• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2166-2168
• /
• 2005

This paper presents the frequency - dependent characteristics of leakage currents flowing through ZnO varistor. The leakage current - voltage (V-I) characteristic curves of the commercial ZnO varistor were measured. The resistive leakage current was increased with increasing the magnitude and frequency of the applied voltage in the low conduction region. The power losses of ZnO varistor increase as the frequency of applied voltage increases, because of the dielectric loss related to the frequency of the test voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1994.05a
• /
• pp.63-66
• /
• 1994

This paper describes the developed sensor for measuring the time-varying magnetic fields and presents the characteristics of the magnetic fields and presents the characteristics of the magnetic field generated by lighting a fluorescent lamp. The frequency bandwidth of magnetic field measurement system is kknown as 40 Hz∼100 kHz by means of calibration experiment. The magnetic field waveform which originates from the various lighting systems was measured and the frequency components were analyzed by fast Fourier transformation technique. The magnetic field generated during the operation of the fluorescent lamp mainly includes the odd harmonics, and in the case\ulcorner of push button switch and high frequency starter types the fast transient component is occurred in an instant of lighting.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.254-255
• /
• 2007

This paper describes underwater discharge phenomena which are less studied than gas, solid and dielectric liquid. Since discharge phenomena were affected by various factors, we investigated the effect of water resistivity in point-plane gap by impulse voltage. In discharge photograph, it is hard to discover the streamer development in positive polarity at high reisistivity. On the other hand, the streamer originated at the tip of rod and developed toward the plane with increasing voltage. It is found that the breakdown voltage of both polarities in lower resistivity are lower than that of high resistivity. High current flowing in lower resistivity before the breakdown induce more streamer and enhance the probability of breakdown.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1436-1437
• /
• 2007

This paper presents the experimental results of the dielectric characteristics with temperature changes under highly non-uniform electric field in $SF_6$ gas. The impulse preliminary breakdown developments were investigated by the measurement of predischarge current and breakdown voltage. As a result, the first stremer corona is initiated at the tip of needle electrode, and bridges the test gap. Also the first stremer corona onset and breakdown voltages the negative polarity was much higher than that in the positive polarity in same temperature. In addition, the varition of temperature have a little effect on the positive polarity. On the other hand, in some cases negative polarity corona onset and breakdown voltages increased with increasing a high temperature.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.2
• /
• pp.363-369
• /
• 2017

This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2003.11a
• /
• pp.369-372
• /
• 2003

To obtain a low ground resistance in high resistivity soil or in insufficient place such as downtown, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flows into the grounding system, the ground impedance is remarkedly increased. This paper presents how the impulse and fault current works on the long. vertical ground rods associated with incoming points. When the test current was injected at the bottom of ground rod, the potential waveform of ground rod includes the oscillation with high frequency.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.338-341
• /
• 2006

This paper presents the leakage current characteristics of ZnO varistors exposed to the $8/20{\mu}s$ lightning impulse currents as functions of the number of injection and amplitude of impulse currents. The surge simulator system ECAT that can generate $8/20{\mu}s$ impulse currents with a peak short-circuit of $5[kA_p]$ was used. Leakage currents flowing through ZnO varistors subjected to the $8/20{\mu}s$ impulse currents were measured under 60 Hz AC voltages. The trend curves of resistive leakage current of ZnO varistors were analytically calculated.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.342-346
• /
• 2006

This paper describes ground surface potential rises and touch voltage. The more soil resistivity of upper layer is lower, the more ground surface potential rise is increased. Ground surface potential rise is increased as the buried depth of ground rod in lowered. Ground surface potential rises were measured in the test site and compared with results by CDEGS program. Touch voltages according to the separation distance of ground rod were measured in four directions. Touch voltages were remarkably changed by separation distance and contact position.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.347-350
• /
• 2006

The conception of early streamers is in sufficient and inadequate as a parameter for the determination of any advantage of early streamer emission(ESE) lightning rods versus ordinary lightning rods. Thus, standards for many other national and international lightning protection as well as KS C IEC 61024-1 do not take ESE lightning rods, charge dissipation systems or non-conventional lightning rods. Unfortunately, many non-conventional lightning rods such as ESE lightning rods and charge dissipation systems in Korea are increasingly used in lightning protection of structures including explosive manufacturing buildings, electric generating, transmission and distribution systems. This study attempts to make aware of no advantage of ESE rods and other non-conventional lightning protection systems and to investigate the present status of installations of ESE lightning rods.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.351-354
• /
• 2006

This paper deals with the potential interferences between ground rod and counterpoise. The ground potential rise and coefficient of potential interference were measured by using the hemispherical water tank grounding simulator and calculated from CDEGS program as functions of the configuration and size of grounding electrodes and the distance between grounding electrodes. The ground potential un and potential interference coefficient strongly depend on the distance between grounding electrodes, the arrangement and size of grounding electrodes.