Sensing the Electrothermal Aging Status of Epoxy Nanocomposites by Standard and Nonstandard Lightning Impulse Parameters

This study proposes an advanced method for sensing the aging state of epoxy nanocomposite insulation. For this purpose, five types of epoxy nano-composites (EPNC) samples (i.e. pure epoxy, epoxy with alumina or titania having concentration of 1wt% or 2wt%) have been prepared in the laboratory. The prepared test samples were undergone through accelerated electro-thermal aging (at 6 kV, 50-Hz and 100°C temperature) for 600 hours. After every 100 hours of aging duration, different lightning impulse voltage (both standard and non-standard) were applied on those test samples and corresponding impulse response current were recorded using the developed experimental arrangement. From the recorded signal, three aging-sensitive parameters are identified i.e. tail-time (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_t</i>), peak impulse current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_P</i>), and area under the curve (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i>). Thereafter, those three parameters are correlated with the aging state of the insulation through three novel empirical relations. Finally, the effectiveness of the proposed empirical relationships is validated using a separate set of laboratory-prepared EPNC insulations having known aging state. The analysis of the validation results shows that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_t</i>, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_P</i>, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> can sense the aging state of EPNC with maximum errors of 2.55%, 4.03%, and 3.60%, respectively. It is yet to be mentioned here that; this advanced methodology for assessing insulation aging state that is less susceptible to noise interference and consume less measurement time. Hence, this method leverages the analysis of three newly identified aging-sensitive parameters extracted from current responses under impulse voltage testing for establishing the empirical relations with aging.