Dielectric response measurements at high voltage bushings

High voltage bushings are the link to connect outer and inner insulating systems. The high voltage is fed into the vessel of the transformer and has to withstand high loads, as electric field strength, mechanical forces, thermal pollution and contaminations due to environmental and chemical loads. For this reason the workability of the bushings plays an important role in the error free operation of high voltage equipment. In this paper the condition of high voltage bushings was investigated by the means of the dielectric response analysis. In the foreground the Frequency Domain Spectroscopy (FDS) was applied to determine the condition and to observe the thermal behavior of different types of bushings. Several test objects of Resin Impregnated Paper (RIP) and Resin Bonded Paper (RBP) Bushings were thermal cycled. The measurement results were analyzed and shown as Dissipation Factor (tan delta) plots in dependence of test frequency.