SURFACE FLASHOVER CHARACTERISTIC OF DISC-TYPE SPACER SYSTEM INITIATEDBY WEDGE-SHAPED GAS GAP AND ITS IMPROVEMENT

The surface flashover characteristics initiated by the local field int ensification have been investigated for lightning impulse, switching i mpulse 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 ev aluated by the simple theory in SF6 gas and compared with the experime ntal results. The practical methods by the thin dielectric coating of a low permittivity material on the sheath ends and by the shielding sh eath ends protruded inwardly are effective in improving the dielectric performance of the system.