EPRI-HVDC INSULATOR STUDIES - 3. THEORIES ON FLASHOVER PROCESSES.

Two intersting phenomena discovered during laboratory flashover simulation experiments are described and theories are presented to explain their occurrences. The first is the formation of a clean zone, in addition to the well-known dry zone, during scintillation stages before a flashover. It was determined that electrostatic forces are responsible for its formation. The second observation was the deleterious effects inflicted by nitrates on suspension insulators, particularly those made of glass. Surface degradations were documented and these were attributed to electrochemical reactions during electrical discharges. Such a finding raises the question of the integrity of an insulator in a nitrate-prone region.