• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.375-380
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• 2004

This paper presents the basic quench protection idea for the HTS(High-Temperature Superconducting) cable. In Korea power system, the transfer capability of transmission line is limited by the voltage stability, and HTS cable could be one of the countermeasure to solve the transfer limit as its higher current capacity and lower impedance[1]. However, the quench characteristic of HTS cable makes HTS cable to loss its superconductivity, and therefore change the impedance of the line and power system operating condition dramatically. This pheonominum threats not only HTS cable safety but also power system security, therefore a proper protection scheme and security control counterplan have to be established before HTS cable implementation. In this paper, the quench characteristics of HTS cable for the fault current based on heat balance equation was established and a proper protection method by FCL(Fault Current Limiter) was suggested.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.266_267
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• 2009

22.9kV HTS(High Temperature Superconducting) cable and SFCL(Superconducting Fault Current Limiter) will be installed to Icheon 154kV substation for real distribution power system operation in 2010. This paper proposes CLR (Current Limiting Resistance) specification of the SFCL and fault current condition fo the HTS cable for applying to Korean power system.

• 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 Electrical Engineering and Technology
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• v.12 no.5
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• pp.1697-1708
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• 2017

This paper proposes an algorithm for the differential protection of an Indirect Symmetrical Phase Shift Transformer (ISPST) by considering the different behaviors of the compensated differential current under internal fault and magnetizing inrush conditions. In this algorithm, a criterion function is defined which is based on the difference of amplitude of the wavelet transformation over a specific frequency band. The function has been used for the discrimination between three phase magnetizing inrush and internal fault condition and requires less than a quarter cycle after disturbance. This method is independent of any coefficient or threshold values of wavelet transformation. The merit of this algorithm is demonstrated by the simulation of different faults in series and excitation unit and magnetizing inrush with varying switching conditions on ISPST using PSCAD/EMTDC. Due to unavailability of in-field large interconnected transformers for such a large number of destructive tests, the results are further verified by Real Time Digital Simulator (RSCAD/RTDS). The proposed algorithm has been compared with the conventional harmonic restraint based method that justifies the application of wavelet transform for differential protection of ISPST. The proposed algorithm has also been verified for different rating of ISPSTs and satisfactory results were obtained.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.43.1-43.1
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• 2011

The detail simulation modeling of fully-fed induction generator is investigated through PC based MATLAB/Simulink environment. Generator's stator currents are controlled by indirect vector control method. In this method, generator side converter controls the maximum excitation (air gap flux) by stator d-axis current and controls generator torque by stator q-axis current. Induction generator speed is controlled by tip speed ratio (TSR) upon the wind speed variations in order to generate the maximum output power. The generator torque model is specified as a 3-blade wind turbine with rating, then, the model is simulated under normal operating condition and three different fault conditions. The matlab model designed for fully-fed induction generator based wind farm provides good performance under normal and grid fault conditions. It provides good results for different pwm techniques and fault conditions except the single-phase line to ground fault, which should be verified with real time data from wind farms.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2658-2660
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• 2005

This paper presents a stator winding fault diagnosis technique of induction motor on the PC - based virtual instrumentation system designed using the graphical programming language LabVIEW. This method collects the 3-phase current signals using the current probe amplifier and PXI/DAQ system then the preprocessing removes the noise using LPF, after then this method transforms the stator current to Park's vector and obtains the each Park's Vector pattern and detects stator winding fault by comparing the obtained faulted pattern with the healthy pattern. This proposed LabVIEW based diagnosis system is applied to the 3 phase 1 hp induction motor and obtained the reasonable results under no load condition. The test results give us the possibility a simple and realistic on-line winding fault diagnosis system.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.736-741
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• 2005

This paper presents electric characteristics analysis and safe configuration for extension power supply between existent 6.6kV ungrounded distribution system and establishment and improvement 22.9kV direct grounding distribution system. For this, we model 6.6kV ungrounded and 22.9kV direct grounding distribution system of urban underground, ground region. and rural electrical, unelectrical region using PSCAD/EMTDC and analyze voltage drop, charging current, ground and short fault through simulation. To analyze electric characteristics of extension power supply, we simulate extension power supply of overhead line of 6.6kV ungrounded system and underground line of 22.9kV direct grounding system of rural electrical region and propose operation condition for safe extension power supply through result of analysis. Characteristics of voltage drop, charging current, ground and short fault appear almost similarly with electrical characteristic of direct power supply. However, because unbalance of phases may cause relay's malfunction of ungrounded system and ground fault current of direct grounding system may demage facilities of ungrounded system, we propose safe system configuration such as impedance grounding system of neutral point.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.5
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• pp.195-201
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• 2006

Tower footing resistance and fault current division factor are important design factors for evaluation of the lightning performance of the transmission line and/or design of the grounding electrode system. The periodic measurement of those factors are also important to verify that the grounding performance of the towers has been maintained good. However, the direct measurement of those factors in operating or energized condition is very difficult because of many practical reasons, such as the difficulty of disconnecting overhead groundwires from the tower under test. With supports by GECOL (General Electricitiy Company of Libya), we had a special chance to conduct Fall-Of-Potential (FOP) test on the energized 220 kV transmission towers before and after disconnecting the overhead groundwires from the towers under test. In this paper, the FOP test results on the towers and the fault current division factors estimated from the comparision of the FOP tests with and without overhead groundwires were presented. The computer models for the FOP test simulations were also constructed to find that the simulated results agreed very well with the measured ones.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.559-568
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• 2014

Induction motors are critical components in industrial processes since their failure usually lead to an unexpected interruption at the industrial plant. The studies of induction motor behavior during abnormal conditions and the possibility to diagnose different types of faults have been a challenging topic for many electrical machine researchers. In this regard, an efficient and new method to detect the induction motor-fault may be the application of the Time Synchronous Averaging (TSA) to the stator current Park's Vector. The aim of this paper is to present a methodology by which defects in a three-phase wound rotor induction motor can be diagnosed. By exploiting the cyclostationarity characteristics of electrical signals, the TSA method is applied to the stator current Park's Vector, allowing the monitoring of the induction motor operation. Simulation and experimental results are presented in order to show the effectiveness of the proposed method. The obtained results are largely satisfactory, indicating a promising industrial application of the hybrid Park's Vector-TSA approach.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.941-942
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• 2007

The superconducting fault current limiter (SFCL) consists of superconducting coil for limiting the fault current and cryogenic cooling system for keeping the coil in superconducting condition. The study on the insulation design for superconducting coil and cryogenic cooling system should be elaborately performed to develop a high voltage SFCL. In this paper, insulation design of solenoid coil for 13.2kV/630A SFCL is performed through the AC dielectric breakdown test and lightning impulse dielectric strength test. The dependence of dielectric characteristics on the magnitude of liquid nitrogen pressure is also investigated. Through the investigation, it is verified that dielectric characteristics of sub-cooled nitrogen are strongly enhanced by the pressurization. The electrical insulation design of 13.2kV/630A SFCL is performed by applying the experimental results. The successful insulation design for development of 13.2kV/630A SFCL is confirmed by AC dielectric breakdown tests.