• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.949-951
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• 1998

Because of the zero sequence mutual coupling of parallel lines, the distance calculation performed by a distance relay is incorrect. To achieve correct operation, the relay has to use not only the measured quantities of faulty line, but also the zero sequence current of healthy line. But the zero sequence current of the healthy line cannot be always measured. Therefore, we propose the neural network method to estimate the zero sequence current and the criterion to determine whether faulty line or not.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.109-111
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• 1996

This paper describes real time dynamic tests on the digital distance relay using new digital test system including RTDS(Real Time Digital Simulator) in KEPRI. The RTDS is developed by the Manitoba HVDC Reserch Centre and consists of specialized hardware and software which allows transients simulation of electrical power systems in real time. From high impedance fault test, it is known that the characteritics of distance reach is influenced by load flow. A detailed discussion of relay test using the RTDS simulator, high impedance faults and test results are included in the paper.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.4
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• pp.617-627
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• 2013

Wireless communication technology such as NFC and RFID makes the data transfer between devices much easier. Instead of the irksome typing of passwords, users are able to simply authenticate themselves with their smart cards or smartphones. Relay attack, however, threatens the security of token-based, something-you-have authentication recently. It efficiently attacks the authentication system even if the system has secure channels, and moreover it is easy to deploy. Distance bounding or localization of two devices has been proposed to detect relay attacks. We describe the disadvantages and weakness of existing methods and propose a new way to detect relay attacks by recording a background noise.

• Proceedings of the Korea Society for Simulation Conference
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• 2005.05a
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• pp.5-9
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• 2005

One of the imminent problems to be solved within wireless sensor network is to balance out energy dissipation among deployed sensor nodes. In this paper, we present a transmission relay method of communications between BS (Base Station) and CHs (Cluster Heads) for balancing the energy consumption and extending the average lifetime of sensor nodes by the fuzzy logic application. The proposed method is designed based on LEACH protocol. The area deployed by sensor nodes is divided into two groups based on distance from BS to the nodes. RCH (Relay Cluster Head) relays transmissions from CH to BS if the CH is in the area far away from BS in order to reduce the energy consumption. RCH decides whether to relay the transmissions based on the threshold distance value that is obtained as a output of fuzzy logic system. Our simulation result shows that the application of fuzzy logic Provides the better balancing of energy depletion and Prolonged lifetime of the nodes.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.4
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• pp.221-226
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• 2004

Power system has recently used Double-circuit Line and Multi-circuit Line in the industrial development. This has an advantage of system stability and reliability, but the complexity of the system has a disadvantage that makes it difficult to protect the power line. Double-circuit Line has two operation conditions in the Single-circuit operation and Double-circuit operation, so it has mutual impedance. To make it possible for the remaining single-line to operate independently while there is a fault with first line or when maintenance is needed, a trip region for the single-circuit operation should be set in order to set the relay trip region. An optimal trip region for each operation, a different operational conditions for the relay setting should be calculated. In this paper, trip regions of each operation condition have been compared by considering mutual impedance and fault resistance that led to the calculation of fault impedance. Also, as we know that one of the advantages in the distance relay is the back-up protection, we calculated the trip region(Zone-2) in consideration of the mutual impedance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.4
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• pp.221-221
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• 2004

Power system has recently used Double-circuit Line and Multi-circuit Line in the industrial development. This has an advantage of system stability and reliability, but the complexity of the system has a disadvantage that makes it difficult to protect the power line. Double-circuit Line has two operation conditions in the Single-circuit operation and Double-circuit operation, so it has mutual impedance. To make it possible for the remaining single-line to operate independently while there is a fault with first line or when maintenance is needed, a trip region for the single-circuit operation should be set in order to set the relay trip region. An optimal trip region for each operation, a different operational conditions for the relay setting should be calculated. In this paper, trip regions of each operation condition have been compared by considering mutual impedance and fault resistance that led to the calculation of fault impedance. Also, as we know that one of the advantages in the distance relay is the back-up protection, we calculated the trip region(Zone-2) in consideration of the mutual impedance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1350-1359
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• 2010

Recently many researchers have been proved that general RFID system for proximity authentication is vulnerable to various location-based relay attacks such as distance fraud, mafia fraud and terrorist fraud attacks. The distance-bounding protocol is used to prevent the relay attacks by measuring the round trip time of single challenge-response bit. In 2008, Munilla and Peinado proposed an improved distance-bounding protocol applying void-challenge technique based on Hancke-Kuhn's protocol. Compare with Hancke-Kuhn's protocol, Munilla and Peinado's protocol is more secure because the success probability of an adversary has (5/8)n. However, Munilla and Peinado's protocol is inefficient for low-cost passive RFID tags because it requires large storage space and many hash function computations. Thus, this paper proposes a new RFID distance-bounding protocol for low-cost passive RFID tags that can be reduced the storage space and hash function computations. As a result, the proposed distance-bounding protocol not only can provide both storage space efficiency and computational efficiency, but also can provide strong security against the relay attacks because the adversary's success probability can be reduced by $(5/8)^n$.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.1-9
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• 2010

This paper summarizes an education and training system for the auto-reclosing of power transmission system using a real time digital simulator. The system is developed to understand the principle of reclosing and the sequence of automatic reclosing schemes, and practice the effects of reclosing actions to power system in real-time simulator. This study is concentrated into the following two parts. One is the development of real time education and training system of automatic reclosing schemes. For this, we use the RTDS(real time digital simulator) and the actual digital protective relay. The mathematical relay model of RTDS and the actual distance relay which is equipped automatic reclosing function are also used. The other is the user friendly interface between trainee and trainer. The various interface displays are used for user handing and result display. The conditions of automatic reclosing which is a number of reclosing, reclosing dead time, reset time, and so on, can be changed by the user interface panel. A number of scenario cases are reserved for the education and training. Through the test, we verified that the proposed system can be effectively used to accomplish the education and training of automatic reclosing.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.383-386
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• 2001

Distance relay is tripped by the line impedance calculated at the relay point. Accordingly the accurate operation depends on the precise calculation of line impedance. 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 cable cover protection units (CCPUs). There are also several grounding systems in cable systems. Therefore, if there is a fault in cable system, these terms will severely be caused much error to calculation of impedance. Accordingly the proper compensation should be developed for the correct operation of the distance relay. This paper presents the distance calculating algorithm in combined transmission line with power cable using wavelet transform. In order to achieve such purpose, judgement method to discriminate the fault section in both sections was proposed using db1 coefficient summation. And also, error compensation factor was proposed for correct calculation of impedance in power cable.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.37-44
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• 2004

This paper represents a new approach for the protective relay of power transmission lines using a Artificial Neural Network(ANN). A different fault m transmission lines need to be detected classified and located accurately and cleared as fast as possible. However, The protection range of the distance relay is always designed on the basis of fixed settings, and unfortunately these approach do not have the ability to adapt dynamically to the system operating condition. ANN is suitable for the adaptive relaying and the detection of complex faults. The backpropagation algerian based multi-layer protection is utilized for the teaming process. It allows to make control to various protection functions. As expected, the simulation result demonstrate that this approach is useful and satisfactory.