Thermal endurance of electrical insulating materials studied by the use of the kalman filter


  • M. Cacciari,

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    • Dr.-Ing. Mario Cacciari (1938) received his M. Sc. and Ph. D. in Eiectrical Engineering from the University of Bologna/Italy in 1965 and 1988, respectively. In 1992 he has become Professor of Electrical Technology at the University of Trieste Ataly. His research interests include reliability inference of solid insulating materials and power system harmonics (Dipartimento di Ingegneria dell' Informazione. Universita di Parrna, Male delle Scienze 1, 1-43100 Parma, Italy, T +39521/9O5833, Fax +395 21/905822)

  • G. C. Montanari,

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    • Dr.-Ing. Gian Car10 Montanari (1955) received his Dr.-Ing. degree in Electrical Engineering from the University of Bologndtaly in 1979. In 1983 he joined the University of Bologna as a researcher and has become Professor of Electrical Technology in 1987. He has worked since 1979 in the field of aging and endurance of solid insulating materials and systems at the Institute of Industrial Electrotechnics of Bologna University, where he is responsible for the high-voltage plant. He is also engaged in the topics of harmonic compensation in electrical power systems, power electronics and statistics. He is IEEE Senior member and member of IEC 15E and IEC TC 33. He is Ad Com member of IEEE DEIS (Dipartimento di Ingegneria Elettrica, Universitg di Bologna, Viale Risorgimento2, I-40136Bologna, Italy, T+3951/6443481, Fax + 395116443470)

  • C. P. Barry

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    • Dr. Cyril P. Barry (1929) has been working in electrical insulation industry for almost 40 years. After research at University (carbohydrate chemistry) and army service (clinical biochemistry) he joined the capacitor industry in 1955. Having been involved in most technical activities there, he moved to the manufacture of electrical insulating paper, where he was also concerned with the production of plastic films for capacitors. An important aspect of this work was the application of statistics to quality control and development of Standards for all electrical insulation. This field is now his main occupation, as an independent Consultant (1 Old Ffordd-Fawr, Llanigon, Hay on Wye, Hereford HR3 5PR, England, T +441497/820129)


In this paper the Kalman-Filter algorithm is applied to the Arrhenius life model, normally used for thermal endurance characterization of insulating materials. It is shown how this algorithm can be used to derive estimates of Temperature Index and Halving Intervals, i. e. the indices recommended by IEC216, using thermal endurance data relevant to three insulating materials or systems. Depending on scattering of the experimental points from the assumed linear model, especially of the points at the lowest temperatures, estimates performed by Kalman filter and according to IEC216 may considerably differ. Tests of the validity of the model, which are available in the Kalman procedure, show that there is a high probability that the linear model is not valid at the lowest test temperatures.