• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1652-1654
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• 1994

The Extra-high voltage XLPE cable is characterized by low transmission loss, large capacity, and high reliability. Conventionally, for XLPE cables of l54kV and above, aluminium sheath was used to be moisture barrier (thus preventing water tree deterioration of the insulation) and to protect cable core from physical stresses. However, as transmission capacity of the cable increases, so does the cable diameter and the corresponding aluminium sheath outer diameter and thickness. As a result, eddy-current loss in the sheath is increased, limiting the maximum current capacity of the cable itself. As an alternative to aluminium sheath, we have adopted stainless steel sheath with non-magnetic properties and a large resistivity, The new XLPE cable with stainless-steel sheath (CSZV cable) has drastically reduced eddy-current loss in the sheath.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.428-430
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• 2000

This paper describes under-ground transmission cable sheath voltage by using EMTP and proposes a new design method for calculating cable sheath voltage in steady state. The cross bonding system of power cable is modeled on ${\pi}$ equivalent circuit and the sheath voltage(current) of cable can be analyzed with comparing to conventional method.

• 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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• 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.

• 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.

• Proceedings of the KIEE Conference
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• summer
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• pp.394-396
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• 2004

In order to reduce the sheath circulating current, same arrangement and balanced length of cable are required for the underground cable system. But practically, changing the whole arrange of cable which is already constructed is impossible. Therefore, It is necessary to apply the restraining-unit of sheath circulating current at the cross-bonding wire of insulated joint because the impedance of restraining-unit is able to reduce sheath circulating current at a normal condition. Even at a transient state, the restraining-unit must maintain electrical and mechanical characteristics. In this paper, the features of restraining-unit developed by LG Cable as well as the electrical test results are described. It proves that the restraining-unit is applicable to the underground cable system where sheath circulating current rises.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.285-288
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• 2007

This article presents the change characteristics of induced noise whether the sheath layer of the cable is grounded or not. As what affects the induced noise, there are power influence or longitudinal transverse voltages and its weighted filtered voltage. The sheath ground is basicaly predicted to have the effects of alleviation on the power influence. But practically the effects may not happen in the case of common cable's sheath layer. Rather there are cases that the ground of sheath affects so that the noise level could increase. So we need to scrutinize the effects of the sheath gorund in the measures for the protection against electromagnetic induction by powerline or traction line system. And the evaluation of using the designated shielding purpose cable is needed.

• 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.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1374-1381
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• 2010

This paper discusses the characteristics of sheath circulating current as well as the development and application of new software for underground power cable systems. Generally, in steady state, high sheath circulating current causes the increase of sheath temperature and thermal resistance which leads to the steeply reduction of the power capacity. Therefore, the exact calculation of sheath circulating current is required for analysis about the influence of high sheath current on permissible current. In this paper, Power Cable Simulator is developed for calculation of the sheath current. It can analyse the sheath current by real time. It is also easier to use than conventional software, such as EMTP and CabSim, because all the data for calculating the cable parameters are stored in a database(DB) within Power Cable Simulator. In addition, the accuracy of Power Cable Simulator is also proved through the comparison among the current calculated by Power Cable Simulator, EMTP and Cabsim with measured current.