• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1817-1819
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• 2001

For an efficient calculation of scattering matrix of planar transmission line with step discontinuity. Mode Matching Method combined with Vector Finite Element Method is adopted. Calculating effective widths are replaced with their respective equivalent planar waveguide corresponding to the microstrip width, Propagation Constant is calculated from the Vector finite element. Mode matching method is used for deriving scattering parameters.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.1
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• pp.38-44
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• 2001

For double-circuit transmission line systems, an accurate digital distance relaying algorithm immune to the reactance effect is proposed. The apparent impedance calculated by the distance relay is influenced by the combined reactance effect of the fault resistance and the load current as well as the mutual coupling effect caused by the zero-sequence current of the adjacent parallel circuit. To compensate the magnitude and phase of the estimated impedance, this algorithm uses phase angle difference between the zero(positive) sequence of the both side of the system seperated by the fault point. The impedance measuring algorithm presented used a current distribution factor to compensate mutual coupling effect instead of the collected zero-sequence current of the adjacent parallel circuit.

• The Journal of Information Technology
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• v.6 no.4
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• pp.1-9
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• 2003

This paper is about power line communication(PLC) over the low power voltage grid. The main advantage with power line communication is the use of an existing infrastructure. The PLC channel can be modeled as having multi-path propagation with frequency-selective fading, typical power lines exhibit signal attenuation increasing with length and frequency. OFDM(Orthogonal Frequency Division Multiplexing) is a modulation technique where multiple low data rate carriers are combined by a transmitter to form a composite high data rate transmission. The performance in consideration of the multi-path(echoes) powerline scheme is analyzed and verified by computer simulation.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.205-207
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• 2003

The line impedance is important data that is applied in all analysis fields of electric power system like power flow, fault current, stability and relay calculation etc. Usually, impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and earth resistance. Therefore, if there is a fault in cable system, these terms will severely be caused much error to calculation of impedance. Therefore, the line impedance were measured for this study in an actual power system of underground cables, and were analyzed by a generalized circuit analysis program EMTP for comparison with the measured value. These analysis result is considered to become foundation of impedance calculation for underground cable.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.612-613
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• 2007

The line impedance is important data that are applied in all analysis fields of electric power system such as power flow, fault current, stability and relay calculation etc. Usually, the impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, the impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and earth resistances. Therefore, if there is a fault in cable system, these terms will severely be caused many errors for calculating impedance. In this paper, the line impedance is measured in a power system of underground cables, and is analyzed by a generalized circuit analysis program, EMTP(Electromagnetic Transient Program), for comparison with the measured value. These analysis results are considered to become foundation of impedance calculation for underground cables.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.2
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• pp.102-108
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• 2002

This paper describes the overvoltage analysis and reduction methods of insulation joint boxes in underground transmission power cables when direct lightning surge strikes to overhead transmission line. An actual 154kV combined transmission line with underground Power cables was modelled in ATPDraw for simulation. Simulations were performed to analyze the overvoltage between insulation joint boxes, sheath-to-ground voltage according to the distance between cable conductors, cable lengths, burying types, CCPU connection types. The most effective method to reduce the induced overvoltage of Insulation joint boxes was proposed. It is evaluated that the proposed reduction method riven from the detailed simulations can be effectively applied to the actual underground power cable systems.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.252-254
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• 2001

Accurate detection and classification of faults on transmission lines is vitally important. High impedance faults(HIF) in particular pose difficulties for the commonly employed conventional overcurrent and distance relays, and if not detected, can cause damage to expensive equipment, threaten life and cause fire hazards. Although HIFs are far less common than LIFs, it is imperative that any protection device should be able to satisfactorily deal with both HIFs and LIFs. This paper proposes an algorithm for fault detection and classification for both LIFs and HIFs using Adaptive Network-based Fuzzy Inference System(ANFIS). The performance of the proposed algorithm is tested on a typical 154[kV] Korean transmission line system under various fault conditions. Test results show that the ANFIS can detect and classify faults including (LIFs and HIFs) accurately within half a cycle.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.9
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• pp.417-423
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• 2001

This paper proposes a technique for fault detection and classification for both LIF(Low Impedance Fault)s and HIF(High Impedance Fault)s using Adaptive Network-based Fuzzy Inference System(ANFIS). The inputs into ANFIS are current signals only based on Root-Mean-Square(RMS) values of 3-phase currents and zero sequence current. The performance of the proposed technique is tested on a typical 154 kV Korean transmission line system under various fault conditions. Test results show that the ANFIS can detect and classily faults including (LIFs and HIFs) accurately within half a cycle.

• International journal of advanced smart convergence
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• v.11 no.4
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• pp.41-46
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• 2022

This study is a Ku-band array antenna for the manufacture of low-orbit satellite communication terminals, designed to have miniaturization, high gain, and wide beam width. The transmission of low-orbit satellite communication has a right-rotating circularly polarized wave, and the reception has a left-rotating circularly polarized wave. The 4×8 array antenna was separated for transmission and reception, and it was combined with the RF circuit part of the transmitter and receiver, and was terminated in the form of a waveguide for RF signal impedance matching in the form of a transition from the microstrip line to the waveguide. The 30° beam width of the receiver maximum gain of 19 dBi and the 29° beam width of the transmitter maximum gain of 18 dBi are shown. Through this antenna configuration, the system was configured to suit the low-orbit satellite transmission/reception characteristics.

• Journal of Power Electronics
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• v.11 no.5
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• pp.734-742
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• 2011

In this paper a robust method is presented for the combined design of STATCOM and Power System Stabilizer (PSS) controllers in order to enhance the damping of the low frequency oscillations in power systems. The combined design problems among PSS and STATCOM internal ac and dc voltage controllers has been taken into consideration. The equations that describe the proposed system have been linearized and a Fuzzy Logic Controller (FLC) has been designed for the PSS. Then, the Particle Swarm Optimization technique (PSO) which has a strong ability to find the most optimistic results is employed to search for the optimal STATCOM controller parameters. The proposed controllers are evaluated on a single machine infinite bus power system with the STATCOM installed in the midpoint of the transmission line. The results analysis reveals that the combined design has an excellent capability in damping a power system's low frequency oscillations, and that it greatly enhances the dynamic stability of power systems. Moreover, a system performance analysis under different operating conditions and some performance indices studies show the effectiveness of the combined design.