• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.280-285
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• 2014

In order to evaluate the insulation deterioration in the stator windings of five gas turbine generators(137 MVA, 13.8 kV) which has been operated for more than 13 years, diagnostic test and AC dielectric breakdown test were performed at phases A, B and C. These tests included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ${\Delta}I$ and ${\Delta}tan{\delta}$ in all three phases (A, B and C) of No. 1 generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable and bad level to the insulation condition. Overall analysis of the results suggested that the generator stator windings were indicated serious insulation deterioration and patterns of the PD in all three phases were analyzed to be internal, slot and spark discharges. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. The breakdown voltage at phases A, B and C of No. 1 generator stator windings failed at 28.0 kV, 17.9 kV, and 21.3 kV, respectively. The breakdown voltage was lower than that expected for good-quality windings (28.6 kV) in a 13.8kV class generator. In the AC dielectric breakdown and diagnostic tests, there was a strong correlation between the breakdown voltage and the voltage at which charging current increases abruptly ($P_{i1}$, $P_{i2}$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.254-257
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• 1997

In this paper, we investigated the effects of gap length and tip radius influenced in breakdown of mineral based insulation oil Electrode system was needle-plane geometry It is to model conductive extrusions in oil filled electrical power apparatus. The tip radius of needle electrode was 5, 10, 20 and 25${\mu}{\textrm}{m}$, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. It was calculated electrical breakdown strength at tip using Mason\`s equation from breakdown voltage As gap lenght increased. breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by tole phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage. breakdown 7tr7ilgtll was higher wheal polarity of needle was negative than positive. It is because of the space charge effect ill accordance with the influence of liquid motion.

• Transactions on Electrical and Electronic Materials
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• v.14 no.1
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• pp.47-51
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• 2013

A high power MOSFET switch based on a 0.35 ${\mu}m$ CMOS process has been developed for the protection IC of a rechargeable battery. In this process, a vertical double diffused MOS (VDMOS) using 3 ${\mu}m$-thick epi-taxy layer is integrated with a Zener diode. The p-n+Zener diode is fabricated on top of the VDMOS and used to protect the VDMOS from high voltage switching and electrostatic discharge voltage. A fully integrated digital circuit with power devices has also been developed for a rechargeable battery. The experiment indicates that both breakdown voltage and leakage current depend on the doping concentration of the Zener diode. The dependency of the breakdown voltage on doping concentration is in a trade-off relationship with that of the leakage current. The breakdown voltage is obtained to exceed 14 V and the leakage current is controlled under 0.5 ${\mu}A$. The proposed integrated module with the application of the power MOSFET indicates the high performance of the protection IC, where the overcharge delay time and detection voltage are controlled within 1.1 s and 4.2 V, respectively.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.9-11
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• 2000

To increase the device linearities and the breakdown-voltages of FETs, Al$\sub$0.25/ Ga$\sub$0.75/AS / In$\sub$0.25/Ga$\sub$0.75/As / Partially doped channel FET(DCFET) structures are proposed. The metal- insulator -semiconductor (MIS) like structures show the high gate-drain breakdown voltage(-20 V) and high linearities. The devices showed the small ripple of the current cut-off frequency and the power cut-off frequency over the wide bias range.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.232-235
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• 2003

To realize the development of HTS power apparatus, various breakdown test of L$N_2$ should be carried out and the mechanism should be understood more. Moreover the dielectric design technology that the basic dielectric experimental data applied to the HTS power system should be developed. In this paper, the electric fields for the insulation design were calculated for example with the analysis of Weibull distribution. And V-t characteristics of L$N_2$ were discussed. Around the breakdown voltage the n values were less than 1.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.251-254
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• 2001

Internal and external forces may be applied on the power cable in the both process of transportation and installation. Even though the EHV power cables have the structure of metal sheath and plastic jacket etc. to minimize these negative influences, the unusual forces result in the unexpected deformation of the cable. Compressing moulded XLPE model cable sheets were prepared and locally dented with round-edge and square-edge tools. All data were analyzed employing Weibull distribution. The breakdown strength of dented molded specimens showed lower values than the normal ones by 10-60%.

• ETRI Journal
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• v.34 no.1
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• pp.134-137
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• 2012

Power metal-oxide semiconductor field-effect transistor (MOSFET) devices are widely used in power electronics applications, such as brushless direct current motors and power modules. For a conventional power MOSFET device such as trench double-diffused MOSFET (TDMOS), there is a tradeoff relationship between specific on-state resistance and breakdown voltage. To overcome the tradeoff relationship, a super-junction (SJ) trench MOSFET (TMOSFET) structure is studied and designed in this letter. The processing conditions are proposed, and studies on the unit cell are performed for optimal design. The structure modeling and the characteristic analyses for doping density, potential distribution, electric field, width, and depth of trench in an SJ TMOSFET are performed and simulated by using of the SILVACO TCAD 2D device simulator, Atlas. As a result, the specific on-state resistance of 1.2 $m{\Omega}-cm^2$ at the class of 100 V and 100 A is successfully optimized in the SJ TMOSFET, which has the better performance than TDMOS in design parameters.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.81-82
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• 2015

BIM has been a reliable construction project management tool to handle various kinds of construction information generated in the facility life cycle. To take these advantages, researchers have been promoted numerous studies in a residential, a commercial, and an educational facilities with a large number of on-going projects. However, despite running as the role of essential energy supplier, power plant related BIM research is relatively insufficient than others. In particular, due to the extending of the facility service period and the requirement of the complicated construction project management for 'overhaul' and 'repowering' in the power plant maintenance phase, the needs for using BIM have been increased gradually. For using BIM based maintenance, it is needed to consider an information collecting methods and necessary to develop an appropriate breakdown structure to share information. Therefore, 'EBS' is produced by reviewing the previous research related to BIM and analyzing the repair activities in the maintenance phase. Proposed 'EBS' must be useful not only a judgment between capital expenditure versus revenue expenditure but also appropriate maintenance strategies development for property management.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1193-1198
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• 2017

The IGBT structure developed in this paper is used as a high power switch semiconductor for DC transmission and distribution and it is expected that it will be used as an important electronic device for new and long distance DC transmission in the future by securing fast switching speed and improved breakdown voltage characteristic. As a new type of next generation power semiconductors, it is designed to improve the switching speed while at the same time improving the breakdown voltage characteristics, reducing power loss characteristics, and achieving high current density advantages at the same time. These improved properties were obtained by further introducing SiO2 into the N-drift region of the Planar IGBT and were compared and analyzed using the Sentaurus TCAD simulation tool.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1142-1145
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• 2004

ZnO surge arresters continuously endure the operating voltages during the operation course, and in the mean time, which need to withstand occasionally transient voltages of lightning and switching overvoltages. Under these voltages, the ZnO varistors inside arresters would have aging phenomena, one important result of aging phenomena is the increasing of resistive currents of varistors, which leads to the increasing of power losses of varistors. And the operating voltage is continuously applied on the ZnO varistors, there is a degradation phenomenon existing in ZnO varistors. When the degradation reaches a certain degree, then the arrester must stop operation. The degradation is related to the applied voltage ratio, the applied voltage ratio is high, the degradation is quickly. When the power loss is higher than the thermal dispersion ability of house of arrester, then the arrester will thermally breakdown. In this study the thermal stability characteristics of surge arresters for high power wil be discussed on the view point of watt losses and thermal breakdown.