• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 E
• /
• pp.2136-2138
• /
• 1999

In this study, we describe the change of electrical properties of XLPE with electrical-tree degradation. XLPE insulation was used as specimen which was cut off from 22.9kV XLPE insulated cable and made in a type of block. The applying voltages are 8kV, 10kV, 12kV and frequency is 60Hz Ogra needles having tip radius of 10$\mu\textrm{m}$ were inserted in blocks. PD quantity and $tan{\delta}$ and DC current were measured from inception of tree to breakdown and their characteristics were analyzed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 E
• /
• pp.1711-1713
• /
• 1998

This paper describes the insulation characteristics of GIS by the free conducting particles under alternating voltage. The particles of the GIS can cause decrease in breakdown voltages. Various materials and sizes of free conducting particles were used to study the lift-off and fall-down characteristics. The measured lift-off voltage for copper particle agreed with the calculated one.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.321-326
• /
• 2008

Light weight of vehicles by composite materials makes possible high speed, energy saving, and low repair cost. As Bimodal Tram and Tilting Train eXpress(TTX) use carbon composite material for their bodies, safety for passengers and electrical devices against unexpected failures has been issued more than ever. Lightning strike which generates high voltages and large currents is the worst case for the safety of passengers and devices. With this background, we experimentally investigated the insulation breakdown phenomena on carbon composite materials by the application of lightning surge voltage and current. From the experimental results, we could estimate whether the composite body is safe or not for the inside passengers and devices against lightning strikes.

• 전자공학회논문지A
• /
• 제33A권4호
• /
• pp.106-111
• /
• 1996

Schottky diodes are fabricated on laser annealed and unannealed polysilicon substrate and their electrical characteristics are studied and analyzed. Current of laser annealed devices are larger than that of unannealed devices because of grain growth, decrease of grain boundary and trap density, lowering of grain boundary barrier height, decrease of dopant segregation. At low forward bias (<0.7V), currents of unanealed devices are larger. Soft breakdown voltages of laser annealed devices are larger than that of unannealed devices.

• 한국전기전자재료학회논문지
• /
• 제24권4호
• /
• pp.261-265
• /
• 2011

This paper describes the fabrication and characteristics of a Au/Ni/Ti/3C-SiC Schottky diode with field plate (FP) edge termination. The Schottky contacts were annealed for 30 min at temperatures ranging from 0 to $800^{\circ}C$. At annealing temperature of $600^{\circ}C$, it showed an inhomogeneous Schottky barrier and had the best electrical characteristics. However, the annealing of $800^{\circ}C$ replaced it with ohmic behaviors because of the formation of many different types of nickel silicides. The fabricated Schottky diode had a breakdown voltage of 200 V, Schottky barrier height of 1.19 eV and worked normally even at $200^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1997년도 추계학술대회 논문집
• /
• pp.480-483
• /
• 1997

This paper describes dielectric characteristics and discharge development mechanisms of SF$_{6}$ gas stressed by very fast transient overvoltages in inhomogeneous electric field. Predischarge phenomena of SF$_{6}$ gas in non-uniform fields are statistically investigated with positive and negative very fast trannsient overvoltages. It was confirmed that all of the predischarges of the positive and negative polarities develop in a regime of stepwise leader extension. i.e, the predischarge developments leading to breakdown against very fast transient overvoltages are similar to the non-oscillating impulse voltages.ges.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
• /
• pp.282-284
• /
• 1996

This paper presents prebreakdown characteristics of $SF_6$ gas stressed by the non-oscillating and oscillating impulse voltages in inhomogeneous fields disturbed by metallic protrusion. The purpose of this investigation is to present the predischarge development and dielectric characteristics of $SF_6$ gas under VFTOs. The experiments were carried out using a needle-to-plane gap geometries in the gas pressure ranges from 0.1 to 0.5 MPa. The gap separation was22 mm, and the needle-shaped protrusions were made of stainless steel 10 mm in length and 1.0 mm in diameter. As a result, it was found that the breakdown mechanism and predischarge current are principally dependent on applied voltage waveform and polarity.

• 전기학회논문지
• /
• 제57권4호
• /
• pp.648-652
• /
• 2008

Corona discharge and ozone generation characteristics of a wire-plate plasma reactor, with a biased third electrode, have been investigated with an emphasis on the role of the bias voltage and frequency applied on the third electrode. It was found that the wire-plate plasma reactor, with the biased third electrode, had a switching characteristic on its I-V characteristics for negative and positive discharges, which is very different from that of a conventional wire-plate plasma reactor without the third electrode. As a result, the corona discharge and ozone generation characteristics of the proposed plasma reactor could be controlled by adjusting the bias voltage and frequency of the third electrode. The corona onset and breakdown voltages, and ozone generation and yield, were increased compared with those of without the third electrode. These, however, reveal the effectiveness of the biased third electrode.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.975-976
• /
• 2007

Thermal and mechanical stresses, caused by repetitive start and stop and load fluctuation during long time operation, on winding stator bars are one of the main causes for electrical degradation of insulating materials. To understand the degradation process, we manufactured bar specimens with the same processes that make generator winding stator bars and the specimens were subjected to various degrees of thermal cycling. Measurements of the insulation properties, such as dissipation factor, tip-up and partial discharge, for un-aged specimens and for specimens aged by thermal cycling at 50, 100, 250, 500 and 1000 thermal cycles were performed. Finally all specimens were tested to obtain electrical breakdown voltages. In this paper we present the data and electrical degradation analysis results obtained during this program.

• 공학논문집
• /
• 제6권2호
• /
• pp.33-38
• /
• 2004

To investigate the reliability of the MTJs on the roughness of insulating tunnel barrier, we prepared two MTJs with the different uniformity of barrier thickness. Namely, the one has uniform insulating barrier thickness; the other has non-uniform insulating barrier thickness as compared to different thing. As to depositing amorphous layer CoZrNb under the pinning layer IrMn, we achieved MTJ with uniform barrier thickness. Toinvestigate the reliability of the MTJs dependent on the bottom electrode, time-dependent dielectric breakdown (TDDB) measurements were carried out under constant voltage stress. The Weibull fit of out data shows clearly that $t_{BD}$ scales with the thickness uniformity of MTJs tunnel barrier. Assuming a linear dependence of log($t_{BD}$) on stress voltages, we obtained the lifetime of $10^4$years at a operating voltage of 0.4 V at MTJs comprising CoNbZr layers. This study shows that the reliabilityof new MTJs structure was improved due to the ultra smooth barrier, because the surface roughness of the bottom electrode influenced the uniformity of tunnel barrier.