Analysis of Arcing Horn on Disk Insulator Configuration in 150 kV SUTT at PT PLN (Persero) Unit Induk Pembangunan Sumatera Bagian Tengah

Abstract

The reliability of the electric power transmission system on 150 kV High Voltage Overhead Transmission Lines (SUTT) is strongly influenced by insulation coordination, particularly in the disk insulator string and arcing horn assembly, which functions to divert electrical flashover caused by overvoltage so that the insulator is not damaged. Under the existing condition, it was found that the installed arcing horn was designed for a 12-disk insulator configuration, while the actual string used only 10 disk insulators, thereby changing the distance between the arcing horns and affecting its breakdown voltage. This study aims to analyze the effect of changes in disk insulator configuration on the arcing horn breakdown voltage and to evaluate the potential risk of insulation unreliability resulting from this mismatch. The research method involves technical data collection of the insulator string and arcing horn configuration, calculation of Critical Flashover Voltage (CFO) using the rod-plane gap method based on CIGRE recommendations, visualized through COMSOL Multiphysics 5.5 simulation. The results show that the 12-disk insulator configuration has an arcing horn distance of 1.352 m with a breakdown voltage of 709.8 kV (positive) and 1209.219 kV (negative), while the 10-disk insulator configuration has a distance of 1.060 m with a breakdown voltage of 556.5 kV (positive) and 995.333 kV (negative). Nevertheless, both configurations still satisfy the insulation coordination principle because the arcing horn breakdown voltage remains lower than the insulator breakdown voltage, with an insulation margin to BIL of 108% (12 disks) and 73.3% (10 disks). The smaller the gap distance, the higher the potential for flashover and the risk of system unreliability, so adjustment of the arcing horn distance is still recommended.