PD behaviour and surface charging of a particle contaminated spacer in SF6-gas insulated switchgear

The electrical properties of the widely used gas insulated systems for switchgear and their depend strongly on the surrounding field conditions. A simplified spacer model with an adhering particle was tested under homogenous field conditions in SF₆. The gas pressure and the particle length were used as parameters. Investigations on the electrical strength and the PD behaviour were performed under clean and particle contaminated conditions. The surface charge accumulated during AC and LI stress and its distribution was measured during the experiment. A specially designed setup was used to acquire the surface charge data; stressing the sample and subsequent measurements of the charge distribution could be performed without distortion of the latter. This enabled the application of voltage stress to a well known “charge distribution and particle configuration”. Thus the effects of surface conditioning and decreasing or increasing insulation strength could be studied. PD activity was measured under AC conditions using the Phase Resolved Partial Discharge method. Fingerprints from particles on spacers were taken and the possibility of using the PD measurement as a diagnosis tool were evaluated. Special attention was paid to the PD level readings concerning different setups and usability for on-site tests