• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 C
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• pp.1496-1498
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• 1999

The line charging is becoming larger due to the expansion of underground cable and extra high voltage lines. It causes reactive power surplus at light load condition which may force generators to operate reluctantly in the under excited mode. This paper proposes the pratical criteria and methodolgy for the shunt reactor planning while suppressing generator's under excited operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1620-1622
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• 1998

The failure occurs in the system of the underground transmission line, the time of restoration is very long, the damage from stopping power supply is very serious and the cost of restoration is very great. because of these problems, the system and equipment must be protected from every electrical failure by installing protection unit. This study is summarized and compared the effects of configuration method of cable protection device with respect to surges in EHV (Extra High Voltage) underground transmission system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1422-1423
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• 2007

This study deals with various neural network algorithms for the on-site partial discharge pattern recognition. For the purpose, the pattern recognition has been carried out on partial discharge data for the typical artificial defect using 9 different neural network models. In order to enhance on-site applicability, artificial defects were installed in the insulation joint box of extra-high voltage xLPE cables and partial discharges were measured by use of the metal foil sensor and a HFCT as a sensor. As the result, it is found out that the accuracy of pattern recognition could be enhanced through the application of the Sigmoid function, the Momentum algorithm and the Genetic algorism on the artificial neural networks. Although Multilayer Perceptron (MLP) algorism showed the best result among 9 neural network algorisms, it is thought that more researches on others would be needed in consideration of on-site application.

• Transactions on Electrical and Electronic Materials
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• 제14권4호
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• pp.211-215
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• 2013

Partial discharge diagnosis techniques using ultra high frequencies do not affect load movement, because there is no interruption of power. Consequently, these techniques are popular among the prevention diagnosis methods. For the first time, this measurement technique has been applied to the GIS, and has been tested by applying an extra high voltage switchboard. This particular technique makes it easy to measure in the live state, and is not affected by the noise generated by analyzing the causes of faults ? thereby making risk analysis possible. It is reported that the analysis data and the evaluation of the risk level are improved, especially for poor location, and that the measurement of Ultra high frequency (UHF) partial discharge of the real live wire in industrial switchgear is spectacular. Partial discharge diagnosis techniques by using the Ultra High Frequency sensor have been recently highlighted, and it is verified by applying them to the GIS. This has become one of the new and various power equipment techniques. Diagnosis using a UHF sensor is easy to measure, and waveform analysis is already standardized, due to numerous past case experiments. This technique is currently active in research and development, and commercialization is becoming a reality. Another aspect of this technique is that it can determine the occurrences and types of partial discharge, by the application diagnosis for live wire of ultra high voltage switchgear. Measured data by using the UHF partial discharge techniques for ultra high voltage switchgear was obtained from 200 places in Gumi, Yeosu, Taiwan and China's semiconductor plants, and also the partial discharge signals at 15 other places were found. It was confirmed that the partial discharge signal was destroyed by improving the work of junction bolt tightening check, and the cable head reinforcement insulation at 8 places with a possibility for preventing the interruption of service. Also, it was confirmed that the UHF partial discharge measurement techniques are also a prevention diagnosis method in actual industrial sites. The measured field data and the usage of the research for risk assessment techniques of the live wire status of power equipment make a valuable database for future improvements.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.42-47
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• 2010

Polymer insulating materials such as cross linked polyethylene (XLPE) are employed in electric cables used for extra high voltage. These materials can degrade due to chemical, mechanical and electric stress, possibly caused by voids, the presence of extrinsic materials and protrusions. Therefore, this study measured discharge patterns, discharge phase angle, quantity and occurrence frequency as well as changes in XLPE under different temperatures and applied voltages. To quantitatively analyze the irregular partial discharge patterns measured, the discharge patterns were examined using a statistical program. A three layer sample was fabricated, wherein the upper and lower layers were composed of non-void XLPE, while the middle layer was composed of an air void and copper particles. After heating to room temperature and $50^{\circ}C$ and $80^{\circ}C$ in silicone oil, partial discharge characteristics were studied by increasing the voltage from the inception voltage to the breakdown voltage. Partial discharge statistical analysis showed that when the K-means clustering was carried out at 9 kV to determine the void discharge characteristics, the amount discharged at low temperatures was small but when the temperature was increased to $80^{\circ}C$, the discharge amount increased to be 5.7 times more than that at room temperature because electric charge injection became easier. An analysis of the kurtosis and the skewness confirmed that positive and negative polarity had counterclockwise and clockwise clustering distribution, respectively. When 5 kV was applied to copper particles, the K-means was conducted as the temperature changed from $50^{\circ}C$ to $80^{\circ}C$. The amount of charge at a positive polarity increased 20.3% and the amount of charge at a negative polarity increased 54.9%. The clustering distribution of a positive polarity and negative polarity showed a straight line in the kurtosis and skewness analyses.

• 한국산학기술학회논문지
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• 제11권1호
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• pp.314-319
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• 2010

본 논문은 초고압 전력케이블의 접속재 개발을 위한 연구결과로써, 접속시스템의 핵심기술인 고절연 고무슬리브의 현장 접속 작업의 용이성을 위한 Carrier Pipe의 구조해석과 주요부의 전기적 특성과 전계의 집중을 완화하기 위한 수치해석 등을 실시하여 구조적 안정성을 평가하려 한다. 절연설계 및 전계완화 해석에 의한 검증과 접속재의 수축거동 해석에 의한 Carrier Pipe의 최적화된 형상으로 두께가 최소 9mm이상을 갖는 Carrier Pipe가 필요하며, 전기적 전계완화 해석결과 고절연 고무슬리브의 중앙매립전극 경계면으로써, 접속재 수축거동 해석 결과와도 일치함을 검증할 수 있었다.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.603-608
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• 2023

Carbon black with high purity and excellent conductivity is used as a conductive filler in the semiconductive compound for EHV (Extra High Voltage) power cables of 345 kV or higher. When carbon black and CNT (carbon nanotube) are applied together as a conductive filler of a semiconductive compound, stable electrical properties of the semiconductive compound can be maintained even though the amount of conductive filler is significantly reduced. In EHV power cables, since the semi-conductive layer is close to the conductor, stable electrical characteristics are required even under high-temperature conditions caused by heat generated from the conductor. In this study, the theoretical principle that a semiconductive compound applied with carbon black and CNT can maintain excellent electrical properties even under high-temperature conditions was studied. Basically, the conductive fillers dispersed in the matrix form an electrical network. The base polymer and the matrix of the composite, expands by heat under high temperature conditions. Because of this, the electrical network connected by the conductive fillers is weakened. In particular, since the conductive filler has high thermal conductivity, the semiconductive compound causes more thermal expansion. Therefore, the effect of CNT as a conductive filler on the thermal conductivity, thermal expansion coefficient, and volume resistivity of the semiconductive compound was studied. From this result, thermal expansion and composition of the electrical network under high temperature conditions are explained.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2009년도 춘계학술발표논문집
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• pp.532-535
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• 2009

본 논문은 초고압 전력케이블의 접속재 개발을 위한 연구결과로써, 접속시스템의 핵심기술인 고절연 고무슬리브 및 현장에서 접속 작업의 용이성을 위한 Carrier Pipe의 구조해석과 전기적 절연설계에 의한 주요부의 전기적 특성과 전계의 집중을 완화하기 위해 Simulation Tool을 이용한 수치해석 등을 실시하여 최적화된 제품을 제작하였다. 절연설계 및 전계완화 해석에서는 고절연 고무슬리브 구조에서 전계가 집중될 수 있는 중요 포인트를 벡터로 선정하였고 이를 기초로 전계해석을 진행하여 선정된 포인트들에서 전계가 집중됨을 검증하였다. 접속재의 수축거동 해석에 의하면, Carrier Pipe의 구조적 안전성을 확보하기 위하여 고절연 고무슬리브로부터의 압력을 구하여 계산한 결과 최소한 9mm이상의 Carrier Pipe 두께가 필요한 것으로 파악 되었다. 이것은 충분한 강도뿐만 아니라 Carrier Pipe의 변형발생으로 인한 현장에서의 설치문제까지 고려하게 된 값이다. 고절연 고무슬리브 제품설계 에서는 고절연 고무슬리브의 특성조건을 설정하였고 고절연 고무슬리브 제품 및 Carrier Pipe의 Interface 설계 기준을 파악하기 위하여 기존의 고절연 고무슬리브를 활용하여 Carrier Pipe와의 장착 Test를 진행하였다. 그 결과, 확장비율 110%로 적용하였을 경우는 30시간 후에는 완전 붕괴가 되었고, 붕괴가 시작되는 지점이 고절연 고무슬리브의 중앙매립전극 경계면으로써, Simulation Tool을 활용한 접속재 수축 거동 해석 결과와도 일치함을 검증 할 수 있었다.