Space charge measurements, dielectric spectroscopy and breakdown tests on new and aged polycarbonate [HVDC insulating materials]

Electrically stressed materials can be characterized as electrically aged only if we have evidence that the material changes due to the electrical stress are responsible for material failure, which is not always the case. Often, a large number of breakdown tests is needed to prove that a set of specimens is electrically aged. As an alternative, we can however also combine a smaller number of breakdown tests with some other method for material characterization. The latter approach was followed when studying polycarbonate with TiO₂ filler, both new specimens and specimens that had been stressed for 860 hours at a DC voltage. Space charge measurements, dielectric spectroscopy tests in the frequency domain and breakdown tests were performed to check whether these methods provide us the same answer concerning the aging of PCTiO₂.