• Journal of the Korean Society of Safety
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• v.25 no.3
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• pp.78-82
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• 2010

This study is to test insulation mortar mixed with wastepaper and sawdust to find out its insulation performance. Therefore, wastepaper and sawdust have been added to normal mortar. They are analyzed for the above purpose using compressive strength and insulation performance. It is found that the more wastepaper and sawdust will be mixed, the lower heat conductivity will be taken. Wastepaper and sawdust mixture will be more 2.0% then the insulation mortar quality can be compatible with the 3rd kind of the standard. Optimal mixture for insulation will be wast paper:sawdust=4:6. Cohesive test of materials showed that test material has stronger than stand are $0.10N/mm^2$. It is satisfactory the test result showed a range of $0.12{\sim}0.15N/mm^2$ from the test result. Optimal mixture of wastepaper and sawdust have been found out from the study comprehensively, exclusive of the proportion of wastepaper:sawdust = 8:2. It is thought that standard of length deformation; 0.5% is reasonable. This means that deformation of mortar itself can be considered. But it is also Shown that water mixture has also been sharply changed at first flow test. Therefore, it is thought that absorbed water content in the material gave considerable effect to variation rate.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.487-492
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• 2006

Inverter driven induction motors with high speed switching and advanced PWM techniques are widely used for variable speed applications. Recently, the insulation failures of stator winding have attracted much concern due to high dv/dt of IGBT PWM inverter output. In this paper, the detailed insulation test results of 26 low-voltage induction motors are presented. Six different types of insulation techniques are applied to 26 motors. The insulation characteristics are analyzed with partial discharge, inception voltage, AC current, and dissipation factor tests. Also, breakdown tests by high voltage pulses are performed. From the above test data the effects due to different wires and insulation techniques on the insulation characteristics of low-voltage induction motors are compared and analyzed. The insulation technique to enhance the insulation strength is suggested from the test results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.141-149
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• 2007

This paper introduce to improve the reliability of the expected service life and the insulation condition evaluation of the high voltage induction motors by assessing, comparing and analyzing the correlation between the dielectric properties of the off-line insulation diagnostic test and dielectric strength on the insulation breakdown test. The insulation diagnostic tests include insulation resistance, polarization index(P.I.), dissipation factor($tan{\delta}$), maximum partial discharges($Q_{max}$) and AC breakdown test. This study evaluated the correlation between insulation diagnostic test and AC breakdown test for stator winding of high voltage induction motor. On the basis of these test results, we expect that this study can be used for effectively assessing the results of insulation diagnostic tests for similar class induction motors in service at industrial field.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.286-291
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• 1991

Most of the failures of rotating machine are stator coil insulation failures. The insulation diagnostic testing for high voltage motors and generators are only megger test and P. I Test which is applied DC voltage until now. But it was impossible to judge insulation deterioration status of high voltage rotating machinery by above testing. In other words, even though the megger measurement values are fairly high, they used to be failed from time to time. Therefore in order to excute reliable and detailed diagnosis of insulation deterioration for rotating machinery, the tangent delta test, the alternating current test and the partial discharge test shall be applied to the insulation diagnostic testing on site.

• Journal of KSNVE
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• v.9 no.6
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• pp.1180-1186
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• 1999

The aim of this study is to investigate the sound insulation performance of windows according to the sound source in the field test. For this purpose, an experiment was performed by KSF 2235(method for field measurements of sound insulation of windows and doors). Based on this code, the sound insulation performance fo the windows was measured for different incident angles of the sound and the effect of incident angle was obtained and discussed. Finally, it was found that the sound insulation performance of the windows was affected by the incident angle of sound source, and the sound insulation rating scale was different for the same window. The main factor changing insulation rating scale is considered to be the sound transmission through the carck of the folding part between the two pieces of wndows. Therefore, when evaluating the sound insulation performance of the windows for the field test, first of all the place of the sound source should be identified and generalized.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.631-635
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• 2007

Diagnostic, surge and ac breakdown tests are widely used to evaluate the insulation condition of stator winding in traction motor. Diagnostic test included ac current, tan delta and maximum partial discharge. The result of diagnostic test indicates that five kinds of stator windings are good condition. Surge test was peformed to confirm the healthy of turn insulation in stator windings. This test is very easy to detect the turn insulation failure between normal and defect stator windings. After completing the diagnostic test, ac breakdown test has conducted gradually increasing ac voltage, until the stator winding punctured. No. 5 stator windings failed near rated voltage of 18.9 kV The breakdown voltage of No. 1 stator windings was 13.0 kV The ac breakdown voltage of normal winding is about 1.45 times higher than that of defect windings. The failure was located in a line-end coil at the exit from the core slot.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1337-1340
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• 1995

For the purpose of rational design of air insulation, it is need to experiment with similar to real shape test object and conform the characterisics. But basic distances of air insulation of transmission line, tower, etc. can be acquired from flashover characteristic of rod-rod, rod-plane electrodes. In this paper, before field test of 765kV transmission line for determination of distances of phase to ground insulation, we execute lightning, switching impulse test with test electrod(rod-rod, rod-plane) against clearances of air insulation. Each tests use up-down method and consist of 30 times flashover test. Flashover data treatment program and air correction program following IEC 60-1(1987) standard were completely builted.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.1-8
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• 2022

This study analyzed the characteristics of insulation resistance and operating time based on an accelerated degradation test of a low-voltage circuit breaker. The experimental sample used a molded case circuit breaker (MCCB) and an earth leakage circuit breaker (ELCB). After measuring the insulation resistance of the circuit breakers, the leakage current was affected by an external rather than an internal structure. Furthermore, the insulation resistance of the circuit breakers with accelerated degradation was measured using a Megger insulation tester. In the accelerated degradation test, aging times of five, ten, 15, and 20 years were applied according to a temperature derived using the Arrhenius equation. Circuit breakers with an equivalent life of ten, 15, and 20 years had increased insulation resistance compared to those with less degradation time. In particular, the circuit breaker with an equivalent life of ten years had the highest insulation resistance. Component analysis of the circuit breaker manufactured through an accelerated degradation test confirmed that the timing of the increase in insulation resistance and the time of additive loss were the same. Finally, after analyzing the operating time of the circuit breakers with degradation, it was confirmed that the MCCB did not change, but the ELCB breaker failed.

• Safety and Health at Work
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• v.11 no.4
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• pp.405-417
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• 2020

Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years. Methods: Thermal characteristics were investigated by measured the temperature increase of electrical socket outlets classified according to year with variation of the current level. Insulation resistance characteristics was measured according to temperature for an electrical socket outlets by their years of use. Finally, to investigate the thermal and insulation resistance characteristics in relation to outlet aging, this study analyzed electrical socket outlets' conductor surface and content, insulator weight, and thermal deformation temperature. Results: Analysis showed, regarding the thermal characteristics, that electrical socket outlet temperature rose when the current value increased. Moreover, the longer the time that had elapsed since an accelerated test and installation, the higher the electrical socket outlet temperature was. With respect to the insulation resistance properties, the accelerated test (30 years) showed that insulation resistance decreased from 110 ℃. In relation to the installation year (30 years), insulation resistance decreased from 70 ℃, which is as much as 40 ℃ lower than the result found by the accelerated test. Regarding the material properties, the longer the elapsed time since installation, the rougher the surface of conductor contact point was, and cracks increased. Conclusion: The 30-year-old electrical socket outlet exceeded the allowable temperature which is 65 ℃ of the electrical contacts at 10 A, and the insulation resistance began to decrease at 70 ℃. It is necessary to manage electrical socket outlets that have been installed for a long time.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1838-1841
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• 2004

This test was performed to assess the correlation between insulation diagnostic tests and breakdown voltage strength of the stator winding of 6.6kV class induction motor in insulation deterioration condition which have been in service for 5 years after being installed in 1998. The insulation diagnostic tests include resistance, polarization index(P.I), dissipation factor(${\triangle}tan{\delta}$), maximum partial discharges(Qmax) and AC breakdown test. we evaluated the correlation between insulation diagnostic test and AC breakdown test for stator winding of high voltage induction motor.