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Featured researches published by F. Ortiz.


IEEE Electrical Insulation Magazine | 2016

Health indexes for power transformers: a case study

F. Ortiz; Inmaculada Fernández; A. Ortiz; C.J. Renedo; F. Delgado; Cristina Fernández

Proper operation of power transformers is critical to ensuring transmission and distribution of electrical power. Most transformers have an electrical insulation system based on oil and paper. The state of the insulation system is the major factor influencing the state of the transformer. During service the dielectric materials within the transformer deteriorate, and small concentrations of impurities such as water, carbon monoxide, carbon dioxide, and furan compounds accumulate in the oil. Since it is easy to obtain oil samples from power transformers, the information most commonly collected by transformer fleet managers relates to the physical and dielectric properties of the oil. These properties include dielectric strength, dissipation factor, color, interfacial tension, and concentrations of dissolved gases, furans, acids, and moisture. Using these properties it is possible to determine whether a transformer has developed certain specific faults, e.g., partial discharges, arcing, sparking, overheating, etc. On the other hand, various health indexes have been proposed to characterize the general condition of a transformer [1]-[3]. The factors taken into account in these indexes vary, and are given different statistical weightings depending on their influence on the general condition of the transformer. In this article we evaluate the condition of a fleet of operating power transformers, using two recently proposed health indexes, and compare the results.


IEEE Transactions on Dielectrics and Electrical Insulation | 2017

Numerical analysis of the hot-spot temperature of a power transformer with alternative dielectric liquids

Agustín Santisteban; F. Delgado; A. Ortiz; Inmaculada Fernández; C.J. Renedo; F. Ortiz

The assessment of two vegetal oils as coolant in Low Voltage Winding of a power transformer with zigzag cooling have been analyzed. These dielectric fluids cooling performance has been compared with a typical mineral oil. To make the study, a 2D-axisymmetrical model of a power transformer has been developed to perform a numerical analysis using a Finite Element Method based software, COMSOL Multiphysics®. Some values are obtained in order to establish the comparison, such as hot-spot temperature or hot-spot factor. Moreover, the influence of the increase of the number of passes of the cooling circuit on the hot-spot temperature has been evaluated for all liquids and compared with the initial design. Results obtained in this work show that the hot-spot temperature is lower for the vegetal oils in the initial design. Furthermore, an increase in the number of passes affect more positively to the mineral oil since similar values of the hot-spot temperature for all liquids are obtained. Values of the hot-spot factor indicates that higher number of passes leads to lower efficient cooling circuits owing to the increase of the pressure drop although the hot-spot temperature decreases.


electrical insulation conference | 2015

Thermal analysis of transformers insulation based on vegetable esters

F. Delgado; Inmaculada Fernández; F. Ortiz; C.J. Renedo; A. Ortiz; J. Carcedo

This paper presents an analysis of the thermal performance experienced by dielectric materials inside power transformers. In this case the materials studied were mineral oil, vegetable ester and kraft paper. Two basic issues on the performance of insulation systems are their cooling capacity and their degradation rate. Thus two research lines have been considered: the first one is based on the assessment of the temperature and velocity distributions of the oil in the transformers cooling channels, being the second aim the measurement of the degree of polymerization of the dielectric paper, a key parameter that is used to estimate the remaining life of power transformers. The first objective was approached by CFD simulations of real transformer geometries. For the second goal, a thermal aging experiment has been implemented in the laboratory. These two perspectives are closely related since high temperature accelerates aging of the dielectric system of these machines.


Applied Thermal Engineering | 2016

Thermal degradation assessment of Kraft paper in power transformers insulated with natural esters

Inmaculada Fernández; F. Delgado; F. Ortiz; A. Ortiz; Cristina Fernández; C.J. Renedo; Agustín Santisteban


Applied Thermal Engineering | 2014

Post-mortem estimation of temperature distribution on a power transformer: Physicochemical and mechanical approaches

J. Carcedo; Inmaculada Fernández; A. Ortiz; Isidro Carrascal; F. Delgado; F. Ortiz; A. Arroyo


Renewable energy & power quality journal | 2016

Estimating the age of power transformers using the concentration of furans in dielectric oil

F. Ortiz; Cristina Fernández; Agustín Santisteban; F. Delgado; A. Ortiz


Forests | 2016

Strategies to Combat Mycosphaerella Leaf Disease in Eucalyptus globulus Plantations in Northern Spain

S. Pérez; C.J. Renedo; A. Ortiz; F. Ortiz; C. Tejedor


Archive | 2018

Assessment of Dielectric Paper Degradation through Mechanical Characterisation

Cristina Fernández-Diego; Inmaculada Fernández; F. Ortiz; Isidro Carrascal; C.J. Renedo; F. Delgado


Archive | 2018

Thermal Modelling of Electrical Insulation System in Power Transformers

Agustín Santisteban; F. Delgado; A. Ortiz; C.J. Renedo; F. Ortiz


Applied Thermal Engineering | 2018

The aging impact on the cooling capacity of a natural ester used in power transformers

A. Ortiz; F. Delgado; F. Ortiz; Inmaculada Fernández; Agustín Santisteban

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A. Ortiz

University of Cantabria

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F. Delgado

University of Cantabria

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C.J. Renedo

University of Cantabria

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J. Carcedo

University of Cantabria

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A. Arroyo

University of Cantabria

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S. Pérez

University of Cantabria

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