Aging effects of conductor surface conditions on AC corona discharge

Aging effects of conductor surface conditions on AC corona discharges were investigated by means of comparing three typical aged conductors with the new ones. The aged conductors acquired from the AC power transmission lines had been used for 12, 15 and 20 years. Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDX) analysis were employed to characterize the morphologies and the compositions of the conductors respectively. As a result of many substances adhering to conductors, the surface of aged conductors became more coarse and unshaped than the new ones. AC Corona discharge characteristics of these conductors were studied in a small corona cage with an ultraviolet imaging instrument, the effects of the surface conditions on the corona discharges process were investigated, and the corona inceptions voltages could be obtained by the “tangent” method. The corona discharge intensity of the aged conductors was much stronger than the new ones; consequently, the corona inception voltages of aged conductors were 10%–25% lower than the new ones.