• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.6
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• pp.791-796
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• 2012

This paper presents the various analysis of the power system for operating the new SIHWA tidal power plant. In the analysis of the power system, summer load condition of 2011 is used. Especially, power flow, fault current, voltage and contingency of SIHWA tidal power plant area are analyzed by using PSS/E and there is no problem for the dynamic stability simulation. The new SIHWA tidal power plant is located in near metropolitan area where about 43% amount of the system load is consumed. Therefore, transmission losses are reduced. In addition, system marginal price can be lowered by generating the new SIHWA tidal power plant. The generation pattern of the SIHWA tidal plant is analyzed and the changes of generation are presented for various water levels by control of the rotor angle alpha and beta in water wheel generator.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.484-485
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• 2008

A micro-grid (MG) is a new concept to aggregate distributed generations (DGs) and loads in a small area. The difference between MG and DG is that MG can supply power to loads even in islanding conditions. The magnitude of the fault current depending on interconnection between the MG and utility and the number of DGs in the MG. Therefore, the setting value of the OCR must be changed depending on operating conditions of the MG. This paper proposes the over-current relay considering operating conditions of the MG. In the proposed algorithm, the supervisory control and data acquisition decides the operating conditions of the MG and sends the proper setting values to each OCR. The performance of the algorithm was investigated in the case of the various operating conditions.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.53-63
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• 2013

To guide the decision making of the expert engineer specialized in power system operation and control; the practical OPF solution should take in consideration the critical situation due to severe loading conditions and fault in power system. Differential Evolution (DE) is one of the best Evolutionary Algorithms (EA) to solve real valued optimization problems. This paper presents simple Differential Evolution (DE) Optimization algorithm to solving multi objective optimal power flow (OPF) in the power system with shunt FACTS devices considering voltage deviation, power losses, and power flow branch. The proposed approach is examined and tested on the standard IEEE-30Bus power system test with different objective functions at critical situations. In addition, the non smooth cost function due to the effect of valve point has been considered within the second practical network test (13 generating units). The simulation results are compared with those by the other recent techniques. From the different case studies, it is observed that the results demonstrate the potential of the proposed approach and show clearly its effectiveness to solve practical OPF under contingent operation states.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.263-268
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• 2004

In the present study, a Nd;YAG Laser (pulse type) was used to emit ultrasonic signals to a test material. In addition, a total ultrasonic investigation system was designed by adopting a Fabry-Perot interferometer, which receives ultrasonic signals without any contact. For non-destructive test SM45C, which contains some flaws was used as a test material. Because it is easy to align light beam in receiver, and the length of the light beam does not change much even if convex mirror leans towards one side, confocal Fabry-Perot interferometer, which has stable frequency, and PI control are used to correct interfered and unstable signals from temperature, fluctuation and time shift of laser frequency. Stable signals are always obtained by the feedback of PI circuit signals in the confocal Fabry-Perot interferometer. The type, size and position of flaws inside the test material were examined by achieving the stabilization of an interferometer. This study presented a useful method, which could quantitatively investigate the fault of objects by using a Fabry-Perot interferometer.

• Journal of Power Electronics
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• v.11 no.4
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• pp.533-541
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• 2011

The redundant operation of a parallel AC to DC converter via a serial communication bus is presented. The proposed system consists of three isolated CUK power factor correction modules. The controller for each converter is a dsPIC30F6010 microcontroller while a RS485 communication bus and the clock signal are used for synchronizing the data communication. The control strategy of the redundant operation relies on the communication of information among each of the modules, which communicate via a RS485 serial bus. This information is received from the communication checks of the converter module connected to the system to share the load current. Performance evaluations were conducted through experimentation on a three-module parallel-connected prototype, with a 578W load and a -48V dc output voltage. The proposed system has achieved the following: the current sharing is quite good, both the transient response and the steady state. The converter modules can perform the current sharing immediately, when a fault is found in another converter module. In addition, the transient response occurs in the system, and the output voltages are at their minimum overshoot and undershoot. Finally, the proposed system has a relatively simple implementation for the redundant operation.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1694-1697
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• 2002

KEPCO is planing to adopt a preventive diagnostic system to obtain the reliability of transformer and GIS in 765kV substation. KEPRI has developed the preventive diagnostic system for 765kV substation since 1997. We used various sensors and fault detecting devices such as a dissolved gas analyzer in oil, a ultrasonic detector and LA leakage current detector, etc., and carried out adaptation tests at the both a laboratory and a site. We developed a data acquisition system, a communication control unit and a server system as well. Furthermore, monitoring program and diagnostic expert system were also developed. This paper describes the preventive diagnostic system for 765kV Sin-Ga-Pyong and Sin-Tae-Baek substations which will be operated from 2004.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.22-35
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• 1992

In highly automated machining centers, intelligent sensor fddeback systems are indispensable on order to monitor their operations, to ensure efficient metal removal, and to initate remedial action in the event of accident. In this study, an on-line tool wear detection system for thrning operations is developed, and experimentally evaluated. The system employs multiple sensors and the signals from these sensors are processed using a multichannel autoegressive (AR) series model. The resulting output from the signal processing block is then fed to a previously tranied artificial neural network (multiayered perceptron) to make a final decision on the state of the cutting tool. To learn the necessary input/output mapping for tool wear detection, the weithts and thresholds of the network are adjusted according to the back propagation (BP) method during off-line training. The results of experimental evaluation show that the system works well over a wide range of cutting conditions, and the ability of the system to detect tool wear is improved due to the generalization, fault-tolearant and self-ofganizing properties of the neural network.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.205-212
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• 1999

A three dimensional binary parallel robot manipulator uses actuators which have only two stable states and its structure is variable geometry truss. As a result, it has a finite number of states and fault tolerant mechanism because of kinematic redundancy. This kind of robot manipulator has some advantages compared to a traditional one. Feedback control is not required, task repeatability can be very high, and finite state actuators are generally inexpensive. Because the number of states of a binary robot manipulator grows exponentially with the number of actuators it is very difficult to solve and inverse kinematic problem. The goal of this paper is to develop an efficient algorithm to solve an inverse kinematic problem of three dimensional binary parallel robot manipulator using a backbone curve when the number of actuators are too much. We first derive the coordinate transformations associated with a three degree of freedom in-parallel actuated robot manipulator. The backbone curve is generated optimally by considering the maximum roll and pitch angles of the robot manipulator configuration and length of link. Then, the robot manipulator is fitted along the backbone curve with some criterion.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.12C
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• pp.1228-1237
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• 2002

Network management is composed of five major functional areas, fault, configuration, account, performance and security management in the ITU standards. Configuration management identifies, exercises control over, collects data from network element node system and provides data to the management systems. The proposed architecture is designed based on the Distributed Processing Environment of CORBA(Common Object Request Broker Architecture) Spec v2.3. In this paper, configuration management system has been designed and implemented with layered managed object. It provides that integrated management of various data link layer technology. We suggest MIB(Management Information Base)/MIT(Management Information Tree) to support integrated management and distributed environment.

• Journal of Korea Port Economic Association
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• v.22 no.2
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• pp.83-108
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• 2006

Regarding the ocean carrier's responsibility for damage indemnification, both his or her duty of care and reason of legal exemption have been considered important. The International Convention for the Unification of Certain Rules relating to Bills of Lading also provides that the ocean carrier indemnifies for the loss or damage of freight on the basis of the principle of liability with fault. In other words, the carrier assumes responsibility only for the loss or damage of freight which is under his or her control and whose safety must be carefully maintained by him or her. The carrier's duty of care which is required for freight safety in accordance with the convention is associated with two themes, seaworthiness of vessel and freight itself. To make ocean freight shipping effective necessities the seaworthiness of the ship that will conduct the shipping service under its responsibility. This will ultimately lead to making the service impressive to the shipper as freight owner. Thus the purpose of this study is to contribute to more reasonable shipping by the shipowner or the carrier who needs to ensure seaworthiness of vessel, and prevent unseaworthiness that may be incurred in accordance with freight characteristics. For the purpose, this paper reviewed the meaning of seaworthiness of vessel through a juridical approach to its causal relationship with ocean freight shipping.