• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.225-226
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• 2005

In this Study, we have acquired 5-simulation Fault types Signals of high voltage Motor stator winding using epoxy/mica coupler. In order to know stator winding fault type using fault signals, we have performed feature extraction to apply wavelet transform technique. we have obtained skewness and kurtosis as statistical parameters of fault signal pattern from non deterioration state winding. We have know that 5 fault signals types have done an exponential function pattern shape but individually fault a class widely was different each other a signal waveform of pattern.

• Polymer(Korea)
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• v.25 no.5
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• pp.691-698
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• 2001

Nanocomposites based on epoxy acid nanoclay were prepared employing organically modified mica type silicate (OMTS), diglycidyl ether of bisphenol A (DGEBA) type epoxy. curing agent (dicyandiamide; DICY), and catalyst (benzyl dimethyl amine; BDMA). Both melt mixing and solution mixing were und for the sample preparation and structural developments with curing reaction were analyzed using X-ray diffractometer (XRD) and small angle X-ray scattering (SAXS). Because of the different curing rate between extra-gallery and intra-gallery reactions of epoxy mixtures, only intercalated structure was observed for the sample prepared by melt mixing while fully exfoliated structure was observed for the sample prepared by solution mixing. Mechanical properties of exfoliated epoxy nanocomposite were investigated using a dynamic mechanical analyzer (DMA). The dynamic storage modulus of the nanocomposite in both glass and rubbery plateau regions were increased with increasing OMTS contents, but glass transition temperatures ($T_g$) remained unchanged. Thermal properties of epoxy nanocomposite were investigated using thermogravimetric (TGA) and limit oxygen index (LOI) methods. Thermal decomposition onset points and LOI values were increased with increasing OMTS contents due to barrier effects of OMTS sheets.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05d
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• pp.38-42
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• 2003

The use of VPI impregnated mica tape as high voltage insulation for large rotating electric machines requires a careful balance of processes and materials to obtain the desired electrical, mechanical and thermal characteristics. The stator insulation systems such as epoxy bonded high voltage mica tape have been produced for many years. One such system employing an epoxy and anhydride impregnating resin developed by Hyundai Heavy Industries, Co. (hereafter, HHI), to satisfy customer requests for an epoxy bonded insulation system. HHI applies the following electrical and thermal evaluations such as dielectric breakdown, voltage endurance, dissipation factor vs. temperature, isothermal weight loss, and so on. A detailed laboratory evaluation can describe specific physical limitations for an insulation system and permit development of long-term operation guidelines that permit full utilization of the proposed system. HHI has found these evaluations very helpful in qualifying insulation system for the repair of both large motors and generators.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.87-87
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• 2010

Epoxy/mica has been used as the material of high-voltage rotator stator winding due to its high insulation performance, mechanical strength, and thermal stability. In recent years, however, it shows frequent changes in the load of generators and frequent automatic stops due to the significant increase in peak loads from the increase in the applied load of power facilities according to the introduction of advanced and high-technology equipments. Thus, it is necessary to develop new materials that highly develop the conventional insulation materials. Nanotechnology introduced in the present time has become an alternative plan that overcomes such technical limitations. In addition, the nano-scaled intercalation composite has been known as the material that represent excellent electrical, mechanical, and thermal characteristics compared to the conventional materials. This study investigated the dielectric dispersion and relaxation characteristics of the nanocomposite, which was fabricated by mixing epoxy matrix with nano-scaled intercalation mica and clay, according to changes in frequencies and temperatures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.330-333
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• 1997

The thermal impact of mica/epoxy paper(130${\mu}{\textrm}{m}$) is investigated using XRD, DSC and TGL X-ray diffraction(XRD) analysis was performed to know the position and structure of mica crystal in insulation materials. A differential scanning calorimeter(DSC) was used to measure glass transition temperature and excess enthalphy of the composite materials that had been subjected to thermal aging. The glass transition temperature(T$_{g}$) measured by DSC is observed at 95.43$^{\circ}C$ and 113.43$^{\circ}C$, respectively. The T$_{g}$ also increases with increased aging time. Measurements performed by TGA(thermogravimetric analysis) have showed that weight loss profile of sound specimens are lower than those aged.ged.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.2
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• pp.59-65
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• 2003

Electrical properties such as permittivity and tan$\delta$ of unaged (control) and aged (72 h at 18$0^{\circ}C$) mica/epoxy composites of 130 ${\mu}{\textrm}{m}$ thickness were measured and their surface conditions were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), electron spectroscopy for chemical analysis (ESCA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Both permittivity and tan6 of control specimens were higher than those of short-time aged specimens. FTIR results show a new peak at 1710 $cm^{-1}$ / for short-time aged specimens, originating from carbonyl group formed by the oxidation reaction during the aging process. ESCA results show that the binding energy at 532.9 eV representing the singlet state of oxygen ( $O_{1s}$) decreases by 13.7%, whereas that at 534.6 eV increases by 13.7%. Glass transition temperatures of control and short-time aged specimens are observed to be 95.4$^{\circ}C$ and 113.4$^{\circ}C$, which increase with the increase of aging time. TGA results indicate that the control specimens contain a smaller amount of volatile components than the short-time aged specimens.s.

• Electrical & Electronic Materials
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• v.10 no.4
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• pp.327-333
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• 1997

Experiments on mechanical fatigue were conducted using the specimens which were cut from hydrogen cooled generator(rated 22kV and 50OMW) stator windings. We have investigated the aged mechanism of mica/epoxy insulation systems under air or hydrogen by both the tensile and compressive loadings. The fracture of generator stator windings is generally affected by mechanical stress. Thus, the tensile strength test were conducted. In this case, the maximum strength and strain are quite different between sound and aged specimens. It is observed that low bonded interface parts of tapes generally have lower strength than those of normal tapes which causes stress. In order to estimate the effects of cyclic load by the electromagnetic forces while the generator starts/stops, the mechanical fatigue test was also conducted. It is confirmed that the equation of expected life depends on stress amplitude and number of cycles. Though the stress amplitude and number of cycles are very tiny, the tensile fatigue of aged specimens under hydrogen atmosphere is bigger than those under air. In the case of hydrogen atmosphere, the tensile stress gives bigger effect than the compressive one.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.123-130
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• 2009

The partial discharge (PD) measurement is a very effective method to assess the winding insulation condition of high-voltage machines, since most of the insulation failure processes are directly or indirectly caused by PD. On-line PD measurements, which can detect insulation defects of winding in the early stages on rotating machines in operation, have been accepted as the most important technique. The epoxy mica capacitive coupler is currently and extensively used for on-line detection of PD pulses of high-voltage rotating machines. To evaluate the feasibility of developing a capacitive coupler that is easier to manufacture at a lower cost compared to epoxy mica couplers, a 100pF capacitive coupler made of ceramic material is designed, fabricated and tested for on-line PD measurements of 23 kV electrical machines. A series of electrical tests and accelerated aging tests are performed on the ceramic coupler to evaluate the performance requirements, long-term reliability and thermal stability for in field application. The test results show that the newly developed ceramic coupler provides equal and improved performance at a lower cost compared to epoxy mica couplers, and estimated voltage life is anticipated to surpass 100 years.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1229-1234
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• 2008

In this work, ultra high-voltage (17 - 50 kV AC), reliable 80 pF mica capacitors for partial discharge system application were investigated. Mica was used as the dielectric of the capacitors. Using the conservative design rule, over 3 individual $50\;{\mu}m$ thick mica sheets with a size of 30mm{\times}35mm were used with lead foils to form a parallel capacitor element and 20 mica sheets were interleaved with lead foils to form a series stack of parallel capacitor element to meet the requirements of the capacitors. The dimensions of the fabricated 80 pF capacitors for 17 kV AC and 50 kV AC were $90\;mm{\times}90\;mm$ and $95\;mm{\times}180\;mm$, respectively. The high-frequency characteristics of the capacitance (C) and dissipation factor (D) of the developed capacitors were measured using a capacitance meter. The developed capacitors exhibited C of 79.5 - 87.5 pF, had D of 0.001% over the frequency ranges of 150 kHz to 50 MHz, had a self-resonant frequency of 65 MHz, and showed results comparable to those measured for the capacitors prepared recently by $Adwel^{Tm}$. The developed capacitors also showed excellent characteristics for thermal shock test and temperature cycling test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.83-89
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• 1991

The partial discharge properties of interface layer in Mica-Epoxy composite, which has been mainly used for the coil insulating material of high voltage machinery, are different from those of resins due to the abnormal interface layer to be presented between inorganic material and resin. Accordingly, the study on discharge of interface in composite insulting system is strongly requsted for not only an increasing of insulating strength, but also the basical information of diagnosis system for high voltage equipment. As a result, it has been confirmed that the interface is an abnormal resin layer and the contact states at interface is depended upon the density of silane aqueous solution. Pulse frequency at abnormal interface shows a linear increasing with enlargement of discharge quantity. Whereas, in case of normal interface, pulse frequency property represents exponential increasing at the point of saturating. A life model can be diagramed from results of time dependance of skewness, and a survival life time can be quantified from the life model suggested.