• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.7
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• pp.1281-1286
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• 2009

As a general radial configuration of power distribution system, the various researches have being studied to change a radial configuration to network one such as smart, intelligent and micro grid for loop operation. If a radial configuration changes to network, protective coordination comes to the biggest problem. When a typical protective algorithm is applied to loop distribution system protection, the interrupted section is expanded, therefore, reliability grows worse. This paper presents the new protective method being able to apply to loop distribution system with Distribution Automation System (DAS) which separate the minimal faulted section. Through contingency analysis of the sustained and momentary fault, we analyzed the influence for radial configuration and loop configuration using interrupted area and proved the effectiveness of proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1347-1352
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• 2010

This paper presents a new adaptive single-phase auto reclosure (SPAR) algorithm to discriminate between a permanent fault and a transient fault and to minimize a protection dead time. The algorithm precisely detects the extinction of the secondary arc, based on THD's profiles on the faulted phase voltage waveform. The EMTP/ATPDraw program was used to simulate the single phase grounding fault for evaluating the proposed algorithm. And the simulation results show that the proposed algorithm is performing well.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.854-859
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• 2007

A wind farm consists of many wind generator(WG)s therefore, it is generally a complex power system. A wind farm as a distributed generation(DG) affects utility power system. If a conventional protection schemes are applied, it is difficult to detect faults correctly and the schemes can't provide proper coordination in some cases. This paper presents a protection algorithm for a wind farm which consists of a looped collection circuit. Because the proposed algorithm can distinguish between an internal fault and an external fault in a wind farm, The proposed algorithm can disconnect the faulted section in a wind farm. This algorithm is based on an overcurrent protection technique with the change of the ratio of the output current of a generator to the current of the looped line connected to each generator to collect the each generator's power. In addition, operating time of the algorithm is shortened by using the voltage drop at a generator collection point. The performance of the proposed algorithm was verified under various fault conditions using PSCAD/EMTDC simulations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.651-659
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• 2007

This paper proposes an improved fault indication algorithm in a distribution automation system. A conventional fault indication method, so called YES-NO algorithm, could generate wrong informations under certain conditions such as line to ground fault, large motor double circuit line. In order to prevent mal-operation of fault indicator, direction of fault current are used as well as magnitude. The feasibility of the proposed algorithm has been testified by computer simulation using Matlab power system toolbox.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.426-428
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• 2005

Recently, There has been growing interest in new renewable energy systems with high-energy efficiency due to the increasing energy consumption and environmental pollution problems, but an insertion of new renewable energy systems to existing power distribution systems can cause several problems such as voltage variations, harmonics, protective coordination, increasing fault current etc, because of reverse power. This paper was applied to Sukumar M, Brahma, A. Girgis[1] proposal schemes and identilys the faulted section performing short-circuit analysis by MATLAB programs to 22.9[kV] distribution system interconnected a large number of new renewable energy system and was analyzed on protective coordination between reclose and Sectionalizer.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.313-315
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• 2005

Recently There has been growing interest in new renewable energy systems with high-energy efficiency due to the increasing energy consumption and environmental pollution problems. But an insertion of new distributed generation to existng power distribution systems can cause several problems such as voltage variations, harmonics, protective coordination, increasing fault current etc, because of reverse power. This paper was applied to fault location defecting a method as each Relay sensing fault current value and carried out short-circuit analysis by MATLAB and PSCAD/EMTDC programs and identity the faulted section o f22.9[kV] distribution system interconnected a large number of distributed generation. The existing protection system of 22.9[kV] power distribution system analyzed and the study on protective coordination recloser and Sectionalzer accomplished

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.127-137
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• 2007

Faults are fractures along which there is visible offset by shear displacement parallel to the fracture surface. Faults can occur as single discrete breaks, but where the rock has been repeatedly faulted, or where the rock is especially weak, no discrete break may be evident. What forms instead is a fault zone composed of countless subparallel and interconnecting closely spaced fault surfaces. Faulting is fundamentally a brittle mechanism for achieving shear displacement. At deep crustal levels where rocks tend to deform plastically under conditions of elevated temperature and confining pressure, shear displacement is achieved by and development of shear zones. In this paper authors propose the fault grade in Korea.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.276-283
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• 1994

The dislocation configuration in web-grown silicon ribbon was investigated using chemical etching techniques. The presence of dislocation loops on twin planes is observed and acounted for by self-interstitial condensation. The interstitials were either quenched in, due to the rapid cooling of the ribbon from the solidification temperatures, or produced by oxide precipitation on the twin plane. Very large faulted loops of mm size were also observed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.6
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• pp.671-677
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• 1999

In this paper, we have designed power system stabilizer (PSS) using object-oriented method. There are several types of power system stabilizer. A proportional-integral(PI) controller is very simple for practical implementation. Therefore it has been widely employed by the industry. The methods of obtaining the gains(Ki,Kp) of PI controller are root-locus method and sub-optimal regulator approach. But these methods are cannot be applicable to nonlinear system and faulted power system. So we proposed a new method which can be applied to nonlinear system by numerical analysis method. The method of dynamic system simulation by numerical method is very difficult and complex. We proposed flexible simultaion method for complex power system analysis using object-oriented programming(OOP) and applied to PI controller design.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.16-22
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• 2006

Selective ground relays (SGRs) are useful fur distinguishing a faulted feeder from the sound feeders in ungrounded systems. However, they sometimes mis-operate due to human or device errors. Particularly, the reversed polarity of zero-sequence current transducers (ZCTs) is the most frequent cause of mis-operation. This paper presents a modified SGR for reducing the probability of mis-operations caused by the reversed polarity of ZCTs. The modification is achieved by introducing an adaptive time delay, which depends on the magnitude of the zero-sequence current and the phase angle deviation from the reference. The modified SGR was successfully demonstrated on a sample ungrounded system without mis-operation.