• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.186-193
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• 2015

In this paper, a reliability growth analysis for a next-generation high-speed train was conducted. First, the high-speed train was decomposed into 6 sub-systems and main equipment of the high-speed train was derived from functional diagrams. Next, failure rates were calculated for each sub-system from the failure data obtained during commissioning tests. Then, reliability growth analysis was conducted for the high-speed train using the Duane model. The results show that activities to increase reliability were carried out throughout the test runs from the reliability growth results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.4
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• pp.177-184
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• 2005

This paper proposes a improved investment priority decision method of the facilities considering the reliability of distribution networks. The proposed method decides a investment order of the facilities combining, by fuzzy rules, the investment priority decision of KEPCO and the priority decision considering reliability evaluation indices. Where reliability evaluation indices are SAIFI(System Average Interruption Frequency Index) and SAIDI(System Average Interruption Duration Index), as referred to evaluation index for sustained interruption. The reliability analysis method of distribution networks applied in this paper utilizes analytic method, where the used reliability data is historical data of KEPCO. Particularly, we assumed that the failure rate increased as the equipment ages. To verify the performance of the proposed method, we applied it with the planned projects to reinforce the weak facility electrical facilities in KEPCO in 2004. The evaluation result showed that, under a limited budget, the reliability of the KEPCO in the Busan region using the proposed method can be enhanced than using the conventional KEPCO's method. Therefore, the results verify the proposed method can be efficiently used in the actual priorities method for investing the electrical facilities.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.230-235
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• 2014

The failure modes of pneumatic directional control valves include leakage, wear of the spool seal, and sticking of the spool. Among them, the main failure mode of the valve is leakage. The leakage is caused by the wear of the spool seal. However, due to the characteristics of the seal material, the leakage rate is fluctuated a lot rather than constantly increased over time. If life analysis is performed using the first time data of leakage failure, predicted life cycles can be different from the real life cycles. This paper predicts life cycles of the pilot pneumatic directional control valve based on the three point moving average which considers the average of the fluctuating leakage rate.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.5
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• pp.675-682
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• 2013

Reliability analysis and prediction of next failure time is critical to sustain weapon systems, concerning scheduled maintenance, spare parts replacement and maintenance interventions, etc. Since 1981, many methodology derived from various probabilistic and statistical theories has been suggested to do that activity. Nowadays, many A.I. tools have been used to support these predictions. Support Vector Regression(SVR) is a nonlinear regression technique extended from support vector machine. SVR can fit data flexibly and it has a wide variety of applications. This paper utilizes SVM and SVR with combining time series to predict the next failure time based on historical failure data. A numerical case using failure data from the military equipment is presented to demonstrate the performance of the proposed approach. Finally, the proposed approach is proved meaningful to predict next failure point and to estimate instantaneous failure rate and MTBF.

• Journal of Electrical Engineering and Technology
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• v.2 no.4
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• pp.441-444
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• 2007

The mechanical endurance is the critical characteristic of Magnetic contactors (MCs), which are widely used in such industrial equipments as elevators, cranes, and factory control rooms in order to close and open the control circuit. Testing time, however, is so long in most cases that some method of reducing the testing period is required. Therefore, the degradation test by the detected vibration of MCs is developed to reduce the testing time in this work. The degradation test data are analyzed and the prediction model is provided. Also, the possibility of this technology for Reliability Centered Maintenance (RCM) will be shown. This will reduce the period of the product development and raise the reliability of the equipment in power distribution.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.11
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• pp.76-83
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• 2009

In today's competitive power market, electric power utilities have strived to provide energy at an acceptable level of quality due to increased expectations from customers. For this reason, electric power utilities have invested in electric equipment and new techniques. That is the Distribution Automation System (DAS). A merit of DAS is the ability to reduce outage time because of fast service restoration. However, DAS is usually installed in outdoor environments. Therefore, their efficiency is affected by the external conditions. Lightning creates varying degrees of physical stress on DAS. This paper focuses on the reliability of DAS for lightning. Four application studies were performed to compare the reliability indices.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.5
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• pp.517-523
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• 1999

The Start-up transformers or on-site stand-by transformers are installed for the start-up and shut-down of generator and emergency status in unclear power plant. The on-site power supply configuration using these transformers must be detemined by considering configuration requirements, site characteristics, reliability and availability severely because it is remarkably important for safety and benefit of plant. The start-up or stand-by power supply configuration has been determined considering only safety requirements and construction cost up to now in Korea. I study various reliability estimating methods for the prediction of availability, and estimate the unavailability for the start-up power supply system of two 1,000㎿ unclear power plants. I also detemine the reliability and unavailability and unavailavility of equipment, system and configuration using FTA method.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.248-254
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• 2008

Electric railway system consists of traction power system, rolling stock, track, and overhead line system. A railway substation transforms the electric power transmitted from a electric power company and supply it to the railway power system for the operation of traction system.. It is very important to prevent a possible accident and keep the security of electric power system. This paper proposes a reliability analysis of AC railway substation by using Fault Tree Analysis(FTA). Failure rates of each equipment of railway substation are used to evaluate the reliability of railway substation. The analyzed results can be used to improve the system reliability. FTA is performed by the commercialized program of Relex(Ver. 7.7).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.247-254
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• 2019

Recently, in designing military equipment, considerable attention has been paid to maintaining operations, including reliability, maintenance, and maintenance time of equipment, from the early stages of development. Therefore, both users and developers stress the importance of design considering the maintenance time. This study evaluated the specific methodologies for predicting the realistic maintenance time, such as the access complexity of equipment, other than the standard maintenance time provided by the conventional method mil-hdbk-470a at the beginning of the design, and applied the time conversion factor using a measure of the maintenance complexity. In addition, the actual maintenance time reflecting the actual maintenance time of the developed equipment and the time-conversion factor applied was compared/verified to confirm the reliability of the data. In a study to set a target for repair and the repair of equipment design in the future, it is expected that the maintenance time of equipment that fails to measure the maintenance time for the initial actual equipment will be reflected as a more realistic time. Moreover, activities, such as research and design reflection activities, will be performed to reduce the maintenance time, operational maintenance cost, etc.

• Journal of Navigation and Port Research
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• v.30 no.6 s.112
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• pp.525-531
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• 2006

In the port, the yard crane is very important. If a container crane or a transfer crane is broken down, it costs a lot because of the delay of work during the period of repair or reorder. But, we don't have enough spare parts because of the high cost. It is necessary to maintain high reliability of the crane through effective preventive maintenance and failure analysis. In this paper, we analyse the function and failure mechanism of the transfer crane which is a main equipment in the yard Also, we standardize failures and maintenance works using the historical data of failure and maintenance. This study which is a basic work for effective equipment operation and maintenance will support reliability engineers to decide the optimal design of the next generation equipment and operational policy of equipment.