Fundamental Investigation on Influence of Mechanical Oscillation on Particle Levitation under DC Electric Field Strength in SF₆ Gas

Abstract

The newest GIS is being reduced in size due to advances in arrester performance and reduction of impulse test voltage for specifications. Field strength of the inner surface for the GIS tank is being strengthened more than ever; for this, it is necessary that the design work consider particles included in the GIS. When GCB and DS are opened, residual DC voltage occurs at the conductor between the GCB and DS. Movement of particles under DC voltage is known to differ from that under AC voltage. It is very important to know particle movement under DC voltage, even if the GIS is for AC use. Therefore, this paper deals with particle-levitation under DC voltage in SF₆ gas. Effects of polarity and vibration were confirmed for levitation of a particle on an insulated coating electrode. An aluminum particle (φ0.25×L3) on a sheath of 0.5MV/m did not levitate until a 6.5G oscillation acceleration was reached under a single-polarity DC voltage. On the other hand, the particle levitated at about a 2G oscillation acceleration under a reversed polarity DC voltage. Moreover, oscillation acceleration of initial levitation for a large size GIS model was almost equal with that of fundamental experiments.