Analysis of the effect of phase wire position upper, middle, and lower against distraction back flashover at transmission line 150 kV Koto Panjang - Payakumbuh

The Transmission line system 150 kV Koto Panjang - Payakumbuh in West Sumatra with a channel length of 86 km and IKL 173 days/year, has 248 towers, accounting for 13 times of back flashover interference with a tower foot resistance value above 5 ohms from 2010-2019 which makes the system trip out due to lightning disturbances and affects every phase wire position. The percentage of distractions due to back flashover preposition by two methods is for the Anderson upper method 29.04%, middle 20.98%, lower 25.323%, and BFO 57.5, after improvement down to upper 3.23%, middle 3.069%, lower 2.90%, and BFO 3.9. While in the Hileman upper method 20,855, middle 14.42%, lower 16.70%, and BFO 41. 55, then after improvement it dropped to upper 1.41%, middle 1.27%, lower 1.10% with BFO 3.2. By using the Anderson Method and Hileman Method calculations as well as simulations using EMTP, namely, the upper position will be dominant when the ground resistance rating (1-5 Ω) and tower height is above 30 m, the middle position will be dominant when the ground resistance rating is (5-35 Ω ) and the hgwp distance on the tower is large, while the lower position will be dominant if the grounding resistance rating is at (≥35 - infinity) and has a smaller hgwp distance value.