Abstract :
The electric strength of air, in millimeter gaps, decreases at frequencies exceeding 100 kHz, but the effect on the discharge inception voltage Vi in solid insulation is too small to explain the reduction in the short-time breakdown voltage Vst of solids at radio frequencies. When breakdown is caused by internal discharges or by surface discharges in air, V st at 50 Hz is usually between 5 Vi, and 20 Vi, so the reduction in Vst when the frequency is raised may be explained by the increased discharge repetition frequency causing more rapid degradation with a risk of cumulative heating at lower stresses. When tests are made in oil, Vst/Vi is smaller than in air, so in this case a tenfold reduction in Vst at higher frequencies may be caused by a reduction in the electric strength of the oil
Keywords :
electric breakdown of solids; electric strength; organic insulating materials; polymers; RF frequencies; air gaps; breakdown voltage reduction; cumulative heating; discharge inception voltage; discharge repetition frequency; electric strength; frequency effect; internal discharges; oil; polymers; radio frequencies; rapid degradation; short-time breakdown voltage; solid insulation; surface discharges; Breakdown voltage; Degradation; Dielectrics and electrical insulation; Electric breakdown; Heating; Petroleum; Polymers; Radio frequency; Solids; Surface discharges;
