Surface Charges Accumulation Characteristics of Epoxy/Glass Fiber Composites under DC Superimposed Harmonic Voltage

Epoxy/glass fiber composites are widely used in the packaging insulation of dry-type air-core reactors. However, charges accumulate on the surface of smoothing reactor are caused by DC superimposed harmonic voltage, which is potential to trigger surface discharge and threaten the safe operation of the reactor. In order to explore the effect of DC superimposed harmonic voltage on the surface charge accumulation characteristics of epoxy/glass fiber composites, the amplitude DC superimposed harmonic voltage and charging time are saturated at 8 kV and 3 min, surface charges distribution of the composite which is charging by the voltage with different harmonic frequencies and DC ratio are measured by the Trek 541 A. The results show that with the increase of harmonic frequency, more electrons are generated near the needle electrode, and space charges accumulate on the surface of the material perpendicular to the needle electrode; With the increase of DC ratio in DC superimposed harmonic voltage, the amount of accumulated charges also increase. When the ratio of D C voltage to harmonic voltage reaches 4: 1, the charge behavior is consistent with the charge accumulation form of only DC component. The study of charge accumulation under DC superimposed harmonic voltage provide guidance for the subsequent study of the inducing mechanism of charge accumulation on surface discharge in smoothing reactor.