• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2173-2178
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• 2007

Dynamics of plasma sheath was analyzed using simple ion fluid model with poison equation. Incident ion current, energy, potential distribution and space charge density profile were calculated as a function of time. The effects of initial floating sheath on the evolution of biased sheath were compared with ideal matrix sheath. The effects of finite rising time of pulse bias voltage on the ion current and energy was studied. The influence of surface charging on the evolution of sheath was also investigated

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.1
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• pp.69-74
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• 2007

The axial speed of plasma current sheath was measured with Rogowski coils and compared with the theory of snowplow model. Current sheath speed is measured with $10^6cm/s$. The speed of light gas, $H_2$ and He were similar to the theory of model, but the heavy gas, Ar was not similar to the theory. The disagreement of the heavy gas was guessed as a results of the instability of the current sheath.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.9
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• pp.474-481
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• 2002

Sheath circulating current is increased in the change of sheath mutual impedance which is caused by unbalanced cable system, and different section length between joint boxes. If excessive current flows in sheath, sheath loss which is reduced the transmission capacity is produced. Recently, excessive sheath circulating current was partially measured in underground cable systems of KEPCO. Accordingly, actual schemes to reduce excessive sheath circulating current are urgently required for installed cable system as well as newly-installing cable systems. This paper describes the relation analysis of sheath circulating current and burying types. And also, various schemes to reduce excessive circulating current using EMTP/ATPDraw and applicable schemes are proposed through a detailed analysis regarding cable systems by considering various electrical and environmental factors. It is evaluated that the proposed reduction schemes can be effectively applied to reduce the excessive sheath circulating current with the minimized electrical problems. And reduction effect is Proved with sheath circulating current reduction equipment.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.10
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• pp.525-533
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• 2002

It is common to install multiple lines in the same route. Recently, excessive sheath circulating current was partially measured in underground cable systems of KEPCO. Especially, the installation type, unbalance section length between joint boxes and zero sequence current by distribution cable have an effect on the rising of sheath circulating current in the underground transmission system. If excessive current flows in sheath, sheath loss which is reduced the transmission capacity is produced. This paper describes the relation analysis of sheath circulating current and burying types. And also, a detailed analysis on rising cause and characteristic of sheath circulating current by considering various unbalanced conditions presents using analysis and measurement regarding cable systems which have the problem of excessive sheath circulation current.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.320-328
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• 2007

The sheath in underground power cables serves as a layer to prevent moisture ingress into the insulation layer and provide a path for earth return current. Nowadays, owing to the maturity of manufacturing technologies, there are normally no problems for the quality of the sheath itself. However, after the cable is laid in the cable tunnel and is operating as part of the transmission network, due to network construction and some unexpected factors, some problems may be caused to the sheath. One of them is the high sheath circulating current. In a power cable system, the uniform configuration of the cables between sections is sometimes difficult to achieve because of the geometrical limitation. This will cause the increase of sheath circulating current, which results in the increase of sheath loss and the decrease of permissible current. This paper will study the various characteristics and effects of sheath circulating current, and then will prove why the sheath current rises on the underground power cable system. A newly designed device known as the Power Cable Current Analyser, as well as ATP simulation and calculation equation are used for this analysis.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.93-94
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• 2006

The sheath of a single-conductor cable for ac service acts as a secondary of a transformer, the current in the conductor induces a voltage in the sheath. When the sheaths of single-conductor cables are bonded to each other, as is common practice for multi-conductor cables, the induced voltage causes current to flow in the completed circuit. This current causes losses in the sheath. Various methods of bonding may be used for the purpose of minimizing sheath losses. In korea, sheath cross bonding system was employed for the prevention of sheath losses, the sheaths wire subjected to at voltages, and the bonding was designed to keep the magnitude of the induced voltages within small limits so as to prevent the possibility of sheath corrosion. But, sheath cross bonding system without transposition of cable can not achieve an exact balance of induced sheath voltages unless the cables are lain in trefoil. This paper describes a transposition system with sheath cross bonding using EMTP(Electromagnetic Transient Program). The transposition system with cross bonding can be extended to longer cable circuits for laid in flat as wall as trefoil by the methods described in this paper.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.57-60
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• 2008

Purpose: The radial speed of plasma current sheath was measured at the plasma focus apparatus. Methods: The measurement was used to time-resolved spectroscopic method and Rogowski coils. Results: Radial current sheath speed was measured with $10^5$ cm/s at Helium and Argon pressure between 5 to 100 torr and discharging voltage of 15 kV. When the gas pressure was increased, the current sheath speeds were decreased. Conclusions: At the optimum condition of plasma focus apparatus, the radial speed is guessed $10^7$ cm/s as a results of the measurement of current sheath speed.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.29-33
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• 2001

Sheath circulating current results from the change of sheath mutual impedance which is caused by unbalanced cable system, and different section length between joint boxes. If circulating over current flows in sheath, it produces much sheath loss which reduces the transmission capacity. And also such large sheath current influences severely on the operator. Recently, large sheath circulating current was partially measured in underground cable system of KEPCO. Accordingly, actual schemes to reduce sheath circulating over current is urgently required for installed cable system as well as newly-constructing cable system. This paper describes the analysis of sheath circulating current and various schemes to reduce the large circulating current in case of operating cable system using EMTP/ATPDraw. And also, possible schemes are proposed through a detailed analysis regarding cable systems by considering various electrical and environmental factors. It is evaluated that the proposed reduction schemes can be effectively applied to reduce the large sheath circulating over current with the minimized electrical problems.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1647-1649
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• 2003

The electric fields of the sheath region in an argon do discharge were measured using a laser optogalvanic spectroscopy in a pressure range from 0.88 to 10 Torr, where collisions are significant in the sheath region. The sheath width is estimated as the position where the electric field becomes zero, and the pressure dependence of the measured sheath width was obtained to be $(pressure)^{-1/3}$. The measured electric fields agree well with one-dimensional simulation results but are slightly different from collisional sheath theory in the mobility limited region.

• Journal of The Korean Society of Grassland and Forage Science
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• v.9 no.3
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• pp.174-178
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• 1989

The investigation was carried out to identify the main pathogen infected with sheath blight in corn plant during 1986-1987. The main fungi of sheath blight isolated from corn plant was identified as Rhizoctonia sobni. Sheath blight in corn plant was first found in early July and infected extremely from late July to end August. Severe sheath blight disease was observed in Gyeongido (Yeoju and Suweon) and Jeonnam (Kwangju) area. The rate of attack was associatied with management and cultural environments of corn plant. Dense planting increased sheath blight, but application of cattle compost reduced the rate of infection. A positive correlation was found between infection rate of shealth blight and concentration of soluble carbohydrate in corn plant (r=0.96). The varieties of Jinjuok, Suweon 83, Suweon 87, Suweon 89, P.3055, P.3160, DK689 and XCG 51 showed remarkable tolerance to sheath blight disease.