• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.221-223
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• 1991

In order to evaluate degradation of the aged power cables, thin slices(200m) cut from the aged cables were prepared for thermally stimulated current measurements. Throughout the temperature range, 140 to $280^{\circ}C$ the TSC is greater for the aged material, and sharp peak is observed at $158^{\circ}C$ and $210^{\circ}C$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.677-682
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• 2000

본 연구는 전동기의 부분방전에 의해 발생되는 전자파를 측정하여 전동기의 열화상태를 진단할 수 있는 진동기 절연열화 진단시스템을 설계하였다. 청장 전동기에서 부분방전에 의한 전자파를 on-line으로 측정하고, 측정된 데이터로부터 정량화된 특징 데이터를 추출한 후 전자파의 평균 에너지 분포를 이용하여 전동기의 절연열화 상태를 판단하는 방법을 제시하였으며, 현장에서 사용 중인 Megger시험과 비교하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.114-120
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• 2008

XLPE cable is using insulator for Cross Linked Polyethylene(XLPE), because insulation Performance is superior and easy comparatively. Need systematization of accident transaction for electrical equipment accident, It is no disposal standard for defect of manufacture and second to accidents. in this paper deals with the change of XLPE cable insulation. To understand the electrical properties of XLPE insulation. Made of XLPE block sample, Penetration fracture Sample and flashover sample. Ogura needles having tip radius of $10[{\mu}m]$ were inserted into each sample. AC voltage of 1[kV/sec] increased at 60[Hz] were apple to breakdown sample and flashover sample. AC voltages of 12[kV], 17[kV] at 60[Hz] were a lied to XLPE block sample. The electrical properties of specimens were measured were measured from initiation of tree and breakdown to their characteristics were analyzed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.5
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• pp.213-221
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• 2002

In order to improve the reliability of XLPE cables, it is necessary to find the useful diagnostic parameter according to long term aging. This paper described the change of partial discharge(PD) phase Properties of XLPE cable insulation with branch type electrical tree degradation. for long term aging. To understand the PD Properties with $\phi$ -q-n distributed shape of XLPE insulation, specimens were prepared by 22.9㎸ distribution cable and made in a type of block(16${\times}$16${\times}$3[mm]). Ogura needles having tip radius of l0${\mu}{\textrm}{m}$ were inserted into each block pieces. The measuring system was consisted of PD detector, digitizer for digital conversion, VXI system for signal processing. The PD properties of the specimens were measured from initiation of tree to breakdown and their characteristics were analyzed. We analyzed the relationship between electrical properties(PD Quantity, PD initiation angle, PD extinction angle, PD occurrence angle : (PD extinction angle - PD initiation angle)) and the normalized aging rate. We found PD parameter, PD initiation angle and occurrence angle, which are a useful diagnostic parameter in estimating the branch type electrical tree for XLPE insulation condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.3
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• pp.107-115
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• 1998

This paper deals with the study on injection with EPDM(Ethylene propylene dien ter polymer) the gap which narrow, long, and tubular between an ablative composite tube and a steel motor case. Small size motor assembly was designed and manufactured for man-portable air defense propulsion system. Motor assembly is consisted with steel tube, ablative composite tube and insulation rubber. Ablative composite tube was made of carbon/phenolic prepreg by rolling process and insulation rubber was made of EPDM by TPM(Trans-power molding) process. To select the insulation rubber material, we tested ablative insulation property and degradation property at first and we tested fluidity, adhesive property and hardness of EPDM rubber. Finally we designed TPM process to manufacture motor case assembly and the motor case assembly was examined by non-destructive test(X-ray).

• KEPCO Journal on Electric Power and Energy
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• v.3 no.1
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• pp.23-28
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• 2017

The life management technology becomes important as the failure risk of the aged power transformers increases. Asset management technology, therefore, has been developed to evaluate the remaining life and build replacement strategies of power transformers, which enables an optimal investment decisions based on reliability and economic feasibility. The remaining life assessment technology uses data related to such as installation, operation, maintenance, refurbishment, and disposed history of power transformers. The optimal investment decision additionally uses data related to failure and social costs. To develop the asset management technology in power transformers, it is important to find deterioration parameters directly indicating degradation of power transformers. In this study, 110,000 DGA data during the past 35 years have been analyzed in order to find the deterioration parameters related to the degradation of power transformers. The alarm rates of combustible gases ($H_2$, $C_2H_2$, $C_2H_4$, $CH_4$, $C_2H_6$), TCG CO, and $CO_2$ were analyzed as deterioration parameters. The origin of the gas was discussed in connection with discharge, overheating and insulation aging.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.910-912
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• 1998

In this paper, we purpose automatic diagnosis in online, as the fundamental study to diagnose the partial discharge mechanism and to predict the lifetime, by introduction a neural network. In the proposed method, Ire use acoustic emission sensing system and calculate a fixed quantity statistic operator by pulse number and amplitude. Using statically operators such as the center of gravity(G) and the gradient of the discharge distribute(C), we analyzed the early stage and the middle stage. the fixed quantity statistic operators are learned by a neural network. The diagnosis of insulation degradation and a lifetime prediction by the early stage time are achieved. On the basis of revealed excellent diagnosis ability through the neural network learning for the patterns during degradation, it was proved that the neural network is appropriate for degradation diagnosis and lifetime prediction in partial discharge.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.43-46
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• 2001

Polymers are widely used as insulating materials at various part of power industry. However, electrical properties of these polymers are easily degraded with their working environments, especially radiation areas. In this research, radiation degradation of low density polyethylene (LDPE) used as cable insulation was evaluated with thermoluminescence characteristics. LDPE was irradiated with gamma ray up to 1000 kGy at a dose rate of 5 kGy/hr in the presence of air at room temperature. Each of the irradiated samples were carried out thermoluminescence analysis as a function of temperature. Interrelationships between thermoluminescence and dielectric characteristics and volume resistivity are investigated as well. The results of thermoluminescence analysis showed that those would be significant factors for evaluation of radiation degradation.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.325-330
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• 2004

Several kinds of low voltage cables have been used in nuclear power plants for the supply of electric power, supervision, and the propagation of control signals. These low voltage tables must be inspected for safe and stable operation of nuclear power plants. In particular, the degradation diagnosis to estimate the integrity of low voltage rabies has recently been emphasized according to the long use of nuclear power plants. In order to evaluate their degradation, the surrounding temperature, hardness of insulation material, elongation at breaking point (EAB), etc. have been used. However, the measurement of temperature or hardness is not useful because of the absence of quantitative criteria; the inspection of a sample requires turning off of the power plant power; and, the electrical inspection method is not sufficiently sensitive from the initial through the middle stage of degradation. In this research, based on the theory that the ultrasonic velocity changes with relation to the degradation of the material, we measured the ultrasonic velocity as low voltage cables were degraded. To this end, an ultrasonic degradation diagnosis device was developed and used to measure the ultrasonic velocity with the clothing on the cable, and it was confirmed that the ultrasonic velocity changes according to the degradation of low voltage cables. The low voltage cables used in nuclear power plants were degraded at an accelerated rate, and EAB was measured in a tensile test conducted after the measurement of ultrasonic velocity. With the increasing degradation degree, the ultrasonic velocity decreased, whose potential as a useful parameter for the quantitative degradation evaluation was thus confirmed.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1299-1303
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• 1995

The detection and measurement of partial discharge activity prevalent in the solid insulating systems of high-voltage generator stator windings has, for many years, been a recognized method of assessing the insulation condition of such systems. Partial discharge activity occurs at sites of degradation within, or at the surface of, stator's insulation systems under high voltage stressing. However, partial discharge pulses suffer from attenuation and distortion when transmitted along windings, because of the complex L-C network between windings. The mode of transmission varies with the signal frequency and is dependant on the geometrical configurations of windings. This paper reports the investigated results of the signal propagation characteristics along the windings when both sinusoidal signals and simulated partial discharge pulses are injected at the various positions of stator windings within the 25 MVA, 11 kV hydro generator. The on-line identification technique of partial discharge location in generator windings is also proposed in this study.