Cumulative Damage Effect of the Pin-Type Porcelain Insulator Incipient Fault in Resonant Grounded Distribution Networks

Cracked porcelain insulators will experience discharges with self-clearing characteristics due to the influence of rainwater, called porcelain insulator incipient fault (PIIF). Frequent occurrences of the PIIF can cause irreversible cumulative damage to the cracked porcelain insulator, eventually leading to a permanent grounding fault. The cumulative damage effects on the porcelain walls caused by PIIF with different numbers of occurrences and different discharge energies were investigated in this article via theoretical analysis and physical experiments. The results indicate that when the discharge energy of PIIF is generally below 15 J, the cumulative rate of damage to the porcelain walls is so slow that it can be almost ignored. When the discharge energy is mainly distributed in the range of 15–35 J, the surfaces of the porcelain walls will develop concave discharge traces, and the depth and width of these traces increase with increasing occurrence number and discharge energy of the PIIF. When PIIF with discharge energy exceeding 35 J occurs several times, a permanent grounding fault will occur soon.