Study on Insulating Characteristics of Aged Epoxy Nano-Composite Insulation Under Lightning Impulse

This article investigates the effect of various lightning impulses on the aged epoxy insulations. To secure the reliability of insulation materials, impulse testing is very crucial at design stage. For this reason, electrical equipment is subjected to a lightning impulse voltage test with a standard waveform of [(1.2 × 50) μs] after manufacturing. However, it is to be noted that natural lightning conforms not only the standard impulse voltage waveform but also non-standard lightning voltage waveforms. Considering this fact, a standard waveform of [(1.2 x 50) μs] and five non-standard lightning impulse (NSLI) waveforms with durations of [(3 x 16) μs, (3 x 10) μs, (8 x 20) μs, (10 x 50) μs, and (7.5 x 30) μs] are generated in simulation platform. Each waveform has a peak voltage of 100 kV. Besides, pure epoxy, epoxy-alumina and epoxy-titania nanocomposite insulation samples are prepared in laboratory. These prepared insulation samples are subjected to electro-thermal aging with an interval of 100 hours for a total of 600 hours. After each aging step, polarization and depolarization currents (PDC) are measured. These PDC measurements are then used to develop an Extended Debye Model (EDM) of the insulation within a simulation platform. Therefore, the simulated impulse voltages are applied to the insulation models and corresponding impulse responses are analysed. The results indicate that impulse currents increase with aging, and epoxy-alumina nanocomposites exhibit superior dielectric properties compared to other samples.