Dielectric spectroscopy of thermally aged insulation

There is difficult to imagine modern manufacturing of electrical devices without components containing (mainly for technological reasons) organic substances. This fact is mainly concerned to composite materials, in which the bond component is made of organic substance. Most of the electro-insulating materials used in common applications are composite materials. The possibility of the determination of dielectric properties of these systems is a problem of theoretical as well as practical importance. The paper is focused on thermal aging and accompanied dielectric spectroscopy diagnostics of two mainly used materials, which are utilized as a part of insulation system of electrical devices. The first tested specimen was mica composite material based on glass fibre and epoxy resin and the second one was two component composite based on epoxy resin as well. The specimens were tested under laboratory conditions. The materials were thermally aged and the changes of its physical and chemical properties were measured and evaluated. For accelerating the aging process different temperature values (170-200°C) were chosen. The aging time was determined for each temperature value. Specimens of tested material were performed and cured as flat plate 100×100 mm. The measuring of these specimens was carrying out in frequency domain from 200 Hz to 2MHz at special electrode test setup. For comparing the aging process of the investigated material the trends of measured parameters were studied and described in dependence on exposure time, temperature and applied frequency during measurement.