which plays an important role in improving the energy density and the life-time of high voltage capacitors. In this experiment, the margin of metalized polypropylene films(MPPFs) is varied in length in order to measure and analyze flashover voltages and partial discharge inception voltages (PDIVS). As a result, the flashover voltage and the PDIV are increased with margin and tracking was observed.