Dielectric properties and equivalent circuit of a high resistivity particulate layer

Abstract

The capacitance and conductance of a compacted layer of high resistivity fly ash particles are measured over the frequency range, 1.0 Hz to 50 kHz. A simplified equivalent circuit, which models the dielectric properties of the layer over this range of frequencies, is developed from the microscopic electric field pattern of an idealized particulate layer. At low frequencies, the effective capacitance is approximately six times greater than the high frequency value and mainly comprises the interparticle air gap capacitance. At higher frequencies, the effective capacitance is constant and its magnitude is determined by the geometry of the particles and voids, and the relative dielectric constant of the particle material. The effective conductance of the layer increases with frequency, and in the high frequency range it is dominated by the dielectric losses. The overall response at the lower frequencies is influenced significantly by the layer's particle surface conductance.