Finding a Zipf distribution and cascading propagation metric in utility line outage data

Observed transmission line outage data is grouped into successive generations of events. The empirical distribution of the number of generations in the cascades follows a Zipf distribution that implies the increasing propagation as cascades progress. The slope of the Zipf distribution gives a System Event Propagation Slope Index (SEPSI). This new metric quantifies the cascade propagation, varies as expected, and determines the probabilities of small, medium, and large cascades

Applying a formula for generator redispatch to damp interarea oscillations using synchrophasors

If an interarea oscillatory mode has insufficient damping, generator redispatch can be used to improve its damping. We explain and apply a new analytic formula for the modal sensitivity to rank the best pairs of generators to redispatch. The formula requires some dynamic power system data and we show how to obtain that data from synchrophasor measurements. The application of the formula to damp interarea modes is explained and illustrated with interarea modes of the New England 10-machine power system.Comment: To appear in IEEE Transactions on Power Systems, accepted September 201

Cascading Power Outages Propagate Locally in an Influence Graph that is not the Actual Grid Topology

In a cascading power transmission outage, component outages propagate non-locally, after one component outages, the next failure may be very distant, both topologically and geographically. As a result, simple models of topological contagion do not accurately represent the propagation of cascades in power systems. However, cascading power outages do follow patterns, some of which are useful in understanding and reducing blackout risk. This paper describes a method by which the data from many cascading failure simulations can be transformed into a graph-based model of influences that provides actionable information about the many ways that cascades propagate in a particular system. The resulting "influence graph" model is Markovian, in that component outage probabilities depend only on the outages that occurred in the prior generation. To validate the model we compare the distribution of cascade sizes resulting from $n-2$ contingencies in a $2896$ branch test case to cascade sizes in the influence graph. The two distributions are remarkably similar. In addition, we derive an equation with which one can quickly identify modifications to the proposed system that will substantially reduce cascade propagation. With this equation one can quickly identify critical components that can be improved to substantially reduce the risk of large cascading blackouts.Comment: Accepted for publication at the IEEE Transactions on Power System

The persistent vegetative state: legal and ethical issues

Recent advances in technology and medical expertise have enabled doctors to prolong the lives of many severely injured patients who only a few years ago would have died from their injuries. The prolongation of life by such measures has raised many legal, ethical and social issues. When in 1992 the House of Lords determined in Airdale NHS Trust V Bland that life-supporting measures, including artificial nutrition and hydration (ANH) might lawfully be withdrawn from Anthony Bland, a patient in a persistent vegetative state (PVS), attention was focused on these issues particularly as they apply to the patient in PVS. Since the PVS patient is neither competent to refuse treatment, nor is he dying or suffering, the reasons normally advanced for withdrawing life-supporting measures do not apply. In Bland, their Lordships relied on the best interests test laid down in Re F (mental patient: sterilisation) [1989] 2 All ER 545, and, with the exception of Lord Mustill, on the Bolam test (Bolam v Friern Barnet Hospital Management Committee) [1957] 1 WLR 582. This thesis examines the decision mBland and addresses some of the issues raised. The appropriateness of the best interests test as applied to the patient in PVS is explored and compared with the approach of substituted judgement employed in some other common law jurisdictions. The relevance of the Bolam test to decisions regarding the withdrawal of life-supporting measures is considered. The legal requirements for the withdrawal of ANH are discussed, together with the ethical debate and the moral dilemmas posed by its withdrawal. Finally, the question as to whether the decision in Bland is good law is addressed, and it will be argued that whilst it may be morally acceptable to withdraw ANH from some patients, as regards a patient in PVS, the moral imperative is that we should not

'POWs and purge victims: attitudes towards party rehabilitation, 1956-57'

In the wake of Stalin's death in 1953 and Khrushchev's Secret Speech three years later, many Soviet citizens hoped that past injustices would now be put right. For some, this meant the right to rejoin the Communist Party. This article explores how former party members - including many returning from the camps - sought rehabilitation in the years 1956 to 1957. Focusing in particular on the party organization in Vladimir province, the article examines the differing ways POWs and purge victims were treated, and asks how far the decisions made by the party elite in this oblast' reflected central policy or local concerns