• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.114-119
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• 2006

This paper reports the investigation results on the leakage currents (LC) on polymeric outdoor insulators. The samples used were EPDM (ethylene prophylene diene monomer) insulators used at 20 kV distribution lines. AC voltage was applied and the LC waveforms were measured under various environmental conditions (humidity and pollution). Digital data of the LC was transferred from a digital storage oscilloscope to a computer for further analysis. The LC waveform parameters such as magnitude and harmonic content (as indicated by the total harmonic distortion (THD)) were analyzed. The experimental results showed that 3rd, 5th and 7th harmonics and higher odd harmonics were observed for symmetrical-distorted LC waveforms while for unsymmetrical-distorted LC waveforms, odd and even harmonics were observed. The LC analysis indicated that there are 5 stages of insulator conditions from normal condition up to flashover correlated with different kind of LC waveforms. The results also showed that in general the magnitude of LC was good enough to show the condition of the insulators. However, under discharge condition (for example as a result of dry band arching) the LC magnitude should be combined by the THD to show a better correlation with the insulator condition. The product between THD and LC magnitude may be used as a diagnostic parameter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.3
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• pp.24-32
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• 2011

[ $SF_6$ ]gas, which has an excellent dielectric strength and interruption performance, is used in various applications such as gas insulated switchgear (GIS) in substations. However, since $SF_6$ has a high global warming potential (GWP), it is necessary to find an eco-friendly alternative insulation gas. In order to examine the possibility of using alternative insulation gases for $SF_6$ in power distribution system equipment, the dielectric strength and physical phenomena of dry air in a quasi-uniform electric field are investigated experimentally in this paper. As a result, the breakdown voltages for positive polarity are higher than those for negative polarity under impulse voltage applications. The negative 50[%] flashover voltage, $V_{50}$ of dry air under conditions above 0.4[MPa] gas pressure, is higher than 150[kV], that is the basic impulse insulation level of distribution equipment. The $V_{50}$ increases linearly with increasing the gas pressure, regardless of the waveform and polarity of the applied impulse voltages. The voltage-time curves are dependent on the rise time of the impulse voltage and gas pressure. Furthermore, streamer discharge was observed through light emission images by an ICCD camera under impulse voltage applications.

• Journal of the Society of Disaster Information
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• v.13 no.4
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• pp.529-536
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• 2017

In this study, the perceptions were surveyed fire risk and flash flames concerning the firefighters. The results were statistically evaluated according to age, experience and rank. More than 70% of the respondents answered that there is a possibility of unexpected flame exposure in the field of fire, but there was no recognition difference according to age, experience and rank. However, if there is an emergency situation in the field of fire, the survey on the ability to cope with crises showed that there is a difference in perception depending on the age, career, and rank of respondents. From these results, it is expected that strengthening simulation training of unexpected situation will be more urgently required in the future, and measures should be taken to minimize human accidents through improvement of standard operation procedures or supplement of fire suppression education according to unexpected situation.