Experimental research on the evolution of creepage discharge in aged pressboard

Experiments were carried out to study the evolution of creepage discharge for various aged pressboards under ac constant voltages. White mark, impulsive current, UHF signal, acoustic signal and dissolved gases were measured. The results show that creepage discharge in aged pressboard tends to creep more quickly and easily than in unaged pressboard; average number of discharge experienced a rapid growth process in early stage to a slightly descent stage both for aged and unaged pressboard and average number of unaged pressboard was larger than unaged pressboard; there are not remarkable differences between aged and unaged pressboard in acoustic signals and DGA.