工频电压下聚乙烯表面动态电荷分布的研究

Polymeric materials are widely used for electrical insulation and mechanical support in electrical apparatus. Under the high voltage electric field，the large number of charges accumulated on the polymeric surface tend to cause local electric field distortion and surface flashover，considerably threatening the safety of equipment. In this paper，a reflective-type surface dynamic charge measurement platform based on Pockels effect is set up to observe the evolution of two-dimensional surface charge distribution on polyethylene under unipolar voltage，single cycle power frequency voltage and multi-cycle power frequency voltage. The results indicate that the measurement method based on Pockels effect can observe the charge accumulation，diffusion and dissipation processes within 0.5 s，which cannot be obtained by the traditional electrostatic probe method. Under the positive and negative polarity voltage，only the charge of the corresponding polarity is deposited on the polyethylene surface. The duration of the charge accumulation，diffusion，and dissipation process is about 0.5 s，and 70%~85% of the total accumulated charge is dissipated from the surface within 0.4 s. By comparing the evolution of the surface charge under sinusoidal AC voltage with different polarity inception，it is found that the coexistence of positive and negative charges occurs only for positive polarity inception. The dynamic behavior under 10 consecutive power frequency cycles reveals that it takes at least 3~4 cycles for surface charge accumulation to evolve into a stable state，with the gradual shrinking charging regions during this period. The research results have important reference value for intuitive understanding the evolution process of polymer charge accumulation under AC voltage.