• 전기의세계
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• v.34 no.8
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• pp.476-488
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• 1985

전기공학분야의 여러다른 부분과 같이 전력케이블 분야에서도 수많은 연구와 아울러 특히 19세기후반에 전력케이블의 제작에 성공한 것은 20세기에 들어와서 케이블과 이에 관련된 모든 기술이 빠른 속도로 발달하게된 주원동력이 되었다고 보아도 과언은 아니다. 비록 19세기 후반에 고무(rubber)를 사용하여 케이블 절연 하였지만, 그이후 약 70여년이상을 Impergnated paper(오일복합수지(oil compound resin)나 오일(oil)을 종이에 스며들게한 후 그 종이를 절연재료로 이용함)를 전력케이블 절연재료로 많이 사용하여 왔다. 아울러 OF cable의 제조기술도 향상되어 현재 매우 높은 전압과 상당한 전력용량를 충족시키는 전력케이블로서 발달을 계속하고 있다. 1960년대에 들어서서 extruded polymer material 이 전력케이블의 절연재료로 쓰이게 되었는데 현저하게 주로 쓰이는 재료로 폴리에틸렌인대, 그대로 순수한 상태로 또는 어떤 처리를 하여 쓰기도 한다. 그러나 EPR(ethylene propylene rubber)도 역시 개발중에 있다. Extruded synthetic insulation을 사용한 케이블은 현재 모든 필요한 전류와 전압을 망라하여 널리 쓰이고 있으며 다른재료를 사용한 케이블 보다 설치하기에 쉽고 사용법이 비교적 간단하고, 또한 전력망(network)에서의 신뢰서이도 높은 것으로 나타나 매우 만족스런 재료로 인정받고 있다.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1746-1748
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• 1998

In this paper, the relation between the increment of metallic content such as copper(Cu) and iron(Fe) according to degradation of pole-transformer oil and change of electrical characteristics according to increment of metallic content was studied. As the result, electrical characteristics was decrease according to increment of metallic content, especially copper content, and the trend of T.C.G(Total Carbonic Gas) agreed with the trend of copper content.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.114-119
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• 2011

Large Power transformer is a complex and critical component of power plant and consists of cellulosic paper, insulation oil, core, coil etc. Insulation materials of transformer and related equipment break down to liberate dissolved gas due to corona, partial discharge, pyrolysis or thermal decomposition. The dissolved gas kinds can be related to the type of electrical faults, and the rate of gas generation can indicate the severity of the fault. The identities of gases being generated are using very useful to decide the condition of transformation status. Therefore dissolved gas analysis is one of the best condition monitoring methods for power transformer. Also, on-line multi-gas analyzer has been developed and installed to monitor the condition of critical transformers. Rogers method, IEC method, key gas method and Duval Triangle method are used to failure diagnosis typically, and those methods are using the ratio or kinds of dissolved gas to evaluate the condition of transformer. This paper analyzes the reliability of transformer diagnostic methods considering actual dissolved gas concentration. Fault diagnosis is performed based on the dissolved gas of five transformers which experienced various fault respectively in the field, and the diagnosis result is compared with the actual off-line fault analysis. In this comparison result, Diagnostic methods using dissolved gas ratio like Rogers method, IEC method are sometimes fall outside the ratio code and no diagnosis but Duval triangle method and Key gas method is correct comparatively.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.604-608
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• 2015

In this paper, we study the characteristics of heat transfer for an insulated multi-core tube using glass wool as an insulator for the multi-core tube. By performing experiments and modeling, we examine the variations in the temperature characteristics of hydraulic oil inside the multi-core tube with atmosphere temperature, inlet temperature, and the flow rate of hydraulic oil for the insulated multi-core tube that we developed. When the minimum inlet flow rate of hydraulic oil employed within the scope of the research is 0.29 l/min, the temperature difference obtained in the experiments and numerical analysis was a maximum of $3^{\circ}C$. For a constant atmospheric temperature, as the inlet temperature of the hydraulic oil increases, the outlet temperature of the hydraulic oil will also increase, regardless of its inlet flow rate. Further, when the inlet flow rate of the hydraulic oil is more than 1.01 l/min, the effect of the atmospheric temperature on the temperature drop of the hydraulic oil is low.

• Transactions on Electrical and Electronic Materials
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• v.13 no.5
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• pp.229-232
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• 2012

DGA is one of the most recent techniques developed to diagnose the fault condition on oil filled insulation transformers. There are more than 6 known different methods of DGA fault interpretation technique and so there is the likelihood that they may vary in their interpretations. A series of combined interpretation methods that can determine the power transformer condition faults in one assessment is therefore needed. This paper presents a computer program- based system developed to combine four DGA assessment techniques; Rogers Ratio Method, IEC Basic Ratio Method, Duval Triangle method and Key Gas Method. An easy to use Graphic User Interface was designed to give a visual display of the four techniques. The result shows that this assessment method can increase the accuracy of DGA methods by up to 20% and the no prediction result had been reduced down to 0%.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.897-899
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• 1999

In this paper, the interfacial dielectric breakdown phenomenon of interface between Epoxy/EPDM (ethylene propylene diene terpolymer) was discussed, which affects stability of insulation system of power delivery devices. Specimen structure was designed by using MAGSOFT's FLUX2D based on the finite elements method. Design concepts is to reduce the effect of charge transport from electrode in the process of breakdown and to have the tangential electrical potential with the Epoxy/EPDM interface. AC interfacial breakdown phenomenon of was investigated by variation of interfacial conditions oil and temperature which are supposed to have influence on the interfacial breakdown strength. Interfacial breakdown strength was improved by spreading oil over interfacial surface. The decreasing ratio of the AC interfacial breakdown strength in non-oiled specimens was increased by the temperature rising and its of oiled specimens was not affected by temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.254-257
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• 1997

In this paper, we investigated the effects of gap length and tip radius influenced in breakdown of mineral based insulation oil Electrode system was needle-plane geometry It is to model conductive extrusions in oil filled electrical power apparatus. The tip radius of needle electrode was 5, 10, 20 and 25${\mu}{\textrm}{m}$, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. It was calculated electrical breakdown strength at tip using Mason\`s equation from breakdown voltage As gap lenght increased. breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by tole phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage. breakdown 7tr7ilgtll was higher wheal polarity of needle was negative than positive. It is because of the space charge effect ill accordance with the influence of liquid motion.

• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.56-59
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• 2004

In this paper, we investigated the influence of gap length and tip radius on breakdown of mineral based insulation oil. Applied voltages were DC and AC voltage. Electrode system was needle-plane structure. The tip radius of needle electrode was 5, 10, 20 and 25${\mu}m$, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. Electric breakdown strength at tip was calculated using Mason's equation contained geometric figure. As gap length increased, breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by the phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage, breakdown strength was higher when polarity of needle was negative than positive. It is because of the space charge effect in accordance with the influence of liquid motion.

• Analytical Science and Technology
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• v.18 no.5
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• pp.410-418
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• 2005

PCBs had numerous uses such as hydraulic fluid, heat exchange fluid, sealant, lubricant, and carbonless copy paper. They are most likely found in electric utilities, power stations, industrial facilities, electronic manufacturing plants, petrochemical plants, railroad systems, electric equipment repair facilities, mining sites (active or abandoned), and military camps. Due to its outstanding chemical and thermal stabilities and electrical insulation properties, the commercial and industrial products of PCBs, such as Aroclors, Kaneclors, Clophens, Phenaclors etc., had been widely used as thermal oil and transformer oil from 1930s until the 1970s. The transformer oils were analyzed as a main source of polychlorinated biphenyls (PCBs) emission into the environment. Qualitative estimation of oil extracts as carried out with Aroclor 1242, 1248, 1254, 1260. The transformer oils contained the pure and mixed of Aroclor 1242, Aroclor 1254, and Aroclor 1260. Also, commercial screening kit of 20 ppm and 50 ppm were applied to the transformer oil samples.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.278-282
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• 2007

In the complex insulation system that is used in extra high voltage(EHV) devices, according to the trend for electric power equipment of high capacity and reduction of its size, macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. In this paper, the dielectric strength decrease of the macro interfaces between epoxy and ethylene propylene diene terpolymer(EPDM) was estimated by using the applied voltage to breakdown time characteristics. Firstly, the AC short time dielectric strength of specimens was measured at room temperature. Then, the breakdown time was measured under the applied constant voltage which is 70% of short time breakdown voltage. With these processes, the life exponent n was determined by inverse power law, and the long time breakdown voltage can be evaluated. The best condition of the interface was LOS(low viscosity(350 cSt) silicone oil spread specimen). When 30 years last on the specimens, the breakdown voltage was estimated 44% of the short time breakdown voltage.