Advanced transformer condition assessment – Part I

Infrared Thermography, Ultrasonic Noise Analysis, Partial Discharge Detection, Dissolved Gas Analysis, Vibration Analysis – all these techniques are great stand-alone diagnostic tools; however, when used properly, combining the data obtained through each technique, an incipient fault can be identified long before it degrades the insulation and creates a failure. This paper will provide guidance in setting up a complete Predictive Maintenance program to be able to provide owners of oil-filled power transformers (4 kV and up), i.e. utilities, refineries, military, mining, etc., with a complete health report and condition assessment of critical oil-filled power transformers and ancillary substation components. The testing described in this paper is done on energized, fully loaded transformers. Author’s vast experience with doing Partial Discharge testing reveals that nearly 80 % of all oil-filled power transformers exhibit some PD. This low level PD activity is not detrimental to the health of the transformer. It is usually a burr or sharp corner that is producing the activity. I consider this just nuisance PD and most times it continues for the entire life of a transformer without a failure related to PD

Advanced transformer condition assessment – Part II

Infrared Thermography, Ultrasonic Noise Analysis, Partial Discharge Detection, Dissolved Gas Analysis, Vibration Analysis – all these techniques are great stand-alone diagnostic tools; however, when used properly, combining the data obtained through each technique, an incipient fault can be identified long before it degrades the insulation and creates a failure. This paper will provide guidance in setting up a complete Predictive Maintenance program to be able to provide owners of oil-filled power transformers (4 kV and up), i.e. utilities, refineries, military, mining, etc., with a complete health report and condition assessment of critical oil-filled power transformers and ancillary substation components. The testing described in this paper is done on energized, fully loaded transformers. Author’s vast experience with doing Partial Discharge testing reveals that nearly 80 % of all oil-filled power transformers exhibit some PD. This low level PD activity is not detrimental to the health of the transformer. It is usually a burr or sharp corner that is producing the activity. I consider this just nuisance PD and most times it continues for the entire life of a transformer without a failure related to PD

Electromagnetic induction in non-uniform domains

Kinematic simulations of the induction equation are carried out for different setups suitable for the von-K\'arm\'an-Sodium (VKS) dynamo experiment. Material properties of the flow driving impellers are considered by means of high conducting and high permeability disks that are present in a cylindrical volume filled with a conducting fluid. Two entirely different numerical codes are mutually validated by showing quantitative agreement on Ohmic decay and kinematic dynamo problems using various configurations and physical parameters. Field geometry and growth rates are strongly modified by the material properties of the disks even if the high permeability/high conductivity material is localized within a quite thin region. In contrast the influence of external boundary conditions remains small. Utilizing a VKS like mean fluid flow and high permeability disks yields a reduction of the critical magnetic Reynolds number for the onset of dynamo action of the simplest non-axisymmetric field mode. However this decrease is not sufficient to become relevant in the VKS experiment. Furthermore, the reduction of Rm_c is essentially influenced by tiny changes in the flow configuration so that the result is not very robust against small modifications of setup and properties of turbulence

Reporte de investigaci?n: la organizaci?n del sector p?blico peruano

Sistematiza los avances sobre la investigaci?n de la organizaci?n del sector p?blico peruano desarrollada por el Proyecto de Gesti?n P?blica de ESAN entre 1983 y 1985, considerando que el conocimiento del Estado y la administraci?n p?blica es condici?n necesaria para actuar en el perfeccionamiento profesional de los directivos y en el cambio administrativo. La primera parte presenta el enfoque y la metodolog?a utilizados, la segunda est? dedicada a diversas ?reas exploradas: a) el empleo y el mercado laboral y su relaci?n con la organizaci?n del sector p?blico; b) el perfil social de los directivos del sector p?blico, a partir de los estudios sobre los directivos que renunciaron al sector p?blico en 1978 y los directivos encuestados en 1984, as? como las caracter?sticas del funcionario p?blico y sus orientaciones en relaci?n con los fines del Estado; c) algunos problemas de gesti?n, en funci?n de los planes y las pol?ticas en las organizaciones reguladoras y empresariales del sector p?blico, y las relaciones de las corporaciones de desarrollo con la administraci?n p?blica; d) la organizaci?n del sector p?blico y la funci?n p?blica, abordadas desde el punto de vista legal, por un lado, y en t?rminos del organigrama y de las funciones, por otro; e) el an?lisis de los trabajos realizados en torno a la problem?tica de la administraci?n p?blica. El reporte concluye con lo que se considera una necesaria advertencia respecto a los problemas de la administraci?n p?blica y la necesidad de estudiarlos con el prop?sito de encontrar las soluciones m?s adecuadas a una cuesti?n que tiene indudable gravitaci?n en la vida nacional

La escuela como espacio de aprendizaje de identidades ciudadanas modernas e intercu lturales: ser limeños, ser señoritas, ser japones

¿Cuáles son las aspiraciones de los padres al colocar a sus hijos e hijas en determinada escuela? Tal vez esperan un determinado tipo de socialización útil para el desempeño posterior de sus hijas e hijos como adultos. En esta ponencia haré un análisis inicial tanto de las entrevistas a varios alumnos y alumnas de cinco distintos colegios de Lima, como de los Proyectos Educativos Institucionales (PEI) de cada uno de estos colegios. El objetivo es comprender si los colegios elegidos por los padres para que sus hijos e hijas estudien allí, se debe por la importancia dada a los valores que promueve la escuela. Así mismo, busco reconocer desde la mirada de los propios alumnos y alumnas entrevistadas, qué es lo que ellos y ellas valoran y, por último, saber lo que el propio director propone a través del PEI. En conclusión, se trata de analizar el diálogo que se produce desde los diversos actores mencionados, desde sus historias socioculturales y desde sus aspiraciones culturales; saben que necesitan de la escuela como estrategia intercultural para el aprendizaje de nuevos códigos para la propia modernización de sus identidades limeñas, de señoritas y de japoneses, para así alcanzar una ciudadanía más solvente

The microgravity environment of the Space Shuttle Columbia payload bay during STS-32

Over 11 hours of three-axis microgravity accelerometer data were successfully measured in the payload bay of Space Shuttle Columbia as part of the Microgravity Disturbances Experiment on STS-32. These data were measured using the High Resolution Accelerometer Package and the Aerodynamic Coefficient Identification Package which were mounted on the Orbiter keel in the aft payload bay. Data were recorded during specific mission events such as Orbiter quiescent periods, crew exercise on the treadmill, and numerous Orbiter engine burns. Orbiter background levels were measured in the 10(exp -5) G range, treadmill operations in the 10(exp -3) G range, and the Orbiter engine burns in the 10(exp -2) G range. Induced acceleration levels resulting from the SYNCOM satellite deploy were in the 10 (exp -2) G range, and operations during the pre-entry Flight Control System checkout were in the 10(exp -2) to 10(exp -1) G range

Analytic results and weighted Monte Carlo simulations for CDO pricing

We explore the possibilities of importance sampling in the Monte Carlo pricing of a structured credit derivative referred to as Collateralized Debt Obligation (CDO). Modeling a CDO contract is challenging, since it depends on a pool of (typically about 100) assets, Monte Carlo simulations are often the only feasible approach to pricing. Variance reduction techniques are therefore of great importance. This paper presents an exact analytic solution using Laplace-transform and MC importance sampling results for an easily tractable intensity-based model of the CDO, namely the compound Poissonian. Furthermore analytic formulae are derived for the reweighting efficiency. The computational gain is appealing, nevertheless, even in this basic scheme, a phase transition can be found, rendering some parameter regimes out of reach. A model-independent transform approach is also presented for CDO pricing.Comment: 12 pages, 9 figure

The CERESIS earthquake catalogue and database of the Andean Region: background, characteristics and examples of use

The history of earthquakes in South America starts with the coming of the Spanish and Portuguese «conquistadores» at the beginning of the 16th century. Their chronicles, and those of local historians, are the only source of earthquake information for the following 400 years. The creation of the Regional Centre for Seismology for South America (CERESIS) was a major factor for homogenous regional progress, in that CERESIS promoted the implementation of the first unified earthquake catalogue and database for the whole Andean Region. This paper reviews basic information about the intensity database and the focal parameter catalogues proposed by CERESIS in 1985. Further macroseismic data available from the CERESIS database (earthquakes with I0 = 8) are used to obtain preliminary results for the earthquake source parameters of selected South American historical events. The case of the Great Earthquake of the Venezuelan Andes, 29 April 1894, is presented in some detail

Influence of high permeability disks in an axisymmetric model of the Cadarache dynamo experiment

Numerical simulations of the kinematic induction equation are performed on a model configuration of the Cadarache von-K\'arm\'an-Sodium dynamo experiment. The effect of a localized axisymmetric distribution of relative permeability {\mu} that represents soft iron material within the conducting fluid flow is investigated. The critical magnetic Reynolds number Rm^c for dynamo action of the first non-axisymmetric mode roughly scales like Rm^c({\mu})-Rm^c({\mu}->infinity) ~ {\mu}^(-1/2) i.e. the threshold decreases as {\mu} increases. This scaling law suggests a skin effect mechanism in the soft iron disks. More important with regard to the Cadarache dynamo experiment, we observe a purely toroidal axisymmetric mode localized in the high permeability disks which becomes dominant for large {\mu}. In this limit, the toroidal mode is close to the onset of dynamo action with a (negative) growth-rate that is rather independent of the magnetic Reynolds number. We qualitatively explain this effect by paramagnetic pumping at the fluid/disk interface and propose a simplified model that quantitatively reproduces numerical results. The crucial role of the high permeability disks for the mode selection in the Cadarache dynamo experiment cannot be inferred from computations using idealized pseudo-vacuum boundary conditions (H x n = 0).Comment: 16 pages, 9 Figures, published in New Journal of Physics 14(2012), 05300

Systemic Risk and Default Clustering for Large Financial Systems

As it is known in the finance risk and macroeconomics literature, risk-sharing in large portfolios may increase the probability of creation of default clusters and of systemic risk. We review recent developments on mathematical and computational tools for the quantification of such phenomena. Limiting analysis such as law of large numbers and central limit theorems allow to approximate the distribution in large systems and study quantities such as the loss distribution in large portfolios. Large deviations analysis allow us to study the tail of the loss distribution and to identify pathways to default clustering. Sensitivity analysis allows to understand the most likely ways in which different effects, such as contagion and systematic risks, combine to lead to large default rates. Such results could give useful insights into how to optimally safeguard against such events.Comment: in Large Deviations and Asymptotic Methods in Finance, (Editors: P. Friz, J. Gatheral, A. Gulisashvili, A. Jacqier, J. Teichmann) , Springer Proceedings in Mathematics and Statistics, Vol. 110 2015