An overview of the reliability metrics for power grids and telecommunication networks

Power grids deliver energy, and telecommunication networks transmit information. These two facilities are critical to human society. In this study, we conduct a comprehensive overview of the development of reliability metrics for power grids and telecommunication networks. The main purpose of this review is to promote and support the formulation of communication network reliability metrics with reference to the development of power grid reliability. We classify the metrics of power grid into the reliability of power distribution and generation/transmission and the metrics of telecommunication network into connectivity-based, performance-based, and state-based metrics. Then, we exhibit and discuss the difference between the situations of the reliability metrics of the two systems. To conclude this study, we conceive a few topics for future research and development for telecommunication network reliability metrics.     

Improved resilience measure for component recovery priority in power grids

Given the complexity of power grids, the failure of any component may cause large-scale economic losses. Consequently, the quick recovery of power grids after disasters has become a new research direction. Considering the severity of power grid disasters, an improved power grid resilience measure and its corresponding importance measures are proposed. The recovery priority of failed components after a disaster is determined according to the influence of the failed components on the power grid resilience. Finally, based on the data from the 2019 Power Yearbook of each city in Shandong Province, China, the power grid resilience after a disaster is analyzed for two situations, namely, partial components failure and failure of all components. Result shows that the recovery priorities of components with different importance measures vary. The resilience evaluations under different repair conditions prove the feasibility of the proposed method.     

A new combinatorial model for deterministic competing failure analysis

Components in many engineering and industrial systems can experience propagated failures, which not only cause the failure of the component itself but also affect other components, causing extensive damage to the entire system. However, in systems with functional dependence behavior where failure of a trigger component may cause other components (referred to as dependent components) to become unusable or inaccessible, failure propagation originating from a dependent component could be isolated if the corresponding trigger component fails first. Thus, a time-domain competition exists between the failure propagation effect and the failure isolation effect, which poses a great challenge to the system reliability modeling and analysis. In this work, a new combinatorial model called competing binary decision diagram (CBDD) is proposed for the reliability analysis of systems subject to the competing failure behavior. In particular, special Boolean algebra rules and logic manipulation rules are developed for system CBDD model generation. The corresponding evaluation algorithm for the constructed CBDD model is also proposed. The proposed CBDD modeling method has no limitation on the type of component time-to-failure distributions. A memory system example and a network example are provided to demonstrate the application of the proposed model and algorithms. Correctness of the proposed method is verified using the Markov method.     

Block diagram method for analyzing multi-state systems with uncovered failures

The paper suggests a modification of the generalized reliability block diagram (RBD) method for evaluating reliability and performance indices of multi-state systems with uncovered failures. Such systems (or their subsystems) can fail to perform their task in the case of undetected failure of any one of their elements. Examples of this effect can be found in computing systems, electrical power distribution networks, pipe lines carrying dangerous materials etc. The suggested method based on a universal generating function technique allows performance distribution of complex multi-state series-parallel system with uncovered failures to be obtained using a straightforward recursive procedure. Illustrative examples are presented.     

Statistical Inference for Power-Law Process With Competing Risks

The focus of this article is on failure history of a repairable system for which the relevant data comprise successive event times for a recurrent phenomenon along with an event-count indicator. We undertake an investigation for analyzing failures from repairable systems that are subject to multiple failure modes. Failure data representing a cluster of recurrent events from a single system are studied under the parametric framework of a power-law process, a model that has found considerable attention in industrial applications. Some interesting and nonstandard asymptotic results ensue in this context that are discussed in detail. Extensive simulation has been carried out that supplements the theoretical findings. An extension to the case where the specific cause of failure may be missing is investigated in detail. The methodology has been implemented on recurrent failure data obtained from a warranty claim database for a fleet of automobiles. Supplementary material for this article is available online.     

A functional failure reasoning methodology for evaluation of conceptual system architectures

In this paper, we introduce a new methodology for reasoning about the functional failures during early design of complex systems. The proposed approach is based on the notion that a failure happens when a functional element in the system does not perform its intended task. Accordingly, a functional criticality is defined depending on the role of functionality in accomplishing designed tasks. A simulation-based failure analysis tool is then used to analyze functional failures and reason about their impact on overall system functionality. The analysis results are then integrated into an early stage system architecture analysis framework that analyzes the impact of functional failures and their propagation to guide system-level architectural design decisions. With this method, a multitude of failure scenarios can be quickly analyzed to determine the effects of architectural design decisions on overall system functionality. Using this framework, design teams can systematically explore risks and vulnerabilities during the early (functional design) stage of system development prior to the selection of specific components. Application of the presented method to the design of a representative aerospace electrical power system (EPS) testbed demonstrates these capabilities.     

Progressive failure analysis for advanced grid stiffened composite plates/shells

A progressive failure methodology is developed to simulate the initiation and propagation of multi-failure modes for advanced grid stiffened (AGS) composite plates/shells on the basis of a stiffened element model. Failures of both skin and ribs are taken into consideration, which are matrix cracking, fiber failure, fiber–matrix shear failure, delamination in skin and fiber failure in rib. All these failures are defined using a set of 2-D stress-based polynomial failure criteria wherein the transverse shear stresses at centroid of the stiffened element are calculated by employing an integrated approach of finite element and finite difference method. Corresponding material and stiffness degradation behavior is introduced after the initiation of individual failure mechanisms. The progressive failure behavior of a composite orthotropic-grid curved panel with a centrally located cutout under compressive load is evaluated using the method.     

多馈入直流输电系统换相失败研究综述

常规高压直流输电系统存在换相失败的风险。对于多馈入直流输电系统而言,由于各交直流系统间的互相作用影响,单个直流回路发生换相失败可能会引起多条直流回路同时或者相继发生换相失败,给电网的安全稳定运行带来威胁。从换相失败的机理出发,引入多馈入交互作用因子来分析多馈入直流输电系统发生换相失败的影响因素和判据,总结了目前抑制换相失败的手段和策略,最后指出了在数学模型、换相失败耦合机理和抑制措施方面值得更深入的探讨和研究。     

火电机组EH油管道泄漏典型案例分析及防范措施

汽轮机EH油系统管道连接供油系统、危急遮断系统与执行机构构成整个回路,其作为油介质的传输通道,一旦发生泄漏,将直接造成发电机组非计划停运,让企业蒙受巨大的经济效益与社会效益损失。针对某集团公司近期火电机组发生的多起EH油管道泄漏案例,从金属材料角度概括了EH油管道常见的几类失效机制,并结合每个典型案例,对失效分析过程及要点做了简单介绍,重点从技术监督角度提出了治理和防范措施,具体到相应的检查方法和检查内容,切合现场,以供借鉴。     

Application of the state transition sampling technique to system reliability evaluation

Monte Carlo simulation is becoming an attractive alternative to analytical approaches for reliability evaluation in large electric power systems. Monte Carlo simulation is generally more flexible than an analytical technique when complex operating conditions and system considerations such as multi-derated states, chronology, reservoir operating rules, bus load uncertainty and weather effects need to be incorporated. Monte Carlo techniques are usually classified as being either a sequential or non-sequential method. The basic non-sequential Monte Carlo approach is known as the state sampling method in which the actual frequency of failure is estimated from the number of failures encountered during the simulation process. The actual frequency of failure can be more accurately obtained by using a sequential approach which models the component up and down cycles together with the system load. This paper presents and illustrates the application of the state transition sampling technique. This method can be used to estimate the actual frequency index without requiring an additional enumeration procedure or sampling the component up and down cycles and storing chronological information on the overall state of the system. In this approach the next system state is obtained by allowing a component to undergo transitions from its present state. The procedure focuses on transitions of the whole system rather than on component states or state durations. This technique is usually much faster than the traditional sequential simulation approach. The state transition sampling technique will be illustrated by application to generating capacity and composite generation and transmission system reliability assessment in a representative electric power system. © 1997 John Wiley & Sons, Ltd.     

Preventing failure in IT-enabled systems for supply chain management

Supply chain management (SCM) emphasises the overall and long-term benefit of all parties on the chain through cooperation and information sharing. This signifies the importance of communication and the application of IT-enabled systems in SCM. A supply chain management information system (SCMIS) is usually user-interfaced and designed to provide information and information processing capability to support the strategy, operations, management analysis, and decision-making functions in an organisation's supply network. SCMIS provides high quality, relevant and timely information flow that effectively supports decision-making for inventory replenishment, capacity activation, and for synchronising material flows at all tiers within the supply chain. In recent years, there have been some efforts on designing efficient information systems for supply chain management; but many of them have led to failure. Using a critical failure factor (CFF) approach and based on a perfect study, we investigate this crucial issue in-depth and put forward feasible solutions regarding failure prevention in such systems throughout this article. Three main purposes of this paper are to: (1) identify SCMIS and its characteristics, (2) introduce and categorise the critical failure factors of SCM and SCMIS, and (3) investigate the explanatory power of these CFFs on the performance of supply channel processes performed through SCMIS.     

一种新型球面等积六边形网格系统生成算法

分析了构建球面等积网格系统的基本原理和常用剖分方法的特点,提出了在二十面体展开图上对顶点和面统一编码的研究思路,将两个相邻三角面合并为一个四边形并建立坐标系描述孔径为4的新型递归剖分网格,最后借助施奈德等积多面体投影将平面网格映射到球面,得到了将孔径为4的等积六边形剖分产生的球面网格系统ISEA4H-3.实验结果表明,用这种算法生成的ISEA4H-3网格的几何属性优于现有球面六边形网格,更适用于海量空间信息管理,具有较强的应用价值.     

Biased Monte Carlo unavailability analysis for systems with time-dependent failure rates

In this paper we consider systems made of components with time-dependent failure rates. A proper analysis of the time-dependent failure behaviour is very important for considerations of life-extension of safety critical systems such as nuclear power plants. This problem is tackled by Monte Carlo simulation which does not suffer from the additional complexity introduced by the model parameters' time inhomogeneity.The high reliability of the systems typically encountered in practice entails resorting to biasing techniques for favouring the events of interest. In this work, we investigate the possibility of biasing the system failures to be distributed in time according to exponential laws. The drawbacks encountered in such procedure have driven us towards the adoption of biasing schemes relying on uniform distributions which distribute failures over the system life more evenly.     

An analysis of safety-critical digital systems for risk-informed design

This paper quantitatively presents the results of a case study which examines the fault tree analysis framework of the safety of digital systems. The case study is performed for the digital reactor protection system of nuclear power plants. The broader usage of digital equipment in nuclear power plants gives rise to the need for assessing safety and reliability because it plays an important role in proving the safety of a designed system in the nuclear industry. We quantitatively explain the relationship between the important characteristics of digital systems and the PSA result using mathematical expressions. We also demonstrate the effect of critical factors on the system safety by sensitivity study and the result which is quantified using the fault tree method shows that some factors remarkably affect the system safety. They are the common cause failure, the coverage of fault tolerant mechanisms and software failure probability.     

Modeling and Simulation of Electrical System in More Electric Civil Aircraft Considering Faults

Based on the integrated design and airworthiness verification of civil aircraft system,this paper completes the simulation modeling and fault modeling of aircraft electrical system. The aircraft electrical system is constructed in the form of dual generators and dual-channel power supply. The main power supply adopts the three-stage power generation system,the auxiliary power supply system uses the permanent magnet synchronous power generation system and a battery. The transmission and distribution system is responsible for the electrical power conversion and the logic control in the system fault-pattern. The simulation results show that the system is reasonable and effective,which provides a reference for the optimal design and control of the actual aircraft electrical system.     

Statistical evaluation of lightning-related failures for the optimal location of surge arresters on the power networks

Direct lightning strokes cause unscheduled supply interruptions in power systems because of a failure of the insulation. Metal oxide surge arresters, as a proper protective device, have been widely adopted in power systems to reduce lightning initiated flashovers and, hence, increase the power quality and reliability of the systems. Based on a genetic algorithm approach, a cost effective solution is described to find the optimum location of surge arresters on a power network in order to minimise the global risk of the network, and to improve its reliability. A statistical approach to evaluate lightning failures has been introduced and an optimisation procedure developed to analyse the network in order to satisfy the power utility requirement for a specific value of risk and/or line performance with a minimum set of arresters, that is, at minimum cost. Not only the insulation flashover but also the failure of the arrester can affect the reliability of power systems. Therefore, both the failure of the insulation and that of the arrester are considered in the proposed method.     

A method for analysing the reliability of a transmission grid

The paper describes a probabilistic method for transmission grid security evaluation. Power system security is the ability of the power system to withstand sudden disturbances such as short circuits. The method presented here uses event and fault trees and combines them with power system dynamic simulations. Event trees model the substation protection and trip operations after line faults. Different event tree end states (fault duration, circuit breaker trips) are simulated with power system dynamic analysis program. The dynamic analysis results (power system post-fault states) are then classified into secure, alert, emergency and system breakdown. The probabilities, minimal cut sets and grid level importance measures (Fussell-Vesely, risk increase and decrease factors) are calculated for the total and partial system breakdown. In this way, the relative importance of the substation devices regarding to the system breakdown can be reached. Also the more and less likely contributing factors to system breakdown are received. With this method, an existing 400 kV transmission grid with its line fault and device failure statistics is analysed.     

EFSIM: An integrated circuit early failure simulator

Early failures are the dominant concern as integrated circuit technology matures into consistently producing systems of high reliability. These failures are attributed to the presence of randomly occurring defects in elementary objects (contacts, vias, metal runs, gate oxides, bonds etc.) that result in extrinsic rather than intrinsic (wearout-related) mortality. A model relating system failure to failure at the elementary object level has been developed. Reliability is modelled as a function of circuit architecture, mask layout, material properties, life-test data, worst-case use-conditions and the processing environment. The effects of competing failure mechanisms, and the presence of redundant sub-systems are accounted for. Hierarchy is exploited in the analysis, allowing large scale designs to be simulated. Experimental validation of the modelling of oxide leakage related failure, based on a correlation between actual failures reported for a production integrated circuit and Monte Carlo simulations that incorporate wafer-level test results and process defect monitor data, is presented. The state of the art in IC reliability simulation is advanced in that a methodology that provides the capability to design-in reliability while accounting for early failures has been developed; applications include process qualification, design assessment and fabrication monitoring.     

Purple plague: Eliminated or just forgotten?

The reappearance of ‘purple plague’ as a reliability and failure risk in current IC devices has led to renewed interest in the precise failure mechanisms and eventual failure mode. These are outlined and illustrated with examples of recent failures in plastic encapsulated integrated circuits, hermetically sealed integrated circuits and hybrids. The reasons for the reappearance of this type of failure are discussed, and it is shown that the problem may be expected to increase in future generation devices.     

An integrated methodology for the dynamic performance and reliability evaluation of fault-tolerant systems

We propose an integrated methodology for the reliability and dynamic performance analysis of fault-tolerant systems. This methodology uses a behavioral model of the system dynamics, similar to the ones used by control engineers to design the control system, but also incorporates artifacts to model the failure behavior of each component. These artifacts include component failure modes (and associated failure rates) and how those failure modes affect the dynamic behavior of the component. The methodology bases the system evaluation on the analysis of the dynamics of the different configurations the system can reach after component failures occur. For each of the possible system configurations, a performance evaluation of its dynamic behavior is carried out to check whether its properties, e.g., accuracy, overshoot, or settling time, which are called performance metrics, meet system requirements. Markov chains are used to model the stochastic process associated with the different configurations that a system can adopt when failures occur. This methodology not only enables an integrated framework for evaluating dynamic performance and reliability of fault-tolerant systems, but also enables a method for guiding the system design process, and further optimization. To illustrate the methodology, we present a case-study of a lateral-directional flight control system for a fighter aircraft.