• Progress in Superconductivity
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• v.10 no.1
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• pp.60-67
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• 2008

We present domestic efforts for superconducting fault current limiter (SFCL) application in the Korea Electric Power Corporation (KEPCO) grid and pending points at issue. KEPCO's decision to upgrade the 154 kV/22.9 kV main transformer from 60 MVA to 100 MVA cast a problem of high fault current in the 22.9 kV distribution lines. The grid planners supported adopting an SFCL to control the fault current. This environment friendly to SFCL application must be highly dependent upon the successful development of SFCL having specifications that domestic utility required. The required conditions are (1) small size of not greater than twice of 22.9 kV gas insulated switch-gear (GIS), (2) sustainability of current limitation without the line breaking by circuit breakers (CB) for maximum 1.5 seconds. Also, optionally, recommended is (3) the reclosing capability. Conventional resistive SFCLs do not meet (1) $\sim$ (3) all together. A hybrid SFCL is an excellent solution to meet the conditions. The hybrid SFCL consists of HTS SFCL components for fault detection and line commutation, a fast switch (FS) to break the primary path, and a limiter. This characteristic structure not only enables excellent current limiting performances and the reclosing capability, but also allows drastic reduction of HTS volume and small size of the cryostat, resulting in economic feasibility and compactness of the equipment. External current limiter also enables long term limitation since it is far less sensitive to heat generation than HTS. Semi-active operation is another advantage of the hybrid structure. We will discuss more pending points at issues such as maintenance-free long term operation, small size to accommodate the in-house substation, passive and active control, back-up plans, diagnosis, and so on.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.94-105
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• 2010

To detect faults in an inverter-fed permanent magnet synchronous motor (PMSM) drive under the circumstance having faults in a stator winding and inverter switch, an on-line basis fault detecting scheme during operation is presented. The proposed scheme is achieved by monitoring the second-order harmonic component in q-axis current and the fault is detected by comparing these components with those in normal conditions. The linear interpolation method is employed to determine the harmonic data in normal operating conditions. As soon as the fault is detected, the operating mode is changed to identify a fault type using the phase current waveform. To verify the effectiveness of the proposed fault detecting scheme, a test motor to allow inter-turn short in the stator winding has been built. The entire control algorithm is implemented using DSP TMS320F28335. Without requiring an additional hardware, the fault can be effectively detected by the proposed scheme during operation so long as the steady-state condition is satisfied.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.18-28
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• 2009

To analyze influences under faults caused by a stator winding short and to evaluate an effectiveness of a diagnostic algorithm a faulty model for an inverter-driven permanent magnet synchronous motor is presented. Even though the conventional dq motor model obtained through the transformation of phase voltage model is widely used to analyze and control the motor, it can not be used in the analysis of a faulty motor since the 3-phase balanced condition is no longer hold under the fault caused by a stator winding short, and thus, it is very difficult to obtain motor input voltages from the pole voltage of an inverter. To overcome this problem, a faulty model for an inverter-driven permanent magnet synchronous motor is proposed by considering the line voltage of 3-phase variables. The effectiveness of the proposed faulty model is verified through comparative simulations and experiments using DSP TMS320F28335 and motor built to allow a partial short of inter-turn.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.148-163
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• 2021

Timely fault identification is important for safe and reliable operation of the electric valve system. Many research works have utilized different data-driven approach for fault diagnosis in complex systems. However, they do not consider specific characteristics of critical control components such as electric valves. This work presents an integrated shallow-deep fault diagnostic model, developed based on signals extracted from DN50 electric valve. First, the local optimal issue of particle swarm optimization algorithm is solved by optimizing the weight search capability, the particle speed, and position update strategy. Then, to develop a shallow diagnostic model, the modified particle swarm algorithm is combined with support vector machine to form a hybrid improved particle swarm-support vector machine (IPs-SVM). To decouple the influence of the background noise, the wavelet packet transform method is used to reconstruct the vibration signal. Thereafter, the IPs-SVM is used to classify phase imbalance and damaged valve faults, and the performance was evaluated against other models developed using the conventional SVM and particle swarm optimized SVM. Secondly, three different deep belief network (DBN) models are developed, using different acoustic signal structures: raw signal, wavelet transformed signal and time-series (sequential) signal. The models are developed to estimate internal leakage sizes in the electric valve. The predictive performance of the DBN and the evaluation results of the proposed IPs-SVM are also presented in this paper.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.258-260
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• 1993

This paper presents an on-line monitoring and control system designed for the automation of a Concrete plant. The system is based on the combined structure composed of a general purpose PLC (Plogrammable Logic Controller) and a personal computer. Simulation results are ahem to illustrate the system operation. Preconstructed rules are applied to the plant data for the diagnosis of the weighing process in the simulation.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.16 no.4
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• pp.238-245
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• 2016

Inverters are considered the basic building blocks of industrial electrical drive systems that are widely used for various applications; however, the failure of electronic switches mainly affects the constancy of these inverters. For safe and reliable operation of an electrical drive system, faults in power electronic switches must be detected by an efficient system that is capable of identifying the type of faults. In this paper, an open switch fault identification technique for a three-phase inverter is presented. Single, double, and triple switching faults can be diagnosed using this method. The detection mechanism is based on stator current analysis. Discrete wavelet transform (DWT) using Daubechies is performed on the Clarke transformed (-) stator current and features are extracted from the wavelets. An artificial neural network is then used for the detection and identification of faults. To prove the feasibility of this method, a Simulink model of the DWT-based feature extraction scheme using a neural network for the proposed fault detection system in a three-phase inverter with an induction motor is briefly discussed with simulation results. The simulation results show that the designed system can detect faults quite efficiently, with the ability to differentiate between single and multiple switching faults.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.5
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• pp.457-465
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• 2011

The fault analysis and detecting algorithm for a 3 phase diode rectifier is proposed. The 3 phase dioderectifier is used for the AC power rectifier of the PWM inverter. The input power or diode faults cause theripples of the DC voltage, degradation of the control performance and life shortening of the DC link capacitor.In this paper, the ripple of the DC voltage is mathematically analyzed for the earth fault of input power andopen circuit fault of the diode, respectively. The fault detection and type of fault can be obtained by comparingthe average DC voltage and the instant DC voltage which is sampled with 6 times of grid frequency. Theproposed method can be easily applicable and doesn't require additional circuit. The experimental and simulationresults are presented to verify the validity of the proposed method.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.56-61
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• 2010

Simulator is a development equipment which enables the ECU to operate in normal mode by simulating the interface signal between ECU and mechanical system electrically. Embedded simulator means simulation function is embedded in ECU firmware, hence the electrical signal interface is replaced by the substitution of information at system program level. This paper explains the development of embedded transmission simulator for the verification of TCU firmware function which covers shifting control and on-board diagnosis. The embedded simulation program is executed in TCU processor along with the TCU firmware and it provides TCU firmware with not only the speed information those are appropriate both in driving and shifting conditions, but also the fault detection signals. Experimental results show that the validity of embedded simulator and its usefulness to the TCU firmware development and verification.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.2
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• pp.38-44
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• 1998

This paper presents an integrated fault diagnosis expert system to assist SCADA operators in local control centers which controls unmanned distribution substations in a power system. The proposed system diagnoses various faults occurred in both substation devices and transmission devices. The system can be easily installed without disturbing main SCADA system. The system simply shares the dynamic information including alarms with main SCADA using dual data link interface. And the proposed expert system utilizes the fuzzy reasoning process in order to consider the uncertainty factor. The system is developed using a low cost personal computer owing to the special modular programming and the meta-inf!'lrence structure. Case studies showed a promising possibility.bility.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.7
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• pp.868-875
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• 1999

In this paper, digital motor control center using protection relay is developed in order to protect power systems by means of timely fault detection and diagnosis during operation for induction motor which have various load environments and capacities in power systems. Digital motor control center is employed by power supervisory control systems without separate remote terminal unit and transducers adding communicational ability. Also we develope a maximum demand controller to control the load effectively at peak status and a power factor controller to minimize real power losses and improve the power factor. Therefore, when using the developed controller, real time computation is possible by loading DSP in hardware and applying real-time kernel which can convert each algorithm to task module.