• Transactions on Electrical and Electronic Materials
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• 제10권5호
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• pp.147-151
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• 2009

For integrated passive device (IPD) applications, we have successfully developed and characterized metalinsulator-metal (MIM) capacitors with 2000 $\AA$ plasma-enhanced chemical vapor deposition (PECVD) silicon nitride which are deposited with the $SiH_4/NH_3$ gas mixing rate, working pressure, and RF power of PECVD at $250^{\circ}C$. Five PECVD process parameters are designed to lower the refractive index and lower the deposition rate of $Si_3N_4$ films for the high breakdown electric field. For the PECVD process condition of gas mixing rate (0.957), working pressure (0.9 Torr), and RF power (60 W), the atomic force microscopy (AFM) root mean square (RMS) value of about 2000 $\AA$ $Si_3N_4$ on the bottom metal is lowest at 0.862 nm and the breakdown electric field is highest at about 8.0 MV/cm with a capacitance density of 326.5 pF/$mm^2$. A pretreatment of metal electrodes is proposed, which can reduce the peeling of nitride in the harsh test environment of heat, pressure, and humidity.

• 전기학회논문지
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• 제60권3호
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• pp.674-679
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• 2011

In this paper, we experimented and analyzed about electric fire risk assessment methods of LED lightings for outdoor. LED lighting is composed of AC power lines, AC/DC converter, DC power lines and LED lamps. There are some risk factors of electric fire in LED lighting such as short circuit between power lines or power line and ground, dielectric breakdown, leakage current, abnormal voltage inflow, poor contacts(connections), etc. As a result of this study, insulation coverings of wire was ignited due to dielectric breakdown between power lines and molten marks were formed in copper conductor. LED lighting was blown out while short circuit, beside that, electrical disorder did not occur. When abnormal voltage was inflowed, electronic components such as varistor, condenser were damaged. Partial heating was produced and insulation was melted and carbonized by arc and heating while poor contacts were happened. We expect that the results of this study would be helpful for electrical safety of LED lightings for outdoor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.46-48
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• 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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.200-203
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• 2006

Prior to destructive testing, diagnostic tests were performed in eight high voltage motors. Diagnostic tests included polarization index, ac current, dissipation factor($tan{\delta}$) and partial discharge magnitude. The rewind of motor stator insulation at rated voltage is assessed by the results of these tests. After completing the diagnostic tests, the stator windings of motors were subjected to gradually increasing ac voltage, until the insulation punctured. No. 1 motor failed near rated voltage of 12.96 kV. The breakdown voltage of No. 4 motor was 6.99 kV which is lower that expected for good quality coils in 6.6 kV class motors. The failure was located in a line-end coil at the exit from the core slot. These two motors began operation in 1994. While testing No. 7 motor, flashover occurred between the stator winding and the stator frame at 15 kV. The relationship between the diagnostic test and the drop in insulation breakdown voltage was analyzed.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.69-74
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• 2018

산업사회의 발달과 더불어 신뢰성 높은 양질의 전기에너지와 운전 및 보수의 간편화, 계통 운용의 신뢰성, 안전성 확보가 요구되고 있다. 본 논문에서는 각종 전력설비에서 SF6을 대체하여 사용되고 있는 친환경절연제 $N_2-O_2$ 혼합가스 고체 절연물의 절연파괴특성과 고체절연재로 사용되고 있는 테프론의 연면절연특성을 압력에 따른 특성을 확인하였다. 대기와 비슷한 성분비 일 때 상대적으로 절연파괴특성이 테프론의 연면절연특성이 안정화되며, Paschen 법칙에 의해 평등전계에 가까운 전극중의 기체의 절연파괴전압은 압력에 비례하여 높아지고 있음을 실험을 통하여 확인하였다. 연면절연파괴전압은 압력에 따라 선형적으로 증가하였으며, 혼합가스의 $O_2$ 가스 혼합비에 따라 절연파괴전압의 차이가 발생하였다. 이는 $O_2$ 가스의 전기적 부성기체의 영향과 분자 간 충돌거리에 의해 연면절연파괴전압이 달라졌고, 본 연구에서 분자 간 충돌거리의 영향이 더 크게 작용하였다. 연면절연특성에 따른 테프론에 적용 가능한 절연파괴전압 관계식을 산출하였다. 이러한 결과는 전력설비의 절연설계 시 기초자료로 사용될 수 있을 것이라 생각된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.241-244
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• 1991

In this paper, we introduced Silicon Oxynitride films deposited by Laser CVD, and evaluated the electrical breakdown of these films by TZDB(Time Zero Dielectric Breakdown) and TDDB(Time Dependent Dielectric Breakdown) test. In addition, high frequency C-V test was done in order to calculate hysterisis and flatband voltage(before and after electric field stress). Failure times against eletric field are examined and electric field accelation factor $\beta$ are obtained, and long term reliability was also described by extrapolating into life time in the operating voltage(5V). In this experiments, the deposited films with increased temperature represented small flatband voltage, hysterisis and favorable breakdown characteristics, this is why the hydrogen in the film was decreased and the film was densified, long term reliability was good in the laser CVD SiON films.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.772-777
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• 2012

Accidents caused by water absorption in water-cooled generator stator windings often occur all over the world. The absorption into the insulator of the coolant, which is used to cool down the heat generated by stator windings during operation, leads to the deterioration of dielectric strength, and insulation breakdown. An insulation breakdown may cause not only an enormous economic loss but also a very serious grid accident that would compromise stable supply of electric power. More than 50 % of domestic generators have been in operation for more than 15 years, and water absorption tests performed on 50 water-cooled generator stator windings during a five-year planned preventive maintenance period beginning in 2006 identified water absorption problems in 10 of them, all of which required repair. Because the existing water absorption test detects this problem by utilizing stochastic methods after measuring the capacitances at the final positions of insulation breakdown, its accuracy is limited. This study demonstrates that water absorption can be more accurately diagnosed by utilizing method along with a more precise one.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.10-14
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• 2013

We have clearly investigated with respect to the survival of the insulator at cryogenic temperature under the electrical stress. The breakdown and voltage-time characteristics of turn-to-turn models for point contact geometry and surface contact geometry using copper multi wrapped with polyimide film for an HTS transformer were investigated under AC and impulse voltage at 77 K. Polyimide film (Kapton) 0.025 mm thick is used for multi wrapping of the electrode. As expected, the breakdown voltages for the surface contact geometry are lower than that of the point contact geometry, because the contact area of the surface contact geometry is lager than that of the point contact geometry. The time to breakdown t50 decreases as the applied voltage is increased, and the lifetime indices increase slightly as the number of layers is increased. The electric field amplitude at the position where breakdown occurs is about 80 % of the maximum electric field value. The relationship between survival probability and the electrical stress at cryogenic temperature was evident.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.309-314
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• 2012

To assess the condition of stator insulation, nondestructive and overpotential tests were performed on four high voltage motors. The stator windings under these tests have nominal ratings of 6.6 kV. After completing nondestructive tests, the AC overvoltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No. 1, No. 2, No. 3 and No. 4 of 6.6 kV motors failed near rated voltage of 18.4 kV, 19.8 kV, 19.7 kV and 21.7 kV, respectively. The breakdown voltage of four motors was higher that expected for good quality coils(14.2 kV) in 6.6 kV motors. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor($tan{\delta}$) and partial discharge magnitude.

• Journal of Electrical Engineering and Technology
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• 제3권4호
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• pp.571-575
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• 2008

Stator insulation quality assessment for high voltage motors is a major issue for the reliable maintenance of industrial and power plants. To assess the condition of stator insulation, nondestructive tests were performed on the sixty coil groups of twelve motors. After completing the nondestructive tests, the AC voltage applied to the stator winding was gradually increased until insulation failure in order to obtain the breakdown voltage. The stator winding of each motor was classified into five coil groups; one group with healthy insulation and four groups with four different types of artificial defects. To analyze the breakdown voltage statistically, Weibull distribution was employed for the tests on the fifty coil groups of ten motors. The 50th percentile values of the measured breakdown voltages based on the statistical data of the five coil groups of ten motors were 26.1kV, 25.0kV, 24.4kV, 26.7kV and 30.5kV, respectively. Almost all of the failures were located in the line-end coil at the exit of the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of dissipation factor and ac current. It is shown that the condition of the motor insulation can be determined from the relationship between the probability of failure and the type of defect.