• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권12호
• /
• pp.581-585
• /
• 2006

Macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably in the complex insulation system using in extra high voltage (EHV) electric devices. In this paper, Interface between epoxy and ethylene propylene diene terpolymer (EPDM) was selected as an interface in electrical insulation system and the AC dielectric strength of the interface was investigated. Air compress system was used to give pressure to the interface. Specimens were prepared in various ways to generate different surface conditions for each type of interface. Increasing interfacial pressure, decreasing surface roughness and spreading oil over surfaces improve the AC interfacial dielectric strength. Especially, the dielectric strength was saturated at certain interfacial pressure.

• 한국전기전자재료학회논문지
• /
• 제19권1호
• /
• pp.40-45
• /
• 2006

Electrical insulation is one of the most important parts in a high voltage apparatus. Traditionally mineral oils and synthetic esters have been widely used as dielectric coolants for power transformers. Recently, researchers are interested in the environmentally friendly vegetable oil from the environmental viewpoint. This paper reports on the synthesis and characterization of soybean based ester oils. Two different types of soybean based transformer oils, named as methyl ester and isopropyl ester were synthesized. The synthesis of these esters was achieved by transesterification reactions between soybean oil and alcohol in the presence of catalyst. The GC and NMR spectroscopic analysis of the esters have been performed. It was observed that isopropyl ester has better thermal resistance than methyl ester by TGA. Also, two esters have a good breakdown voltage and electrical resistance.

• 한국전기전자재료학회논문지
• /
• 제16권11호
• /
• pp.1001-1007
• /
• 2003

The silicone fluids have been generally used as processing agent in silicone rubber(SIR) compounding. The addition of hydroxy silicone (HS) fluids to SIR for insulator housing material is required to meet the good electrical performance and the good processability. In this study, SIR with HS fluids was evaluated to investigate how the kinds of them affect insulation properties. The contact angle of the virgin sample of 40-HS SIR was low and its recovery rate was also slow. The recovery rate of 50-HS SIR was the highest being decreased with the viscosity increase of HS fluids. The tracking resistances and the corona aging resistance of 70-HS SIR and 1,040-HS SIR were excellent Tracking resistance depended largely on heat resistance of silicone fluids. But arc resistance didn't depend merely on the kind of silicone fluids.

• Journal of Electrical Engineering and Technology
• /
• 제12권6호
• /
• pp.2333-2341
• /
• 2017

Mineral oils are commonly used as transformer insulation oils but these oils are obtained from non-renewable and non-sustainable sources, which is highly undesirable. For this reason, natural ester oils are now being used in replacement of mineral oils because of their good biodegradability, high cooling stability, good oxidation stability and excellent insulation performance. Nanotechnology has gained prominence in both academic and industrial fields over the years and it has been shown in previous studies that nanoscale materials are useful for transformers due to their favourable dielectric properties. The objective of this study is to compare the AC breakdown voltage and viscosity of natural ester oil with three types of nanofluids. The natural ester oil-based nanofluids are prepared by mixing palm fatty acid ester (PFAE) oil with three types of nanoparticles at a concentration of 0.01 g/l: (1) $Fe_3O_4$ conductive nanoparticles, (2) $TiO_2$ semi-conductive nanoparticles and (3) $Al_2O_3$ insulating nanoparticles. The AC breakdown voltage of the oil samples is analysed using Weibull statistical analysis and the results reveal that the PFAE oil-based $Fe_3O_4$ nanofluid gives exceptional dielectric performance compared to other oil samples, whereby the AC breakdown voltage increases by 43%. It can be concluded that the PFAE oil-based $Fe_3O_4$ nanofluid is a promising dielectric liquid to substitute mineral oils.

• 한국컴퓨터산업학회논문지
• /
• 제4권4호
• /
• pp.579-588
• /
• 2003

지중전선로에 있어서 케이블을 연결하는 중간 접속재에 발생하는 전계 집중, 각종 불순물의 침투 및 케이블 절연층의 손상은 궁극적으로 열화 및 절연파괴를 야기하게 되어 케이블의 수명을 단축시키고 있다. 본 연구에서는 경계요소법을 이용하여 초고압 케이블 절연재료로 널리 사용되고 있는 가교폴리에틸렌과 접속재 키트의 절연층으로 사용되고 있는 EPDM의 전계분포를 시뮬레이션 하였다. 시료는 두께 1[mm]로 3장을 중첩한 것으로 모델링하여 컴퓨터 시뮬레이션을 하였다. 전계해석 결과 보이드 내부의 defect는 silicone oil에 의해 전계집중을 약화시킴을 확인하였고, XLPB보다 EPDM의 전계분포가 낮게 유지됨을 확인하였다.

• Journal of Electrical Engineering and Technology
• /
• 제10권6호
• /
• pp.2348-2355
• /
• 2015

Transformer mineral oil which is normally hydrocarbon based is non- biodegradable and pollutes the environment in all aspects. Though vegetable oils are eco-friendly in nature and potentially could be used in transformers as a replacement for the mineral oil, there usage is restricted because of their oxidative instability. The present work focuses on using rapeseed oil and pongamia (pongamia pinnata) oil as effective alternatives for the traditional mineral oil in power transformer. The oxidative stability of the rapeseed oil and pongamia oil is increased by using combinations of the natural and synthetic anti-oxidants as additives. The parameters like breakdown voltage, viscosity, flash point, fire point are measured for the rapeseed oil and pongamia oil with and without the additives as per IEC and ASTM standards. The results shown encouraging changes in the parameter values and ensures the use of the oils as a potential alternative insulation in power transformers.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 전기설비
• /
• pp.76-78
• /
• 2005

Moisture contents measurement is frequently used as one of parameters for degradation diagnosis of transformer insulation. In general Karl-Fisher method is mainly used for moisture contents till now. But this method is inconvenient because of dismounting transformer for sampling oil or paper, and also partial sampling. At latest Recovery Voltage Method(RVM) is noticed for complement of this method. RVM can directly estimate moisture contents of transformer insulations in field without dismounting transformer. In this paper the accelerated aging process of oil-paper samples have been investigated at a temperature up to 140$^{\circ}C$ for 500 hours. The oil-paper insulation samples have been measured at intervals of 100 hours. Next to, we have estimated moisture contents using both Karl-Fisher Titration Method and RVM. And we have compared with Karl-Fisher Titration Method and RVM for estimating moisture contents. At last we have verified reliability of RVM which is new measurement method.

• 한국조명전기설비학회지:조명전기설비
• /
• 제8권4호
• /
• pp.55-62
• /
• 1994

본 논문에서는 기존의 펌프나 가스를 이용한 강제유동식 시스템과는 달리 회전원통을 이용한 유동대전현상에 대하여 연구하여, 강제유동식에서의 대전특성과 비교, 분석하였다. 연구결과, 회전원통 시스템에서의 회전원통의 회전속도 및 온도에 따른 유동대전 특성은 강제유동식과 같은 경향을 보여 회전원통 시스템이 유동대전현상을 연구하는데 적합함을 알 수 있었다. 회전원통시스템은 강제유동식에 비하여 실험장치의 기계적 구조가 간단하고, 적은 양의 절연유만이 필요하며, 여러 가지 다른 물질로 실험하기가 비교적 편리하였다. 또한 대전 방지제의 첨가나 절연유의 열화에 따른 대전현상 등을 연속적으로 측정할 수 있는 특징이 있음을 알 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권10호
• /
• pp.523-529
• /
• 2004

Faults of cellulosic insulations greatly affect the life span of oil immersed transformers because their performance recovery is impossible. Therefore, the reliable diagnosis technologies are needed for detection of the faults. Dissolved gas analysis technologies using CO and $CO_2$ gases have been widely used for fault diagnosis of cellulosic insulations. In this research, we described Degradation diagnosis of insulation paper CO and $CO_2$ gases in oil immersed Transformers using. We considered the distribution characteristics of CO, $CO_2$ gases' concentrations and ratios of $CO_2$/CO not only in serviced transformers but in experiments with typical fault causes such as heat, partial discharge and moisture. As result, the reliability of diagnosis results for the cellulosic insulations can be improved when the concentrations of CO, $CO_2$ and the ratio of CO/$CO_2$ satisfy each diagnosis criterion at a tim

• 한국기계가공학회지
• /
• 제13권6호
• /
• pp.61-65
• /
• 2014

Construction heat insulating material for construction is used in large amounts in industry. In the manufacturing process of this insulation material, a thermal insulation material is completed while a polymer in a liquid state passes through Hall breaker. At this time, the quality and form of a product are determined by a hole in the breaker according to the oil pressure of the fluid and the change of the flow velocity. The friction wear action with regard to partner movement between the two levels of quality of materials affects the performance and the lifetimes of machine parts. In this study of a friction test, SM45C, which is a material used to create brake holes, was used. PVC was used to create the specimen. Moreover, an experiment divided a lubricous state and an unlubricated condition. The resulting value over the load of a pin, the revolving speed of a disk, and the standby state of an experimental result disk could be acquired.