• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1025-1027
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• 1997

In this paper, the digital distance relay of transmission lines under fault conditions is discussed. Distance relay is used to protect transmission lines. The principle of distance relay is well-known ; the impedance measured by a relay is Proportional to the distance from the relay to the fault. Hence, by measuring the impedance, it can be determined whether the line is faulted or not. Unfortunately, the measurement of the fault distance is distorted by Mutual Coupling. To implement more reliable and practical digital distance relay, the mutual coupling effect has to be considered.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.8-15
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• 2010

This paper analyzes the steady-state output characteristics of variable-speed wind turbine systems using doubly-fed induction generators(DFIG) compared with fixed-speed induction generator(FSIG) wind turbine systems. It also presents simulations of a grid-connected wind turbine generation system for dynamics analysis on MATLAB/Simulink and compares the responses between DFIG and FSIG wind turbine systems with respect to wind speed variation, impedance changes and X/R ratio changes of interconnecting circuits. Simulation results show the variation of generator's active output, terminal voltage and fault currents at the interconnecting point. Case studies demonstrate that DFIG wind turbine systems illustrate better performance to 3-phase fault than FSIG's.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.509-512
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• 1995

The relaying algorithm to calculate the fault distance from only transient signal at faults in T/L is presented. In this paper. At faults the oscillation frequency components exist in both voltage and current and these components minimize the input impedance shown in fault point. The equivalent source impedance shown in relaying point is needed to calculate the fault distance using these components. To source impedance, the reflection coefficient between forward wave and backward and the Prony's analysis is also employed to extract the oscillation frequency component from transient signals. The case study show that the new distance relaying algorithm satisfies the high operation speed and high accuracy even if the algorithm uses only transient signals.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.270-272
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• 2018

This paper proposes an open-phase fault control system using 3-phase neutral voltage. The proposed control system is designed as a new topology which uses the potential difference between neutral point and ground(G) of three phase. And the open-phase detection system is configured to three resistance devices(Y-wiring) of the same capacity to each line of three phase power source R,S,T. This paper also designs a mobile phone application for remote alarm of open-phase fault.

• Journal of Information Processing Systems
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• v.8 no.1
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• pp.21-54
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• 2012

As we know every software development process is pretty large and consists of different modules. This raises the idea of prioritizing different software modules so that important modules can be tested by preference. In the software testing process, it is not possible to test each and every module regressively, which is due to time and cost constraints. To deal with these constraints, this paper proposes an approach that is based on the fuzzy multi-criteria approach for prioritizing several software modules and calculates optimal time and cost for software testing by using fuzzy logic and the fault tolerance approach.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.3
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• pp.173-178
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• 2003

This paper proposes a three-winding transformer protective relaying algorithm based on the ratio of the induced voltages (RIV). The RIV of the two windings is the same as the turn ratio for all operating conditions except an internal fault. For a single phase and a three-phase transformer containing the wye-connected windings, the induced voltages of the windings are estimated. For a three-phase transformer containing the delta-connected windings, the induced voltage differences are estimated using the line currents, because the winding currents are practically unavailable. The algorithm can identify the faulted phase and winding if a fault occurs on one phase of a winding. The test results clearly show that the algorithm successfully discriminates internal winding faults from magnetic inrush. The algorithm not only does not require hysteresis data but also can reduce the operating time of a relay.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.893-895
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• 1998

This paper presents the adaptive setting method of distance relay under the single line ground fault. The apparent impedance measured at the relaying point and actual impedance is different because of fault resistance and various prefault loading condition. For a resistance earth fault detection, relay setting zone is adaptively changed with measured load current and bus voltage at the relaying point to avoid maloperation.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.822-827
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• 2004

In this paper, an intelligent fault diagnosis system is proposed for induction motors through the combination of feature extraction, genetic algorithm (GA) and neural network (ANN) techniques. Features are extracted from motor vibration signals, while reducing data transfers and making on-line application available. GA is used to select most significant features from whole feature database and optimize the ANN structure parameter. Optimized ANN diagnoses the condition of induction motors online after trained by the selected features. The combination of advanced techniques reduces the learning time and increases the diagnosis accuracy. The efficiency of the proposed system is demonstrated through motor faults of electrical and mechanical origin on the induction motors. The results of the test indicate that the proposed system is promising for real time application.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.1
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• pp.10-15
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• 1990

This paper presents an algorithm that can compute equivalent impedance effctively in computing 3-phase short circuit current which would be generated in power systems. Also this paper proposes a method that can decide the capacity of circuit breaker by analysing the fault current distribution probabilistically when the fault point of specificed line varies. The efficiency of the algorithm was verified by applying the proposed method to IEEE-6bus system and IEEE-30bus system, and probabilistic fault analysing method is verified economic in facility investment by deciding the proper capacity of circuit breaker.

• Journal of Power Electronics
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• v.6 no.3
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• pp.245-252
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• 2006

This paper presents a method based on neural networks to detect the broken rotor bars and end rings of squirrel cage induction motors. At first, detection methods are studied, and then traditional methods of fault detection and dynamic models of induction motors by using winding function model are introduced. In this method, all of the stator slots and rotor bars are considered, thus the performance of the motor in healthy situations or breakage in each part can be checked. The frequency spectrum of current signals is derived by using Fourier transformation and is analyzed in different conditions. In continuation, an analytical discussion and a simple algorithm are presented to detect the fault. This algorithm is based on neural networks. The neural network has been trained by using information of a 1.1 KW induction motor. This system has been tested with a different amount of load torque, and it is capable of working on-line and of recognizing all normal and ill conditions.