New VPI Insulation System of High Voltage Stator Windings of Large Rotating Electrical Machines Based on Cogemica VPI Tapes and One-component Epoxy Impregnation Varnish

Cogebi, member of ELCIM Group, is a traditional producer of mica insulation materials. The presented work introduces a new VPI isolation system of the HV winding of large rotating electrical machines based on medium-viscosity one-component epoxy impregnation varnish with high reactivity and Cogemica glass backed VPI tape 609R containing no accelerator. Due to its technological properties and final dielectric parameters, this insulation system aspires to be an alternative to insulation systems based on epoxy-anhydride VPI varnishes and porous mica tapes with an accelerator. Although existing insulation systems of large HV windings are very good in all technical and technological aspects, the legislative regulations (REACH registration requirement) limit the use of some key components of the systems in the future.