Conductive tape influence on composite dielectric spectra

Partial discharges suppression in slot part of rotating machines is an issue to be solved using the different attempts. Since decades the conductive layers of main wall slot insulation are used. Besides their resistivity / conductivity which allows proper contact with stator core and partial discharges / vibrational sparking reduction, their dielectric properties shouldn’t affect the losses in stator insulation. Thus, the dielectric properties of composites used as main wall insulation of rotating machines are presented and discussed. The comparison of final dielectric properties of a composite concerning three different types of conductive tapes are presented. One type of epoxy resin was used as matrix and influence of conductive tapes based on a) PET-non-woven with additional polyester threads, b) polyester / glass fibres and c) electrically conducting glass fabric on whole composite dielectric spectra were investigated. The methodology of investigation is based on broadband dielectric measurement in frequency spectra. The test results show significant differences of composite dielectric behaviour dependent on tape type used as filler.