Current imbalance and charge build-up on insulators in AC air coronas

By replacing an AC-corona-stressed insulator surface by a metal electrode subjected to superposed AC and DC corona, the authors studied the processes responsible for the DC charging of insulators. A main result is that the charging is critically dependent on corona processes at the high-field electrode. A corona electrode that gives positive streamers will give substantially less net charge than an electrode burning in the positive glow (Hermstein corona) mode. However, the streamers may do other damage to insulator surfaces. The balance between the synchronous and impulse current components is found to be the decisive factor in determining the charging of corona-exposed dielectric surfaces