Reduction in AC partial discharge from PMMA films doped with an electron donor dye

AC partial discharges from PMMA films doped with various dyes have been investigated. In this paper, the following three dye films were prepared by the solution‐casting method: p‐aminoazobenzene (Ab); p‐nitrobenzeneazo‐resorcinol (Nb); and methyl‐yellow (My). AC partial discharges were investigated by placing a 100‐μm thick film on a 3‐mm thick PMMA plate between a spherical high‐voltage electrode and planar ground electrode. The number of discharge pulses and total electric charge discharged from an Ab‐doped PMMA film was less than 50 percent of those without Ab. AC partial discharges were suppressed at electric fields which were slightly higher than the electric field for the onset of ac partial discharges. However, ac partial discharge characteristics of PMMA films doped with other dyes were not affected. Attempts have been made to elucidate mechanisms for the reduction in ac partial discharges on the PMMA film doped with Ab by examining the distribution of surface potential at zero crossovers. The ionization of Ab dye, which is an electron donor, is attributed to the reduction in ac partial discharges on the Ab‐doped PMMA film.