Study on the Mechanism and Electrical Characterization of the Distribution Porcelain Insulator Incipient Fault in the Non-Effectively Grounded System

The porcelain insulator incipient fault (PIIF) is a self-clearing discharge process caused by water entering the crack of the porcelain insulator. It will not result in a tripping operation but may evolve into a permanent grounding fault after multiple occurrences, leading to various types of accidents, such as wire breaks, power outages, fires, and personal electric shocks. This paper uncovered the mechanisms behind the initiation and evolution of the PIIF. Unique characteristics of the PIIF are analyzed from aspects such as the starting time, the power-resistance variation trend, and the fault duration. The characteristics were verified and supplemented by field experiments, and the influence of the insulator models, neutral grounding modes, and the number of discharges on these characteristics was analyzed. The results lay the foundation for the identification and pre-warning of PIIF.