• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.112-113
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• 2006

The operational characteristics of the integrated three-phase flux-lock type superconducting fault current limiter (SFCL) were analyzed. The suggested three-phase SFCL consisted of a three-phase flux-lock reactor and three high-$T_c$ superconducting (HTSC) elements. The former has three windings wound on an iron core, each of which has the same turn's ratio between coil 1 and coil 2. The latter are connected in series with coil 2 of each phase. The integrated three-phase flux-lock type SFCL showed the operational characteristics that the fault phase could affect the sound phase, which resulted in quenching the HTSC element in the sound phase. Through the computer simulation applying numerical analysis for its three-phase equivalent circuit, the fault current limiting characteristics of the integrated three-phase flux-lock type SFCL according to the ground fault types were compared.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2003년도 학술대회논문집
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• pp.279-281
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• 2003

We analysed the operating properties of resistive type superconducting fault current limiters (SFCLs) based on YBCO thin films with a single line-to-ground fault. When a single line-to-ground fault occurred, the short circuit current of a fault phase increased up to about 6 times of transport currents immediately after the fault instant and was effectively limited to the designed current level within 2 ms by the resistance development of the SFCL. The fault currents of the sound phases almost did not change because of their direct grounding system. The unsymmetrical rates of a fault phase were distributed from 6.4 to 1.4. It was found that the unsymmetrical rates of currents were noticeably improved within one cycle after the fault instant. We calculated the zero phase currents for a single line-to-ground fault using the symmetrical component analysis. The positive sequence resistance was reduced remarkably right after the fault but eventually approached the balanced positive resistance component prior to the system fault. This means that the system reaches almost the three-phase symmetrical state in about 60 ㎳ after the fault. The ground currents were almost 3 times of the zero phase mts since most of the fault currents flowed through the grounding line.

• 전력전자학회논문지
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• 제18권3호
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• pp.205-210
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• 2013

This paper presents a novel hall sensor fault detection and fault-tolerant control method for a high-speed permanent magnet synchronous motor (PMSM) drive system. A phase locked loop (PLL) type position estimator is used with a conventional interpolation based rotor position estimator to reduce position errors due to misalignment of hall sensors. The expected trigger time of hall sensor's output is used for detecting hall sensor fault condition and the PLL type position estimator is reconfigured for fault-tolerant control at the hall sensor fault condition. The proposed method can minimize current ripples during the transition from sensored control using hall sensors to sensorless control. Experimental results have been proposed to prove the validity of the proposed method.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.78-85
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• 2006

The Ulsan Fault System continues from north of Gyeongju to Ulsan city, trending NNW-SSE and is about 50 km. Many Quaternary faults have been reported and investigated with outcrop observation. Lineaments have been extracted with aerial photograph interpretation and classified by their ranks. Trench excavations on the lineaments along Ulsan Fault System have been carried out to clarify the neotectonic movements and fault parameters such as the latest movement age, fault displacement, slip rate and recurrence interval. We have compiled data from previous studies on criteria of segment type such as lineament rank, seismicity, slip rate, and the latest fault movement. Based on these data, we tried to devide the Ulsan Fault System into several segments. The results of segmentation with each types of segment along the Ulsan Fault System did not show singular division point but overlapped or different length and location.

• Journal of Power Electronics
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• 제12권1호
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• pp.10-18
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• 2012

This paper proposes a finite element method (FEM)-based model of an interior permanent magnet (IPM)-type BLDC motor having stator inter-turn faults. We also propose impedance modeling of the magnetic characteristics. By integrating the developed model with a current-controlled voltage source inverter (CCVSI) model, the distributed characteristics of an inter-turn fault operated by a six-switch inverter are investigated considering speed control. Moreover, this paper presents the flux density distribution and torque characteristics for analyzing the inter-turn fault of an IPM-type BLDC motor. Additionally, fault impedance is required to calculate the circulating current that causes magnetic distortion. Thus, this paper proposes a method for estimating the circulating current taking into account the voltage at the shorted turn and the rotating speed. The analysis data were verified experimentally.

• 한국초전도ㆍ저온공학회논문지
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• 제13권3호
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• pp.14-18
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• 2011

Electrical system is changing to smart grid which includes the distributed generations with reusable energy sources in these days. The distributed generations are environmentally friendly and have no concern with depletion problem. But dispatching distributed generations can cause an increase of the fault current. Resistive type super conducting fault current limiter is one of the candidates of solution for the large fault problem in smart grid. In this paper, a design method for the wire length of fault current limiter and the result of short circuit test for small scale modules considering system resistance are introduced.

• 한국초전도ㆍ저온공학회논문지
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• 제5권2호
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• pp.1-7
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• 2003

Nowadays, one of the serious problems in KEPCO(Korea Electric Power Co-Operation) system is the more higher fault current than the SCC(Short Circuit Capacity) of circuit breaker. There are many alternatives to reduce the increased fault current such as isolations of bus ties, enhancement of SCC of circuit breaker, applications of HVDC-BTB(High Voltage Direct Current-Back to Back) and FCL(fault current limiter). But, these alternatives have some drawbacks in viewpoints of system stability and cost. As the superconductivity technology has been developed, the HTS-FCL(High Temperature Superconductor -Fault Current Limiter) can be one of the attractive alternatives to solve the fault current problem. Under this background, this paper presents the EMTDC(Electro-Magnetic Transient Direct Current) model for resistance type HTS-FCL considering the nonlinear characteristic of final resistance value when quenching phenomena occur.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.332-334
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• 2003

The direction and the type of a fault on a transmission line needs to be identified rapidly and correctly. This paper presents a approach to identify fault direction and type with neural network on double circuit transmission line. A neural network based on self organization map(SOM) provides the ability to accurately classify the fault type and to select of a fault direction. In this paper, proposed algorithm uses different patterns of the associated voltages and currents in order to identify fault clusters.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.143-145
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• 1996

This paper presents the hybrid type based expert system for fault diagnosis in transformers. The proposed system uses the novel fault diagnostic technique based on dissolved gas analysis(DGA) in oil-immersed transformers. The uncertainty of key gas analysis, norm threshold, and gas ratio boundaries are managed by using a fuzzy set. Also, the uncertainty of the fault diagnostic rules are handled by using fuzzy measures. Finally, kohnen's feature map performs fault classification in transformers. To verify the effectiveness of the proposed diagnosis technique, the hybrid type based expert system for fault diagnosis has been tested by using KEPCO's transformer gas records.

• Transactions on Electrical and Electronic Materials
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• 제18권3호
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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.