Electrical characterization of low-density solid insulating fillers for hollow-core composite insulators

Insulating materials that can fill the internal space of hollow-core composite insulators (HCIs) are gaining relevance due to the new areas of applications of these insulators. Such materials must be light and have sufficient electrical properties to preserve the integrity of the inner room of the HCIs. The electrical properties of a light polymeric foam, known as dry syntactic foam (DSF), which is based on two types of hollow microspheres (HMSs), were investigated. Special emphasis is placed on the influence of the density of the resulting material regarding the electrical properties. The results show that the dissipation factor and the relative permittivity have a proportional relationship with the density. Furthermore, two main properties, namely the number of interfaces and the pore size are found to influence the breakdown strength of the DSF.