• 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.55 no.3
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• pp.116-122
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• 2006

The underground transmission lines is continuously expanded in power systems. Therefore the fault of underground transmission lines are increased every year because of the complication of systems. However the studies dealing with fault location in the case of the underground transmission lines are rarely reported except for few papers using traveling wave method and calculating underground cable impedance. This paper describes the algorithm using fuzzy system and travelling wave method in the underground transmission line. Fuzzy inference is used for fault discrimination. To organize fuzzy algorithm, it is important to select target data reflecting various underground transmission line transient states. These data are made of voltage and average of RMS value on zero sequence current within one cycle after fault occurrence. Travelling wave based on wavelet transform is used for fault location. In this paper, a variety of underground transmission line transient states are simulated by EMTP/ATPDraw and Matlab. The input which is used to fault location algorithm are Detail 1(D1) coefficients of differential current. D1 coefficients are obtained by wavelet transform. As a result of applying the fuzzy inference and travelling wave based on wavelet transform, fault discrimination is correctly distinguished within 1/2 cycle after fault occurrence and fault location is comparatively correct.