• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.11
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• pp.735-741
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• 1999

The monitoring and assessment on the insulation condition of generator stator windings have been an important task of utility companies. The interest for the assessment of insulation condition has been increasing due to the need to keep old generating equipment reliable in order to extend the equipment life and to increase the generating capacity. Even though many developments and research activities for the condition assessment of generator insulation have been performed for decades, the assessment criterion in order to consistently predict the actual insulation condition is still in question. In this paper, the correlation between the parameters and the insulation condition is analyzed through the various non-destructive diagnostic tests in order to establish the assessment criterion on insulation deterioration of generator stator windings. By analyzing the correlation, PDI(Partial Discharge Index) as a novel parameter for the assessment criterion on insulation diagnosis of stator winding is proposed and verified.

• Fashion & Textile Research Journal
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• v.14 no.4
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• pp.660-668
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• 2012

The purpose of this study is to analyze the thermal characteristics of garments marketed for Korean males and to investigate the influence of each garment on ensemble, by measuring their insulation values(clo) using thermal manikins. The results are as follows. The total insulations(clo) of ensembles for S/S seasons are between 1.46 and 2.6 clo, with the mean of 2.12 clo. The insulation in the still air condition is 1.23 clo, which means a decrease of 42% compared to the total insulation of all the component garments. The insulation of ensembles for S/S seasons in the dynamic air condition decreased by 46.8%, compared to the still air condition. The total insulation(clo) of ensembles for F/W seasons is between 3.84 and 7.36 clo with the mean of 4.74 clo. The insulation in the still air condition is 2.26 clo, which means a decrease of 53.6% compared to the total insulation of all the component garments. The insulation of ensembles for F/W seasons in the dynamic air condition decreased by 36.2%, compared to the still air condition. As the clo value of each component garment gets higher, the insulation of ensembles gets higher. Especially, the insulation of ensembles was more influenced by outer wear than inner wear. The insulation of ensembles could be predicted by the insulation of outerwear better.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1706-1708
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• 2001

Nondestructive tests are used to evaluate the insulation condition of stator windings in rotating machine. These tests included ac current, tan delta and maximum partial discharge. The insulation condition of stator windings was assessed by three test items. The stator windings were generally in good condition, wash, reimpregnation and rewind. It was confirmed that nondestructive tests were most useful method to indicate the insulation condition of stator windings.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.6
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• pp.324-329
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• 2004

Six stator slot couplers(SSC) and a flux probe sensor installed on the stator winding slots of large turbine generator. Assessment of insulation condition has been based upon the measurements of partial discharge(PD) of stator windings and shorted-turn of rotor windings in operating large turbine generator. The maximum PD magnitude(Qm), normalized quantify number(NQN), PD pattern and shorted-turn were measured using on-line insulation condition monitoring system. The NQN and Qm of slot PD side in the phase A are indicated the highest value in six SSC sensors. Monitoring system results showed that discharge at conductor surface and internal discharge were detected at the surface of stator winding and in voids of the groundwall insulation. Insulation of stator and rotor windings in large turbine generator was judged to be in good condition.

• The Korean Journal of Community Living Science
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• v.25 no.4
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• pp.549-556
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• 2014

This study evaluates the thermal insulation and evaporative resistance of a waterproof and breathable garment system and determines the factors influencing its thermal performance. The experimental garments were composed of underwear (shirts with 100% wool and 100% polyester) and outerwear (jackets and pants with a vapor-permeable membrane and a vapor-impermeable membrane). Data on clothing insulation in a dry condition ($10^{\circ}C$) and a wet condition ($10^{\circ}C$, 40% R.H.), evaporative resistance ($34^{\circ}C$, 40% R.H., and $10^{\circ}C$, 40% R.H.), and microclimate vapor pressure were collected and analyzed. According to the results, the thermal insulation of the experimental garment system ranged 1.27~1.40 in the dry condition and 0.40~0.89 in the wet condition at $10^{\circ}C$. Evaporative resistance ranged $41{\sim}525m^2Pa/W$. A decrease in thermal insulation by wetting underwear ranged 31~67% in the cold condition ($10^{\circ}C$). The breathability of the outer garment influenced the decrease in thermal insulation by wetting. The type of underwear fiber influenced the decrease in thermal insulation only when it was used with breathable outerwear. The vapor-permeable outerwear sample with polyester underwear (P_Perm) showed a larger decrease in insulation than that with wool (W_Perm). The evaporative resistance of the vapor-permeable ensemble showed no effect of underwear in the warm condition ($34^{\circ}C$), but polyester underwear showed lower evaporative resistance than wool in the cold condition ($10^{\circ}C$). The vapor-impermeable ensemble showed no difference in evaporative resistance between polyester underwear and wool underwear in both conditions. Future research should consider various clothing ensemble combinations and environmental conditions and evaluate wear comfort by using human subjects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1390-1397
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• 2004

This study is concerned with the thermal analysis during the cool-down period of 135,000㎥ class GT-96 membrane type LNG carrier under IMO and USCG design condition. During the cool-down period, the spraying rate for the NG cooling decreases as the temperature of NG falls down from -4$0^{\circ}C$ to -l3$0^{\circ}C$, and the spraying rate for the cooling of the insulation wall increases as the temperature gradient of the insulation wall is large. It was confirmed that there existed the largest temperature decrease at the first barrier and the first insulation, which are among the insulation wall, especially in the top side of the insulation wall under IMO and USCG design condition. Also, as the NG temperature distribution is fixed, the outer temperature condition under the design condition has influence on the temperature variation at the insulation. By the 3-D numerical calculation about the cargo tank and the cofferdam during the cool-down period, the temperature variation in hulls and insulations is precisely predicted under IMO and USCG design condition. From the comparison between two conditions; IMO design condition shows more severe temperature gradient than USCG design condition, therefore, it provides the conservative estimation of the BOG.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.499-502
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• 2004

In order to detect of insulation problems an early, transformer has to be performed the several tests. The ac current and tan6 of transformer winding insulation were investigated by Schering bridge. Partial discharge(PD) tests are used to evaluate the insulation condition of transformer. The moisture content measurement was conducted using RVM(recovery voltage meter). The RVM test can show that the problem is affecting the paper insulation of transformer. The value of moisture content was 2.3% in main transformer. The insulations of four transformers were judged to be in good condition.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2072-2074
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• 2005

This test was performed to assess the insulation condition of the stator winding of 3.45kV hydro generator in insulation deterioration condition which was due to long service period(30years) since installed We extracted 12 stator wingdings from the hydro generator core, cut the stator windings into three parts(Middle winding part, slot winding part, end wingding part), and evaluated the insulation condition to know the deterioration condition of each parts. This insulation diagnostic tests include AC current, dissipation factor, and partial discharg test.

• Transactions on Electrical and Electronic Materials
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• v.15 no.1
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• pp.7-11
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• 2014

The Polarization and Depolarization Current (PDC) measurement is an efficient and effective diagnostic technique based on time domain measurement, for evaluating the high voltage insulation condition. This paper presents a review and comparison results from several published papers on the application of the PDC method to finding the conductivity and moisture content of various types of insulators. For solid insulation, the study was focused on cable insulation, electric machine stator insulation, and paper insulator in transformer insulation with different conditions. For liquid insulation, the review and comparison was done on biodegradable and mineral transformer oils, with fresh oil condition, and aged condition. The results from previous researchers tests were complied, analyzed and discussed, to evaluate the application of the PDC method to monitor the conductivity and moisture of HV equipment insulation systems. From the review results, the PDC technique successfully gives an indication of the conductivity and moisture level of high voltage insulation.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.595-601
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• 2016

The insulation performance of the insulation currently used in building structures is reflected only during design based on initial performance and the reduction in heat insulation performance due to the degradation of long-term durability is not reflected. This study reviewed the degradation of heat insulation performance due to the durability degradation of insulating materials through the accelerated durability test. The study findings showed that the foamed polystyrene insulation bead method did not show performance degradation due to aging in the standard environmental condition and laboratory accelerated test condition but the performance is degraded in the freeze-thaw test condition. On the other hand, in the case of the extrusion method, the degradation of the heat insulation performance was less in the freeze-thaw test condition, but the rapid performance degradation was caused by the release of the internal gas at the beginning of aging. In addition, the hard polyurethane foam insulation showed better initial insulation performance than other insulation materials, but the performance was found to be degraded somewhat under laboratory accelerated test conditions and freeze-thaw test conditions.