Impact of Corona Aging on the Electrical Performance of SiC/Epoxy Composites

Nonlinear resistive field grading materials are widely used in high-voltage power equipment. Meanwhile, corona discharge in equipment may cause the deterioration of the materials. In this paper, the electrical performance of field grading materials after corona aging is investigated. The SiC/epoxy composites are prepared as an example of nonlinear resistive field grading materials and are aged under corona discharge. The microstructures are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and contact angle. The dielectric spectra, breakdown strength, and conductivity are measured. In addition, a finite element simulation for a cone spacer model based on the aged samples is carried out to investigate the effects of corona aging on the electric field distribution and power dissipation. Experimental results reveal that, compared with unaged SiC/epoxy composite, the aged composite is larger in relative permittivity, loss tangent, surface and volume conductivity, whereas it is lower in breakdown strength, nonlinear coefficients, and switching electric field. Simulation results show that the power dissipation density highly increases as the aging time increases, which threatens the safe operation of the spacer. This work provides a reference for the development and application of nonlinear resistive field grading materials.