• Proceedings of the KIEE Conference
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• summer
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• pp.455-457
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• 2004

An accurate digital distance relaying algorithm which is immune to reactance effect of the fault resistance and the load current for phase-to-phase short fault in 765kV untransposed transmission lines is proposed. The algorithm can estimate adaptively the impedance to a fault point independent of the fault resistance. To compensate the magnitude and phase of the apparent impedance, this algorithm uses the angle of an impedance deviation vector. The impedance correction algorithm for phase-to-phase short fault uses a voltage equation at fault point to compensate the fault current at fault point. A series of tests using EMTP output data in a 765kv untransposed transmission lines have proved the accuracy and effectiveness of the proposed algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.81-88
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• 2013

A low voltage circuit breaker protects electrical equipments from over current and short faults of system by cutting the power supply. The breaker use a thermal magnetic type trip device from the past. In recent years, electronic type relays are applied due to useful functions and services. The purpose of this development is full digitalizing of relay functions of a low voltage breaker. It includes separation of current sensor from current transformer, digital signal processing, high speed relaying, and voltage measuring for power meter. The suggestions are tested and implemented by making prototype and testing its all relay functions.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.717-718
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• 2008

We developed the protection program for the generator fault protection system and each module of the digital protective relay H/W for loading the protection program. The protective algorithm for the generator is 51, 51G/N, 46P/N, 47P/N, 50G/N, and 32, and we developed each fault protection program. And we must design high efficiency microprocessor, CT, and PT for realtime measuring, relaying and high accuracy of measurement, also. From now on digital protective relay must be operated with integrated management systems. For this point, we must load various industrial protocol on the digital protective relay. In this research, we developed each protective relay H/W module according to above conditions. And we designed real-time operating system in order that each protective algorithm is operated with realtime processing on the H/W system.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.137-147
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• 2008

This paper proposes a novel approach to interference avoidance via inter-cell relaying in cellular OFDMA-TDD (orthogonal frequency division multiple access - time division duplex) systems. The proposed scheme, termed asymmetry balancing, is targeted towards next-generation cellular wireless systems which are envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing resolves the detrimental base station (BS)-to-BS interference problem inherent to TDD networks by synchronizing the TDD switching points (SPs) across cells. In order to maintain the flexibility of TDD in serving the asymmetry demands of individual cells, inter-cell relaying is employed. Mobile stations (MSs) in a cell which has a shortage of uplink (UL) resources and spare downlink (DL) resources use free DL resources to off-load UL traffic to cooperating MSs in a neighboring cell using ad hoc communication. In an analogous fashion DL traffic can be balanced. The purpose of this paper is to introduce the asymmetry balancing concept by considering a seven-cell cluster and a single overloaded cell in the center. A mathematical model is developed to quantify the envisaged gains in using asymmetry balancing and is verified via Monte Carlo simulations. It is demonstrated that asymmetry balancing offers great flexibility in UL-DL resource allocation. In addition, results show that a spectral efficiency improvement of more than 100% can be obtained with respect to a case where the TDD SPs are adapted to the cell-specific demands.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.216-218
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• 2001

The transformer role is very important in power system operation and control; also its price is very expensive. Therefore many kinds of the efforts for transformer protection have been executed. So for as, current differential relay(87) has been mainly used for transformer protection. But current differential relaying method has several troubles as followings. Differential current can be occurred by transformers inrush current between winding1 and winding2 of transformer when transformer is initially energized. Also harmonic restrained element used in current differential relaying method is one of the causes of relays mal-operation because recently harmonics in power system gradually increase by power switching devices(SVC, FACTS, DSC, etc). Therefore many kinds of effort have been executed to solve the trouble of current differential relay and one of them is method using ratio of increment of flux linkages(RIFL) of the primary and secondary windings. This paper introduces a novel protective relay for power transformers using RIFL of the primary and secondary windings. Novel protective relay successfully discriminates between transformer internal faults and normal operation conditions including inrush and this paper includes real time test results using RTDS(Real Time Digital Simulator) for novel protective relay. A novel protective relay was designed using the TMS320C32 digital signal processor and consisted of DSP module. A/D converter module, DI/DO module, MMI interface module and LCD display module and developed by Xelpower co., Ltd.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.215-217
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• 2000

Protective relay play a crucial role in the proper operation of a power system, and the reliable transfer of electrical power. This paper deals with the design and implementation of a digital protective relay on a single chip. Implementation on the FPGA(Field Programmable Gate Array) of the chip of digital protective relay. This protective relaying chip monitors the frequency and the voltage and current of the power system. And report the voltage, the current. the frequency, active power and reactive power.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.181-183
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• 2005

The existing distribution networks are growing with an increase of power demand more and more. Therefore, for efficient operation of distribution networks, operators are much in need of distributed generation. This paper describes a development of the digital protection relay(HIMAP) for protecting distributed generation which is expected to play an increasing role in electric power systems in the near future. This paper particularly introduces frequency protective algorithm and reverse power protective algorithm among the relaying algorithms for protecting distributed generation in distribution networks and resents capability of a developed digital protection relay including these algorithms.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.51-53
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• 1994

Recently, advanced digital protection relays were developed in Japan. This improved relaying system for the next generation is expected to have higher performance for the discrimination of the fault, functions for multi-purpose use of acquired data, easy operation and maintance, and also have friendly man-machine interface. This paper describes the system configuration of the developed relay and its representive characteristics.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.444-446
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• 1994

This paper describes the design of a digital multifunction controller for the intelligent high voltage customer switchboard and proposes a relaying algorithm for high impedance faults using back-propagation neural network. The hardware design uses the three microprocessors and global memory architecture to achive real time operation and control 4 feeders. The controller uses a 64-point radix-4 DIF FFT algorithm to measure the harmonic and relay parameters. Synthesized fault current waveforms are used to train and test the back - propagation network.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.276-277
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• 2006

Estimation of power system frequency is an important task because frequency deviation is a good indicator of the system abnormal operating conditions. The algorithms, curve fitting, technique using Taylor series, deviation of phasor angle of fundamental waveform using DFT (Discrete Fourier Transform) and Prony method, are tested under operation of the frequency relaying by using EMTP MODELS. The performance of methods is compared with the simulation results.