Analysis on the Dielectric Characteristics of $SF_6$ Gas for Developing a High Voltage Superconducting Coil

남석호,홍종기,허정일,강형구,Nam, Seok-Ho,Hong, Jong-Gi,Heo, Jeong-Il,Kang, Hyoung-Ku The Korean Superconductivity Society 2012 Progress in superconductivity Vol.13 No.3

Studies on the development of high voltage superconducting apparatuses, such as transmission superconducting fault current limiters (SFCLs) and superconducting cables, have been performed worldwide. In this paper, a study on the electrical insulation characteristics of electro negative gas according to various pressures and utilization factors was conducted as a part of developing a high voltage superconducting coil with a sub-cooled nitrogen cooling system. Some gases such as helium (He), nitrogen ($N_2$), and sulfur hexafluoride ($SF_6$) are considered for pressurizing the sub-cooled nitrogen cooling system of high voltage SFCLs and superconducting cables. $SF_6$ is used to pressurize and enhance the dielectric performance of a superconducting system of a sub-cooled nitrogen cooling system for superconducting cables being developed in the Republic of Korea. In this paper, dielectric experiments on AC voltage, as well as lightning impulse voltage of $SF_6$, are conducted according to various utilization factors by using several kinds of sphere-to-plane electrode systems. As results, it is known that the empirical formulae of $SF_6$, known as an electro negative gas, are derived according to various pressures and utilization factors. Also, the appropriate pressure condition for designing a high voltage superconducting coil is found from the viewpoint of dielectric performance.

유한요소법을 이용한 22.9kV용 Polymer COS의 구조물 형태에 따른 전계분포 분석

남석호,허정일,홍종기,안영대,이종득,강형구 대한전기학회 2012 대한전기학회 학술대회 논문집 Vol.2012 No.7

고압배전반의 전기적 안정성 향상을 위한 버스바의 배치기법에 따른 전자기 특성에 관한 연구

남석호,허정일,홍종기,강형구,Nam, Seokho,Heo, Jeong Il,Hong, Jonggi,Kang, Hyoungku 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.3

The rated voltage has been rising in order to minimize the losses in power transmission. The high voltage electric machines should be minimized due to the constraints of space. Therefore, the temperature of high voltage electric apparatuses easily exceeds the temperature limits. In this paper, it is investigated that how to minimize the internal temperature rising of a high voltage switchgear by adjusting the arrangement of bus bars. High voltage switchgears consist of a circuit breaker, a CT, a PT, a earthing switches, bus bars, and so on. It is very difficult to estimate the electromagnetic properties of a high voltage switchgear due to these various environments and structures. In this paper, analyses are focused on the electromagnetic characteristics of bus bars according to the arrangement method and the enclosures to simplify the electromagnetic characteristics of a switchgear. It is found that the characteristics of electric field intensity and electromagnetic losses in bus bars are influenced by the arrangement method of bus bars. However, it is confirmed that the electromagnetic characteristics of enclosures are not affected by the arrangement of bus bars. In this paper, the arrangement methods of bus bars to minimize the electric field intensity and electromagnetic losses are suggested. It is expected that the research results are helpful to design and develop an electrically reliable high voltage switchgear.

Incomplete form of Sturge-Weber Syndrome

남석호,임창수,이기찬,김혜연,지제근 대한신경외과학회 1985 Journal of Korean neurosurgical society Vol.14 No.2

Sturge-Weber syndrome is a neurocutaneous syndrome characterized by port-wine nevus of the face with angiomatosis of the ipsilateral cerebral leptomeninges and extensive calcification in the underlying cerebral cortex. Associated features include mental retardation, generalized or focal seizures, hemiparesis, choroidal angioma, & buphthalmos or glaucoma. We experienced a case of incomplete form of Sturge-Weber syndrome in a 12 year-old boy, who had generalized seizure, a homonymous hemianopsia, intracranial calcification and leptomeningeal angiomatosis without facial nevus or mental retardation. So we presented a case with a brief review of related literatures.

실험적 뇌지주막하출혈후 연축혈관의 미세구조학적 변화

남석호,이훈갑,이기찬,주정화 대한신경외과학회 1986 Journal of Korean neurosurgical society Vol.15 No.3

Studies of the pathophysiology of intracranial artery following vasospasm remains yet incomplete. The present investigation was undertaken for the purpose of elucidating ultrastructural changes in the cerebral arterial wall sequentially from 1hour to 24 hours following subarachnoid hemorrhage. Experimental vasospasm was induced by injecting autogenous blood into the cisterna magna of cats. The following observations were made: 1) One hour after the induction of subarachnoid hemorrhage, endothelial cells in the intima became more round and their cellular surface was markedly corrugated, these changes culminated at 7 to 24 hours with intimal thickening (due to subendothelial tissue) 2) In the media, the smooth muscle cells were most consistently and severely affected showing degeneration of mitochondria and vacuoles containing fine particles. 3) Twelve hours following SAH, some endothelial cells in the intima were displaced or seemed to have partially broken apart from the adjoining cells. On the basis of the above findings, it was concluded that the ultrastructural changes in the cerebral arterial wall was observed after the induction of SAH with normal cat's blood occured as a consequence of vasospasm of the intracranial arteries.

친환경 고압배전반 개발을 위한 dry air의 압력별 절연내력특성 분석에 관한 연구

남석호(Seok Ho Nam),강형구(Hyoungku Kang) 대한전기학회 2011 전기학회논문지 Vol.60 No.8

The environmental pollution caused by green-house gases such as CO₂ and SF6 has been becoming the main issue of industrial society. Many developed countries are making efforts to minimize the amount of CO₂ emission come from the operation of high voltage electrical apparatuses. As a part of these efforts, 180 countries signed the Kyoto Protocol in 1997 to cut back on their green-house gas emissions. Nowadays, the study on the development of dry air insulated switchgear (DAIS) which is known as an eco-friendly electrical apparatus is in progress. A DAIS is advantageous for minimizing the effect of impurities and enhancing the dielectric characteristics over an air insulated switchgear (AIS) by applying constant pressure to an enclosed cubicle. Therefore, a study on the electrical insulation performance of dry air as a gaseous insulation medium is conducted in this paper to substitute a gas insulated switchgear (GIS) for DAIS. As results, it is verified that the AC dielectric characteristics of dry air are similar to those of air and the lightning impulse dielectric characteristics of dry air are superior to those of air at 1bar pressure condition. However, dry air is of inferior dielectric characteristics to SF6 at 4bar pressure condition. Finally, it is suggested that the internal pressure of DAIS should be over 4bar pressure to develop a high voltage switchgear which has similar electrical performance to a conventional GIS. Also, the empirical formulae on calculating the maximum electric field intensity at sparkover of dry air are deduced by experiments according to pressures. It is expected that these results are helpful to design and develop a high voltage electrical apparatus.

고전압 전력기기 개발을 위한 기중 절연파괴특성 분석에 관한 연구

남석호(Seok Ho Nam),강형구(Hyoungku Kang) 대한전기학회 2011 전기학회논문지 Vol.60 No.5

The accidents caused by dielectric instability have been increasing in power grid. It is important to enhance the dielectric reliability of a high voltage apparatus to reduce the damage from electrical hazards. To develop an electrically reliable high voltage apparatus, the experimental study on the electrical breakdown field strength is indispensable, as well as theoretical approach. In this paper, the lightning impulse breakdown characteristics considering utilization factors are studied for the establishment of insulation design criteria of an high voltage apparatus. The utilization factors are represented as the ratio of mean electric field to maximum electric field. Dielectric experiments are performed by using several kinds of sphere-plane electrode systems made of stainless steel. As a result, it is found that dielectric characteristics are affected by not only maximum electric field intensity but also utilization factors of electrode systems. The results are expected to be applicable to designing the air-insulated high voltage apparatuses.

사이리스터로 조절되는 초전도 한류기의 전류제한특성 연구

남석호(Seokho Nam),이우승(Woo Seung Lee),이지호(Jiho Lee),박영건(Young Gun Park),고태국(Tae Kuk Ko) 대한전기학회 2014 대한전기학회 학술대회 논문집 Vol.2014 No.10

Effect of Active Stretching and Instrument-Assisted Soft Tissue Mobilization on the Hip Joint Range of Motion and Stiffness of the Tensor Fascia Lata in Subjects with Shortened Tensor Fascia Lata

임진용,남석호,김경돈 KEMA학회 2022 근골격계과학기술학회 Vol.6 No.2

Background Various therapeutic methods have been suggested to increase the flexibility of shortened muscles in patients with knee pain. However, no previous study has directly compared the hip joint range of motion (ROM) and muscle stiffness as a mechanical property following the active stretching (AS) and instrument-assisted soft tissue mobilization (IASTM) for shortened tensor fascia lata (TFL). Purpose To compare the effects of AS and IASTM on hip joint ROM and TFL stiffness in subjects with shortened TFL. Study design Two groups pre- and post-test design Methods Twenty healthy male subjects with shortened TFL were selected. The subjects were randomized between the AS group (n=10) and the IASTM group (n=10). A smartphone was used to measure the hip joint adduction ROM and Myoton was used to measure the TFL stiffness. Paired t-test was performed to analyze the within-group variation before and after the intervention, and an independent t-test was used to compare the between-group variation. Results In the within-group comparison, both the AS and IASTM groups showed a significant increase in the hip joint adduction ROM after the intervention, whereas neither group showed a significant difference in the TFL stiffness after the intervention. In the between-group comparison, a greater increase in the hip joint adduction ROM was observed for the AS group compared to the IASTM group. Conclusions This study found that the hip adduction ROM of the subjects with TFL shortness increased immediately in both AS group and IASTM group, although the TFL stiffness was not decreased. And the greater increase of the hip adduction ROM was revealed in AS group than IASTM group.

마늘成分이 mouse 肝 Aniline Hydroxylase 活性에 미치는 影響

허근,남석호,박종민,장억규 영남대학교 자원문제연구소 1985 資源問題硏究 Vol.4 No.-

Garlic (Allium sativum) is a widely distributed plant used in all parts of the world not only as a spice and a food but also a popular remedy. The active component of garlic has been known as allicin which is formed by the enzyme alliinase from alliin. This study is associated with the effect of garlic component on the drug-metabolism. After garlic-juice (0.5 w/v %) was administered to mouse 60 days, the results were as follow. 1. Pentobarbital sleeping time was decreased by 30% 2. Pentobarbital levels in plasma and liver were decreased to a extent of 27%, 33%, respectively. 3. The content of microsomal cytochrome P-450 was increased to approximately 17%. 4. In comparison to control, aniline hydroxylase activity was increased around 50%. By the way, allicin fraction inhibited aniline hydroxylase activity in vitro. These observations led us to conclude that shortening of pentobarbital sleeping time and decrease of pentobarbital concentrations in plasma and liver were attributed to the induction of drug-metabolizing enzyme by garlic component. It can be considered that allicin should not be a drug-metabolizing enzyme inducer, but further investigations about this point be needed.