The investigation and relationship between space charges and pre-breakdown of solid dielectrics

The electroacoustic pulse method is used to measure the space-charge distribution in solid dielectrics in which the stress waves of interfacial and volume charges overlap. To reduce measurement errors, a polyvinylidene fluoride piezoelectric transducer of wider frequency bandwidth (0.5-10 MHz) is used instead of a lead zirconate-titanate transducer. The processes of injection and accumulation of space charge in low-density polyethylene samples are observed, and the charge distribution and the electric field distribution under high DC electric fields are measured. Experimental results show that space charges play an important role in the breakdown of solid dielectrics