String Efficiency Analysis of 132-kV High Suspension Insulators Using 2D Finite Element Method Magnetics

Abstract

Suspension insulator is needed to prevent leakage current flow to earth through the support tower in high voltage transmission. However, the potential distribution and electric field across each insulator in a string is non-uniform, which causes flash over and excessive heat that shortens the lifespan of the insulators and lowers string efficiency. The potential difference at the bottom unit is inversely proportional to string efficiency. A higher string efficiency, which can be attained using capacitance grading, assures a longer lifespan of the insulator. The purpose of this paper is to study the voltage distribution and string efficiency of a 12-disc glass suspension insulator (model LXWP4-70) at 132 kV using 2D Finite Element Method Magnetics (2D FEMM) software with and without capacitance grading method. The 2D FEMM was used to determine the potential distribution as well as the static capacitance of each string insulator and to calculate the string efficiency. One of the string insulator disc dimensions was measured at the High Voltage Lab of the University Malaya. The results showed that the string efficiency has improved from 64% to 76% due to capacitance grading.