On the Partial Discharge Behavior of a Low-Density Polymeric Foam for Hollow-Core Composite Insulators

Increasing attention is being paid in the recent years to low-density foams to enable new applications in the field of hollow-core composite insulators (HCIs). These fillers must feature a sufficient dielectric strength to adequately insulate the inner room of the HCIs. Under AC stress, the dielectric breakdown in foams is driven by a partial discharge (PD) process. The PD activity of a novel low-density polymeric foam was investigated for several densities comprising different pore structures. The results show that the compositions with very low densities display generally a lower breakdown strength, the biggest pores being the most determining factor. Moreover, the inception strength for PDs does not depend linearly on the density and is closely related to the smaller-size pores.