Prediction of remaining life of power transformers based on left truncated and right censored lifetime data

Prediction of the remaining life of high-voltage power transformers is an important issue for energy companies because of the need for planning maintenance and capital expenditures. Lifetime data for such transformers are complicated because transformer lifetimes can extend over many decades and transformer designs and manufacturing practices have evolved. We were asked to develop statistically-based predictions for the lifetimes of an energy company's fleet of high-voltage transmission and distribution transformers. The company's data records begin in 1980, providing information on installation and failure dates of transformers. Although the dataset contains many units that were installed before 1980, there is no information about units that were installed and failed before 1980. Thus, the data are left truncated and right censored. We use a parametric lifetime model to describe the lifetime distribution of individual transformers. We develop a statistical procedure, based on age-adjusted life distributions, for computing a prediction interval for remaining life for individual transformers now in service. We then extend these ideas to provide predictions and prediction intervals for the cumulative number of failures, over a range of time, for the overall fleet of transformers.Comment: Published in at http://dx.doi.org/10.1214/00-AOAS231 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

When organisational effectiveness fails: business continuity management and the paradox of performance

Purpose: The aim of the paper is to consider the nature of the business continuity management (BCM) process and to frame it within wider literature on the performance of socio-technical systems. Despite the growth in BCM activities in organisations, some questions remain as to whether academic research has helped to drive this process. The paper seeks to stimulate discussion within this journal of the interplay between organisational performance and BCM and to frame it within the context of the potential tensions between effectiveness and efficiency. Design/methodology/approach: The paper considers how BCM is defined within the professional and academic communities that work in the area. It deconstructs these definitions in order to and set out the key elements of BCM that emerge from the definitions and considers how the various elements of BCM can interact with each other in the context of organisational performance. Findings: The relationships between academic research in the area of crisis management and the practice-based approaches to business continuity remain somewhat disjointed. In addition, recent work in the safety management literature on the relationships between success and failure can be seen to offer some interesting challenges for the practice of business continuity. Practical implications: The paper draws on some of the practice-based definitions of BCM and highlights the limitations and challenges associated with the construct. The paper sets out challenges for BCM based upon theoretical challenges arising in cognate areas of research. The aim is to ensure that BCM is integrated with emerging concepts in other aspects of the management of uncertainty and to do so in a strategic context. Originality/value: Academic research on performance reflects both the variety and the multi-disciplinary nature of the issues around measuring and managing performance. Failures in organisational performance have also invariably attracted considerable attention due to the nature of a range of disruptive events. The paper reveals some of the inherent paradoxes that sit at the core of the BCM process and its relationships with organisational performance

Review of recent research towards power cable life cycle management

Power cables are integral to modern urban power transmission and distribution systems. For power cable asset managers worldwide, a major challenge is how to manage effectively the expensive and vast network of cables, many of which are approaching, or have past, their design life. This study provides an in-depth review of recent research and development in cable failure analysis, condition monitoring and diagnosis, life assessment methods, fault location, and optimisation of maintenance and replacement strategies. These topics are essential to cable life cycle management (LCM), which aims to maximise the operational value of cable assets and is now being implemented in many power utility companies. The review expands on material presented at the 2015 JiCable conference and incorporates other recent publications. The review concludes that the full potential of cable condition monitoring, condition and life assessment has not fully realised. It is proposed that a combination of physics-based life modelling and statistical approaches, giving consideration to practical condition monitoring results and insulation response to in-service stress factors and short term stresses, such as water ingress, mechanical damage and imperfections left from manufacturing and installation processes, will be key to success in improved LCM of the vast amount of cable assets around the world

What lies beneath? The role of informal and hidden networks in the management of crises

Crisis management research traditionally focuses on the role of formal communication networks in the escalation and management of organisational crises. Here, we consider instead informal and unobservable networks. The paper explores how hidden informal exchanges can impact upon organisational decision-making and performance, particularly around inter-agency working, as knowledge distributed across organisations and shared between organisations is often shared through informal means and not captured effectively through the formal decision-making processes. Early warnings and weak signals about potential risks and crises are therefore often missed. We consider the implications of these dynamics in terms of crisis avoidance and crisis management

Warranty Data Analysis: A Review

Warranty claims and supplementary data contain useful information about product quality and reliability. Analysing such data can therefore be of benefit to manufacturers in identifying early warnings of abnormalities in their products, providing useful information about failure modes to aid design modification, estimating product reliability for deciding on warranty policy and forecasting future warranty claims needed for preparing fiscal plans. In the last two decades, considerable research has been conducted in warranty data analysis (WDA) from several different perspectives. This article attempts to summarise and review the research and developments in WDA with emphasis on models, methods and applications. It concludes with a brief discussion on current practices and possible future trends in WDA

Analysis of significant factors on cable failure using the Cox proportional hazard model

This paper proposes the use of the Cox proportional hazard model (Cox PHM), a statistical model, for the analysis of early-failure data associated with power cables. The Cox PHM analyses simultaneously a set of covariates and identifies those which have significant effects on the cable failures. In order to demonstrate the appropriateness of the model, relevant historical failure data related to medium voltage (MV, rated at 10 kV) distribution cables and High Voltage (HV, 110 kV and 220 kV) transmission cables have been collected from a regional electricity company in China. Results prove that the model is more robust than the Weibull distribution, in that failure data does not have to be homogeneous. Results also demonstrate that the method can single out a case of poor manufacturing quality with a particular cable joint provider by using a statistical hypothesis test. The proposed approach can potentially help to resolve any legal dispute that may arise between a manufacturer and a network operator, in addition to providing guidance for improving future practice in cable procurement, design, installations and maintenance

Five Questions about Demonstrating Impact

American foundations must do a better job of demonstrating the impact of their work, according to a dozen philanthropy leaders. In this Philanthropy Awareness Initiative Digest, they weigh in on how foundations can demonstrate impact and why they should. The stakes are high, the state of practice low. Consider it a wake-up call for the field

Innovation, competition and public procurement in the pre-commercial phase

Should the supply or the demand side bear the risk connected to innovation? The two polar cases identified in the literature are the supply push and the demand pull. The former is the typical one, with the supplier bearing the costs and obtaining the benefits from innovating. The latter is technology procurement, where the buyer takes the risk, by procuring the innovative good or service. With respect to this, pre-commercial procurement is a peculiar solution that can explain the debate found in the literature relative to its configuration either as a supply-side or a demand-side instrument. The separation from the commercial phase allows the procurer to take only (part of) the risks connected to R&D services. Also, competition among suppliers gives the opportunity of evaluating different solutions and to obtain, in the commercial phase, a lower price for the innovative good. The counterpart of all this is a large portion of risk being left to the supplier. As a consequence, suppliers need to obtain a larger share of the benefits of the innovation process. This economic reason, besides the legal restrictions on State aid, explains the need for a shared risks-shared benefits approach, centred on the agreements on the assignment of IPRs

Life After Being a Pathology Department Chair II: Lessons Learned.

The 2016 Association of Pathology Chairs annual meeting featured a discussion group of Association of Pathology Chairs senior fellows (former chairs of academic departments of pathology who have remained active in Association of Pathology Chairs) that focused on how they decided to transition from the chair, how they prepared for such transition, and what they did after the transition. At the 2017 annual meeting, the senior fellows (encompassing 481 years of chair service) discussed lessons they learned from service as chair. These lessons included preparation for the chairship, what they would have done differently as chair, critical factors for success as chair, factors associated with failures, stress reduction techniques for themselves and for their faculty and staff, mechanisms for dealing with and avoiding problems, and the satisfaction they derived from their service as chair. It is reasonable to assume that these lessons may be representative of those learned by chairs of other specialties as well as by higher-level academic administrators such as deans, vice presidents, and chief executive officers. Although the environment for serving as a department chair has been changing dramatically, many of the lessons learned by former chairs are still valuable for current chairs of any length of tenure