Investigations on charge trapping and de de-trapping trapping properties of polymeric insulators through discharge current measurements
Abstract: It is generally accepted that formation and accumulation of space charge in polymeric insulation is a critical issue in the design of high voltage electric systems, as it leads to insulation degradation and premature failure under high voltage surges and polarity olarity reversals. Even at service stress level, accumulation of space charge may cause electrothermal aging. The insulation degradation and aging is reflected in the trapping and detrapping characteristics of the insulation, making it a useful aging marke marker. r. Space charge measurement methods are frequently used for trapping and de de-trapping trapping analysis. However, estimation of charge trapping and de-trapping trapping behavior is very difficult due to the involvement of material properties and also partly due to the fact tthat hat proper measurement of space charge is itself a very complicated issue, requiring very sophisticated experimental arrangement and signal processing techniques. Moreover, application of these methods is limited to polymeric insulations of certain geometries ies (planar or radial). In this paper, the charge trapping and de-trapping de behavior of low density polyethylene (LDPE), a widely used polymeric material for electrical insulation purpose, have been investigated employing a direct method based on the discharge rge characteristics obtained after the sample was stressed for short durations. A relationship is established between the de de-trapped trapped charge and the extracted charge measured from the discharge current. From this relationship