Insulators are essential components of transmission lines

and porcelain insulators are particularly widely used.When a zero-value insulator is present in a porcelain insulator string

the risk of pollution flashover and overvoltage flashover increases significantly

posing a severe threat to the safety of the power grid.In this study

a finite-element simulation model of the electric field for 220 kV double-string porcelain insulator was established to analyze the spatial electric field distribution under both normal and degraded conditions.The feasibility of detecting zero-value defects based on spatial electric field characteristics was verified through live-line measurements.The results show that when a pronounced “drop” in the spatial electric field amplitude occurs along the insulator string

a corresponding insulator unit can be identified as zero-value or deteriorated.Therefore

by analyzing the spatial electric field distribution

zero-value detection of 220 kV double-string porcelain insulators can be effectively achieved.