• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.19-21
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• 2001

Induction motors are a critical component of many industrial machines and are frequently integrated in commercial equipment. The many economical losses and the deterioration of system reliability might be caused by the failure of induction motors in industrial field. Based on the reliability and cost competitiveness of driving system(motors), the faults detection and diagnosis of system is considered very important factors. In order to perform the faults detection and diagnosis of motors, the vibration monitoring method and motor current signature analysis (MCSA) method are emphasized. In this paper, MCSA method is used for induction motor fault diagnosis. This method analyzes the motor's supply current, since this diagnoses the motor's condition. The diagnostic system is constructed by using LabVIEW of National Instruments.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.9
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• pp.1351-1363
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• 1990

In this paper, a reliable control system structured with dual CPU modules and dual I/O modules is implemented as a means of achieving a highly reliable fault tolerant control system. For this, faults in the system modules are first examined, and a fault detection technique consisting of self diagnostic, comparison process, and exception processing is applied. Self diagnostic is used to locate which components in the modules have been failed, while comparison process is to cmpare control outputs computed by both CPU modules and protect the plant from malfunction by blocking failed control outputsin advance. Finally exception processing is used to determine the faults that are not detected immediately by the self diagnostic and comparison process, e.g. bus error processing when acknowledge signal for data transfer is not activeted in the I/O modules. Also reliability analysis is conducted for the discrete time Markov model with dual structure. It is shown quantitatively that the reliability is improved in the control system with dual structure in comparison with a system with single module structure.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1980-1983
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• 2002

When a feedback bridging fault is activated in a circuit, logical oscillation may occur at a signal line. If the oscillation appears, the fault may not be detected by logic testing. In order to detect such bridging faults, output logic values of the circuit should be measured at higher frequency than frequency of the logical oscillation. In this paper, a method fur estimating the maximum frequency of logical oscillation is proposed to detect such bridging faults in a circuit by logic testing. Also, it is shown by some experiments that such bridging faults can be detected by measuring output logic values at the frequency obtained by the method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.3
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• pp.158-164
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• 2003

This paper proposes a percentage current differential relaying algorithm for bus protection using an advanced compensating algorithm of the secondary current of current transformers (CTs). The compensating algorithm estimates the core flux at the start of the first saturation based on the value of the second-difference of the secondary current. Then, it calculates the core flux and compensates distorted currents using the magnetization curve. The algorithm Is unaffected by a remanent flux. The simulation results indicate that the proposed algorithm can discriminate internal faults from external faults when the CT saturates. This paper concludes by implementing the algorithm into a TMS320C6701 digital signal processor. The results of hardware implementation are also satisfactory. The proposed algorithm can improve not only stability of the relay in the case of an external fault but sensitivity of the relay in the case of an internal fault.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.98-106
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• 2009

This paper proposes an optical wireless transfer agent method which realizes the continuous and swift data transfer of optical wireless terminals in optical wireless networks. The unguided wireless channel generally shows frequent link disconnections and propagation delays due to weak wireless links. Specially speaking, optical wireless channels have more vulnerable links and roaming propagation delays relative to the weakness of the previous RF channels due to their low signal connectivity and small geographic coverage. Conventional optical wireless network protocols did not consider any fault models about physical link faults. Consequently, they have shown data transfer inefficiency for both data link control and physical wireless link control. To overcome these optical wireless environmental problems, this paper suggests a new wireless access point (or base station) agent system, which provides wireless or mobile clients with previous link layer protocols compensated.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1488-1494
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• 2006

The most important thing to secure safety and reliability of railway vehicles is to verify performance characteristics of equipments, and related companies or research institutes had many efforts to verify performances and functions of equipments synthetically and efficiently. KHST(Korean High Speed Train) has been developed by KRRI(Korea Railroad Research Institute). An electric railway system is composed of high-tech subsystems, among which main electric equipment such as transformers and converter are critical components determining the performance of rolling stock. We developed a measurement system for on-line test and evaluation of performances of KHST. The measurement system is composed of software part and hardware part. Perfect interface between multi-users is possible. A new method to measure temperature was applied to the measurement system. By using the system, fault diagnosis and performance evaluation of electric equipment in Korean High Speed Train was conducted during test running.

• Journal of Power Electronics
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• v.12 no.6
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• pp.982-991
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• 2012

In this study, a new method has been presented for the detection of broken rotor bar (BRB) faults in inverter driven induction motors controlled via Field Oriented Control (FOC). To this end, a FOC controlled induction motor with a BRB fault was modeled using the Matlab/Simulink program. Experiments were carried out using the prepared simulation model at various loads and operating speeds. The motor current and speeds were monitored for healthy, 1, 2 and 3 BRB faults. The Resampling Based Order Tracking Analysis (RB-OTA) method was applied to the monitored signals. The obtained results were compared by using the classic Fast Fourier Transform (FFT) method. When the obtained results were analyzed via the FFT method no information regarding any faults was determined in the run up or run down regions of the motor and the presented method gave very good results. The reliability of the proposed method was validated with experimental results. The main innovative part of this study is that the RB-OTA method was implemented on the induction motor current signal for detecting BRB faults.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2076-2078
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• 2003

전력 케이블의 고장점 탐지를 상시 감시하고 있는 데이터로부터 on-line으로 할 수 있도록 하기 위한 전력 케이블 고장 신호의 전처리 기술 개발에 관하여 언급하였다. 고장 전류 파형을 모의하고 측정할 수 있는 케이블 고장 모의 측정 시스템을 구성하여 고장 전압과 전류 파형을 측정하였으며 측정된 신호로부터 고장점을 보다 정확하고 빠르게 연산할 수 있도륵 하기 위한 down sampling, filtering 등 전처리 과정에 대하여 시뮬레이션하고 그 결과에 대하여 논하였다.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.156-158
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• 1993

This paper presents several techniques of power spectrum estimation for high impedance fault detection. High impedance faults are those faults with current too low to be reliably cleared by conventional overcurrent protection. So power spectrum estimation is required. AR and MA techniques require optimal order for good performance of power spectrum estimation because these techniques are unstable for order selection. ARMA and Extended techniches are stable for order selection and have very sharp response. So ARMA and Extended Prony techniques are suitable for our purpose.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.377-382
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• 2008

For stator winding protection of AC generator, KCL(Kirchhoff's Current Law) is widely applied. Actually a CRDR(Current Ratio Differential Relay) based on DFT(Discrete Fourier Transform) has been used for protecting generator. It has been pointed out that defects can occur during the process of transforming a time domain signal into a frequency domain one which can lead to loss of time domain information. Wavelets techniques are proposed for the analysis of power system transients. This paper introduces an algorithm to choose a suitable Mother Wave1et for generator stator fault detection. For optimal selection, we analyzed db(Daubechies), sym(Symlets), and coif(Coiflects) of Mother Wavelet. And we compared with performance of the choice algorithm using detail coefficients energy and RMS(root mean square) error. It can be improved the reliability of the conventional DFT based CRDR. The feasibility and effectiveness of the proposed scheme is proved with simulation using collected data obtained from ATP (Alternative Transient Program) package.