• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2119-2124
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• 2010

Reliability evaluation of power distribution system is the evaluation for all customers supplied from one power source as main transformer located in substation. However, power sources include not only the main transformer but distributed generations. Typical reliability evaluation has focused on configuration of power system with one source including failure rates of equipment. In this paper, we focus on not only configuration but power sources as distributed generations. New reliability evaluation method using power supplied probability (PSP) is proposed. The proposed evaluation method are proved through case studies.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.3
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• pp.163-168
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• 2014

In this paper, when photovoltaic systems are connected to distribution system, most effective capacity and location of PV system are studied considering customer interruption costs of power distribution system. The reliability model of PV system considering the duration of sunshine, the model of time-varying load and Roy Billinton test system (bus2 model) are used. To simulate the effects of PV system, various cases are selected; (1) base case which is no connection of PV system to power distribution system when faults are occurred, (2) 3MW case which is 3[MW] connection of PV system (3) 4[MW] case, and (4) 20[MW] case which is 20[MW] connection of PV system to the bus of power distribution system. The capacity limit of connected PV system is settled to 14[MW] for all cases except case 4. The reliability and customer interruption costs for residential, general, industrial, and educational customer is evaluated.

• International Journal of Reliability and Applications
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• v.11 no.1
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• pp.1-16
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• 2010

In this paper we will discuss the stochastic analysis of a three state semi-Markov reliability model. Maximum likelihood procedure will be used to obtain the estimators of the parameters included in this reliability model. Based on the assumption that the lifetime and repair time of the system units are generalized linear failure rate random variables, the reliability function of this system is obtained. Also, the distribution of the first passage time of this system will be derived. Some important special cases are discussed.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.201-210
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• 2010

In this study, new methodology to estimate the reliability of a water distribution system using HSPDA model is suggested. In general, the reliability of a water distribution system can be determined by estimating either the ratio of the required demand to the available demand or the ratio of the number of nodes with sufficient pressure head to the number of nodes with insufficient pressure head when the abnormal operating condition occurs. To perform this approach, hydraulic analysis under the abnormal operating condition is essential. However, if the Demand-Driven Analysis (DDA) which is dependant on the assumption that the required demand at a demand node is always satisfied regardless of actual nodal pressure head is used to estimate the reliability of a water distribution system, the reliability may be underestimated due to the defect of the DDA. Therefore, it is necessary to apply the Pressure-Driven Analysis (PDA) having a different assumption to the DDA's which is that available nodal demand is proportion to nodal pressure head. However, because previous study used a semi-PDA model and the PDA model which had limited applicability depending on the characteristics of a network, proper estimation of the reliability of a water distribution system was impossible. Thus, in this study, a new methodology is suggested by using HSPDA model which can overcome weak points of existing PDA model and Available Demand Fraction (ADF) index to estimate the reliability. The HSPDA can simulate the hydraulic condition of a water distribution system under abnormal operating condition and based on the hydraulic condition simulated, ADF index at each node is calculated to quantify the reliability of a water distribution system. The suggested model is applied to sample networks and the results are compared with those of existing method to demonstrate its applicability.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1482-1488
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• 2014

The reliability evaluation of the electrical distribution networks (EDN) requires sufficient consideration of the effects of planned outages. The planned outages of the EDN can be divided, by outage models and their effects on the reliability into two major categories: by equipment and by feeder. After studying the characteristics of different categories of planned outages, this paper expands the classification of load points by outage time from 4 types to 7 types and defines corresponding reliability parameters for the different types. By using the section algorithm, this paper proposes a reliability evaluation technique of EDN considering equipment random failures and two categories of planned outages. The proposed technique has been applied to the RBTS-BUS6 test system and some practical EDNs in China. The study results demonstrate that the proposed technique is of higher practical value and can be used for evaluating the reliability performance of EDN more efficiently considering the planned outages.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.90-96
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• 1998

Helical gear system is widely used to transmit heavy duty power with harmonies and silences between parallel shafts. This paper predicts a life with Weibull distribution and estimates a reliability based on recycle principle of helical gear systems. 2-parameter Weibull distribution is generally adopted to estimate the mechanical life and the reliability of most gear systems, because this Weibull distribution is proper to explain a characteristics or a life of parts of gear systems with linearity of probability density data on weibull data sheet. For a high reliability, this paper estimates a number of overhaul times and a number of needed substitutes (exchange attachment,1 or parts) with following renewal theory, One is make an exchange of whole module include failure attachments/parts and second estimating method is only exchange of a failure attachments / parts.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.1
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• pp.7-14
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• 2002

In power system study, relibility assessment has been an important topic during past several decards because sudden power interruption can bring about enormous economic loss. although the size of a substation is smaller than that of generation system or transmission system, switching actions after fault(s) make reliability assessment of substation rather complex situations such as switching actions easily and permit various probability distributions in describing substation elements. Despite this ability of Monte Carlo simulation, one-parameter exponential distribution is still popular in this reliability assessment. This paper examines the characteristics of several two-parameter probability distributions, and offers new parameter decision rule based on average and variance of the target to be modelled. In case study, this paper shows the profits by using Weibull distribution which is one of two-parameter probabilistic distributions instead of exponential one.

• Journal of Applied Reliability
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• v.17 no.4
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• pp.332-342
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• 2017

Purpose: In this study, the lifetime distribution of a k-out-of-n system with heterogeneous components is suggested as Markov model, and the time-to-failure (TTF) distribution of each component is considered as phase-type distribution (PHD). Furthermore, based on the model, a redundancy allocation problem with a mix of components (RAPMC) is proposed. Methods: The lifetime distribution model for the system is formulated by the structured Markov chain. From the model, the various information on the system lifetime can be ascertained by the matrix-analytic (or-geometric) method. Conclusion: By the generalization of TTF distribution (PHD) and the consideration of heterogeneous components, the lifetime distribution model can delineate many real systems and be exploited for developing system operation policies such as preventive maintenance, warranty. Moreover, the effectiveness of the proposed RAPMC is verified by numerical experiments. That is, under the equivalent design conditions, it presented a system with higher reliability than RAP without component mixing (RAPCM).

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.154-156
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• 1987

An important aspects of power system design involves consideration of service reliability requirements of load to be supplied and service reliability provided by any proposed system. This paper shows the investigation of the 1984 KEPCO service reliability to the large electric consumer whose contracted maximum demand is over 500 kw. 68 customers of the total 111 investigated are located in Myungdong area and Yuido in Seoul. Of the customers are included hotel Lotte, Giobo and Seoul national University Hospital. The average service reliability of Myungdong area customers is 316min/yr/customer and about 7 times/yr/customer, and 160 min, 6 times for Yuido. Which the service reliability the interruption and the interruption frequency which caused by the customers receiving facilities were showed. The investigation is telling that the service reliability of the underground distribution area are very superior to the other area reliability. The investigated reliability seem not appropriate to be improved by change of distribution System as well as equipments and facilities improvement in the near future.

• Journal of applied mathematics & informatics
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• v.5 no.2
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• pp.277-284
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• 1998

The reliability and an estimate for it are derived for series-parallel and parallel-deries stress-strength model under assumption that all components are subjected to a common stress. We also obtain the asymptotic normal distribution of the estimate.