Influence of aged conductor surface conditions on AC corona-generated audible noise with a corona cage

Relatively few investigations have previously been made on the effects of surface conditions on corona-generated audible noise for the long-term aged ac conductors. In the present work these were investigated by means of comparing audible noise on typical aged conductors with that on new ones. The aged conductors from the ac power transmission lines had been in service for 12, 15 and 20 years, and their surface morphology, composition and roughness had been analyzed in our previous paper. A microphone and sound level meter was employed to measure the audible noise of the aged conductors in a small corona cage. As a result of the much intense corona discharge on the surfaces of the aged conductors, the audible noise of the aged conductors was much higher than the new conductors in dry condition. In wet condition, the corona discharge was found to be become more serious than the conductor in dry condition; hence, the audible noise was about 3 to 5dB stronger than that in dry condition.