• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.117-122
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• 2015

Our research team proposed a flux-offset type fault current limiter as a new limiter. The flux-offset type fault current limiter uses a fault current limit technology based on the flux offset principle of the primary and secondary windings of a transformer. Stable fault current limit characteristics were achieved through a preliminary study. However, it was discovered that the initial fault current was not limited. Therefore, in this paper, a high-speed interrupter and a superconducting element were separately applied to the secondary winding of the flux-offset type fault current limiter and the operating characteristics were comparatively analyzed. In the experiment, when the superconducting element was applied to the secondary winding of the transformer, the initial fault current was limited while the limitation in the operation time was further shortened.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.1
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• pp.120-127
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• 1991

The purpose of this study is to develop a fault detection and diagnosis scheme that can monitor process fault and instrument fault of a steam generator. The suggested scheme consists of a Kalman filter and two bias estimators. Method of detecting process and instrument fault in a steam generator uses the mean test on the residual sequence of Kalman filter, designed for the unfailed system, to make a fault decision. Once a fault is detected, two bias estimators are driven to estimate the fault and to discriminate process fault and instrument fault. In case of process fault, the fault diagnosis of outlet temperature, feed-water heater and main steam control value is considered. In instrument fault, the fault diagnosis of steam genrator's three instruments is considered. Computer simulation tests show that on-line prompt fault detection and diagnosis can be performed very successfully.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.3 s.18
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• pp.140-148
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• 2004

Fault detection and isolation(FDI) and reconfigurable flight control system provide better survivability even though actuator faults occur. In this study, a new fault detection and isolation algorithm is proposed using fuzzy logic. When the FDI system detects the actuator fault, the fuzzy logic investigates the state variables to find which actuator has fault. Proposed fuzzy detection algorithm detect not only a single fault but also multiple faults. After detecting the fault, the reconfigurable flight control system begins operating for compensating the effects of the fault. A numerical simulation using six degree-of-freedom nonlinear aircraft model is performed to verity the performance of the proposed fault detection and isolation scheme.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11b
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• pp.3-17
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• 2002

Tertiary Pohang basin distributed in south weatern part of the korean peninsula, is composed of Chunbuk formation as the basal conglomerate, Hakjon formation, Duho formation and intrusive basalt which is 15 Ma by absolute age data. The basement of the basin is represented by Cretaceous sedimentary rocks, Hakjon welded tuff and Chilpo welded tuff and rhyolite. The fault systems at the basement of the Pohang basin are consist of NNE direction fault, WNW to EW trend fault. NNE fault is not only strike-slip fault but also normal fault. n fault has sinistral strike-slip sene and the EW fault is strike-slip and normal fault. In the Tertiary basin, the fault system is represented by nm strike-slip fault, EW normal fault and NNE thrust fault. By these fault relationships and geometries, it is interpreted that NNE sinistral strike-slip fault and nomal fault have acted at Creceous times. At Tertiary tines, NNE dextralstrike-slip fault and EW normal fault has created. Progressively Tertiary Pohang basin was influenced by the trenspression to make thrust fault and fold, namely as inversion tectonics.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.7
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• pp.37-44
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• 2013

Phase to ground faults are possibly one of the maximum number of faults in power distribution system. During a ground fault the maximum fault current and neutral to ground voltage will appear at the pole nearest to the fault. Distribution lines are consisted of three phase conductors, an overhead ground wire and a multigrounded neutral line. In this paper phase to neutral faults were staged at the specified concrete pole along the distribution line and measured the ground fault current distribution in the ground fault current, three poles nearest to the fault point, overhead ground wire and neutral line. A simplified equivalent circuit model for the distribution system under case study calculated by using MATLAB gives results very close to the ground fault current distribution yielded by field tests.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.932-941
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• 2004

The objective of this study is to detect the multi-fault of HVAC system using a new pattern classification technique. To classify the effect of single-fault in determining the pattern, supply air temperature, OA-damper, supply fan, and air flowrate were chosen as experimental parameters. The combination of supply temperature, flow rate, supply fan and OA-damper were chosen as multi-fault conditions. Three kinds of patterns were introduced in the analysis of multi-fault problem. To solve multi-fault problem, the new pattern classification technique using residual ratio analysis was introduced to detect the multi-fault as well as single-fault. The residual ratio could diagnose single-fault or multi-fault into several patterns.

• Journal of Korean Society for Quality Management
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• v.21 no.1
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• pp.78-95
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• 1993

The art of designing and analyzing fault-tolerant computers is surveyed with special emphasis on problems of analyzing the behavior of computers that have autonomous repair capability. The survey covers the following topics : (1) general issues in computer reliability, (2) fault-tolerance state relations and requirements, (3) computational hierarchy, (4) fault characteristics, (5) fault diagnosis, (6) fault-tolerance schemes for logic network and machines, (7) fault-coverage effects, and (8) fault-tree analysis of coverage. This paper does not include techniques for verifying nonredundant hardware or system software designs or for verifying the correctness of application programs.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.4
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• pp.291-296
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• 2015

Transmission line is exposed to a large area, and then faults are likely to occur than the other component of power system. When a fault occurs on a transmission line, fault locator helps fast recovery of power supply on power system. This paper deals with the design of a digital fault locator for improvement accuracy of the fault distance estimation and a fault occurrence position for transmission line. The algorithm of a fault locator uses a DC offset removal filter and DFT filter. The algorithm utilizes a fault data of GPS time synchronized. The computed fault information is transmitted to the other side substation through communication. The digital fault locator includes MPU module, ADPU module, SIU module, and a power module. The MMI firmware and software of the fault locator was implemented.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.10-11
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• 2006

The fault location is obtained from the distance relay that detects the fault of the transmission line. In this time, transmission line crews track down the fault location and the reasons. However, because of having error at the fault location of the distance relay, there is a discordance between real and obtained fault location. As this reason, the inspection time for finding fault location can be longer. In this paper, we proposed the statistical (regression) analysis method based on each type of relay's the historical fault location data and the real fault distance data to improve the problems. With finding the regression equation based on the regression analysis, and putting the relay fault location into that equation, the real fault distance is calculated. As a result of the Prediction fault location, the inspection time of transmission line can be reduced.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.130-130
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• 2000

This paper presents a robust fault diagnosis and fault tolerant control lot the actuator and sensor faults in the closed-loop systems affected by unknown inputs or disturbances. The fault diagnostic scheme is based on the residual set generation by using robust Parity space approach. Residual set is evaluated through the threshold test and then fault is isolated according to the decision logic table. Once the fault diagnosis module indicates which actuator or sensor is faulty, the fault magnitude is estimated by using the disturbance-decoupled optimal state estimation and a new additive control law is added to the nominal one to override the fault effect on the system. Simulation results show that the method has definite fault diagnosis and fault tolerant control ability against actuator and sensor faults.