• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.261-262
• /
• 2008

Failure Mode Effects and Criticality Analysis (FMECA) evaluates criticality and severity of each failure mode. Generally, those indices are determined subjectively by experts and operators. However, this process has no choice but to include uncertainty. In this paper, a method for eliciting expert opinions considering its uncertainty is proposed to evaluate the criticality and severity. In addition, a fuzzy expert system is constructed to determine the crisp value of risk level for each failure mode. The results are worth considering while deciding the proper policies for each component of the system.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.6
• /
• pp.870-875
• /
• 2013

After introducing diagnosis equipment power failure prevention activities for distribution system have become more active. To do facility diagnosis and maintenance work more efficiently we need to evaluate reliability for the system and should determine the priority line with appropriate criteria. Thus, to calculate risk factor for the power distribution line that are composed of many component facilities its historical failure events for the last 5 years are collected and analysed. The failure statics show that more than 60% of various failures are related to environment factors randomly and about 20% of the failures are refer to the aging. As a strategic evaluation system reflecting these environmental influence is needed, a system on the basis of the probabilistic approach related statical variables in terms of failure rate and failure probability of electrical components is proposed. The figures for the evaluation are derived from the field failure DB. With adopting Bayesian rule we can calculate easily about conditional probability query. The proposed evaluation system is demonstrated with model system and the calculated indices representing the properties of the model line are discussed.

• Journal of Electrical Engineering and Technology
• /
• v.11 no.1
• /
• pp.47-54
• /
• 2016

Microgrids offer several reliability benefits, such as the improvement of load-point reliability and the opportunity for reliability-differentiated services. The primary goal of this work is to investigate the impacts of operating condition on the reliability index for microgrid system. It relies on a component failure rate model which quantifies the relationship between component failure rate and state variables. Some parameters involved are characterized by subjective uncertainty. Thus, fuzzy numbers are introduced to represent such parameters, and an optimization model based on Fuzzy Chance Constrained Programming (FCCP) is established for reliability index calculation. In addition, we present a hybrid algorithm which combines scenario enumeration and fuzzy simulation as a solution tool. The simulations in a microgrid test system show that reliability indices without considering operating condition can often prove to be optimistic. We also investigate two groups of situations, which include the different penetration levels of microsource and different confidence levels. The results support the necessity of considering operating condition for achieving accurate reliability evaluation.

• Proceedings of the KIEE Conference
• /
• 1994.11a
• /
• pp.33-35
• /
• 1994

This Paper Presents a practical approach to evaluate the reliability indices of electric distribution systems. The use of reliability evaluation is placed with the framework of distribution system planning. In this paper, the reliability model is based on an analytical method, connecting component failure to load point outage each section. five case studies are reported in the paper. These are to study the effect of varying failure rates and repair times on distribution feeders. The results of a study on sample system are presented in this paper.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.326-327
• /
• 2011

Failure rate serves as a pivotal role in reliability study. When the system operates, failure datum of the system reflects the actual operating environment. Therefore, when we estimate the system's with the component failure data, we can find the more exact failure rate that reflected the system's operating environment. In this paper, we use the components' fault data and find out failure rate.

• Proceedings of the KIEE Conference
• /
• 2003.11a
• /
• pp.272-274
• /
• 2003

Distribution system reliability evaluation estimates by approach methods such as Makove modelling or Monte Carlo simulation, equation of state and failure rate that is on one basic data used to these assessment technique is described as probability of average value. because average failure rate equipment device is aged as time goes by but there is shortcoming that such used failure rate does not evaluate thing which is correct in reliability change hereafter. In this paper, failure rate displayed that apply aging to basis equipment device by passing time using Weibull distribution one of life evaluation method and for express aging of component from utility's failure database.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.9 no.5
• /
• pp.64-70
• /
• 1995

This paper presents a practical approach to evaluate the reliability indices of electric distribution systems. The use of reliability evaluation is placed with framework of distribution system planning and operation. In this paper, the reliability model is based on an analytical method, connecting component failure to load point outage in each section. Five cases are reported in the paper to study the effect of varying failure rates and repair times on real distribution systems. Simulations are preformed by the developed reliability evaluation program.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 2007.04a
• /
• pp.331-333
• /
• 2007

Product reliability is important to quality and competitiveness. Much management and engineering efforts go into evaluating reliability, assessing new designs and changes of manufacturing processes, identifying cause of failure. Major methods are based on environmental test. In this study, we analysis the environmental test data of the electrical component, unit, set. These data were gathered for 7 years.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.11
• /
• pp.1543-1550
• /
• 2015

Ferroresonance is a non-linear vibrational phenomenon that is generated by the electrical interaction of the inductance component with the capacitor component of a certain capacitance as the device of the inductance component such as a transformer is saturated due to the degradation, the waveform distortion of current and voltage, and the oscillation of overcurrent and overvoltage in a system. Recently, ferroresonance was generated from the waveform distortion of current and voltage, or the overvoltage or undervoltage phenomenon caused by the nature of an electrical power system and design technology of the transformer in the three phase transformer system. Hence, in general, ferroresonance analyzed by converting to the LC equivalent circuit. However, in general, the aforementioned analytical method only applies to the resonance phenomenon that is generated by the interaction of the capacitance of bussbar and grounding, and switching as the capacitor component with PT and the transformer as the inductance component in a system. Subsequently, the condition where ferroresonance was generated since overvoltage was supplied as line voltage to the phase voltage and thus the iron core is saturated due to the interconnection between grounded and ungrounded systems could not be analyzed when single phase PT was connected in a ${\Delta}$/Y connection system. In this study, voltage swell in the configuration of grounded circuit of a step-up transformer with the ${\Delta}-{\Delta}$ connection linked to PT for control power and the ferroresonance generated by overvoltage when the line voltage of the ${\Delta}-{\Delta}$ connection was connected to the phase voltage of the grounded Y-Y connection were analyzed using PSCAD / EMTDC through the failure case of the transformer caused by ferroresonance in the system with the ${\Delta}-{\Delta}$/Y-Y connection, and subsequently, the preventive measure of ferroresonance was proposed.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.50 no.4
• /
• pp.168-176
• /
• 2001

In this paper, we develop a dual-duplex system which detects a fault by hardware comparator and switches to hot standby redundancy. This system is designed on the basis of MC68000 and can be used in VMEbus. To improve reliability, the dual-duplex system is designed in dual modular redundancy. The failure rate of electrical element is calculated in MILSPEC-217F, and the system RAMS(Reliability, Availiability, Maintainability and Safety) and MTTF(Mean Time to Failure) are evaluated by Markov modeling method. As the evaluation result shows improved reliability, it can be used as a component hardware for a highly reliable control system.