• Title/Summary/Keyword: Insulation Assessment

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The Assessment on the Insulation Condition of Generator Stator Windings by a Novel Parameter PDI(Partial Discharge Index) (새로운 파라메타인 부분방전 변화지수에 의한 발전기 고정자 권선의 절연상태 평가)

  • Hwang, Don-Ha;Park, Do-Yeong;Kim, Yong-Ju;Kim, Jin-Bong;Ju, Yeong-Ho
    • 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.

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Assessment of Insulation Condition in Operating Large Turbine Generator (운전중인 대형 터빈발전기에서 절연상태 평가)

  • 김희동
    • 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.

Stator Insulation Quality Assessment for High Voltage Motors Based on Probability Distributions

  • Kim, Hee-Dong;Kim, Chung-Hyo
    • Journal of Electrical Engineering and Technology
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    • v.3 no.4
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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.

Correlation of Single-Number Ratings for Sound Insulation by Floor Impact (바닥충격음 차단성능 단일수치 평가방법별 상관성에 대한 조사연구)

  • 김흥식;김명준;김하근
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.719-723
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    • 2002
  • The purpose of this study is to suggest the correlation of single-number ratings for sound insulation by floor impact. As a assessment method of impact sound insulation. we selected the IIC contour of ISO, A weighted sound level. Inverse A-weighting curve and L-Index of japanese industrial standard. And we estimated the single-number ratings by application the measured data of impact sound level to each method. The results showed that the coefficients of determination between each two single-number ratings were very high (more than 0.9169). And In the condition of same assessment method, the coefficient of determination for light-weight impact sound was higher than that for heavy-weight impact sound.

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A Preliminary Assessment on ERVC Performance Depending on Insulation Conditions (단열재 조건에 따른 원자로용기 외벽냉각 성능 예비분석)

  • Dong-Hyeon Choi;Yoon-Suk Chang
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.19 no.1
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    • pp.36-43
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    • 2023
  • Lots of researches have been conducted on in-vessel retention (IVR) to prevent or mitigate severe accident in nuclear power plants. Various methodologies were proposed and the external reactor vessel cooling was selected as a part of promising IVR strategy. In this study, the strategy is strengthened by enhancing the natural circulation performance through the adoption of insulation in the reactor cavity. A thermal analysis was carried out based on an assumed accident scenario and its results were used as boundary conditions for subsequent seven flow analysis cases. By comparing the natural circulation performance, effects of annular gaps and insulation shapes on the mass flow rate and flow velocity were quantified. The improvement in cooling performance can be reflected in actual design via detailed assessment.

Condensation Prevention Performance Assessment Taking Into Account Thermal Insulation Performance Degradation Due to Aging for Apartment Housing

  • Choi, Doo-Sung;Lee, Myung-Eun
    • KIEAE Journal
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    • v.15 no.6
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    • pp.11-18
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    • 2015
  • Purpose: The current study analyzed trends in thermal insulation performance with aging, and condensation characteristics caused by the former. Method: Thermal insulation and condensation prevention performance of an architecture were assessed using Temperature Difference Ration Inside, or TDRi. Subjects of this quantitative analysis in thermal insulation performance change due to aging included recently constructed apartments and aged apartments older than 40 years. Time series comparison and analysis were conducted to observed changes in the thermal insulation performance and condensation characteristics. Result: Analysis showed that wall insulation performance degraded with aging regardless of fortified insulating material usage or insulating material type, which caused increased danger of condensation. In addition, when fortified insulating material was installed on the connection between the walls, insulation performance degradation was lower compared to cases in which fortified materials were not used. In all cases from 1 to 10, the rate of thermal insulation performance degradation increased after 20 years of aging.

Assessment of Insulation Condition in Rotating Machine Stator Windings (회전기 고정자 권선의 절연상태 평가)

  • Kim, Hee-Dong
    • 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.

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Assessment of Insulation Deterioration in Stator Windings of High Voltage Motor (고압전동기 고정자 권선의 절연열화 평가)

  • Kim, Hee-Dong;Kong, Tae-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.5
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    • pp.711-716
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    • 2012
  • To assess the insulation deterioration of stator windings, diagnostic and AC breakdown tests were performed on the eleven high voltage (HV) motors rated at 6kV. After completing the diagnostic tests, the AC overvoltage test was performed by gradually increasing the voltage applied to the stator windings until electrical insulation failure occurred, to obtain the breakdown voltage. Stator winding of motors 1, 3, and 8 failed at above rated voltage at 14 kV, 13.8kV, and 16.4kV, respectively. The breakdown voltage of three motors was higher than expected for good quality windings in 6kV motors. Based on deterioration evaluation criteria, the stator winding insulation of eleven HV motors are confirmed to be in good condition. The turning point of the current, $P_{i2}$, in the AC current vs. voltage characteristics occurred between 5kV and 6kV, and the breakdown voltage was low between 13.8kV and 16.4kV. There was a strong correlation between the breakdown voltage and various electrical characteristics in diagnostic tests including Pi2.

Examination of the Optimal Insulation Thickness of Exterior Walls for Climate Change (기후변화를 고려한 외벽 최적단열두께 검토)

  • Jung, Jae-Hoon
    • KIEAE Journal
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    • v.11 no.6
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    • pp.81-86
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    • 2011
  • By strengthening the insulation performance of a building, a great deal of energy can be saved and a comfortable indoor environment can be offered to people. On the other hand, the climate, which has a great influence on the indoor environment, is changed by global warming. Therefore, in planning building envelope structure and design, climate change should be considered. In this paper, the optimal insulation thickness of exterior walls was calculated by an economic assessment method using heating degree-days. Additionally, how much influence climate change has on planning building insulation was investigated. The examination showed that heating degree-days have decreased by about 10% due to climate change in the past few decades. It was also shown that the optimal insulation thickness of exterior walls was thin, at about 6%, in three representative Korean cities (Seoul, Daejeon, Jeju).

Assessment of Risk Factors for Application of Exterior Insulation Board in Cast-in-place Concrete Form System for Apartment (공동주택용 외단열 동시타설 공법 적용을 위한 리스크 요인 평가)

  • Cui, Jun-Long;Kim, Taehoon;Lim, Hyunsu;Cho, Hunhee;Kang, Kyung-In
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2015.05a
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    • pp.204-205
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    • 2015
  • Exterior insulation board in cast-in-place concrete form system could reduce construction period and improve quality in apartment construction. However, the method is progressed with insulation and concrete frame works at the same time, then risk is increased in duration control and quality management. Therefore, this paper analyzed risk factors through FMEA method. We found that the key risk factors delaying schedule was insulation material that soaked in the rain and quality defects on the insulation material joint. Based on this research, the risk management approach should be developed for improvement of method activation.

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