• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.244-247
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• 2004

The electrical insulating design is important to realize a HTS power cable because the cable is operated under the high voltage environment. For the insulation design of a HTS power cable, it is necessary to investigate the AC, impulse breakdown and partial discharge(PD) inception stress of liquid nitrogen/LPP composite insulation system. Based on these results, the electrical insulation of a HTS power cable is designed and Mini-model cables are manufactured. The manufactured Mini-model cables are evaluated that AC, impulse withstand voltage, breakdown and partial discharge inception stress and analyzed characteristics insulation of HTS cable bending condition according to this paper. From these tests, the AC, impulse withstand voltage test and partial discharge inception stress is satisfied "standard technical specification of KEPCO" in Korea and the breakdown voltage was 120kV.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.9
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• pp.32-39
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• 2008

This paper presents the soil ionization phenomena and the parameters with the transient characteristics of model grounding system under lightning impulse voltages. lonization properties of dry and wet sands were investigated by using two test cells of concentric cylindrical electrode system with different dimensions. As a result non-linear electrical behavior of sand under high impulse voltage is caused by ionization process. The transient impedance of sand depends not only on the water content but also on the magnitude of applied impulse voltages. The grounding impedance is decreased with increasing the water content and the magnitude of a lied voltages. The results resented in this paper will provide useful information on the design of high performance grounding systems against lightning surge.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1418_1419
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• 2009

This paper presents the transient impedance when high current impulse up to 5 kA is applied to a scaled grounding grid in test field. For a realistic analysis of transient impedance on the high current impulse in the ground systems, grounding electrode installed outdoors and impulse current generator was used. The results were discussed based on its voltage and current trace, impulse impedance and V-I curve.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.698-702
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• 1987

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.783-789
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• 2008

This experimental study describes the noise reduction and the feasibility of short current of a silencer for a high voltage COS(cut out switch) fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the strong impulse noise over 150 dB(A) is generated. For the purpose of the reduction of impulse noise, in this study, the diffuser type and the reactive type silencers have been designed and tested, respectively. And also the electrical test on the short current is performed. From the experimental results, the well designed reactive type silencer has been shown to have the noise reduction of about 20 dB(A). It has been found that the feasibility of short current for the COS fuse is closely related to the porosity of the silencer.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.756-760
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• 1988

The paper presents the measurement results on the parameters affecting the breakdown mechanism of a large air spacing under switching impulse voltages. Measured parameters are the velocities of leader channels, predischarge currents, electric charges injected into the rod-plane air gap and electric field intensities on the plane. For the 3m air gap under switching impulse voltages, the velocities of leader channel have been measured to be of 1cm/${\mu}s$ - 5cm/${\mu}s$, electric field intensity of 2kv/cm, predischarge current of 1.2A - 1.6A, the charges injected into the air gap of 11 - 40 ${\mu}$C for 400-887kV impulse voltages.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.301-304
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• 2008

This paper presents the experimental results on breakdown characteristics in $N_2$ gas under non-uniform electric fields caused by both the positive and negative lightning impulse voltages. $N_2$ gas have an advantage of eco-friendly and cost reduction, and safety aspects. In order to analyze the impulse pre-breakdown processes in $N_2$ gas, we carried out measurements and observations of the impulse breakdown voltages, pre-breakdown current and luminous signals. They were measured by a voltage divider, a shunt and a photo-multiplier tube, respectively. Additionally, the characteristics of discharge channels were observed by high speed cameras. The breakdown voltages in the positive polarity was lower than those in the negative polarity.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.101-109
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• 2002

The electrical properties of polyethylene are changed by the superstructure. Such crystalline polymer as polyethylene or polypropylene changes crystallinity and products spherulite or trans-crystal when it is cooled slowly. In this study, after thermal treatment of LDPE at 100[${circ}C$], in silicone oil for an hour, we made specimens in order of slow cooling, water cooling, quenching according to cooling speed. Also, to study the influence of electrical properties due to the superstructure change, we analyzed physical properties and performed dielectric breakdown experiments using DC and impulse voltage Moreover we measured space charges in bulk using Laser Induced Pressure Pulse(LIPP) method. Trap level of specimen is 0.064[eV] at the low temperature region 0.31[eV] at the high temperature region in DC dielectric strength, 0.03[eV] at the low temperature region 0.0925[eV] at the high temperature region in impulse dielectric strength. As its result shows that the quantity of charges induced from the electrode surface increases with applied voltage time, and the distribution of space charges in samples increases the quantity of charges in proportion to applied voltage.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.989-993
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• 2009

Triple junction which consists of three media(electrode, insulator, and gas) should be considered in designing of high voltage equipments due to the electric field enhancement. In this paper, positive lightning impulse breakdown voltage is predicted based on the streamer theory for simplified insulator models and 72.5kV spacer with varying the triple junction geometry and gas pressure, and the results are compared to the experimental results. The electric field coefficient concept is also applied in order to evaluate the partial discharge inception voltage and the surface flashover voltage from the streamer inception voltage. The application of this method using the constant electric field coefficient of 1.3 and 0.66 is possible for evaluating the triple-junction insulation of the simplified insulator and the 72.5kV spacer respectively. The error rate is under 10%.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.6
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• pp.96-103
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• 1997

This paper deals with the malfunction characteristics of the earth leakage circuit breakers(ELBs) applied by a lightning impulse voltage. In the cases of the regulation of KS C 4613 and the simulated circuits with surge protection devices, the dead operation characteristics of the ELBs against lightning impulse voltages were experimentally investigated and discussed. As a result, all the specimens(ELBs) used in this work have a cutoff performance of the lightning impulse voltage when the differential mode surges were injected at the input terminals of the ELBs owing to a surge absorber installed at the power source side of amplification circuit. Four kinds of the specimens have brought about malfunction in the condition of the lightning impulse dead operation test defined in KS C 4613, and the malfunction voltages are relatively high and are about 5-6.5[kV]. In the case of the simulated test circuit with surge protection devicesthree kinds of the ELBs have led to malfunction. Also the voltage level causing the malfunction of the ELBs is decreased by operation of surge protection devices, and it ranges from 3 to 5(kV).