• Journal of Power Electronics
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• v.13 no.5
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• pp.909-918
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• 2013

This paper proposes a coordinated control of the reactive power between the STATCOMs (static synchronous compensators) and the grid-side converters (GSC) of wind farms equipped with PMSGs (permanent-magnet synchronous generators), by which the voltage fluctuations at the PCC (point of common coupling) are mitigated in the steady state. In addition, the level of voltage sags is reduced during grid faults. To do this, the GSC and the STATCOM supply reactive power to the grid coordinately, where the GSCs are fully utilized to provide the reactive power for the grid prior to the STATCOM operation. For this, the GSC capability of delivering active and reactive power under variable wind speed conditions is analyzed in detail. In addition, the PCC voltage regulation of the power systems integrated with large wind farms are analyzed for short-term and long-term operations. With this coordinated control scheme, the low power capacity of STATCOMs can be used to achieve the low-voltage ride-through (LVRT) capability of the wind farms during grid faults. The effectiveness of the proposed strategy has been verified by PSCAD/EMTDC simulation results.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.219-221
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• 1999

HVDC(High Voltage Direct Current) transmission system was constructed between Cheju island and mainland Haenam and has been operating commercially since 1998. But research activities in this area are not so much. That is caused by the facts that HVDC is large scale system and it is not so easy to implement and to test. Though such simulation tools as RTDS(Real Time Digital Simulator) and EMTDC can be useful, these have limitations for actual control and protective system design. Therefore scaled-down HVDC model was developed for the purpose of researches at operating technique, control and protection methods. The design of this model was based on real Cheju-Haenam HVDC system. And additionally faults simulator such as ground fault, short-circuit and change of impedance in transmission line is equipped for analysis of these faults. Control system of the model was implemented fully digitally. So it is very easy for the researchers to develope control and protection algorithm and to test the performance.

• Journal of Power Electronics
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• v.16 no.3
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• pp.1097-1109
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• 2016

Fault detection and isolation are related to system monitoring, identifying when a fault has occurred, and determining the type of fault and its location. Fault detection is utilized to determine whether a problem has occurred within a certain channel or area of operation. Fault detection and diagnosis have become increasingly important for many technical processes in the development of safe and efficient advanced systems for supervision. This paper presents an integrated technique for fault diagnosis and classification for open- and short-circuit faults in three-phase inverter circuits. Discrete wavelet transform and principal component analysis are utilized to detect the discontinuity in currents caused by a fault. The features of fault diagnosis are then extracted. A fault dictionary is used to acquire details about transistor faults and the corresponding fault identification. Fault classification is performed with a fuzzy logic system and relevance vector machine (RVM). The proposed model is incorporated with a set of optimization techniques, namely, evolutionary particle swarm optimization (EPSO) and cuckoo search optimization (CSO), to improve fault detection. The combination of optimization techniques with classification techniques is analyzed. Experimental results confirm that the combination of CSO with RVM yields better results than the combinations of CSO with fuzzy logic system, EPSO with RVM, and EPSO with fuzzy logic system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.39-40
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• 2007

The analysis of fault current limiting characteristics according to variation of fault current level in the integrated three-phase flux-lock type superconducting fault current limiter (SFCL), which consisted of three-phase flux-lock reactor wound on an iron core with the same turn's ratio between coil 1 and coil 2 for each single phase, was performed. To analyze the current limiting characteristics of this integrated three-phase flux-lock type SFCL, the short circuit experiments was carried out the various three-phase faults such as the single line-to-ground fault, the double line-to-ground fault, the triple line-to-ground fault. From the experimental results, the fault current limiting characteristic was improved according to increase of fault current level.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.55-59
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• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

• Progress in Superconductivity and Cryogenics
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• v.6 no.3
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• pp.50-55
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• 2004

We fabricated and tested a resistive type superconducting fault current limiter (SFCL) of three-phase 6.6 $kV_{rms}/200 A_{rms}$ rating based on YBCO thin films grown on sapphire substrates with a diameter of 4 inches, Short circuit tests were carried out at a accredited test facility for single line-to- ground faults, phase-to-phase faults and three-phase faults, Each phase of the SFCL was composed of 8${\times}$6 elements connected in series and parallel respectively. Each element was designed to have the rated voltage of 600 $V_{rms}$. A NiCr shunt resistor of 23 Ω was connected to each element for simultaneous quenches. Firstly, single phase-to-ground fault tests were carried out. The SFCL successfully developed the impedance in the circuit within 0.12 msec after fault and controlled the fault current of 10 $kA_{rms} below 816 A_{peak}$ at the first half cycle. In addition, in case of phase-to-phase fault and three- phase fault test. simultaneous quenches among the SFCLs of the phases successfully accomplished. In conclusion. the SFCL showed excellent performance of current limitation upon fault and stable operation regardless of the amplitude of fault currents.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.3
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• pp.52-58
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• 2008

The importance of. identifying the causes of electrical faults cannot be overstated because of the accidents caused by over-current that take place at the home, the office and electrical facilities due to misuse, poor products and system faults. It is necessary to gather objective, scientific data pertaining to electrical fault investigation in a product liability(PL) environment. To date, no database(DB) has been built concerning the accurate cause analysis of faultyfacilities. In this paper, accident hazard and arc scattering when over-current flows in copper wire was investigated. It was found that when over-current flows in a copper wire, the copper wire became heated and bent and beads were scattered around the wire with a flash. It was determinedthat the fusing current and time was related to the current rise per second. For example, when the current rise per second was largethe fusing current was higher than when the current rise per second was small, and the beads dispersed along a wide area. Fusing time, however, was shorter. The possibility of electrical fault became highest when the fusing current was higher. As the current rise per second is short, the dendrite structure is distributed in the surface of the copper wire. These experimental results can be utilized for a fault process DB system in the investigation and the prevention of electrical faults.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1810-1816
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• 2009

In 2007, 9,128 fires were actually caused by electrical faults and these fires resulted in 29 deaths and 262 injuries. Arc-faults were one of the major causes of these fires. When an unintended arc-fault occurs, it generates intense heat that can easily ignite surrounding combustibles. But, because conventional circuit breakers only respond to overloads, short circuits, and leakage currents, the breakers do not protect against arcing conditions. This paper presents results obtained in experiments on ignition behavior of wire by series arc fault currents and techniques developed to detect the arc-faults. The developed technique was tested after installation to make sure that they are working properly and protecting the circuit. If the developed arc fault detection technique is applied, the electrical fires caused by an arc-fault can be reduced.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.643-652
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• 2021

Accidents or faults in the transmission and distribution system are never completely avoidable, and short-circuit and earth faults are occurs despite the efforts of the TSO and DSO. Recently, the connection to the transmission and distribution system of large-capacity new and renewable distributed power has increased rapidly and has various effects on the operation of the system. In order to minimize this, connection standards such as FRT (Fault-Ride-Through) have been established to provide wind turbines or solar inverters. In the event of a major faults of the power system, the operation support shall be provided so that the operator can stably operate the system by smoothly performing connection maintenance or rapid system separation. In this paper, in order to appropriately determine whether the FRT condition, which is the grid connection criterion for a representative DERs, is sufficient, a detection system using a PMU (Phasor Measurement Unit) that measures a synchro-phasors was designed and deployment and a system accident due to a generator step-out to analyze and evaluate the proposed system based on the case.

• Fire Science and Engineering
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• v.16 no.3
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• pp.8-11
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• 2002

Recently, the spark and the overheat due to in the failure of pressure contacts on connecting points and the momentary short circuit have been the major causes of electrical fire because these may cause the deposition and the graphite of insulating materials in electrical wiring system. Also, because in these cases the current is a surge one, the losses and faults of a communication, a home appliances, a computer and a measuring instrument may occur. Especially, in such cases, we are very difficult to detect the failure of pressure contacts on connecting points and the momentary short circuit. In this paper, we have developed an auxiliary control device, the electrical fire prevention control device(EFPCD), of an earth leakage breaker(ELB). And we can pre-vent the electrical fire caused by the spark and the overheat occurring in the failure of pressure contacts in connecting points and the momentary short circuit with the EFPCD.