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혼합 와이블 분포를 이용한 고장률 산출 기법에 관한 연구
채희석(Hui-seok Chai),신중우(Joong-woo Shin),임태진(Tae-jin Lim),김재철(Jae-chul Kim) 대한전기학회 2017 전기학회논문지 Vol.66 No.3
In 2014, ISO 55000s has been enacted and the power plant asset management is becoming a hot issue for all over the world. The asset management system is being developed as a combination of CBM(Condition Based Maintenance) and RCM(Reliability Centered Maintenance). Therefore, the research on the calculation of the failure rate which is the most basic index of RCM is actively carried out. The failure rate calculation has been going on for a long time, and the most widely used probability distribution is the Weibull distribution. In the Weibull distribution, the failure rate function is determined in three types according to the value of the shape parameter. However, the Weibull distribution has a limitation that it is difficult to apply it when the trend of failure rate changes-such as bathtub curves. In this paper, the failure rate is calculated using the mixture Weibull distribution which can appropriately express the change of the shape of the failure rate. Based on these results, we propose the necessity and validity of applying mixture Weibull distribution.
저압계통 연계력을 고려한 지상변압기 용량증가에 따른 이용률 분석에 관한 연구
채희석(Hui-Seok Chai),신중우(Joong-Woo Shin),문종필(Jong-Fil Moon) 대한전기학회 2021 전기학회논문지 P Vol.70 No.3
Underground power system has been mostly configured in a type of transformers connected to branch lines. However, Configuration type of transformer connected to main line with open or looped low voltage(LV) network is now being applied to underground system to improve operating complexity and customer’s reliability. In this paper, when a transformer connection type is changed and already installed transformers are used, utilization factors of the transformers are analyzed. We divided 13 sections and two capacities of transformers. If there is a fault at 1 transformer, it is analyzed how the other’s utilization factor can be changed using monte carlo simulation. Futhermore, the growth of load is applied to analyze the utilization factors of transformers. thus, the trends of utilization factors are presented according to years.
신뢰도 비용 최소화를 위한 개폐기의 최적 자동화율 도출에 관한 연구
채희석(Hui-seok Chai),강병욱(Byoung-wook Kang),김진석(Jin-seok Kim),문종필(Jong-fil Moon),김재철(Jae-chul Kim) 대한전기학회 2015 전기학회논문지 P Vol.64 No.4
Replacing a manual switch installed in a feeder for a distribution system with an automatic one increases the reliability of the electric power system. This is because the automatic switch can shorten the duration of a fault the customer experiences by splitting the faulty section faster than the manual one does. However, improving the reliability of the distribution system may increase investment costs. Here, the investment costs include automatic switch cost, replacement work cost and labor cost. For this reason, importance should be attached to the proper balance between the increase of the investment costs and the improvement of the reliability of the distribution system. This article analyzed reliability index and economics when manual switches installed in a feeder (RBTS Bus2 model) was replaced by automatic ones. In addition, it attempted to draw the optimum rate of automation of manual switches by automatic ones using the GRG optimization method, considering the current economic requirements.