• Transactions on Electrical and Electronic Materials
• /
• v.16 no.3
• /
• pp.146-150
• /
• 2015

Insulation breakdown voltage and insulation lifetime were investigated in straight lines or twisted pairs with polyesterimide-polyamideimide enameled round wires (EI/AIW ). The enamel thickness was 50 μm and the conducting copper radius was 0.50, 0.75, 1.09, and 1.50 mm, respectively. There were many air gaps in a twisted pair therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge according to Paschen's law. Insulation breakdown voltage and insulation lifetime were highest in the sample of 0.75 mm conductor radius, which was higher than those values for 0.50 mm or 1.09 and 1.55 mm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.699-702
• /
• 2000

Today, electrical machine is being large capacitor and EHV(Extra High Voltage) of power equipment is a need of high reliability of insulating matetials. Therefore, it is a need of fixed appraisement of lifetime to used data of breakdown. This paper studied a development of the program for estimation the lifetime of insullating materials and the long-time breakdown voltage by experimentation. The estimation program is based on the "Inverse Power Law", defined V$\^$n/t is constant. After gaining the life exponent n, it is mapping the long-time breakdown voltages. On the base of life exponent, the estimation of lifetime and usefulness of the insulation systems are possible, furthermore easy calculation is possible.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.5
• /
• pp.297-301
• /
• 2016

The effects of ambient temperature and diameter on the insulation lifetime of winding coils prepared with polyamideimide (PAI), flexural PAI (nanosilica 5 wt%) and anti-corona PAI (nanosilica 15 wt%) wires were investigated. The winding coils were made of enameled wire with enamel thickness of 30~50 μm. The thickness and width of the rectangular copper wires were 0.77~0.83 mm and 1.17~1.23 mm, respectively. The insulation breakdown lifetime decreased with increasing ambient temperature regardless of wire type and winding coil diameter under an inverter surge of 1.5 kV/20 kHz. The insulation breakdown lifetimes of φ5 mm winding coils at 150, 200, and 250℃ were 11.38, 5.19, and 4.22 min respectively, and those of φ10 mm winding coils at 150, 200, and 250℃ were 11.32, 5.79, and 4.57min respectively. The winding coil diameter had little effect on the insulation lifetime.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.9
• /
• pp.628-633
• /
• 1999

Degradation diagnosis of XLPE insulated URD cables was accomplished through out new method, which was to be analyzed by non-electrical experiments and synthesized by degradation points. To supplement this method, It was also carried out using several electrical analyses. Tan$\delta$ had commonly a different tendency by means oftemperature and frequency and also appeared higher at the outer part rather than innerpart of insulator. PD-q increased generally in proportion to the applied voltage andshowed regular patterns in relation to the thickness of insulator. Breakdown voltageswere measured and breakdown lifetimes were predicted appling for Weibull distribution function. As a result, breakdown lifetime in failure cables was shorter up to$\fraction one-third$ times than that in general cables. It was very available to estimate cable degradation using above method, but it needs further study on XLPE insulated URD cables in order to improve reliability.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.2
• /
• pp.840-845
• /
• 2017

In this paper, in order to investigate the lifetime of oil-paper insulation, specimens were artificially aged with thermal and electrical multiple stresses. Accelerated ageing factors and equivalent operating years for each aging temperatures were derived from results of tensile strengths for the aged paper specimens. Also, the evaluation for the multi-stress aged specimens were carried out through the measurement of impulse breakdown voltage at high temperature of $85^{\circ}C$. The lifetimes of the oil-paper insulations were calculated with the value of 66.7 for 1.0 mm thickness specimens and 69.7 for 1.25 mm thickness specimens throughout the analysis of impulse BD voltages using equivalent operating years, which means that dielectric strengths would not be severely decreased until the mechanical lifetime limit. Therefore, for the lifetime evaluation of the oil-paper insulation, thermal aging would be considered as a dominant factor whereas electrical degradation would be less effective.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.11
• /
• pp.1003-1008
• /
• 2002

In this paper, the estimation of lifetime with the various conditions of the interface between toughened epoxy and rubber which are consisting materials of underground power delivery system has been studied. After the measurement of the short time AC interfacial breakdown strength on macro interfaces at room temperature, the breakdown time at several voltages were measured under the constant voltages lower than the short time breakdown voltage. The long time breakdown voltage was calculated by using Inverse Power Law. Two types of interfaces was studied. One was the interface between toughened epoxy and EPDM(Ethylene Prorylene Diene Terpolymer). The other was the interface between toughened epoxy and silicon rubber. Interfacial pressure and roughness of interfaces was determined through the characteristic of short time AC interfacial breakdown strength. Oil condition was no oiled, low viscosity oiled and high viscosity oiled. High viscosity oiled interface between Toughened epoxy and silicon rubber had the best lifetime exponent, 20.69. and the breakdown voltage of this interface after 30 years was evaluated 19.27㎸.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.4
• /
• pp.346-353
• /
• 2012

The Laser-Induced Breakdown Spectroscopy (LIBS) has great advantages as an analytical technique, namely real-time analysis without sample preparation, ideal for mobile chemical sensor for space exploration. The LIBS plasma characteristics are strongly dependent on the surrounding pressure. In this study, seven types of target (C, Ti, Ni, Cu, Sn, Al, Zn) were investigated for their elemental lifetime. The target was located in vacuum chamber which has the pressure range of 760 to $10^{-5}$ torr. As the pressure is decreased, the elemental lifetimes of carbon and titanium declined, while all other targets showed increased lifetimes until reaching 1 torr and declined with continued pressure decrease. The boiling point and electronegativity amongst the physicochemical properties of the samples are used to explain this peculiarity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.222-225
• /
• 1999

Degradation diagnosis of XLPE insulated URD cables was accomplished through out new method. which was to be analyzed non-electrical experiments and synthesized by degradation points. To supplement this method, it was also carried out using several electrical analyses. Breakdown voltages were measured and breakdown lifetimes were Predicted appling for Weibull distribution function. As a result, breakdown lifetime in failure cables was shorted up to 1/3 times than that in general cables. It was very available to estimate cable degradation using above method, but it needs further study on XLPE insulated URD cables in order to improve reliability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.05a
• /
• pp.46-49
• /
• 2000

This paper studied development of the program for estimation the life time of insullating materials and the longtime breakdown voltage. First, short-time breakdown voltage of Epoxy and insulating oil was measured. Life exponent was gained from measurement of insulating breakdown time of the specimens. Life time is presumed from program. The estimation program is based on the "Inverse Power Law", defined $V^nt$ is constant. After gaining the life exponent n, it is mapping the longtime breakdown voltages. On the base of life exponent, the estimation the lifetime and usefulness of the insulation systems are possible, furthermore easy calculation is possible.

• Proceedings of the KIEE Conference
• /
• 2004.11a
• /
• pp.46-48
• /
• 2004

A micro-scale discharge device has been fabricated using MEMS technology and failure mechanisms during DC discharge are investigated for the microstructure. The failure of sustaining the plasma is mainly caused by either open or short of the micro-electrodes, both resulting from the sputtered metal atoms during the DC discharge. The glow discharge lifetime of the microstructures is found to depend on bias circuit scheme as well as the electrode structure. Based on the understanding of the failure mechanism, a novel microstructure is suggested to improve discharge lifetime and the longer lifetime is experimentally demonstrated. In addition to the failure mechanism, an electric breakdown between two electrodes with microns gap are studied using micromachined metal structures. The electrode gap is able to be accurately controlled by thickness of a sacrificial layer and the electric breakdown was measured while varying the gap from $2{\mu}m$ to $20{\mu}m$. The electric breakdown behavior was found to highly depend on the electrode material, which was not considered in Paschen's law.