ABSTRACT
Partial discharges are a special type of electrical discharges according to IEC 60 270, in which there is a partial violation of part of the dielectric insulation. With these discharges, the remaining part of the dielectric still has sufficient electrical strength to allow further trouble-free condition of the electrical machines. Gas cores are located in the insulating material itself or just below the electrode during the so-called delamination (separation of layers) of individual materials with each other. Delamination occurs either during the production of insulation or during operation under the action of high temperature and pressure on individual layers of insulation. Anorganic Insulating materials, e.g., porcelain, mica, and glass, have very good resistance to partial discharges. High temperature resistance also characterizes these materials. Their disadvantage is that they are fragile and therefore cannot be directly used in the insulation systems of HV electric machines.
