R and D Institute for Electrical Engineering ICPE CA

Bucharest, Romania

R and D Institute for Electrical Engineering ICPE CA

Bucharest, Romania
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Ciuriuc A.,Polytechnic University of Bucharest | Dumitran L.M.,Polytechnic University of Bucharest | Notingher P.V.,Polytechnic University of Bucharest | Badicu L.V.,OMICRON Energy Solutions GmbH | And 4 more authors.
Proceedings of the 2016 IEEE International Conference on Dielectrics, ICD 2016 | Year: 2016

In this paper the results of an experimental study concerning the vegetable and mineral oil impregnated paper subjected to thermal ageing is presented. Using activation energy method, the paper lifetime is calculated. Samples of vegetable and mineral oil impregnated paper were aged at 155 °C. Dielectric properties, water content and degree of polymerization of aged samples were measured. Using the activation energy for paper degradation calculated from DSC (Differential Scanning Calorimetry) data, the lifetime curves were drawn and hence the lifetime values at different operating temperatures were calculated. It was observed that the lifetime values are higher for vegetable oil impregnated samples as compared to mineral oil ones. © 2016 IEEE.


Badicu L.V.,Polytechnic University of Bucharest | Dumitran L.M.,Polytechnic University of Bucharest | Notingher P.V.,Polytechnic University of Bucharest | Setnescu R.,University Valahia of Targoviste | And 3 more authors.
Proceedings - IEEE International Conference on Dielectric Liquids | Year: 2011

Lifetime estimation of mineral oil is based on IEC 60216-1/2001, using accelerated thermal ageing at three temperatures), method which requires a long experimental time. In order to reduce the experimental times, this paper proposes a simpler method to draw the lifetime curve by determining an experimental point (carrying out only a thermal ageing at the highest temperature - which requires the least time) and curve slope (based on the activation energy of oxidation reaction). Assuming the volume resistivity and the loss factor as diagnostic factors, their variation curves with ageing time were drawn, and the lifetime values were calculated. Using differential calorimetry measurements (DSC curves) for four heating rates, the activation energy value Wa of oxidation reactions was obtained. Knowing the Wa value and the ageing time to achieve the end of life criterion for thermal ageing at the highest temperature (155 °C), the D3 lifetime value was determined and compared with D1 and D2 values obtained by accelerated thermal method at three temperatures. Finally is showed that, the differences between D3 and D1,2 values are relatively reduced and the method based on activation energy obtained by DSC, can be used to assess the lifetime of mineral oil. © 2011 IEEE.


Ilie S.,CERN | Setnescu R.,CERN | Setnescu R.,R and D Institute for Electrical Engineering ICPE CA | Setnescu R.,University Valahia of Targoviste | And 7 more authors.
Polymer Testing | Year: 2011

This paper presents the investigation work on different polymeric materials used as insulation materials of conductors in a multicore instrumentation cable. Among differently colored materials, only the white one presented cracks after a few years of use. Isothermal and non-isothermal DSC measurements were performed on initial (non-used) and aged (in service used or laboratory aged) materials as well as on raw materials in order to characterize their stability and the ageing state after storage, use in service or laboratory ageing. As shown by the oxidation induction time values, a pronounced antioxidant loss occurred for all materials during storage or service; plus a strong effect of the ambient light on stability was observed for the white insulation material. Around 3% of filler, consisting mainly of TiO2 particles (as revealed by SEM-XRF elemental analysis), was found in the white material. The higher degradability of the white material can be related to both the photocatalytic effect of the TiO2 particles and rapid loss of stabilizers. © 2011 Elsevier Ltd. All rights reserved.

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