• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.88-90
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• 2003

In this paper, an algorithm to compensate the distorted signals due to CT(Current Transformer) saturation is suggested. Firstly, WT(Wavelet Transform) is used to detect a start point and an end point of saturation. Filter banks which can be easily realized in real-time applications are employed in detecting CT saturation. Secondly, least-square curve fitting method is used to restore the distorted section of the secondary current. Fault simulations are performed on a power system model using EMTP(Electromagnetic Transient Program). A series of test results indicate that WT has superior detection accuracy and the proposed algorithm which shows very stable features under various levels of remanent flux is also satisfactory.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1073-1077
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• 2009

The iron core, which comprises the superconducting fault current limiter (SFCL) using magnetic coupling of coils, can be operated in the saturation region, especially at the initial fault period. This operation of the iron core in the saturation region deteriorates the fault current limiting operation of the SFCL. To solve the saturation problem of the SFCL using magnetic coupling of coils, the iron core with two magnetic paths, which has an air-gap in one of them, was adopted. In this paper, the hysteresis characteristics of SFCL using magnetic coupling of coils, which were wound in the iron core with two magnetic paths, were analyzed. Through comparative analysis on the hysteresis characteristics of the iron core comprising SFCL, the hysteresis characteristics of the iron core with two magnetic paths were confirmed to be kept in the non-saturation region during the fault period and thus, the effective fault current limiting operation of the SFCL using the magnetic coupling of coils could be performed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.6
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• pp.221-226
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• 2006

The current flowing though a power line is measured by a current transformer (CT). Since a CT is a kind of transformer, saturation of magnetic flux in the core may occur when a large primary current flows. This saturation makes the secondary current of a CT distorted and causes problems in the protection point of view. Because of the current distortion, a protection relay cannot collect the correct information showing how the primary power system changed. Consequently, the current distortion may cause the mal-operation or operation time delay of protective relay. In this paper, an algorithm based on AR model and LSQ is proposed to compensate the saturated CT secondary currents. Various test results indicate that the proposed algorithm can accurately compensate a severely distorted secondary current and is not affected by remanence.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.9
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• pp.446-450
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• 2000

A conventional variable percentage current differential relaying algorithm for bus protection may misoperate for external faults with severe CT saturation and internal faults with high impedance. This paper proposes a percentage differential current relaying algorithm for bus protection combined with a compensating algorithm of secondary currents of CTs. Even though CTs are saturated and their secondary currents are severely distorted, the proposed relaying algorithm does not only misoperate for external faults with CT saturation but also detects the internal faults with high fault impedance. Thus, the method improves the sensitivity of the relays and does not require any counterplan for CT saturation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.12
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• pp.773-776
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• 1999

A newly proposed lateral dual-gate thyristor was fabricated and measured, which has excellent current saturation characteristics of $1200A/cm^2$ even at an anode-gate voltage of 29V, through the elimination of the structurally existing parasitic thyristor. And through the comparison with the LIGBT, the excellent current saturation characteristics of a newly proposed device was verified.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.159-162
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• 2017

In designing the autotransformer type superconducting fault-current limiter (SFCL), one must consider that the iron core can be saturated for the SFCL to have effective fault-current limiting operation. In this paper, to examine the saturation of the iron core comprising SFCL during the fault period, the linkage flux and the magnetizing current of the SFCL were derived from the electrical equivalent circuit with the nonlinear exciting branch. By analysis on the linkage flux versus the magnetizing current of the autotransformer type SFCL, calculated from the short-circuit tests, the design condition for the suppression of the iron core's saturation was discussed.

• Progress in Superconductivity and Cryogenics
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• v.20 no.1
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• pp.15-18
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• 2018

In this paper, the magnetizing characteristics of the current limiting reactor (CLR) using $high-T_C$ superconducting (HTSC) module were analyzed. Since the saturation of iron core comprising the CLR using HTSC module deteriorates its current limiting operation, the design of the CLR using HTSC module considering the magnetizing characteristics is needed. For the analysis on the magnetizing characteristics, the flux linkage and the magnetizing current of this CLR using HTSC module were derived from its electrical equivalent circuit. Through the analysis on the linkage flux versus the magnetizing current, obtained from the short-circuit tests, the suppressing effect of the iron core's saturation was discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.66-70
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• 2007

For the design to prevent the saturation of the iron core and the effective fault current limitation, the analysis for the operation of the flux-lock type superconducting fault current limiter (SFCL) with consideration for the hysteresis characteristics of the iron core is required. In this paper, the hysteresis characteristics of the flux-lock reactor, which is an essential component of the flux-lock type SFCL, were investigated. Under normal condition, the hysteresis loss of the iron core in the flux-lock type SFCL does not happen due to its winding structure. From the equivalent circuit for the flux-lock type SFCL and the fault current limiting experiments, the hysteresis curves could be drawn. From the analysis for both the hysteresis curves and the fault current limiting characteristics due to the number of turns for the 1st and 2nd windings, the increase of the number of turns in the 2nd winding of the flux-lock type SFCL had a role to prevent the iron core from saturation.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.370-377
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• 2010

In this study, we investigated the current saturation which forces the apparent resistivity to converge when the conductivity contrast between the anomalous body and background medium is greater than a specific value. Analizing theoretical and numerical solutions for some simple models, we studied the behavior of the surface charge, and how the surface charge cause the current saturation and finally lead to the convergence of the apparent resistivity in the resistivity method. As a consequence of above analysis, we verified that the current saturation makes the apparent resistivity converge to a specific value and the magnitude of the apparent resistivity anomaly be less than that of the ideal conductor or insulator in the resistivity method. In general, current saturation is considered to occur when the conductivity contrast becomes larger than 100.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.1
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• pp.74-80
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• 1990

The transconductance of short channel LDD MOSFETs in the saturation region (high Vd)has shown different characteristics from that of conventional device. The transconductance in saturation regime of short channel LDD MOSFETs is reduced from maximum value at higher gate voltage. This decline is analyzed as the velocity saturation effects of carrier at LDD region but accurate analytical expressions for the drain current Idsat and the transconductance Gmsat in the saturation regime are still not in existence. Recently the drain current dependence of parasitic source resistance Rs has been modeled from the velocity saturation of carriers in LDD region. In this study, we approximate that Rmsat that Rs is linearly dependent on the applied gate voltage. Analytical expressions for Idsat and Gmsat obtained from this approximation show the same general behavior as experimental results of short channel LDD NMOSFETs.