• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1471_1472
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• 2009

In a wide variety of high-voltage applications surface flashover plays major role in the system's performance and yet has not been studied in great detail for vacuum conditions with modern diagnostic tools. surface flashover for both direct current and pulsed voltages in considered. within the setup, parameters such as geometry, material characteristics of the applied voltage can be altered. This paper review surface flashover of insulator, primarily in vacuum. It discusses theories and models relating to surface flashover and experimental results. surface flashover of insulators in vacuum generally is initiated by the emission of electrons from the cathode triple junction point (the region where the electrode, insulator, vacuum). the electrode material was copper, and a AC voltage was applied between the electrodes. these results were compared with the surface flashover characteristic of insulator at results, surface flashover influenced only insulator surface condition. and increasing vacuum pressure was risen breakdown voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.400-400
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• 2009

In a wide variety of high-voltage applications surface flashover plays major role in the system's performance and yet has not been studied in great detail for atmospheric conditions with modem diagnostic tools. surface flashover for both direct current and pulsed voltages in considered. within the setup, parameters such as geometry, material characteristics of the applied voltage can be altered. This paper review surface flashover of insulator, primarily in atmosphere. It discusses theories and models relating to surface flashover and experimental results. surface flashover of insulators in atmosphere generally is initiated by the emission of electrons from the cathode triple junction point (the region where the electrode, insulator, air). the electrode material was copper, and a AC voltage was applied between the electrodes. these results were compared with the surface flashover characteristic of epoxy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.70-76
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• 2003

For the development of superconducting power apparatus, it is necessary to establish the dielectric technology in coolant like L$N_2$. Therefore in this paper we conducted experiment of surface flashover that could occur in the windings of HTS transformer which will be developed in the pancake coil type. First, we distinguished two types of surface flashover by electrode alignment, such as parallel and vertical, and then compared with each characteristics of surface flashover. The flashover voltage was more affected by thickness of spacer than by surface length when the thickness of spacer is over 1 mm. And the surface flashover with metallic particle attached on the spacer was tested, it was affected by the particle position. The more close to the electrodes, the worse the characteristics. Also the experiment was conducted when the electrode was immersed in liquid nitrogen(L$N_2$) partially. The surface flashover characteristics of spacer was, when immersed partially in 50%, rapidly decreased.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.32-39
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• 2015

This paper presents the surface flashover mechanism of a laminated solid dielectric and describes the surface flashover characteristics with the inherent capacitance of the laminated solid dielectric in a $N_2/O_2$ mixture gas (8:2) under an quasi uniform field. It was found that the electron emission at a cathode and the high-local electric field region around an anode were important factors to reasonably describe the surface flashover mechanism. The surface flashover voltage by the mechanism decreased with the inherent capacitance increase of the laminated solid dielectric. In addition to the surface flashover mechanism and its characteristics, the surface flashover voltage equations as a function of the inherent capacitance were derived by considering a gas pressure used in future eco-friendly GIS and the factors influencing the surface flashover.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.961-968
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• 2016

The non-uniform distribution of contamination on insulator surface has appreciable effects on flashover voltage, and corresponding researches are valuable for the better selection of outdoor insulation. In this paper, two typical types of porcelain and glass insulators which are widely used in ac lines were taken as the research subjects, and their corrections of AC flashover voltage under non-uniform pollution were studied. Besides, their flashover characteristics under different ratio (T/B) of top to bottom surface salt deposit density (SDD) were investigated, including the analysis of flashover voltage, surface pollution layer conductivity and critical leakage current. Test results gave the modified formulas for predicting flashover voltage of the two samples, which can be directly applied in the transmission line design. Also, the analysis delivered that, the basic reason why the flashover voltage increases with the decrease of T/B, is due to the decrease of equivalent surface conductivity of the whole surface and the decrease of critical leakage current. This research will be of certain value in providing references for outdoor insulation selection, as well as in proposing more information for revealing pollution flashover mechanism.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.2
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• pp.317-321
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• 2021

As the large-scale renewable energy power plant increases, the high-capacity and compact Energy Storage System (ESS) is required. However, this trend could reduce the insulation reliability of ESS. In this study, the surface flashover characteristics for four types of solid insulators are investigated in the uniform electric field with AC and Lightning Impulse (LI) voltage waveforms under various contamination levels. In addtion, insulator surfaces are compared based on the contact angle before and after surface flashover. The experimental results show that AC flashover voltage is dependent on the materials and the contamination level, but LI flashover voltage is only associated with the contamination level. Especially, AC flashover voltage of PC (PolyCarbonate) is higher than that of other insulators, which is associated with the unique and sequential creepage discharge propagation pattern of PC. The localized discharges on the surface of PC form corresponding tracking points. Then, the interconnected trackings result in the complete flashover. This flashover patterns degrade the surface of PC much more than that of epoxy and Bulk Molding Compoud (BMC). Thus, the contact angle of PC is significantly reduced compared to that of other insulators. The increased hydrophilicity in the surface of PC enhances the insulator surface conductivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.420-423
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• 2002

In this paper the characteristics of surface flashover for high temperature superconducting transformer(HTS) was discussed. The transformer, will be developed in the shell type with double pancake coil, isn't developed yet in the world. We conducted experiment of surface flashover that could occur in the windings of the transformer. First, we distinguished the surface flashover with electrode alignment into two type, such as parallel and vertical, and then compared with each characteristics of surface flashover. And the surface flashover with metallic particle was tested, it was also affected by the particle position. .

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.119-123
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• 2002

In this study, we discussed the characteristics of breakdown and surface flashover of FRP in L$N_2$ for applying it to spacer of a superconducting power equipment. Fiberglass reinforced plastic(FRP) has high breakdown puncture strength and has high mechanical strength. So the research of its dielectric properties have been conducted in liquid nitrogen($LN_2$). We measured breakdown voltage of FRP and distinguished four types of surface flashover along solid insulator with arrangement of electrodes and measured the surface flashover voltages of each types of electrode arrangement. The type of a electrode set at the back of the insulator showed the worst dielectric property. The property of surface flashover depending on pressure was tested.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.2
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• pp.177-182
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• 2000

Composite insulation system of liquid nitrogen and solid spacer is widely applied in high temperature superconduction power machine. This study has three step procedure. As follow, first step is composition of parallel deposited electrode and vertically deposited electrode along the direction of immersion in liquid nitrogen(LN2). Second step is investigation into surface flashover voltage of solid spacer under partially immersed in LN2, and last step is comparison the result of this research with that of fully immersed in LN2 and at cryogenic temperature gaseous nitrogen(GN2). This result presented that surface flashover voltage along solid spacer half immersed in LN2 was almost the same as that of fully immersed spacer when the thickness of spacer(t) was t<10mm. In the case of t> 10mm, however, spacer flashover voltage was equal to that obtained in GN2 at cryogenic temperature. And the immersed direction functions as role of deciding the difference of surface flashover voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.530-537
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• 2008

This paper describes the results of a study on the tracking performance of outdoor insulating materials based on the rotating wheel dip test(RWDT). And, the influence of surface degradation was evaluated through such as measurement of the flashover voltage after and before tracking test, also aspects of surface degradation using scanning electron microscopy. The time to tracking breakdown of treated filled specimen is longer than untreated filled specimen. And, after the RWDT, the surface of specimen by adding untreated filler appeared heavy erosion. It was found that the addition to surface treated filler, the better tracking resistance. In the RWDT, the breakdown specimen is not affected by the dry flashover voltage, despite the fact that the surface degradation of tracking test has different state on each specimen. This suggests that wet flashover voltage play an important role in evaluating of tracking and erosion on the surface degradation in tracking test. And, the flashover voltage of specimen under wet conditions are greatly affected by the salt concentration and degree of degradation by the RWDT Because of hydrophobicity and degree of degradation by the RWDT, the flashover voltage of treated filled specimen is higher than that of untreated filled specimen. Different types of specimen may have different hydrophobicity and their surface state under contaminated conditions may not be the same.