• Proceedings of the KIEE Conference
• /
• 1999.11b
• /
• pp.110-112
• /
• 1999

Recently the substation automation is actively researched at each country. Since the substation automation is an integrated system that consist of electrical, electronic and computer technologies, performance evaluation is very important to inspect the developed system's applicable possibility for real power system. Most studies are verified using computer simulation, because it is hard to apply them to real power systems. Therefore development of a substation simulator is necessary for the performance evaluation of many application systems such as operator aid system. This paper introduces a substation simulator. An intelligent fault diagnosis and restorative control expert system is also introduced UDP/IP is applied as a protocol for data transport between expert system and SC(station computer). As to the Graphic User Interface, C++ Language and Visual Basic is used in the Windows NT operating system together with four Pentium II systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05b
• /
• pp.20-23
• /
• 2003

The operational characteristics of flux-lock type high-Tc superconducting fault currentlimiters(HTSC-FCLs) was described and currents equation at each coil was derived from equivalent circuit. $YBa_{2}Cu_{3}O_{7-x}$(YBCO) thin film was used as the current limiting elements of the flux-lock type HTSC-FCL, which were fabricated by etching the YBCO thin film into 2 mm wide and 420 mm long meander line consisting of foureen stripes with different length. The 2nd peak on the current of coil 2 after a fault disappeared by current of the 3rd winding, which was installed in the flux-lock type HTSC-FCL.

• Proceedings of the KIEE Conference
• /
• 1997.07c
• /
• pp.891-893
• /
• 1997

In this paper an intelligent power transformer protective relaying algorithm based on Fuzzy Decision-Making is presented. The introduced protection algorithm contains several internal fuzzy rule-bases including bpa(Basic Probability Assignment: m) which are subject to off-line pre-installation by the analysis of the transformer transient characteristics for detecting the internal fault. Dempster-Shafer's rule of combination is used for the inference method with rules to decide the situation of a transformer, The proposed algorithm immunes to the saturation of transformer, inrush conditions, over excitation, and external fault. The included results of testing show practically sufficient sensitivity and selectivity of the proposed algorithm.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.2
• /
• pp.138-143
• /
• 2005

During faults, the voltage and current signals available to the relay are affected by the decaying dc component and harmonics. In order to make appropriate and accurate decisions, most of the relaying algorithms require the fundamental frequency phasor information that is immune to decaying dc effect and harmonics. The conventional Fourier ph as or estimation algorithm is affected by the presence of decaying-exponential transients in the fault signal. This paper presents a modified Fourier algorithm, which effectively eliminates the decaying dc component and the harmonics present in the fault signal. The decaying dc parameters are estimated by means of an out-of-band filtering technique. The decaying dc offset and harmonics are removed by means of a simple computational procedure that involves the design of two sets of Orthogonal digital OFT filters tuned at different frequencies and by creating three off-line look-up tables. The technique was tested for different decay rates of the decaying dc component. It was also compared with the conventional mimic plus the full cycle OFT algorithm. The results indicate that the proposed technique has a faster convergence to the desired value compared to the conventional mimic plus OFT algorithms over a wide range of decay rates. In all cases, the convergence to the desired value was achieved within one cycle of the power system frequency.

• The Transactions of the Korea Information Processing Society
• /
• v.2 no.3
• /
• pp.425-432
• /
• 1995

In this paper we propose a design and implementation technique of a universal automatic test pattern generator(UATPG) which is well suited for VLSI digital circuits. UATPG is designed to extend the capabilities of the existing APTG and to provide a convenient environment to computer-aided design(CAD) users. We employ heuristic techniques in line justification and fault propagation for functional gates during test pattern generation for a target fault. In addition, the flip-flops associated with design for testability (DFT) are exploited for pseudo PIs and pseudo POs to enhance the testabilities of VLSI circuits. As a result, UATPG shows a good enhancement in convenient usage and performance.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.15 no.2
• /
• pp.111-120
• /
• 2012

Built-In-Test is a design feature in more and more advanced weapon system. During development test and evaluation(DT&E) it is critical that the BIT system be evaluated. The BIT system is an integral part of the weapon system and subsystem. Built-In-Test assists in conducting on system and subsystem failure detection and isolation to the Line Replaceable Unit(LRU). This capability reduces the need for highly skilled personnel and special test equipment at organizational level, and reduces maintenance down-time of system by shortening Total Corrective Maintenance Time. During DT&E of weapon system the objective of BIT system evaluation is to determine BIT capabilities achieved and to identify deficiencies in the BIT system. As a result corrective actions are implemented while the system is still in development. Through the use of the reiterative BIT evaluation the BIT system design was corrected, improved, or updated, as the BIT system matured.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.54 no.12
• /
• pp.592-596
• /
• 2005

Recently, substations have been constructed in GIS (Gas Insulated Switchgear) and indoor type because of the increasing difficulties of securing locations. In case of urban substations, it is also common that the substations are exclusively fed by underground cables. Sometimes, the infrastructures in urban area, such as communication facilities, are located near substations to be constructed. In this paper, we examined such a case that a branch office building of KT(Korea Telecom) was located near 154 kV underground GIS substation under construction with about 100 meters of the lateral distance between two facilities. GPR (Ground Potential Rise) at the substation and the transferred earth potential at the KT building through the earth in SLG (Single-Line-to- Ground) fault condition were investigated based on a series of computer simulations. The calculated earth potential at a distance of 100 m from the substation was below 120 V which satisfying the limit value of 650 V.

• Proceedings of the KIEE Conference
• /
• 2004.11b
• /
• pp.122-124
• /
• 2004

Recently, power system is getting larger and more complex. When the complex power system has a problem, it is very difficult even for the experts to find out where the problem is and to make a timely decision by operators. There have been many studies on these problems but the results are not good enough for applying to real power system. Therefore power system operators always had to judge the exact state of power system and had to be preparative for the problems that can occur later. We developed new methods that can be applied to complex power system by dividing the system into small modules. By using 'module' we can combine small modules together to make complex power systems and the knowledge base that is applied to fault diagnosis system. As a result, compared to previously developed diagnosis products, operational time has shortened, and the knowledge base becomes simpler and clearer, which made online usage capable. This system can be used as a complementary measure that helps the operator from making any mistakes.

• Journal of the Korean Institute of Gas
• /
• v.8 no.2 s.23
• /
• pp.28-34
• /
• 2004

Enhanced methodologies for process diagnosis and abnormal situation management have been developed for the last two decades. However, there is no single method that always shows better performance over all kinds of diagnostic problems. In this paper, a framework of message-passing, cooperative, intelligent diagnostic agents is presented for improved on-line fault diagnosis through cooperative problem solving of different expertise. A group of diagnostic agents in charge of different process functional perform local diagnoses in parallel; exchange related information with other diagnostic agents; and cooperatively solve the global diagnostic problem of the whole process plant or business units just like human experts would do. For their better understanding, sharing and exchanging of process knowledge and information, we also suggest a way of remodeling processes and protocols, taking into account semantic abstracts of process information and data. The benefits of the suggested multi-agents-based approach are demonstrated by the implementations for solving the diagnostic problems of various chemical processes.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.8 no.2
• /
• pp.117-127
• /
• 1998

Power systems have uncertain dynamics due to a variety of effects such as lightning, severe storms and equipment failures. The variation of the effective reactance of a transmission line due to a fault is an example of uncertainty in power system dynamics. Hence, a robust controller to cope with these uncertainties is needed. Recently, fuzzy controllers are becoming quite popular for robust control due to its potential of dealing with uncertain systems. Thus in this paper we design an adaptive fuzzy controller based on an input-output linearization approach for the transient stabilization and voltage regulation of a power system under a sudden fault. Also this paper proposes a fuzzy system that estimates the upper bound of uncertain term in the system dynamics to guarantee the Lyapunov stability. Simulation results show that good performance is achieved by the proposed controller.