• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.456-465
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• 2001

In this paper, breakdown voltages in $SF_6-N_2$ mixtures were experimentally investigated to understand characteristics of dielectric strength and physical phenomena in nonuniform field disturbed by a needle shape protrusion. The test voltages are the lightning impulse$(\pm1.2/44 \mus)$ and the damped oscillatory impulse$(\pm400 ns / 0.83 MHz)$ voltages which can be occurred by the operation of disconnecting switches in gas-insulated switchgears(GIS). The effects of the polarity and wave shape of the test voltages, and the gas pressure on the V-t characteristics were in detail examined. The V-t characteristic curves were measured in different two ways : (1) one is the method by taking the maximum voltage recorded at or prior to breakdown against the time to breakdown, that is, the Procedures recommended in IEC 60060-1, (2) the other is the method by taking the voltage at the instant of chopping against the time to breakdown. As a result, the V-t characteristics of $SF_6-N_2$ mixtures in nonuniform electric field were significantly affected by the polarity and wave shape of the applied voltages. The positive breakdown voltages resulted in lower breakdown voltages in the time ranges considered, and the V-t curves for the negative oscillatory impulse voltage were extended over the longer time range. For the lightning impulse voltages, the V-t curves obtained by IEC Pub. 60060-1 were nearly same with the V-t curves obtained by the voltage at the instant of chopping against the time to breakdown. It is clear that the actual breakdown voltages were much lower than the maximum voltages appearing at or prior to breakdown because of the displacement current produced as a result of the dV/dt during the oscillatory transient voltage app1ication. The scattering of the negative actual breakdown voltages was much larger than that of the positive.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.227-228
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• 2007

Although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/CF_4$ mixtures. At present study the breakdown characteristics of SFJCF4 mixtures in uniform field was performed. The experiments were carried out under AC and standard lightning impulse (SLI) voltages. The sphere-sphere electrode whose gap distance was 1 mm was used in a test chamber. $SF_6/CF_4$ mixtures contained from 0 to 100% $SF_6$ and the experimental gas pressure ranged from 0.1 to 0.4 MPa. The results show that addition of $SF_6$ to $CF_4$ increase AC and SLI breakdown voltages. Under AC voltages the breakdown voltages of each mixture were linearly increased according to the quantity of $SF_6$. However under SLI voltages the breakdown voltages of each mixture were similar.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.10 s.340
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• pp.9-18
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• 2005

Analytical expressions for breakdown voltages of abrupt $p^{+}n$ junction of Si, GaAs, InP and In$In_{0.53}Ga_{0.47}AS$ were induced. Getting analytical breakdown voltages, effective ionization coefficients were extracted using lucky drift parameters of Marsland for each materials. The results of analytical breakdown voltages followed by ionization integral agreed well with experimental result within 10$\%$ in error for the doping concentration in the range of $10^{14}cm\;^{-3}\~5\times10\;^{17}cm\;^{-3}$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.79-84
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• 2011

In this study, breakdown characteristics of a vertical sphere-plane air gap in the presence of combustion flame were examined under the application of a.c. and d.c. high-voltages in order to investigate the effect of flame on the dielectric strength of air. Propane gas is used as the fuel of the flame, and the temperature distribution of air around the flame is measured. The polarity effects for the d.c. voltages and breakdown voltages of air when applied both of a.c. and d.c. voltages were examined in the case of the variation of the gap length and the horizontal distance between the flame and the high-voltage sphere electrode. The influence of relative air density, electrification and shape changes of the flame as factors that affect the breakdown voltages were discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.131-136
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• 2011

This paper aims to examine the possibility of using an environmentally friendly $N_2$ as an alternative gas to $SF_6$. For this purpose, we have investigated breakdown characteristics of $N_2$ under impulse voltages in a quasi-uniform electric field gap. The 1.2/50[${\mu}s$] lightning impulse voltage, switching impulse voltages and oscillatory impulse voltages were applied at the test gap. The electric field utilization factor ranges from 0.5 to 0.8. The experimental data of $SF_6$ and $N_2$ acquired in the same experimental condition are presented in parallel for comparison. As a result, the breakdown voltages in $SF_6$ and $N_2$ are linearly increased with the gas pressure, also the breakdown voltages in $N_2$ are increased with increasing the gap distance and electric field utilization factor. The positive breakdown voltages are higher than the negative breakdown voltages. The nagative basic lightning impulse withstand level of 150[kV] in $N_2$ of about 0.5[MPa] is nearly equal to that in $SF_6$ of 0.15[MPa]. It is seen from the results obtained in this work that $N_2$ can be used as an eco-friendly alternative gas to $SF_6$ in distribution power equipment.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1334-1335
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• 2008

Although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/CF_4$ mixtures. At present study the breakdown characteristics of $SF_6/CF_4$ mixtures in uniform and nonuniform field was performed. The experiments were carried out under AC voltages. The sphere-sphere electrode whose gap distance was 1 mm was used and the point-plane electrode whose gap distance was 3 mm was used in a test chamber. $SF_6/CF_4$ mixture contained 20% $SF_6$ and 80% $CF_4$ and the experimental gas pressure ranged from 0.1 to 0.5 MPa. The results show that addition of $SF_6/CF_4$ mixtures increase AC breakdown voltages. In uniform field the breakdown voltages of gas were linearly increased according to the pressure. However in nonuniform field the breakdown voltages of gas were increased nonlinearly.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.1-9
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• 2004

Analytical expressions for breakdown voltages of abrupt pn junction in GaP, GaAs and InP of III-V binary semiconductors was induced. Getting analytical breakdown voltage, effective ionization coefficients were extracted using ionization coefficient parameters for each materials. The result of analytical breakdown voltages followed by ionization integral agrees well with numerical and experimental results within 10% in error.

• 전자공학회논문지 IE
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• v.44 no.1
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• pp.10-14
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• 2007

Analytical expression for breakdown voltages of InP diodes is induced by employing the effective ionization coefficient extracted from ionization coefficients for electron and hole in InP. The analytical results for breakdown voltage are compared with numerical and experimental results for the doping concentration, $N_D=6\times10^{14}cm^{-3}\sim3\times10^{17}cm^{-3}$. The analytical results show good agreement with the numerical data. Good fits with the experimental results are found for the breakdown voltages within 10% in error at each doping concentration.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1999-2001
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• 2000

Impulse breakdown voltage characteristics of sulphur-hexafluoride/nitrogen ($SF_{6}-N_{2}$) mixtures were presented. The applied voltages were the positive and negative lightning impulse (1.2/44${\mu}s$) and oscillating impulse ($0.4{\mu}s$/2.08MHz) voltages. The predischarge current was observed to clarify the breakdown mechanism. The electrode system was consisted of plane to plane configuration with a needle-shaped protrusion whose length and diameter are 10mm and 1mm. The measurements were carried out at the gas pressure of mixtures up to 0.5MPa with nitrogen concentrations varying from 5 to 20%. The electrical breakdown in $SF_{6}-N_{2}$ mixtures develops with steplike pulses in leader mechanism. The minimum breakdown voltages for the negative lightning and oscillating impulse voltages were higher than those for the positive.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.184-191
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• 2016

In recent years, there are a number of studies that have been carried out to explore the alternative for Mineral Oil (MO) as dielectric insulating fluid in transformers due to the increasing tight regulation on safety and environment. Vegetable oils have been identified as suitable candidate since it is biodegradable, non-toxic and high flash/fire points which ensure more in-service safety. Among the types of vegetable oils considered for transformers application are Palm Oil (PO) and Coconut Oil (CO). This paper presents an experimental study on the lightning breakdown voltages of PO and CO under non-uniform electric field based on needle-sphere electrodes configuration at 3 small gap distances. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The main focus of this study is to examine the lightning breakdown performance of RBDPO and CO under different test conditions and assess its suitability as dielectric insulating fluid in transformers. The effect of voltage polarities (positive and negative) and testing methods (rising-voltage, up-and-down and multiple-voltage) were investigated. The data obtained from all tests were analysed by Weibull distribution in order to determine the withstand voltages for each type of oils. It was found that the breakdown voltages of RBDPO and CO are comparable with MO under positive lightning impulse. Under negative lightning impulse, the breakdown voltage of MO is slightly higher than RBDPO and CO. There is no significant effect of testing methods and voltage polarities on lightning breakdown voltages of RBDPO and CO. Based on the statistical analysis, it is found that the breakdown voltages of RBDPO and CO at 1% probability are slightly lower than MO.