• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.12
• /
• pp.877-882
• /
• 2014

It has been confirmed that the inner defect of transformer and the perfect diagnosis for aging are closely related to safe electric power transmission system and that the detection of accident and diagnosis technique turn out to be very important issues. Since electric power machinery consists of various kinds of components, however, it is very difficult to make a diagnosis for aging by one parameter. Thus, diagnosis for aging is feasible only through the combination of various parameters. Recently, various expert systems have been developed and applied to diagnosis for aging, but they are not yet reliable enough to apply to the real system. In this paper, XLPE which is ultra high voltage cable insulator material were chosen to investigate the influence of void on insulator material using partial discharge. Obtained data have been processed by PRPD (phased resolved partial discharge) distribution function and K-means. And statistical and cluster distribution of partial discharge have been analysed and investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.36 no.6
• /
• pp.570-575
• /
• 2023

Demand and necessity for eco-friendly offshore wind farms have been increasing. Research on submarine cables is constantly being considered for a reliable and stable power transmission. This study aimed to evaluate the thermal aging characteristic of submarine cables inside the J-tube of offshore wind farms. In this study, a submarine cable was set in three sections: The first is the part exposed to the air above the sea level at high temperature. The second is the section exposed to repeated temperature fluctuation as the sea level rises and falls. The third is the part submerged at low temperature below the sea level. Aged samples were tested by using the method of electrical evaluation to obtain insulation characteristics. The experimental results show that the dielectric breakdown of the sample with temperature fluctuation was 7% lower than the sample with a constant temperature; thereby, demonstrating that the section where the temperature fluctuation occurred in the submarine cables was weaker than the other. The sections of submarine cable with temperature fluctuations are believed as a weak point during operation; therefore, this part should be monitored preferentially.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.9
• /
• pp.1518-1523
• /
• 2016

In this study, in order to understand the degradation characteristics of oil-paper insulation for power transformers and OF cables, tan delta was measured using cable model specimens with long-term accelerated thermal and electrical aging. In addition, to find out the degradation level due to the accelerated aging, tensile strengths of aged papers were measured. As a result, tan ${\delta}$ showed the characteristics of slight decrease at the first stage and then increase with the aging time, which could be analyzed due to the evaporation of remaining moisture and the change of aging rate with time. Also, the trend of tensile strengths with aging temperature and time was appeared to be exponentially decreased and by use of these data equivalent calculated lifetimes and accelerated aging factors were derived for each aging temperatures. After then, tan ${\delta}$ was analyzed with the equivalent operating years. For all different aging temperatures, the aged data were very well fit to the equivalent operating years and it is shown that tan ${\delta}$ was increased with the decrease of tensile strength.

• Journal of the Korea Computer Industry Society
• /
• v.4 no.4
• /
• pp.579-588
• /
• 2003

There are many unfavorable conditions that lead to shortening life of cable by causing dielectric breakdown and aging such as field concentrations occurring in intermediate materials linking each cables, penetration of various impurities, and undermining of cable insulation layers. This paper simulated investigated partial discharge properties of XLPE which is widely used for ultra high voltage cable insulation materials and EPDM which is being used as insulation layer of cable joint materials kit, using Boundary Element Method. The result of computer simulation showed that inner-Void defect caused silicone oil to weaken the E-field effect. and we also found that E-field distribution in EPDM remained relatively lower than that in XLPE.

• Steel and Composite Structures
• /
• v.12 no.5
• /
• pp.413-426
• /
• 2012

In this paper, nonlinear static analysis of three-dimensional cable stayed bridges is performed for the time dependent materials properties such as creep, shrinkage and aging of concrete and relaxation of cable. Manavgat Cable-Stayed Bridge is selected as an application. The bridge located in Antalya, Turkey, was constructed with balanced cantilever construction method. Total length of the bridge is 202 m. The bridge consists of one $\ddot{e}$ shape steel tower. The tower is at the middle of the bridge span. The construction stages and 3D finite element model of bridge are modeled with SAP2000. Large displacement occurs in these types of bridges so geometric nonlinearity is taken into consideration in the analysis by using P-Delta plus large displacement criterion. The time dependent material strength and geometric variations are included in the analysis. Two different finite element analyses carried out which are evaluated with and without construction stages and results are compared with each other. As a result of these analyses, variation of internal forces such as bending moment, axial forces and shear forces for bridge tower and displacement and bending moment for bridge deck are given with detailed. It is seen that construction stage analysis has a remarkable effect on the structural behavior of the bridge.

• Proceedings of the KIEE Conference
• /
• 1996.07c
• /
• pp.1825-1827
• /
• 1996

In this study, the Joint of 345kV OF $1C{\times}2000mm^2$ cable was developed to keep up with the trends that need higher-voltage & capacity underground transmission line. The type of joint developed was based on the two kinds of models that have had a good reliability internationally. The mechnic and electric characteristics of the sample specimen was managed in detail when it was manufactured and estimated. Especially, in order to prove the reliability of usage for 30 years, the method of long term aging test was studied. As a result of test, we knew that the joint developed had a good performance. From this study, it can be thought that future ultra-high voltage underground transmission line could be constructed by domestic technology.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.8
• /
• pp.1632-1638
• /
• 2011

Electric cables are one of the most important components in a nuclear power plant since they provide the power needed to operate electrical equipment. Despite their importance, cables typically receive little attention since they are considered passive, long-lived components that have been very reliable over the years when subjected to the environmental conditions for which they were designed. The operating experience reveals that a defect of the insulator or poor construction causes the initial failure of cable. However, the number of cable failures increase with plant aging, and these cable failures are occurring within the plants' 40-year licensed period. These cable failures have resulted in plant transients, shutdown, loss of safety functions or redundancy, entries into limiting conditions for operation, and challenges for plant operators. Therefore, diagnosis of MV cable installed in NPPs has become one of the most urgent issues in recent years. In accordance with PSR, condition maintenance for cables is also continuously required. Recently, HFPD tests have been widely performed to diagnose cable in the transmission and distribution cable system. However, on-line HFPD wasn't used in the NPPs because of the danger of plant shutdown, measurement sensitivity and application problems, etc. In this paper, HFPD measurement with portable device was performed to evaluate the integrity of the 4.16kV & 13.8kV cable lines. The test results show that HFPD is highly attractive to the diagnosis of MV cables in NPP by high detection sensitivity on-site.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.35-40
• /
• 1997

As demand of electric power are growing and transmission line limited owing to enlargement of the downtown area The eonfidence of underground transmission cable which shows gradual growth are high. It is found whether insulating ability is good or not. In this paper, The exper iment result is shown that the fall of insulating ability and take preventive measure through the analysis of tans, water content, dielectric breakdown voltage, total acid number, volume resistivity , and gas in the oil in an accordance with the characteristic change of oil used very much for insulating oil of cable.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.50-50
• /
• 2010

전력케이블의 수명예측은 전력설비의 적절한 전력설비의 신뢰성 확보에 목적이 있다. 그러나 장기간의 수명으로 설계되는 관계로 가속실험을 수행하여 중장기적인 절연성 추세를 평가하기 위해서 와이블 분포함수와 같은 통계적인 접근과 수영과 관련된 보상조건에 대한 고려가 필수적이다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.05c
• /
• pp.148-151
• /
• 2002

In order to prevent the failures of underground distribution power cables we need to measure insulation condition in the field. Until now we used DC high voltage as a power source for the cable diagnosis but it was not proper method to the XLPE insulation cables because DC high voltage can affect sound insulation and can't diagnose exactly insulation degradation. For these reasons we imported isothermal relaxation current measurement system called by KDA-1 from germany but it's reliability did not proved in our URD cables. DC voltage decay measurement system was developed by domestic company but they don't have field experience. In this paper we tried to prove reliability of these two systems in the field. Through the field diagnosis and Ac breakdown test the two systems showed similar results.