Effect of particulates on the dielectric properties and breakdown strength of insulation oil

The dielectric properties of dodecylbenzene cable oil containing various concentrations of silica, paper, carbon and copper particles were explored. Dielectric spectroscopy and electrical conductivity measurements revealed a critical concentration above which the dielectric properties were adversely affected by the particles. A reduction in electrical breakdown strength was observed as the particle concentration increased. Carbon was the most deleterious material with only 0.005 wt. % required to cause a catastrophic reduction in breakdown strength. The results indicate that carbonaceous particulates, which might arise from electrical discharge activity, are particularly detrimental for high voltage plant.