An Optimal Design of Grounding System for Tower Footings in Payakumbuh 150 kV Transmission Line of Koto Panjang

The 150 kV Koto Panjang – Payakumbuh transmission line has a line length of 86 km with 249 towers, and the occurrence of the back-flashover in their transmission line is 74%, indicated by the high tower footing resistance as that is >3 ohms. The type of rock on the transmission line and the location of the towers, 79% in hilly or mountainous terrains, are among the factors that can cause an increase in the resistance value. The results of this study indicate that the level of back-flashover affects the value of the tower footing resistance by considering the number of electrode installations. When the towers were installed with more electrodes, the value of tower footing resistance, back-flashover level, and insulator voltage could be reduced to less than half of the previous ones. Moreover, the occurrence of the back-flashover rate in each tower can be dropped to ≤ 1 back-flashover rate of 100-km/year. Each tower's soil resistivity value has grown, yet fewer back-flashover disruptions exist. The span's length causes this, as the shorter the span, the faster the reflected wave will travel. As a result, it can lower the voltage in the insulator and diminish the likelihood that a flashover would occur