Sharif Digital Repository

The aim of this two-part paper is to present a comprehensive reliability-centerd maintenance framework tailored to power distribution systems. The first paper discusses the fundamental concepts, presents the developed algorithm, and introduces the required mathematical formulations. This second paper is focused on the application of the proposed methodology on a real distribution system. Considerable effort is devoted to examine the proposed method in a step-by-step manner to clarify the implementation procedure. The required data for the procedure are taken from available references and follow reasonable technical assumptions. Practical aspects are incorporated, and the results obtained are... 

Power plant successful operation is always a function of its constituent sub-systems and components. Due to the current financial constraints in power industry, power plant operators are continuously facing a wide range of challenges when dealing with maintenance scheduling and asset management practices of the plant sub-systems. Knowledge on the roles and criticality of the constituent components on the plant overall performance will help in establishing the plans for its smooth, safe, and economic operation. To ensure making the techno-economical decisions on the maintenance of power plant equipment, this paper focuses on the reliability modeling of the combined cycle power plants (CCPP).... 

Electricity companies have been under a great pressure to improve their technical and financial performances in order to survive and thrive in the deregulated environment. Therefore, these companies are seeking for innovative approaches to take the most out of the restricted resources. These approaches inherently concentrate the available budgets to the most critical components. In this regard, prioritizing the system components and identifying the most critical ones play a vital role in the planning and operation of the system. This paper presents a novel approach to prioritize power transmission system components. In the proposed methodology, a criticality factor is defined and implemented... 

Although reliability-centered maintenance (RCM) has proven its noticeable merits in many industries, has not been yet furnished with efficient analytical methods in the power engineering context. The first of this two-paper set presents a practical framework by which the RCM procedure can be implemented in power distribution systems. The proposed algorithm consists of three main stages. The prerequisites of the analysis are outlined in the first stage. In the second stage, an approach is developed to identify the network's critical components, from the reliability point of view. Having practically modeled the components' failure rates, an efficient cost/benefit evaluation approach is then... 

As the electricity market undergoes continuous evolutions, along with the outdated nature of the grid, system operators would have to be able to more effectively manage the operation costs since waves of maintenance costs and equipment investments would be anticipated in the years to come. Strategic implementation of cost-effective reliability centered maintenance (RCM) approaches seems to be a key solution. This paper proposes an efficient method to assess the component criticality for the system overall reliability and further maintenance focuses. A solution concept of game theory, called Shapely Value, that is able to fairly identify the contribution of each single equipment to the system... 

As the electricity market undergoes continuous evolutions, along with the widely-recognized outdated nature of the grid, system operators would have to be able to more effectively manage the system operation expenses since waves of maintenance costs and equipment investments would be anticipated in a few years to come. Strategic implementation of cost-effective reliability-centered maintenance (RCM) approaches seems to be a key solution. This paper proposes an efficient method to assess the component criticality for system overall reliability and further maintenance focuses. A solution concept of game theory, called shapely value, is proposed that is able to fairly identify the contribution... 

First stage nozzles are considered as one of the most critical components in the heavy-duty gas turbines because of their operational in-service condition in the hot gas path. In the present research, the failure analysis of a first stage nozzle in a 159 MW gas turbine is investigated in order to specify the modes and mechanisms of the failure and their root causes. Various examinations including macroscopic and visual inspection of the nozzle outer surface, the micro examination of the fracture surface, chemical analysis and metallographic analysis were carried out to complete the investigation. The micro and macro examinations revealed cracks, erosion and oxidation damages in the nozzle... 

Contact wires are critical components of railway overhead infrastructure which provide power for trains. This paper proposes an innovative method to determine the service life of worn contact wires under three failure modes: tension, fatigue, and attrition. The tensile stress, fatigue damage, and cross-section loss of contact wire have been modelled as stochastic processes following lognormal distribution. The first-passage probability method is then used to determine the time-dependent failure probability for contact wires under each failure mode. The service life of the contact wire is determined through system reliability analysis. This method has then been applied to a case study to... 

Confronted with the power system restructuring trend reforming the past-regulated power systems, the need for a narrower insight on the costly maintenance strategies seems imperative. It falls within the realm of reliability centered maintenance to enhance the cost effectiveness of power distribution maintenance policies. From a practical point of view, this paper devises a novel approach on the basis of the analytical hierarchical process (AHP) accompanied by fuzzy sets theory to determine the most critical component types of distribution power systems to be prioritized in maintenance scheduling. In the presence of many qualitative and quantitative attributes, fuzzy sets can effectively... 

The present context of the electric industry, characterized by competitive markets, privatization, and regulatory of technical requirements forces the power utilities to optimize their asset management practices and develop the requisite decision plans techno-economically. Practically approaching, this paper devises a new support tool based on a multiattribute decision making (MADM) framework in combination with analytical hierarchical process (AHP) to determine the most critical components of power transmission systems. Measure of system-wide reliability performance, outage cost, marginal clearing prices demonstrative of market fairness, and network losses are among the attributes... 

Heavy-duty gas turbines are usually devised in power plants to generate electrical energy. Sudden failure in any of its parts or subdivisions will result in a decrement of the efficiency of the system or emergency shutdown of the system. The highest risk of failure in these turbines is subjected to the hot gas path (HGP) of the turbine. Due to the existence of uncertainty in diagnosing process or damage growth, in this research, a modified risk-based probabilistic failure analysis model using Bayesian networks (BN) was developed. First, a failure model was developed using the Fault Tree Analysis, and then it is transformed into a BN model. This model is capable of predicting and diagnosing... 

Low-noise amplifiers (LNAs) with low-noise performance are critical components in communication systems. However, reaching a high level of performance is difficult. This study introduces a LNA for radio frequency front-end receivers with a frequency range of 6–12 GHz. The planned LNA contains a two-stage high-electron-mobility transistor cascade amplifier with a minimum measured noise figure of 0.8 dB and a peak gain of 25 dB at room temperature. The proposed LNA is based on a gallium arsenide field-effect transistor transistor (CE3512K2) because of its good low-noise performance at microwave frequency bands. The measured results demonstrate that the proposed LNA is perfectly matched over... 

Capacitors are one of the most critical components in power electronic converters, yet they are notoriously susceptible to failure. Avoiding unforeseen outages caused by capacitor failures is one of the most effective approaches to increase system availability. Therefore, a variety of methods have been proposed to monitor a capacitor health condition based on different degradation indicators. This paper proposes a new approach based on the accurate measurement of an electrolytic capacitor dissipation factor to detect its end-of-life. Since the dissipation factor is affected by both the capacitor resistance and capacitance simultaneously, it can provide more information about the health... 

Compared with fossil fuel, biomass is a clean energy with zero CO 2 emission, because CO 2 is fixed by photosynthesis during biomass growth and released again during utilization. Due to its low energy density, direct use of biomass is not convenient. Thus, it is necessary to convert biomass to fuel gas, such as hydrogen, which can be used cleanly and highly efficiently in fuel cell. Thermo-chemical gasification is likely to be the most cost-effective conversion process and it is promising technology for renewable hydrogen production by utilizing biomass. Biomass gasification produces a mixture of gases (mainly consisting of H 2, CO, CO 2, CH 4 and higher hydrocarbons), solids (char) and...