Influence of corona intensity on the hydropobhicity recovery of polymeric insulating samples

Corona discharges from the insulator metal parts and the line hardware influence long term performance of the silicon rubber insulators used in HVAC and HVDC transmission. Polymeric insulators when installed are highly hydrophobic; they have to perform under various mechanical, electrical and environmental stresses, over a period the hydrophobic properties decrease. The present work, investigates the loss and recovery of hydrophobicity of silicon rubber insulator samples exposed to AC and DC corona. Two types of specially designed corona generating electrodes are used to simulate uniform and non-uniform corona stress on the samples. A systematic study of loss and recovery of hydrophobicity as a function of electric field intensity and type of voltage employed is conducted. The investigation shows that the effect of DC corona on hydrophobicity property is significantly low in comparison with that of AC corona. The initial rate of recovery of hydrophobicity is found to be higher and stabilized over a period of time.