• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2278-2288
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• 2017

Multilevel converter topologies are widely used in many applications. The cascaded H-bridge multilevel inverter (CHBMI), which is one of many multilevel converter topologies, has been introduced as a useful topology in high and medium power. However, it has a drawback to require a lot of switches. Therefore, the reliability of CHBMI is important factor for analyzing the performance. This paper presents a simple switch fault diagnosis method for single-phase CHBMI. There are two types of switch faults: open-fault and short-fault. In the open-fault, the body diode of faulty switch provides a freewheeling current path. However, when the short-fault occurs, the distortion of output current is different from that of the open-fault because it has an unavailable freewheeling current flow path due to a disconnection of fuse. The fault diagnosis method is based on the zero current time analysis according to zero-voltage switching states. Using the proposed method, it is possible to detect the location of faulty switch accurately. The PSIM simulation and experimental results show the effectiveness of proposed switch fault diagnosis method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1286-1291
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• 2018

In recent years, the proliferation of DER (distributed energy resources) is progressing rapidly. In particular, research on LVDC distribution grid with various advantages has begun. In order to commercialize this LVDC grid, direct current protection method should be established by analysis of DC faults. Recently, the development of HSCB (high-speed circuit breaker) for new ${\pm}750[V]$ LVDC grid has been researched. This paper deals with the calculation of the maximum short-circuit fault current of the HSCB as a part of the development of HSCB for the LVDC distribution grid. First, modeling using PSCAD was carried out for PV array with BESS on the Gochang Power Test Center system. Next, to calculate the rated capacity of HSCB, fault currents were calculated and the characteristics were analyzed through fault simulations. Thus, this study results can help to establish short-circuit capacity calculation of HSCB and protection plan for DC protection relay system.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.39-43
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• 2019

The breaking of a circuit in DC grid could pose a challenge because of the absence of zero-crossing instant for both current and voltage when a fault occurs. An additional fault current limiting function will be very helpful for reducing the burden of the DC circuit breaker by limiting the fault current to a reasonable value. In this paper, we studied the overcurrent characteristics of several HTS conductors so that we could use the selected conductors for the basic design work of a resistive type fault current limiting module as a part of the circuit breaking system. According to the short-circuit test results, we suggested and compared two different basic design parameters of the HTS fault current limiting module, which will be connected in series to the DC circuit breaker.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.876-880
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• 2013

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The principal factor of the fire is electric arc or spark accompanied with such electric faults. Earth Leakage Circuit Breaker (ELB) and Molded_case Circuit Breaker (MCCB), that is, Residual Current Protective Devices (RCDs) used on low voltage distribution lines cut off earth leakage and overload, but the RCD can not cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied in low voltage distribution panel are prescribed to rated breaking time about 30[ms] (KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To improve such problems, this paper studies on an arc fault circuit interrupter (AFCI) using the distorted voltage wave in electric arc faults. The proposed voltage sensing type AFCI is an electrical fire prevention apparatus of new conception that operates a circuit breaker with sensing the instantaneous voltage drop of line voltage at electrical faults occurrence. The proposed AFCI is composed of control circuit topology using some semiconductor switching devices. Some experimental tests of the proposed AFCI confirm practicality and the validity of the analytical results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2342-2348
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• 2009

Even though underground transmission cable is an essential transmission method to supply stable power for downtown and population center, the interaction of electromagnetic force by fault current is very large comparing to overhead transmission line due to restricted installation space such as tunnel, and close consideration is required for it. This paper presents countermeasures to reduce and release the effect of electromagnetic force with rope binding and installation of spacer and describes its efficacy through three phase short-circuit test, which will be utilized as basic materials for improvement and development of cleat, hanger, etc. to reduce and release effect of electromagnetic force in the future.

• Journal of Magnetics
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• v.20 no.4
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• pp.400-404
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• 2015

Various kinds of winding arrangements can be used to enable fault current limiters (FCL) to tolerate higher forces without resulting in a substantial increase in construction and fabrication costs. In this paper, a distributed winding arrangement is investigated in terms of its effects on the short-circuit forces in a three-phase FCL. The force magnitudes of the AC supplied windings are calculated by employing a finite element-based model in the time stepping procedure. The leakage flux and radial and axial force magnitudes obtained from the simulation are compared to those obtained from a conventional winding arrangement. The comparison shows that the distributed winding arrangement significantly reduces the radial and, especially, the axial force magnitudes.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.115-116
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• 2006

Since the discovery of the high-temperature superconductors, many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means to limit fault current in power systems. The SFCLS, in contrast to current limiting reactors or high impedance transformers, are capable of limiting short circuit currents without adding considerable voltage drop and energy loss to power systems during normal operation. Under fault conditions, a resistance is automatically inserted into the power grid to limit the peak short-circuit current by transition from the superconducting state to the normal state, the quench. The advantages, like fail safe operation and quick recovery, make SFCL very attractive, especially for rapidly growing power systems with higher short-circuit capacities. In order to verify the effectiveness of the SFCL, in this paper, the analysis of fault current and voltage stability assessment in a sample distribution system and a transmission system are performed by the PSCAD/EMTDC based simulation method. Through the simulation, the advantage of SFCL application is shown, and the effective parameters of the SFCL are also recommended for both distribution and transmission systems. A resistive type component of SFCL is adopted in the analysis. The simulation results demonstrate not only the effectiveness of the proposed simulation scheme but also SFCL parameter assessment technique.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.4
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• pp.210-215
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• 2013

This paper analyze the bus voltage sags in the power distribution system with a small scale cogeneration system when the superconducting fault current limiter was introduced. Among the solutions to decrease the short-circuit current considering the locations of the small scale cogeneration system, the superconducting fault current limiter (SFCL) has been announced as one of the promising methods to reduce the fault current because the installation of the small scale cogeneration system which increases the short-circuit current. According to the application locations of the small scale cogeneration system in a power distribution system, it has caused the variations of voltage sag and duration which depends on the change of the short-circuit current, which can make the operation of the protective device deviate from its original set value when the fault occurs. To investigate the voltage sag when a SFCL was applied into a power distribution system where the small scale cogeneration system was introduced into various locations, the SFCL, small scale cogeneration system, and power system are modeled using PSCAD/EMTDC. In this paper, the effects on voltage sags are assessed when the SFCL is installed in power distribution system with various locations of the small scale cogeneration system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1953-1958
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• 2012

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The occurrence factor of the fire is electric arc or spark accompanied with such electric faults, specially short circuit faults. Earth Leakage Circuit Breaker (ELB) and Molded_case Circuit Breaker (MCCB), that is, Residual Current Protective Devices (RCDs) used on low voltage distribution lines cut off earth leakage and overload, but the RCD can not cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied in low voltage distribution panel are prescribed to rated breaking time about 30ms(KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To improve such problem, this paper proposes a prevention apparatus using the line voltage drop of neutral wire and some semiconductor switching devices. Some experimental tests of the proposed apparatus confirm the validity of the analytical results.