• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.158-161
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• 2010

In the paper, the researcher has proposed to install a relay between Base Station (BS) and Mobile Station (MS) to improve receiving performance of the downlink transmission method of Long Term Evolution (LTE) system whose standards now being established by 3GPP. By setting the distance between the location of BS and the relay installed as by 500m, 1000m, and selecting OFDMA and SC-FDMA as transmission method, the researcher conducted a study to improve the receiving performance of LTE. The results from study revealed that when the location of Relay Station (RS) was closer to BS, it was better to use OFDMA at BS, and SC-FDMA at RS. On the contrary, when the distance between BS and RS was farther, it was better to use SC-FDMA at BS, and OFDMA at RS. In addition, around the center zone between the location of BS and of MS, the researcher was able to improve the receiving performance of the system by utilizing the transmission method suitable for the situation in that area.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.8
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• pp.1113-1118
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• 2018

Protection in HVDC(High Voltage Direct Current) have the very fast velocity of fault detection. Because Fault in HVDC has the fast propagation, large currents, high interruption cost. The focus to velocity caused possibility of errors like a detection error like a high impedance fault. In this paper, Proposed complex composition for get the reliability and velocity. That used SFCL(Super Conducting Fault Current Limiter), Protection Zone and DTS(Distributed Temperature Sensing). The SFCL was detect the fault by quench and DTS&Protection Zone were perceive the detect by variation too. To examine the proposed method, PSCAD/EMTDC simulated. The results of simulation, proposed methods could the detect of fault to whole HVDC line. And that improved the reliability of fault clearing.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.121-130
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• 2021

Cascading failure is the main cause of large blackouts in electrical power systems; this paper analyzes a cascading failure in Hanbit nuclear power plant unit two (2) caused by a circuit breaker (CB) operation failure. This malfunction has been expanded to the loss of offsite power (LOOP). In this study, current practices are reviewed and then the methodologies of how to prevent cascading failures in protection power systems are introduced. An overview on the implementation of IEC61850 GOOSE messaging-based zone selective interlocking (ZSI) scheme as key solution is proposed. In consideration of ZSI blocking time, all influencing factors such as circuit breaker opening time, relay I/O response time and messages travelling time in the communication network should be taken into account. The purpose of this paper is to elaborate on the effect of cascading failure in NPP electrical power protection system and propose preventive actions for this failures. Finally, the expected advantages and challenges are elaborated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1011-1022
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• 2014

Currently, the wireless network environment of air node is constructed mainly of ground relay station. However, as the Korean Peninsula is composed of 70% mountainous region, there are multiple shadow zones. This is calling for effective measures to prevent aircraft from losing communication link during low-mid altitude missions. In this article we propose the utilization of Bezier Curve for estimation of aircraft flight path and control method for entering shadow zone. This method successfully estimated aircraft track, and analyzed the existence, disseminated the warning, and took measures to avoid the shadow zone before entering. This article, suggested after simulated experiments, proves that the method enables seamless communication during air operations.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.234-235
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• 2006

The protection relay keeps electric power facilities by using signals of the voltage and current which are input and output terminals of each equipment. Each relay performances protection algorithm by using informations of own protecting zone. To prevent the mal-operation in inrush current, established transformer differential protection method uses the second harmonics as blocking signal. This method is not operate at the initial inrush. However, in case of the parallel operation, if the initial inrush is occurred in one transformer which is generated, the sympathetic inrush Is occurred in adjacent transformer. This paper approach the sympathetic inrush detecting algorithm of a transformer based on agent. Proposed algorithm, when inrush current occurred, distinguish sympathetic inrush or not by using differential current of adjacent transformer. This algorithm have the advantage of the distinguishing initial inrush and sympathetic inrush at operation of parallel transformer

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1542-1547
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• 2012

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. When calculation method of protection settings and logic for protection of generator asynchronization will be recommended, a distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection, this paper describes an improved backup protection coordination scheme using a new logic that will be suggested.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.232-233
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• 2008

There are various large shocks in optical disc drive system like human touch and speak sound. In this paper, a nonlinear controller and a detection method are proposed. First, a relay nonlinear controller with dead zone is introduced. The structure of this nonlinear controller is simple and has a small amount of calculation. However, this controller has chattering problem when it is working. We suggest a disturbance detection algorithm using Kalman filter in this paper and it shows effective reduction of chattering. The proposed nonlinear controller using this detection algorithm had good performance for the shock.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.850-855
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• 2006

Railway signal interlocking device with the reverse unit control device which is most important from country season, the subway and the high-speed railroad back, electric relay boarding and lodging accomplishes the master and servant and it comes and before from the Japanese back and an electronic interlocking device, a zone one interest in updated technology introduction Great Britain, Germany, Sweden and the United States, it quarrels about under developing it puts to practical use even from our country it shows. About reasoning lower our country subway or the country closing up shop stem there is not a possibility of throwing away the impression where the exhibition hall of foreign nation signal system is being turning out. Consequently is enormous a system well expense at the foreign corporation about under paying Oh!, it understands, with difficult always it is exposed to it is an actuality in the accident which is dangerous. In like this point of view first piece which is important securing safety of system from electronic anger of electronic interlocking device.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.68-74
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• 2007

Critical Chain Project Management(CCPM) is a new project management system paradigm which maintains the advantages of PERT/CPM and improves the shortcomings of it. In CCPM the task durations are determined as 50% time estimates, ie average time discarding the their contingency. CCPM determines the critical chain the constraint of a projects considering the logical precedence relationship and resource conflict resolution. Project buffer is located at the end of critical chain to absorb the variations of critical chain. The size of project buffer is usually calculated as the half of the sum of critical chain length. Also feeding buffer is inserted after each non-critical chain which feeding into the critical chain to prevent the time delay of critical chain from uncertainties of non-critical chains. Resource buffer can be utilized to improve the availability of resources of critical chain. Buffer management is a project execution and control mechanism. Buffers are classified into 3 zones. They are OK zone, Watch and Plan zone and Expediting zone. If the project status is within Watch and Plan zone, contingency plan is established. And if it changes into Expediting zone, the preplanned contingency plan are executed to recover the time delay. In CCPM the workers are asked to work with relay runner work mechanism that they work fast if possible and report their completion to project manager for the succeeding task to start as soon as possible. The task durations are not considered as the promised time schedule. The multi-tasking is prohibited.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.1
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• pp.73-80
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• 2015

The valve device is installed in hazardous areas, such as a chemical plant explosion has been sealed with fire protection device to prevent the risk of explosion. In this paper, due to the explosion-proof devices using external power the device can not be used in infrared sensors and Zigbee sensor valve device by measuring the open degree of valve opening and closing of the danger zone to check whether. Valve opening and closing operation log screen time, we propose a low-power operation monitoring system administrators to manage and control the plant. Develop power control relay board apply an improved algorithm to apply the asynchronous LPL power management. The plant monitoring system and explosion-proof valve opening and closing the valve system with the intelligent device designed and implemented and tested it.