Surface flashover characteristic of disc-type spacer system initiated by wedge shaped gas gap and its improvement

The surface flashover characteristics initiated by the local field intensification have been investigated for lightning impulse, switching impulse and ac voltages, using disc-type model spacer systems with the wedge shaped gas gap formed between the spacer flange and the earthed sheath end. The surface flashover voltages of the systems have been evaluated by the simple theory in SF(sub 6) gas and compared with the experimental results. The practical methods by the thin dielectric coating of a low permittivity material on the sheath ends and by the shielding sheath ends protruded inwardly are effective in improving the dielectric performance of the system.