• Title/Summary/Keyword: flash-over

Search Result 189, Processing Time 0.026 seconds

Theoretical consideration on some method of improving surface flash over discharge characteristics (연면섬락특성의 한 개선방법에 대한 이론적 고찰)

  • 정성계
    • 전기의세계
    • /
    • v.18 no.1
    • /
    • pp.7-10
    • /
    • 1969
  • This paper shows theoretically the possibility of raising up the flash over voltage in suspension insulators or bushing according to the results which was gotten by previous study done by the Author. If some conducting metallic barriers are inserted into the flash over discharge path, the flash over voltage is forund to be increased condiferablly. Applying this priciple, some methods of improving flash over characteristics are discussed theoretically.

  • PDF

A study on the effects of a conducting metallic barrier on the surface creepage flash over discharge (연면방전에 미치는 도전층의 영향에 관한 연구)

  • Sung Kae Chung
    • 전기의세계
    • /
    • v.17 no.3
    • /
    • pp.7-28
    • /
    • 1968
  • When a insulator plate is inserted to the discharge path of a space discharge gap in which the field strength is not uniform, the spark voltage under the atmospheric pressure between the electrodes decreases or rises according to the position of the insulating plate. Also it is reported that if a metallic barrier plate is inserted to the discharge path of the same space discharge gap, similar variations of spark voltage are found. Speaking briefly, mensioned above are the spark voltage characteristics when an insulator or metallic barrier is inserted to the space discharge gap. Also some experimental results, concerning to the surface creepage flash over characteristics at the case when an insulator barrier is inserted to the discharge path of a surface creepage discharge gap, were reported by Peek. But up to now there are no reports on surface flash over voltage characteristics at the case when a metallic barrier is inserted to the surface creepage gap. In this study the effects of a conducting metallic barrier inserted to the path of a surface creepage discharge gap on the flash over voltage characteristics are investigated theoretically and experimentally, and got some important results, clearing the effects of the position and width of a conducting barrier is inserted, the surface flash over voltage characteristics appear as an Inverse N or W Characteristics. Such theoretical or experimental results may have some relation not only with the effects of dry belt and snow on suspension insulators, but also with the effects of dirty zone or water drops on the surface creepage flash over voltage.

  • PDF

A Study of Particle-Initiated Breakdown Characteristics on a Spacer Surface for $SF_6$ GIS ($SF_6$ GIS용 스페이서 표면에서의 파티클에 의한 절연파괴 특성연구)

  • Kim, Jae-Ho;Lee, Yong-Gil;Kim, Dong-Eui;Lee, Sae-Hun;Kim, Jung-Dal
    • Proceedings of the KIEE Conference
    • /
    • 1994.07b
    • /
    • pp.1536-1539
    • /
    • 1994
  • The influence due to metallic particle contaminated on spacer surface is remarkable in the decreasing of dielectric strength in $SF_6$ GIS. In relation with this problem, We studied, AC flash-over voltage characteristics and breakdown mechanism are investigated under metallic particle initiated condition in $SF_6$ gas by varying the particle position, particle shape with a plane-plane electrode. The main results arc as follows 1. The small amount of the metallic particle in the gap do not make flash-over voltage to be influence, but the significant decrease of th flash-overed voltage is result in case of the big and long size of the metallic paraticle. 2. Influence of the flash-over voltage are lowest in the mid and are highest in the electrode of metallic particle position. 3. In case of the initiated metallie particle, The more the pressure are high, the more the recluced ratio of flash-over voltage are high. 4. The metallic particle shape which results in the reduced flash-over voltage forced the critical pressure to move in to the region of low pressure. 5. The existance of the metallic particle on the upper electrode side and high pressure make the decreasing ratio of flash-over voltage bigger than that of the ground side electrode.

  • PDF

Prediction of Flash Over and Characteristics Operation of Sprinkler RTI in Compartme nt Fire (아파트형 공장 구획 공간 화재시 Flash Over 예측과 Sprinkler RTI 작동특성)

  • 진복권;정수일
    • Journal of the Korea Safety Management & Science
    • /
    • v.5 no.1
    • /
    • pp.1-12
    • /
    • 2003
  • In this paper, computer simulation was used for researching into the estimate of flash over result from compartment fire and the characteristics operation of sprinkler RTI. Computing simulation, we analyzed and verified the path of the flame in compartment fire and the adaptation of sprinkler system concerned with sprinkler RTI.

The Effect of Metallic Barrier on the Surface creeping Flash-over Voltage along the Insulation Materials (절연물의 연면섬락 전압에 미치는 금속 격벽의 영향)

  • Sung Kae Chung
    • 전기의세계
    • /
    • v.14 no.2
    • /
    • pp.8-13
    • /
    • 1965
  • It is expected that the impurities contained in a solid state insulation material will affect a considerable influence on its break-down voltage, dielectric loss, and insulation resistance. In this thesis, as a preliminary experimental research for the investigation described above, the effect of metalic barrier between the electrodes on the creepin flash over discharge voltage along the surface of a solid insulation material has been investigated, and got some interesting results. It was found that generaly the flash over voltage rises when a metalic barrier is located between the electrodes. The results of this investigation will be taken into account as an important components on the insulation design to prevent the creeping flash over discharge in insulators, bushings, and so on.

  • PDF

The Particle-Initiated Breakdown Characteristics on the Spacer Surface for $SF_6$GIS ($SF_6$GIS용 스페이서 표면 파티클에 의한 절연파괴 특성)

  • 김정달;이세훈
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.12 no.1
    • /
    • pp.3-11
    • /
    • 1998
  • The influence due to particle contaminated on spacer surface is remarkable in the decreasing of dielectric strength in SF6 GIS. In relation with this problem, We studied, AC flash-over voltage characteristics and breakdown mechanism are investigated under metallic and insulating particle initiated condition in SF6 gas by varying the particle position, particle shape with a plane-plane electrode. The main results are as follows $\circled1$ Influence of the flash-over voltage decrease for particle position is lowest in mid gap and is highest in separated small gap on electrode. $\circled2$ The metallic particle shape which results in the more reduced flash-over voltage, the FOV saturation moved in to the region of low pressure. $\circled3$Insulating particle less than 0.6[mm] are not almost influenced by the flash-over Voltage.oltage.

  • PDF

Estimation of the Flash Flood Index by the Probable Rainfall Data for Ungauged Catchments (미계측 유역에서의 확률강우에 대한 돌발홍수지수 산정)

  • Kim, Eung-Seok;Choi, Hyun-Il;Jee, Hong-Kee
    • Journal of the Korean Society of Hazard Mitigation
    • /
    • v.10 no.4
    • /
    • pp.81-88
    • /
    • 2010
  • As there occurs recently and frequently a flash flood due to the climate change, a sudden local flood of great volume and short duration caused by heavy or excessive rainfall in a short period of time over a small area, it is increasing that significant danger and loss of life and property in Korea as well as the whole world. Since a flash flood usually occurs as the result of intense rainfall over small steep slope regions and has rapid runoff and debris flow, a flood rises quite quickly with little or no advance warning to prevent flood damage. The aim of this study is to quantify the severity of flash food by estimation of a flash flood index(FFI) from probability rainfall data in a study basin. FFI-D-F(FFI-Duration-Frequency) curves that present the relative severity of flash flood are developed for a study basin to provide regional basic information for the local flood forecasting and warning system particularly in ungauged catchments. It is also expected that FFI-D-F curves can be utilized for evaluation on flash flood mitigation ability and residual flood risk of both existing and planned flood control facilities.

Design and Implementation of the Mobile Flash for Flash Game on Mobile Terminals (휴대 단말기에서 플래시 게임을 위한 Mobile Flash의 설계 및 구현)

  • Oh, Hwang-Seok;Lee, Jae-Young;Kim, Man-Soo;Lee, Chung-Hwan
    • Journal of Korea Game Society
    • /
    • v.5 no.3
    • /
    • pp.11-16
    • /
    • 2005
  • As an improvement of the CPU performance of mobile terminals and an increase of user requirements for multimedia services, various multimedia services and applications have been developed and served over mobile platforms. In this paper, we describe the design and implementation of the Mobile Flash which is one of the famous services in mobile platforms with the limitation of hardware resources. The Mobile flash is an optimized solution for mobile terminals of the Flash, which has been used in the Internet browsers not less than 95% in the world for playing various types of contents such as animations, games, contents for education, e-commerce.

  • PDF

Simulation and validation of flash flood in the head-water catchments of the Geum river basin

  • Duong, Ngoc Tien;Kim, Jeong Bae;Bae, Deg-Hyo
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2021.06a
    • /
    • pp.138-138
    • /
    • 2021
  • Flash floods are one of the types of natural hazards which has severe consequences. Flash floods cause high mortality, about 5,000 deaths a year worldwide. Flash floods usually occur in mountainous areas in conditions where the soil is highly saturated and also when heavy rainfall happens in a short period of time. The magnitude of a flash flood depends on several natural and human factors, including: rainfall duration and intensity, antecedent soil moisture conditions, land cover, soil type, watershed characteristics, land use. Among these rainfall intensity and antecedent soil moisture, play the most important roles, respectively. Flash Flood Guidance is the amount of rainfall of a given duration over a small stream basin needed to create minor flooding (bank-full) conditions at the outlet of the stream basin. In this study, the Sejong University Rainfall-Runoff model (SURR model) was used to calculate soil moisture along with FFG in order to identify flash flood events for the Geum basin. The division of Geum river basin led to 177 head-water catchments, with an average of 38 km2. the soil moisture of head-water catchments is considered the same as sub-basin. The study has measured the threshold of flash flood generation by GIUH method. Finally, the flash flood events were used for verification of FFG. The results of the validation of seven past independent events of flash flood events are very satisfying.

  • PDF

Flash Drought Onset and Development Mechanisms Using Flash Drought Intensity Index (FDII) Based on Satellite-Based Soil Moisture (위성영상 토양수분 기반 FDII를 활용한 돌발가뭄의 메커니즘 분석)

  • Lee, Hee-Jin;Nam, Won-Ho;Sur, Chanyang;Jason A. Otkin;Yafang Zhong;Mark D. Svoboda
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.65 no.3
    • /
    • pp.57-67
    • /
    • 2023
  • A flash drought is a rapid-onset drought that develops over a short period of time as weather and environmental factors change rapidly, unlike general droughts, due to meteorological abnormalities. Abnormally high evapotranspiration rates and rapid declines in soil moisture increase vegetation stress. In addition, crop yields may decrease due to flash droughts during crop growth and may damage agricultural and economic ecosystems. In this study, Flash Drought Intensity Index (FDII) based on soil moisture data from Gravity Recovery Climate Experiment (GRACE) was used to analyze flash drought. FDII, which is calculated using soil moisture percentile, is expressed by multiplying two factors: the rate of intensification and the drought severity. FDII was developed for domestic flash drought events from 2014 to 2018. The flash drought that occurred in 2018, Chungcheongbuk-do showed the highest FDII. FDII was higher in heat wave flash drought than in precipitation deficit flash drought. The results of this study show that FDII is reliable flash drought analysis tool and can be applied to quantitatively analyze the characteristics of flash drought in South Korea.