Electric field computation of composite line insulators up to 1200 kV AC

TLDR

Composite insulator performance depends on surface electric field distribution. The study calculates electric field distribution for composite insulators up to 1200 kV using a 3‑D Boundary Element Method software. The analysis examined how corona rings, grading rings, conductor configurations, insulator orientation, unit type, and surface condition affect electric field distribution. Dual insulators with individual corona rings at line and ground ends and a common grading ring at the line end reduce stress in UHV systems, with optimal corona and grading dimensions illustrated for a 1000 kV string, and dead‑end insulators experiencing higher stress than suspension ones, especially at higher voltages.

Abstract

Satisfactory operation of composite insulators is intimately related to the surface electric field (stress) distribution. This paper presents results of calculation of the electric field distribution for composite insulators up to 1200 kV, using a 3D software package based on the Boundary Element Method. The impact of corona and grading rings, single and bundled conductors, insulator orientation (dead-end and suspension), single and double units, and surface condition (dry and wet) on the electric field distribution has been analyzed. For UHV systems (higher than 750 kV ac) the use of dual insulators with individual corona rings at the line and ground end and a common grading ring at the line end is beneficial. The existence of optimal dimensions of corona and grading arrangement has been illustrated on a 1000 kV insulator string. It was found that the dead end insulators experience higher electric stress when compared to their suspension counterparts and this difference gets more prominent as the system voltage increases.