Failure Rates Of System Components Research Articles

Reliability assessment of grid-connected multi-inverter for renewable power generation sector

PurposeThe paper aims to present a grid-connected multi-inverter for solar photovoltaic (PV) systems to enhance reliability indices after selected the placement and level of PV solar.Design/methodology/approachIn this study, the associated probability is calculated based on the solar power generation capacity levels and outages conditions. Then, based on this probability, dependability indices like average energy not supplied (AENS), expected energy not supplied and loss of load expectations (LOLE) are computed, also, another indices have been computed such as (customer average interruption duration index (CAIDI), system average interruption frequency index (SAIFI) and system average interruption duration index (SAIDI)) addressing by affected customers with distribution networks reliability assessment, including PV. On the basis of their dependability indices and active power flow, several PV solar modules installed in several places are analyzed. A mechanism for assessing the performance of the grid's integration of renewable energy sources is also under investigation.FindingsThe findings of this study based on data extracted form a PV power plant connected to the power network system in Diyala, Iraq 132 kV, attempts to identify the system's weakest points in order to improve the system's overall dependability. In addition, enhanced reliability indices are given for measuring solar PV systems performance connected to the grid and reviewed for the benefit of the customers.Originality/valueThe main contributions of this study are two methods for determining the reliability of PV generators taking into consideration the system component failure rates and the power electronic component defect rates in a PV system which depend on the power input and the power loss using electrical transient analysis program (ETAP) program.

Search the optimal ratio of system’s component reliability parameters and the heat capacity of prosumers in the district heating system

The paper presents a methodology for ensuring the reliability of heat supply to prosumer connected to a district heating system, by using the heat capacity of its own heat source and optimization of failure rates of system components. To solve this problem, a mathematical formalization is developed, within which a markov random process, a flow distribution model of the theory of hydraulic circuits, nodal reliability indices, and simplified models of heat transfer processes in heat supply to consumers are used. A case study is considered based on a test scheme of district heating system with prosumer, an analysis of the results obtained is carried out, conclusions and directions for the further research on the subject are formulated.

Dynamic reliability assessment of flare systems by combining fault tree analysis and Bayesian networks

ABSTRACT Flaring is a combustion process commonly used in the oil and gas industry to dispose flammable waste gases. Flare flameout occurs when these gases escape unburnt from the flare tip causing the discharge of flammable and/or toxic vapor clouds. The toxic gases released during this process have the potential to initiate safety hazards and cause serious harm to the ecosystem and human health. Flare flameout could be caused by environmental conditions, equipment failure, and human error. However, to better understand the causes of flare flameout, a rigorous analysis of the behavior of flare systems under failure conditions is required. In this article, we used fault tree analysis (FTA) and the dynamic Bayesian network (DBN) to assess the reliability of flare systems. In this study, we analyzed 40 different combinations of basic events that can cause flare flameout to determine the event with the highest impact on system failure. In the quantitative analysis, we use both constant and time-dependent failure rates of system components. The results show that combining these two approaches allows for robust probabilistic reasoning on flare system reliability, which can help improving the safety and asset integrity of process facilities. The proposed DBN model constitutes a significant step to improve the safety and reliability of flare systems in the oil and gas industry.

Redundancy allocation problem with a mixed strategy for a system with k-out-of-n subsystems and time-dependent failure rates based on Weibull distribution: An optimization via simulation approach

Reliability improvement for electronics and mechanical systems is vital for engineers in order to design of these systems. For this reason, there are many researches in this scope to help engineers in real world applications. One of the useful methods in reliability optimization is redundancy allocation problem (RAP). In the most previous works, the failure rates of system components are considered to be constant based on negative exponential distribution; whereas, nearly all systems in real world have components with time-dependent failure rates; i.e., the failure rates of system components will be changed time by time. In this paper, we have worked on a RAP for a system under k-out-of-n subsystems with time-dependent components failure rates based on Weibull distribution. Also, the redundancy policy of the proposed system is considered as mixed strategy and the optimization method was based on the simulation technique to obtain reliability function as implicit function. Finally, a branch and bound algorithm has been used to solve the model, exactly.

Investigation of PV Power Plant Structures Based on Monte Carlo Reliability and Economic Analysis

With the increasing deployment of photovoltaic (PV) sources in the power grid and their contribution to power generation, it is imperative to obtain accurate models for the reliability and stability of these plants. In this paper, a novel method is proposed for reliability assessment for the different structures involved in the implementation of PV plants, in which the failure rate of system components is calculated using the FIDES Guide standard, taking into account environmental conditions such as radiation curves, temperature, and humidity. Failure rates of the insulated gate bipolar transistor and converter capacitor were found to be greater than other components. After precise calculation of failure and repair rates, the probability of functioning in three states of full generation, partial failure, and down was obtained through Monte Carlo simulations. Considering the effect of the system's structure on its stability, the reliability of the system can be increased by adding inverter paths to its structure. Several such structures are proposed, and the most economical design is identified by analyzing load duration curves to obtain the energy loss in each configuration. The proposed algorithm was implemented in Isfahan University's 20 kW PV power plant. Simulations demonstrate the efficiency of the proposed algorithm in design and evaluation of economic system structures.

Self-monitoring electro-mechanical actuator for medium altitude long endurance unmanned aerial vehicle flight controls

This article deals with the reliability analysis and architecture definition of a fault-tolerant electro-mechanical actuator system for unmanned aerial vehicle applications. Starting from the basic layout of the flight control system of a medium altitude long endurance unmanned aerial vehicle, the attention is focused on the fault mode analysis of the single electro-mechanical actuator system, with the purpose of pointing out the effects of architectural choices on the system reliability. The electro-mechanical actuator system, developed to be a self-monitoring equipment, has three operating modes: normal, fail-operative and fail-safe. Reliability and safety budgets are quantitatively evaluated via fault tree analysis using typical failure rates of system components, and the most critical paths are identified and discussed.

Estimation of exponential component reliability from uncertain life data in series and parallel systems

Estimating reliability of components in series and parallel systems from masking system testing data has been studied. In this paper we take into account a second type of uncertainty: censored lifetime, when system components have constant failure rates. To efficiently estimate failure rates of system components in presence of combined uncertainty, we propose a useful concept for components: equivalent failure and equivalent lifetime. For a component in a system with known status and lifetime, its equivalent failure is defined as its conditional failure probability and its equivalent lifetime is its expectation of lifetime. For various uncertainty scenarios, we derive equivalent failures and test times for individual components in both series and parallel systems. An efficient EM algorithm is formulated to estimate component failure rates. Two numerical examples are presented to illustrate the application of the algorithm.

Uncertainty in fault tree analysis: A fuzzy approach

In fault tree analysis, the uncertainties in the failure probability and/or failure rate of system components or basic events can be propagated to find the uncertainty in the overall system failure probability. The conventional approach is Monte-Carlo simulation by assuming a probability distribution for the failure probability. In addition, a new methodology based on fuzzy set theory is also being used in the fault tree analysis for quantifying the basic event uncertainty and for propagating it. However, identification of the components which contribute maximum to the system failure probability is also important in fault tree analysis. Similarly, ranking the components based on their contribution of uncertainty to the uncertainty of the system failure probability is also very important. This paper presents a comparative study of probabilistic and fuzzy methodologies for top event uncertainty evaluation. Further, it explains a new approach to rank the system components or basic events depending on (1) their contribution to the top event failure probability and (2) their uncertainty contribution to the uncertainty of the top event based on fuzzy set theory.

General computational method for performing availability analysis of power-system configurations

The paper presents a general computational method and the relevant computer program which can be easily used to perform availability/unavailability analysis on power-system configurations. The mathematical availability formulation of the program is based primarily on: the tie sets (or cut sets) of the system configuration, the component failure rates and repair and maintenance times, some aspects of a Markov model of two states and the functional block concept. A real prerequisite for the successful utilisation of the program is the availability of realistic statistical data for the system components. For purposes of illustration, the computer program has been applied to evaluate the availability of two practical high-voltage/medium-voltage (HV/MV) substation configurations, from the standpoint of design, practical functionality and repair and maintenance procedures. The program is suitable in performing system availability/unavailability sensitivity analysis, based on value variations of system-component failure rates and repair and maintenance times.

Ion Propulsion Flight Experience, Life Tests, and Reliability Estimates

The application of low-thrust ion propulsion systems to space missions requires long duration (~ 5,000-20,000 hr) component operation. Thus, components must be developed with wearout mean times to failure in excess of these required mission times. Furthermore, chance failures which occur during the useful life of components must be minimized. This paper makes an assessment of both early and wearout failure modes of ion propulsion systems by examining the results of existing developmental and long duration testing. Estimates of chance failure rates of system components are also presented along with design concepts which maximize total propulsion system reliability. I. Introduction B ECAUSE of the long time operation required for most space applications, ion propulsion system reliability is a major concern. For this reason, the long duration and space testing of critical components, subsystems, and systems associated with primary and auxiliary ion propulsion systems are of great importance. It should be recognized, however, that although a large number of long duration tests have been conducted to date on ion propulsion systems, subsystems, and components, these tests have been part of a technology development phase and are not to be considered statistical reliability testing of fully developed systems. Thus, even though space-qualified ion propulsion systems are becoming available, system reliability can only be inferred from the results of past and present developmental testing and estimated by analytical techniques.